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SpaceX Vehicles and Missions => SpaceX Starship Program => Topic started by: john smith 19 on 03/11/2016 11:44 pm

Title: Power options for a Mars settlement
Post by: john smith 19 on 03/11/2016 11:44 pm
A search of Mars & power did not find an existing thread on this topic, yet it seems quite important.

Any settlement is going to need a substantial power source to run it's ECLSS, ISRU and mfg facilities to expand the settlement.

Lots of people have talked about PV and nuclear options. The actual current SoA for large arrays (from a powerpoint from Jess Sponable on the Evolved DC-X thread) is actually about 7W/Kg. He was working (at DARPA) on blankets pushing 300W/Kg.

The MIT work suggests 6000Kw/Kg thin films are possible, but probably won't survive launch and/or landing.

On the nuclear side the last US nuclear reactor, the SNAP 10a was in 1965 and produced 500W from 30Kw thermal. Upgraded thermo electric modules could bring it to maybe 4Kw. Moving to Stirling engines (demonstrated in the DUFF programme) would give about 8.2Kw, but the reactor design will not meet modern safety rules.

The follow on to DUFF ("KRUSTI") is aiming at a space rated no maintenance reactor in the 1Kw+ range. The largest space power reactors have been Russian designs in the 10Kw range. 

This suggests PV is likely but there is a problem which people don't seem to think about. Mars dust storms can last for weeks, implying the need for huge amounts of battery storage or evacuation back to orbit.

This suggests a 2nd power mode is needed. The obvious one is to use the storm itself with wind turbines. On the upside turbines could be much larger in 1/3 g but the air density is roughly 1/80 that of Earth at sea level, giving radically lower power output per m^2 of swept turbine area.

The key issue with this pair of systems would be a "valley of death" of too much dust to clear off the cells but not enough to spin the turbines.

One idea I've not heard mentioned is using the temperature difference between the air (running +20c/-140c) to the soil, however I'm not sure what the Mars subsurface stable temperature is. On Earth the a number of dried up oil wells generate power by injecting low BP into one well and ducting the outflow from another well into a turbine.

Such systems can generate power in the 100s of Kw range, provided you can find some way to condense the fluid back to the cycle.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 03/12/2016 12:27 am
We've only discussed this a million bajillion times. Here's one of the latest threads: http://forum.nasaspaceflight.com/index.php?topic=34836.0

Here's another, slightly more general thread that nonetheless immediately began with the power question:
https://forum.nasaspaceflight.com/index.php?topic=34667.msg1195066#msg1195066
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 03/21/2016 01:59 pm
Thanks for that.

So roughly speaking you're looking for each 100 new people to add between 500KW and 6MW to the power budget.

Just to be clear that's a minimum of 2.5x the size of the ISS PV array and about 1000x the largest reactor the US has ever flown in space, and 100x the biggest the USSR ever flew.

Reactor wise that's on the scale of the units the US Army used to power an Arctic base, per 100 settlers. The units of the NS Otto Hahn (38MW) and NS Savanah (74MW) are starting to look like quite a good size.
Landing such a unit on Mars may be difficult.

I'll also note that played out oil wells on Earth can harvest 500Kw by injecting fluid down one, collecting up the other and running it through a low BP heat exchanger. 
Title: Re: Power options for a Mars settlement
Post by: Vultur on 03/28/2016 11:09 pm
This suggests PV is likely but there is a problem which people don't seem to think about. Mars dust storms can last for weeks, implying the need for huge amounts of battery storage or evacuation back to orbit.

As Robotbeat said, this has been discussed before, but dust storms don't mean zero sunlight (the solar-powered MERs survived at least one large storm).

If one has sufficiently thin-film cells (low mass per area), just having enough area to provide the needed power at 5%-10% sunlight might be the way to go.

EDIT: fixed quote tag
Title: Re: Power options for a Mars settlement
Post by: JasonAW3 on 03/29/2016 04:47 pm
One would think that you could use some of the waste heat to supplement the heat needed for the colony as a whole.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 03/29/2016 10:29 pm
and another idea I raised:
http://forum.nasaspaceflight.com/index.php?topic=39583.msg1491714#msg1491714
....especially valid if SEP tugs are used to get the cargos to Mars orbit.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 03/30/2016 12:06 am
As Robotbeat said, this has been discussed before, but dust storms don't mean zero sunlight (the solar-powered MERs survived at least one large storm).
Survived, as in "not destroyed."

I don't think that's going to be enough for a settlement to wait out such a storm.
Quote
If one has sufficiently thin-film cells (low mass per area), just having enough area to provide the needed power at 5%-10% sunlight might be the way to go.

EDIT: fixed quote tag

So you're starting at between 493W and 590W according to Colorado U. in 2016 world record (1st solar CdTe) was 22.1%, giving about 108-130W/m^2

A minimal power level is 500Kw/100 people is 4630 m^2 worst case. So 10x that is 46300 m^2, a square about 216m on a side, per 100 people. At 60Kw/person it's 12x those numbers.

TBF it looks like dust does a lot of scattierng but little absorbing and a figure of 50w/m^2 in a dust storm may be reasonable.

So you'd have to double the minimal size (but at 60Kw/ person that's. 12x bigger)

Assuming 60Kw and 50w/m^ minimum even during a major dust storm that's a square of 22.1% efficient thin film about 334m on a side for each batch of 100 settlers. I do think the "waste" heat from such an array would be quite a useful raw materail for various processes, but it's not clear if that's worth the mass penalty.
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 03/30/2016 12:24 am
As Robotbeat said, this has been discussed before, but dust storms don't mean zero sunlight (the solar-powered MERs survived at least one large storm).

If one has sufficiently thin-film cells (low mass per area), just having enough area to provide the needed power at 5%-10% sunlight might be the way to go.

Presumably the settlement will include ISRU propellant production capability (methane + LOX or whatever); you could burn surplus propellant for electric power and heat during dust storms.
Title: Re: Power options for a Mars settlement
Post by: QuantumG on 03/30/2016 12:31 am
Presumably the settlement will include ISRU propellant production capability (methane + LOX or whatever); you could burn surplus propellant for electric power and heat during dust storms.

That reminds me. I often see the argument made that a point failure of a life support system will destroy a colony. The pretty good retort is typically eye rolling and the single word "redundancy". I think there's a little more to be said though: long term storage of LOX in underground tanks shouldn't require refrigeration if done at the appropriate pressure. As such, a surplus can be cheaply built up. So even if your entire oxygen production system went down and you had to wait for a part from Earth before you could get it up again - a worst case scenario - your colony should be able to keep breathing. I imagine there's other problems that would have similar solutions.

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 03/30/2016 01:07 am
More than that. A cubic meter of air at sea level pressure has about 70 grams of oxygen that could be consumed from it before the oxygen level will cause significant hypoxia without exertion, and can withstand about 70 grams of additional CO2 before significant hypercapnia occurs. You inhale about a 1 kg of oxygen per day (some of which is metabolized into water) and exhale about 1kg of CO2. So if the settlement has about 100m^3 per settler (including all pressurized areas), then the settlement could be without ECLSS for a whole week before major problems occur (although you'd want fans to keep the air from going stale, or perhaps people would move to places where the air is not stale).

I think 100m^3 pressurized volume per person is on the low side for a permanent settlement. ISS has about 150m^3 of pressurized volume per crew. But it does show that while you DO need to get ECLSS working eventually, ECLSS doesn't technically need to be working every single day. ;)

tl;dr: If you have 100m^3 of air per person, you can be without ECLSS for about a week before major health problems.
Title: Re: Power options for a Mars settlement
Post by: Impaler on 03/30/2016 06:54 am
Indeed, I am always annoyed as hell at Sci-fi in which they say they only have a few hours or air left while standing in a ROOM on their space ship which has enough air in it to last DAYS.  This trope is comes from a lot of old 'hard' writing (Heinlein mainly who loved to show off his disdain for sentimentality by putting someone out the airlock in this situation) but it got really cemented in the general public's mind with Apollo 13 and the whole CO2 scrubber/hack.  People don't realize that the LEM is the size of a phone booth and it still took hours for the air to get even remotely bad with 3 people in it. 

In any kind of long term habitation without evacuation ability it's not the prompt failures or emergencies which get you, it's the slow chronic breakdowns of equipment, festering health, declining morale, and teamwork being supplanted with animosity and isolation that dooms you.  Generally a terrible response to some minor issue either internal or external compounds it and turns it into a catastrophe.  The equivalent of a 90 year old falling and breaking a hip.
Title: Re: Power options for a Mars settlement
Post by: FinalFrontier on 03/31/2016 08:48 am
My favorite word one word solution:
Thorium.
FLIBE or NAbe thorium generation plant. Could produce immense amount of power and potentially use ISRU from martian soil to make new thorium for the plant. Tons of potential power production capability because of the extremely high thermal spectrum regime of a thorium reactor (due to liquid blanket reactor physics and operating regimes). Also smaller and lighter weight than traditional reactors, much smaller in fact according to some recent designs such as THORcon.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 03/31/2016 09:31 am
My favorite word one word solution:
Thorium.
FLIBE or NAbe thorium generation plant. Could produce immense amount of power and potentially use ISRU from martian soil to make new thorium for the plant. Tons of potential power production capability because of the extremely high thermal spectrum regime of a thorium reactor (due to liquid blanket reactor physics and operating regimes). Also smaller and lighter weight than traditional reactors, much smaller in fact according to some recent designs such as THORcon.
I suppose if you're going to dream you should dream large.

Practically this is a system with zero operating units (although I think that may change in India and/or China in the next few years)

140 000 000 miles away from Earth is not the distance to discover some of your key operating parts aren't quite as reliable as you thought they'd be.  :(
Title: Re: Power options for a Mars settlement
Post by: JamesH65 on 03/31/2016 09:57 am
My favorite word one word solution:
Thorium.
FLIBE or NAbe thorium generation plant. Could produce immense amount of power and potentially use ISRU from martian soil to make new thorium for the plant. Tons of potential power production capability because of the extremely high thermal spectrum regime of a thorium reactor (due to liquid blanket reactor physics and operating regimes). Also smaller and lighter weight than traditional reactors, much smaller in fact according to some recent designs such as THORcon.
I suppose if you're going to dream you should dream large.

Practically this is a system with zero operating units (although I think that may change in India and/or China in the next few years)

140 000 000 miles away from Earth is not the distance to discover some of your key operating parts aren't quite as reliable as you thought they'd be.  :(

Are you implying that someone would be brave/stupid enough to send a untried/untested reactor to another world?  My impression would be that stuff would, in all likelihood, be rather well tested before it goes anywhere.
Title: Re: Power options for a Mars settlement
Post by: Spaniard on 03/31/2016 10:25 am
The MIT work suggests 6000Kw/Kg thin films are possible, but probably won't survive launch and/or landing.
From ISRU point of view, you could send a thin film printer using local materials for the rest of elements.
Only capture surface require some complex and difficult of local extract elements.
The rest could be plastics or aluminium from local resources.

Not for the first colony but it should be ready in after a couple missions later, when all ISRU demostrators was worked well.

Using this way, 6000Kw/Kg even more seems achievable.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 03/31/2016 06:15 pm
As Robotbeat said, this has been discussed before, but dust storms don't mean zero sunlight (the solar-powered MERs survived at least one large storm).
Survived, as in "not destroyed."

I don't think that's going to be enough for a settlement to wait out such a storm.

Well, they continued to have power, otherwise they would have frozen.


Quote
is 4630 m^2 worst case. So 10x that is 46300 m^2, a square about 216m on a side, per 100 people.

That doesn't sound too bad. IKAROS thin films were 25 micrometers thick, so 46300 square meters is 1.16 cubic meters. I believe they were silicon, density about 2300 kg/cubic meter, so that's less than 3 metric tons for the cells.

I don't know how much the power cables etc. would mass, but ... huge areas of thin film are not mass prohibitive, since modern thin films can be really really thin.

Quote
(but at 60Kw/ person that's. 12x bigger)

Where does 60 Kw/person come from?

I'd imagine the big power requirement would be the propellant ISRU and life support requirements would be rather small in comparison.

Mars is very cold, but the atmosphere is very thin, so it might not transfer heat as effectively -- the thermal environment might actually be more benign than the near-polar Antarctic research stations. Has anyone run the numbers on that?

Oxygen is going to be a byproduct of the ISRU, and you might be able to get enough oxygen for breathing with plants/algae at very small power consumption (use natural Martian sunlight instead of artificial light - unlike the Moon, the day/night cycle is close enough to Earth's).

EDIT: fixed quote tag
Title: Re: Power options for a Mars settlement
Post by: shooter6947 on 03/31/2016 06:27 pm

Well, they continued to have power, otherwise they would have frozen.

The MERs have 238Pu-powered Radioisotope Heater Units (RHUs) to provide heating for precisely this reason.  So they could survive with zero power for some period of time and still not freeze because of the RHU power.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 03/31/2016 07:13 pm
The MERs have 238Pu-powered Radioisotope Heater Units (RHUs) to provide heating

They do, but...

Quote
  So they could survive with zero power for some period of time and still not freeze because of the RHU power.

...I'm not sure they are that capable, because there have repeatedly been concerns of the MER surviving the winter due to diminished sunlight, needing to park on a north-facing slope etc.

So I don't think they can survive zero power.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 03/31/2016 11:15 pm
Are you implying that someone would be brave/stupid enough to send a untried/untested reactor to another world?  My impression would be that stuff would, in all likelihood, be rather well tested before it goes anywhere.
Exactly.

And that has not even begun on Earth.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 03/31/2016 11:32 pm
Well, they continued to have power, otherwise they would have frozen.
No. Each rover (in fact most probes) were fitted with a number of Pu radioisotope heaters to keep certain parts of the electronics and mechanics above failure temperatures.
Quote

Where does 60 Kw/person come from?
It's from one of the reports in the thread Robotbeat cited at the start of this thread.
Quote
I'd imagine the big power requirement would be the propellant ISRU and life support requirements would be rather small in comparison.
I'd agree but those numbers gave a quick snapshot of various groups thinking.
Quote
Mars is very cold, but the atmosphere is very thin, so it might not transfer heat as effectively -- the thermal environment might actually be more benign than the near-polar Antarctic research stations. Has anyone run the numbers on that?
Probably, but I don't have them. I will note while you've still got some fluid flow you'll get convection.

Anyone who'se found a draught in a house will now that a small airflow can suck out a lot of heat from a structure.  :(
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/01/2016 12:11 am

Quote
Anyone who'se found a draught in a house will now that a small airflow can suck out a lot of heat from a structure.  :(

When you have that kind of draught in a martian habitat you have a much bigger problem than heat loss.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 04/01/2016 02:35 am
Yeah and one would think habitats would be insulated...
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/01/2016 02:49 am
Yeah and one would think habitats would be insulated...
Personally I would think they'd be buried given the radiaton background level and low surface temperatures at night.
Title: Re: Power options for a Mars settlement
Post by: sanman on 04/14/2016 06:49 pm
Came across this article about GE's supercritical CO2 turbine, which although small and lightweight, could be used to power a small city:

https://www.technologyreview.com/s/601218/desk-size-turbine-could-power-a-town/

So what would be the best scenario to use this thing for power conversion on Mars? Hook it up to a nuclear reactor? What about geothermal/areothermal?

Or given Mars' unique environment, is there something better than supercritical CO2 to run a turbine with?
I've only assumed that the more efficient size/weight package of this turbine, coupled with the abundance of atmsopheric CO2 on Mars, would make it a good candidate.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/15/2016 09:32 am
Came across this article about GE's supercritical CO2 turbine, which although small and lightweight, could be used to power a small city:

https://www.technologyreview.com/s/601218/desk-size-turbine-could-power-a-town/

So what would be the best scenario to use this thing for power conversion on Mars? Hook it up to a nuclear reactor? What about geothermal/areothermal?

Or given Mars' unique environment, is there something better than supercritical CO2 to run a turbine with?
I've only assumed that the more efficient size/weight package of this turbine, coupled with the abundance of atmsopheric CO2 on Mars, would make it a good candidate.
The unit shown in the picture GE Global Research have released is sized for 10MW, which would be adequate for about 166 people even with the worst case power estimate of 60Kw/person.

The British AGR did 40bar at 650c but CO2 goes supercritical at above 73.9bar. I don't think anyone's run a gas cooled reactor at that pressure.  Gas reactors also tend to be quite big for their power output. It's not clear to me if that's due to inherent physics or just very conservative design.

People keep talking about Fission Power Systems for Mars but no one is anywhere near the scale needed, unless you like the idea of Mars littered with large numbers of spent nuclear fuel cores.  :(

A key issue for all designs is what if the LV crashes and dumps it in the sea. Water is a good moderator, and moderator behavior is inversely proportional to temperature. It's a design requirement that a space nuclear system not go critical even if it's suddenly put into a much better moderating environment than air or vacuum (and that environment floods inside the reactor). This may explain the US fondness for fast or epithermal spectrum designs, despite their need for substantial enrichment.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/15/2016 03:42 pm
Spent nuclear fuel cores sounds like a great idea to help terraform the planet! Long-duration decay heat could help liberate volatiles from the soil. :D
Title: Re: Power options for a Mars settlement
Post by: Kansan52 on 04/29/2016 11:28 pm

Well, they continued to have power, otherwise they would have frozen.

The MERs have 238Pu-powered Radioisotope Heater Units (RHUs) to provide heating for precisely this reason.  So they could survive with zero power for some period of time and still not freeze because of the RHU power.

Sorry to come late to this discussion. The MERS were never expected to last the Martian winter due to dust build-up on the PVs. The RHUs could not keep them warm enough (Spirit). Then the dust devils unexpectedly cleared the PVs. Even then, only southern exposure gave enough sun light to survive. Once Spirit got stuck and could not park in 'winter mode', it froze up. So both are needed.
Title: Re: Power options for a Mars settlement
Post by: Bob Shaw on 04/29/2016 11:37 pm

A key issue for all designs is what if the LV crashes and dumps it in the sea.


This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins. Unlike the Moon, Mars rotates in 24hrs, so no need to deal with 14 days of night. The Moon is a different matter.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/30/2016 01:37 am

A key issue for all designs is what if the LV crashes and dumps it in the sea.


This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins. Unlike the Moon, Mars rotates in 24hrs, so no need to deal with 14 days of night. The Moon is a different matter.
A fair point, but this still leaves the question of what happens in a prolonged dust storm.

I think some system to tap the temperature difference between Mars surface and sub surface temp (which cannot be stopped by dust) is the way to have a backup power system.
Title: Re: Power options for a Mars settlement
Post by: sanman on 04/30/2016 08:18 am

A fair point, but this still leaves the question of what happens in a prolonged dust storm.

I think some system to tap the temperature difference between Mars surface and sub surface temp (which cannot be stopped by dust) is the way to have a backup power system.

You mean some sort of ground loop heating?

Even in spite of Mars' thin atmosphere, could there be some way to harness wind power on Mars during a dust storm - maybe using a very large and lightweight wind turbine?
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 04/30/2016 08:19 pm
Even in spite of Mars' thin atmosphere, could there be some way to harness wind power on Mars during a dust storm - maybe using a very large and lightweight wind turbine?

'Very large' and 'lightweight' tends to be inconsistent! :) I suspect that for the mass required you'd get more power by adding more solar and storage.

There are a number of potential back-up power systems to replace solar during prolonged dust storms (nuclear wouldn't be much affected, of course), the most obvious being batteries and ICE generators or fuel cells utilising stored ISRU methalox. Then there's the strategy of turning off non-essential power-using activities. Finally, a dust storm wouldn't reduce the output of solar to zero - it seems the MERs worst reduction was ~80% - and such a storm wouldn't prevent base personnel cleaning the solar cells manually.
Title: Re: Power options for a Mars settlement
Post by: inonepiece on 04/30/2016 09:29 pm

A key issue for all designs is what if the LV crashes and dumps it in the sea.


This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins.
What do you both imagine might happen if it dumps in the sea?
Title: Re: Power options for a Mars settlement
Post by: sewebster on 04/30/2016 09:36 pm
What do you both imagine might happen if it dumps in the sea?
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 04/30/2016 11:16 pm
The up and coming new solar cell tech is lead halide perovskite which is cheap and easy to manufacture as an aqueous solution. In just a few years they've already hit 20% with no real end in site. Certainly not viable yet but it will be a few days before they need them on mars. :) One of the big problem right now is degradation due to atmospheric water, probably not much of an issue on mars. Early indications are that they are well suited to space applications with low temperatures and high radiation flux, exhibiting little degradation compares to silicon or gallium cells. If there is Thorium on mars then there is probably lead at too. Now if SpaceX could just find someone in the solar power industry to look into it ... Definitely something to keep and eye on for the future.
Title: Re: Power options for a Mars settlement
Post by: inonepiece on 05/01/2016 01:07 am
Ha.  I assume you are joking sewebster, but there are always people who won't realize it...
Title: Re: Power options for a Mars settlement
Post by: sewebster on 05/01/2016 03:33 am
Ha.  I assume you are joking sewebster, but there are always people who won't realize it...

Probably a good rule of thumb to always assume I am joking...
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/02/2016 09:47 am
You mean some sort of ground loop heating?
No I was thinking of a low BP liquid used to drive a turbine. On Earth such systems have generated 500Kw/ borehole.  However just raw temperature management is likely to be an issue on Mars. The day/night temperature swing seems quite high and being able to manage that with relatively passive systems sounds like a good idea.
Quote
Even in spite of Mars' thin atmosphere, could there be some way to harness wind power on Mars during a dust storm - maybe using a very large and lightweight wind turbine?
I think Robobeat referenced a NASA report earlier in the thread. The fact remains the density is about 1% of Earth's density means even if you get an average higher speed you still need a lot of collection area to collect enough power.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/02/2016 10:11 am

A key issue for all designs is what if the LV crashes and dumps it in the sea.


This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins.
What do you both imagine might happen if it dumps in the sea?

It would disintegrate into sub critical parts - once the range safety officer presses the trigger, or upon a high speed impact - and spread some low enriched Uranium around on the sea bed.

As long as the reactor hasn't been operating, there would be no fission products and hence no radioactive danger.

There'd be less concern than there would be for a large Plutonium RTG.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/03/2016 06:57 pm
It would disintegrate into sub critical parts - once the range safety officer presses the trigger, or upon a high speed impact - and spread some low enriched Uranium around on the sea bed.
You might like to check the enrichment levels in space nuclear systems.

The ones that have been fielded or study are well into the HEU range IE 20%+, usually around 90%+ U235
Quote
As long as the reactor hasn't been operating, there would be no fission products and hence no radioactive danger.
Uranium and Plutonium are highly toxic without being radioactive.

The NASA estimate for SNR development on one slide was $19Bn.

I hope that's wrong, but it's their estimate.  :(
Title: Re: Power options for a Mars settlement
Post by: enzo on 05/03/2016 08:30 pm
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.
Title: Re: Power options for a Mars settlement
Post by: biosehnsucht on 05/03/2016 09:37 pm
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.

That's a good point, regular batteries (regardless of chemistry) aren't the only way we can store energy.

Flywheels (as you said), compressed gas (CO2 is plentiful, can compress it, store it, then run it back through a turbine to generate power), and even simply burning ISRU-collected CH4/LOX in a methane ICE or turbine of some kind (assuming your ISRU generation and storage is beyond your MCT refuel needs - assumes you aren't bringing Hydrogen with you anymore but harvesting it locally from water or other sources and in sufficient quantity, since until then that will be a major ISRU fuel constraint).

Flywheels are probably easiest - you could even ship them without their weights, just empty containers in a circle/tube/whatever, and fill them with Martian 'dirt'. Would need a way to balance them but there's probably some easy ways to do it such as having either stick-on weights like balancing a car's wheel or simply adding and removing material from the containers. Either way, you can basically take a wheel balancer you'd find at the tire shop and use it's balance detection mechanism for giving instruction on fine tuning the balance.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 05/03/2016 10:37 pm
Then there's the strategy of turning off non-essential power-using activities.

You could keep a reserve of water, etc. long enough to last through any dust storm so that you could turn off the water purifiers EDIT: during storms.

Quote
Finally, a dust storm wouldn't reduce the output of solar to zero - it seems the MERs worst reduction was ~80% - and such a storm wouldn't prevent base personnel cleaning the solar cells manually.

If it's that "small" a reduction, plants in a Martian greenhouse might not need supplemental lighting even during a dust storm - 1/5 of normal Martian sunlight is something like 1/15 of normal Earth sunlight, which I think is still more than gets through thick clouds on Earth. And plants grow fine in heavily cloudy regions on Earth.


A key issue for all designs is what if the LV crashes and dumps it in the sea.


This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins.
What do you both imagine might happen if it dumps in the sea?

It's a political concern, not a matter of "real" risk.

Realistically, probably nothing would happen. Water is very good radiation shielding - and radioactive stuff isn't nearly as much of an ecological problem as people think anyway (since ecosystems - unlike human public health - don't care about individual outcomes but only populations).
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 05/03/2016 10:51 pm
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.
A relatively recent case of a power flywheel RUD is described here:

http://www.timesunion.com/local/article/Flywheels-fail-at-energy-project-2227225.php

Pictures of the externally-visible aftermath are here:

http://eastwickpress.com/news/2011/07/a-mishap-at-the-beacon-power-frequency-flywheel-plant/
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/04/2016 01:54 am
It's a political concern, not a matter of "real" risk.

Realistically, probably nothing would happen. Water is very good radiation shielding
It's also a very good neutron moderator potentially pushing a marginally sub critical design over the edge into going critical and starting a chain reaction, giving a long lived radiation source, if not an outright nuclear explosion.

Personally that's why I like molten lead or lead alloy designs. On a crash there's no way for the water to penetrate inside the cooling channels, as they are filled with solid alloy.
Quote
- and radioactive stuff isn't nearly as much of an ecological problem as people think anyway (since ecosystems - unlike human public health - don't care about individual outcomes but only populations).
True, but it represents another complex system that has to be designed, tested and certified before you can move to a settlement.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/04/2016 01:57 am
A relatively recent case of a power flywheel RUD is described here:

http://www.timesunion.com/local/article/Flywheels-fail-at-energy-project-2227225.php

Pictures of the externally-visible aftermath are here:

http://eastwickpress.com/news/2011/07/a-mishap-at-the-beacon-power-frequency-flywheel-plant/
Interesting stuff.

Note while these are quite small for Earth use they might be quite large for Mars use. It's impressive a unit failed but the flywheel released its energy by shattering, leaving a fine powder. A potential fire and inhalation hazard, but not an explosive one, as you would see if a complete fly wheel flew through the air, scything everything in its path.
Title: Re: Power options for a Mars settlement
Post by: Mongo62 on 05/04/2016 02:35 am
It's a political concern, not a matter of "real" risk.

Realistically, probably nothing would happen. Water is very good radiation shielding
It's also a very good neutron moderator potentially pushing a marginally sub critical design over the edge into going critical and starting a chain reaction, giving a long lived radiation source, if not an outright nuclear explosion.

But the reactor would NOT be "marginally sub-critical". It would not be remotely close to criticality during launch, and could not become critical without a no doubt careful procedure only done once it is located at its permanent location on Mars. For example, having the fuel pellets carried in several separate flights, such that no single collection of pellets can approach criticality, even if they are all mashed together into one lump.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 05/04/2016 03:22 pm
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.
A relatively recent case of a power flywheel RUD is described here:

http://www.timesunion.com/local/article/Flywheels-fail-at-energy-project-2227225.php

Pictures of the externally-visible aftermath are here:

http://eastwickpress.com/news/2011/07/a-mishap-at-the-beacon-power-frequency-flywheel-plant/

Reading your excellent citations shows how FEW KiloWatt HOURS are stored and accessible per flywheel.
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 05/04/2016 04:03 pm
A relatively recent case of a power flywheel RUD is described here:

http://www.timesunion.com/local/article/Flywheels-fail-at-energy-project-2227225.php

Pictures of the externally-visible aftermath are here:

http://eastwickpress.com/news/2011/07/a-mishap-at-the-beacon-power-frequency-flywheel-plant/

Reading your excellent citations shows how FEW KiloWatt HOURS are stored and accessible per flywheel.
Yup, it's more of a short-term buffer to cover the minutes it takes for another generator to spin up.   I don't think they make sense for long-term power storage.   

On Mars, having the ability to burn spare ISRU-generated methane+oxygen to cover solar power deficits during dust storms would make a lot more sense; the only additional mass required would be some number of methane-burning engines and generators and associated electrical switch gear.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/04/2016 06:52 pm
But the reactor would NOT be "marginally sub-critical". It would not be remotely close to criticality during launch, and could not become critical without a no doubt careful procedure only done once it is located at its permanent location on Mars. For example, having the fuel pellets carried in several separate flights, such that no single collection of pellets can approach criticality, even if they are all mashed together into one lump.
Those are design decisions. Fast or epithermal spectrum reactors are believed to be more compact as they have no volume dedicated to moderator. However they need enrichment because the capture cross sections for U and Pu are lower at higher energies.

So what's marginal at a fast spectrum becomes much less marginal IE supercritical when immersed into a large pool of moderator, especially if that moderator floods into the coolant channels, as it will for a gas or room temperature liquid.

I like the reactor option. It's a closed system, excellent power density, independent of outside weather conditions.

But with USG procurement it's going to be eyewateringly expensive with a very small market. That's important because compact --> highly enriched and the USG is going to be very wary of any private entity holding

About the only things I can think of to lower that cost are trying to get commonality between the fuel elements for thermal and power reactors, as (currently) NASA seems to be putting some more money in NTR than power generation.
Title: Re: Power options for a Mars settlement
Post by: sewebster on 05/04/2016 07:51 pm
I believe the energy density for flywheels is similar to batteries, so while they might be useful, they don't help for something long term like a dust storm any more than (more) batteries would.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 06/13/2016 07:15 am
Highly speculative: I wanted to connect two dots: Nuclear power for Mars and Elon Musks recent talk with the Secretary of Defense.
If I wanted a highly reliable and compact nuclear reactor, I would look at the A1B https://en.wikipedia.org/wiki/A1B_reactor (https://en.wikipedia.org/wiki/A1B_reactor). And then I would try to talk to the man in charge...
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/13/2016 07:50 am
Are you saying Elon Musk summoned the Secretary of Defense not the other way around?

 ;D

P.S. I don't think Elon Musk can get that technology from the Navy.

Edit: I also don't think a technology developed for Navy use with unlimited cooling water available would be suitable for Mars. I may be wrong on this one.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 06/13/2016 08:14 am
Since the talk was at the Pentagon, he obviously did not summon Ash Carter.  :)

But I think that the US Navy has the deepest knowledge on how to run compact nuclear reactors. If the A1B is unsuitable, there might be other designs. I would suspect that a boomer can't use all that much cooling water, if it wants to run ultra silent.
Title: Re: Power options for a Mars settlement
Post by: mvpel on 06/13/2016 02:28 pm
Navy reactors were magnificent works of technological art two decades ago when I was taking my ASVAB; I wonder what they must be like these days. The specs of the A1B are remarkable.

Remember, Bechtel is a "private company" too.

I think that nuclear power on Mars, like it or not, is really going to be the difference between a camping trip and a second branch of human civilization.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/13/2016 02:31 pm
Navy reactors were magnificent works of technological art two decades ago when I was taking my ASVAB; I wonder what they must be like these days. The specs of the A1B are remarkable.

Remember, Bechtel is a "private company" too.

I think that nuclear power on Mars, like it or not, is really going to be the difference between a camping trip and a second branch of human civilization.
At-scale solar farms would also work, but I agree nuclear power is quite attractive on Mars surface. The big problem is heat exchange.
Title: Re: Power options for a Mars settlement
Post by: mvpel on 06/13/2016 02:54 pm
At-scale solar farms would also work, but I agree nuclear power is quite attractive on Mars surface. The big problem is heat exchange.

Here's a concept from about a dozen years ago that uses lithium heat pipes for heat exchange, and cesium thermionic cells for power conversion, delivering 1.2MWt and 100Kwe:

The Martian Surface Reactor: An Advanced Nuclear Power Station for Manned Extraterrestrial Exploration  (http://web.mit.edu/22.33/FINAL%20REPORT/22.033%20MSR%20Final%20Report.pdf)
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/13/2016 03:02 pm
At-scale solar farms would also work, but I agree nuclear power is quite attractive on Mars surface. The big problem is heat exchange.

Here's a concept from about a dozen years ago that uses lithium heat pipes for heat exchange, and cesium thermionic cells for power conversion, delivering 1.2MWt and 100Kwe:

The Martian Surface Reactor: An Advanced Nuclear Power Station for Manned Extraterrestrial Exploration  (http://web.mit.edu/22.33/FINAL%20REPORT/22.033%20MSR%20Final%20Report.pdf)
...and has a total mass of several tons. It /might/ be better than solar from a specific power perspective if you include mass of batteries (thin films are better and with state of the art batteries, could be better than nuclear), but not much.

The radiators look like they're in the multiple ton range for 1.2MWth (100kWe).

No, I think you'd want nuclear at several megawatts electric. And not thermionic or thermocouples for heat conversion buy a turbine.

If you're going to bother with the hassle of going nuclear, then don't mess around. Do at least 1MWe.
Title: Re: Power options for a Mars settlement
Post by: mvpel on 06/13/2016 04:02 pm
Good point... Doesn't BFR intend a hundred tons to the Martian surface? "Go big or stay home."

Supercritical CO2 turbines are rather interesting technology - you can use the Martian atmosphere as your turbine's working fluid.
Title: Re: Power options for a Mars settlement
Post by: Tyber1 on 08/17/2016 05:30 pm
While nuclear would be useful for starting a colony, I think nuclear energy should be reserved for temporary projects like starting colonies, deep space travel and outer solar system mining. It's easy to forget because it's so plentiful but nuclear power is a non-renewable energy source.
Title: Re: Power options for a Mars settlement
Post by: Lar on 08/17/2016 09:37 pm
While nuclear would be useful for starting a colony, I think nuclear energy should be reserved for temporary projects like starting colonies, deep space travel and outer solar system mining. It's easy to forget because it's so plentiful but nuclear power is a non-renewable energy source.
Um?  It depends on your fuel. Breeders won't run out of fuel for a very very long time. I don't see this as a serious show stopper.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 08/18/2016 07:30 am
The only problem with nuclear power is the disposal of waste and old reactors. These things are contaminated with radiation producing isotopes and chemically very poisonous elements. Both things make a safe disposal almost impossible. A disposal site would have to last millions of years without interference or releasing any of the contaminated material into the environment.

When factoring in disposal, I think solar is the vastly simpler power source, even on Mars. Especially when talking about terraforming Mars in the long term.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 08/18/2016 08:25 am
The only problem with nuclear power is the disposal of waste and old reactors. These things are contaminated with radiation producing isotopes and chemically very poisonous elements.

Much less a problem with molten salt reactors, especially those which burn thorium.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 08/18/2016 08:40 am
It seems Lockheed Martin (http://www.lockheedmartin.com/us/products/compact-fusion.html)'s portable 100MW High beta fusion reactor (https://en.wikipedia.org/wiki/High_beta_fusion_reactor) is still alive (http://fusion4freedom.us/lockheed-martin-one-step-closer-portable-nuclear-generator/).

If it really fits at the back of a truck, it would be portable to Mars.

Another Link: Lockheed Still Supporting Portable Nuclear Generator (http://www.defensenews.com/story/defense/innovation/2016/05/03/lockheed-nuclear-fusion-generator-investment/83870398/)
Title: Re: Power options for a Mars settlement
Post by: MickQ on 08/19/2016 08:53 am
And don't forget the Gen4 power module.  70mw thermal and 25mw electrical.  10 years before replacement or refuel.  Worth looking at.

Mick
Title: Re: Power options for a Mars settlement
Post by: geza on 08/21/2016 07:23 am
Don't forget that Elon plans to send the first cargo MCT to Mars in 2022 to produce the return fuel for the fist crew launched NET in 2024. As fuel production is quite energy-intensive, the '22 flight must carry a significant source of energy. It must be robotically depoyable. I do not think that any of the nuclear options can be developed to be flight ready in time.
Title: Re: Power options for a Mars settlement
Post by: BobHk on 08/21/2016 05:11 pm
Possibility of a submarine based nuclear power system being adapted to a ship sent to Mars?  Just putting this out there, how many years to integrate?
Title: Re: Power options for a Mars settlement
Post by: BobHk on 08/21/2016 05:20 pm
The only problem with nuclear power is the disposal of waste and old reactors. These things are contaminated with radiation producing isotopes and chemically very poisonous elements. Both things make a safe disposal almost impossible. A disposal site would have to last millions of years without interference or releasing any of the contaminated material into the environment.

When factoring in disposal, I think solar is the vastly simpler power source, even on Mars. Especially when talking about terraforming Mars in the long term.

https://upload.wikimedia.org/wikipedia/commons/thumb/d/d7/Naval_Reactor_Compartment_Packages_in_Trench_94_at_Hanford%2C_WA.png/725px-Naval_Reactor_Compartment_Packages_in_Trench_94_at_Hanford%2C_WA.png

This is earth and these are old sub reactor compartments - this is how we dispose of them on Earth.  Mars can do the same.  Fuel is pulled and the compartment cut out and, well, dumped.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 08/21/2016 07:42 pm
To be clear, I didnt meant to say that disposal is impossible or even prohibitive for nuclear. Its just very hard. And if you factor in disposal, solar power becomes more favourable in my opinion. Even the disposal containers posted above do not last millions of years. They need to be taken care of. You cant dump them anywhere easily either because no geological site is stable for millions of years. If you want to terraform Mars, water is going to get everywhere, you cant put them in some crater either.
Title: Re: Power options for a Mars settlement
Post by: the_other_Doug on 08/21/2016 08:17 pm
To be clear, I didnt meant to say that disposal is impossible or even prohibitive for nuclear. Its just very hard. And if you factor in disposal, solar power becomes more favourable in my opinion. Even the disposal containers posted above do not last millions of years. They need to be taken care of. You cant dump them anywhere easily either because no geological site is stable for millions of years. If you want to terraform Mars, water is going to get everywhere, you cant put them in some crater either.

I though the longest half-lives of most of the current spent fuel rods is in the tens of thousands of years, not millions.  And last I read, there aren't any terraforming concepts that would take less than tens of thousands of years.  So, I'm not certain I understand the concern.

Let's not get ourselves into knee-jerk, bypass-rational-thought patterns of decision-making just because the word "nuclear" is uttered, eh?  ;)
Title: Re: Power options for a Mars settlement
Post by: zodiacchris on 08/21/2016 08:45 pm
Well, the term half-life defines the time in which the radioactivity of the material drops by half. So if it is a few thousand times more radioactive than the lethal dose for humans (depending on time of exposure or uptake of radionuclide elements), which Plutonium is, it takes way more than 10,000 years before you can put it in your pocket or expose it to the environment. The Navy is only storing those reactors, that is not long term disposal.
IMO you'd want to get the colony radioactive waste off planet, dump it in a stable solar orbit or something like that, a million years out there amounts to very little.
2 cents...
Cheers,
Chris
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 08/21/2016 08:57 pm
Possibility of a submarine based nuclear power system being adapted to a ship sent to Mars?  Just putting this out there, how many years to integrate?

Although the US Navy has long experience with very reliable reactors, the are all water-cooled.

My guess is, Musk also controlling a solar power and battery company, he will go with that to start.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/22/2016 01:43 am
Don't forget that Elon plans to send the first cargo MCT to Mars in 2022 to produce the return fuel for the fist crew launched NET in 2024. As fuel production is quite energy-intensive, the '22 flight must carry a significant source of energy. It must be robotically depoyable. I do not think that any of the nuclear options can be developed to be flight ready in time.

Except they're not starting now, right?  They've been serious about Mars from the get go, and clearly power generation is a major enabling technology with long development times, so I am sure they were seriously studying options even 6 years ago, and you have no way of knowing what private project they may have going with any of the nuclear vendors.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/22/2016 02:11 am
Indeed. If they're considering nuclear, you can be certain that they're not starting just now.

We also know that SpaceX has been considering designs for deployable surface solar arrays. Inflatable deployment arrays, in particular, is one option they've looked at.
Title: Re: Power options for a Mars settlement
Post by: Lar on 08/22/2016 03:19 pm
We have two power for mars threads, someone pm me why not to merge them...

See

http://forum.nasaspaceflight.com/index.php?topic=34836.0 (it's in a different section)
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 08/22/2016 07:06 pm
Perhaps the thing to do is a separate section for Mars habitability, landing locations, power gen, etc discussions that is independent of talking about whose launcher / organization/ business plan is used to get there.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 08/22/2016 07:31 pm
Perhaps the thing to do is a separate section for Mars habitability, landing locations, power gen, etc discussions that is independent of talking about whose launcher / organization/ business plan is used to get there.

We have done extensive discussion on this in the general Mars section. Not so much on landing locations, as far as I remember. But that section is the place to discuss this independent of SpaceX. Though SpaceX MCT has the additional requirement of much water at the landing site. More than another architecture would need.
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 08/22/2016 09:29 pm
Do you mean the one under the "HLV / SLS / Orion / Constellation" main section?   I took that to be about specifically NASA-based plans, launchers, and equipment.  The top level is heavily organized by launcher technology, except for the "General" section.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 08/23/2016 04:35 am
I mean this section.

http://forum.nasaspaceflight.com/index.php?board=21.0

Missions to Mars (HSF)
Title: Re: Power options for a Mars settlement
Post by: jfallen on 08/23/2016 11:18 am
I think all of this will become a lot clearer at the end of next month, but having followed Elon and his companies for about 14 years, my bet is on solar.  His other companies involve batteries and solar power generation, it just makes sense.  And it is excellent PR don't forget, sales fund all his pet projects.  It is going to take some cash to colonize Mars and this would be some amazing PR for solar power.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 08/23/2016 05:00 pm
I think all of this will become a lot clearer at the end of next month, but having followed Elon and his companies for about 14 years, my bet is on solar.  His other companies involve batteries and solar power generation, it just makes sense.  And it is excellent PR don't forget, sales fund all his pet projects.  It is going to take some cash to colonize Mars and this would be some amazing PR for solar power.

I like nukes for Mars surface power but were SX to go that way Elon would be placing the fate of his endeavor in someone else's hands, something he tends to avoid. 
(1) Somebody, not SX would design & build & price the nuke.
(2) Others in the political domain would be able to veto use of a nuke.  Heck, not even veto as it's prohibited so he would need an exemption.  Musk has done well interacting with governments, so this is not completely out of the question.

I agree that solar is aligned with his other companies, especially after the megamerger.  It would also alienate some current solar fanatic Tesla/Solar fans were he to opt for nuclear.

1st blush will be solar with nuclear the long pole being worked behind the scenes for eventual base expansion.

Title: Re: Power options for a Mars settlement
Post by: jfallen on 08/24/2016 01:24 pm
Musk has mentioned nuking the poles, so he definitely isn't anti-nuke.   I am with you, I think nuclear is the best option, but I also agree with you that Elon doesn't want this out of his control.  He seems to be very impatient with things, which is probably one of the things that has made him so successful.  He will probably go with solar because he can own the whole process and he knows it best.  I would like to think that there is a secret MarsX Base 2.0 reactor plan that is quietly being worked behind the scenes, but Elon normally isn't that good at keeping secrets and we probably would have heard about it somewhere.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 08/24/2016 01:29 pm
Musk has mentioned nuking the poles, so he definitely isn't anti-nuke.

He has clarified later, that he did not mean conventional nukes as they exist now but some future development without lasting radiation.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/24/2016 06:42 pm
Musk has said pretty clearly that he's not opposed to nuclear fission.
Title: Re: Power options for a Mars settlement
Post by: BobHk on 08/24/2016 10:22 pm
Do any of you think it would be beyond the realm of possibility for Musk to ask the Navy to provide a reactor and crew to operate it for the MCT that could be a backup power system, doesn't have to be full sized just big enough to power essential systems there to and on mars and back.  I suggested this to my cousins, Navy was interested, Air Force scowled.  Apparently space belongs to the Air Force.
Title: Re: Power options for a Mars settlement
Post by: KelvinZero on 08/25/2016 12:43 am
Do any of you think it would be beyond the realm of possibility for Musk to ask the Navy to provide a reactor and crew to operate it for the MCT that could be a backup power system, doesn't have to be full sized just big enough to power essential systems there to and on mars and back.  I suggested this to my cousins, Navy was interested, Air Force scowled.  Apparently space belongs to the Air Force.
Discussed this a bit back and the main issue was radiators. A couple of people including myself suggest using the waste heat to melt ice underground, also creating circulating water pool for cooling. Maybe the goal should be to plug in an off the shelf reactor, at a point in ISRU development when the radiator problem has solved itself because access to a lot of water has been established. Whether this is early or late is the fiddly bit.

Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/25/2016 05:05 am
Do any of you think it would be beyond the realm of possibility for Musk to ask the Navy to provide a reactor and crew to operate it for the MCT that could be a backup power system, doesn't have to be full sized just big enough to power essential systems there to and on mars and back.  I suggested this to my cousins, Navy was interested, Air Force scowled.  Apparently space belongs to the Air Force.
Discussed this a bit back and the main issue was radiators. A couple of people including myself suggest using the waste heat to melt ice underground, also creating circulating water pool for cooling. Maybe the goal should be to plug in an off the shelf reactor, at a point in ISRU development when the radiator problem has solved itself because access to a lot of water has been established. Whether this is early or late is the fiddly bit.

Nuclear, if he can pull it off, has a clear advantage over everything else.  Compactness and the availability of process heat being just the leading two.

It's not Musk's style to hook up with a government body like the navy. If he'll go that route, he would do it directly with the manufacturers, with implicit government blessing.

There was talk in other threads about the possibility of bootstrapping the first base robotically.  I am willing to give this path more credence if it doesn't require installing acres of solar panels with no people present.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 08/25/2016 07:03 am
Do any of you think it would be beyond the realm of possibility for Musk to ask the Navy to provide a reactor and crew to operate it for the MCT that could be a backup power system, doesn't have to be full sized just big enough to power essential systems there to and on mars and back.  I suggested this to my cousins, Navy was interested, Air Force scowled.  Apparently space belongs to the Air Force.

Well, there was the secret meeting with Ash Carter in June (http://edition.cnn.com/2016/06/08/politics/elon-musk-ash-carter-pentagon/).

Elon wrote on Twitter, that it was "Something about a flying metal suit". (https://twitter.com/elonmusk/status/740723195431538689)
Title: Re: Power options for a Mars settlement
Post by: jfallen on 08/26/2016 05:47 pm
Do any of you think it would be beyond the realm of possibility for Musk to ask the Navy to provide a reactor and crew to operate it for the MCT that could be a backup power system, doesn't have to be full sized just big enough to power essential systems there to and on mars and back.  I suggested this to my cousins, Navy was interested, Air Force scowled.  Apparently space belongs to the Air Force.

Well, there was the secret meeting with Ash Carter in June (http://edition.cnn.com/2016/06/08/politics/elon-musk-ash-carter-pentagon/).

Elon wrote on Twitter, that it was "Something about a flying metal suit". (https://twitter.com/elonmusk/status/740723195431538689)

I would guess that a partnership with DARPA would be more likely.
Title: Re: Power options for a Mars settlement
Post by: Oersted on 08/29/2016 12:11 am
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.

A flywheel should somehow be dual-use. Otherwise it sounds like a very big and heavy weight to bring to the Martian surface.
Title: Re: Power options for a Mars settlement
Post by: IntoTheVoid on 08/29/2016 12:18 am
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.

A flywheel should somehow be dual-use. Otherwise it sounds like a very big and heavy weight to bring to the Martian surface.

A millstone for Martian wheat?
A bench grinder for the machine shop?

...

Why not send it up empty and fill it with martian water or other material. The key would be balancing it.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 08/29/2016 05:24 am
... that could be a backup power system, doesn't have to be full sized just big enough to power essential systems ...

One thing often missing from such discussions is the question of security of supply and redundancy. As far as I can see, there's only two options for power on Mars (other than for short-term backup) and that's nuclear and solar. Ideally then, you should have both.
Title: Re: Power options for a Mars settlement
Post by: Jcc on 09/04/2016 11:51 pm
... that could be a backup power system, doesn't have to be full sized just big enough to power essential systems ...

One thing often missing from such discussions is the question of security of supply and redundancy. As far as I can see, there's only two options for power on Mars (other than for short-term backup) and that's nuclear and solar. Ideally then, you should have both.

You can also have redundancy with solar and more solar, given its distributed nature it's easy to design with no single point of failure. Still, nuclear is a good option to provide a large quantity of power 24/7 once certain problems are solved for use on Mars.
Title: Re: Power options for a Mars settlement
Post by: oldAtlas_Eguy on 09/05/2016 05:47 pm
... that could be a backup power system, doesn't have to be full sized just big enough to power essential systems ...

One thing often missing from such discussions is the question of security of supply and redundancy. As far as I can see, there's only two options for power on Mars (other than for short-term backup) and that's nuclear and solar. Ideally then, you should have both.

You can also have redundancy with solar and more solar, given its distributed nature it's easy to design with no single point of failure. Still, nuclear is a good option to provide a large quantity of power 24/7 once certain problems are solved for use on Mars.
Even though solar would have a high level of redundancy there is still the problem of a SPOF due to a design flaw. The best defense in a solar only system is to use multiple versions, designs and sources for all the elements of the system. This then gives the no-SPOF for a solar only power source.

This is done by having differing solar implementations with only one attribute the same: the ability to deliver power to multiple common bussbars. Here the only shared tech is wire and insulators which would be the same for Nuclear or for a Nuclear solar combination.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 09/05/2016 10:45 pm
... that could be a backup power system, doesn't have to be full sized just big enough to power essential systems ...

One thing often missing from such discussions is the question of security of supply and redundancy. As far as I can see, there's only two options for power on Mars (other than for short-term backup) and that's nuclear and solar. Ideally then, you should have both.

You can also have redundancy with solar and more solar, given its distributed nature it's easy to design with no single point of failure.

No apparent SPOF - it's always the unforeseen that gets you!

Even though solar would have a high level of redundancy there is still the problem of a SPOF due to a design flaw. The best defense in a solar only system is to use multiple versions, designs and sources for all the elements of the system. This then gives the no-SPOF for a solar only power source.

That's no defense to an event that causes simultaneous different SPOFs. Difficult to see that that might be - that's why it's unforeseen ! - but even more difficult if you add nuclear into the mix.

Quote
This is done by having differing solar implementations with only one attribute the same: the ability to deliver power to multiple common bussbars. Here the only shared tech is wire and insulators which would be the same for Nuclear or for a Nuclear solar combination.

The same argument applies in favour of multiple nuclear reactors of different designs. In fact, even the wires and insulators can be made of different materials!

So, ideally you'd like multiple designs of solar alongside multiple designs of nuclear. One can imagine that getting rather expensive! The big difference is between nuclear and solar, and multiple designs of solar will probably be cheaper to realise than multiple designs of solar. Therefore I'd aim for two solar designs alongside one nuclear.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 09/06/2016 10:17 pm
Has anyone discussed power beamed from orbit?  Was reading up on it yesterday and it seemed fairly compelling.
Title: Re: Power options for a Mars settlement
Post by: QuantumG on 09/06/2016 10:38 pm
Has anyone discussed power beamed from orbit?  Was reading up on it yesterday and it seemed fairly compelling.

One miracle at a time please.
Title: Re: Power options for a Mars settlement
Post by: Pipcard on 09/06/2016 11:12 pm
Has anyone discussed power beamed from orbit?  Was reading up on it yesterday and it seemed fairly compelling.
Elon Musk hates it; he believes the energy "conversion rate" makes it nonviable (http://www.popularmechanics.com/technology/a8101/elon-musk-on-spacex-tesla-and-why-space-solar-power-must-die-13386162/).

[ Personally, I believe space solar power (talking about Earth here) and RLVs would compliment each other; SSP would be a clean, reliable (i.e. no problems with clouds and nighttime) source of energy that would drive the demand for high flight rate RLVs. And cheap high flight rate RLVs would make launch costs for a solar power satellite more feasible.

But Robotbeat claims that the real problem is the cost of the transmitter (http://forum.nasaspaceflight.com/index.php?topic=17902.msg1533316#msg1533316). ]
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 09/07/2016 08:25 pm
But Robotbeat claims that the real problem is the cost of the transmitter (http://forum.nasaspaceflight.com/index.php?topic=17902.msg1533316#msg1533316). ]

I would say that the real problem is that for any given amount and availability of power, ground-based solar is  cheaper than space-based, and much lower risk. Investment is a matter of the risk-reward ratio.

That's true for Earth; it might not be true for Mars. Except that if I was on a Mars base or colony, I wouldn't want to be reliant for power on something I'd have difficulty getting to if there's a problem. Plus ...

One miracle at a time please.
Title: Re: Power options for a Mars settlement
Post by: JasonAW3 on 09/07/2016 08:40 pm
Has anyone discussed power beamed from orbit?  Was reading up on it yesterday and it seemed fairly compelling.

If we assume that, somehow, one manages to create a beam of coherent radio waves, mange to keep a tight focus on the receiver array, you still have to deal with the inverse square law about the fall off of electromagnetic radiation.

This is in addition to converting direct current to microwaves, transmitting them to the receiver antenna, then converting them back to direct current electricity.  While great in theory, the amount of energy loss would require a few square kilometers of solar arrays to make it even worth the effort.

On top of all that, the amount of sunlight that is received at Mars is just over half of that of Earth. 
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 09/07/2016 09:25 pm
If I haven't used up my miracle allotment, I was thinking along the line of nuclear in orbit as the power supply.  Not landing the nuclear eliminates several problems and provides some advantages.  Maybe not early in settlement but seems like it would be an interesting option as you scale.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 09/07/2016 09:37 pm
Much easier to cool nuclear on the surface of Mars.  Cooling nukes in a vacuum means large radiators and that means mass.
No big inverse square losses if your nuke is in the next door crater.
No conversion to microwaves and back again losses.
Quick access to your nuke if something goes wrong.

Nukes in space transmitting to the surface are an even worse idea than space based solar.
Title: Re: Power options for a Mars settlement
Post by: biosehnsucht on 09/08/2016 06:29 am

This is in addition to converting direct current to microwaves, transmitting them to the receiver antenna, then converting them back to direct current electricity.  While great in theory, the amount of energy loss would require a few square kilometers of solar arrays to make it even worth the effort.

On top of all that, the amount of sunlight that is received at Mars is just over half of that of Earth.

While still figuratively but not quite literally pie-in-the-sky, it seems a more sensible approach (if you're going to have something power related in orbit) would be a giant solar concentrator. Toss a few solar panels on it for it's own needs and some SEP, and a method of refueling said SEP occasionally (send up a MCT to dock with it and offload some Martian CO2, perhaps) and it can station keep over your colony (or close enough to keep the concentrator aimed appropriately).

Build the concentrator such that it doesn't focus so much power that it's dangerous, but that it can focus way more than regular straight from the sun solar energy into a given area, and reflect that all down at your ground based solar PV arrays, you might get a nice gain on power? Bonus if you get enough gain that you can then pull thermal energy off the panels as well, and get some free heating for your greenhouses or what-have-you. If something goes wrong with the collector, it's not deadly (like a mis-aimed microwave power station) and just means you're gonna be on power rations ...

For a second slice of pie-in-the-sky, position another concentrator (or several) such that you can bounce sunlight around the planet when on the night side, and get 24/7 solar power.

Of course at this point we're probably talking large enough installations you could be using them to melt the ice caps as well...
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 09/08/2016 06:39 am

Build the concentrator such that it doesn't focus so much power that it's dangerous, but that it can focus way more than regular straight from the sun solar energy into a given area, and reflect that all down at your ground based solar PV arrays, you might get a nice gain on power? Bonus if you get enough gain that you can then pull thermal energy off the panels as well, and get some free heating for your greenhouses or what-have-you. If something goes wrong with the collector, it's not deadly (like a mis-aimed microwave power station) and just means you're gonna be on power rations .

It would not work during dust storms. Non concentrating solar on the surface does work during dust storms, just loses some efficiency.
Title: Re: Power options for a Mars settlement
Post by: sdsds on 09/08/2016 06:45 am
[Th]ink
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 09/08/2016 12:34 pm
If I haven't used up my miracle allotment, I was thinking along the line of nuclear in orbit as the power supply.  Not landing the nuclear eliminates several problems and provides some advantages.  Maybe not early in settlement but seems like it would be an interesting option as you scale.
Absolutely no point in that. Nuclear would actually weigh just as much in orbit if not more, EVEN given Mars' greater distance from the sun. Better off saving your money and using solar instead.

For the surface, nuclear does look attractive. (Near) immunity to dust storms (dust can still affect radiators, though not as bad). And you now have atmosphere or the ground to dump heat into instead of just vacuum. And the waste heat may even be useful.

My guess is a Mars settlement will probably use a hybrid of solar and nuclear on the ground, unless political or technological constraints make just solar the better choice.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 09/08/2016 08:19 pm
My guess is a Mars settlement will probably use a hybrid of solar and nuclear on the ground, unless political or technological constraints make just solar the better choice.

Good, very likely to be correct, guess, IMO.
Title: Re: Power options for a Mars settlement
Post by: biosehnsucht on 09/09/2016 07:56 am

It would not work during dust storms. Non concentrating solar on the surface does work during dust storms, just loses some efficiency.

Good point... how bad can they get? With such thin atmosphere I have a hard time believing you could approach 100% loss of light (the dust has to float / get pushed around by something), so perhaps you see a reduction but being still 24/7 might help reduce the impact vs regular solar only.

Of course, I never expect such a scheme to happen... :D
Title: Re: Power options for a Mars settlement
Post by: Impaler on 09/11/2016 12:28 am
Small thought, would a series of pipes in the ground similar to a geothermal heat pump system be a better means to dump heat from a nuclear reactor on mars surface.  The regolith of mars would have plenty of thermal mass and because it is far denser it's got more thermal conductivity then the atmosphere.

Because heat is being dumped continually and you want to allow the ground to release this heat as much as possible the cooling channels should be relatively shallow, maybe just a foot or two down, the temperature should be consistently below freezing and probably -30 C as that's the year round average for the martian equator.  If your power source is nuclear and you don' care about solar then being closer to the poles would give a lower average soil temperature too and mean the heat rejection levels won't change over the summer/winter cycle as they would with an air based radiator.

If over several years the area of the radiator field starts to warm up too much then a shallowly buried system of flexible hosing could conceivably be pulled up and redeployed to a new area using a simple chisel type cable trenching tool.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 09/11/2016 04:38 am

It would not work during dust storms. Non concentrating solar on the surface does work during dust storms, just loses some efficiency.

Good point... how bad can they get? With such thin atmosphere I have a hard time believing you could approach 100% loss of light (the dust has to float / get pushed around by something), so perhaps you see a reduction but being still 24/7 might help reduce the impact vs regular solar only.

I honestly have no idea how big the loss could be. But the dust scatters more than it attenuates. The spot illuminated would become much larger. So assume it becomes 3 times larger the energy received would drop by 90%.

However if you have really huge solar panels for a very large, like a circle of several km diameter and you have several independently steerable mirrors it may still work. You concentrate all your solar energy to the center of the array and the dust scatters it over the whole array.

Note, that the numbers I used are arbitrary, just to illustrate the concept. Someone would have to do the measurements and do the math.
Title: Re: Power options for a Mars settlement
Post by: biosehnsucht on 09/12/2016 11:31 pm

It would not work during dust storms. Non concentrating solar on the surface does work during dust storms, just loses some efficiency.

Good point... how bad can they get? With such thin atmosphere I have a hard time believing you could approach 100% loss of light (the dust has to float / get pushed around by something), so perhaps you see a reduction but being still 24/7 might help reduce the impact vs regular solar only.

I honestly have no idea how big the loss could be. But the dust scatters more than it attenuates. The spot illuminated would become much larger. So assume it becomes 3 times larger the energy received would drop by 90%.

However if you have really huge solar panels for a very large, like a circle of several km diameter and you have several independently steerable mirrors it may still work. You concentrate all your solar energy to the center of the array and the dust scatters it over the whole array.

Note, that the numbers I used are arbitrary, just to illustrate the concept. Someone would have to do the measurements and do the math.

That would actually be pretty clever, using multiple mirrors to normally light up the whole solar array, then compensate when there's atmospheric issues by adjusting the aim of them and let the atmosphere scatter the light... you'd still lose efficiency I assume since some portion of the light will scatter in non-useful directions, but it wouldn't be as bad. Plus multiple mirrors means redundancy (just hope the reason you lost one doesn't take out the rest due to Kessler syndrome)
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/14/2017 05:15 pm
Bump - in an interview Tom Mueller said they can start with solar, but see fission as the real solution.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 05/14/2017 05:57 pm
He mentioned NASA's small 10kWe development reactor, Kilopower. If it can be used in groups and is scalable...

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012354.pdf

Quote
The Evolvable Mars Campaign has found that Kilopower systems can be used in multiples to address human surface missions as an alternative to a large single power plant

§ Smaller unit size and mass permits easier packaging in surface landers

§ Multiple units provide a greater level of redundancy and fault tolerance

§ Units can be deployed as needed in timeline for flexibility in buildup approach

§ Human missions can benefit from first user’s establishment of nuclear infrastructure (material handling, testing, safeguards) and launch approval process.
Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/14/2017 06:17 pm
It would disintegrate into sub critical parts - once the range safety officer presses the trigger, or upon a high speed impact - and spread some low enriched Uranium around on the sea bed.
You might like to check the enrichment levels in space nuclear systems.

The ones that have been fielded or study are well into the HEU range IE 20%+, usually around 90%+ U235
Quote
As long as the reactor hasn't been operating, there would be no fission products and hence no radioactive danger.
Uranium and Plutonium are highly toxic without being radioactive.

I think their oxides in ceramic form are not chemically reactive. Basically, you can lick an UO2 pellet and have no ill effects.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/14/2017 06:53 pm
Most space reactor designs nowadays are trying to use LEU and avoid HEU. Performance is hit, but this should help certain aspects and reduce political exposure.

I listened to the interview and did not hear kilopower mentioned.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/14/2017 07:33 pm
The quote, btw:

Quote
To get one ship back, you need about eight football fields worth of solar cells on Mars. And you have to keep the dust off them. Um; so that’s tricky. It’s much better to use nuclear, fission reactor, it gets, you know, more compact; you actually get more; you get more power out per pound of reactor than you do out of solar cells, so it’s more mass-efficient. So if you’re taking it to Mars, it’s more efficient to ship reactors than it is to ship solar; it’s just that nobody’s really developed a space reactor yet.

Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 05/15/2017 02:05 am
If I was Musk, I would invest in some of the nuclear fusion concepts out there. Most can get to proof of concept with 10 to 20 million (and not all in one year). Compared to the cost of developing ITS, that is peanuts. Some of the fusion concepts currently desperately looking for funding could act as both a power source and a high ISP space drive.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/15/2017 02:14 am
If I was Musk, I would invest in some of the nuclear fusion concepts out there. Most can get to proof of concept with 10 to 20 million (and not all in one year). Compared to the cost of developing ITS, that is peanuts. Some of the fusion concepts currently desperately looking for funding could act as both a power source and a high ISP space drive.
Musk didn't get where he was by being easily taken in by outlandish physics claims. And the more conventional fusion approaches are heavier than fission, at least for reasonable investments.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 05/15/2017 02:38 am
Musk didn't get where he was by being easily taken in by outlandish physics claims. And the more conventional fusion approaches are heavier than fission, at least for reasonable investments.
PPPL's P-FRC. I would not call their claims "outlandish" at all. It has combined propulsion and power production uses. There are a few others that I would not call "outlandish" either. Something like Uri Shumlak's FUZE can be developed to proof of concept for a few million and that would be extremely compact and lightweight. FUZE is currently funded through ARPA-E, but I am not sure for how long.
And it could be argued that Musk absolutely is where is, because he is taking risks.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 05/15/2017 04:36 am
Musk didn't get where he was by being easily taken in by outlandish physics claims. And the more conventional fusion approaches are heavier than fission, at least for reasonable investments.
PPPL's P-FRC. I would not call their claims "outlandish" at all. It has combined propulsion and power production uses. There are a few others that I would not call "outlandish" either. Something like Uri Shumlak's FUZE can be developed to proof of concept for a few million and that would be extremely compact and lightweight. FUZE is currently funded through ARPA-E, but I am not sure for how long.
And it could be argued that Musk absolutely is where is, because he is taking risks.
Elon waited till Tesla and SpaceX were stable and performing on track to launch the Boring Company and Neurallink. lets let these two get up to speed before we start demanding he solve fusion power or antimatter prodiction problems.
Title: Re: Power options for a Mars settlement
Post by: Zed_Noir on 05/15/2017 05:02 am
Most space reactor designs nowadays are trying to use LEU and avoid HEU. Performance is hit, but this should help certain aspects and reduce political exposure.

I listened to the interview and did not hear kilopower mentioned.

Near the end of the Q&A after Mueller's monologue. In the response to the first question from part 5 of the Reddit thread transcript (https://www.reddit.com/r/spacex/comments/6b043z/tom_mueller_interview_speech_skype_call_02_may/dhiygzm/) from the Mueller Skype Reddit interview.

Quote from:  Reddit transcript
They’ve got a program called kilopower going that’s like, ten thousand watts, a 10 kilowatt reactor. We need a megawatt, but you know, you need to start somewhere.
Title: Re: Power options for a Mars settlement
Post by: GWH on 05/15/2017 05:10 am
The quote, btw:

Quote
To get one ship back, you need about eight football fields worth of solar cells on Mars. And you have to keep the dust off them. Um; so that’s tricky. It’s much better to use nuclear, fission reactor, it gets, you know, more compact; you actually get more; you get more power out per pound of reactor than you do out of solar cells, so it’s more mass-efficient. So if you’re taking it to Mars, it’s more efficient to ship reactors than it is to ship solar; it’s just that nobody’s really developed a space reactor yet.

The dust comment got me thinking about a recent study on making bricks out of Martian dust with its  high iron oxide content, and difficulties in collecting it. Seems like a serindpidous combo.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 05/15/2017 07:16 am
The dust comment got me thinking about a recent study on making bricks out of Martian dust with its  high iron oxide content, and difficulties in collecting it. Seems like a serindpidous combo.

I suspect that if you get enough dust from the PV collectors to make bricks from, you have a much more pressing problem.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/15/2017 07:18 am

Near the end of the Q&A after Mueller's monologue. In the response to the first question from part 5 of the Reddit thread transcript (https://www.reddit.com/r/spacex/comments/6b043z/tom_mueller_interview_speech_skype_call_02_may/dhiygzm/) from the Mueller Skype Reddit interview.

Quote from:  Reddit transcript
They’ve got a program called kilopower going that’s like, ten thousand watts, a 10 kilowatt reactor. We need a megawatt, but you know, you need to start somewhere.
A MW sized reactor was one of the few things I thought would need something the size of SLS to deliver.  However I see no sign of NASA funding such a unit.  :(

IIRC Kilopower has design options that allow it to scale up to 100Kw. But a key feature of it is its granularity. The reactor on NASA's DRM 5.0 architecture is IIRC the biggest single item to move. It sets the limit for the materials handling equipment you have to have on Mars. It also needed a 5Kw power source to start (mostly, I think, to melt the metal coolant)

Going to Kilopower means a unit that can be moved by hand (if still cold) and moved within a week of shut down (also by hand)

Kilopower is AFAIK still due to do a ground test by Dec 2017.
The dust comment got me thinking about a recent study on making bricks out of Martian dust with its  high iron oxide content, and difficulties in collecting it. Seems like a serindpidous combo.
Depends on wheather you're planning to just clean them and stockpile what you've collected or start the conversion to building materials.

Because the key task for initial PV array deployment is to run the ISRU propellant mfg plant.

Note when people say that diffusion due to dust lowers PV output "a bit" they mean to a level of 20% of full sunlight.

So to deliver a probable level of power output (as I'm not sure output cannot fall further) you're looking at an array at least 5x bigger than the baseline full Sun size.

Brick mfg might be an option if the propellant system is designed to with the full array at 20% illumination then at full illumination 80% of that power can be diverted to other tasks. If illumination falls then that will have to be reconsidered.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 05/15/2017 08:39 am
Elon waited till Tesla and SpaceX were stable and performing on track to launch the Boring Company and Neurallink. lets let these two get up to speed before we start demanding he solve fusion power or antimatter prodiction problems.
Who was talking antimatter production?!
They need power for mars and they need faster propulsion. Fusion could theoretically make both happen and Mueller himself mentioned fusion n the last interview. So it is not completely out there. Fission reactors have regulatory problems that could be very hard to overcome for a private company.
Title: Re: Power options for a Mars settlement
Post by: Hauerg on 05/15/2017 09:22 am
Elon waited till Tesla and SpaceX were stable and performing on track to launch the Boring Company and Neurallink. lets let these two get up to speed before we start demanding he solve fusion power or antimatter prodiction problems.
Who was talking antimatter production?!
They need power for mars and they need faster propulsion. Fusion could theoretically make both happen and Mueller himself mentioned fusion n the last interview. So it is not completely out there. Fission reactors have regulatory problems that could be very hard to overcome for a private company.
Tom himself mentioned antimatter. But for sure not for a near future by any standards.
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/15/2017 01:26 pm

Near the end of the Q&A after Mueller's monologue. In the response to the first question from part 5 of the Reddit thread transcript (https://www.reddit.com/r/spacex/comments/6b043z/tom_mueller_interview_speech_skype_call_02_may/dhiygzm/) from the Mueller Skype Reddit interview.

Quote from:  Reddit transcript
They’ve got a program called kilopower going that’s like, ten thousand watts, a 10 kilowatt reactor. We need a megawatt, but you know, you need to start somewhere.
A MW sized reactor was one of the few things I thought would need something the size of SLS to deliver.  However I see no sign of NASA funding such a unit.  :(

IIRC Kilopower has design options that allow it to scale up to 100Kw. But a key feature of it is its granularity. The reactor on NASA's DRM 5.0 architecture is IIRC the biggest single item to move. It sets the limit for the materials handling equipment you have to have on Mars. It also needed a 5Kw power source to start (mostly, I think, to melt the metal coolant)
...

Kilopower is a couple orders of magnitude too small.  Should start with megawatts or tens of megawatts.
High power density, simplicity, and long life (decades) is possible if the US Navy's submarine reactor is the model; these start at tens of MW -- could be scaled down(there was a 1MW reactor built for a research vessel) -- but also are able to operate at any power, from barely critical to full, and respond to changing demand naturally (without human or computer intervention).  They are designed to be essentially closed cycle (except for the cooling mechanism) and compatible with nearby human habitation.  Been there, done that.  Closed loop cooling is possible if 'waste' heat is used for thermal control of settlement and agricultural facilities. 

Bottom line:
Don't start from a reactor designed for space... because these will only be transported through space and will operate on land.

Title: Re: Power options for a Mars settlement
Post by: GWH on 05/15/2017 04:00 pm
I suspect that if you get enough dust from the PV collectors to make bricks from, you have a much more pressing problem.
Intentional or not this was an amazing pun. 

The bricks in this study only need to be compressed, rather than say cooking in a kiln: https://www.theverge.com/2017/4/27/15436154/mars-soil-simulant-study-building-human-missions

Brick mfg might be an option if the propellant system is designed to with the full array at 20% illumination then at full illumination 80% of that power can be diverted to other tasks. If illumination falls then that will have to be reconsidered.

I wouldn't suggest using the thin film PV surface as the primary dust collection surface, the solar arrays should be laid out in such a way that any air moving across them would be doing so at a higher velocity than ambient, and as such dust should actively be removed rather than collected. This would be accomplished just by the shape of the "panels".  I''m picturing these being laid out like a semi hemispherical or triangular profile "tents".

That shape that allows for air passing over to increase in velocity would also create corresponding velocity drops where dust would want to fall out and collect, picture the backside of a snow drift or sand dune.  So if the panels rolled out featured small air dam lip or trough where the dust could collect, this could then be robotically harvested.

8 football fields is 42,810m2, if the thin film array "tents" featured a 3m wide PV surface that results in a 14,270m length of PV. 
A 100x10mm collection trough filled to the brim over that length has a total volume of 14.27m3, not allowing for compaction that is the equivalent of 13,900 standard 3 5/8x2 1/4x8" sized bricks. Enough to build a 10' tall x 170' (~3m x 52m) wall if wall building was something one wanted to do on Mars.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 05/15/2017 04:34 pm

Near the end of the Q&A after Mueller's monologue. In the response to the first question from part 5 of the Reddit thread transcript (https://www.reddit.com/r/spacex/comments/6b043z/tom_mueller_interview_speech_skype_call_02_may/dhiygzm/) from the Mueller Skype Reddit interview.

Quote from:  Reddit transcript
They’ve got a program called kilopower going that’s like, ten thousand watts, a 10 kilowatt reactor. We need a megawatt, but you know, you need to start somewhere.
A MW sized reactor was one of the few things I thought would need something the size of SLS to deliver.  However I see no sign of NASA funding such a unit.  :(

IIRC Kilopower has design options that allow it to scale up to 100Kw. But a key feature of it is its granularity. The reactor on NASA's DRM 5.0 architecture is IIRC the biggest single item to move. It sets the limit for the materials handling equipment you have to have on Mars. It also needed a 5Kw power source to start (mostly, I think, to melt the metal coolant)
...

Kilopower is a couple orders of magnitude too small.  Should start with megawatts or tens of megawatts.
High power density, simplicity, and long life (decades) is possible if the US Navy's submarine reactor is the model; these start at tens of MW -- could be scaled down(there was a 1MW reactor built for a research vessel) -- but also are able to operate at any power, from barely critical to full, and respond to changing demand naturally (without human or computer intervention).  They are designed to be essentially closed cycle (except for the cooling mechanism) and compatible with nearby human habitation.  Been there, done that.  Closed loop cooling is possible if 'waste' heat is used for thermal control of settlement and agricultural facilities. 

Bottom line:
Don't start from a reactor designed for space... because these will only be transported through space and will operate on land.

Any unclassified info on the mass of a 1 MW or nMW  Navy reactor? 
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 05/15/2017 05:08 pm
IIRC back in the 1960's there was a program to develop nuclear merchant ships, which was cancelled. The GE air cooled reactor for it was 66 MW thermal. The compartment dimensions. & weight were about 15'w x 30' h, massing a bit over 300 tons.
Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/15/2017 05:09 pm
You may notice worldwide... there are NO reactors in a desert environment... (dry)

Most, if not all, are near a natural or man made heat sink (open water) OR have HUGE cooling towers...
There are a few with powered air cooling worldwide... not many...

That said...
You all realize that a major power plant (producing electricity)... has to have some way to cool itself to make it work...
You all are talking Reactors and the heating side... But the cooling side is just as critical...

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???

THAT is the riddle that needs solved... if you want to make MW of power on Mars...   :P 
Title: Re: Power options for a Mars settlement
Post by: Port on 05/15/2017 05:11 pm

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???


you use the ground as a heat-sink ;) much better conductivity than air, much higher thermal capacity, usually sub-zero temperature (higher thermal differential than air)

you could, depending on the location, also use a glacier, making a shit-big lake in the process (and lots of CO2 which you would want to capture)

it's actually pretty easy, quintessencial is: mars itself is a freaking snowball for all intents and purposes right now it doesn't matter where you dump the heat but some portion of it would likely be needed as process-heat for other chemical reactions, residency heating, warm water and so on and so on - since all the heat is used rather than "dumped" it's actually not lowering the efficiency of the reactor when the temperature or pressure differential is lower because of it, sure you get less electricity but more energy overall is used rather than wasted
Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/15/2017 05:18 pm

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???


you use the ground as a heat-sink ;) much better conductivity than air, much higher thermal capacity, usually sub-zero temperature (higher thermal differential than air)

you could, depending on the location, also use a glacier, making a shit-big lake in the process (and lots of CO2 which you would want to capture)

it's actually pretty easy, quintessencial is: mars itself is a freaking snowball for all intents and purposes right now

We are talking BILLIONS of BTU's per day need to go somewhere and "disappear"...
ALL the methods you list above have limits how much they can dissipate long term...
And all sound like major construction projects... with much resources to haul in from Earth...
Just saying...  ;)
Title: Re: Power options for a Mars settlement
Post by: spacenut on 05/15/2017 05:21 pm
I remember reading somewhere, that Russia developed a 20 ton nuclear power system for space.  If they still have this technology, maybe SpaceX can get Russia to launch it and pick it up on the way to Mars for a backup and night time power supply to continuously make liquid oxygen and liquid methane.  Mars is cold, so cooling the reactor may not be a problem.  Cooling can be as simple as melting the ice for water breakdown.  A small thorium reactor could be made also, to avoid long term radioactivity and bomb making in space. 
Title: Re: Power options for a Mars settlement
Post by: Port on 05/15/2017 05:22 pm

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???


you use the ground as a heat-sink ;) much better conductivity than air, much higher thermal capacity, usually sub-zero temperature (higher thermal differential than air)

you could, depending on the location, also use a glacier, making a shit-big lake in the process (and lots of CO2 which you would want to capture)

it's actually pretty easy, quintessencial is: mars itself is a freaking snowball for all intents and purposes right now

We are talking BILLIONS of BTU's per day need to go somewhere and "disappear"...
ALL the methods you list above have limits how much they can dissipate long term...
Just saying...  ;)

you don't get the dimensions we're talking about. the outer shell of mars has an average temperature of -40°C something or lower while being basically stone. the surface itself delivers a huge radiative cooling effect, it's going to be no problem at all

even if you would warm mars up in the process, congratulations you just helped terraform mars ;)
Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/15/2017 05:31 pm

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???


you use the ground as a heat-sink ;) much better conductivity than air, much higher thermal capacity, usually sub-zero temperature (higher thermal differential than air)

you could, depending on the location, also use a glacier, making a shit-big lake in the process (and lots of CO2 which you would want to capture)

it's actually pretty easy, quintessencial is: mars itself is a freaking snowball for all intents and purposes right now

We are talking BILLIONS of BTU's per day need to go somewhere and "disappear"...
ALL the methods you list above have limits how much they can dissipate long term...
Just saying...  ;)

you don't get the dimensions we're talking about. the outer shell of mars has an average temperature of -40°C something or lower while being basically stone. the surface itself delivers a huge radiative cooling effect, it's going to be no problem at all

even if you would warm mars up in the process, congratulations you just helped terraform mars ;)

Final point I will make... today... in this thread...
Please keep the end to end system in mind when "internet designing" a MW class nuclear power plant for Mars.
Heat source...Power Generation...Cooling sink...
And the Logistics to put ALL THREE in place and installed on Mars...  :-\
The first two may it fit in a container or two... But that cooling System will not...  ;)
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/15/2017 05:50 pm
Naval Reactors do seem ideal for a Mars Settlement but specs are hard to come by.  I wonder if they even make a Naval Reactor on the smaller end.  They seem to be pretty large.

For comparison though, some information on Commercial Modular Designs (https://en.wikipedia.org/wiki/Small_modular_reactor#Reactor_designs) with one Hyperion Power Module rating out at 70MWt/25MWe for 50 tons.
Title: Re: Power options for a Mars settlement
Post by: RonM on 05/15/2017 06:02 pm
IIRC back in the 1960's there was a program to develop nuclear merchant ships, which was cancelled. The GE air cooled reactor for it was 66 MW thermal. The compartment dimensions. & weight were about 15'w x 30' h, massing a bit over 300 tons.

NS Savannah was in operation from 1962 to 1972 and had a 74 MW reactor.

https://en.wikipedia.org/wiki/NS_Savannah

Here's some detailed specifications on the reactor.

https://maritime.org/tour/savannah/press/part2b.htm

Quote
The estimated gross weight of the power plant is as follows:
Propulsion system   1,265   short tons
Reactor system   665   short tons
Containment and shielding   2,418   short tons
Total   4,348   short tons

The operating period between each refueling of the core is expected to be about 3.5 years. All other structural and mechanical features of the plant are being designed for the normal life of a merchant ship, in excess of 20 years.

The key number here is 665 short tons (603 metric tonnes) for the reactor. Set it far enough away from the colony and shielding can be a minimum.

Also the fuel rods need to be replaced every 3.5 years.
Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/15/2017 06:12 pm
I wouldn't suggest using the thin film PV surface as the primary dust collection surface, the solar arrays should be laid out in such a way that any air moving across them would be doing so at a higher velocity than ambient, and as such dust should actively be removed rather than collected. This would be accomplished just by the shape of the "panels".  I''m picturing these being laid out like a semi hemispherical or triangular profile "tents".

That shape that allows for air passing over to increase in velocity would also create corresponding velocity drops where dust would want to fall out and collect, picture the backside of a snow drift or sand dune.  So if the panels rolled out featured small air dam lip or trough where the dust could collect, this could then be robotically harvested.

How about just making the tilt variable? Once in a week, turn them 90 degrees vertical (or more) and almost all dust falls off. No robots required. Just some electric motors.
Title: Re: Power options for a Mars settlement
Post by: GWH on 05/15/2017 06:49 pm
I wouldn't suggest using the thin film PV surface as the primary dust collection surface, the solar arrays should be laid out in such a way that any air moving across them would be doing so at a higher velocity than ambient, and as such dust should actively be removed rather than collected. This would be accomplished just by the shape of the "panels".  I''m picturing these being laid out like a semi hemispherical or triangular profile "tents".

That shape that allows for air passing over to increase in velocity would also create corresponding velocity drops where dust would want to fall out and collect, picture the backside of a snow drift or sand dune.  So if the panels rolled out featured small air dam lip or trough where the dust could collect, this could then be robotically harvested.

How about just making the tilt variable? Once in a week, turn them 90 degrees vertical (or more) and almost all dust falls off. No robots required. Just some electric motors.

Think of the thin film panels like a blanket, at least the length of a football field long.  To tilt them you would need to either hold it extremely taut from two ends and twist at both ends, or have considerable structure that can be rigid enough to transmit the torque over long distances - OR have just lots and lots of little motors and actuators.

I would picture these panels rolling out as a sheet from a coil, with lightweight stringers (like a rod) that can the used to  give the panels some shape by fastening them together (picture setting up a camping tent) and then weigh everything down with regolith to a flap sewn on to the bottom across the strut tying the stringers together. Very light wight materials, not easily moved once deployed. 

See the Mega Roll Out Solar Array for an example: http://www.dss-space.com/press.html
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 05/15/2017 07:26 pm
Think of the thin film panels like a blanket, at least the length of a football field long.  To tilt them you would need to either hold it extremely taut from two ends and twist at both ends, or have considerable structure that can be rigid enough to transmit the torque over long distances - OR have just lots and lots of little motors and actuators.
Probably cheaper to put some slack in the film and have a little vehicle that slowly shuttles from one end to the other of each strip, tilting/shaking/brushing as it goes.

Conceptually like one of these: https://en.wikipedia.org/wiki/Barrier_transfer_machine

Title: Re: Power options for a Mars settlement
Post by: GWH on 05/15/2017 07:32 pm
Think of the thin film panels like a blanket, at least the length of a football field long.  To tilt them you would need to either hold it extremely taut from two ends and twist at both ends, or have considerable structure that can be rigid enough to transmit the torque over long distances - OR have just lots and lots of little motors and actuators.
Probably cheaper to put some slack in the film and have a little vehicle that slowly shuttles from one end to the other of each strip, tilting/shaking/brushing as it goes.

Conceptually like one of these: https://en.wikipedia.org/wiki/Barrier_transfer_machine

Sure.  Either shake it out and try and pick it up or scoop/suck it out from a little gutter that is built in.

Point is with that much surface area, the dust could go from a problem that needs to be solved to a resource that can be actively harvested to build construction materials.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 05/15/2017 08:27 pm

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???


you use the ground as a heat-sink ;) much better conductivity than air, much higher thermal capacity, usually sub-zero temperature (higher thermal differential than air)

you could, depending on the location, also use a glacier, making a shit-big lake in the process (and lots of CO2 which you would want to capture)

it's actually pretty easy, quintessencial is: mars itself is a freaking snowball for all intents and purposes right now

We are talking BILLIONS of BTU's per day need to go somewhere and "disappear"...
ALL the methods you list above have limits how much they can dissipate long term...
Just saying...  ;)

you don't get the dimensions we're talking about. the outer shell of mars has an average temperature of -40°C something or lower while being basically stone. the surface itself delivers a huge radiative cooling effect, it's going to be no problem at all

even if you would warm mars up in the process, congratulations you just helped terraform mars ;)

Final point I will make... today... in this thread...
Please keep the end to end system in mind when "internet designing" a MW class nuclear power plant for Mars.
Heat source...Power Generation...Cooling sink...
And the Logistics to put ALL THREE in place and installed on Mars...  :-\
The first two may it fit in a container or two... But that cooling System will not...  ;)

I suspect that the cooling system for the power plant will look an awful lot like a heating system for something else.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/15/2017 09:49 pm
IIRC back in the 1960's there was a program to develop nuclear merchant ships, which was cancelled. The GE air cooled reactor for it was 66 MW thermal. The compartment dimensions. & weight were about 15'w x 30' h, massing a bit over 300 tons.
That's pretty important since this is a Low Enriched Uranium system. It's also important if SX does not want to be stuck with the huge bill for developing a new nuclear reactor power system.
Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???

THAT is the riddle that needs solved... if you want to make MW of power on Mars...   :P 

True. However the situation on Mars would be a bit different from Earth. Mars is energy poor. What is "waste" heat on Earth is likely to be used for something on Mars, rather than just dumping it to the environment. Using "waste heat" to melt a glacier would be an excellent piece of synergy for example. Likewise heating human waste storage management for anaerobic digestion for gas or power generation.

While it's true Mar's atmosphere is about 1/160 that of SL pressure that does not mean it's a vacuum. IIRC the ISS radiators are about 47W/M^2. I would expect Mars to be orders of magnitude better. IIRC the radiators on a nuclear powered aircraft carrier are about 200 tonnes. Then again that's a much bigger reactor than the size SX would need. 

Reaction Engines estimated they could reduce the radiator mass of a nuclear aircraft carrier to about 2 tonnes. However that is with an Earth heat sink. So better, but still quite heavy.


you use the ground as a heat-sink ;) much better conductivity than air, much higher thermal capacity, usually sub-zero temperature (higher thermal differential than air)

you could, depending on the location, also use a glacier, making a shit-big lake in the process (and lots of CO2 which you would want to capture)

it's actually pretty easy, quintessencial is: mars itself is a freaking snowball for all intents and purposes right now

We are talking BILLIONS of BTU's per day need to go somewhere and "disappear"...
ALL the methods you list above have limits how much they can dissipate long term...
Just saying...  ;)

you don't get the dimensions we're talking about. the outer shell of mars has an average temperature of -40°C something or lower while being basically stone. the surface itself delivers a huge radiative cooling effect, it's going to be no problem at all

even if you would warm mars up in the process, congratulations you just helped terraform mars ;)
Actually something like this is done on Earth with abandoned oil wells, where a low BP liquid is injected in one, harvested from another and used to drive a turbine. The driver is the Earth's geothermal heat.

Typically these generate (and by inference can absorb) about 500Kw. So that 74MW(t) of the Savannah reactor (assuming it's 40% efficient) needs to dump about 44MW into the ground. So that's 88 wells. [EDIT at around 2-4 000 feet deep, although I think more toward the 4000 ft mark.]

But note these wells are linked by highly cracked rock strata. On Mars you'd probably only have the surface excavated by the drill bits into the surface, a much smaller surface area to dissipate heat.

[EDIT so using a civilian naval reactor design you'll be needing to drill 88 (or 176 if they are operating in pairs) wells, each several 1000 feet deep, frack the rock between them and run pipes to and from them for hot and cold coolant. But you can't use the reactor itself except at fairly low power (presumably enough to run the drilling rig) because it's got nowhere it can dump that heat to fast enough (that's what you're building).  Even an experienced drilling team is not enough because no one's experienced in drilling Mars, with or without a pressure suit.  :(   

The glacier idea makes a lot more sense but now you've got to either keep the water sealed in its hole to get anywhere like 100c before it boils (NASA say Mars surface pressure will have fresh water boiling at 10c. Since you're probably extracting the water for propellant mfg you'll need to find some way to keep the radiator pipes in contact with the glacier for maximum cooling as they melt it. Also quite challenging. ] 

The joker in the pack is that when you have fluids you have convection, which can transfer a hot of heat efficiently. Coupled with water (which has an astonishingly high heat capacity given it's molecular weight) you can dump a lot of heat easily.

While rock does have greater density than water that does not guarantee greater heat capacity and its ability to absorb heat will depend on its diffusivity.   You end up with a layer of hot (well warmish) rocks around the piping. In time that heat will diffuse outward but in the meantime where will the heat from the reactor go?
Title: Power options for a Mars settlement
Post by: kaoru on 05/16/2017 02:15 am
Not to throw fuel on the fire but what about a Molten Salt Reactor (MSR) on a Thorium fuel cycle?  Thorium is plentiful here on earth, don't know about mars though.  The research at Oakridge was for developing a reactor for the USAF (aka power a bomber).  MSR has a lot of safety features (can't melt down; low pressure, etc.) and you only need to bring Uranium 238? as the starting fuel.  Suffice to say that MSR can be made small and safe with high power...  The only issues is the metallurgy needed for the plumbing/heat exchanger to stop corrosion/wearing.  Something that rocket engines have in common.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/16/2017 02:23 am
Except the features that thorium gives you are not the ones you really care about.


A LEU (20% U235) reactor makes the most sense, IMHO.

In particular, I have in mind a surface reactor that's like a jet turbine version of an NTR, using the Martian atmosphere (compressed and cleaned of dust by shaft power driven by a downstream turbine) instead of hydrogen and driving a turbine (hooked to a generator) instead of generating thrust. That way, you could get a specific power of about 40 times that of a conventional surface reactor. And you could still use low enriched Uranium (LEU) as even some newer NTR designs use it.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/16/2017 06:43 am
You may notice worldwide... there are NO reactors in a desert environment... (dry)

Most, if not all, are near a natural or man made heat sink (open water) OR have HUGE cooling towers...
There are a few with powered air cooling worldwide... not many...

That said...
You all realize that a major power plant (producing electricity)... has to have some way to cool itself to make it work...
You all are talking Reactors and the heating side... But the cooling side is just as critical...

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???

THAT is the riddle that needs solved... if you want to make MW of power on Mars...    

Some answers:
1: Some of the ISRU processes need a lot of heat
2: subsurface ice deposits
3: the colony needs heat
4: forced convection still works
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/16/2017 11:18 am
Not to throw fuel on the fire but what about a Molten Salt Reactor (MSR) on a Thorium fuel cycle?  Thorium is plentiful here on earth, don't know about mars though.  The research at Oakridge was for developing a reactor for the USAF (aka power a bomber).  MSR has a lot of safety features (can't melt down; low pressure, etc.) and you only need to bring Uranium 238? as the starting fuel.  Suffice to say that MSR can be made small and safe with high power...  The only issues is the metallurgy needed for the plumbing/heat exchanger to stop corrosion/wearing.  Something that rocket engines have in common.
The concept was for the NPB but AFAIK Oak Ridge never got anywhere near that in terms of system weight. I'd also guess part of that is that military and space reactors have historically been Highly Enriched Uranium (that's how you can get such tiny cores, by commercial PWR standards). A flight weight reactor would have been much more enriched.
A LEU (20% U235) reactor makes the most sense, IMHO.

In particular, I have in mind a surface reactor that's like a jet turbine version of an NTR, using the Martian atmosphere (compressed and cleaned of dust by shaft power driven by a downstream turbine) instead of hydrogen and driving a turbine (hooked to a generator) instead of generating thrust. That way, you could get a specific power of about 40 times that of a conventional surface reactor. And you could still use low enriched Uranium (LEU) as even some newer NTR designs use it.
So let's see.

1) New gas cooled reactor design
2) CO2 driven gas turbine (if you're thinking of a supercritical CO2 turbine for size that's about 74 bar or  roughly 11686 Martian atmospheres. That's a pretty big job of gas handling.
3) High speed direct coupled generator or pretty big gearbox (1MW(e) output will need maybe 1.12MW of shaft input, about 1500Hp.

People have been saying ITS will cost a few $Bn to develop but you've just put a shed load of very complex hardware (which SX has zero experience in developing) in the exploration path.

BTW given Mars thin atmosphere significant sized meteorites can reach the ground with substantial KE. While a Black Swan event the consequences of a hit on such a power plant would be very severe.  Single big power systems create single point failure.

I think the odds on bet is the first power system will be PV, but once on the surface SX will move to establish a 2nd system that gives settlers at least some freedom from relying exclusively on the Sun. Biogas, geothermal and larger units of the Kilopower system all seem plausible to me.

I'd remind people this is a settlement, not an outpost. Evacuation back to Earth is not a good way to deal with failure and (if settlement plans are fulfilled) 2nd or more generation inhabitants may not be able to ever return to Earth.  :(
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/16/2017 01:35 pm
You may notice worldwide... there are NO reactors in a desert environment... (dry)

Most, if not all, are near a natural or man made heat sink (open water) OR have HUGE cooling towers...
There are a few with powered air cooling worldwide... not many...

That said...
You all realize that a major power plant (producing electricity)... has to have some way to cool itself to make it work...
You all are talking Reactors and the heating side... But the cooling side is just as critical...

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???

THAT is the riddle that needs solved... if you want to make MW of power on Mars...   :P 


Actually, some of us do realize these things.  In a former couple of careers, I built and operated nuclear power plants from a few tens of MW(thermal) to several GigaWatts(thermal).  Deserts on Earth are not the same as Mars.

'Waste' heat is a precious commodity on Mars; it is one of the most essential parts of ECLSS.

Communities could be heated in same way as done using geothermal heating in Iceland... providing a perfect heat sink for the reactor.
Quote
Geothermal systems tend to benefit from economies of scale, so space heating power is often distributed to multiple buildings, sometimes whole communities. This technique, long practiced throughout the world in locations such as Reykjavík, Iceland,[5] Boise, Idaho,[6] and Klamath Falls, Oregon[7] is known as district heating
https://en.wikipedia.org/wiki/Geothermal_heating

Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/16/2017 01:42 pm
You may notice worldwide... there are NO reactors in a desert environment... (dry)

Most, if not all, are near a natural or man made heat sink (open water) OR have HUGE cooling towers...
There are a few with powered air cooling worldwide... not many...

That said...
You all realize that a major power plant (producing electricity)... has to have some way to cool itself to make it work...
You all are talking Reactors and the heating side... But the cooling side is just as critical...

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???

THAT is the riddle that needs solved... if you want to make MW of power on Mars...    

Some answers:
1: Some of the ISRU processes need a lot of heat
2: subsurface ice deposits
3: the colony needs heat
4: forced convection still works

1)... ok, true that... what if it's down?... not soaking up the waste heat?
2)... yikes!... big deal to get up and running... not bad once going...
3)... ok, true that... but load is variable
4)... ok, agree in principle... but atmosphere has low mass to pass heat into...

You will have to curtail electric power generation if you cooling system can't soak it up...
And that #4 cooling system will not be small in size and mass IF needs to handle MW full power generation...
Plus, forced air is not used much on earth... because the fans eat a lot of the power plants output up...

I agree though... doable but not easy... major project for just one plant install and operation...  :-\

@ AncientU...
You posted while I was typing the above... thanks for your point of view on topic...
Just have concerns of having to throttle back power output to match cooling sink size at times...
But, I agree... It's doable...
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/16/2017 01:59 pm
Like all ECLSS systems (and reactor systems -- they have an incredible amount in common) a huge amount of redundancy will be needed.  Even 'passive' cooling mechanisms on Earth like cooling towers require redundancy in pumps to lift water to be cooled to high in the tower where it is sprayed into the updraft.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/16/2017 02:16 pm
You may notice worldwide... there are NO reactors in a desert environment... (dry)

Most, if not all, are near a natural or man made heat sink (open water) OR have HUGE cooling towers...
There are a few with powered air cooling worldwide... not many...

That said...
You all realize that a major power plant (producing electricity)... has to have some way to cool itself to make it work...
You all are talking Reactors and the heating side... But the cooling side is just as critical...

Now... How will COOLING that Reactor work in the dry thin atmosphere of Mars??  ???

THAT is the riddle that needs solved... if you want to make MW of power on Mars...    

Some answers:
1: Some of the ISRU processes need a lot of heat
2: subsurface ice deposits
3: the colony needs heat
4: forced convection still works

1)... ok, true that... what if it's down?... not soaking up the waste heat?
2)... yikes!... big deal to get up and running... not bad once going...
3)... ok, true that... but load is variable
4)... ok, agree in principle... but atmosphere has low mass to pass heat into...

You will have to curtail electric power generation if you cooling system can't soak it up...
And that #4 cooling system will not be small in size and mass IF needs to handle MW full power generation...
Plus, forced air is not used much on earth... because the fans eat a lot of the power plants output up...

I agree though... doable but not easy... major project for just one plant install and operation...  :-\

@ AncientU...
You posted while I was typing the above... thanks for your point of view on topic...
Just have concerns of having to throttle back power output to match cooling sink size at times...
But, I agree... It's doable...
True about throttling..

A colony is a giant process plant, one that also supports love as a by product.

Process plants are difficult and sometimes fail in unpleasant ways.

Nobody said it'd be easy...

Title: Re: Power options for a Mars settlement
Post by: TrevorMonty on 05/16/2017 02:24 pm
See 1st Feb podcast on mars reactors.

http://spirit.as.utexas.edu/~fiso/archivelist.htm

Beaming power from 17000km Areostationary orbit is another option. Laser while not very efficient would be best to start with as only needs simple and lite solar arrays for surface reception. A large SSP can make its own way from LEO to ASO using SEP.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 05/16/2017 02:26 pm
A LEU (20% U235) reactor makes the most sense, IMHO.

In particular, I have in mind a surface reactor that's like a jet turbine version of an NTR, using the Martian atmosphere (compressed and cleaned of dust by shaft power driven by a downstream turbine) instead of hydrogen and driving a turbine (hooked to a generator) instead of generating thrust. That way, you could get a specific power of about 40 times that of a conventional surface reactor. And you could still use low enriched Uranium (LEU) as even some newer NTR designs use it.
So let's see.

1) New gas cooled reactor design
2) CO2 driven gas turbine (if you're thinking of a supercritical CO2 turbine for size that's about 74 bar or  roughly 11686 Martian atmospheres. That's a pretty big job of gas handling.
3) High speed direct coupled generator or pretty big gearbox (1MW(e) output will need maybe 1.12MW of shaft input, about 1500Hp.
...

Why use supercritical CO2? Jets don't use supercritical air.
Title: Re: Power options for a Mars settlement
Post by: Hyperion5 on 05/17/2017 01:29 am
Not to throw fuel on the fire but what about a Molten Salt Reactor (MSR) on a Thorium fuel cycle?  Thorium is plentiful here on earth, don't know about mars though.  The research at Oakridge was for developing a reactor for the USAF (aka power a bomber).  MSR has a lot of safety features (can't melt down; low pressure, etc.) and you only need to bring Uranium 238? as the starting fuel.  Suffice to say that MSR can be made small and safe with high power...  The only issues is the metallurgy needed for the plumbing/heat exchanger to stop corrosion/wearing.  Something that rocket engines have in common.

I believe Clongton would be giving you a big thumbs up if he saw this.  Given the Thorium reserves found on Mars, he was of the opinion that a Thorium-fueled MSR would be by far the best choice. 
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/17/2017 02:22 am
There is thorium on Mars? I thought Mars was deficient in both uranium and thorium compared to Earth.
Title: Re: Power options for a Mars settlement
Post by: QuantumG on 05/17/2017 02:33 am
I'm guessing this the source https://mars.jpl.nasa.gov/odyssey/gallery/latestimages/PIA04257.html

Doesn't seem very promising.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/17/2017 03:21 am
Not to throw fuel on the fire but what about a Molten Salt Reactor (MSR) on a Thorium fuel cycle?  Thorium is plentiful here on earth, don't know about mars though.  The research at Oakridge was for developing a reactor for the USAF (aka power a bomber).  MSR has a lot of safety features (can't melt down; low pressure, etc.) and you only need to bring Uranium 238? as the starting fuel.  Suffice to say that MSR can be made small and safe with high power...  The only issues is the metallurgy needed for the plumbing/heat exchanger to stop corrosion/wearing.  Something that rocket engines have in common.
The concept was for the NPB but AFAIK Oak Ridge never got anywhere near that in terms of system weight. I'd also guess part of that is that military and space reactors have historically been Highly Enriched Uranium (that's how you can get such tiny cores, by commercial PWR standards). A flight weight reactor would have been much more enriched.
A LEU (20% U235) reactor makes the most sense, IMHO.

In particular, I have in mind a surface reactor that's like a jet turbine version of an NTR, using the Martian atmosphere (compressed and cleaned of dust by shaft power driven by a downstream turbine) instead of hydrogen and driving a turbine (hooked to a generator) instead of generating thrust. That way, you could get a specific power of about 40 times that of a conventional surface reactor. And you could still use low enriched Uranium (LEU) as even some newer NTR designs use it.
So let's see.

1) New gas cooled reactor design
2) CO2 driven gas turbine (if you're thinking of a supercritical CO2 turbine for size that's about 74 bar or  roughly 11686 Martian atmospheres. That's a pretty big job of gas handling.
3) High speed direct coupled generator or pretty big gearbox (1MW(e) output will need maybe 1.12MW of shaft input, about 1500Hp.

People have been saying ITS will cost a few $Bn to develop but you've just put a shed load of very complex hardware (which SX has zero experience in developing) in the exploration path.

BTW given Mars thin atmosphere significant sized meteorites can reach the ground with substantial KE. While a Black Swan event the consequences of a hit on such a power plant would be very severe.  Single big power systems create single point failure.

I think the odds on bet is the first power system will be PV, but once on the surface SX will move to establish a 2nd system that gives settlers at least some freedom from relying exclusively on the Sun. Biogas, geothermal and larger units of the Kilopower system all seem plausible to me.

I'd remind people this is a settlement, not an outpost. Evacuation back to Earth is not a good way to deal with failure and (if settlement plans are fulfilled) 2nd or more generation inhabitants may not be able to ever return to Earth.  :(


I'm not expecting SpaceX to fund this reactor. I'm just pointing out something that'd be significantly better than other Mars power sources on a specific power basis. On the order of 400W/kg for what I'm suggesting vs 4W/kg for kilopower. You could land a 100MWe reactor using a single ITS this way, enough for a huge settlement. Probably want a bunch of them (like 10?) for redundancy and for a larger city. In addition to solar power (just bring the cells from Earth, the rest is manufactured on Mars).

With kilopower-like specific power (or similar nuclear reactor tech, like the larger but heavier 40kWe reactors), it takes a full ITS load to bring enough power to power the ISRU equipment to launch that ITS back to Earth every 2 years (solar+storage actually is more powerful for the same mass, even on Mars). With this jet turbine nuclear reactor concept, you improve that by a factor of 100.

Part of the reason I'm proposing this is that I really like the insanity of NTR cores. Gigawatts in just a few tons! But I think NTR is mostly over-rated (although 30 day transits is one of the rare instances where NTR combined with extreme aerobraking is enabling... Usually it's just cheaper to launch more propellant). So in this case, you take advantage of that crazy specific power. NASA is starting to invest in NTR tech again, and this would be a good use for it.


Basically, this thing (MANGLE, Mars Aerial Nuclear Global Landing Explorer) except just the reactor sitting on the ground spinning a generator and probably makes sense to modify it for LEU so it's cheaper:
http://www6.miami.edu/acfdlab/publications/AIAA-2014-3820.pdf
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/17/2017 01:29 pm
Why use supercritical CO2? Jets don't use supercritical air.
Historically CO2 gas cooled reactors have operated at high pressure and temperature. GEC have done SC CO2 turbine design work. They are small, but complex.

Gases are not very dense. So you need a lot of them to transfer the amount of heat we're talking about. There are few teams with CO2 turbine design experience. That's one of the costs of the system you're proposing.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/17/2017 01:32 pm
Why use supercritical CO2? Jets don't use supercritical air.
Historically CO2 gas cooled reactors have operated at high pressure and temperature. GEC have done SC CO2 turbine design work. They are small, but complex.

Gases are not very dense. So you need a lot of them to transfer the amount of heat we're talking about. There are few teams with CO2 turbine design experience. That's one of the costs of the system you're proposing.
Please read this report. The concept doesn't use supercritical CO2: http://www6.miami.edu/acfdlab/publications/AIAA-2014-3820.pdf
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/17/2017 02:05 pm
I'm not expecting SpaceX to fund this reactor. I'm just pointing out something that'd be significantly better than other Mars power sources on a specific power basis. On the order of 400W/kg for what I'm suggesting vs 4W/kg for kilopower.
This is a design derived from MITEE. You might like to look up what happened to such proposed designs and how feasible people think they are IRL.

True. However 4W/Kg in a test unit (Kilopower will be tested this Dec) beats 400w/Kg on a sheet of paper.  :(
Quote from: Robotbeat
With this jet turbine nuclear reactor concept, you improve that by a factor of 100.
If you're not expecting SX to fund this and NASA certainly won't who do you expect to fund it?
Quote from: Robotbeat
Part of the reason I'm proposing this is that I really like the insanity of NTR cores. Gigawatts in just a few tons! But I think NTR is mostly over-rated (although 30 day transits is one of the rare instances where NTR combined with extreme aerobraking is enabling... Usually it's just cheaper to launch more propellant). So in this case, you take advantage of that crazy specific power. NASA is starting to invest in NTR tech again, and this would be a good use for it.
AFAIK the properties of CO2 and H2 are very different and I think NASA is still baselining H2 as the propellant for any NTR it's looking at.
Quote from: Robotbeat
Basically, this thing (MANGLE, Mars Aerial Nuclear Global Landing Explorer) except just the reactor sitting on the ground spinning a generator and probably makes sense to modify it for LEU so it's cheaper:
http://www6.miami.edu/acfdlab/publications/AIAA-2014-3820.pdf
It's very unlikely the USG would release HEU to a private business. They've spent very significant effort in eliminating the use of HEU anywhere in civilian systems (quite a lot of civilian research reactors at universities were fueled with HEU).  :(

The attraction with nuclear is that you don't need enormous over capacity (like PV arrays) to cope with dust storms if you want to maintain a launch schedule and it can run at night. BTW Kilopower can scale up to at least 100Kw. Currently an RTG (the only US nuclear power system flying) is $240m each. They hope their 1-10Kw unit will be delivered for about 60% of that, about $144m.

SX has demonstrated the benefits of standardizing and clustering to deliver capability. A settlement will need a lot of power, depending on numbers (various studies have put power needs between 5 and 60Kw/person/day, at the top end that's 60MW for a 1000 people) and a lot of that will need to be reliable, not shut down due to a sand storm unless Mars remains a place where only highly trained staff can be expected to cope.
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/17/2017 02:39 pm
...

The attraction with nuclear is that you don't need enormous over capacity (like PV arrays) to cope with dust storms if you want to maintain a launch schedule and it can run at night. BTW Kilopower can scale up to at least 100Kw. Currently an RTG (the only US nuclear power system flying) is $240m each. They hope their 1-10Kw unit will be delivered for about 60% of that, about $144m.
...

Don't start with a space reactor concept!!!

Assuming 60MW for 1000 people (upthread), and $14.4M/kW, that's $864B for electrical power (alone).
No one can afford a reading lamp if it is designed with this economic model.
Title: Re: Power options for a Mars settlement
Post by: RonM on 05/17/2017 03:30 pm
Quote from: Robotbeat
Basically, this thing (MANGLE, Mars Aerial Nuclear Global Landing Explorer) except just the reactor sitting on the ground spinning a generator and probably makes sense to modify it for LEU so it's cheaper:
http://www6.miami.edu/acfdlab/publications/AIAA-2014-3820.pdf
It's very unlikely the USG would release HEU to a private business. They've spent very significant effort in eliminating the use of HEU anywhere in civilian systems (quite a lot of civilian research reactors at universities were fueled with HEU).  :(

It would definitely have to be redesigned to use LEU, like conventional fission power plants. The 93% U-235 mentioned in the paper is weapons grade material.

Outside the box thinking like this design is what a Mars colony would need. Conventional nuclear power is too massive. The reactor and turbine on the NS Savannah was about 600 tons without shielding. That's for 74 MW. It would also need more cooling systems to function on Mars. I assume there are more modern designs, but there probably hasn't been much effort to reduce mass.

https://forum.nasaspaceflight.com/index.php?topic=39785.msg1678499#msg1678499

A combination of solar and nuclear would be the best, saving money on the reactor capacity. Have enough nuclear capability for a minimum baseline power during dust storms and use solar for the rest.
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/17/2017 04:16 pm
Naive question- just how far away is Mars-manufactured solar likely to be?
Semiconductors might be to much of a leap, but what about solar thermal? AFAIK you mostly just need Si and Al and ability to produce these to a reasonable level of purity. Even if the clever turbine bits had to be imported, you could build acres of mirror from native materials.
Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/17/2017 04:30 pm
Solar thermal in cold places does NOT work well... too much heat loss... Been there, seen that...  ;)
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/17/2017 04:39 pm
Solar thermal in cold places does NOT work well... too much heat loss... Been there, seen that...  ;)

Would be interesting to know why that is. Intuitively you would think that you have the same energy per square metre available as for PV.
Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/17/2017 05:11 pm
Solar thermal in cold places does NOT work well... too much heat loss... Been there, seen that...  ;)

Would be interesting to know why that is. Intuitively you would think that you have the same energy per square metre available as for PV.

Yes.. same energy is striking the absorbing surface... agree on that point...
But the surrounding atmosphere and cold surfaces within line of sight to the same surface act as cold sinks and draw off the heat you just collected...

Solar thermal (for water heating) was tried in the US upper Midwest and was a colossal failure...
In the winter time, even on bright sunny days... the heat loss thru the glazing in both IR and heat was almost as much as the gain... the water barely gets warm in the collector...
As cold as Mars is... I have a feeling Solar Thermal will suffer the same issue on Mars...  :-\

The current best practice in the upper Midwest... is just put in PV solar and run some low voltage elements in the hot water preheat tanks off the battery bank (using a load diversion controller once the battery banks are full)
This negates the heat loss issue... You get Hot water even on a very cold winter day...  ;)
In fact...PV works better when it's cold... More voltage at same amps=more watts...
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/17/2017 06:00 pm
On the other hand, Mars is near-vacuum so there will be less heat lost passing through the atmosphere.
Also, on Earth you are trying to heat water up to say 60 degrees for domestic use, and your starting point varies depending on your location/climate.
But on Mars you are merely trying to create a temperature difference to drive a turbine. Can you not simply have everything working at a lower temperature? What matters is the energy input.
I could be totally wrong thinking that this could be made to work. But the relative simplicity of ISRU-sourced mirrors must be a big bonus.
Don't forget that the whole point of this is to create a self reliant colony, not one which is wholly dependent on imports from Earth. And whilst eventually I would hope to see the manufacturing base for semiconductors established on Mars, mirrors sure sound easier, at least in the early days.
Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/17/2017 07:34 pm
While I have seen write-ups on concentrator thermal solar setups... driving Stirling motors w/alternators  mounted on tracking mounts...
The cost was such... that if you took that same $$$$$ and bought flat PV... put them on simple fixed (or seasonal tilt) mounts... and walked away... Your KWH yield per year was more with PV...

Nope... Solar thermal is dead to me...  :P
PV panels (at todays prices) rule as far as Solar to electric conversion...  ;)
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/17/2017 07:56 pm
Solar PV will clearly be the better option, as soon as someone opens a solar panel shop on Mars :D
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/17/2017 08:01 pm

It would definitely have to be redesigned to use LEU, like conventional fission power plants. The 93% U-235 mentioned in the paper is weapons grade material.

Outside the box thinking like this design is what a Mars colony would need. Conventional nuclear power is too massive. The reactor and turbine on the NS Savannah was about 600 tons without shielding. That's for 74 MW. It would also need more cooling systems to function on Mars. I assume there are more modern designs, but there probably hasn't been much effort to reduce mass.

https://forum.nasaspaceflight.com/index.php?topic=39785.msg1678499#msg1678499

A combination of solar and nuclear would be the best, saving money on the reactor capacity. Have enough nuclear capability for a minimum baseline power during dust storms and use solar for the rest.
That would be one option. Another would be the geothermal energy route, but that is more limited.

The trouble with nuclear is the limited starter options. The current space nuclear systems are quite small (and expensive in $/Kw terms) while the marine systems are too big for a starter settlement and are (by space standards) damm heavy.  :(
On the other hand, Mars is near-vacuum so there will be less heat lost passing through the atmosphere.
Also, on Earth you are trying to heat water up to say 60 degrees for domestic use, and your starting point varies depending on your location/climate.
But on Mars you are merely trying to create a temperature difference to drive a turbine. Can you not simply have everything working at a lower temperature? What matters is the energy input.
As with geothermal the trick is to find a liquid that will boil over an appropriate temperature range and design a turbine (or Stirling system) to run from it.
[quote author=Kaputnik}
I could be totally wrong thinking that this could be made to work. But the relative simplicity of ISRU-sourced mirrors must be a big bonus.
Don't forget that the whole point of this is to create a self reliant colony, not one which is wholly dependent on imports from Earth. And whilst eventually I would hope to see the manufacturing base for semiconductors established on Mars, mirrors sure sound easier, at least in the early days.
[/quote]
Something to keep in mind. The usual argument against is dust makes concentrator systems much less effective than ones using just ambient light.

I'll also note that outside the domestic solar heating systems one option has been to use linear collectors of oil filled glass tubes inside a vacuum tube, ensuring that heat is retained in the liquid.
Title: Re: Power options for a Mars settlement
Post by: M.E.T. on 05/17/2017 08:17 pm
Someone mentioned two football fields of solar panels to generate the power for one ISRU ITS refuelling over a 2 year period. But is this really a challenge once a few cargo flights have landed?

How much does a square metre sized solar panel weigh? 10kg? One dedicated cargo flight can deliver 200 tons of payload to Mars. A dedicated solar panel delivery could then give you 20,000 square metres of solar panels, by my calculation.


What stops them from eventually having a square mile of solar panels, or 10 square miles, or however much they need. If there is one thing Mars has plenty of, its empty space for solar panels.
Title: Re: Power options for a Mars settlement
Post by: John Alan on 05/17/2017 08:19 pm
I'll also note that outside the domestic solar heating systems one option has been to use linear collectors of oil filled glass tubes inside a vacuum tube, ensuring that heat is retained in the liquid.

I've seen that... Seemed a bit fragile to put out in the US Midwest weather (Hail happens here)...

However... I liked the idea of using oil as the fluid in the collectors...
A nice off the shelf 0W-20 synthetic motor oil would be nice I think.
Will not freeze or flash boil at Earth like temps... 

But... then again I ran the cost numbers... and PV wins in payback time... on Earth anyway...  ;)
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/17/2017 11:59 pm
So, what you bring to Mars is the facility to fabricate solar cells/panels. 
Then set up shop and sell them to Kaputnik
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/18/2017 12:06 am
So, what you bring to Mars is the facility to fabricate solar cells/panels. 
Then set up shop and sell them to Kaputnik
Solar cells can be made so thin that a single ITS could land Gigawatts of cells. And, if you're concentrating the sunlight using Mars-made concentrators, hundreds of Gigawatts or even a Terawatt worth of cells per ITS payload.

So there's no real reason you would need an actual solar cell manufacturing plant on Mars except complete independence.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/18/2017 08:11 am
Solar cells on Mars can be very different to panels used on earth. Rain, snow, hailstorms, tornados are rare on Mars and don't need to be calculated in the design.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/18/2017 08:23 am
So, what you bring to Mars is the facility to fabricate solar cells/panels. 
Then set up shop and sell them to Kaputnik
Solar cells can be made so thin that a single ITS could land Gigawatts of cells. And, if you're concentrating the sunlight using Mars-made concentrators, hundreds of Gigawatts or even a Terawatt worth of cells per ITS payload.

So there's no real reason you would need an actual solar cell manufacturing plant on Mars except complete independence.
Isn't that sort of the point of setting up a Martian settlement?

It just occurred to me that a Martian solar farm would likely look very different from an Earth one. Metal production is highly energy intensive.

Imagine 2 suitably aligned (Martian) brick walls of different height with the PV panel attached between them to give an averagely good solar output, much like the PV arrays on houses on Earth. 
Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/18/2017 08:41 am
So, what you bring to Mars is the facility to fabricate solar cells/panels. 
Then set up shop and sell them to Kaputnik
Solar cells can be made so thin that a single ITS could land Gigawatts of cells. And, if you're concentrating the sunlight using Mars-made concentrators, hundreds of Gigawatts or even a Terawatt worth of cells per ITS payload.

So there's no real reason you would need an actual solar cell manufacturing plant on Mars except complete independence.
Isn't that sort of the point of setting up a Martian settlement?

It just occurred to me that a Martian solar farm would likely look very different from an Earth one. Metal production is highly energy intensive.

Imagine 2 suitably aligned (Martian) brick walls of different height with the PV panel attached between them to give an averagely good solar output, much like the PV arrays on houses on Earth.

Mars colony needs to make metals anyway, it's impractical to completely get rid of them.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/18/2017 10:28 am

Imagine 2 suitably aligned (Martian) brick walls of different height with the PV panel attached between them to give an averagely good solar output, much like the PV arrays on houses on Earth.

Probably easier to find a suitable inclined area or use a rove to make inclined rows for placement of solar sheets on the ground. Use a cleaning rover that dusts it off using a broom or I think just lift it up somewhat and apply a gentle shaking to get the dust off.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/18/2017 11:59 am
A single axis tracker on Mars would work very well, especially near the equator. Since it tilts each day, dust falls off and never appreciably accumulates.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 05/18/2017 01:27 pm

Imagine 2 suitably aligned (Martian) brick walls of different height with the PV panel attached between them to give an averagely good solar output, much like the PV arrays on houses on Earth.

Probably easier to find a suitable inclined area or use a rove to make inclined rows for placement of solar sheets on the ground. Use a cleaning rover that dusts it off using a broom or I think just lift it up somewhat and apply a gentle shaking to get the dust off.

Or an blower driven by electric motor. If the atmosphere is thick enough for wind to blow dust, it's thick enough for a blower to blow dust.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/18/2017 02:08 pm
Or an blower driven by electric motor. If the atmosphere is thick enough for wind to blow dust, it's thick enough for a blower to blow dust.

I am a little bit worried it may just blow the dust to the next panel.
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/18/2017 02:33 pm
Or an blower driven by electric motor. If the atmosphere is thick enough for wind to blow dust, it's thick enough for a blower to blow dust.

I am a little bit worried it may just blow the dust to the next panel.

If it's a tracking array, then you need to have space between each row of panel- the greater the gap, the wider range of angles they can work on.
But maybe Robotbeat's idea of hoping the dust will just fall off by itself will be sufficient.

And, hey, sending people out there with an EMU and a broom could be a useful minor punishment for petty crimes... I mean this place is going to need a law and order system after all :D
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/18/2017 06:29 pm
Mars colony needs to make metals anyway, it's impractical to completely get rid of them.
Reduce, not eliminate.  :(

If you look at solar farms you see most of them use steel supports for their PV arrays or mirrors. I think settlers will have to look much more carefully at the use of metals for structural support applications.

I think Martian bricks (or Marscrete) will be adequate for a surprising number of tasks. I'd like to see the cells made on Mars as well but we'll see.

Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/18/2017 07:22 pm
I'm compelled to believe that beyond bootstrapping the colonization effort and prior to full ISRU independence from Earth, that one of the most critical factors is easy setup and low-maintenance.  If that is as critical as it feels to me then I don't see how big solar farms play a big role except as residual assets post-bootstrap or other incidental applications.

Does this sound logical or am I missing something?

I know nuclear isn't trivial but I've seen lots and lots of design-work already invested in modular nuclear (http://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx).  The Tom Meuller interview and Elon's success leads me to think their approach and mindset could solve almost any problem that physics doesn't preclude.

Naively perhaps, with all this investment I'm surprised that there isn't further progress toward working examples.  Is it beyond reason to develop in the appropriate timeframes a self-contained modular nuclear package that could plug into the martian grid to obviate the requirement of large solar farms post-bootstrap?  Am I really stretching to believe the same could serve as a pluggable "energy pack" for large logistics equipment like material handling, regolith-moving, and tunnel-boring?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/18/2017 10:21 pm
Mars colony needs to make metals anyway, it's impractical to completely get rid of them.
Reduce, not eliminate.  :(

If you look at solar farms you see most of them use steel supports for their PV arrays or mirrors. I think settlers will have to look much more carefully at the use of metals for structural support applications.

I think Martian bricks (or Marscrete) will be adequate for a surprising number of tasks. I'd like to see the cells made on Mars as well but we'll see.
Meteoric iron is plentiful on Mars. Already refined and just sitting there on the surface waiting for settlers to pick it up and cast it.
Title: Re: Power options for a Mars settlement
Post by: montyrmanley on 05/18/2017 10:35 pm
Mars colony needs to make metals anyway, it's impractical to completely get rid of them.
Reduce, not eliminate.  :(

If you look at solar farms you see most of them use steel supports for their PV arrays or mirrors. I think settlers will have to look much more carefully at the use of metals for structural support applications.

I think Martian bricks (or Marscrete) will be adequate for a surprising number of tasks. I'd like to see the cells made on Mars as well but we'll see.
Meteoric iron is plentiful on Mars. Already refined and just sitting there on the surface waiting for settlers to pick it up and cast it.

Iron oxide. Mars is full up of it. It's the "red planet" for a reason. Problem is, it takes energy to separate all that iron oxide into usable oxygen and iron, and if that separation can't be done in an effcient and cost-effective way, it may not matter. It's kind of like desalinating ocean water on earth to make it drinkable: it's only done more or less as a last resort when no other sources of potable water are available because of the inefficient and energy-intensive desalination process.

We really need to invest a lot of money into shrinking and "containerizing" fission reactors. And not just for Mars, but for earthbound uses as well.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/18/2017 11:27 pm
I'm pretty sure I said meteoric iron, not iron oxide (when is even more plentiful). Did I mistype??

Let me go back and check to make sure I said meteoric iron...

...Meteoric iron...
Yup! Looks like meteoric iron is what I said, not iron oxide.
Title: Re: Power options for a Mars settlement
Post by: Stan-1967 on 05/18/2017 11:47 pm

Meteoric iron is plentiful on Mars. Already refined and just sitting there on the surface waiting for settlers to pick it up and cast it.

Meteoric iron could be very useful for simple structural needs.  I think it might be preferable to bring along a furnace to melt meteoric Ni:Fe , & make metal powders out of it vs. casting.  Metal powders could be used laser sintering in 3-D additive processes, which would enable greater complexity & more flexibility in what could be made.

I also have an interest in trying to figure out how to use martian resources like perchlorates, sulfates, & nitrates to  be used in electrochemical process for refining metal oxides or digesting & purifying metals through electrowining or precipitation. 

Both pathways are power intensive.   Making metal powders is probably the best initial path.   

Title: Re: Power options for a Mars settlement
Post by: BobHk on 05/19/2017 01:25 am
There is a solution to most dust build up on the surface of solar panels:

http://www.tandfonline.com/doi/abs/10.1080/02726350601146341

Mashing the martian soil into lego bricks to build habitats with is already theoretically possible:

https://www.theverge.com/2017/4/27/15436154/mars-soil-simulant-study-building-human-missions

Quote
After working with the material for a while, the engineers found that just adding the right amount of pressure was enough to form the soil into tiny, stiff blocks — stronger than steel-reinforced concrete.

SO you bring a machine with you that mashes soils into building blocks and set up the solar panels with native materials holding them up off the ground, integrate them into shelters as roof tiles also as the panels anti dust tech could be used to keep them from getting buried.

No iron smelting/melting needed.

If we import polymers they can be used to 3dprint essential tools and support struts that cant be made with compacted dusts.

http://www.inquisitr.com/4147743/do-it-yourself-mars-colony-3d-printer-would-use-mars-dust-to-make-tools-building-materials/

Native metals would be best used with sinter printing, allowing the 3d printing of tools that uses a minimal amount of the native meteoric iron material and gives maximal strength for the design. 

I'm a fan of amerecium rtgs.  SpaceX could start landing them as red dragon like power pods as soon as retropropulsive landings are safe enough to trust a rtg on a drone landing mission near a prospective colony site. 

Once colonists land they could hook up to the rtg landers power and set up the colony.  How long can transmission lines be?  It doesnt have to be close and could probably be buried if you didnt want to maintenance the thing after its hooked up to colony power lines.  More than one rtg could be landed and daisy chained together as needed.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/19/2017 02:19 am
So, what you bring to Mars is the facility to fabricate solar cells/panels. 
Then set up shop and sell them to Kaputnik
Solar cells can be made so thin that a single ITS could land Gigawatts of cells. And, if you're concentrating the sunlight using Mars-made concentrators, hundreds of Gigawatts or even a Terawatt worth of cells per ITS payload.

So there's no real reason you would need an actual solar cell manufacturing plant on Mars except complete independence.

Tom Mueller directly contradicted this, by saying that Nuclear delivers more Watts per kg.

This is presumably after studying the matter.

The GWatts per ITS can only be achieved by taking the mass of in-space zero-g thin film systems such as the ATK product.  Those don't work in atmosphere, and don't have longevity on Mars.

Solar is an ok interim solution, if flown from Earth.

Mars-originated solar has a chance, but it has to be on vast scales, or else the energy put into solar panel production exceeds the energy it generates over its lifetime.  (and even if was "only" 50% of that energy, it'd still be problematic since you need to invest that energy upfront)

If those problems can be solved, then yes - you could use Mars-native solar.   But that's a very big if.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/19/2017 02:32 am
So, what you bring to Mars is the facility to fabricate solar cells/panels. 
Then set up shop and sell them to Kaputnik
Solar cells can be made so thin that a single ITS could land Gigawatts of cells. And, if you're concentrating the sunlight using Mars-made concentrators, hundreds of Gigawatts or even a Terawatt worth of cells per ITS payload.

So there's no real reason you would need an actual solar cell manufacturing plant on Mars except complete independence.

Tom Mueller directly contradicted this, by saying that Nuclear delivers more Watts per kg.

This is presumably after studying the matter.
I've also studied the matter and I disagree. He's perhaps the world's best liquid rocket engine engineer, but he's not the world-premier expert in everything. Also, please quote where he actually said what you're claiming to be a direct contradiction.

Quote
The GWatts per ITS can only be achieved by taking the mass of in-space zero-g thin film systems such as the ATK product.  Those don't work in atmosphere, and don't have longevity on Mars.
Sure they do. And anyway, making supporting material is way simpler than the cells themselves.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 05/19/2017 06:10 am
I dont think that dust on solar panels is a big issue. It can easily be mitigated, for example put the solar panels at least at a slight angle (you want to do that anyway to optimize the angle to the sun) and mount a small piezo element at the backside of the panel. When dust accumulates on the solar panels, vibrate the piezo element with a suitable frequency. Effectively the solar panel acts like a speaker membrane and the dust walks right off. No complicated cleaning machinery, just a few grams of piezo element and wires per solar panel.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/19/2017 09:55 am
We really need to invest a lot of money into shrinking and "containerizing" fission reactors. And not just for Mars, but for earthbound uses as well.
An idea that's been around for several decades.

Technically the PWR's were the closest to getting to serial production but they have issues. The main problems with all the proposed designs are they come from people looking to leverage their existing experience, none of which is ideal. Multiply that by a regulatory regime that takes no account of the size of the reactor and you need deep pockets to start with.

In terms of safety, ease of of construction cost and freedom from proliferation issues anywhere within the current experience base the ideal would be an unenriched (natural Uranium) thermal reactor using a 10%BiPb alloy, graphite moderator and natural circulation or heat pipes operating at around 540c.

Such a system eliminates the need for enriched Uranium and high pressure vessels (beyond  the dead weight of the lead, 10s, not 100s of atm) and operates at temperatures that allow conventional steam turbine (available down to the 100s of Kws) easily. russian experience suggest using Martensitic (AISI 400 series) rather than Austenitic (300 series) as they are more resistant to neutron damage and easier to weld. BTW I don't think anyone's tried FSW on such steels, but that would probably substantially reduce weld issues.

The 10%Bi results in temperatures low enough to freeze out Polonium without the coolant freezing, the biggest hazards of this type of system.

The (relatively) easy availability of enriched Uranium has been the quick fix for reactor designers but it's also the key issue around proliferation. People don't want to be dependent on others for supplies of enriched uranium but existing nuclear countries are nervous about supplying enrichment technology to new countries, fearing its use in nuclear weapons. Only a natural Uranium design completely eliminates that risk and gives control of supply to the client country without fear of proliferation.   

Needless to say no one has spent any significant time working on such a concept.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/19/2017 09:55 am


Meteoric iron could be very useful for simple structural needs.  I think it might be preferable to bring along a furnace to melt meteoric Ni:Fe , & make metal powders out of it vs. casting.  Metal powders could be used laser sintering in 3-D additive processes, which would enable greater complexity & more flexibility in what could be made.

I also have an interest in trying to figure out how to use martian resources like perchlorates, sulfates, & nitrates to  be used in electrochemical process for refining metal oxides or digesting & purifying metals through electrowining or precipitation. 

Both pathways are power intensive.   Making metal powders is probably the best initial path.
Yes that's the problem. Powders as an intermediate for different mfg routes sounds a good idea.

It's only when you try to replace coal, oil or natural gas you realize just how much energy Earth civilization uses.  Not in terms of operating but in mfg new stuff.

On Earth a 1GW power plant is a fairly typical sized unit. Using the worst case Martian energy budget (60Wk/person/day) that's 16 000 people, or say half that with the rest driving mfg systems. But given Mar's extra distance from the Sun (140 Vs 93 million miles)and thin film PV's (10-20% efficiency) that's maybe 85W/m^2 IE 1GW is close to 12 sq Km of PV cells. Or 5x that to allow for dust storms cutting off direct sunlight by 80% (or 100% at night).

Not impossible but it does give an idea of the scale of work you've got to do on Mars to give you the kind of power levels people take for granted from the grid on Earth.

Obviously I don't think that will be available immediately but that's the kind of scale that a solar only solution needs.

Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/19/2017 10:18 am
During the worst of bad sandstorms they can switch off energy intensive manufacturing. It is not like strong sandstorms are as frequent as cloud cover in most regions of the earth.
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/19/2017 01:14 pm
They'll also need copious battery banks for overnight/emergency use (e.g., severing cables from power generating facility(ies)) that can also accommodate dust storms to a great degree.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/19/2017 04:54 pm
They'll also need copious battery banks for overnight/emergency use (e.g., severing cables from power generating facility(ies)) that can also accommodate dust storms to a great degree.

Good insulation can help you retain heat and efficient lighting can be a minimal power drain but once you get into just cooking stuff your power needs go up.

It also turns out that growing plants in artificial light is very power hungry. You'd really want to grow them under sunlight, but of course if you have a month long sandstorm that will affect your PV array as well.

I'm not sure if it can generate enough energy but I think biogas will definitely be used.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/19/2017 09:16 pm
An idea that's been around for several decades.

Technically the PWR's were the closest to getting to serial production but they have issues. The main problems with all the proposed designs are they come from people looking to leverage their existing experience, none of which is ideal. Multiply that by a regulatory regime that takes no account of the size of the reactor and you need deep pockets to start with.

Needless to say no one has spent any significant time working on such a concept.  :(

I can think of someone that likes ambitious projects and could perhaps help with the regulatory stuff.  I also know someone else that likes to think big and could provide some invaluable guidance.  I can also think of a system that could economically dispose of the biggest problem if it can reliably abort during ascent and maintain payload integrity.

It seems to me like that time is right now for this Manhattan Project.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/20/2017 01:45 am
So, what you bring to Mars is the facility to fabricate solar cells/panels. 
Then set up shop and sell them to Kaputnik
Solar cells can be made so thin that a single ITS could land Gigawatts of cells. And, if you're concentrating the sunlight using Mars-made concentrators, hundreds of Gigawatts or even a Terawatt worth of cells per ITS payload.

So there's no real reason you would need an actual solar cell manufacturing plant on Mars except complete independence.

Tom Mueller directly contradicted this, by saying that Nuclear delivers more Watts per kg.

This is presumably after studying the matter.
I've also studied the matter and I disagree. He's perhaps the world's best liquid rocket engine engineer, but he's not the world-premier expert in everything. Also, please quote where he actually said what you're claiming to be a direct contradiction.

Quote
The GWatts per ITS can only be achieved by taking the mass of in-space zero-g thin film systems such as the ATK product.  Those don't work in atmosphere, and don't have longevity on Mars.
Sure they do. And anyway, making supporting material is way simpler than the cells themselves.

What he said is that they studied the matter, and Nuclear provides better power/mass than solar does.

He was not expressing the result of a study he did.  He explained what conclusion SpaceX arrived at, and I assume they also gave it some thought.

The reasons why de-facto solar is so different then spec-sheet solar have been explained upthread so many times...  I also spend some time "giving it thought", and am a solar advocate - when it makes sense.  Which is plenty of times.

But there are a number of reasons why it's a problematic solution for Mars.

Now, your point upthread was that "You can bring Solar from Earth, and that the ONLY reason to manufacture Solar on Mars is energy independence (for Mars).".   

But if you want energy independence, you need to fabricate the whole thing on Mars, and there's an energy balance problem there, since the scale is small.

I think Solar has a lot to offer for the early stage where you still can't set up nuclear.  Or for temporary remote installations.  And definitely for in-space applications.

You can't just waive off Mueller's conclusion so easily without actually showing a viable path forward with solar, one that addresses longevity, environmental issues starting with wind and dust, one that brings into account structure and not just the thin film, etc.

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/20/2017 01:58 am
Fission has longevity issues. I mean, almost all the problems solar has, fission also has (sometimes worse, sometimes not as bad). Even dust! Dust settling on radiators reduces their effectiveness. Fission requires refueling, and Mars is fissionable-poor.

I have, in fact, developed a very good lightweight solar solution which addresses wind and dust while also being extremely efficient structurally. I plan on proposing it sometime.

And it's not like conventional fission is super amazingly good. Kilopower is like 5-10W/kg, which is barely better than RTGs and not really any better than even conventional solar and batteries. And Kilopower is actually better than the previous nuclear reactor concept that was used. It's only designed for like a 12 year lifespan. In fact, I'd say relatively conventional solar outperforms near-term nuclear overall.

But I think something like Kilopower as an addition to solar makes a lot of sense to help smooth over interruptions of power from dust storms. It seems like it has reasonable development cost, and as long as NASA's contributing the reactor, the fuel is actually free (it comes from dismantled nuclear weapons stockpile and is actually free for space reactors).

I'd like to see the assumptions behind Mueller's numbers. Also, I want a DIRECT quote, not a paraphrase. It's also possible that Musk disagrees with Mueller. I CAN just handwave away your paraphrase of his opinion, and again, this is his opinion, a man who is a propulsion (not energy systems) expert.
Title: Re: Power options for a Mars settlement
Post by: drzerg on 05/20/2017 10:30 am
simple safe reactor for space applicaions.
https://www.youtube.com/watch?time_continue=14&v=KobRfGqlpGc

but you could easily modify it for mars use. just dig a deep hole some distance from base and put it in it with proper radiator. when its done after 10 years just leave it there for future recycling. yes some contamination will occur but it is small price and can be solved in the future when colony becomes self sustained.

such reactor active zone weights 35 kg and can produce up to 40kw heat energy for 10 y and with stirling engine 10kw electricity. uranium cost is $500K
Title: Re: Power options for a Mars settlement
Post by: M.E.T. on 05/20/2017 10:31 am
Isn't the problem with nuclear that basically it will be impossible to take a nuclear reactor to Mars given that governments (the US government in particular, in whose jurisdiction all SpaceX launchpads are located) won't allow it? Else we would have nuclear spaceships flying through the solar system already.

So basically, as advantageous as nuclear power is, it may never be allowed for political reasons, hence the need to focus on solar power, right?

Or are the regulations relating to fission power in space not as draconic as I perceive them to be?
Title: Re: Power options for a Mars settlement
Post by: QuantumG on 05/20/2017 10:34 am
Isn't the problem with nuclear that basically it will be impossible to take a nuclear reactor to Mars given that governments (the US government in particular, in whose jurisdiction all SpaceX launchpads are located) won't allow it?

No.

Quote
Else we would have nuclear spaceships flying through the solar system already.

There's many of them, they're called RTGs. The reason why there isn't space-based nuclear reactors is because the best ones ever developed were developed by Russia and they sucked anyway when compared to RTGs. In any case, we're talking about Mars-based power reactors, not nuclear power for spacecraft.
Title: Re: Power options for a Mars settlement
Post by: M.E.T. on 05/20/2017 10:41 am
Isn't the problem with nuclear that basically it will be impossible to take a nuclear reactor to Mars given that governments (the US government in particular, in whose jurisdiction all SpaceX launchpads are located) won't allow it?

No.

Quote
Else we would have nuclear spaceships flying through the solar system already.

There's many of them, they're called RTGs. The reason why there isn't space-based nuclear reactors is because the best ones ever developed were developed by Russia and they sucked anyway when compared to RTGs. In any case, we're talking about Mars-based power reactors, not nuclear power for spacecraft.

I'm aware of RTG's. But aren't they fairly small scale by comparison to a full size nuclear reactor? And  even then, I recall the controversy when Cassini was launched and the paranoia over the potential for a mishap.

As for distinguishing a Mars reactor from a space based reactor, I guess I need some help here. Would it not present the same risk during launch, irrespective of what the reactor's eventual destination is?
Title: Re: Power options for a Mars settlement
Post by: QuantumG on 05/20/2017 10:53 am
I'm aware of RTG's. But aren't they fairly small scale by comparison to a full size nuclear reactor? And  even then, I recall the controversy when Cassini was launched and the paranoia over the potential for a mishap.

There were idiots who said turning on the Large Hadron Collider would create a black hole that would swallow the Earth too, who cares? Cassini was still launched because people who actually understand the risks make decisions, not the ignorant public.

Title: Re: Power options for a Mars settlement
Post by: Oli on 05/20/2017 11:04 am
I'm aware of RTG's. But aren't they fairly small scale by comparison to a full size nuclear reactor?

To my knowledge launching an brand new inactive reactor is far less of an issue than launching RTGs.
Title: Re: Power options for a Mars settlement
Post by: M.E.T. on 05/20/2017 11:12 am
I'm aware of RTG's. But aren't they fairly small scale by comparison to a full size nuclear reactor?

To my knowledge launching an brand new inactive reactor is far less of an issue than launching RTGs.

Ok, that's good to know. I would love nuclear reactors on Mars. It broadens your energy options greatly. Especially in the early years, before large scale alternatives are available.

For some reason I was just under the impression that there were some regulations prohibiting it. If not, then great.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/20/2017 12:22 pm
I would love nuclear reactors on Mars. It broadens your energy options greatly. Especially in the early years, before large scale alternatives are available.

I agree, provided there are enough solar panels to survive if the reactor fails. I don't see 100% availability for a nuclear reactor. Maybe at least 3 of them can give some assurance to make a non nuclear fall back less urgent.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 05/20/2017 12:42 pm
No matter how efficient a nuclear solution would be, I think it has to have convincing and practical strategies for the following questions:
1. What do you do with the nuclear waste of a reactor?
2. How do you dispose a reactor after it is decommissioned?
3. Assuming there will be at least one reactor with a catastrophic failure of the containment vessel within the first 100 years of the colony, what effect does that have on the colony? And "it will not happen" is only an acceptable answer if it is physically impossible for the failure to happen.
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/20/2017 02:07 pm
No matter how efficient a nuclear solution would be, I think it has to have convincing and practical strategies for the following questions:
1. What do you do with the nuclear waste of a reactor?
It's a big, dead planet. This will be much less of an issue than on Earth. Store it away from sources of water ice.

Quote
2. How do you dispose a reactor after it is decommissioned?
If mobile, take it to a dumping area. If not, bury it.
We do this on Earth already- when the Kursk was raised, they left the reactor on the seabed because that was the safest thing to do.

Quote
3. Assuming there will be at least one reactor with a catastrophic failure of the containment vessel within the first 100 years of the colony, what effect does that have on the colony? And "it will not happen" is only an acceptable answer if it is physically impossible for the failure to happen.

A Mars colony will be much better insulated from the effects of a nuclear accident. It is hermetically sealed and nothing gets in or out without a lot of processing and screening. Given the higher level of background radiation, the colony will be pretty robust already in this regard.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/20/2017 04:59 pm
It's unlikely there will even be a containment vessel for early Mars reactors. Kilopower doesn't have one.
Title: Re: Power options for a Mars settlement
Post by: DOCinCT on 05/20/2017 06:31 pm
NASA Langley staff back in 2014 proposed using at least 3 115 kWe reactor systems weighing about 11-12 tons each for a small colony of 20 individuals.  This included an ISRU facility and greenhouses.
The reactors, following proposals in the DRM 5.0 Addendum 2 would be buried in a shallow (2m) pit using regolith as shielding. The design goal was less than 5 rem/year at a 100 m radius, or the minimum distance of a habitat.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/20/2017 06:41 pm
Yeah, and since then the Kilopower units have been the base assumption for power for the Evolvable Mars Campaign because they're lighter per unit power than those larger units.
Title: Re: Power options for a Mars settlement
Post by: DOCinCT on 05/20/2017 06:57 pm
Yeah, and since then the Kilopower units have been the base assumption for power for the Evolvable Mars Campaign because they're lighter per unit power than those larger units.
One paper I read "Kilowatt-Class Fission Power Systems for Science and
Human Precursor Missions" used an example of a 3 kWe system weighing 750kg  to provide 110 kWe you would need 36 systems weighing over 27,500kg or 30 tons; granted the weight power ratio gets better with scaling, but I think you are still looking at 10-12 tons per reactor.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/20/2017 07:04 pm
The Kilopwer systems are 1 ton for 10kWe, so easy to manage with a smallish rover and a winch.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/20/2017 07:07 pm
Isn't the problem with nuclear that basically it will be impossible to take a nuclear reactor to Mars given that governments (the US government in particular, in whose jurisdiction all SpaceX launchpads are located) won't allow it? Else we would have nuclear spaceships flying through the solar system already.

So basically, as advantageous as nuclear power is, it may never be allowed for political reasons, hence the need to focus on solar power, right?

Or are the regulations relating to fission power in space not as draconic as I perceive them to be?

No, the problem with nuclear power is that it isn't as good as solar power for in-space activities. Part of the issue is that no one has invested the billions to make a space reactor - and why would they when solar power is so good?

Nuclear does have advantages on planetary surfaces, and perhaps beyond Saturn. But no one is going to invest in it till there's a need.

For Mars by the way, a liquid sodium cooled reactor could be optimum.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/20/2017 09:17 pm
No matter how efficient a nuclear solution would be, I think it has to have convincing and practical strategies for the following questions:
1. What do you do with the nuclear waste of a reactor?
2. How do you dispose a reactor after it is decommissioned?
3. Assuming there will be at least one reactor with a catastrophic failure of the containment vessel within the first 100 years of the colony, what effect does that have on the colony? And "it will not happen" is only an acceptable answer if it is physically impossible for the failure to happen.

I am of the opinion that for practical reasons, the current politically correct avoidance of reality cannot continue and therefore there are certainties that we must move toward accepting.

Earth needs passively-safe modular nuclear power long term.
Earth needs a nuclear disposal plan.

ITS intends to put large amounts of mass in space at a low price.
I presume ITS will be able to achieve reliable abort during ascent maintaining the integrity of the payload.
I presume it's techinically possible to create a couple scales of passively-safe modular nuclear packages.

So my vision would be:

1)  Develop ITS to it's cost goals and payload safety
2)  Dispose of Earth's Nuclear Waste to Venus (or Mercury) ($100B's of revenue and comparable to current plans)
3)  Add Modular Nuclear to the SpaceX stable of Cashflows from Earth
4)  Create Modular Nuclear power-pack for Boring Machines and Other Heavy Equipment for siting issues


I feel modularity, reliability, plug-and-play, and low-maintenance are major drivers leading me this direction.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 05/20/2017 09:33 pm
Kaputnik, your answers handwave away real problems. That's not the idea.
To 1. and 2.: you can't just dump nuclear waste on the surface. Nuclear waste stays dangerous for millions of years. A colony on Mars is not the end goal, the goal is to terraform Mars which includes an active water cycle.

To 3.: that's not a solution either. I asked for a absolute solution, not a relative statement that it's better than on earth. That's irrelevant.

Also, I don't know how a reactor without a containment vessel works, but there must be some cooling cycle near the fuel and if that breaches nuclear fallout will be the result.
Title: Re: Power options for a Mars settlement
Post by: Torbjorn Larsson, OM on 05/20/2017 10:42 pm
Kaputnik, your answers handwave away real problems. That's not the idea.
To 1. and 2.: you can't just dump nuclear waste on the surface. Nuclear waste stays dangerous for millions of years. A colony on Mars is not the end goal, the goal is to terraform Mars which includes an active water cycle.

Of course you can just dump - or better, bury - old reactors on Mars. The surface environment is already dangerous, including cancerogenous (dust, oxidants). That there is an end goal besides a colony is not demonstrated, nor its feasibility.

And - millions of years!? Really? I glanced at a decay diagram, and typically the activity decreased 10^-3 every 10^3 years. So after shutdown the activity would presumably be in W rather than kW, and after 1000 year mW. Not much activity. Just don't go around kick the old reactors, and you will be fine, as long as you don't subject them to typical wind driven Mars weathering.

Also, I don't know how a reactor without a containment vessel works, but there must be some cooling cycle near the fuel and if that breaches nuclear fallout will be the result.

I looked over the Kilopower designs since SpaceX appears to invest in them because solar energy is likely impossible for their ramped up fuel production needs. Kilopower designs are without massive containment vessels as they are intended for space use, and thermally self regulating (if temperature increases due to reaction increases, the neutron multiplication factor goes down). The engine cooling from a working Stirling or Brayton engine as it generates electric power is rather a nuisance factor (slows down reactor stabilization) than a necessity, see the published data.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 05:36 am
Fission has longevity issues. I mean, almost all the problems solar has, fission also has (sometimes worse, sometimes not as bad). Even dust! Dust settling on radiators reduces their effectiveness. Fission requires refueling, and Mars is fissionable-poor.
...

I'd like to see the assumptions behind Mueller's numbers. Also, I want a DIRECT quote, not a paraphrase. It's also possible that Musk disagrees with Mueller. I CAN just handwave away your paraphrase of his opinion, and again, this is his opinion, a man who is a propulsion (not energy systems) expert.

The quote you're looking for, from the transcript, ans which I've quoted before:

Quote
If you try to do it with solar; it’s extremely difficult, but doable. To get one ship back, you need about eight football fields worth of solar cells on Mars. And you have to keep the dust off them. Um; so that’s tricky. It’s much better to use nuclear, fission reactor, it gets, you know, more compact; you actually get more; you get more power out per pound of reactor than you do out of solar cells, so it’s more mass-efficient. So if you’re taking it to Mars, it’s more efficient to ship reactors than it is to ship solar;

He was not presenting it as a result of some private research he did, but as a conclusion SpaceX arrived at.

As for dust on heat exchangers, do you really not understand the difference in power densities, and the difference in degradation as a function of dust load?

And that residual heat is actually useful for many chemical processes, for ice melting, etc?

Those are fundamentals that have been discussed above multiple times, and every time we circle back to the same starting point.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/21/2017 07:32 am
I looked over the Kilopower designs since SpaceX appears to invest in them because solar energy is likely impossible for their ramped up fuel production needs. Kilopower designs are without massive containment vessels as they are intended for space use, and thermally self regulating (if temperature increases due to reaction increases, the neutron multiplication factor goes down). The engine cooling from a working Stirling or Brayton engine as it generates electric power is rather a nuisance factor (slows down reactor stabilization) than a necessity, see the published data.
"The engine cooling from a working Stirling or Brayton engine as it generates electric power is rather a nuisance factor"
???
Kilopower's purpose is to generate electrical energy. NASA spent a lot of time and money to develop a system that's AFAP is as reliable as the thermoelectric elements in an RTG but about 4x more efficient. Stirling is that system.  It is also expected to be about 40% cheaper than an RTG (RTG's cost about $240m. They cannot be throttled up or down and their output falls from the moment they are constructed). 
For Mars by the way, a liquid sodium cooled reactor could be optimum.
On what basis? I think the number of Sodium (or Na/K eutectic)  cooled reactors that have racked up any significant operating time can be counted on one hand.
No matter how efficient a nuclear solution would be, I think it has to have convincing and practical strategies for the following questions:
1. What do you do with the nuclear waste of a reactor?
Current space nuclear designs have been sealed for life. They are not refueled.

Quote from: Semmel
2. How do you dispose a reactor after it is decommissioned?
The units already sealed and "waste" heat is likely to remain a valuable byproduct on Mars for a long time to come. So remove the generating equipment and continue to harvest the heat.
Quote from: Semmel
3. Assuming there will be at least one reactor with a catastrophic failure of the containment vessel within the first 100 years of the colony, what effect does that have on the colony? And "it will not happen" is only an acceptable answer if it is physically impossible for the failure to happen.
You're assuming a Mars reactor would be exactly like one on Earth. That's a very bad starting point

"containment failure" is typically caused by a loss of coolant. If the fuel is solid and the cooling handled through multiply redundant heat pipes (true of the Kilopower design, which the Youtube link is basically talking about) that can't happen.

Title: Re: Power options for a Mars settlement
Post by: Semmel on 05/21/2017 11:35 am
"containment failure" is typically caused by a loss of coolant. If the fuel is solid and the cooling handled through multiply redundant heat pipes (true of the Kilopower design, which the Youtube link is basically talking about) that can't happen.

You are correct, I was limited to mobile in the lat days and coldnt watch the video. Now I understand better what you mean by the kilo-power design. It doesnt look like it can fail in the same way traditional reactors can.

It uses however U235, which has a half life of 7*10^8 years. Thats quite a long time. I am not sure its a good idea to just dum it somewhere. The nuclear processes will brittle the beryllium vessel. It will break at some point, even if it takes some thousend years.

If we use a nuclear reactor, we should have the responsibility to dispose it in a way that our kids or grandkids dont have to deal with it.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/21/2017 11:39 am
U235 is naturally occurring and the fact that it has a really long half life means it's basically not radioactive. (Half life means how long it take for half the atoms to decay. If that number is really long, then the number of decays per second is really, really low.)
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/21/2017 01:48 pm
Does a sealed reactor actually need to be refuelled or even retired? Presumably the power output just falls off over time, like an RTG. In which case why would you bother doing anything other than bring in a fresh one every few years to augment the old reactor?

One can envisage a thriving secondhand nuclear reactor market on Mars in fifty years time- older low output reactors being shipped out to distant outposts with low power requirements.
Title: Re: Power options for a Mars settlement
Post by: Dao Angkan on 05/21/2017 02:06 pm
The surface of Mars is already bathed in radiation, and colonisation is likely to be limited to a small precentage of the planet ... 99%+ of the planet will be lifeless. Still, if nuclear waste is considered an issue, then it will be a lot easier to dispose of it in space from the relatively low gravity well of Mars.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/21/2017 02:47 pm
Does a sealed reactor actually need to be refuelled or even retired? Presumably the power output just falls off over time, like an RTG. In which case why would you bother doing anything other than bring in a fresh one every few years to augment the old reactor?

One can envisage a thriving secondhand nuclear reactor market on Mars in fifty years time- older low output reactors being shipped out to distant outposts with low power requirements.
Assuming Mars settlement did grow as much as we hope I could see a trade probably buying more of them to give the same power level.

However the real payoff for Mars nuclear (could be a company name ?) would require more ambitious work.

The Kilopower design side steps fission product release (and hence needing FP containment) because the actual burn up of Uranium is very small. Depending on the enrichment level some of the U238 could be converted to Pu and begin to fission ("breeding" takes place in all reactors with fissile, but not actually fissionable, material in them, even PWR's). That leaves a lot of high grade Uranium in each unit.

Hypothetically it would be possible to disassemble the cores, separate the (small) quantity of FP's and actinides from the U235 and recast the U235 into a new core. The FP and actinides can then be stored (it's all pretty nasty and some has a long half life).

A more ambitious option yet would be to feed the mix of FP's and actinides into a molten salt reactor, which is quite flexible at both fissioning elements and irradiating FP's to push them further down their decay chains to harmless elements ("burning").
Title: Re: Power options for a Mars settlement
Post by: DAZ on 05/21/2017 03:30 pm
There has been some discussion in this thread regarding power to weight ratios of various proposed systems.  I believe there should be a discussion on 3 other very important considerations, namely space, weight, and labor.

When transporting an item to a distant location you need to consider all 3 factors.  Even when shipping on an aircraft we would think weight would be the predominant factor but volume can actually be the predominant factor.  So the question on aircraft quite often becomes have you palliated it out or grossed out.  Believe it or not quite often you will pallet out before you gross out.

So how does this pertain to power?  A nuclear reactor option, may or may not, have a higher power density per weight.  But it also could possibly have a higher power density for transported volume.  Solar cells and their associated supporting structures can be flat packed thus taking up a relatively small volume but they’re still likely to take more volume per kilowatt than a nuclear reactor.  The consideration of volume could become more important than the consideration of mass.  If you are taking something like humans, they are a relatively low weight high space item.  In addition what is needed to support them (namely food water life-support) also takes up a considerable amount of space.  So in this type of situation (especially even if you’re transporting a somewhat low number of people) your constraint, could be transportable volume as opposed to mass.

An additional constraint is the amount of available labor.  Labor is quite likely (as EM himself has stated) to be extremely limited at 1st.  The options might come down to something like this.  Unpack the nuclear reactor, drag it to its intended location, dig a hole in place to reactor inside and bury it.  Total labor time in days to weeks.  The other option could start unpacking, transporting, and assembling the solar power system.  This could take weeks to months of labor time.  In order to have such a lightweight and at the same time compact as possible for transportation the solar power system it will inherently take somewhat more labor to assemble.

This is labor that has to be used to assemble the power system that will also be desperately needed for other tasks.  These other tasks would include setting up the shelters, the fuel processing equipment and mining for water.  These 3 tasks alone could end up sucking up all the available labor.  In addition, there is the time factor.  If it takes months to get your power system up and running this also delays by months most of these other tasks.  You can’t arbitrarily just extend out your times as you do have a hard horizon (time for the next ships to arrive and depart) that you must adhere to.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/21/2017 04:08 pm
A lot of solar systems are easier to install than the nuclear. Digging a hole 1km from base is harder than pressing the unfurl button on an ultra flex array.
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 05/21/2017 04:19 pm
U235 is naturally occurring and the fact that it has a really long half life means it's basically not radioactive. (Half life means how long it take for half the atoms to decay. If that number is really long, then the number of decays per second is really, really low.)
The danger from used reactor fuel lies not in the unburned U-235 but in the mix of unstable short half-life fission products that build up during operation.

The radiation produced by their continued radioactive decay is hazardous, but a more immediate concern is decay heat since excess heat can lead to the failure of the structure containing the fuel.

In steady-state operation, decay of fission products produces about 6.5% of a reactor's output; when the main chain reaction is stopped, fission product decay continues and gradually declines.   One hour after shutdown it's at 1.5%.   A year later it's still producing 10kW per ton.   So a working cooling system is necessary for a considerable period.    (That cooling system could rely on convection rather than pumped circulation but you're still going to have a bad day if you lose your coolant..)
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 05:05 pm
A lot of solar systems are easier to install than the nuclear. Digging a hole 1km from base is harder than pressing the unfurl button on an ultra flex array.

And that would be good, if only that ultra flex array could function in a meaningful manner on Mars, as in last for more than a couple of months, withstand wind, or provide a useful amount of power...

Installing enough solar for several MWatt worth of power - that's more difficult then pressing a button.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 05/21/2017 05:08 pm
How about some form of heliostat?
Title: Re: Power options for a Mars settlement
Post by: DAZ on 05/21/2017 05:29 pm
This actually brings up an interesting point.  It is outside of SpaceX’s presented plans but it can be assumed that what SpaceX is doing is only part of an overall solution.  What I’m getting to are solar electric tugs.  It would seem reasonable that for the foreseeable future more cargo will be going toward Mars then returning from Mars.  To greatly increase the available cargo going to Mars above and beyond with the ITS could send it could launch this cargo before the Mars window opens and be transported via solar electric tugs.  These tugs, once they have delivered their cargo at Mars could make their way back to earth to pick up more cargo or stay in Mars orbit.  If they stay in Mars orbit they could become part of a solar power satellite.  You would still need to build the ground receiving station but this could be much easier to construct and probably even have less transported volume/mass than just solar power on the surface.  It also quite likely require less ground power storage and alleviate problems with dust and dust storms.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/21/2017 05:49 pm
A lot of solar systems are easier to install than the nuclear. Digging a hole 1km from base is harder than pressing the unfurl button on an ultra flex array.

And that would be good, if only that ultra flex array could function in a meaningful manner on Mars, as in last for more than a couple of months, withstand wind, or provide a useful amount of power...

Installing enough solar for several MWatt worth of power - that's more difficult then pressing a button.
Ultraflex does last a long time. Please don't inject false facts. Phoenix was buried by ice, not toppled by wind.

Additionally, an Ultraflex array can provide just as much power as a Kilopower module. Again, let's deal with facts.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 06:16 pm
A lot of solar systems are easier to install than the nuclear. Digging a hole 1km from base is harder than pressing the unfurl button on an ultra flex array.

And that would be good, if only that ultra flex array could function in a meaningful manner on Mars, as in last for more than a couple of months, withstand wind, or provide a useful amount of power...

Installing enough solar for several MWatt worth of power - that's more difficult then pressing a button.
Ultraflex does last a long time. Please don't inject false facts. Phoenix was buried by ice, not toppled by wind.

Additionally, an Ultraflex array can provide just as much power as a Kilopower module. Again, let's deal with facts.

The Phoenix power panel was simply not designed to last more than a few months.  The ice got it first, that's all.

It had an area of 3.1 m2, and produced an average power of 87 Watts in good weather.

So that's peanuts even in relation to a kiloPower system, which as noted above, is not what you'd want for a colony.  And even the Peanuts system didn't last.

For a colony, you need MWatt, and quickly 10x and 100x that. You need the power plant to last 10 years at least, or else as soon as you're done building it, you're already thinking about replacing it, and that doesn't even bring into account growth.

Ultraflexes on poles are not going to cut it.



 
Title: Re: Power options for a Mars settlement
Post by: Dao Angkan on 05/21/2017 06:20 pm
For Mars InSight solar arrays "75 m/s Martian wind load capability". 2.15m diameter (x2), 450 W. Projected lifetime of lander 2 years.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/21/2017 06:53 pm
That was the smallest variant of Ultraflex, why are you using it as the end-all be-all? That's intellectually dishonest. In system level trades, large Ultraflex is just as good as Kilopower. And Ultraflex is just one possible solution.

Kilopower gets 5-10W/kg. No better than solar and storage. So where are these great nukes that Mueller is talking about? Kilopower sure isn't it. It must be a proposal for a higher specific power solution.

It seems to me there are multiple schools of thought about surface power within SpaceX and Mueller is on one side. Publicly, Musk has mentioned just solar, and seems to think it'll be the major source of power for both Earth and Mars long-term.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 07:01 pm
For Mars InSight solar arrays "75 m/s Martian wind load capability". 2.15m diameter (x2), 450 W. Projected lifetime of lander 2 years.

And that right there is the differnerce between spec sheets and reality.

Those panels were 450 W peak, under nominal illumination, maybe even at Earth orbit.

However, in practice:

Quote
Before the storm hit, Phoenix was generating about 2,100 Watt-hours each sol...
  (From news stories at the time).  You can compare that to the insolation graph data I posted upthread.

Also, in practice:

The system was down after a few months.  It was ice, but it would also have gone done due to excessive wind, or wind-induced fatigue over time, etc.  It takes an inordinate amount of effort to make a PV panels that survives the environment for years, and until you do, you don't have an "almost system", you simply don't have a system.



Title: Re: Power options for a Mars settlement
Post by: Dao Angkan on 05/21/2017 07:04 pm
Phoenix was at a polar location, InSight will be at an equatorial location. Phoenix solar array had 24% efficiency, InSight has 29.5+% efficiency.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 07:05 pm
That was the smallest variant of Ultraflex, why are you using it as the end-all be-all? That's intellectually dishonest. In system level trades, large Ultraflex is just as good as Kilopower. And Ultraflex is just one possible solution.

Kilopower gets 5-10W/kg. No better than solar and storage. So where are these great nukes that Mueller is talking about? Kilopower sure isn't it. It must be a proposal for a higher specific power solution.

It seems to me there are multiple schools of thought about surface power within SpaceX and Mueller is on one side. Publicly, Musk has mentioned just solar, and seems to think it'll be the major source of power for both Earth and Mars long-term.

Because you brought up UltraFlex, and that's the only one that barely survived any time on the surface.

Larger structures will do worse.  In the brochure, ATK goes up to 40 m diameter.  Do you want to calculate the weight of a 40 m structure that can survive the wind for 10 years?

Using a vacuum-designed system as a benchmark for surface solar, using Watt/kg numbers that are simply nonsensical in that environment - that's where the problem lies. You so want to sell surface solar that you're ignoring the real-life realities, and just repeating the insane Watt/kg figure of merit than a thin-film array can achieve at zero g and vacuum.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 07:08 pm
Phoenix was at a polar location, InSight will be at an equatorial location. Phoenix solar array had 24% efficiency, InSight has 29.5+% efficiency.

Which means it had a bad insolation angle, but it was at summer, so it had a very favorable power cycle.  On the equator, you have 50% night, and still have to content with inperfect insolation angles during 50% of the daylight time.

I posted the actual insolation numbers upthread, look them up...  They match the reality of output from PV panels on the surface.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/21/2017 07:16 pm
No, I wasn't referring to ATK's brochure but to actual Mars surface architecture trades which include wind load masses, etc.

Here is a group of slides gathered by fission /advocates/ showing that solar is comparable or better that nuclear (for Equatorial sites), slide 33: http://spirit.as.utexas.edu/%7Efiso/telecon/Rucker_12-7-16/Rucker_12-7-16.pdf

I believe a mix of power makes the most sense, just like on Earth. But I don't see where Mueller is getting this idea that solar is heavier unless you're proposing a much more radical nuclear reactor design as I mentioned up thread (or tap an aquifer and dump heat into the aquifer).

Also, Kilopower units are $70-80 million apiece. SpaceX can't afford that price even for a single ITS worth of power. (This is a good opportunity for collaboration with folks like NASA, by the way... NASA or some international partner contributes some reactors to provide more robustness and diversity to the fledgling settlement's power grid).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 07:34 pm
No, I wasn't referring to ATK's brochure but to actual Mars surface architecture trades which include wind load masses, etc.

Here is a group of slides gathered by fission /advocates/ showing that solar is comparable or better that nuclear (for Equatorial sites), slide 33: http://spirit.as.utexas.edu/%7Efiso/telecon/Rucker_12-7-16/Rucker_12-7-16.pdf

I believe a mix of power makes the most sense, just like on Earth. But I don't see where Mueller is getting this idea that solar is heavier unless you're proposing a much more radical nuclear reactor design as I mentioned up thread (or tap an aquifer and dump heat into the aquifer).

Also, Kilopower units are $70-80 million apiece. SpaceX can't afford that price even for a single ITS worth of power.

The question of which power source will be better is complex, and probably not binary.

My objection is that when you bring in specific power numbers for solar that are irrelevant.  The really high numbers used for thin film are disconnected from surface mission design requirements.  I also don't understand why you're stuck on kiloPower.  It's irrelevant.

I brought up the ATK design not because I think that "this is how you'd do solar", but because you brought up UltraFlex.

These "reality factors" is why SpaceX arrived at that conclusion.  They actually have to make it work, and they (as relayed by Mueller) concluded that a solar system that is "long term surface worthy" has a poorer specific power than nuclear does.

They also concluded that initially, since the reactors do not exist, solar will have to do.  For an "initially" concept, you can relax the longevity requirement, and so this probably helped too.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/21/2017 07:45 pm
Kilopower is the only realistic nuclear power source in the near term. As Mueller said, SpaceX is not going to develop nuclear power, they can't afford it. But NASA can (partly because they can partner with DOE who has access to "free" enriched uranium).

Thin film is not irrelevant, as very lightweight structures are possible (yes, compatible with wind loads), and making structure for the thin film arrays is one of the most straightforward structural ISRU things you could do... Compressed soil bricks is one such method (that we know Musk is looking into for other purposes).
Title: Re: Power options for a Mars settlement
Post by: Patchouli on 05/21/2017 08:26 pm
No, I wasn't referring to ATK's brochure but to actual Mars surface architecture trades which include wind load masses, etc.

Here is a group of slides gathered by fission /advocates/ showing that solar is comparable or better that nuclear (for Equatorial sites), slide 33: http://spirit.as.utexas.edu/%7Efiso/telecon/Rucker_12-7-16/Rucker_12-7-16.pdf

I believe a mix of power makes the most sense, just like on Earth. But I don't see where Mueller is getting this idea that solar is heavier unless you're proposing a much more radical nuclear reactor design as I mentioned up thread (or tap an aquifer and dump heat into the aquifer).

Also, Kilopower units are $70-80 million apiece. SpaceX can't afford that price even for a single ITS worth of power. (This is a good opportunity for collaboration with folks like NASA, by the way... NASA or some international partner contributes some reactors to provide more robustness and diversity to the fledgling settlement's power grid).

In space power generation is one of the things NASA should be funding as a nuclear reactor makes a dust storm go from something that would shut down normal operations and possibly force an evacuation to more of a nuisance.

Though large scale chemical fuel storage in the form of methane along with fuel cells or ICE power generators could be another option.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 08:28 pm
Kilopower is the only realistic nuclear power source in the near term. As Mueller said, SpaceX is not going to develop nuclear power, they can't afford it. But NASA can (partly because they can partner with DOE who has access to "free" enriched uranium).

Thin film is not irrelevant, as very lightweight structures are possible (yes, compatible with wind loads), and making structure for the thin film arrays is one of the most straightforward structural ISRU things you could do... Compressed soil bricks is one such method (that we know Musk is looking into for other purposes).

kiloPower only came up in this thread. It's too small for the mission requirements, and I haven't heard SpaceX say they intend to use these micro-reactors on Mars.

I'd expect them to partner with someone like General Dynamics EB, or with one of the newer developers of MWatt-class nuclear power.

As for a surface system - I'll be happy to take a (critical) look...  But irrespective of the structure you come up with (I have to admit I've never heard of a brick-based design before) please use realistic insolation numbers, not peak numbers, and realistic conversion efficiencies at system level, not at single-cell test-stand level..

There's much of that going on.  For example, the panel on Phoenix, which is advertised as 450W, is actually using earth-orbit level insolation for the specification.  That's just playing hide-and-seek.

The figure of merit is kWatt-hr per sol, averaged over the year, with some allowance for doing more ISRU work during the hours-of-plenty, but then bringing into account that the ISRU equipment has to be up-scaled accordingly since it is running at a lower utilization factor, and bringing into account use of excess thermal power.  These are the kind of optimization I expect SpaceX has been fiddling with for several years now.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/21/2017 09:28 pm
what are you talking about as far as insolation values? All I did was link to the study in the FISO presentation.

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/21/2017 10:27 pm
Quote
Before the storm hit, Phoenix was generating about 2,100 Watt-hours each sol...
  (From news stories at the time).  You can compare that to the insolation graph data I posted upthread.

Also, in practice:

The system was down after a few months.  It was ice, but it would also have gone done due to excessive wind, or wind-induced fatigue over time, etc.  It takes an inordinate amount of effort to make a PV panels that survives the environment for years, and until you do, you don't have an "almost system", you simply don't have a system.
All true, but a settlement has resources that any machine simple does not have.

Humans that can go out and clean PV arrays or pick them up if they fall over or (for extreme simplicity) move them by hand through a certain number of degrees every hour.

I'd also remind people that 75 m/s is a pretty severe storm on Earth, but Mars surface pressure is 1/160.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/21/2017 11:25 pm
what are you talking about as far as insolation values? All I did was link to the study in the FISO presentation.

Here's what seems to be a well researched study:

http://ccar.colorado.edu/asen5050/projects/projects_2001/benoit/solar_irradiance_on_mars.htm

showing values both above the atmosphere and on the surface, as a function of latitude.

(Some interesting insights regarding polar collectors, btw)

The bottom line is that average surface insolation is 60-80 W/m2.  (Averaged over night/day and over the year), or ~100 in the most favorable location/ time-of-year

On top of that you have conversion efficiency (panels are 30-40% efficient, but are probably not tracking, and probably are partially obscured by dirt) and you realize you're scavenging power here.

I quoted above that Phoenix's panels got 87 Watts-avg out of 3.1 m2 of receiver, or 28 W-avg/m2, when relatively clean.

This is in rough agreement with the paper.

Long term solar deployment will do worse.  There will be more dust, more need to clean, more degradation, etc.

If you want a MWatt of power for ISRU, you need 35,000 m2 of installed PV area.  (7 football fields).

Just for 1 MWatt.












Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/22/2017 12:04 am
The previous study I pointed to assumed tracking for solar because it both increased output nominally and helped solve the dust and wind problem (by tilting to aid dust removal and by feathering in order to minimize wind loading). It's really a no-brainer (and even if it gets stuck, it still produces power, unlike if the moving parts of a reactor gets stuck).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/22/2017 12:43 am
The previous study I pointed to assumed tracking for solar because it both increased output nominally and helped solve the dust and wind problem (by tilting to aid dust removal and by feathering in order to minimize wind loading). It's really a no-brainer (and even if it gets stuck, it still produces power, unlike if the moving parts of a reactor gets stuck).

That's fine.  Then the design should include the benefits of tracking in terms of power output (~30% more), but also the mass penalty since the panels need to be supported on a central torque tube with the ability to pivot.  (Or on a gimbal if you're doing 2 axis tracking).

As for cleanliness, there are 100 designs for cleaning systems.  It's just a function of weight.  You can have robots run along the panels, for example, using the edges as rails.  It's just that your panels now have to be sturdy enough for that. 

With solar, everything is possible. It's just the resultant kg/kWatt that ends up being high.

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/22/2017 01:43 am
The previous study I pointed to assumed tracking for solar because it both increased output nominally and helped solve the dust and wind problem (by tilting to aid dust removal and by feathering in order to minimize wind loading). It's really a no-brainer (and even if it gets stuck, it still produces power, unlike if the moving parts of a reactor gets stuck).

That's fine.  Then the design should include the benefits of tracking in terms of power output (~30% more), but also the mass penalty since the panels need to be supported on a central torque tube with the ability to pivot.  (Or on a gimbal if you're doing 2 axis tracking).
That is included all that in the study I pointed to.
Quote

As for cleanliness, there are 100 designs for cleaning systems.  It's just a function of weight.  You can have robots run along the panels, for example, using the edges as rails.  It's just that your panels now have to be sturdy enough for that.
Um, it's included in the design. Tilting arrays mounted high will keep the dust off. (We know this based on operational experience from Spirit and Opportunity, this isn't just hand-waving... We can keep dust off the arrays by parking at an angle on top of a hill, simulating mounting higher and having tilting capacity.)

Quote
With solar, everything is possible. It's just the resultant kg/kWatt that ends up being high.
No, it's still better than fission (or essentially equivalent) in the study I showed. And the design they picked wasn't particularly novel and innovative, either.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/22/2017 04:18 am
Well, we've circled back, so I'm not going to reply directly.

All I can say is that when you wonder why Mueller stated what he did - the explanations are in the posts upthread.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/22/2017 06:52 am
The bottom line is that average surface insolation is 60-80 W/m2.  (Averaged over night/day and over the year), or ~100 in the most favorable location/ time-of-year

On top of that you have conversion efficiency (panels are 30-40% efficient, but are probably not tracking, and probably are partially obscured by dirt) and you realize you're scavenging power here.

I quoted above that Phoenix's panels got 87 Watts-avg out of 3.1 m2 of receiver, or 28 W-avg/m2, when relatively clean.

This is in rough agreement with the paper.

Long term solar deployment will do worse.  There will be more dust, more need to clean, more degradation, etc.

If you want a MWatt of power for ISRU, you need 35,000 m2 of installed PV area.  (7 football fields).

Just for 1 MWatt.
IIRC 40% needs rigid triple junction solar cells and AFAIK they are normally installed in a concentrator configuration. People have pointed out that's not a good system on Mars due to diffuse lighting caused by regular atmospheric dust storms.

AFAIK 20%+ is at or close to cutting edge on thin film PV so 50-100% bigger. OTOH you should get a much lighter structure, and a much lighter support structure to mount it.

It still remains a very big structure to erect and to keep clean.   
In space power generation is one of the things NASA should be funding as a nuclear reactor makes a dust storm go from something that would shut down normal operations and possibly force an evacuation to more of a nuisance.
To be clear NASA is funding Kilopower and has in fact moved to it for planning future DRMs. A live Kilopower ground test is scheduled for Dec this year (2017) excluding the radiator design but including a full reactor and Stirling generators up to 1Kw(e). The design is expected to stretch to 10Kw(e) and possibly up to 100Kw(e). This will be the closest that NASA has gone toward actually building a full space nuclear (where it's used has a big impact on the detailed radiator design, hence that's the part they are not testing) power reactor since 1965. Incidentally it'x actually 2x bigger in terms of electrical power generation but about 50x more efficient (Stirling Vs 1st gen thermoelectric modules).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/22/2017 11:05 am
Multi junction cells are indeed rigid, but can be thinned, and are used in concentration on earth for economic reasons that do not apply on Mars.

The diffuse light thing is caused by concentration, not by the mere use of MJ cells.

You can assume 35% conversion at the system level before dust, alignment, etc.

The weight comes from the substrate.
Title: Re: Power options for a Mars settlement
Post by: IRobot on 05/22/2017 01:28 pm
It still remains a very big structure to erect and to keep clean.   
I've already proposed a possible solution before: slighly tilted panels with an electroacoustic transducer attached to the surface (or support beams), to make it vibrate. Should be enough to kick out the dust on the low g of Mars.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/22/2017 01:43 pm
It still remains a very big structure to erect and to keep clean.   
I've already proposed a possible solution before: slighly tilted panels with an electroacoustic transducer attached to the surface (or support beams), to make it vibrate. Should be enough to kick out the dust on the low g of Mars.
So for that to even have a chance to work, the panels have to be rigid.

2 mm thick glass?

So 5 kg/m2, before the railing and acoustic generators...  Now add the support structure, and you're at 7-8 kg/m2.

So with 28 W/m2, you get 4 W/kg, and a MWatt weighs 250 tons.

Now add cabling to cover the several football fields, batteries for winter night time, and you see the problem.
Title: Re: Power options for a Mars settlement
Post by: IRobot on 05/22/2017 01:48 pm
It still remains a very big structure to erect and to keep clean.   
I've already proposed a possible solution before: slighly tilted panels with an electroacoustic transducer attached to the surface (or support beams), to make it vibrate. Should be enough to kick out the dust on the low g of Mars.
So for that to even have a chance to work, the panels have to be rigid.
No, no reason to be rigid. You just have to adjust the oscillation frequency to avoid damping from the film.


So 5 kg/m2, before the railing and acoustic generators...  Now add the support structure, and you're at 7-8 kg/m2.

Now add cabling to cover the several football fields, batteries for winter night time, and you see the problem.
You can power it directly from the solar panel and commands are sent wireless. There is no cabling or batteries required.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/22/2017 01:54 pm
Now add cabling to cover the several football fields, batteries for winter night time, and you see the problem.

No need to do it at night. The devices can be fed from the panel. They can do regular shakes or be activated by wireless control. No need for a lot of cabling.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/22/2017 01:55 pm
Now add cabling to cover the several football fields, batteries for winter night time, and you see the problem.

No need to do it at night. The devices can be fed from the panel. They can do regular shakes or be activated by wireless control. No need for a lot of cabling.
Power cabling, for the field...  And general usage batteries, sized to work even in winter when days are short - just adding to the mass of the system.

So for a MWatt system, it's about 1-2 kg/sec, so another 50-100 tons.

---

The point of all this is that in-space PV advertises kWatt/kg power levels, and that's actually within the realm of possibility for very specific systems in 1 AU orbit...  But by the time you deploy a true Mars surface system, you're 3 (!) orders of magnitude lower, at single digit W/kg...
Title: Re: Power options for a Mars settlement
Post by: IRobot on 05/22/2017 02:46 pm
Power cabling, for the field...  And general usage batteries, sized to work even in winter when days are short - just adding to the mass of the system.
We are talking about something not much more complex than a buzzer with a wireless uController, with a small cable (a few cm), weighting a few grams per panel, that would vibrate once in a while, perhaps once a day for 10 minutes. You could even ditch the remote control and just use a timer.

Easy, simple, self contained.
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/22/2017 03:03 pm
I find it a bit unsatisfying to think that a huge settlement with thousands of people and megawatts of power requirements would be entirely prefabricated on Earth. Surely the whole point of this endeavour is to eventually establish a self sustaining colony.

So rather than shipping dozens and dozens of ITS-loads of solar panels or reactors, look at what sorts of ISRU can be established early, to start reducing the mass burden. Propellant is the obvious low-hanging-fruit, and the entire architecture is founded on in-situ propellant manufacture. Likewise basic inputs for ECLSS such as O2, H2O, and presumably a proportion of the food requirements, ought to be Mars-sourced. Habitats will hopefully be constructed from Marscrete, and/or created by tunneling.
But why stop there? If the bulk of the mass of a solar array is in the support frame, why not just bulldoze banks of regolith to bunds, and sit the panels on these? What about manufacturing glass, metal structures, cable? All these things will be needed eventually, and it seems a much better use of payload mass to set up manufacturing capabilities than to keep on importing finished goods from Earth.

I know that the response to this will be "ITS has huge payload capacity" or "ITS will be really cheap" but the thing is, you want the bulk of your flights to be carrying people, not cargo.

ITS is not going to be all that cheap. The best case scenario is that you pony up a few hundred thousand dollars for a ticket, and share a ride with 99 other colonists. Even viewed in this light, the ITS would have to have an extremely low per-flight cost. Your ticket price is paying for one percent of the cost of six booster flights, five tanker flights, and one ITS flight to Mars, an ITS-worth of ISRU propellant, the return flight of the ITS, the refurbishment of the ITS ready for its next mission, plus a share of the amortisation cost for building that ITS. If each one 'only' costs $500m, and lasts 20 years, that's a bill of half a million dollars per colonist seat, just in amortisation costs alone. If each launch is $50m (WAG) that's a total of $4m per colonist seat.

Now if each colonist also needs X amount of cargo flown on another flight- ready built reactors or PVAs, etc- then the cost per ticket looks very much as though the number of people able and willing to take this up is not going to add up. But of course I hope I am wrong about this.
Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/22/2017 03:16 pm
I find it a bit unsatisfying to think that a huge settlement with thousands of people and megawatts of power requirements would be entirely prefabricated on Earth. Surely the whole point of this endeavour is to eventually establish a self sustaining colony.

Settlement can't possibly start with thousands of people. Technology maturation takes time. A base with ~20 people is about the maximum of what you want to do for the first 10 years.

They will need to put all prepared technologies (power generation, ISRU, food, etc) to the final test: actually try it in real Mars environment. As usual, not everything will work as good as planned, some redesign will occur.

For a small colony, shipping a lot of stuff from Earth is quite acceptable while ISRU is being tested.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 05/22/2017 05:33 pm
IF it is true that SpaceX is looking at sites roughly 40 degrees north for access to extensive and readily reachable near surface water ice, then solar insolation will be a problem compared to equatorial sites.  May be a reason Tom M blurted out about nuclear power.  Best case for solar sites are disjoint from best case for water sites.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/22/2017 05:43 pm
IF it is true that SpaceX is looking at sites roughly 40 degrees north for access to extensive and readily reachable near surface water ice, then solar insolation will be a problem compared to equatorial sites.  May be a reason Tom M blurted out about nuclear power.  Best case for solar sites are disjoint from best case for water sites.
Valid point.

However, Melas Chasma offers the best views on Mars. And lots of water in other places than just ice.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 05/22/2017 10:02 pm
IF it is true that SpaceX is looking at sites roughly 40 degrees north for access to extensive and readily reachable near surface water ice, then solar insolation will be a problem compared to equatorial sites.  May be a reason Tom M blurted out about nuclear power.  Best case for solar sites are disjoint from best case for water sites.
Valid point.

However, Melas Chasma offers the best views on Mars. And lots of water in other places than just ice.

I'm into views and human interesting surroundings as a criteria for a colony site.  Have to motivate people to go.  A flat featureless plain Viking 1 style ain't gonna get that job done.  Could be that SpaceX wants to land on Northern Plains with Red Dragon early on to test water ice mining in the easiest setting.  If experience shows it's viable with their methods, they might move to less water accessible but "interesting" sites near the equator where solar power for iSRU mining and processing maxes out, but move there with ground truth confidence they can do the mining.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/22/2017 11:09 pm
IF it is true that SpaceX is looking at sites roughly 40 degrees north for access to extensive and readily reachable near surface water ice, then solar insolation will be a problem compared to equatorial sites.  May be a reason Tom M blurted out about nuclear power.  Best case for solar sites are disjoint from best case for water sites.
Interesting question. Which is more important? A site close to the equator with good (by Mars standards) lighting or a site on top of a glacier? I'm guessing without a nearby glacier you're looking at pulling water vapor out of the air. Given the huge amounts of mass you need to process access to a glacier is the more important.

Another interesting point is that water or ice is a pretty good radiation shield and relatively easy to create cavities in (I think Zubrin suggested this idea first) so easier to dig a base into a glazier (perhaps with a big enough air gap around it to stop the ice melting anymore) than to bore into the side of a mountain or the rock floor.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/22/2017 11:15 pm
No, plain regolith and sulfates are both much richer in water than the air. Gypsum contains a lot of water and MSL and Opportunity keep finding lots of it.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/23/2017 04:14 am
Power cabling, for the field...  And general usage batteries, sized to work even in winter when days are short - just adding to the mass of the system.
We are talking about something not much more complex than a buzzer with a wireless uController, with a small cable (a few cm), weighting a few grams per panel, that would vibrate once in a while, perhaps once a day for 10 minutes. You could even ditch the remote control and just use a timer.

Easy, simple, self contained.

I know, and agree.  The cables I was referring to were the main cables for generated power, and the batteries, in connection with mass estimates.

You dust shaker is a fine idea.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/23/2017 06:47 am
I wonder how hard it will be to build a 500-1000km power line and disconnect settlement and power production. It would enable putting the solar arrays on a higher altitude too which would reduce impact of dust storms a lot. Most of the dust must be at low altitude. Not something for the very early stage of settlement but maybe not too far in the future to take it into account for location planning.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 05/23/2017 09:10 am
Why would the latitude have such a strong impact on mars? Assuming the solar panels are angled, even if they dont move can face the sun pretty effectively. The atmosphere is so thin, that almost no light is lost due to the tilt. They just need more space in between the rows of solar panels, but thats hardly a problem, ground real estate doesnt come at a premium on Mars last time I checked. So I miss something?
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 05/23/2017 11:54 am
Hours of sunlight in winter
Title: Re: Power options for a Mars settlement
Post by: JamesH65 on 05/23/2017 12:07 pm
Dust in the atmosphere would also be a big influence.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/23/2017 12:53 pm
I find it a bit unsatisfying to think that a huge settlement with thousands of people and megawatts of power requirements would be entirely prefabricated on Earth. Surely the whole point of this endeavour is to eventually establish a self sustaining colony.

So rather than shipping dozens and dozens of ITS-loads of solar panels or reactors, look at what sorts of ISRU can be established early, to start reducing the mass burden. Propellant is the obvious low-hanging-fruit, and the entire architecture is founded on in-situ propellant manufacture. Likewise basic inputs for ECLSS such as O2, H2O, and presumably a proportion of the food requirements, ought to be Mars-sourced. Habitats will hopefully be constructed from Marscrete, and/or created by tunneling.
But why stop there? If the bulk of the mass of a solar array is in the support frame, why not just bulldoze banks of regolith to bunds, and sit the panels on these? What about manufacturing glass, metal structures, cable? All these things will be needed eventually, and it seems a much better use of payload mass to set up manufacturing capabilities than to keep on importing finished goods from Earth.

I know that the response to this will be "ITS has huge payload capacity" or "ITS will be really cheap" but the thing is, you want the bulk of your flights to be carrying people, not cargo.

ITS is not going to be all that cheap. The best case scenario is that you pony up a few hundred thousand dollars for a ticket, and share a ride with 99 other colonists. Even viewed in this light, the ITS would have to have an extremely low per-flight cost. Your ticket price is paying for one percent of the cost of six booster flights, five tanker flights, and one ITS flight to Mars, an ITS-worth of ISRU propellant, the return flight of the ITS, the refurbishment of the ITS ready for its next mission, plus a share of the amortisation cost for building that ITS. If each one 'only' costs $500m, and lasts 20 years, that's a bill of half a million dollars per colonist seat, just in amortisation costs alone. If each launch is $50m (WAG) that's a total of $4m per colonist seat.

Now if each colonist also needs X amount of cargo flown on another flight- ready built reactors or PVAs, etc- then the cost per ticket looks very much as though the number of people able and willing to take this up is not going to add up. But of course I hope I am wrong about this.

This post has a "Style over Substance" theme to it, and other premises, that I very much disagree with.

Satisfaction isn't part of the planning process.  A huge settlement with 1000's of people might still be in the final years of the bootstrap phase or the early years of the growth phase.  Prefab and ISRU will be balanced based on what works best all things considered.  There's no implicit preference of people over cargo.  You send what best furthers the mission.  And the economic calculations seem premised on the colonists covering the full cost including infrastructure rather than most of it being subsidized in various ways.


The last self-sustaining colony created still imports a lot of finished goods from the rest of the world.
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/23/2017 02:09 pm
Yes, my premise was that the colonists are paying for this. If not them, then who?
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/23/2017 03:43 pm
I find it a bit unsatisfying to think that a huge settlement with thousands of people and megawatts of power requirements would be entirely prefabricated on Earth. Surely the whole point of this endeavour is to eventually establish a self sustaining colony.

So rather than shipping dozens and dozens of ITS-loads of solar panels or reactors, look at what sorts of ISRU can be established early, to start reducing the mass burden. Propellant is the obvious low-hanging-fruit, and the entire architecture is founded on in-situ propellant manufacture. Likewise basic inputs for ECLSS such as O2, H2O, and presumably a proportion of the food requirements, ought to be Mars-sourced. Habitats will hopefully be constructed from Marscrete, and/or created by tunneling.
But why stop there? If the bulk of the mass of a solar array is in the support frame, why not just bulldoze banks of regolith to bunds, and sit the panels on these? What about manufacturing glass, metal structures, cable? All these things will be needed eventually, and it seems a much better use of payload mass to set up manufacturing capabilities than to keep on importing finished goods from Earth.

I know that the response to this will be "ITS has huge payload capacity" or "ITS will be really cheap" but the thing is, you want the bulk of your flights to be carrying people, not cargo.

ITS is not going to be all that cheap. The best case scenario is that you pony up a few hundred thousand dollars for a ticket, and share a ride with 99 other colonists. Even viewed in this light, the ITS would have to have an extremely low per-flight cost. Your ticket price is paying for one percent of the cost of six booster flights, five tanker flights, and one ITS flight to Mars, an ITS-worth of ISRU propellant, the return flight of the ITS, the refurbishment of the ITS ready for its next mission, plus a share of the amortisation cost for building that ITS. If each one 'only' costs $500m, and lasts 20 years, that's a bill of half a million dollars per colonist seat, just in amortisation costs alone. If each launch is $50m (WAG) that's a total of $4m per colonist seat.

Now if each colonist also needs X amount of cargo flown on another flight- ready built reactors or PVAs, etc- then the cost per ticket looks very much as though the number of people able and willing to take this up is not going to add up. But of course I hope I am wrong about this.
I agree, but in the slightly longer term.

The whole point of the colony is self sufficiency, and without power, you have nothing.

However, the problem with local PV production, even for 1000 people, is that it takes a lot of energy to manufacture PV.

Earth solar panels became net energy positive only after pretty high scaling. 

So irrespective of mass and cost, if it takes more energy to make a PV panel than it will produce in its lifetime, then there's no point.

And if it takes, say, 4 years, for energy payback, given that you needed to put up the power upfront,  and the colony grew 2x over those 4 years, it's still a losing game.

Nuclear OTOH doesn't​ have this problem. With time, some fissionable deposits will be found on Mars, and the source power issue will be solved.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 05/23/2017 03:49 pm
MeekGee, that I'd actually a good point. How much energy per energy production (I.e. J/W) Do solar cells need here on earth? And what kind of production facilities are required?
Title: Re: Power options for a Mars settlement
Post by: envy887 on 05/23/2017 04:08 pm
MeekGee, that I'd actually a good point. How much energy per energy production (I.e. J/W) Do solar cells need here on earth? And what kind of production facilities are required?

Payback for marginal manufacturing energy input is as little as 1 year on Earth.

https://dspace.library.uu.nl/bitstream/handle/1874/7966/98054.pdf?sequence=1
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/23/2017 04:48 pm
Yes, my premise was that the colonists are paying for this. If not them, then who?

Well if I were in Musk's position, I would be working toward capturing MASSIVE revenue streams using synergistic technologies such that I can essentially provide them subsidized to the colonization effort.  He's already showing that's exactly what he intends with Solar City, CommX, The Boring Company, and even Tesla,.  All of these are synergistic.  I can imagine at least two other major revenue producing businesses.  Remember, he wants to go.  He can't do all the lifting himself.  He'd be little different than captains that transported people to the new world in exchange for a period of indentured servitude.  Just with a more palatable division of labor and requirements.   

Remember Musk is holding the strings.  He's not under a fiduciary duty to maximize profit.  Let's say with 24hour reuse he can relaunch a Falcon9 for $1M.  When he's got the operation running full speed and making tons of money, he can give away pro-bono launches for cost all he wants.  Just because a revenue producing asset like a GSO sat will pay a list price of $40M doesn't mean Musk can't give away a heavily subsidized launch and probably structure it as some kind of charitable contribution and get a tax deduction.  He could also do something like provide heavily subsidized launches that still turn a profit to launch non-revenue-producing payloads that are desirable to place into space.   

Back-of-the-napkin estimates (https://en.wikipedia.org/wiki/Interplanetary_Transport_System#Fabrication_cost_projections) of payload costs $70/lb to Mars (and certainly far lower to other interesting destinations I can think ok) puts an enormous amount of business opportunity in play.

And it's with all this in mind that I think Musk gets into the Nuclear Business when profits permit.
Title: Re: Power options for a Mars settlement
Post by: BobHk on 05/24/2017 02:09 am
Yes, my premise was that the colonists are paying for this. If not them, then who?

Colonists could record their 'adventures' and sell them as subscriptions to Earthers.  There are a number of interesting virtual tourism (via robots) ideas already percolating.  Did that colonist just find a plant fossil? Is that bigfoot?  On Mars?  My god the programming possibilities are endless.  Oh then theres the hard work, exploring and finding resources to exploit.  If you sell everything and have money left over you dont need it on Mars - you need it in a interest bearing account on Earth that will enable you to buy needful things and have them shipped to Mars.  Companies that are less inclined to kill their employees can hire colonists to perform experiments, scout, harvest resources for return to Earth, do astronomy from Mars, whatever humans can think of and the colonists will be on Mars to do it, and not for free eh?
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/24/2017 03:54 am
MeekGee, that I'd actually a good point. How much energy per energy production (I.e. J/W) Do solar cells need here on earth? And what kind of production facilities are required?

Payback for marginal manufacturing energy input is as little as 1 year on Earth.

https://dspace.library.uu.nl/bitstream/handle/1874/7966/98054.pdf?sequence=1

It is 1 year today, but it required terrestrial-scale production, and a huge investment in fab facilities - which in and of itself is also energy intensive, and has to be made up front. (Not upfront per panel, but upfront before the first panel leaves the line)

20 years ago, payback was about lifetime of the panel.

On Mars, we're talking about an initial colony of 1000 - 10,000 people?  A joke by terrestrial standards.
We're also talking about minimal facilities, which are energy wasteful. (energy efficiency relies on extensive facilities.  Thermal losses decrease with production scale, for example, and with the introduction of big and heavy heat exchangers)

Finally, with insolation down to 40% on Mars, there's a factor of 2.5x slapped on the energy payback time.

BTW - in terrestrial history, it was all Si.   It might be better for MJ panels.

------

But the nature of PV is that you're scavenging single-digit Watts per m2 of panel.  And that panel, and associated structure, take energy to make.

We're really lucky on Earth that we can just build giant factories and figure out the energy balance later.  On Mars, every time you pick up power tool and drill a hole, you just eat up irreplaceable Watt-seconds.  Not to mention every time you fashion a glass plate for a panel, or extrude a sheet of plastic.

Title: Re: Power options for a Mars settlement
Post by: docmordrid on 05/24/2017 05:10 am
>
But the nature of PV is that you're scavenging single-digit Watts per m2 of panel.

About 197 W/m2, 330 W/1.67 m2 Panasonic HIT PV N330 panel.

https://eu-solar.panasonic.net/en/solar-panel-vbhn325sj47-vbhn330sj47.htm
Title: Re: Power options for a Mars settlement
Post by: BobHk on 05/24/2017 05:21 am
Well there is wind on Mars, not like on earth, but its there.  You can print wind turbine parts (except the metals might have to be shipped in - not exactly sure what can be sourced on Mars).  Would it be worth it to also deploy wind power generation? 

https://www.nasa.gov/centers/ames/news/releases/2001/01_72AR.html

Month long dust storms will take a bite out of pv power generation. 

Turbines with RTGs anyone?

The article linked above was from 2001.  Does anyone know what came of the experiment?
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/24/2017 06:02 am
>
But the nature of PV is that you're scavenging single-digit Watts per m2 of panel.

About 197 W/m2, 330 W/1.67 m2 Panasonic HIT PV N330 panel.

https://eu-solar.panasonic.net/en/solar-panel-vbhn325sj47-vbhn330sj47.htm

Read upthread, avg. power, based on measured and modeled insolation, and corroborated by actual output of lander panels.
Title: Re: Power options for a Mars settlement
Post by: Dalhousie on 05/24/2017 06:19 am
IF it is true that SpaceX is looking at sites roughly 40 degrees north for access to extensive and readily reachable near surface water ice, then solar insolation will be a problem compared to equatorial sites.  May be a reason Tom M blurted out about nuclear power.  Best case for solar sites are disjoint from best case for water sites.

At the equator the ice is probably still here, a little deeper.  This being 4 m rather than 1 m.  There is a good chance there is ice at these depths beneath Curiosity in Gale crater, for example, given Curiosity results.  There is also thermal inertia data for relatively shallow near equatorial ice, as geomorphic evidence in the form of thermokarst, rock glaciers, rampart craters, and solifluction.  Four metres is a bit deep for initial missions but is not a huge depth for settlement scale projects.

Alternative you can increase the output of solar panels by tilting them. Again not a first mission option but acceptable for later missions. Single axis tracking is also relatively straight forward.
Title: Re: Power options for a Mars settlement
Post by: Dalhousie on 05/24/2017 06:23 am
The only problem with nuclear power is the disposal of waste and old reactors. These things are contaminated with radiation producing isotopes and chemically very poisonous elements.

Much less a problem with molten salt reactors, especially those which burn thorium.

Still a huge problem from fission products, transuranics and the rest
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/24/2017 09:20 am
No, plain regolith and sulfates are both much richer in water than the air. Gypsum contains a lot of water and MSL and Opportunity keep finding lots of it.
In hindsight they sound much more accessible than drilling into a glacier, depending on the chemical and mechanical complexity and the energy bill for the extraction.

"No drilling" sounds like it beats "some drilling (to unknown depth)," all else being equal.

WRT to this thread I guess the question would be what would be the power budget for a drill that drills a well big enough to extract the amount of water (although I doubt it will be so convenient as to be pure ice  :( . In any case the ISRU will have to be designed to cope with the worst case ) needed to process the amount of propellant to refuel an ITS?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/24/2017 09:25 am
Yes, my premise was that the colonists are paying for this. If not them, then who?

Yes, my premise was that the colonists are paying for this. If not them, then who?

Colonists could record their 'adventures' and sell them as subscriptions to Earthers.  There are a number of interesting virtual tourism (via robots) ideas already percolating.  Did that colonist just find a plant fossil? Is that bigfoot?  On Mars?  My god the programming possibilities are endless.  Oh then theres the hard work, exploring and finding resources to exploit.  If you sell everything and have money left over you dont need it on Mars - you need it in a interest bearing account on Earth that will enable you to buy needful things and have them shipped to Mars.  Companies that are less inclined to kill their employees can hire colonists to perform experiments, scout, harvest resources for return to Earth, do astronomy from Mars, whatever humans can think of and the colonists will be on Mars to do it, and not for free eh?

Perhaps better in this thread?

https://forum.nasaspaceflight.com/index.php?topic=41937.0
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/24/2017 09:34 am
The only problem with nuclear power is the disposal of waste and old reactors. These things are contaminated with radiation producing isotopes and chemically very poisonous elements.

Much less a problem with molten salt reactors, especially those which burn thorium.

Still a huge problem from fission products, transuranics and the rest
Depends on the design.

IIRC MSR's are quite efficient in terms of neutron production (no steel fuel pins to absorb neutrons for a start in most design) and quite tolerant of what's put in them. some designs have been proposed as "burner" reactors that take FP's and transuranics as fuel, fissioning them to release energy or irradiating them to shift them to different (potentially much faster) decay paths.

The result is a very small amount of high level waste
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/24/2017 11:44 am
I think the waste issue is not even worth discussing. People don't have a good mental picture of how much waste is produced and so assume it's a lot even though it's absolutely minuscule. So many other problems should be the focus first.
Title: Re: Power options for a Mars settlement
Post by: sghill on 05/24/2017 01:23 pm
MeekGee, that I'd actually a good point. How much energy per energy production (I.e. J/W) Do solar cells need here on earth? And what kind of production facilities are required?

As someone who used to own a solar power development company, I can give you some considerations.

It's probably worth a little primer on solar panels here.

Most people think of solar panels as the rectangular window framed silicon wafer panels people play Tetris with on their roofs.

These types of silicon wafer panels can also be manufactured without the framing, and are only a millimeter thick or so.  They are extremely fragile when made like this, so you usually only see them used in space applications- think ISS main PV arrays or the original Hubble PV arrays (which were later replaced with rigid panels).

The other main type of panel is called "thin-film"  These panels are robust and flexible, but they don't come in "panels" they come in spools from the factory.  You can make the spool as long as you want, but after a while it gets hard to transport it or for it to hold it's shape efficiently.  For residential purposes, they are often also sold in the "window frame" format due to ease of replacement.  Thin-film panels tend to be less efficient than their wafer counterparts, but not always, and PV efficiency changes like fish-market pricing.

Thin film panels would work well on Mars, because you'd lay the spool on the ground and just roll it out, then connect your electrical connectors.  Little rocks wouldn't matter, and bigger rocks can just get raked out of the way.

Solar cells are generally produced using "obsolete" silicon wafer production equipment that is scrapped after computer chip manufacturers move on to the latest and greatest computer chip.  That's why we have so much rigid solar panel dumping out of China. They buy the second hand chip production equipment, make some wafers, wire them together, and then put a glass and aluminium frame around it. Thin Film solar panels are a little harder to manufacture.

In other words, if you can produce computer chips on Mars you can also produce solar cells.  The problem is that you need all of the mining and refining industries to be equally advanced in order to have the feed stock for silicon chip manufacturing.  FAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAR cheaper in my estimation to import the PV capacity you need from Earth and purchase it with things you can do on Mars (precious metal mining and IP production (which includes exploration and research) will be the only two viable industries for decades, IMHO).

Now consider this.  If you've got solar panels on Mars, you need to clean the panels no matter what.  So it's an equivalent cost so to speak with any framed panel system.

Where the cleaning expense (manpower and time) differs is here: panels that you roll out on the ground are far easier to clean than panels that are elevated.  Just walk along them with a push broom (trust me, I've done this more times than I care to remember) versus spending hours with a brush at the end of a boom in a spacesuit.

Plus, as I've pointed out in previous posts, panels laying on the ground are cheaper, easier to and lighter to deploy, and have fewer points of failure and less mass per watt.

Just use tent stakes every few feet to keep them on the ground and sweep it clean when you need to.  Better yet, in the low pressure environment, squirt them with a water hose and it'll clean them like a nitrogen bath here on Earth!  (Side note, I think rapidly boiling off water is the source of the "blueberries" on Mars).

One more point.  Panels operate more efficiently when warm.  If they are on the ground, they'll benefit from surface temps that can reach into the 70's (f), and the ground warmth will continue into the night. 

When I read "The Martian" I thought: "Why would they have actual panels??? He'd be far more likely to have a thin-film spool and just drag them all behind the rover like a sled!"

See also this thread: http://forum.nasaspaceflight.com/index.php?topic=37518.0
and this thread specifically regarding dust removal: http://forum.nasaspaceflight.com/index.php?topic=37874.msg1393003#msg1393003

We've been repeating this conversation for years now.



Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/24/2017 01:39 pm
Better yet, in the low pressure environment, squirt them with a water hose and it'll clean them like a nitrogen bath here on Earth!

Not with water costs on Mars... Compressed "air" maybe?

Quote
One more point.  Panels operate more efficiently when warm.  If they are on the ground, they'll benefit from surface temps that can reach into the 70's (f), and the ground warmth will continue into the night.

Perfect example of people not really understanding how cold Mars is.
Both Viking landers, during 6 years, never registered temperatures above -6 C.
The highest ever temperature _estimated_ (not directly measured) from orbital IR observations is something like +15 C (a black surface in a well wind-protected area on a calm day).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/24/2017 02:18 pm
MeekGee, that I'd actually a good point. How much energy per energy production (I.e. J/W) Do solar cells need here on earth? And what kind of production facilities are required?

As someone who used to own a solar power development company, I can give you some considerations.

... Thin-film panels tend to be less efficient than their wafer counterparts, but not always, and PV efficiency changes like fish-market pricing.

...


I don't know about that.  Each technology is pretty specific.  For any flexible deployable product out there that can be made to survive 10+ years on the Martian surface - you need to come up with two numbers - conversion efficiency, and aerial density.  The flex types "roll" panels are pretty low efficiency.

Also consider dust abrasion. One you leave glass behind, you're susceptible to very high velocity dust abrasion. Mars may have lower density atmosphere, but it has fast winds.  If you're micro-scratching the panels, they will deteriorate very fast...

Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 05/24/2017 04:12 pm
IIRC MSR's are quite efficient in terms of neutron production (no steel fuel pins to absorb neutrons for a start in most design) and quite tolerant of what's put in them. some designs have been proposed as "burner" reactors that take FP's and transuranics as fuel, fissioning them to release energy or irradiating them to shift them to different (potentially much faster) decay paths.

The result is a very small amount of high level waste
That sounds like the MSR design proposed by Transatomic Power.   Sadly they're less optimistic about this now:

"Nuclear Energy Startup Transatomic Backtracks on Key Promises",
https://www.technologyreview.com/s/603731/nuclear-energy-startup-transatomic-backtracks-on-key-promises/

Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/24/2017 05:24 pm
MeekGee, that I'd actually a good point. How much energy per energy production (I.e. J/W) Do solar cells need here on earth? And what kind of production facilities are required?

As someone who used to own a solar power development company, I can give you some considerations.

... Thin-film panels tend to be less efficient than their wafer counterparts, but not always, and PV efficiency changes like fish-market pricing.

...


I don't know about that.  Each technology is pretty specific.  For any flexible deployable product out there that can be made to survive 10+ years on the Martian surface - you need to come up with two numbers - conversion efficiency, and aerial density.  The flex types "roll" panels are pretty low efficiency.

Also consider dust abrasion. One you leave glass behind, you're susceptible to very high velocity dust abrasion. Mars may have lower density atmosphere, but it has fast winds.  If you're micro-scratching the panels, they will deteriorate very fast...



Producing glass must be much easier than producing semiconductors... we've been doing it for thousands of years, after all. Or perhaps a transparent polymer instead?
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/24/2017 05:37 pm
For Mars by the way, a liquid sodium cooled reactor could be optimum.
On what basis? I think the number of Sodium (or Na/K eutectic)  cooled reactors that have racked up any significant operating time can be counted on one hand.

We can debate different types of reactor - perhaps elsewhere. However, PWRs were originally designed for nuclear submarines, and then became the dominant technology, despite their limitations.Better technologies currently being worked on include:
- Pebble bed type designs using gases as the coolant. China is building a 200MW prototype
- Molten Salt designs, as tested in the USA in the 1970s. There are several companies with workable molten salt designs
- Liquid sodium cooled, as tested in the Integral Fast Reactor and currently offered (and working) from Rosatom.

These are all passive safety designs, BUT - the passive safety relies on
1. convection
2. heat transfer to water or air in the environment
so it won't work in space, and will be limited on Mars. It is therefore very hard to design a passively safe reactor for use in space. (A small pebble bed perhaps, if it loses cooling, could rise to >2,000C and lose enough heat through radiation).

The liquid sodium design relies slightly less on convection, because sodium is an excellent conductor of heat. A sodium bath will take away heat from a reactor even without convection.

Liquid sodium reactors look very promising but they have one drawback - sodium reacts with water or air. That is much less of a risk on Mars compared to on Earth.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/24/2017 05:47 pm
IIRC MSR's are quite efficient in terms of neutron production (no steel fuel pins to absorb neutrons for a start in most design) and quite tolerant of what's put in them. some designs have been proposed as "burner" reactors that take FP's and transuranics as fuel, fissioning them to release energy or irradiating them to shift them to different (potentially much faster) decay paths.

The result is a very small amount of high level waste
That sounds like the MSR design proposed by Transatomic Power.   Sadly they're less optimistic about this now:

"Nuclear Energy Startup Transatomic Backtracks on Key Promises",
https://www.technologyreview.com/s/603731/nuclear-energy-startup-transatomic-backtracks-on-key-promises/


Transatomic is a very ambitious design - and perhaps the claims were too good to be true.

Nearer term are ThorCon and Terrestrial Energy, who's designs are very closely based on the Weingberg's MSRs of the 1960s/70s. They are burners, not breeders. They can convert Thorium (hence Thor-Con) in Uranium for burning, but can't consume Pu240, or significant amounts of U238.

For that you need a fast spectrum design, examples of which include Moltex's Stable Salt Reactor (http://www.moltexenergy.com/) and GE-Hitachi's PRISM (sodium cooled) reactor (http://gehitachiprism.com/what-is-prism/). Those are able to convert U238 and Pu240 into Fission products.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/24/2017 08:27 pm
These are all passive safety designs, BUT - the passive safety relies on
1. convection
2. heat transfer to water or air in the environment
so it won't work in space, and will be limited on Mars. It is therefore very hard to design a passively safe reactor for use in space. (A small pebble bed perhaps, if it loses cooling, could rise to >2,000C and lose enough heat through radiation).

The liquid sodium design relies slightly less on convection, because sodium is an excellent conductor of heat. A sodium bath will take away heat from a reactor even without convection.

Liquid sodium reactors look very promising but they have one drawback - sodium reacts with water or air. That is much less of a risk on Mars compared to on Earth.
If you want to operate it in space that will kill it anyway depending on how fast heat moves through liquid sodium (which IIRC is governed by the metals diffusivity).

When Physicists design a reactor they choose Sodium. When actual engineers design a metal cooled reactor they go with Lead or Lead/Bismuth alloy. SNAP 10a was designed 6 decades ago.

You've also ignored reactors cooled by heat pipes, which will work in zero g and without needing a pump.

The problem with all liquid metal cooled reactors is modern safety rules require them to be sent to orbit switched off. That means the first order of business is to melt the metal coolant. The NASA DRM 5.0 design took something like 5Kw of power to do this, but a heat pipe cooled design does not need this, and can operate in zero g, which makes Kilopwer so attractive across a wide range of missions.

Note also that despite using heat pipes Kilopwer drives Stirling generators with about a 28% overall efficiency, compared to the (maybe) 6% of modern thermoelectric generator modules.
Nearer term are ThorCon and Terrestrial Energy, who's designs are very closely based on the Weingberg's MSRs of the 1960s/70s. They are burners, not breeders. They can convert Thorium (hence Thor-Con) in Uranium for burning, but can't consume Pu240, or significant amounts of U238.

For that you need a fast spectrum design, examples of which include Moltex's Stable Salt Reactor (http://www.moltexenergy.com/) and GE-Hitachi's PRISM (sodium cooled) reactor (http://gehitachiprism.com/what-is-prism/). Those are able to convert U238 and Pu240 into Fission products.
I'd be weary of such absolute statements, given MSRs can have new fuel bled into them and thermal, epithermal and fast can vary depending on the salt mixture. The ability to get major fission poisons like Xenon be bled off is a major help as well.
Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/24/2017 08:42 pm
Better technologies currently being worked on include:
- Pebble bed type designs using gases as the coolant. China is building a 200MW prototype

For some definition of "better". Here's a presentation "Decommissioning problems of German pebble bed reactors".

TL,DR: it's a huge PITA.

Selected quotes

"Problematic features of carbon/graphite: burnable, porous, high sorption capability for radioactive nuclides, easily leachable, fast radiolytic attack in presence of water/air, C-14 formation from nitrogen impurities.
Pronounced friction of fuel element graphite in He (= sub-μ dust, broken fuel pebbles)."

"AVR confessed in 2000: most heavily Sr-90 contaminated nuclear facility worldwide (100 TBq Sr-90)"

"Vessel still contains at least 200 fuel elements (e.g. in cracks of the broken bottom reflector)"

"Still contains 1.6 kg of fissile material (3000 broken pebbles of 27.000 not yet removed)"

Ho hum. When I was reading about awesome features of pebble bed reactors, "lots of radioactive dust and broken pebbles stuck everywhere" was never advertised...

Also, AVR "overheated to 950 C" at some point, which is strange to hear - weren't pebble bed reactors _designed_ to do so on low power or loss of cooling? Why now heating to mere 950 C caused severe problems?

I have this feeling all paper reactors are amazing while they stay on paper.
Title: Re: Power options for a Mars settlement
Post by: MickQ on 05/24/2017 11:46 pm
I don't have the numbers to work it out so:   
One appropriately sized reactor - One ITS,
Solar panels and storage to provide the same power - How many ITS ?
Title: Re: Power options for a Mars settlement
Post by: DAZ on 05/24/2017 11:52 pm
Power to weight is not the only consideration.  It may not even be the most important consideration.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/25/2017 12:15 am
I don't have the numbers to work it out so:   
One appropriately sized reactor - One ITS,
Solar panels and storage to provide the same power - How many ITS ?
One, possibly less. Current fission options aren't actually better than state of the art solar and storage, yes even including the reduced average insolation.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 05/25/2017 12:44 am
I don't have the numbers to work it out so:   
One appropriately sized reactor - One ITS,
Solar panels and storage to provide the same power - How many ITS ?

Here's a page & PDF link about Kilopower (10.9 mb)

https://ntrs.nasa.gov/search.jsp?R=20170002010
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/25/2017 07:21 am
Ho hum. When I was reading about awesome features of pebble bed reactors, "lots of radioactive dust and broken pebbles stuck everywhere" was never advertised...
One way to look at technology is as an artifact of the corporate culture that made it.

Westinghouse built steam boilers for the US Navy. Guess what? It's reactor looks like a Uranium heated steam boiler.

Germany has large supplies of coal. Guess what? Its reactor looks like a coal burning furnace, with Uranium filled "coals." :)
Unfortunately it turns out the "clinker" at the bottom of a nuclear furnace is a bit more trouble than the regular kind.

Quote from: gospacex
Also, AVR "overheated to 950 C" at some point, which is strange to hear - weren't pebble bed reactors _designed_ to do so on low power or loss of cooling? Why now heating to mere 950 C caused severe problems?
As in exceeded it's design temperature level, which probably affected all the rest of the plant. AFAIK the actual "pebbles" are rated much higher. BTW that's about 3x what a PWR runs at. By that temperature the metal of most PWR's would have started to soften quite a lot.
Quote from: gospacex
I have this feeling all paper reactors are amazing while they stay on paper.
On paper anything is possible.  :(

In hindsight they look like they focused on high temperature FP containment (which the pebbles do quite well) but it seemed no one spent much time thinking about how those pebbles would grind together, and wheather or not they were hard enough to resist the grinding, especially at the bottom of the pile.  :(

Which is another way of saying that reactor design is a very complex multi-variable optimization problem and what you consider an "optimal" design depends on what weight you give to the different aspects of that design.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/25/2017 08:08 am
I don't have the numbers to work it out so:   
One appropriately sized reactor - One ITS,
Solar panels and storage to provide the same power - How many ITS ?

Here's a page & PDF link about Kilopower (10.9 mb)

https://ntrs.nasa.gov/search.jsp?R=20170002010
Excellent report. NASA seems very serious about Kilopower, even to working out how to fuel it on the pad.

Some interesting numbers.
(page 6) RTG 91840 Curies. Switched off reactor 5 Curies. On the pad or during ascent the reactor option is (literally) 10 000x safer.
(Page 7) Kuiper Belt Object Orbiter study. RTG/ASRG package is 5W(e)/Kg. Single fast reactor 7W(e)/Kg.
(page 8 ) The NASA ISRU demonstrator baselines gimbal mounted ATK Ultraflex arrays 120VDC and 33% conversion efficiency and a potential 120day dust storm. They can tilt to 45deg to shake off dust.
(Page 9) NASA view a 175-225 day LEO to mars trip as "fast."

These are the numbers that NASA are saying they are using to evaluate Kilopower against solar systems. Wheather people agree with them is a different matter but those are what NASA is working around.

Where Kilopower really scores is when you you can use a larger (10Kwe) unit to drive a bigger ion thruster  to the point where you can eliminate a whole rocket stage (and possibly aerobraking as well), but that's more for outer planet science missions but this is tricky as the cost of the payload is not on the same budget as the cost of the LV. It's also OT for this thread.
Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/25/2017 08:24 am
In hindsight they look like they focused on high temperature FP containment (which the pebbles do quite well)

This did not work as well as promised, too:
"AVR confessed in 2000: most heavily Sr-90 contaminated nuclear facility worldwide (100 TBq Sr-90)"
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/25/2017 12:15 pm
Ho hum. When I was reading about awesome features of pebble bed reactors, "lots of radioactive dust and broken pebbles stuck everywhere" was never advertised...
One way to look at technology is as an artifact of the corporate culture that made it.

Westinghouse built steam boilers for the US Navy. Guess what? It's reactor looks like a Uranium heated steam boiler.

Germany has large supplies of coal. Guess what? Its reactor looks like a coal burning furnace, with Uranium filled "coals." :)
Unfortunately it turns out the "clinker" at the bottom of a nuclear furnace is a bit more trouble than the regular kind.

Quote from: gospacex
Also, AVR "overheated to 950 C" at some point, which is strange to hear - weren't pebble bed reactors _designed_ to do so on low power or loss of cooling? Why now heating to mere 950 C caused severe problems?
As in exceeded it's design temperature level, which probably affected all the rest of the plant. AFAIK the actual "pebbles" are rated much higher. BTW that's about 3x what a PWR runs at. By that temperature the metal of most PWR's would have started to soften quite a lot.
Quote from: gospacex
I have this feeling all paper reactors are amazing while they stay on paper.
On paper anything is possible.  :(

In hindsight they look like they focused on high temperature FP containment (which the pebbles do quite well) but it seemed no one spent much time thinking about how those pebbles would grind together, and wheather or not they were hard enough to resist the grinding, especially at the bottom of the pile.  :(

Which is another way of saying that reactor design is a very complex multi-variable optimization problem and what you consider an "optimal" design depends on what weight you give to the different aspects of that design.

Perfect counter example to "Engineering is done with numbers."

Most of the difficult to evaluate parts of 'engineering' are value judgements like weights, merit functions, popular acceptance/opposition, etc.  Too often engineers call the factors that they cannot objectively determine '0' or '1'.

Nuclear died in the USA because of a few of these subjective (therefore assumed unimportant) factors.
Title: Re: Power options for a Mars settlement
Post by: sghill on 05/25/2017 03:16 pm
Quote
One more point.  Panels operate more efficiently when warm.  If they are on the ground, they'll benefit from surface temps that can reach into the 70's (f), and the ground warmth will continue into the night.

Perfect example of people not really understanding how cold Mars is.
Both Viking landers, during 6 years, never registered temperatures above -6 C.
The highest ever temperature _estimated_ (not directly measured) from orbital IR observations is something like +15 C (a black surface in a well wind-protected area on a calm day).

Perfect example of shooting one's mouth off.

https://mars.nasa.gov/mer/spotlight/20070612.html

"Temperatures in the shade for Spirit ranged from highs of about 35 degrees C. (95 degrees F.) in summer to lows of -90 degrees C. (-130 degrees F.)... Temperatures in the shade for Opportunity ranged from about 30 degrees C. (86 degrees F.) in summer to minus 80 degrees C. (-112 degrees F.) in winter. "

Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/25/2017 04:07 pm
"Temperatures in the shade for Spirit ranged from highs of about 35 degrees C. (95 degrees F.) in summer to lows of -90 degrees C. (-130 degrees F.)... Temperatures in the shade for Opportunity ranged from about 30 degrees C. (86 degrees F.) in summer to minus 80 degrees C. (-112 degrees F.) in winter. "

Raising the interesting question to my uninformed mind:  What is the temperature difference between "in the shade" and "not in the shade".  It seems the latter a touch more relevant to the discussion and pushing further from the -6 degree point.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/25/2017 07:52 pm
Better technologies currently being worked on include:
- Pebble bed type designs using gases as the coolant. China is building a 200MW prototype

For some definition of "better". Here's a presentation "Decommissioning problems of German pebble bed reactors".



Also, AVR "overheated to 950 C" at some point, which is strange to hear - weren't pebble bed reactors _designed_ to do so on low power or loss of cooling? Why now heating to mere 950 C caused severe problems?

I have this feeling all paper reactors are amazing while they stay on paper.
Well, this one isn't on paper any more:
http://www.world-nuclear-news.org/NN-Fuel-loading-starts-at-Chinese-demonstration-HTGR-0704175.html

Not sure about the cracks problems. The spheres are meant to be good over 2,000C.

I do think recycling of the spheres will be very,very hard, leaving the only option as complete burial. Which isn't really a problem.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/25/2017 08:12 pm
If you want to operate it in space that will kill it anyway depending on how fast heat moves through liquid sodium (which IIRC is governed by the metals diffusivity).
I'd have expected conduction to be a lot faster than diffusion.

Quote
When Physicists design a reactor they choose Sodium. When actual engineers design a metal cooled reactor they go with Lead or Lead/Bismuth alloy. SNAP 10a was designed 6 decades ago.
Only if they're worried about Sodium coming into contact with water. If you're not, then Sodium is vastly superior to Lead in every respect.

Quite a few Alpha class submarine lead cooled reactors have frozen solid, and in lead cooled reactors, the primary pump uses a significant chunk of the electricity generated.

I quite like them for marine reactors, as if they go to the bottom of the ocean, the solid fuel rods get encased in a layer of lead.

Quote
You've also ignored reactors cooled by heat pipes, which will work in zero g and without needing a pump.
Not familiar with heat pumps. Are they being considered for Earth based reactors?

Quote
The problem with all liquid metal cooled reactors is modern safety rules require them to be sent to orbit switched off. That means the first order of business is to melt the metal coolant. The NASA DRM 5.0 design took something like 5Kw of power to do this, but a heat pipe cooled design does not need this, and can operate in zero g, which makes Kilopwer so attractive across a wide range of missions.
That will also be a problem with molten salt reactors. Still, 5KW isn't too much. I guess time is not too important.

Quote
Note also that despite using heat pipes Kilopwer drives Stirling generators with about a 28% overall efficiency, compared to the (maybe) 6% of modern thermoelectric generator modules.
As a wise man said "On paper anything is possible." Stirling generators are proving very difficult to perfect, and typically struggle to get 20% efficiency even when using gas heating and a water sink at 30C.

Nearer term are ThorCon and Terrestrial Energy, who's designs are very closely based on the Weingberg's MSRs of the 1960s/70s. They are burners, not breeders. They can convert Thorium (hence Thor-Con) in Uranium for burning, but can't consume Pu240, or significant amounts of U238.

For that you need a fast spectrum design, examples of which include Moltex's Stable Salt Reactor (http://www.moltexenergy.com/) and GE-Hitachi's PRISM (sodium cooled) reactor (http://gehitachiprism.com/what-is-prism/). Those are able to convert U238 and Pu240 into Fission products.

I'd be weary of such absolute statements, given MSRs can have new fuel bled into them and thermal, epithermal and fast can vary depending on the salt mixture. The ability to get major fission poisons like Xenon be bled off is a major help as well.

Lots is possible with MSRs, but simple designs are aimed at either thermal or fast spectrum. Removing xenon is helpful. Not enough Xenon to power the ion engines though.
Title: Re: Power options for a Mars settlement
Post by: gospacex on 05/25/2017 08:24 pm
Quote
One more point.  Panels operate more efficiently when warm.  If they are on the ground, they'll benefit from surface temps that can reach into the 70's (f), and the ground warmth will continue into the night.

Perfect example of people not really understanding how cold Mars is.
Both Viking landers, during 6 years, never registered temperatures above -6 C.
The highest ever temperature _estimated_ (not directly measured) from orbital IR observations is something like +15 C (a black surface in a well wind-protected area on a calm day).

Perfect example of shooting one's mouth off.

https://mars.nasa.gov/mer/spotlight/20070612.html

"Temperatures in the shade for Spirit ranged from highs of about 35 degrees C. (95 degrees F.) in summer to lows of -90 degrees C. (-130 degrees F.)... Temperatures in the shade for Opportunity ranged from about 30 degrees C. (86 degrees F.) in summer to minus 80 degrees C. (-112 degrees F.) in winter. "

Interesting.
Actually, I remembered Vikings incorrectly. They only ever saw -17.2 C, not -6.
Wiki has this collated info on observed temperatures in "Climate of Mars" article:

"""
Differing in situ values have been reported for the average temperature on Mars,[20] with a common value being −55 °C (218 K; −67 °F).[21] Surface temperatures may reach a high of about 20 °C (293 K; 68 °F) at noon, at the equator, and a low of about −153 °C (120 K; −243 °F) at the poles.[22] Actual temperature measurements at the Viking landers' site range from −17.2 °C (256.0 K; 1.0 °F) to −107 °C (166 K; −161 °F). The warmest soil temperature estimated by the Viking Orbiter was 27 °C (300 K; 81 °F).[23] The Spirit rover recorded a maximum daytime air temperature in the shade of 35 °C (308 K; 95 °F), and regularly recorded temperatures well above 0 °C (273 K; 32 °F), except in winter.
"""

Curiosity at 4.5 degrees south latitude: +15 C tops.
https://www.nasa.gov/mission_pages/msl/multimedia/pia16913.html

So, average temp of -55 C, highs +20 C, Spirit saw +35 C.
Sorry, but I still think this is very cold, however I do need to raise max temps a bit in my understanding of it.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 05/25/2017 08:56 pm
"Temperatures in the shade for Spirit ranged from highs of about 35 degrees C. (95 degrees F.) in summer to lows of -90 degrees C. (-130 degrees F.)... Temperatures in the shade for Opportunity ranged from about 30 degrees C. (86 degrees F.) in summer to minus 80 degrees C. (-112 degrees F.) in winter. "

Raising the interesting question to my uninformed mind:  What is the temperature difference between "in the shade" and "not in the shade".  It seems the latter a touch more relevant to the discussion and pushing further from the -6 degree point.

Because it's the proper way to measure air temperatures.
https://www.weatherworksinc.com/temperature-measurement

In the case of this discussion, surface temp on the solar panel array itself would be far hotter than the air temp immediately above it- further increasing the efficiency of solar panels laid out on the ground.

Yes I understand that.  My poorly worded effort  :o  was to make the point in your 2nd paragraph.

What I really was asking about is if you had a Temps in the Sun graph for those rovers, what would the graph show.  Like there might be a 30 degree diff here on earth but I'd expect Mars would be different.  What's a typical (if there is one) delta there.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/26/2017 01:15 pm
Doesn't have to be space rated, just need contacts that don't mind the cold temps.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/26/2017 05:18 pm
Yeah, super cold at night (so thermal protection would be needed, IMHO), but nice and toasty for the panels during the day (at the equator). They'd probably reach 150 degrees or so to the touch, which is about right if the panels were here on Earth.
Could you specify if that's Fahrenheit or Centigrade you're talking about?
Quote from: sghill
IMHO, a thermal fluid backing could recirculate at night to provide thermal protection during the cold.  The fluid could be stored in a large enough tank and circulated with a high enough flow rate calculated to prevent the panels from dropping to a temperature cold enough to damage them.

Of you could just use space-rated panels....
The question of course is what does that do to the W/Kg rating of the panels?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/26/2017 05:37 pm
I'd have expected conduction to be a lot faster than diffusion.
At Degree level Physics heat conduction is modeled as the diffusion of virtual particles called phonons. It matters because that's how heat spreads out.  This is the process that underlies the simple High School level Physics description of conduction.

Quote from: alexterrell
Only if they're worried about Sodium coming into contact with water. If you're not, then Sodium is vastly superior to Lead in every respect.
Space reactor design has to include launch failure modelling and that include immersion in and entry of seawater, as it can act as a moderator, turning a sub critical reactor critical.

The US tried a Sodium cooled submarine reactor. It did not end well.  :(

Quote from: alexterrell
Quite a few Alpha class submarine lead cooled reactors have frozen solid, and in lead cooled reactors, the primary pump uses a significant chunk of the electricity generated.
True of any reactor that is not designed to rely on natural circulation. Fortunately I think the limit for that is around 300MW(t).

Quote from: alexterrell
Lots is possible with MSRs, but simple designs are aimed at either thermal or fast spectrum. Removing xenon is helpful. Not enough Xenon to power the ion engines though.
The Xenon isotope being removed is a major fission poison and one of the reasons why most reactors cannot run on natural Uranium.

Here' is the wikipedia article on "heat pipes".

https://en.wikipedia.org/wiki/Heat_pipe

And here is the article on "heat pumps"
https://en.wikipedia.org/wiki/Heat_pump

Here is some background on Kilopower and the KRUSTY reactor concept.
http://www.voss-associates.com/downloads/Small%20Nuclear%20Reactors.pdf

Reading these will make you better informed on some of the options for space nuclear power that are being worked on and how they work.
Title: Re: Power options for a Mars settlement
Post by: JasonAW3 on 05/26/2017 06:33 pm
Ok,  perhaps I'm oversimplifying things, but it appears that a major issue with Nuclear Reactors on Mars is simply how to dissipate the waste heat.

      I would suggest that a portion of that waste heat could be redirected to heating the colony proper, through a secondary, or even tertiary coolant loop.

      The rest, assuming that the reactor was placed in an area that is dryer than most, could be dissipated by sinking a secondary loop into the Martian regolith, several hundred or thousand feet in a sort of reverse geothermal heating.

      On the other hand, the waste heat could be redirected to a molten salt storage where much of the waste heat could be stored for both colony heating, and as a heat storage battery that could be used to run steam turbines to help utilize every bit of energy that can be scavenged from such reactors.

      Note; this same waste heat could be used for boring machines, or to melt and extract water as needed.

      I fully realize that there will always be some heat lost in a system like this, but it makes no sense to NOT try to use as much of the available heat as possible, while dissipating excess heat that cannot be used.

      If these comments cover ones previously made, please feel free to delete this message.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 05/26/2017 08:49 pm
Space reactor design has to include launch failure modelling and that include immersion in and entry of seawater, as it can act as a moderator, turning a sub critical reactor critical.

That only applies if the reactor is fuelled. If unfuelled, it doesn't matter what happens to it during a launch failure. Other than landing on someone's head, that is!

There are no particular regulatory difficulties in launching an unfuelled reactor. The difficulties come with launching the fuel. Launching the reactor and its fuel separately and bringing them together in LEO, or even on Mars, may simplify the regulatory problem considerably. The fuel could benefit from a specifically designed containment vessel, and could even be orbited via multiple launches.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 05/27/2017 01:16 am
Space reactor design has to include launch failure modelling and that include immersion in and entry of seawater, as it can act as a moderator, turning a sub critical reactor critical.

That only applies if the reactor is fuelled. If unfuelled, it doesn't matter what happens to it during a launch failure. Other than landing on someone's head, that is!

There are no particular regulatory difficulties in launching an unfuelled reactor. The difficulties come with launching the fuel. Launching the reactor and its fuel separately and bringing them together in LEO, or even on Mars, may simplify the regulatory problem considerably. The fuel could benefit from a specifically designed containment vessel, and could even be orbited via multiple launches.

Agreed.
As a crude example.  Launch the fuel in a used Crew Dragon.  It would have escape and landing capability.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/27/2017 06:33 am
That only applies if the reactor is fuelled. If unfuelled, it doesn't matter what happens to it during a launch failure. Other than landing on someone's head, that is!

There are no particular regulatory difficulties in launching an unfuelled reactor. The difficulties come with launching the fuel. Launching the reactor and its fuel separately and bringing them together in LEO, or even on Mars, may simplify the regulatory problem considerably. The fuel could benefit from a specifically designed containment vessel, and could even be orbited via multiple launches.
So you trade 1 payload for 2 payloads (reactor and fuel) and fueling the reactor in Leo or on Mars.

That said the fuel for the Lunar experiment packages left by Apollo was housed in a separate container which could act as its own reentry vehicle in the event of a launch accident.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/27/2017 11:39 am
A quick re-cap on (potentially) viable  energy systems for a Mars settlement ranked in terms of known complexity and ease of testability on Earth.

Photovoltaic solar cells

Bio gas from human and other waste (using either internal combustion or fuel cell conversion)

Fission reactor specifically Kilopower.

Geothermal heat from boreholes (assuming working fluid can be found and driving turbines or reciprocating engines)


Possible energy storage options on Mars, again in terms of availability, known problems and systems deployed.

Battery bank

Flywheels

Stored reactant fuel cells (possibly in a cycle storing electric power by back conversion of the reaction products into reactants)


Note. A Mars settlement is (by Earth standards) going to be energy poor.

It is therefor very likely that "waste" heat which on Earth would be dumped to the environment through cooling towers or radiators will  be recycled for settlement heating, crop heating and lower temperature mfg processes.

A note on human energy levels. Different studies put the energy needs per person between 5-60Kw/person.
NASA estimates artificial light farming will need an additional 42.5Kw/person to grow their individual food needs. Previous posters estimate dust storms will diminish surface illumination by 80%

Study on Mars Greehouses (possibly the one that inspired Musk to want to land one?)
 
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050182966.pdf
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/27/2017 12:20 pm
Bio gas goes way down the list.

About energy needed for food: Photosynthesis is inefficient, especially multicellular plants. Growing single celled food in vats (with energy coming from ISRU hydrogen, methane, and/or ammonia) for most of your calories (with plenty of typical multicellular plants for salad and side dishes, but a minority of calories) would be much more efficient than artificial light growing multicellular plants. You can also feed the monocellular food to farmed fish (or poultry) like we do on Earth for a treat, although that's less efficient than a vegan diet.

Human metabolism is just 100 Watts on average. We can do a lot better than 40,000 Watts for growing food.
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 05/27/2017 01:08 pm
Does solar thermal not make the list?
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/27/2017 02:54 pm

At Degree level Physics heat conduction is modeled as the diffusion of virtual particles called phonons. It matters because that's how heat spreads out.  This is the process that underlies the simple High School level Physics description of conduction.
So it is conduction. Just modelled as diffusion.

I looked through the heat tube section. It's only a passive design in the presence of gravity - so it would work on Mars. (You could use centripetal force - complex though. The article talks about capillary action but that will be size limited) 

Quote
Quote from: alexterrell
Quite a few Alpha class submarine lead cooled reactors have frozen solid, and in lead cooled reactors, the primary pump uses a significant chunk of the electricity generated.
True of any reactor that is not designed to rely on natural circulation. Fortunately I think the limit for that is around 300MW(t).
No. The ThorCon (MSR) primary loop pump is sized at 2.2MW for a reactor outputting 250MWe. So <1%. I think I've seen lead cooled designs with pumps that consume about 10% of the electrical output.   

The kilopower design is also sodium cooled.

Quote
Quote from: alexterrell
Lots is possible with MSRs, but simple designs are aimed at either thermal or fast spectrum. Removing xenon is helpful. Not enough Xenon to power the ion engines though.
The Xenon isotope being removed is a major fission poison and one of the reasons why most reactors cannot run on natural Uranium.

Here' is the wikipedia article on "heat pipes".

https://en.wikipedia.org/wiki/Heat_pipe

And here is the article on "heat pumps"
https://en.wikipedia.org/wiki/Heat_pump

Here is some background on Kilopower and the KRUSTY reactor concept.
http://www.voss-associates.com/downloads/Small%20Nuclear%20Reactors.pdf

Reading these will make you better informed on some of the options for space nuclear power that are being worked on and how they work.
I looked through the kilopower document. Quite impressive if they can get a fast reactor to work at such scale. That does need a "Highly Enriched Uranium core" which I assumes means 20% U235 - but the neutron economy may limit the burn-up.

They have a long way to go and some of the test results show low power. (Attaching stirling engines to heat sources is more difficult than you'd expect - and whilst low maintenance, they are not maintenance free).

The important question is what kind of certification does a space reactor need - especially if using HEU. The US or UK GDA process would kill the Kilopower concept - especially for a fast rector design using sodium coolant. However, the design looks promising for space applications, and should be suitable for Mars.

Have they made progress since those slides?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/27/2017 03:04 pm
Heat pipes don't need gravity.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/27/2017 04:20 pm
Does solar thermal not make the list?

Solar thermal needs a point source, the sun and tracking. Tracking needs maintenance. There are reasons why it is not common even at earth where maintenance is easy.

It breaks down with dust in the air as the light gets scattered. So not suitable for power production during dust storms. It could have applications for industrial process heat when shutting down during dust storms is acceptable. Not good for power production.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/27/2017 07:07 pm
Still makes more sense than biogas.
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/27/2017 07:12 pm
Does solar thermal not make the list?

Solar thermal needs a point source, the sun and tracking. Tracking needs maintenance. There are reasons why it is not common even at earth where maintenance is easy.

It breaks down with dust in the air as the light gets scattered. So not suitable for power production during dust storms. It could have applications for industrial process heat when shutting down during dust storms is acceptable. Not good for power production.

Solar thermal also suffers from repeated thermal cycling (daily or sol-ly) -- could be exacerbated on Mars where night temps plummet to cryo range.  One of those ideas that works better in theory than practice, for very mundane engineering reasons.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/27/2017 07:50 pm
Heat pipes don't need gravity.
They need a method of getting the liquid from the cold point to the hot point. Capillary action might work for microchip cooling, but for MW scale?
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 05/27/2017 07:52 pm
A quick re-cap on (potentially) viable  energy systems for a Mars settlement ranked in terms of known complexity and ease of testability on Earth.

If you want to think out the box, and you use SEP to go from Earth to Mars orbit, then Space Solar Power with lasers would be an option.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/27/2017 07:57 pm
Heat pipes don't need gravity.
They need a method of getting the liquid from the cold point to the hot point. Capillary action might work for microchip cooling, but for MW scale?
Yup, it works for MW scale. That's what a heat pipe is.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 05/27/2017 08:14 pm
A quick re-cap on (potentially) viable  energy systems for a Mars settlement ranked in terms of known complexity and ease of testability on Earth.

If you want to think out the box, and you use SEP to go from Earth to Mars orbit, then Space Solar Power with lasers would be an option.

This would be fine in the general Mars thread and has been discussed ad-infinitum, but unless Elon trashes the ITS completely this summer, it's not a SpaceX approach. 
My problem with SEP is the really, really small thrust even with megawatts of solar panels resulting in long transit times, another SpaceX no-no.  And don't even mention Space Solar to the guy who runs SpaceX.  :)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/27/2017 08:19 pm
Does solar thermal not make the list?
It would be simpler to mfg out of local materials and can be made scratch resistant but other posters complained it was not viable due to the high level of atmospheric dust.  :(

The atmosphere of Mars is not something that can be fixed in a timescale less then centuries (and probably Milenia  :( )

I note that on clear days concentrated solar thermal systems can generate high temperatures as in the NRL's "Solchem" reversible solar energy storage system studies in the early 80's.

An interesting question would be wheather or not "non imaging" concentrator systems (with concentration ratios in the 1000x) would also be degraded by diffuse light.
Bio gas goes way down the list.
It has no technical issues, can scale up depending on the number of settlers (and farm animals or fish) and a large number of people already use it cooking and lighting (through incandescent gas mantles, which are fairly low tech but fairy bright)
Quote from: Robotbeat
About energy needed for food: Photosynthesis is inefficient, especially multicellular plants. Growing single celled food in vats (with energy coming from ISRU hydrogen, methane, and/or ammonia) for most of your calories (with plenty of typical multicellular plants for salad and side dishes, but a minority of calories) would be much more efficient than artificial light growing multicellular plants. You can also feed the monocellular food to farmed fish (or poultry) like we do on Earth for a treat, although that's less efficient than a vegan diet.

Human metabolism is just 100 Watts on average. We can do a lot better than 40,000 Watts for growing food.
I'm unaware of any system that does this (outside "The Matrix" that is  :) ) . I think there was some work on bacteria to eat oil sludge done in the 70's and 80's but it went nowhere (and oil sludge is going to be in short supply on Mars).  IOW it's TRL is 0.

The nearest I am aware of is Quorn, which AFAIK is based on fungi. Quarn is pretty versatile but it's not single celled.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/27/2017 08:39 pm
A quick re-cap on (potentially) viable  energy systems for a Mars settlement ranked in terms of known complexity and ease of testability on Earth.

If you want to think out the box, and you use SEP to go from Earth to Mars orbit, then Space Solar Power with lasers would be an option.

This would be fine in the general Mars thread and has been discussed ad-infinitum, but unless Elon trashes the ITS completely this summer, it's not a SpaceX approach. 
My problem with SEP is the really, really small thrust even with megawatts of solar panels resulting in long transit times, another SpaceX no-no.  And don't even mention Space Solar to the guy who runs SpaceX.  :)
SpaceX considered SEP for ITS. And there are ways to get faster transits using ambitious SEP approaches, but I completely agree with respect to beamed power.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/27/2017 08:55 pm
I'm unaware of any system that does this (outside "The Matrix" that is  :) ) . I think there was some work on bacteria to eat oil sludge done in the 70's and 80's but it went nowhere (and oil sludge is going to be in short supply on Mars).  IOW it's TRL is 0.


If we want to continue this discussion we should move to another thread. But protein for animal feed from methane is ready for commercial use or nearly. It can also be modified for human consumption. From the Financial Times.

https://www.ft.com/content/f520cebc-dbe5-11e6-9d7c-be108f1c1dce

Quote
It is possible that one day methane-based protein could be consumed directly by humans. “These kinds of products could end up in human protein bars eventually,” Mr Shaw believes.

Both Mr Shaw and Mr Busch-Larsen have tried their own food but neither plans to enter the human market as there could be considerable public aversion. “You would have to modify the process,” says Mr Busch-Larsen. “It is not for tomorrow.”

I am sure future processes can make more than protein bars for human consumption.

Edit: I am sure this process will be more energy efficient than producing artificial light for greenhouse plants.
Title: Re: Power options for a Mars settlement
Post by: Dao Angkan on 05/27/2017 09:47 pm
Calysta have been in contact with SpaceX about it. At least at first I would expect solar with Methane powered generators as back up. Maybe it will be a Methane based economy on Mars.

https://www.newscientist.com/article/2112298-food-made-from-natural-gas-will-soon-feed-farm-animals-and-us/

Quote
The technology might one day also feed explorers of other planets. For instance, SpaceX head Elon Musk’s plans for Mars exploration include generating methane and oxygen for making rocket fuel. Some could be used to make food, too. “We have been in touch with SpaceX,” says Shaw.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/27/2017 09:54 pm
CO/O2 makes more sense for general energy storage than methane, as methane requires water and also has extra losses from the Sabatier reaction step.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/27/2017 09:55 pm
It is possible that one day methane-based protein could be consumed directly by humans. “These kinds of products could end up in human protein bars eventually,” Mr Shaw believes.

Both Mr Shaw and Mr Busch-Larsen have tried their own food but neither plans to enter the human market as there could be considerable public aversion. “You would have to modify the process,” says Mr Busch-Larsen. “It is not for tomorrow.”
So not TRL0, maybe TRL1. This is not yet ready for sale as animal feed. It's decades from development for humans on Earth.  It puts yet another fairly major development project in the critical path to setting up a settlement. All grounds for forgetting about it entirely.
Quote from: guckyfan
Edit: I am sure this process will be more energy efficient than producing artificial light for greenhouse plants.
That's on topic for this thread. :) If it can be made to work it should be possible to engineer a relatively small package to do this provide you have a source of Methane.

But it's just so complex.  :( People have been looking at growing food in space for decades but they have been growing crops for 1000s of years and KISS is usually a pretty good idea to follow.

In principle the lowest power option is natural light. The joker are the dust storms. Month long dust storms are simply not a feature of Earth agriculture. But all the stuff about how you cope with this stuff is all OT for this thread.

From the power PoV the key point is depending on what your baseline is (5-60Kw/person) it increases your power budget by 2/3s at the high end to a factor of 9 at the low end.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/27/2017 10:10 pm
No, it's already cleared for animal feed in Europe, specifically fish feed.

It's not decades from human consumption, it just needs a few years and sufficient demand. No real demand on Earth for direct human consumption here as we have massively automated agriculture of enormous acreage.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/28/2017 02:16 am
A quick re-cap on (potentially) viable  energy systems for a Mars settlement ranked in terms of known complexity and ease of testability on Earth.

If you want to think out the box, and you use SEP to go from Earth to Mars orbit, then Space Solar Power with lasers would be an option.

This would be fine in the general Mars thread and has been discussed ad-infinitum, but unless Elon trashes the ITS completely this summer, it's not a SpaceX approach. 
My problem with SEP is the really, really small thrust even with megawatts of solar panels resulting in long transit times, another SpaceX no-no.  And don't even mention Space Solar to the guy who runs SpaceX.  :)
SpaceX considered SEP for ITS. And there are ways to get faster transits using ambitious SEP approaches, but I completely agree with respect to beamed power.

Was there any more information beyond GS's "yeah we're looking at that too" in a Q&A session?

And if yes, what type of SEP did they indicate they'd use?

Title: Re: Power options for a Mars settlement
Post by: DAZ on 05/28/2017 02:46 am
This would seem like a natural to go to with ITS.  It would launch like crazy, around the Mars window but the question becomes what do they do for the other 16 – 18 months out of the cycle?  It would seem a natural to launch cargo that is not time constraint like people.  Precisely when they launch wouldn’t matter, it could just spiral up and wait for the appropriate window.  It would seem that there’d be lots of cargo like this for the 1st few decades.
As for transferring the power, it would seem to be better to use RF instead of lasers.  For lasers, you are primarily changing one light source for another and if you’re trying to avoid problems with dust you don’t seem to be escaping the problem this way.  Additionally, the ground receiver would seem to be easier to construct and deploy with fewer problems with dust/temperature swings.  After each tug releases its cargo it could then make its way to areostationary orbit. 

They would then become power satellites with some having added packages to be communication relay satellites.  For the communication side, this could be a laser to earth with an additional laser to Mars surface.  There would additionally be an RF link not only as a backup but to relay for ground entities when they move out of line of sight of the master ground stations.  It would still need to occasionally use their ion engines for station keeping.  As power satellites, they would have to slave their frequency off of one of the satellites so they would be phase locked together so as not to interfere with each other when providing power to the same ground location.

From reading this thread and others it would seem that the early Mars colony would be primarily limited to its growth by power constraints followed by certain specialized pieces of equipment.  So it would seem the question it is not what is the best way to get power and supplies but maximizing all available options.
Title: Re: Power options for a Mars settlement
Post by: Oli on 05/28/2017 08:31 am
This would be fine in the general Mars thread and has been discussed ad-infinitum, but unless Elon trashes the ITS completely this summer, it's not a SpaceX approach. 
My problem with SEP is the really, really small thrust even with megawatts of solar panels resulting in long transit times, another SpaceX no-no.  And don't even mention Space Solar to the guy who runs SpaceX.  :)

SpaceX' "obsession" with fast transfer is a mystery to me, it's irrelevant for building a colony.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/28/2017 11:08 am
This would be fine in the general Mars thread and has been discussed ad-infinitum, but unless Elon trashes the ITS completely this summer, it's not a SpaceX approach. 
My problem with SEP is the really, really small thrust even with megawatts of solar panels resulting in long transit times, another SpaceX no-no.  And don't even mention Space Solar to the guy who runs SpaceX.  :)

SpaceX' "obsession" with fast transfer is a mystery to me, it's irrelevant for building a colony.
It does matter if you want to limit radiation exposure, which is very serious during the deep space trip.

Setting up a settlement is likely to need a lot of cargo shipping.  If those cargo transports can be sent without crews (either by taking on a crew at Mars or full automation to land it) then they could be sent on slower trajectories.
Title: Re: Power options for a Mars settlement
Post by: Oli on 05/28/2017 11:49 am
This would be fine in the general Mars thread and has been discussed ad-infinitum, but unless Elon trashes the ITS completely this summer, it's not a SpaceX approach. 
My problem with SEP is the really, really small thrust even with megawatts of solar panels resulting in long transit times, another SpaceX no-no.  And don't even mention Space Solar to the guy who runs SpaceX.  :)

SpaceX' "obsession" with fast transfer is a mystery to me, it's irrelevant for building a colony.
It does matter if you want to limit radiation exposure, which is very serious during the deep space trip.

Setting up a settlement is likely to need a lot of cargo shipping.  If those cargo transports can be sent without crews (either by taking on a crew at Mars or full automation to land it) then they could be sent on slower trajectories.

1) Settlers will only experience one trip in one direction, how's radiation exposure an issue?
2) ITS won't return within a single synodic cycle. SEP can easily return within 2 synodic cycles.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/28/2017 12:39 pm
2) ITS won't return within a single synodic cycle. SEP can easily return within 2 synodic cycles.

Return in a single synodic cycle is the goal of fast transfer. Looking through the presentation I read it as they can do fast return with 200t of payload with 6km/s delta-v available. Maybe a little more payload in good windows.

Cost for cargo is calculated on 450t cargo. I read the 450t max cargo as slow and no return in 1 one synodic cycle. It makes sense to me. Sending up to 450t slow is efficient compared to 200t fast. This will affect propellant production on Mars positively as they need to produce half of the return propellant for the same amount of cargo. The cost slide of the presentation shows a small gain in cost per flight after 6 flights so it makes a lot of sense.

Opposed to that sending crew fast makes sense. Going slow does not allow for more passengers, the opposite would be true. The crew ITS can return in one synodic cycle and fly twice as many times as cargo.

Title: Re: Power options for a Mars settlement
Post by: Welsh Dragon on 05/28/2017 03:19 pm
<snip>
1) Settlers will only experience one trip in one direction, how's radiation exposure an issue?
<snip>
That trip is instantaneous and does not result in any radiation exposure?
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/28/2017 03:43 pm
That trip is instantaneous and does not result in any radiation exposure?

As a fraction of permissible life time exposure the answer is almost yes.
Title: Re: Power options for a Mars settlement
Post by: Oli on 05/28/2017 03:48 pm
As for one-synod return (not the same as fast transfer btw.), it's a combination of factors that make me think it's not desirable: Reduced cargo, much higher propellant production/storage requirements on Mars, Earth reentry velocities far above 12.5km/s (a braking burn can reduce it to ~12.5km/s in some opportunities, but again, more prop), short period of time to refurbish the entire fleet of ITS on Earth respectively Mars.

That trip is instantaneous and does not result in any radiation exposure?
   

"Risk-averse NASA" is willing to send astronauts on 1000 days trips to Mars in unprotected habitats. Surely Mars colonists can tolerate a bit of increased cancer risk due to 200-300 days in deep space? I suggest people worry about colonists having to live and reproduce in 0.38g, because it's completely uncertain whether that is actually feasible.
Title: Re: Power options for a Mars settlement
Post by: DarkenedOne on 05/28/2017 03:50 pm
This would be fine in the general Mars thread and has been discussed ad-infinitum, but unless Elon trashes the ITS completely this summer, it's not a SpaceX approach. 
My problem with SEP is the really, really small thrust even with megawatts of solar panels resulting in long transit times, another SpaceX no-no.  And don't even mention Space Solar to the guy who runs SpaceX.  :)

SpaceX' "obsession" with fast transfer is a mystery to me, it's irrelevant for building a colony.
It does matter if you want to limit radiation exposure, which is very serious during the deep space trip.

Setting up a settlement is likely to need a lot of cargo shipping.  If those cargo transports can be sent without crews (either by taking on a crew at Mars or full automation to land it) then they could be sent on slower trajectories.

1) Settlers will only experience one trip in one direction, how's radiation exposure an issue?
2) ITS won't return within a single synodic cycle. SEP can easily return within 2 synodic cycles.
Its called the Linear no-threshold model.  Basically says that no dose of ionizing radiation is too small. 
Title: Re: Power options for a Mars settlement
Post by: DAZ on 05/28/2017 04:00 pm
Discussed ad nausea and here

https://forum.nasaspaceflight.com/index.php?topic=41309.0

And here

https://forum.nasaspaceflight.com/index.php?topic=41562.0

And off-topic.  If you talking about power options (not people or animals) for Mars settlement you're talking about cargo that should be relatively unaffected by radiation or transit times.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/28/2017 05:46 pm
Well, using single synod transfers (for people-carrying ITSes) is SpaceX's plan. So that's what we've got to work with.

Fast transfers help enable single synod transfers.

Otherwise you spend twice as much on amortization of the BFS, which is already by far the largest cost of the ITS architecture.
Title: Re: Power options for a Mars settlement
Post by: DAZ on 05/28/2017 06:07 pm
Well, using single synod transfers (for people-carrying ITSes) is SpaceX's plan. So that's what we've got to work with.

Fast transfers help enable single synod transfers.

Otherwise you spend twice as much on amortization of the BFS, which is already by far the largest cost of the ITS architecture.

Yes, you must get the ITS back as quick as practical for multiple reasons.  The ITS is required to get people to Mars and back.  The ITS can also carry cargo to Mars.  It is not necessary for the ITS to go all the way to Mars in order to deliver cargo to Mars.  The ITS can only launch to Mars as stated during the synod to Mars.  The actual window is short but the lead-up time to get everything into orbit and fueled could add up to about 4 to 5 months.  So the rest of the time you have the booster and any ITSs that have been completed sitting on the ground doing (at least as far as the Mars campaign is concerned) nothing.  As far as amortization goes it would seem to make much more sense to launch any other cargo that is not time sensitive during this downtime of approximately 16 – 18 months.  This would seem to maximize the ITS and thus reduce the cost of everything going to Mars.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/28/2017 06:17 pm
Technically, there are different classes of orbits that allow you to launch just about any time you want, although it may take years to get to Mars.Ballistic transfers could allow you to push cargo to Mars, then catch it on the other end.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/29/2017 06:57 am
Technically, there are different classes of orbits that allow you to launch just about any time you want, although it may take years to get to Mars.Ballistic transfers could allow you to push cargo to Mars, then catch it on the other end.
True, and could probably increase the payload to Mars if that were necessary.

In the context of this thread would would that need to be to support some of the power options suggested.

Looking over the original presentation I think they expect ITS to make 12 journeys to Mars and cost $200m with a $40m refurb cost, about $560k/passenger for a 100 passenger vessel.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/29/2017 07:15 am
Looking over the original presentation I think they expect ITS to make 12 journeys to Mars and cost $200m with a $40m refurb cost, about $560k/passenger for a 100 passenger vessel.

The proposed ticket price was much lower. I guess revenue supported by significant cargo that goes along in the cargo bay.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/29/2017 01:57 pm
Looking over the original presentation I think they expect ITS to make 12 journeys to Mars and cost $200m with a $40m refurb cost, about $560k/passenger for a 100 passenger vessel.

The proposed ticket price was much lower. I guess revenue supported by significant cargo that goes along in the cargo bay.
I'd say we're a decade from a first flight to Mars by an ITS. At this point most of those numbers will be subject to change.

AFAIK no one anywhere has ever built flight weight composite cryogenic tanks at this size for multiple reuse.  The soonest that will change will be when the XS-1 starts flying around 2019/2020.

Right now the biggest ones I am aware of were the COPV's on the Shuttle for fuel cell reactants. 

The biggest cryogenic tanks that have been reused are the LOX ones on the F9 booster stage, but they are AlLi alloy. 

There is AFAIK no data to predict the long term survival of a large composite cryo tank. I'm very pleased SX have already started tests on one.
Title: Re: Power options for a Mars settlement
Post by: Oli on 05/30/2017 11:09 pm
Well, using single synod transfers (for people-carrying ITSes) is SpaceX's plan. So that's what we've got to work with.

Source?

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/31/2017 12:01 pm
Well, using single synod transfers (for people-carrying ITSes) is SpaceX's plan. So that's what we've got to work with.

Source?
Like every other time, from SpaceX's Mars presentation.
http://www.spacex.com/sites/spacex/files/mars_presentation.pdf
Title: Re: Power options for a Mars settlement
Post by: Oli on 06/01/2017 01:50 pm
Well, using single synod transfers (for people-carrying ITSes) is SpaceX's plan. So that's what we've got to work with.

Source?
Like every other time, from SpaceX's Mars presentation.
http://www.spacex.com/sites/spacex/files/mars_presentation.pdf

It says nothing about single synod trips, only fast transfers to Mars. Those are obviously not the same thing. The return leg is the problematic part.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/01/2017 04:05 pm
Elon Musk has mentioned many times that he wants the spacecraft back in 1 synod for reuse. It is also indirectly in the IAC presentation. He made his calculation for 12 reuses. Which would mean operational life of ITS of 50 years if reused only every other synod.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 06/02/2017 12:40 am
At least at first I would expect solar with Methane powered generators as back up. Maybe it will be a Methane based economy on Mars.
CO/O2 makes more sense for general energy storage than methane, as methane requires water and also has extra losses from the Sabatier reaction step.

At least in the early days, you'd be crazy not to use methalox generators for back-up power supply as you'd have tonnes of the stuff available for use as propellant. Though this may be more as an emergency, last-resort kind of back-up as you are going to a great deal of effort to produce this methalox for a reason! Even in the early days, it may be worth considering something else for more regularly anticipated back-up needs, such as at night if you're relying on solar power. For electricity storage, batteries are the obvious alternative, but there may be opportunities for heat storage.

A distinction will probably have to be made for the main base/colony and any satellite installations, including sensor or communications points and longer-distance vehicles. At least for the smaller such installations this is almost certainly going to be solar/battery.

Of course, any colony is going to want local production of power and storage at some point. CO/O2 has the benefit of being straightforward and utilising a ubiquitous resource. But what would be the easiest battery technology to produce on Mars?
Title: Re: Power options for a Mars settlement
Post by: raketa on 06/02/2017 01:00 am
Elon Musk has mentioned many times that he wants the spacecraft back in 1 synod for reuse. It is also indirectly in the IAC presentation. He made his calculation for 12 reuses. Which would mean operational life of ITS of 50 years if reused only every other synod.

In my opinion to utilize build ITS:
1/ITS will be coming back in 1 synod and use for LEO, GEO and Moon deliveries, then refurbish and use  for next trip Mars.
2/In a period of Marsion fleet away, ITS dedicated to earth service has to fly more often.
3/Maybe just brand new ITS(most advance) will go to Mars and then will be used for Earth service, as second hand ITS.
4or maybe proven ITS only will be refurbish and sent to Mars.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/02/2017 12:39 pm
Elon Musk has mentioned many times that he wants the spacecraft back in 1 synod for reuse. It is also indirectly in the IAC presentation. He made his calculation for 12 reuses. Which would mean operational life of ITS of 50 years if reused only every other synod.
Good point. When you work out  all the transit times even a fairly modest reuse runs a very long time scale.

Just a factor for the scale for settlement.

A fleet of 2 vessels can land a 1000 people in 5 synods (or ten if they are being launched every other synod).

Unless SX build a substantial fleet quickly this plan will land Elon Musk and his entourage on Mars in a reasonable space of time. And that's about it.

People might like to consider what is the minimum size of settlement that can support itself and continue to expand and have enough resources to accommodate the arrival of new settlers.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/02/2017 01:38 pm
SpaceX would need to perfect reuse AND have a huge spaceship assembly line, as busy as those used for airliners.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/02/2017 07:29 pm
SpaceX would need to perfect reuse AND have a huge spaceship assembly line, as busy as those used for airliners.
I think the mfg line could be quite small, as long as they can mfg a pair each cycle to grow the fleet. The other problem is the refurb line. That will also have to grown and for all vehicles to be useful on each (or every other) cycle
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 06/02/2017 09:19 pm
SpaceX would need to perfect reuse AND have a huge spaceship assembly line, as busy as those used for airliners.
I think the mfg line could be quite small, as long as they can mfg a pair each cycle to grow the fleet. The other problem is the refurb line. That will also have to grown and for all vehicles to be useful on each (or every other) cycle
Other factors to contemplate:

 - it's unknown how many (hopefully uncrewed!) ITS vehicles are lost while they get ITS-scale mars EDL working reliably.

 - I haven't see estimates of how many uncrewed-ITS-loads will be required to ship the ISRU fuel plant and everything it depends on (solar arrays, etc.) before the first ITS can refuel on the surface and come back, but it seems likely that >1 ITS-load is needed to send the capability to refuel 1 ITS/cycle at Mars, which means that  some of the ships will not be coming back right away.

I think the second factor nudges towards a higher build rate.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/02/2017 10:13 pm
WRT to this actual thread title this seems quite relevant.


http://large.stanford.edu/courses/2010/ph240/cook2/

It's a very interesting description of what a  biogas system would need.

Title: Re: Power options for a Mars settlement
Post by: DAZ on 06/03/2017 01:41 am
Even though, the ITS will eventually be able to deliver the most cargo ever seriously conceived to Mars, it's hard to see how the ITS system is going to get all the cargo that is needed for a self-sustaining Mars society if the only way to get cargo to Mars is by the ITS going to Mars and then returning.  This is even more difficult to visualize when the primary constraint for how many ships can return, and when, is primarily going to be the availability of power on Mars.  Building more ships on earth would obviously help alleviate this problem some but is mostly just kicking the problem down the road.

It is much easier to see how this could take place if you decouple every ITS flight from having to go to Mars in order to deliver cargo to Mars.  Only going all the way to Mars and returning ignores that the ITS can deliver an absolutely huge amount of cargo into Earth orbit.  In fact, just delivering the cargo to orbit with the systems required to make a one-way trip to Mars the ITS system can probably deliver much more cargo to Mars that way than by taking it all the way to Mars and returning.

Delivering much of this cargo this way, especially the power components would allow for more of the ITS flights to return from Mars sooner.  SpaceX is smart and undoubtedly knows this.  Just because they haven’t discussed the other aspects of how the ITS system can support getting materials to Mars doesn’t mean they aren’t considering it.  They have been primarily talking about the hard part of getting people (and the supplies immediately need) to Mars and back.

If you look a little further down the road you’ll see the problem of mining and refining.  On earth, these are referred to as heavy industries for a very good reason.  It will probably be decades before there are any serious mining and refining (other than for things like water) on Mars.  It will take decades of exploring justifying possible sources of much of the ore.  Small-scale manufacturing plants, on the other hand, could happen very soon if they just had the source of raw materials.  This would allow them to construct what they would need on a relatively short timeframe as opposed to 2 to 6 years to have something sent from Earth.  Things like bearings and cutting teeth for Mars excavating equipment can probably be anticipated but what about that pesky little return spring (or other such items) for the sewage pump.  Providing duplicate parts for every conceivable item (let alone planning what those items would be) is just not practical.  But if you have the raw elements available it would be possible to make just about any part in a small-scale production.  This is something else the ITS could help ship to Mars in between its trips to Mars.  They would need just about every common element in the periodic table.

The whole problem becomes very much simpler if the ITS doesn’t have to go to Mars to deliver most of the cargo to Mars.
Title: Re: Power options for a Mars settlement
Post by: raketa on 06/03/2017 02:37 am
Even though, the ITS will eventually be able to deliver the most cargo ever seriously conceived to Mars, it's hard to see how the ITS system is going to get all the cargo that is needed for a self-sustaining Mars society if the only way to get cargo to Mars is by the ITS going to Mars and then returning.  This is even more difficult to visualize when the primary constraint for how many ships can return, and when, is primarily going to be the availability of power on Mars.  Building more ships on earth would obviously help alleviate this problem some but is mostly just kicking the problem down the road.

It is much easier to see how this could take place if you decouple every ITS flight from having to go to Mars in order to deliver cargo to Mars.  Only going all the way to Mars and returning ignores that the ITS can deliver an absolutely huge amount of cargo into Earth orbit.  In fact, just delivering the cargo to orbit with the systems required to make a one-way trip to Mars the ITS system can probably deliver much more cargo to Mars that way than by taking it all the way to Mars and returning.

Delivering much of this cargo this way, especially the power components would allow for more of the ITS flights to return from Mars sooner.  SpaceX is smart and undoubtedly knows this.  Just because they haven’t discussed the other aspects of how the ITS system can support getting materials to Mars doesn’t mean they aren’t considering it.  They have been primarily talking about the hard part of getting people (and the supplies immediately need) to Mars and back.

If you look a little further down the road you’ll see the problem of mining and refining.  On earth, these are referred to as heavy industries for a very good reason.  It will probably be decades before there are any serious mining and refining (other than for things like water) on Mars.  It will take decades of exploring justifying possible sources of much of the ore.  Small-scale manufacturing plants, on the other hand, could happen very soon if they just had the source of raw materials.  This would allow them to construct what they would need on a relatively short timeframe as opposed to 2 to 6 years to have something sent from Earth.  Things like bearings and cutting teeth for Mars excavating equipment can probably be anticipated but what about that pesky little return spring (or other such items) for the sewage pump.  Providing duplicate parts for every conceivable item (let alone planning what those items would be) is just not practical.  But if you have the raw elements available it would be possible to make just about any part in a small-scale production.  This is something else the ITS could help ship to Mars in between its trips to Mars.  They would need just about every common element in the periodic table.

The whole problem becomes very much simpler if the ITS doesn’t have to go to Mars to deliver most of the cargo to Mars.
The first crew arrives without the option to return back to Earth until fuel and power infrastructure will be built. It could be 2-6-8years, every two-year they will new get cargo and people to help them base on progress and issue to finish this basic task. After infrastructure builds, ITS will start to return back to Earth and maybe return in the same synod.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/03/2017 02:02 pm
The first crew arrives without the option to return back to Earth until fuel and power infrastructure will be built. It could be 2-6-8years, every two-year they will new get cargo and people to help them base on progress and issue to finish this basic task. After infrastructure builds, ITS will start to return back to Earth and maybe return in the same synod.
Which suggests setting up a settlement will be a very prolonged process. :(

My instinct is food, ISRU and the power needed to run it will be the biggest priorities for cargo.

Which raises the question what's the power needed to generate a load of propellant to get back to Earth?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/03/2017 03:13 pm
A Megawatt of average power for 1 synod per returning ITS.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/05/2017 06:45 am
A Megawatt of average power for 1 synod per returning ITS.
Although technically I suppose the goal would be for most people to stay on Mars and send the ship(s) back empty for reuse.

Obviously that gives no "life boat" option if anything happens  :(

To put that in perspective that's in the range of power generated by the gases collected from landfill sites, which can last decades.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/06/2017 06:58 am
A Megawatt of average power for 1 synod per returning ITS.
Although technically I suppose the goal would be for most people to stay on Mars and send the ship(s) back empty for reuse.

Obviously that gives no "life boat" option if anything happens  :(

To put that in perspective that's in the range of power generated by the gases collected from landfill sites, which can last decades.

The thing about lifeboats is the launch windows.  It's not like "OMG we have to bug out go! go! go! go! go!".  It's more like "We have a problem, and the launch window to leave opens at about the same time that supplies from Earth are due.  And leaving means we still have to endure transit."

In most cases, it's easier and safer to "fail forward" - meaning to send rescue supplies. Earth has a lot of resources, and can afford to send fast ships.  An "emergency cargo ship" can be built that is all fuel, small cargo hold, and maybe no ability to come back.  So something that starts out like ITS, but has an end mass on the surface of say, 1 ton.

Wait - this is the power options thread.  How did we get here?

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/06/2017 11:40 am
How efficient is methalox as an energy storage system?  If the colony depends on solar for its power, and needs to be able to survive low solar periods during dust storms, and has an important manufacturing base to produce methalox, can this serve as their bad times battery?  In particular, as we can expect the waste heat from the methalox combustion to be useful as well, the 'efficiency' might be 50% or more? 
There is a large energy loss in gas compression, I believe, and hydrogen production also loses energy, so I wonder about the overall energy requirements.


Title: Re: Power options for a Mars settlement
Post by: envy887 on 06/06/2017 08:17 pm
Synods, supplies, and launch windows are off topic.

Let's stick with power options please.

If we need a new subject in this thread, let's talk about the million reasons why DC will be the chosen power delivery system for mars wiring.

https://www.mnn.com/green-tech/research-innovations/stories/the-home-of-tomorrow-will-run-on-direct-current

Is Mars cold enough for high-temp superconductors to make sense? Because if not, power delivery will be AC even if local use is DC.
Title: Re: Power options for a Mars settlement
Post by: whitelancer64 on 06/06/2017 08:27 pm
Synods, supplies, and launch windows are off topic.

Let's stick with power options please.

If we need a new subject in this thread, let's talk about the million reasons why DC will be the chosen power delivery system for mars wiring.

https://www.mnn.com/green-tech/research-innovations/stories/the-home-of-tomorrow-will-run-on-direct-current

Is Mars cold enough for high-temp superconductors to make sense? Because if not, power delivery will be AC even if local use is DC.

Mars is not quite cold enough, at least not all the time (daytime temps can get well above 0 C), for the record highest temperature superconductor - which is -70 C for Hydrogen Sulfide at very high pressure (150 gigapascals).
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 06/06/2017 11:36 pm
How efficient is methalox as an energy storage system?  If the colony depends on solar for its power, and needs to be able to survive low solar periods during dust storms, and has an important manufacturing base to produce methalox, can this serve as their bad times battery?  In particular, as we can expect the waste heat from the methalox combustion to be useful as well, the 'efficiency' might be 50% or more? 
There is a large energy loss in gas compression, I believe, and hydrogen production also loses energy, so I wonder about the overall energy requirements.

About 36% efficiency, apparently (http://blogs.worldwatch.org/revolt/is-%E2%80%9Crenewable-methane%E2%80%9D-energy-storage-an-efficient-enough-option/). Batteries are about 99%! But if you have tonnes of methalox propellant available, it would make an emergency power source.

One way to survive low - not zero - solar power supplies during dust storms would be to switch off energy usage (shutting down the methalox production facilities, for instance).
Title: Re: Power options for a Mars settlement
Post by: spacenut on 06/06/2017 11:58 pm
If they make 10 cargo trips to Mars for colonial building materials such as solar power, mining, making CH4, making Lox, etc, for every one trip of colonists.  It seems to me they are going to have to make at least 10-12 ITS flights per synod.  So, it seems the manufacturing will have to be at least minimum 5 per year, say 6.  The fleet could build up over time. 

The subject is power.  It will take at least twice as much solar power as battery storage, since power is going to have to be used around the clock.  Over the long haul, nuclear is probably the only option. 

An aircraft carrier is self sufficient except for food and aviation fuel.  They are probably going to have to have power at night to keep the greenhouses producing, not just for fuel manufacturing.  Mars is cold, so heating will be required, especially at night.  An aircraft carrier can go 50 years on it's supply of uranium or plutonium, and they use a lot of power. 

Small light weight nuclear power plants, say 20 tons, can be installed at a distance from the colony.  Excess heat can be used to melt ice for water and rocket fuel production. 
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/08/2017 12:33 pm
Mars is not quite cold enough, at least not all the time (daytime temps can get well above 0 C), for the record highest temperature superconductor - which is -70 C for Hydrogen Sulfide at very high pressure (150 gigapascals).
Not really practically useful unless you could encase wires of it in an astonishingly strong sheath that would exert enough pressure to maintain the SC state. Not really very viable.

OTOH SC at 203K is intriguing.

I wonder wheather the existence of SC at this (relatively) high temperature strengthens or weakens existing SC theories?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/08/2017 02:00 pm
Mars is not quite cold enough, at least not all the time (daytime temps can get well above 0 C), for the record highest temperature superconductor - which is -70 C for Hydrogen Sulfide at very high pressure (150 gigapascals).
Not really practically useful unless you could encase wires of it in an astonishingly strong sheath that would exert enough pressure to maintain the SC state. Not really very viable.

OTOH SC at 203K is intriguing.

I wonder wheather the existence of SC at this (relatively) high temperature strengthens or weakens existing SC theories?
Getting off topic, but the recent very high temperature superconductor is actually understood as a "conventional" superconductor using the relatively easy-to-understand BCS (Bardeen–Cooper–Schrieffer) theory based on phonon coupling of the Cooper pair electrons. As one electron passes through the lattice of atoms, the positively charged centers of the atoms are attracted and move toward the electron, but by the time they've moved, the first electron has passed. A second electron "sees" these positive cores as an attractive force, causing it to be pulled along in the wake of the first electron. Basically, you have two electrons coupled to on another in such a way that separating them requires, like the energy levels in an atom, a certain minimum energy threshold (that minimum threshold determines the critical temperature and current), not just any small perturbation. This is unlike the "high temperature" superconductors (i.e. Cuprates such as YBCO that superconduct at liquid nitrogen temperatures) which are coupled by a different and lesser understood mechanism (d-wave?).

Metallic hydrogen is supposed to be a conventional superconductor at room temperatures since the ion cores are very light and so move more and couple the Cooper pairs more strongly. You can think of this hydrogen sulfide superconductor as basically a way to access the inherent Superconductivity of hydrogen,

So this actually confirms existing theory.

And it does point to further methods which could lead to actual room temperature superconductors.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/08/2017 05:33 pm
DC makes more sense nowadays due to ubiquitous, efficient, and lightweight step up and step down DC to DC converters. They even can beat AC transformers.
Title: Re: Power options for a Mars settlement
Post by: JasonAW3 on 06/08/2017 05:46 pm
DC makes more sense nowadays due to ubiquitous, efficient, and lightweight step up and step down DC to DC converters. They beat AC transformers.

Problem is Robotbeat, if you have your generating system too far from the final destination of the electricity, then the line losses become very bad, with DC current.  (This is the reason that Westinghouse won the Niagara Falls contract, as DC power would require repeater generators every few miles).   AC current, on the other hand, doesn't have quite the same issues that DC current has.

In this case, you'd probably be better off generating DC (simpler) converting to AC for line transmission, (not quite so simple) then converting it back to DC for storage, in batteries.  While equipment CAN be designed with DC power in mind, most current civilian equipment is designed to work on AC.  (Honestly, I can't remember if the ISS is set up with DC or AC equipment and systems).
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/08/2017 05:52 pm
False. For the same peak voltage, DC losses are lower than AC.

Nowadays, high voltage DC is a thing. Wasn't true in the past.
Title: Re: Power options for a Mars settlement
Post by: whitelancer64 on 06/08/2017 05:54 pm
DC makes more sense nowadays due to ubiquitous, efficient, and lightweight step up and step down DC to DC converters. They beat AC transformers.

Problem is Robotbeat, if you have your generating system too far from the final destination of the electricity, then the line losses become very bad, with DC current.  (This is the reason that Westinghouse won the Niagara Falls contract, as DC power would require repeater generators every few miles).   AC current, on the other hand, doesn't have quite the same issues that DC current has.

In this case, you'd probably be better off generating DC (simpler) converting to AC for line transmission, (not quite so simple) then converting it back to DC for storage, in batteries.  While equipment CAN be designed with DC power in mind, most current civilian equipment is designed to work on AC.  (Honestly, I can't remember if the ISS is set up with DC or AC equipment and systems).

ISS is DC.

Transmission losses are obviously no issue there.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/08/2017 06:03 pm
There are actually more loss mechanisms in AC than in DC. In addition to resistive losses (which are lower in DC for the same peak voltage), you also have AC reactive power losses.

You can practically transmit power longer (7000km) distance with DC than with AC (4000km): https://en.wikipedia.org/wiki/Electric_power_transmission#Losses
Title: Re: Power options for a Mars settlement
Post by: RonM on 06/08/2017 06:22 pm
We're also discussing "Power options for a Mars settlement." Electricity production will be at the colony, like it is on ISS, so DC should work just fine. Maybe a kilometer away, but certainly not hundreds of kilometers.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/08/2017 06:40 pm
You can not transport DC output of a solar array over distance. Voltage is low, current is high. You need to invert, step up and reconvert to DC for long distance transport. You need to do the same for step down transforming at the receiving end.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/09/2017 02:20 pm
We're also discussing "Power options for a Mars settlement." Electricity production will be at the colony, like it is on ISS, so DC should work just fine. Maybe a kilometer away, but certainly not hundreds of kilometers.
Sure. Except you're missing the point: DC actually works BETTER than AC for distance.
Title: Re: Power options for a Mars settlement
Post by: Steve D on 06/09/2017 02:23 pm
You can not transport DC output of a solar array over distance. Voltage is low, current is high. You need to invert, step up and reconvert to DC for long distance transport. You need to do the same for step down transforming at the receiving end.

Or you just wire the panels in series to get whatever voltage you want. Individual cells have very low voltages but you can get any voltage you want by wiring in series.
Title: Re: Power options for a Mars settlement
Post by: RonM on 06/09/2017 03:03 pm
We're also discussing "Power options for a Mars settlement." Electricity production will be at the colony, like it is on ISS, so DC should work just fine. Maybe a kilometer away, but certainly not hundreds of kilometers.
Sure. Except you're missing the point: DC actually works BETTER than AC for distance.

True, but you're missing my point. Why are we even discussing long range power transmission in this thread when power production will right next door to the settlement? It's off topic.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/09/2017 05:09 pm
You can not transport DC output of a solar array over distance. Voltage is low, current is high. You need to invert, step up and reconvert to DC for long distance transport. You need to do the same for step down transforming at the receiving end.

Or you just wire the panels in series to get whatever voltage you want. Individual cells have very low voltages but you can get any voltage you want by wiring in series.

I don't think this would be a good idea for high kV transmission powers. It may also have sounded more complicated than it is. Modern power electronics are amazing and very robust.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/09/2017 07:39 pm
HVDC

https://en.wikipedia.org/wiki/Pacific_DC_Intertie
Title: Re: Power options for a Mars settlement
Post by: TrevorMonty on 06/09/2017 08:22 pm
7 june podcast is on 10kw solar powerstation for Mars, self deployed from lander.

http://spirit.as.utexas.edu/~fiso/archivelist.htm

Sent from my SM-G570Y using Tapatalk

Title: Re: Power options for a Mars settlement
Post by: DAZ on 06/09/2017 09:41 pm
It’s not the current (as in what kind of current) it’s the voltage.  If you use a lower voltage system (as in 5 volts for example) you will have humongous losses due to the high currents involved unless you are using exceptionally low resistance conductors.  This is pertinent as you basically talking about very big heavy wires.  At these low voltages, with the usual type of copper wire say 10 gauge you could have 50% or more losses in just hundreds of feet.  By stepping the voltage up significantly, to let’s say a few hundred volts, you could reduce these losses to single digits for distances of only a few hundred feet.  Higher voltages for longer distances are better.  Inside of a given structure, it could definitely be desirable to be using 20 to 30 VDC systems.  As just about all of the power generation systems discussed here require that the power be generated some distance from the place it will be used this require that the voltages be increased significantly above what you would normally find even in a house.

When stepping up or stepping down voltages the most efficient ways of doing this are to use an AC transformer.  So inherent DC systems like solar voltaic will usually convert the DC, using multiple different methods to AC.  They will then step this voltage up using a transformer.  You could then convert this higher voltage AC into higher voltage DC and transport that across your power line.  This could, in theory, be more efficient under certain circumstances like very high powers over very long distances.  Then at the other end convert this down to whatever usable voltages you needed.  As you are probably only talking about transporting this hundreds of feet to a handful of miles it would probably be more efficient, from the point of view of transported mass, to leave it as high-voltage AC until you get to where it needs to be used.  This means you only have to do the AC to DC and voltage conversion once.  This also doesn’t mean that the AC you use has to be 60 Hz.  As the distances we are discussing our relatively short a 400 Hz system with its lighter components might be desirable.

The Mars surface soil could inherently be a very good insulator.  This is something that probably should be checked out.  Even if it’s only moderately low resistance as in 1 to 2 ohms per foot you could still directly bury the conductors with only a moderate amount of insulation around the wires.  You could probably reasonably get up to several thousand volts safely this way.  All of this could save a significant amount of transported weight.  All of this weight will be coming out of your power generation budget so it needs to be accounted for in the total scheme.
Title: Re: Power options for a Mars settlement
Post by: floss on 06/11/2017 05:13 pm
This is the map of thorium for Mars pretty obvious where the first Mars base should be built.
Title: Re: Power options for a Mars settlement
Post by: scienceguy on 06/11/2017 06:48 pm
Isn't that the moon, not Mars?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/12/2017 12:41 am
This is the map of thorium for Mars pretty obvious where the first Mars base should be built.
Why the heck would you build your colony at your thorium mine? You only need a small amount of thorium/uranium, so transporting it to the other side of the planet is no problem. Same is not true of other resources.
Title: Re: Power options for a Mars settlement
Post by: llanitedave on 06/12/2017 12:59 am
Isn't that the moon, not Mars?

Well, if the first Mars base is built on the Moon that makes it easier to get to.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 06/12/2017 01:13 am
This is the map of thorium for Mars pretty obvious where the first Mars base should be built.
Why the heck would you build your colony at your thorium mine? You only need a small amount of thorium/uranium, so transporting it to the other side of the planet is no problem. Same is not true of other resources.

Campsite selection 101: camp near fuel, water and resources (game, material needs.) In this case fuel = fissionable materials. Saves a lot of walking if your transportation has a problem, such as being electric and the recharging power fails. Unless, of course, you have 50-100 kW of Kilopower modules on your vehicle
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/12/2017 04:48 am
This is the map of thorium for Mars pretty obvious where the first Mars base should be built.
Why the heck would you build your colony at your thorium mine? You only need a small amount of thorium/uranium, so transporting it to the other side of the planet is no problem. Same is not true of other resources.

Campsite selection 101: camp near fuel, water and resources (game, material needs.) In this case fuel = fissionable materials. Saves a lot of walking if your transportation has a problem, such as being electric and the recharging power fails. Unless, of course, you have 50-100 kW of Kilopower modules on your vehicle
I'd argue that it'll be a long time before you need to mine the Thorium locally.

What you need is water, and geological structure amenable to digging in.

When you finally want to mine for Thorium, it can be done at a remote site.  Much better than transporting water, or iron, or any other resource.

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/12/2017 07:04 am
This is the map of thorium for Mars pretty obvious where the first Mars base should be built.
Why the heck would you build your colony at your thorium mine? You only need a small amount of thorium/uranium, so transporting it to the other side of the planet is no problem. Same is not true of other resources.

Campsite selection 101: camp near fuel, water and resources (game, material needs.) In this case fuel = fissionable materials. Saves a lot of walking if your transportation has a problem, such as being electric and the recharging power fails. Unless, of course, you have 50-100 kW of Kilopower modules on your vehicle
Campsite 101 when your fuel source mass is comparable with your water mass instead of being A MILLION TIMES different.
Title: Re: Power options for a Mars settlement
Post by: Kaputnik on 06/13/2017 10:00 pm
We're also discussing "Power options for a Mars settlement." Electricity production will be at the colony, like it is on ISS, so DC should work just fine. Maybe a kilometer away, but certainly not hundreds of kilometers.
Sure. Except you're missing the point: DC actually works BETTER than AC for distance.

True, but you're missing my point. Why are we even discussing long range power transmission in this thread when power production will right next door to the settlement? It's off topic.

Probably just different perspectives on size/scale/time.
If Mars is settled on a truly planetary scale, it makes sense to connect the power grids of each settlement.
And since it's always daytime somewhere on the planet, doing so solves the energy storage problem (except for global dust storms).
Title: Re: Power options for a Mars settlement
Post by: Oli on 06/14/2017 01:16 pm
Interesting presentation on solar arrays on Mars, especially the second part. Variation in flux on the surface is quite extreme.

http://spirit.as.utexas.edu/%7Efiso/telecon/Pappa-Kerslake_6-7-17/
Title: Re: Power options for a Mars settlement
Post by: spacenut on 06/14/2017 01:37 pm
I thought the reason they chose AC over DC at the turn of the last century is DC did not transmit well over distance.  Initially power was produced at hydroelectric dams and had to be transmitted to where the people lived. 

Same may happen on Mars especially if they use nuclear.  It will be produced remotely away from a settlement, then transmitted.  So because of the massive use of AC worldwide, AC will probably be used, if they go nuclear.  Solar will only power so much due to the vast amount of space needed for the panels, and having to clean them from dust, so a lot more maintenance work. 

A seriously large Martian colony, will need probably far more power than the same sized city on earth.  They have to have power to produce their food, not open fields and sunlight.  Heat will be needed.  Continuous air handling will be needed.  Probably all construction equipment will be electric, thus requiring constant charging.  That is why in the long run, nuclear power is the only viable alternative.  Solar will not be as good on Mars as on Earth since it is further from the sun.  With this in mind, solar isn't taking over on earth, only in a few dessert areas and small scale.  Not the scale of nuclear, coal, natural gas, and even hydro.  Cost is still a problem on earth. 
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/14/2017 01:56 pm
I thought the reason they chose AC over DC at the turn of the last century is DC did not transmit well over distance.  Initially power was produced at hydroelectric dams and had to be transmitted to where the people lived. 

The problem was voltage transformation. You can transform AC up and down. With todays electronics you can do high frequency AC, transform it in a small transformer and  then transmit it as AC DC at low loss.

Edited per the remark of Robotbeat. It was a slip by me.
Title: Re: Power options for a Mars settlement
Post by: Dao Angkan on 06/14/2017 08:14 pm
I don't think that nuclear needs to be far from colonies ... they are self contained, so not an issue if atmosphere gets contaminated, and they should be radiation hardened from the environment anyway. Lots of people live near nuclear reactors on Earth, where atmospheric contamination would be far more of an issue.

I think that the biggest issue for nuclear on Mars would be opposition on Earth to launching it there.
Title: Re: Power options for a Mars settlement
Post by: DAZ on 06/14/2017 11:58 pm
Terms like near and far or high or low loss are relevant terms like hot and cold.  Is all determined by your personal reference.  So for it to make any sense you have to assign some numbers.

If you are talking, relatively low voltages like 5 to 50 V (without regard to its AC or DC) with conductors in the 8 to 10 gauge range and your distances are in the hundreds of feet you now have a common parameter to talk about.  Distances in the hundreds of feet would be pretty common regardless if you are using nuclear or solar.  This kind of a system would have extremely high loss as in 50 to 75% of your power you’re generating.

You can overcome this extremely high loss in one of 3 ways.  The 1st way is to make the distances shorter.  As these distances are pretty much as short as you can reasonably get there is not much to work with.  The 2nd way is to make your conductors very much bigger.  Aside from the price of copper just carrying large copper bars to Mars would be extremely expensive.  The 3rd way and most practical way is to step up the voltage.

It is technically possible, although somewhat more difficult, to directly step DC voltages up.  The much more practical way is to turn the DC into AC.  Then you can use high-efficiency transformers at each end to step the voltages up and down.  If you’re using a solar voltaic system it will generate its power as DC.  Many modern solar systems convert the DC to AC directly on the panel.  Depending on the type of nuclear power system you’re using it could generate its power in either DC or convert the heat into mechanical energy at which point you have a choice of generating either DC or AC.

The real takeaway here is to transport the power even in a relatively short distance of hundreds of feet with any kind of efficiency you must 1st step up the voltage (usually much higher than the end system needs) and this step up in voltage is best done as AC.  If you have already generated the power as AC is probably most efficient to leave it as AC until you are finished stepping the voltages up and down.  The exception to this would be if your AC frequency is too high and will generate radiated losses during transmission.  Some modern switching power supplies use AC frequencies in the tens of kilohertz to hundreds of kilohertz.  These frequencies may be too high to be usable at even the shorter transmission distances of hundreds of feet.  So you could either convert these to high voltage DC or use lower frequencies 50/60 or 400 Hz for example.

So it is really not an AC or DC question.  It is what engineering trades that the engineers will make to manipulate the voltages for the given system.  And other than at the endpoint there could be a mix of systems on Mars.

For example, a solar voltaic might need to be miles away just to have enough real estate to spread everything out.  In this case, the system might look like this.  Each section generates its power in very low voltage DC but immediately converts this to 100 V 400 Hz AC.  All the sections are connected together until they get to the main power line where the voltage is stepped up to 10 kV.  This is then transported via the underground cable several miles to the location where the power will be used/stored.  It is then converted down to 30 VDC (that is stored in batteries or used for most applications) and some of it at 200 VDC for high power applications.  Power from the batteries for the higher power applications when necessary could use the higher frequency switching power supplies operating in the tens of kilohertz.

Alternately the nuclear power system could generate its power directly as 200 V DC and transport this the 500 with thousand feet to be used/stored.  Some of the power would be used, as above, for high power applications.  Like above, the power to and from the batteries would use high frequency switching power supplies.

As you can see it is really not about AC or DC.  It’s all about the voltages.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/15/2017 04:22 am
The real takeaway here is to transport the power even in a relatively short distance of hundreds of feet with any kind of efficiency you must 1st step up the voltage (usually much higher than the end system needs) and this step up in voltage is best done as AC.  If you have already generated the power as AC is probably most efficient to leave it as AC until you are finished stepping the voltages up and down.  The exception to this would be if your AC frequency is too high and will generate radiated losses during transmission.  Some modern switching power supplies use AC frequencies in the tens of kilohertz to hundreds of kilohertz.  These frequencies may be too high to be usable at even the shorter transmission distances of hundreds of feet.  So you could either convert these to high voltage DC or use lower frequencies 50/60 or 400 Hz for example.

So it is really not an AC or DC question.  It is what engineering trades that the engineers will make to manipulate the voltages for the given system.  And other than at the endpoint there could be a mix of systems on Mars.

I mostly agree. But if you transform AC to DC with modern power electronics it is likely the best design choice to transform to quite high frequencies, so you can use a small lightweight transformer. This then requires to transform it back to DC for transport. That is when you are handling power in the MW range. With 10kW 50 or 60 Hz might be fine but as you say it will be an engineering exercise to determine it for any given circumstances.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/15/2017 06:53 am
I thought the reason they chose AC over DC at the turn of the last century is DC did not transmit well over distance.  Initially power was produced at hydroelectric dams and had to be transmitted to where the people lived. 

The problem was voltage transformation. You can transform AC up and down. With todays electronics you can do high frequency AC, transform it in a small transformer and  then transmit it as AC at low loss.
You mean transmit as DC. But yeah, this is the reason.
Title: Re: Power options for a Mars settlement
Post by: DAZ on 06/16/2017 02:16 am
This conversation is hung up on transmission losses. On Mars, that will be nearly irrelevant for decades- if ever.

This is one of those relevant issues.  If you're thinking that transmission losses only pertaining to high tension power lines when they stretch hundreds if not thousands of miles then you are probably correct.

The transmission losses I have been discussing, on the other hand, are pertinent in the hundreds of feet and beyond.  So this is relevant to a Martian colony from literally day one.  Power sources at a minimum will need to be hundreds of feet from where the power is needed.  And very quickly will stretch into many miles.

Transmission power lines are in virtually every neighborhood.  They are in industrial business parks.  I have been to some very small remote and out-of-the-way villages and even they have transmission power lines from their central generating facilities.  These relatively small facilities and locations don't generate power and use it in the megawatt scale.  This Martian colony is going to have to generate power in megawatts and transport the power to both water mining facilities and propellant manufacturing/storage locations.  So this is most definitely gonna be an issue from day one.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/16/2017 02:52 am
Probably hundreds of volts DC, maybe thousands.

On residential PV systems, one of the best methods is to put a power optimizer (cheap and small) on each panel that hooks up to a 400VDC common bus. That makes it easy to transmit the power on lightweight conductors. Also makes integration with a battery system easier. Then it's finally inverted. But on Mars, you could just use the power at that voltage or perhaps step down and/or invert the power at the point of use.

Could be 400V or 1000V or 5000V. Whichever is more convenient.
Title: Re: Power options for a Mars settlement
Post by: raketa on 06/16/2017 06:10 am
have too many devices raise the risk of failure, this reason it think it will be DC, at the beginning
Title: Re: Power options for a Mars settlement
Post by: AncientU on 06/16/2017 07:04 pm
This conversation is hung up on transmission losses. On Mars, that will be nearly irrelevant for decades- if ever.

This is one of those relevant issues.  If you're thinking that transmission losses only pertaining to high tension power lines when they stretch hundreds if not thousands of miles then you are probably correct.

The transmission losses I have been discussing, on the other hand, are pertinent in the hundreds of feet and beyond.  So this is relevant to a Martian colony from literally day one.  Power sources at a minimum will need to be hundreds of feet from where the power is needed.  And very quickly will stretch into many miles.

Transmission power lines are in virtually every neighborhood.  They are in industrial business parks.  I have been to some very small remote and out-of-the-way villages and even they have transmission power lines from their central generating facilities.  These relatively small facilities and locations don't generate power and use it in the megawatt scale.  This Martian colony is going to have to generate power in megawatts and transport the power to both water mining facilities and propellant manufacturing/storage locations.  So this is most definitely gonna be an issue from day one.

Just a nit...
Let's at least give a nod to planetary protection for Mars and not introduce the noxious and debilitating plague -- American Standard Units.
Title: Re: Power options for a Mars settlement
Post by: AncientU on 06/16/2017 07:13 pm
have too many devices raise the risk of failure, this reason it think it will be DC, at the beginning

Custom making every device headed to Mars to use an uncommon (and dangerous) power supply (high voltage DC) is a bad idea and an expensive one.  Keep it simple and use nominal voltage AC, 50Hz, and COTS components will be vastly more affordable. We use this system in local power distribution to consumers for lots of reasons.
Title: Re: Power options for a Mars settlement
Post by: DAZ on 06/16/2017 09:19 pm
This conversation is hung up on transmission losses. On Mars, that will be nearly irrelevant for decades- if ever.

This is one of those relevant issues.  If you're thinking that transmission losses only pertaining to high tension power lines when they stretch hundreds if not thousands of miles then you are probably correct.

The transmission losses I have been discussing, on the other hand, are pertinent in the hundreds of feet and beyond.  So this is relevant to a Martian colony from literally day one.  Power sources at a minimum will need to be hundreds of feet from where the power is needed.  And very quickly will stretch into many miles.

Transmission power lines are in virtually every neighborhood.  They are in industrial business parks.  I have been to some very small remote and out-of-the-way villages and even they have transmission power lines from their central generating facilities.  These relatively small facilities and locations don't generate power and use it in the megawatt scale.  This Martian colony is going to have to generate power in megawatts and transport the power to both water mining facilities and propellant manufacturing/storage locations.  So this is most definitely gonna be an issue from day one.

Just a nit...
Let's at least give a nod to planetary protection for Mars and not introduce the noxious and debilitating plague -- American Standard Units.

You may have a point but I grew up with ASU so that is how I think.  I can translate of course but that require that I think and that is not my strong suit. ;)
Title: Re: Power options for a Mars settlement
Post by: Jcc on 06/17/2017 04:15 pm
have too many devices raise the risk of failure, this reason it think it will be DC, at the beginning

Custom making every device headed to Mars to use an uncommon (and dangerous) power supply (high voltage DC) is a bad idea and an expensive one.  Keep it simple and use nominal voltage AC, 50Hz, and COTS components will be vastly more affordable. We use this system in local power distribution to consumers for lots of reasons.

Even with the efficiency of a reusable ITS, transportation cost to Mars will still be outrageously expensive compared to shipping around Earth. Therefore, a custom design that minimizes weight and is suited to the Mars environment may be far cheaper and more practical than COTS devices designed for Earth.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/17/2017 05:29 pm
Even with the efficiency of a reusable ITS, transportation cost to Mars will still be outrageously expensive compared to shipping around Earth. Therefore, a custom design that minimizes weight and is suited to the Mars environment may be far cheaper and more practical than COTS devices designed for Earth.
I'd caution that this is very much the performance-above-everything that makes the NASA Mars mission about $40Bn.

This issue was faced when commercial flying started to become a thing in the late 1920's and early 1930's.

The compromise was to go with 400Hz AC, which is still very much in use.

Power electronics has made vast strides over the last 40 years in terms of voltage and current handled (much higher), and the size of the package (much smaller) needed.

It's a subject I imagine SX can access through links to Tesla, as well as their in house skills.

However that means another range of specialized semiconductors whose supply chain needs to be maintained.

So it is really not an AC or DC question.  It is what engineering trades that the engineers will make to manipulate the voltages for the given system.  And other than at the endpoint there could be a mix of systems on Mars.

This point. SX are very pragmatic. Any moves away from something as fundamental in this area means either providing specialist PSU's for all your kit or having mfgs build "Mars only" motors for all your gear.

That does not sound like SX's way of doing things.  :(

Incidentally Methalox could also be used in a fuel cell system (although not a favorite option of Musks). Keep in mind the resulting CO2/water products would be much purer and the CO2 much higher density than stuff collected from the planet. It's quite likely you'd want to retain the exhaust for re-conversion.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/17/2017 06:50 pm
Just use CO/O2 as a fuel system. Then you don't need to mine water and don't need to collect the exhaust.

There's also a sizable efficiency advantage to using CO/O2 instead of methalox. Methane is made via electrolysis of hydrogen then combining with CO2 in the Sabatier Reaction. That wastes a bunch of energy. So not only does methane require water and probably requires collection of exhaust, but it is also fundamentally less efficient.

Also, we'll probably use medium voltage DC, like 400V. That's what electric cars operate at. You just use a DC-DC converter, like is used in everything nowadays from car adapters to USB, etc. they're ubiquitous and thus invisible. They're also common in data centers.
Title: Re: Power options for a Mars settlement
Post by: DAZ on 06/17/2017 07:25 pm
SpaceX is definitely very pragmatic.  To have any hope at all of permanently settling on Mars everybody involved will have to be exceptionally pragmatic.

There is no one size fits all solution for power options on Mars just like there is not a one size fits all solution on earth.  We use AC/DC with varying voltages from very low to very high on earth now.  Let Topsy stay dead and buried.  She definitely paid for any crimes she may have committed.  Likewise, there is no reason to start a new War of Currents.

The only place that power appears to be near universal is in the common household.  Even then there are differences between the European and the American standards.  Neither one is particularly better than the other.  Once you get away from the common household you will find that a wide variety of voltages both DC and AC are used almost everywhere else.  On earth, we use diesel electric trains.  These can be both DC and AC.  You’ll find similar situations in mining.  It’s quite possible that on Mars they might be using methanol fuel cell electric mining equipment instead of having to drag the power cables along behind them.  On the other hand, they might just use batteries and swap them out as necessary, charging them at some other location.

Much of what we think now as COTS is not exactly off the shelf.  Once you start to get away from items that are of a household type use you will find that many of these items are not exactly off the shelf.  You order them, they are then made to spec, and they have a lead time in weeks to years.  Many items that would seem to be off-the-shelf items on earth will by necessity need to be specially designed for Mars.  Even a simple DC motor that is used on Earth may need to be redesigned to take into account the lack of air cooling.  Many items we use on Earth, on the other hand, may require little if no modifications.  For example, the common laptop can probably be used just as readily on Mars as on Earth regardless of what the power is.

Getting to Mars may require rocket science but power is definitely not rocket science.  We have been doing this for something like 150 years.  We definitely have an extremely large body of electrical engineers to draw on to solve these problems.  And undoubtedly they will be extremely pragmatic in their solutions.  If they can use a simple COTS available item then undoubtedly they will.  If they can take a COTS item and only need to make simple modifications then that’s what they’ll do.  But if they have to make an item from scratch, then that’s what they will do.  The items we are talking about are not that inherently expensive/difficult to make, even in small quantities.

So in the end just like on Earth you’ll see multiple variations of power as needed.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/17/2017 10:40 pm
Just use CO/O2 as a fuel system. Then you don't need to mine water and don't need to collect the exhaust.
In principle this is a backup system that is only needed in emergencies. On that basis any system should leverage as much existing infrastructure as possible. Since SX have decided on Methalox (and show no signs of changing that decision) the simplest option is to run power generation (either combustion based or FC) with the same reactants, running overnight needs on batteries.
Quote from: Robotbeat
There's also a sizable efficiency advantage to using CO/O2 instead of methalox. Methane is made via electrolysis of hydrogen then combining with CO2 in the Sabatier Reaction. That wastes a bunch of energy. So not only does methane require water and probably requires collection of exhaust, but it is also fundamentally less efficient.
OTOH it creates more special components for the logistics operation to manage. Due to the mass of propellant that needs to be mfg atmospheric handling is going to be a major problem, regardless of what system is chosen.
Quote from: Robotbeat
Also, we'll probably use medium voltage DC, like 400V. That's what electric cars operate at. You just use a DC-DC converter, like is used in everything nowadays from car adapters to USB, etc. they're ubiquitous and thus invisible. They're also common in data centers.
Keep in mind that any power conversion is never 100% efficient and will either need to dump heat into the environment or be on a cooling loop. Given any settlement  is likely to be energy poor the cooling loop is not as inconvenient as it sounds.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/17/2017 11:29 pm
DC-DC converters are just as efficient as transformers and AC-DC converters that are ubiquitous. Also, you have the option of setting the operating DC voltage at the battery's voltage, thus improving efficiency.

And by using DC, there are several kinds of losses that you can avoid which you have to deal with if using AC.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 06/18/2017 02:55 pm
Just use CO/O2 as a fuel system. Then you don't need to mine water and don't need to collect the exhaust.
In principle this is a backup system that is only needed in emergencies. On that basis any system should leverage as much existing infrastructure as possible. Since SX have decided on Methalox (and show no signs of changing that decision) the simplest option is to run power generation (either combustion based or FC) with the same reactants, running overnight needs on batteries.

I agree with using methalox for emergency power supplies if methalox is available - i.e. you happen to be near where methalox propellant production facilities are sited, which will be true in the early days. But any settlement is likely to soon have outposts and a CO/O2 system might then be useful as an emergency backup power system; perhaps even a non-emergency one. The obvious alternative is simply more batteries, but batteries are heavy, expensive and need a great deal of industrial infrastructure to manufacture. A CO/O2 system may be more easily manufactured on Mars. I foresee an engineering trades analysis!
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/18/2017 03:54 pm
A system that can burn both CO/O2 and methane O2 would be helpful at the main site. CO/O2 can keep heavy industry running over night and may be more efficient than batteries, when weight and lifespan is included. In emergencies like long dust storms the propellant store can be used.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 06/20/2017 04:58 am
A system that can burn both CO/O2 and methane O2 would be helpful at the main site. CO/O2 can keep heavy industry running over night and may be more efficient than batteries, when weight and lifespan is included. In emergencies like long dust storms the propellant store can be used.

Good idea. Dual fuel shouldn't be a problem (the on-board generator for the Wrightspeed hybrid truck is a micro-turbine that is designed to run on diesel, compressed natural gas, liquid natural gas, liquid propane, or landfill gasses).

You might want generators at two sites (and away from any batteries) for redundancy/safety reasons. Just as you probably don't want to keep all your propellant in two big tanks. Though such redundancy comes at a cost, of course.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/21/2017 10:53 am
Good idea. Dual fuel shouldn't be a problem (the on-board generator for the Wrightspeed hybrid truck is a micro-turbine that is designed to run on diesel, compressed natural gas, liquid natural gas, liquid propane, or landfill gasses).
I had not heard of Wrightspeed before. There technology sounds interesting and the power level seems to be in the range that a small settlement would need, although you could cluster them for larger sizes. 
Quote from: CuddlyRocket
You might want generators at two sites (and away from any batteries) for redundancy/safety reasons. Just as you probably don't want to keep all your propellant in two big tanks. Though such redundancy comes at a cost, of course.
The last thing you want is your contingency system (which is only operating in an emergency) to fail on you, making what's already a serious situation worse.

If the system could run on either CO or CH4 you would have two sets of tanks anyway. Keep in mind while on emergency power it's likely all propellant production will be shut down and if the system has to switch to Methalox burning things will have gotten very serious.
Title: Re: Power options for a Mars settlement
Post by: Ludus on 06/27/2017 04:37 pm
From the POV of a commercial project, Solar Power Satellites in Areostationary Orbit have some real advantages. ASO is less than half the distance of GSO, not much atmosphere to get in the way, no real environmental issues or land issues with the rectenna.

SPS's have the advantage of scaling. If you have a design that can deploy itself and start beaming power it can be replicated and improved. Local conditions don't change for every deployment.

The system is likely to be lower upkeep. Ground PV has to be kept free of dust. Rectennas are likely much less trouble.

It provides reliable power 24/7 unlike ground Solar, without batteries. Unlike the Terrestrial version it's not competing with Solar PV with zero launch cost...it all has to get to Mars one way or another.

It's flexible. If Mars has a new settlement it can be powered right away hundreds of miles from old settlements.

It's a utility service that bills for power delivered not a product.

Mars will need a lot of electricity.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 03/09/2018 05:49 pm
MIT Aims To Bring Nuclear Fusion To The Market In 10 Years

http://www.wbur.org/bostonomix/2018/03/09/mit-nuclear-fusion

https://www.engadget.com/2018/03/09/mit-embarks-ambitious-plan-build-nuclear-fusion-2033/
Title: Re: Power options for a Mars settlement
Post by: Hominans Kosmos on 03/09/2018 10:29 pm
MIT Aims To Bring Nuclear Fusion To The Market In 10 Years

http://www.wbur.org/bostonomix/2018/03/09/mit-nuclear-fusion

https://www.engadget.com/2018/03/09/mit-embarks-ambitious-plan-build-nuclear-fusion-2033/

For some context and background on those articles

https://www.youtube.com/watch?v=L0KuAx1COEk

https://www.youtube.com/watch?v=KkpqA8yG9T4

TL;DR: commercial availability of continuously improving magnetic field and current density compatible high temperature superconductors. 
Basically the remaining job is commercializing the specific integration of the commercial off-the-shelf technologies in modern start-up fashion, quickly and efficiently.

It seems reasonable to expect these aspirations to be met. This would make these commercial reactor technologies available for the aerospace community to lightweight for airlift and space-lift compatible versions.

Edit: disambiguating field strength and current density
Title: Re: Power options for a Mars settlement
Post by: speedevil on 03/09/2018 10:50 pm
TL;DR: commercial availability of continuously improving magnetic field density resistant high temperature superconductors. 
Basically the remaining job is commercializing the specific integration of the commercial off-the-shelf technologies in modern start-up fashion, quickly and efficiently.

It seems reasonable to expect these aspirations to be met. This would make these commercial reactor technologies available for the aerospace community to lightweight for airlift and space-lift compatible versions.

I just watched that a few days ago.
There are major caveats in lightweighting - namely that as I understand it, other than for the ancillary systems, you pretty much can't, this is the minimal size.

The whole thing pretty much needs to be largely steel, or coolant, or superconductor wire, and you can't go significantly under 6m diameter, or the scaling goes all wrong.

However.
This isn't too disasterous, the weight of the system is not >20000 tons for the reactor like ITER, but more like 300-400 tons.

But, it gets better!
Due to the design, you can obviously drain the coolant, and remove the vacuum vessel and inner superconductors (it's designed for this for servicing), and get it in two major halves of about 150 tons each.
A number you may remember from elsewhere.

You then need probably several more loads of cryogenics, heat radiators, generators, and such. But then if you get it working, your only meaningful import for power per 500MW-years becomes the vacuum vessel and superconductors, which are a consumable, weighing perhaps 50 tons.

(assuming it works according to the design shown)
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/10/2018 01:48 pm
One point I've not seen discussed very much is how much baseload vs dispatchable power will be needed on Mars.

Given by far the greatest power requirement comes from the Sabatier plant making rocket fuel, I think the answer to this hinges on how amenable our hypothetical Mars-based Sabatier plant will be to shutting down and starting up again. I know that in heavy industry on Earth some industries are very suitable to Demand Side Response, is this the case with the Sabatier plant? What kind of penalties are there to shutting down/starting up? What losses are there, and how agile (fast) can a shutdown/startup be done in this kind of process?
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 04/11/2018 06:06 pm
One point I've not seen discussed very much is how much baseload vs dispatchable power will be needed on Mars.

Given by far the greatest power requirement comes from the Sabatier plant making rocket fuel, I think the answer to this hinges on how amenable our hypothetical Mars-based Sabatier plant will be to shutting down and starting up again. I know that in heavy industry on Earth some industries are very suitable to Demand Side Response, is this the case with the Sabatier plant? What kind of penalties are there to shutting down/starting up? What losses are there, and how agile (fast) can a shutdown/startup be done in this kind of process?

I don't know the answer to that, but the ability to reduce power consumption significantly would be desirable, especially if solar was a significant source of electrical power - at night and during dust storms, for example. But you might not need to shut down the propellant plant; reducing output may be sufficient.

Minimum baseload is presumably life-support and keeping essential equipment etc running.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 04/11/2018 07:12 pm
One point I've not seen discussed very much is how much baseload vs dispatchable power will be needed on Mars.

Given by far the greatest power requirement comes from the Sabatier plant making rocket fuel, I think the answer to this hinges on how amenable our hypothetical Mars-based Sabatier plant will be to shutting down and starting up again. I know that in heavy industry on Earth some industries are very suitable to Demand Side Response, is this the case with the Sabatier plant? What kind of penalties are there to shutting down/starting up? What losses are there, and how agile (fast) can a shutdown/startup be done in this kind of process?

I don't know the answer to that, but the ability to reduce power consumption significantly would be desirable, especially if solar was a significant source of electrical power - at night and during dust storms, for example. But you might not need to shut down the propellant plant; reducing output may be sufficient.

Minimum baseload is presumably life-support and keeping essential equipment etc running.

Not all life support has to be baseload. You could use consumable stores (e.g. O2, water) when you don't have power, then regenerate (by electrolysis, filtration, etc.) them when you do.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 04/11/2018 07:21 pm
One point I've not seen discussed very much is how much baseload vs dispatchable power will be needed on Mars.

Given by far the greatest power requirement comes from the Sabatier plant making rocket fuel, I think the answer to this hinges on how amenable our hypothetical Mars-based Sabatier plant will be to shutting down and starting up again. I know that in heavy industry on Earth some industries are very suitable to Demand Side Response, is this the case with the Sabatier plant? What kind of penalties are there to shutting down/starting up? What losses are there, and how agile (fast) can a shutdown/startup be done in this kind of process?
The assumption was, that the generated fuel would also serve as electricity source while solar power is not available.

This obviously does not work to power the ISRU plant...
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/11/2018 07:22 pm
One point I've not seen discussed very much is how much baseload vs dispatchable power will be needed on Mars.

Given by far the greatest power requirement comes from the Sabatier plant making rocket fuel, I think the answer to this hinges on how amenable our hypothetical Mars-based Sabatier plant will be to shutting down and starting up again. I know that in heavy industry on Earth some industries are very suitable to Demand Side Response, is this the case with the Sabatier plant? What kind of penalties are there to shutting down/starting up? What losses are there, and how agile (fast) can a shutdown/startup be done in this kind of process?

I don't know the answer to that, but the ability to reduce power consumption significantly would be desirable, especially if solar was a significant source of electrical power - at night and during dust storms, for example. But you might not need to shut down the propellant plant; reducing output may be sufficient.

Minimum baseload is presumably life-support and keeping essential equipment etc running.

Not all life support has to be baseload. You could use consumable stores (e.g. O2, water) when you don't have power, then regenerate (by electrolysis, filtration, etc.) them when you do.

Yep. I read on another thread here that the larger your habitat volume, the longer it takes for the O2 mix to become seriously depleted. It sounds like given the 'planned economy' of a Martian colony, very little baseload is necessary - night times and local dust storms could almost certainly be powered by a relatively modest battery backup (we're seeing more and more utility-scale battery deployments on Earth. They'll only get cheaper and better). However, surviving longer dust storms remains a challenge. I think it would be crazy not to have some kind of backup Methane turbine/generator for these situations, given the stockpiles the colony will have for most of the synod.

Does anyone know how flexible a Sabatier plant can be?
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 04/11/2018 09:18 pm
Yep. I read on another thread here that the larger your habitat volume, the longer it takes for the O2 mix to become seriously depleted.

And I recall also seeing that "air pockets" last far, far longer than people think. 

http://www.vocativ.com/198502/underwater-air-pocket-yangtze-river/index.html
"Hexdall calculated that, in an air pocket the size of a U-Haul moving van, it would take about 79 hours before you lost consciousness."
Title: Re: Power options for a Mars settlement
Post by: Steve D on 04/11/2018 09:45 pm
Yep. I read on another thread here that the larger your habitat volume, the longer it takes for the O2 mix to become seriously depleted.

And I recall also seeing that "air pockets" last far, far longer than people think. 

http://www.vocativ.com/198502/underwater-air-pocket-yangtze-river/index.html
"Hexdall calculated that, in an air pocket the size of a U-Haul moving van, it would take about 79 hours before you lost consciousness."


Yes, but its not the lack of oxygen thats the problem. Its the carbon dioxide build up that will get you in trouble first long before you run out of oxygen.
Title: Re: Power options for a Mars settlement
Post by: whitelancer64 on 04/11/2018 09:57 pm
Yep. I read on another thread here that the larger your habitat volume, the longer it takes for the O2 mix to become seriously depleted.

And I recall also seeing that "air pockets" last far, far longer than people think. 

http://www.vocativ.com/198502/underwater-air-pocket-yangtze-river/index.html
"Hexdall calculated that, in an air pocket the size of a U-Haul moving van, it would take about 79 hours before you lost consciousness."


Yes, but its not the lack of oxygen thats the problem. Its the carbon dioxide build up that will get you in trouble first long before you run out of oxygen.

That's exactly what that article says.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/11/2018 10:09 pm
Yep. I read on another thread here that the larger your habitat volume, the longer it takes for the O2 mix to become seriously depleted.

And I recall also seeing that "air pockets" last far, far longer than people think. 

http://www.vocativ.com/198502/underwater-air-pocket-yangtze-river/index.html
"Hexdall calculated that, in an air pocket the size of a U-Haul moving van, it would take about 79 hours before you lost consciousness."
Yes, but its not the lack of oxygen thats the problem. Its the carbon dioxide build up that will get you in trouble first long before you run out of oxygen.
So you need first after a while CO2 scrubbing, and then later begin to need oxygen supplementation.
separate to solving these, you could have individual or room sized emergency systems based on either scrubbing or exhausting CO2 rich "air", and O2 supplementation from pressurised storage.

But for larger community and working spaces, plus for resilience, and avoiding excessive disruption from dust storms etc, you have plants, (which unfortunately need light input, which will in a dust storm be largely from likely scarce electrical power). However they should be considered a key part in maintaining breathable air.

Then there is large scale chemical scrubbing. One look at Wikipedia https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber (https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber), gave several reactions the first is:
Quote from: wikipedia
The dominant application for CO2 scrubbing is for removal of CO2 from the exhaust of coal- and gas-fired power plants. Virtually the only technology being seriously evaluated involves the use of various amines, e.g. monoethanolamine. Cold solutions of these organic compounds bind CO2, but the binding is reversed at higher temperatures:

CO2  +  2 HOCH2CH2NH2  ↔  HOCH2CH2NH3+  +  HOCH2CH2NHCO2−

And since it is reversible, when the storm has passed and more energy is available the CO2 is recovered for use in Sabatier, and the monoethanolamine is recovered for use next time. This would be built into the ECLSS breathable air management system. I am no expert on this, but at first sight something like this would be an excellent and reusable buffer for periods of lacking light and energy. As for O2, just a large reserve of pressurised/liquid? O2, that is output earlier from Sabatier.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 04/11/2018 10:39 pm
And I recall also seeing that "air pockets" last far, far longer than people think. 

Yes, but its not the lack of oxygen thats the problem. Its the carbon dioxide build up that will get you in trouble first long before you run out of oxygen.

That's exactly what that article says.

And a perfect example of the point in bold red above.   ;D
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/12/2018 01:11 am
BTW, if you have access to vacuum, then CO2 scrubbing is pretty easy with some valves. The only problem is Mars isn't totally a vacuum as it has a CO2 partial pressure higher than usual Earth air. But regardless, even if you need a more active scrubber, it doesn't take much energy compared to oxygen production.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/12/2018 04:12 am
I like the idea of polar orbital solar power at the dusk-dawn area of around Mars.  The solar power would always be facing the sun while beaming the power to a dark side receiving antenna for night power.  Having several solar stations orbiting Mars in this vertical orbital plane could actually beam power almost anywhere on Mars at any time.  Not as much need for batteries. 

Another idea is to split water during the day into hydrogen and oxygen, then use the two as batteries at night like they did with Apollo and have water reproduced as a by product.  All this in a closed system. 

Small scale fission reactors will probably eventually be brought, coupled together to produce all the power they need for industrial scale uses.   
Title: Re: Power options for a Mars settlement
Post by: envy887 on 04/12/2018 12:59 pm
I like the idea of polar orbital solar power at the dusk-dawn area of around Mars.  The solar power would always be facing the sun while beaming the power to a dark side receiving antenna for night power.  Having several solar stations orbiting Mars in this vertical orbital plane could actually beam power almost anywhere on Mars at any time.  Not as much need for batteries. 

Another idea is to split water during the day into hydrogen and oxygen, then use the two as batteries at night like they did with Apollo and have water reproduced as a by product.  All this in a closed system. 

Small scale fission reactors will probably eventually be brought, coupled together to produce all the power they need for industrial scale uses.

Solar+batteries is also closed system, and far lighter and more efficient than fuel cells and electrolysis and storing LH2.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 04/12/2018 01:12 pm
I like the idea of polar orbital solar power at the dusk-dawn area of around Mars.  The solar power would always be facing the sun while beaming the power to a dark side receiving antenna for night power.  Having several solar stations orbiting Mars in this vertical orbital plane could actually beam power almost anywhere on Mars at any time.  Not as much need for batteries. 

Another idea is to split water during the day into hydrogen and oxygen, then use the two as batteries at night like they did with Apollo and have water reproduced as a by product.  All this in a closed system. 

Small scale fission reactors will probably eventually be brought, coupled together to produce all the power they need for industrial scale uses.

Solar+batteries is also closed system, and far lighter and more efficient than fuel cells and electrolysis and storing LH2.

SpaceX has easy access to state of the art battery storage. Why would they spend R&D $ to develop and launch a satellite power system AND ground rectenna farm when the solution is just more batteries for night power?  There are many many R&D challenges for a Mars base without inventing new R&D costs.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/12/2018 01:12 pm
By the way, everyone, the Sabatier Reaction is exothermic (meaning it produces heat) and so requires no power source except for operation of valves. It is the electrolysis of hydrogen that requires power input, and that is easily rampable. It is essentially a fuel cell in reverse. So there is no reason you can’t just turn off electrolysis during a dust storm.

And it’s worth pointing out that because most power consumption will be due to ISRU, if ISRU is shut down temporarily, then there’s easily enough power to keep the rest of the settlement operating because solar panels still produce power even during a dust storm, just at lower output. You don’t have to burn your precious propellant, just stop electrolysis.

Let’s say the dust storm reduces solar output by 80%. If ISRU consumes 80% of your power requirements, then the rest of the settlement can run without any power reduction just by shutting down ISRU temporarily.

It’s like growing crops: a cloudy week doesn’t make much difference as the crop kind of averages energy acquisition over months. ISRU is a long-term energy storage system like crops, and so long-term a dust storm makes very little difference.
Title: Re: Power options for a Mars settlement
Post by: Steve D on 04/12/2018 02:39 pm
I like the idea of polar orbital solar power at the dusk-dawn area of around Mars.  The solar power would always be facing the sun while beaming the power to a dark side receiving antenna for night power.  Having several solar stations orbiting Mars in this vertical orbital plane could actually beam power almost anywhere on Mars at any time.  Not as much need for batteries. 

Another idea is to split water during the day into hydrogen and oxygen, then use the two as batteries at night like they did with Apollo and have water reproduced as a by product.  All this in a closed system. 

Small scale fission reactors will probably eventually be brought, coupled together to produce all the power they need for industrial scale uses.

How much would a dust storm affect the microwave beam? As I understand it there is a fair amount of iron in the dust. Could that block or disrupt the beam?
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 04/12/2018 03:50 pm
BTW, if you have access to vacuum, then CO2 scrubbing is pretty easy with some valves. The only problem is Mars isn't totally a vacuum as it has a CO2 partial pressure higher than usual Earth air. But regardless, even if you need a more active scrubber, it doesn't take much energy compared to oxygen production.

another easy co2 scrubbing system is just a cold trap.
N2 and O2 have lower boiling points than CO2. You could use some liquid methane to cool the trap.
No electricity required.
Title: Re: Power options for a Mars settlement
Post by: josespeck on 04/12/2018 05:53 pm
Mars crops can be used to make batteries or capacitors of popcorn. Can ionic liquid be produced on Mars?.
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/13/2018 05:49 am
By the way, everyone, the Sabatier Reaction is exothermic (meaning it produces heat) and so requires no power source except for operation of valves. It is the electrolysis of hydrogen that requires power input, and that is easily rampable. It is essentially a fuel cell in reverse. So there is no reason you can’t just turn off electrolysis during a dust storm.

And it’s worth pointing out that because most power consumption will be due to ISRU, if ISRU is shut down temporarily, then there’s easily enough power to keep the rest of the settlement operating because solar panels still produce power even during a dust storm, just at lower output. You don’t have to burn your precious propellant, just stop electrolysis.

Let’s say the dust storm reduces solar output by 80%. If ISRU consumes 80% of your power requirements, then the rest of the settlement can run without any power reduction just by shutting down ISRU temporarily.

It’s like growing crops: a cloudy week doesn’t make much difference as the crop kind of averages energy acquisition over months. ISRU is a long-term energy storage system like crops, and so long-term a dust storm makes very little difference.

I had a conversation with my father-in-law yesterday who used to work in petrochemical refineries. His conclusion was the only thing that would happen when turning off the ISRU system would be that as it cooled down, the ratios of the produced liquids in the distillation part would change, something that is not difficult to handle.

One more question I have about the dust storms: I've read that local dust storms typically take 2-3 days and reduce PV by around 80%. What about the larger, longer lasting dust storms?
Title: Re: Power options for a Mars settlement
Post by: Semmel on 04/13/2018 10:55 am
One more question I have about the dust storms: I've read that local dust storms typically take 2-3 days and reduce PV by around 80%. What about the larger, longer lasting dust storms?

There are global martian dust storms that can last for month.

see: https://en.wikipedia.org/wiki/Martian_soil#Atmospheric_dust

specifically: https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/PIA03170_fig1duststroms.jpg/800px-PIA03170_fig1duststroms.jpg


Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/13/2018 12:47 pm
I don't think some of you guys read what I said.  No batteries.  Solar power at a polar orbit at a 6am/6pm position, so it gets continuous sun that can be beamed to the dark side over the horizon.  In the day time ground solar would work.  The only thing would be several large solar stations in continuous same orbit beaming power to the back side.  Reception would only be bad during dust storms, some batteries would be required during dust storms anyway. 

The only other options would be fission or fusion generators for continuous uninterrupted power.  Either would be fine for Mars, especially banks of small scale self contained reactors. 
 
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/13/2018 01:11 pm
I don't think some of you guys read what I said.  No batteries.  Solar power at a polar orbit at a 6am/6pm position, so it gets continuous sun that can be beamed to the dark side over the horizon.  In the day time ground solar would work.  The only thing would be several large solar stations in continuous same orbit beaming power to the back side.  Reception would only be bad during dust storms, some batteries would be required during dust storms anyway. 

The only other options would be fission or fusion generators for continuous uninterrupted power.  Either would be fine for Mars, especially banks of small scale self contained reactors. 
 
But solar+batteries is a perfectly fine solution, particularly since the solar array would be primarily sized for ISRU which is easy to throttle down and thus the solar array would be over-sized enough to provide plenty of power for the rest of the settlement even during a dust storm.

Space based solar power is just not needed. Battery tech is already plenty good enough, and has the ability to improve by a factor of 10 by using a lithium-CO2 battery in the future (has been tested in the lab already).
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/13/2018 01:13 pm
One more question I have about the dust storms: I've read that local dust storms typically take 2-3 days and reduce PV by around 80%. What about the larger, longer lasting dust storms?

There are global martian dust storms that can last for month.

see: https://en.wikipedia.org/wiki/Martian_soil#Atmospheric_dust

specifically: https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/PIA03170_fig1duststroms.jpg/800px-PIA03170_fig1duststroms.jpg
Sure, but the intensity isn’t super high for the whole month. Plenty of sunlight diffuses down to the ground.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/13/2018 01:48 pm
I see the only reason for massive power is for industrial use, metal smelting and such.  Solar/batteries would be fine for living areas and agricultural areas, and even rocket fuel production. 
Title: Re: Power options for a Mars settlement
Post by: josespeck on 04/13/2018 04:59 pm
Mars crops can be used to make batteries or capacitors of popcorn. Can ionic liquid be produced on Mars?.


 :-[   Forget to put the link:  https://pubs.acs.org/doi/10.1021/acsami.7b07746 (https://pubs.acs.org/doi/10.1021/acsami.7b07746)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/14/2018 08:05 am
One more question I have about the dust storms: I've read that local dust storms typically take 2-3 days and reduce PV by around 80%. What about the larger, longer lasting dust storms?

There are global martian dust storms that can last for month.

see: https://en.wikipedia.org/wiki/Martian_soil#Atmospheric_dust

specifically: https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/PIA03170_fig1duststroms.jpg/800px-PIA03170_fig1duststroms.jpg
And keep in mind Musks goal of a growing settlement.

I'd suggest that PV array mfg should be an early target for ISRU regardless of what PV technology is chosen.
Here's some facts culled from earlier posts to remind people of the scale of the problem.
Quote
The actual current SoA for large arrays (from a powerpoint from Jess Sponable on the Evolved DC-X thread) is actually about 7W/Kg (ISS). He was working (at DARPA) on blankets pushing 300W/Kg.

----
So roughly speaking you're looking for each 100 new people to add between 500KW and 6MW to the power budget.

Just to be clear that's a minimum of 2.5x the size of the ISS PV array and about 1000x the largest reactor the US has ever flown in space, and 100x the biggest the USSR ever flew.

---
So you're starting at between 493W and 590W (according to Colorado U.) at Mars.  In 2016 world record (1st solar CdTe) was 22.1%, giving about 108-130W/m^2

A minimal power level is 500Kw/100 people is 4630 m^2 worst case. So 10x that is 46300 m^2, a square about 216m on a side, per 100 people. At 60Kw/person it's 12x those numbers.

TBF it looks like dust does a lot of scattierng but little absorbing and a figure of 50w/m^2 in a dust storm may be reasonable
And 50w/m^ gives 11W/m^2 output with thin films.
World record level efficiencies (c43%) use triple junction space grade cells with concentrators which are very expensive and difficult to make.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/14/2018 12:57 pm
I see the only reason for massive power is for industrial use, metal smelting and such.  Solar/batteries would be fine for living areas and agricultural areas, and even rocket fuel production.
propellant production IS massive industrial use. It just turns out to be easy to modulate for available power.

And don’t underestimate solar+batteries for industrial uses, either. A small mass of thinned solar cells can provide a tremendous amount of power.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/14/2018 01:03 pm
What about metal smelting.  This will take a huge amount of heat.  We know Mars has iron from the red dust.  What about aluminum, even titanium.  Aluminum has a melting point somewhere in the 1100 degree F range while titanium is around 3500 degrees F.  Both will be needed, but titanium and iron/steel production will take a lot of heat thus a huge amount of power will be needed to do this. 
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 04/14/2018 03:47 pm
What about metal smelting.  This will take a huge amount of heat. 

Some thermites are used for metal refining and welding. My dad used thermite to weld a cracked tractor engine block, a method he picked up  during WW-2 to repair Jeep & aircraft engines, and I guarantee you it's hot enough 😨

The oxide he used was iron oxide, rust,  and I believe Mars is awash in it. Fuel: powdered aluminum.

Fe2O3 + 2 Al → 2 Fe + Al2O3

Liquid iron, on the half-shell, with gobs of residual heat for other uses.

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/14/2018 04:17 pm

Some thermites are used for metal refining and welding. My dad used thermite to weld a cracked tractor engine block, a method he picked up  during WW-2 to repair Jeep & aircraft engines, and I guarantee you it's hot enough 😨

The oxide he used was iron oxide, rust,  and I believe Mars is awash in it. Fuel: powdered aluminum.

Fe2O3 + 2 Al → 2 Fe + Al2O3

Liquid iron, on the half-shell, with gobs of residual heat for other uses.
Historically this was SOP for railroad welding repairs.

Of course the problem is where you get the raw Aluminum powder from in the first place, which is even more energy intensive than Iron, and can't be reduced using coke.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 04/14/2018 06:27 pm

Some thermites are used for metal refining and welding. My dad used thermite to weld a cracked tractor engine block, a method he picked up  during WW-2 to repair Jeep & aircraft engines, and I guarantee you it's hot enough 😨

The oxide he used was iron oxide, rust,  and I believe Mars is awash in it. Fuel: powdered aluminum.

Fe2O3 + 2 Al → 2 Fe + Al2O3

Liquid iron, on the half-shell, with gobs of residual heat for other uses.
Historically this was SOP for railroad welding repairs.

Of course the problem is where you get the raw Aluminum powder from in the first place, which is even more energy intensive than Iron, and can't be reduced using coke.

The base will inevitably have big cranes. If you have BFS's which will stay forever, and the "stay" vehicles can be separated into their modules (likely), the thrust structure will be chock full of aluminum-lithium and engine spares. Remove the cargo/passenger compartment for habitation, and use the tank modlue for prop storage. Separating the alloy has been done.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/14/2018 07:01 pm
What about metal smelting.  This will take a huge amount of heat.  We know Mars has iron from the red dust.  What about aluminum, even titanium.  Aluminum has a melting point somewhere in the 1100 degree F range while titanium is around 3500 degrees F.  Both will be needed, but titanium and iron/steel production will take a lot of heat thus a huge amount of power will be needed to do this.
Iron can be smelted with carbon monoxide, which is easier to make on Mars than even hydrogen is. But Mars is also awash in already-smelted meteoric iron which just needs to be melted or sintered.
Title: Re: Power options for a Mars settlement
Post by: aero on 04/14/2018 08:37 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 04/14/2018 10:06 pm
Mars-sourced meteors which found their way to Earth have been found to contain carbon.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/14/2018 10:17 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 04/14/2018 10:42 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.
You will also need O2 deposits, I think.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/14/2018 10:44 pm
You can get O2 from CO2. 
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/14/2018 10:49 pm
You can get O2 from CO2.

You can get oxygen and CO from the atmosphere by liquefaction or other techniques, it's at around the 0.1% level.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/14/2018 11:28 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
Of course. Carbon can be made electrolytically from CO2.
Title: Re: Power options for a Mars settlement
Post by: gideonlow on 04/15/2018 06:03 am
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.

Can you share a source for these reports?  I noticed you made the same claim in other threads.  I've seen speculation about underground clathrates being part of potential methane cycles, but nothing so dramatic as confirming "methane deposits being found" . . .
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/15/2018 01:49 pm
Been doing some more reading into the ISRU/Sabatier side of things.

This paper by PCI is a great baseline for experimental Martian ISRU reactors: https://ttu-ir.tdl.org/ttu-ir/bitstream/handle/2346/67656/ICES_2016_308.pdf?sequence=1

They assume a PV system to power the Sabatier reactor, and did a 1000-hour test with several start/stop cycles to validate their system was compatible with a variable power source like PV.

Quote
This paper describes and experimentally demonstrates that the implementation of a Microlith-based regenerable
CO2 adsorber and efficient Sabatier reactor system can be significantly beneficial for producing fuel and oxygen
from the Martian atmosphere (for ISRU application) with high CO2 conversion and high CH4 selectivity at low
system size/weight and low overall power consumption. The methane produced by the Sabatier reactor can be combined with methane and high hydrocarbons collected from the regolith off-gases, and can be fed to a solid oxide
stack system implementing a Microlith-based reformer concept for generating power.

NASA's Design Reference Architecture 5.0 is also definitely worth a read: https://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf

NASA's design architecture isn't really compatible with SpaceX's objectives, though:

1. It describes using nuclear power for surface generation, not solar

2. ISRU methane production is only used for the Descent/Ascent Vehicle; Mars-Earth transfer cruise is powered by nuclear thermal rockets
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/17/2018 03:37 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.

Can you share a source for these reports?  I noticed you made the same claim in other threads.  I've seen speculation about underground clathrates being part of potential methane cycles, but nothing so dramatic as confirming "methane deposits being found" . . .
Sorry for the delay. I think we've seen the same thread.

here (https://forum.nasaspaceflight.com/index.php?topic=44508.0)

And in the thread I did say if confirmed it could be huge. I note it in the "Advanced Concepts" thread, rather than the Mars HSF or SpaceX Mars sections.

A ready large scale source of fuel would make life a lot easier. Refueling becomes a process of warm (to extract the Methane), filter for impurities, cool for loading.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/17/2018 11:54 pm
But then you have to transport large amounts of fuel to Mars, and you also have to develop a very different ISRU procedure. Better to build the real ISRU capability. It requires a lot of power, but also provides plenty of power (even during dust storms) for the rest of the outpost. It can be reused for the next flight, too, instead of spending a whole bunch mass on something you burn up.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/18/2018 06:50 am
MIT Aims To Bring Nuclear Fusion To The Market In 10 Years

http://www.wbur.org/bostonomix/2018/03/09/mit-nuclear-fusion

https://www.engadget.com/2018/03/09/mit-embarks-ambitious-plan-build-nuclear-fusion-2033/

For some context and background on those articles

https://www.youtube.com/watch?v=L0KuAx1COEk

https://www.youtube.com/watch?v=KkpqA8yG9T4

TL;DR: commercial availability of continuously improving magnetic field and current density compatible high temperature superconductors. 
Basically the remaining job is commercializing the specific integration of the commercial off-the-shelf technologies in modern start-up fashion, quickly and efficiently.

It seems reasonable to expect these aspirations to be met. This would make these commercial reactor technologies available for the aerospace community to lightweight for airlift and space-lift compatible versions.

Edit: disambiguating field strength and current density
Or these guys, maybe?
http://seattlebusinessmag.com/technology/redmond%E2%80%99s-helion-energy-looks-nuclear-fusion-next-big-thing-power-generation
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 04/18/2018 07:01 am
MIT Aims To Bring Nuclear Fusion To The Market In 10 Years

http://www.wbur.org/bostonomix/2018/03/09/mit-nuclear-fusion

https://www.engadget.com/2018/03/09/mit-embarks-ambitious-plan-build-nuclear-fusion-2033/

For some context and background on those articles

https://www.youtube.com/watch?v=L0KuAx1COEk

https://www.youtube.com/watch?v=KkpqA8yG9T4

TL;DR: commercial availability of continuously improving magnetic field and current density compatible high temperature superconductors. 
Basically the remaining job is commercializing the specific integration of the commercial off-the-shelf technologies in modern start-up fashion, quickly and efficiently.

It seems reasonable to expect these aspirations to be met. This would make these commercial reactor technologies available for the aerospace community to lightweight for airlift and space-lift compatible versions.

Edit: disambiguating field strength and current density
Or these guys, maybe?
http://seattlebusinessmag.com/technology/redmond%E2%80%99s-helion-energy-looks-nuclear-fusion-next-big-thing-power-generation

Seriously curious: Fusion research has been plodding along for the last 70 years and now there seems to be a sudden rush of commercial interest. Did something change recently that brought the promise of a working reactor that much closer to reality? Is it just a lot of cheap money sloshing around or are venture capitalists on the scent of the next big thing?
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/18/2018 09:41 am
Seriously curious: Fusion research has been plodding along for the last 70 years and now there seems to be a sudden rush of commercial interest. Did something change recently that brought the promise of a working reactor that much closer to reality? Is it just a lot of cheap money sloshing around or are venture capitalists on the scent of the next big thing?

For most of the last 70 years, fusion has been getting every closer to breakeven, then it stalled some 20 years ago, as the 'easy' route - which was to make things bigger - became intractably expensive, needing massive supra-national designs - ITER.
At the time ITER was being designed, there was no alternative to the simple metallic superconductors used.

The above MIT design uses newer superconductors, which are off the shelf (https://www.alibaba.com/product-detail/2-Generation-High-Temperature-Superconductor-tape_50013334401.html) and allows a higher field to be used, meaning the dimension shrinks down lots, making everything easier.

This leads to a gigawatt thermal in a package of a thousand tons, not like ITER, with a hundred megawatts thermal in a few hundred thousand tons.

I strongly recommend the above video.
The core of the reactor fits in BFS, for scale.

19-26 minutes in is 'how to rate fusion approaches' and is particularly recommended.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/18/2018 10:34 am
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.
You will also need O2 deposits, I think.

Or perchlorates.  There is no reason the oxidizer has to be O2.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/18/2018 05:49 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.
You will also need O2 deposits, I think.

Or perchlorates.  There is no reason the oxidizer has to be O2.

All you need is accessible materials that contain the right elements mostly Hydrogen, Oxygen, Carbon and Nitrogen. These are present in the atmosphere or in water ice under the surface. The rest is just chemistry and finding enough energy for the reactions. In the case of methane, electrolysis of water to get at the hydrogen and oxygen will be the energy intensive part as the Sabatier reaction is exothermic.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 04/18/2018 05:54 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.
You will also need O2 deposits, I think.

Or perchlorates.  There is no reason the oxidizer has to be O2.

All you need is accessible materials that contain the right elements mostly Hydrogen, Oxygen, Carbon and Nitrogen. These are present in the atmosphere or in water ice under the surface. The rest is just chemistry and finding enough energy for the reactions. In the case of methane, electrolysis of water to get at the hydrogen and oxygen will be the energy intensive part as the Sabatier reaction is exothermic.
The potential methane deposits where presented as an energy source for the Mars settlement. If you need another energy source to extract an oxidizer, then it's easier to just use the other energy source directly.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 04/18/2018 06:11 pm
The above MIT design uses newer superconductors, which are off the shelf (https://www.alibaba.com/product-detail/2-Generation-High-Temperature-Superconductor-tape_50013334401.html) and allows a higher field to be used, meaning the dimension shrinks down lots, making everything easier.

Anxiously awaiting "Economics of Deploying Fusion from EBay" thread.   ;)
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/18/2018 07:53 pm
The above MIT design uses newer superconductors, which are off the shelf (https://www.alibaba.com/product-detail/2-Generation-High-Temperature-Superconductor-tape_50013334401.html) and allows a higher field to be used, meaning the dimension shrinks down lots, making everything easier.

Anxiously awaiting "Economics of Deploying Fusion from EBay" thread.   ;)

Anyone putting undeveloped technically hardware - especially nuclear related, which at best going to be expensive to develop with a history of delays - in the critical path of anything they actually want to happen needs reeducation.

Perhaps some hard labour in the lithium mines.

Fusion would be great - but solar is quite adequate near-term.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/18/2018 08:28 pm
Anyone putting undeveloped technically hardware - especially nuclear related, which at best going to be expensive to develop with a history of delays - in the critical path of anything they actually want to happen needs reeducation.

Perhaps some hard labour in the lithium mines.

Fusion would be great - but solar is quite adequate near-term.

I fully agree. But then there are signs that maybe betting fully on solar and battery backup may turn out wrong. Fusion may disappoint again but I would not rule out that in 20 years it will be on the way to become the main source of energy for our industry.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 04/18/2018 09:15 pm
^^ and ^

Booo!!!  I was quipping re: sd's really cool thread elsewhere.  Apologies!!!    :o ??? 8)
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/18/2018 09:51 pm
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.
You will also need O2 deposits, I think.

Or perchlorates.  There is no reason the oxidizer has to be O2.
This is a very good point. If methane deposits ARE found, they could be reacted with the perchlorate deposits.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/18/2018 10:48 pm
Anyone putting undeveloped technically hardware - especially nuclear related, which at best going to be expensive to develop with a history of delays - in the critical path of anything they actually want to happen needs reeducation.

Perhaps some hard labour in the lithium mines.

Fusion would be great - but solar is quite adequate near-term.
Agreed.  Nuclear development is nowhere in SX's known skillset.

OTOH the Kilopower programme seems to be (quietly) proceeding.  I know, it's only a 10Kw unit, but
a) Once you can build one, you can build more. It's granular in power usage (it's even crew portable, if you have a crew of about 4-6).
b) The design has "stretch." At least to 100Kw, maybe to 1MW.  But 10Kw gives you a decent sized power supply for an ion thruster, then on site power out to Pluto or beyond. 
c) NASA seems pretty keen on it going forward. The only question is will it be ready for the first launch. By Jan 1st 2023 we'll have the answer to that.

Obviously 100Kw, or 1MW radically changes the game, but I don't think they can make a case to go that large this early.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/18/2018 11:28 pm
Nuclear is a hard sell for powering SpaceX's plans. Not really feasible at kilopower scale as it's too costly.

But SpaceX will DOUBTLESSLY be partnering with NASA and others. NASA may want to fly kilopower for the technology maturation alone (i.e. as a tech demo), and SpaceX may be able to use it for free (in exchange for flying it there and providing plenty of data).

Additionally, if nuclear can scale up, cost per watt should drop.

And if SpaceX's ISRU starts requiring a lot of thermal input, then nuclear starts looking a lot better than it otherwise would compared to PV, as you get 3 to 4 times the heat output of a thermally-optimized unit as you would an electrically optimized one, and you also save the expense and weight of the heat engine and dynamo and (potentially) radiator. It might weight just a fifth the mass of an electrical one with the same thermal output.

Solar+battery is a MUCH better solution than a lot of space fans and experts think (even on Mars), but nuclear is definitely very nice to have, and SpaceX would doubtless love to have it if given it for free.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/19/2018 12:37 am
can they get carbon in a form that can be used to make carbon steel from the iron?
What happened to reports of large Methane deposits being found?

That would change everything in terms of settlement viability.
You will also need O2 deposits, I think.

Or perchlorates.  There is no reason the oxidizer has to be O2.

All you need is accessible materials that contain the right elements mostly Hydrogen, Oxygen, Carbon and Nitrogen. These are present in the atmosphere or in water ice under the surface. The rest is just chemistry and finding enough energy for the reactions. In the case of methane, electrolysis of water to get at the hydrogen and oxygen will be the energy intensive part as the Sabatier reaction is exothermic.
The potential methane deposits where presented as an energy source for the Mars settlement. If you need another energy source to extract an oxidizer, then it's easier to just use the other energy source directly.
This is the thread where Mars Methane Clathrates are discussed: https://forum.nasaspaceflight.com/index.php?topic=44508.0 (https://forum.nasaspaceflight.com/index.php?topic=44508.0)
Including some chemistry, and oxidation and perchlorates etc...
Title: Re: Power options for a Mars settlement
Post by: DAZ on 04/19/2018 03:32 am
I’m probably going to regret posting this as it’s a little long.  Additionally, the longer a post more likely it is that I will have made a mistake.  But in the interest of furthering the conversation, I will foolishly wade in, or maybe more accurately jump.

I have become disappointed with this thread.  Power will be THE most important item for a Mars settlement.  Power will be the limiting factor for growth and sustainability.  Power will set the standard of living and essentially limit what can and cannot be built.  The limiting scale on how fast you can grow on Mars is power.  About everything else can be scaled quickly if you have the power. If one megawatt of power were available initially, it would be quickly exceeded. In short, you cannot have too much power nor can you get it to Mars too fast. 

Initially, the power will probably come from solar photovoltaic and batteries.  These have advantages of flexibility of packaging, and almost no startup power is required.  This low startup power requirement is underappreciated.  The problem with solar with batteries is that it doesn’t scale to the same extent as quickly as other options.  You very quickly end up covering 25 square miles.  The battery power system starts to become massive to account for the day-night cycle alone.  You then start to need a massive power distribution system a.k.a. a power grid.  These type of systems start to require a very large amount of upkeep and support.  It becomes difficult to move the power where you need to, for example, your ice mining is 100 miles away from your settlement, and your fuel manufacturer is 10 miles away from the settlement.  It also limits how far away you can look for resources because you need the power.  Even with beamed power from space you’re still not going to be as flexible as having your power generation at the site you need the power.

This naturally leads to other power generation systems like nuclear fusion or fission systems.  You could obviously put one of these at each site and build additional ones as quickly as you can bring the parts.

The option for nuclear fusion until recently wasn’t really realistic.  As others have mentioned, these fusion power plants were almost too big to build on earth let alone on Mars.  Minimum working size of these power plants was like 1 GW.  With the advent of high-temperature superconductors, it now seems possible to scale down into the 500 kW to 1 MW range.  The reactor alone may take one or 2 ships to get there, but the actual power generation and cooling might take several more.  One of the safety advantages of the fusion power plant is that it takes power to run the plant.  If you have a problem, you just shut down the power plant, so it is inherently safe.  But this is also one of the big drawbacks for using one of these systems on Mars.  You will need to heat up the breeder material which is also the coolant.  Then you’ll need to preheat your power generation side of the system.  This will take hundreds of kilowatts over something like a half an hour to an hour.  You will then have to start up the fusion reactor to its breakeven point.  This will require someplace in the vicinity of 500 kW to 1 MW.  On earth, this would not be a problem you pull the power off the power grid.  But until you have megawatts of power being generated on Mars, you can’t even start the fusion reactor.

This leads on to fission systems.  Some of the systems discussed like the kilowatt power system require almost no startup power.  The problem with these systems is they don’t scale very well or don’t become very efficient until they are very large.  This also makes them much more expensive to put in.  The path of using uranium 235 and uranium 238 and on to plutonium was that this was the path that allowed you to breed plutonium for bombs.  This drove the design for the reactors that are mostly used at this time.  These light water reactors are not the most efficient designs.  This also makes the fuel very expensive.  This would appear to point against the use of reactors on Mars, but there is another option for this.

The law of the instrument: “When the only tool you have is a hammer you tend to treat everything as if it were a nail.”  The need for all of these reactors and their designs was fundamentally due to the requirement to make nuclear weapons as cheaply and quickly as possible.  So most of the people looking at these problems had only one hammer and treated the entire problem as a nail.  This is the same problem that Elon Musk had to overcome.  All the rocket designs were based on ICBMs which are inherently munitions.  You use a munition exactly one time, so this drives the entire mindset and how you would make rockets work.

About the only way to avoid the law of the instrument is to go back to 1st principles.  This is what Elon Musk has done and had such success with.  He went back and looked at every part, not as if a munition but as something that was going to be repeatedly used.  An example of this is the avoidance of using explosive separators (which is by definition a munition) and went with pneumatic separators.  Everything about the systems was looked at from the ground up with a new eye toward costs.

Many others are now starting to do this with various nuclear power options.  They are talking about using the thorium cycle in the thermal neutron range.  They would use molten salts which greatly increases the efficiencies while decreasing the size and the cost.  These designs are inherently walk away safe.  Additionally, for someplace like Mars, they are totally sustainable as the fuel can be mined and refined on Mars.  To do the same thing with the uranium cycle, you would need to build massive isotope separators.  You cannot scale these small, you have to be massive and power-hungry.  It is one of the more expensive and difficult industrial processes we do on earth and one of the primary constraining factors on somebody building a nuclear bomb.  Using the thorium cycle in the thermal neutron range, you can build sustainable reactors much sooner.  It should be theoretically possible to build the smallest reactors in the 100-kilowatt size in either scale up or build them modular.  Building them in small modular systems allows you to more easily transport and package them while giving you inherently better redundancy with lower spare parts costs.

There are also advantages that can be used with the waste heat as these reactors run at much higher temperatures than light water reactors.  There’s talk about using it to improve the efficiencies of separating hydrogen from the oxygen from water.  So this would improve your efficiencies in the fuel manufacturing process.  Additionally, the waste heat could be used directly in your ice mining.  This would not only improve the speed of the mining but the efficiency of the reactor itself.

The real beauty of these thorium reactors is that SpaceX doesn’t have to be paying the startup design money for them.  There are dozens of groups and companies already looking into actually building these things.  They want to build larger ones in the United States in the hundreds of megawatt-class, but others want to build them in the hundreds of kilowatt classes to be used in Third World countries.  Many of the environmental groups are starting to see the need for reactors like these and are already starting to try to change the minds of the other environmentalists.  The other advantage of the smaller sizes is they can be built in factories easing transport and greatly reducing the costs.

Even if the United States and Europe don’t get onto this new nuclear technology other countries are pursuing it to a massive amount.  India is now looking at building these reactors today.  They’ve already started building some test reactors.  China is spending billions of dollars on this technology alone.  If nobody else does it, China absolutely will accomplish it.

Some may say that the US will never allow SpaceX to launch such a system.  And in reality other than stopping them from going to Mars they might not be able to stop them.  If they don’t build such a reactor in the United States, they’ll go to China and have them build the reactor.  If the US government won’t let them launch the nuclear fuel which by the way is so unbelievably intrinsically safe as to why would you bother regulating it?  SpaceX could have the Chinese launched just the fuel on their rocket and meet up with it in orbit.

The bottom line to all this is that the sooner they start planning on using the small reactors, the faster the entire Mars colony will grow.  Spending too much time fooling around with other power systems will just be slowing the process.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/19/2018 04:34 am
Initially, the power will probably come from solar photovoltaic and batteries.  These have advantages of flexibility of packaging, and almost no startup power is required.  This low startup power requirement is underappreciated.  The problem with solar with batteries is that it doesn’t scale to the same extent as quickly as other options.  You very quickly end up covering 25 square miles.  The battery power system starts to become massive to account for the day-night cycle alone.  You then start to need a massive power distribution system a.k.a. a power grid.  These type of systems start to require a very large amount of upkeep and support.  It becomes difficult to move the power where you need to, for example, your ice mining is 100 miles away from your settlement, and your fuel manufacturer is 10 miles away from the settlement.  It also limits how far away you can look for resources because you need the power.  Even with beamed power from space you’re still not going to be as flexible as having your power generation at the site you need the power.

This is very close to an argument that industry on earth is impossible.

The problem with this is once you start to put numbers on it, at the most pessimistic case - literally buying the parts from online vendors in one-off-quantity pricing, and assuming the IAC2017/16 like lift costs, you end up with a price per kWh for a system that lasts for 20 years of $0.3/kWh or so. (explored here (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512).

With even slight martian capability, such as the ability to extract iron in very small quantities for stands and frames, and slightly upgraded solar panel design, this goes to $0.15/kWh.
I note that US steelworks exist at a price of $0.04/kWh or so, at the half gigawatt level.

Your 40 ton (say) 1MW reactor needs to cost under $15M or so, or solar is cheaper.

Methane/oxygen as an energy transport medium is also a possibility.

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/19/2018 04:39 am
74,000,000 square miles are used for agriculture on Earth. I really don't think a few square miles for solar (which is just a kind of agriculture, just using photovoltaics instead of photosynthesis) is going to be that much of a problem for Mars (which has about the same land area as Earth). The area argument against solar is tired and not actually true when judged in proportion to other uses of land (particularly agriculture). And this applies much more strongly on Mars.

From a mass perspective, solar is superior to nuclear on Mars. And solar+batteries are a very good solution.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/19/2018 04:43 am
The option for nuclear fusion until recently wasn’t really realistic.  As others have mentioned, these fusion power plants were almost too big to build on earth let alone on Mars.  Minimum working size of these power plants was like 1 GW.  With the advent of high-temperature superconductors, it now seems possible to scale down into the 500 kW to 1 MW range.  The reactor alone may take one or 2 ships to get there, but the actual power generation and cooling might take several more.  One of the safety advantages of the fusion power plant is that it takes power to run the plant.  If you have a problem, you just shut down the power plant, so it is inherently safe.  But this is also one of the big drawbacks for using one of these systems on Mars.  You will need to heat up the breeder material which is also the coolant.  Then you’ll need to preheat your power generation side of the system.  This will take hundreds of kilowatts over something like a half an hour to an hour.  You will then have to start up the fusion reactor to its breakeven point.  This will require someplace in the vicinity of 500 kW to 1 MW.  On earth, this would not be a problem you pull the power off the power grid.  But until you have megawatts of power being generated on Mars, you can’t even start the fusion reactor.
This is not the case for the Helion Energy fusion reactor, I posted earlier. Their reactor directly converts the fusion energy into electricity. This works because the result of the D + He3 fusion reaction are charged particles. The energy from the fusion reaction presses them back out through the magnetic field that accelerated and compresses them. You move a charged particle through a magnetic field, you induce a current. So they don't need a steam cycle like D+T power plants do. Don't worry about the He3 either. The plant fuses D+D initially, which creates a helion in one branch. That helion is then fed back into the reactor for the next cycle. The other branch creates a triton, which has a half life of 12 years and then decays into another helion.
They are also quite close to a working full scale reactor prototype (end of the year) and their reactors will be relatively small and compact and produce about 50MWe.
Here is the link again (I think it went under in the quote earlier):
http://seattlebusinessmag.com/technology/redmond%E2%80%99s-helion-energy-looks-nuclear-fusion-next-big-thing-power-generation
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/19/2018 04:45 am
Let's see break even, then we can talk about fancy power conversion schemes and low-neutron fuels. Until breakeven, nothing matters.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/19/2018 04:48 am
Let's see break even, then we can talk about fancy power conversion schemes and low-neutron fuels. Until breakeven, nothing matters.
If you read the article, you would see that they want to have a full scale break even (or better) reactor prototype built by the end of the year (then it will take them a few months to get to full power, I presume).
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/19/2018 04:55 am
Good, then I will start being interested in it. We've been hearing this sort of thing from alt-fusion people for decades, and from the regular fusion community for even longer.

But I'm serious: everything but breakeven is basically a distraction. You know why? Because once you demonstrate break-even, you'll have plenty of interest and cash for follow on capabilities. You'll be fighting off investors with a stick (although I wouldn't be one of them). So don't worry about anything but a convincing breakeven.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/19/2018 05:02 am
Good, then I will start being interested in it. We've been hearing this sort of thing from alt-fusion people for decades, and from the regular fusion community for even longer.

But I'm serious: everything but breakeven is basically a distraction. You know why? Because once you demonstrate break-even, you'll have plenty of interest and cash for follow on capabilities. You'll be fighting off investors with a stick (although I wouldn't be one of them). So don't worry about anything but a convincing breakeven.
They have full (30 million) funding for the full scale prototype now, because the experiments that they have done until now have convinced investors that they can do it. I have known them for a while (so has Jon Goff) and I am very sure that they can do what they say they can do.
Also worth noting is that they have not made any promises over the past 4 years or so, because they wanted to avoid too much hype. So the fact that they are letting this out know, is quite significant.

And if they fail, then Tokamak Energy is the next in line with break even experiments planned for 2020. Though that is a traditional D+T tokamak with all the issues that come with it.
There is one more player that has me exicted is Prof Uri Shumlak's Sheared Flow Stabilized Z- Pinch. They are about to spin off from the UW (like Helion did) and their device is extremely small. Their latest test device FuZE seems to match predictions for scaling laws. They are currently at 200 kA input current. They only need 650 kA for break even. FuZE went from 50 to 200 kA so far and will go all the way to 300 by the time funding from ARPA- E runs out.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/19/2018 05:03 am
The flip side of not making any promises is you can't be proven wrong.

I'll make a bet against them achieving break even within the year.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/19/2018 05:08 am
The flip side of not making any promises is you can't be proven wrong.

I'll make a bet against them achieving break even within the year.
They will have the reactor ready by the end of the year. I would assume that it will be a few months until the thing has run its course to optimum settings. It is hard to say, but based on previous experiments, I would expect break even NET mid 2019, more likely closer to the end of 2019 or beginning of 2020, though.
Also worth noting that they expected to be there earlier, but funding realities required them to do smaller scale experiments first, to satisfy investors that their theories are sound.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/19/2018 05:23 am
This sounds really familiar. Okay, beer bet, then. No breakeven by end of 2019.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/19/2018 05:33 am
This sounds really familiar. Okay, beer bet, then. No breakeven by end of 2019.
I am not a betting man and this is a very hard task. So I would not make that bet myself, but for the fun of it, I will hold that bet, if only to maybe convince you to visit me in Michigan some day to claim that beer ;)
Title: Re: Power options for a Mars settlement
Post by: RonM on 04/19/2018 04:33 pm
This sounds really familiar. Okay, beer bet, then. No breakeven by end of 2019.

Safe bet.

I hate to be pessimistic, but we've been hearing about fusion break even for decades. It would be great if it happened next year, but I wouldn't be surprised if it doesn't happen in twenty years.

Since Musk wants to land the first BFS on Mars in less than a decade, we need to be discussing what can be ready to deploy very soon. Even if there's a big fusion success next year, production power reactors won't be ready for the initial settlement.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 04/19/2018 06:52 pm
Nuclear is a hard sell for powering SpaceX's plans. Not really feasible at kilopower scale as it's too costly.

But SpaceX will DOUBTLESSLY be partnering with NASA and others. NASA may want to fly kilopower for the technology maturation alone (i.e. as a tech demo), and SpaceX may be able to use it for free (in exchange for flying it there and providing plenty of data).

Additionally, if nuclear can scale up, cost per watt should drop.

And if SpaceX's ISRU starts requiring a lot of thermal input, then nuclear starts looking a lot better than it otherwise would compared to PV, as you get 3 to 4 times the heat output of a thermally-optimized unit as you would an electrically optimized one, and you also save the expense and weight of the heat engine and dynamo and (potentially) radiator. It might weight just a fifth the mass of an electrical one with the same thermal output.

Solar+battery is a MUCH better solution than a lot of space fans and experts think (even on Mars), but nuclear is definitely very nice to have, and SpaceX would doubtless love to have it if given it for free.

Or even not for free, as long as they don't have to develop it all by themselves. All the national space agencies have better access to nuclear development, and might want to develop it and share it with SpaceX in return for launch services.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/19/2018 07:39 pm
Or even not for free, as long as they don't have to develop it all by themselves. All the national space agencies have better access to nuclear development, and might want to develop it and share it with SpaceX in return for launch services.
However AFAIK only 1 (NASA) has anactive space power reactor development programme running. 
The Kilopower test programme ended last month and it looks like NASA is close to making announcement on it.

https://forum.nasaspaceflight.com/index.php?topic=45509.0

Something tells me that if it wasn't pretty positive they wouldn't be that keen on getting press attention for it.

 I think it's gone well and I hope it's flushed out any glitches in the design (it's the first reactor designed for space use in the US since the early 60's. It'd be frankly amazing if there were no issues at all. The old X-plane rule that "if you haven't broken one you're not testing them hard enough" comes to mind ).

Recall NASA has a number of internal programmes that would like to use something like, but it's been a chicken and egg situation. Programmes wanted it but it wasn't available and developers wanted to do it but project managers couldn't commit a payload to using something that didn't exist (yet). Everyone's unhappy but no one can figure out what to do about it.  :(

Kilopower has been an amazing project for NASA, given what it's close to delivering for the size of budget.

That said I think they'd expect SX to pay something per unit to offset some of those costs.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/19/2018 08:08 pm
My speculation... A NASA team of several astronauts, one or two Kilopower reactors.... on the first Human mission.
Quote from: john smith 19
That said I think they'd expect SX to pay something per unit to offset some of those costs.
Not "payment" as such, but the opportunity for NASA to have a key, valued role in the expedition, and not be just passengers, or scientist/explorers, or labour for SX to deploy. The NASA personnel would have their own expertise, and tasks to perform, to install connect maintain and evaluate the reactors.
Of course SX can have sufficient solar panels and batteries to cover the shortfall if the nulcear takes a while to come online... 
Of course the NASSA contingent could get stuck into everything else when their "baby" is happy.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/19/2018 09:50 pm
My speculation... A NASA team of several astronauts, one or two Kilopower reactors.... on the first Human mission.
Quote from: john smith 19
That said I think they'd expect SX to pay something per unit to offset some of those costs.
Not "payment" as such, but the opportunity for NASA to have a key, valued role in the expedition, and not be just passengers, or scientist/explorers, or labour for SX to deploy. The NASA personnel would have their own expertise, and tasks to perform, to install connect maintain and evaluate the reactors.
Of course SX can have sufficient solar panels and batteries to cover the shortfall if the nulcear takes a while to come online... 
Of course the NASSA contingent could get stuck into everything else when their "baby" is happy.

Nuclear is perhaps the hardest capability for a private company to develop. I wonder if the potential of spinning this as 'a vital component of' could limit NASA intrusion into the design of the core mission.

If it can't, it may be best not to take NASA money at all for any marsbase, and only offer contracted kilos on the ground.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/19/2018 10:08 pm
My speculation... A NASA team of several astronauts, one or two Kilopower reactors.... on the first Human mission.
Quote from: john smith 19
That said I think they'd expect SX to pay something per unit to offset some of those costs.
Not "payment" as such, but the opportunity for NASA to have a key, valued role in the expedition, and not be just passengers, or scientist/explorers, or labour for SX to deploy. The NASA personnel would have their own expertise, and tasks to perform, to install connect maintain and evaluate the reactors.
Of course SX can have sufficient solar panels and batteries to cover the shortfall if the nulcear takes a while to come online... 
Of course the NASSA contingent could get stuck into everything else when their "baby" is happy.

Nuclear is perhaps the hardest capability for a private company to develop. I wonder if the potential of spinning this as 'a vital component of' could limit NASA intrusion into the design of the core mission.

If it can't, it may be best not to take NASA money at all for any marsbase, and only offer contracted kilos on the ground.
I imagined that NASA probably wouldn't be able to transfer such technology easily or quickly, and this arrangement would give SX access to Kilopower.

It is true that power (and heat) from Kilopower reactors would be extremely useful, as people have said above, for ISRU, baseload, mining water by melting... etc.

NASA can claim to be making an important contribution, and not be publicly embarrassed by being shut out of the project. Plus its a nicer way to work (together).
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/20/2018 01:02 am
I hate to be pessimistic, but we've been hearing about fusion break even for decades. It would be great if it happened next year, but I wouldn't be surprised if it doesn't happen in twenty years.
A lot of the delays were because of the notoriously low funding for anything but tokamaks and those things are big and complicated and expensive mega projects that take a long time to develop. A lot has changed in the past 20 years, however and new designs and ideas have emerged along with new enabling technology.
One can not look back to predict the future. I mean, a few years ago, none of us would have worried about power options for a Mars settlement or would have expected fully reusable Mars space ships any time soon and look where we are now!

Since Musk wants to land the first BFS on Mars in less than a decade, we need to be discussing what can be ready to deploy very soon. Even if there's a big fusion success next year, production power reactors won't be ready for the initial settlement.
That is probably true, but then a success like that would result in a lot of interest from many parties (including NASA) and a lot of cash flow. All that could accelerate development a lot. Again, look what happened with RLV development in the last 10 years! Plus, even if there is no reactor ready for Mars 15 years from now, the colony will still be growing (assuming that enough people want to go) and so will the power requirements. They can start out with solar and batteries initially and then switch to fusion, once it becomes available.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/20/2018 01:51 am
This sounds really familiar. Okay, beer bet, then. No breakeven by end of 2019.
I am not a betting man and this is a very hard task. So I would not make that bet myself, but for the fun of it, I will hold that bet, if only to maybe convince you to visit me in Michigan some day to claim that beer ;)
Okay, so what are the terms? No Helios scientific breakeven before end of 2019 UTC.

I consider scientific breakeven to be total input power equal to power generated by fusion. That's easier than engineering breakeven, which takes into account the efficiency of converting the heat to electricity.


What I am NOT referring to is just input power to the pellet. It has to be wall-plug input power being equal to the heat of the generated fusion. Deal? If so, I will send an email to emailfuture.com to remind myself on January 1st, 2020.

Terms are: beverage or beer (value not to exceed $5 or so) to the winner, must be redeemed in person.
Title: Re: Power options for a Mars settlement
Post by: paramedikisto on 04/20/2018 02:17 am
Has anyone considered salvaging and using the nuclear reactors currently in orbit?  The Russians orbited over 30 reactors, most producing 2-3KW, and a couple larger ones that produced about 6KW (all electrical, the reactors produced much more thermal energy...which is also useful).  There was also SNAP-10A that the US launched, but it only produced about 500W.

My thought is that the reactors, or at least the cores (which were mostly ejected into a graveyard orbit) could be salvaged and transported to Mars, where the core or  even just the fuel rods could be placed into a reactor, ideally one specially constructed to accept multiple cores so as to obtain a greater output.  Doesn't seem like that difficult of an engineering task.

The advantage would be that these reactors get removed from orbit around the Earth, where they are a hazard, and will (after thousands of years) eventually decay and reenter the atmosphere.  There is also the advantage of not having the huge headache of launching nuclear material, and since under the OST the reactors are still property of Russia, they can be sold off by the government.

Title: Re: Power options for a Mars settlement
Post by: Ludus on 04/20/2018 04:13 am
I hate to be pessimistic, but we've been hearing about fusion break even for decades. It would be great if it happened next year, but I wouldn't be surprised if it doesn't happen in twenty years.
A lot of the delays were because of the notoriously low funding for anything but tokamaks and those things are big and complicated and expensive mega projects that take a long time to develop. A lot has changed in the past 20 years, however and new designs and ideas have emerged along with new enabling technology.
One can not look back to predict the future. I mean, a few years ago, none of us would have worried about power options for a Mars settlement or would have expected fully reusable Mars space ships any time soon and look where we are now!

Since Musk wants to land the first BFS on Mars in less than a decade, we need to be discussing what can be ready to deploy very soon. Even if there's a big fusion success next year, production power reactors won't be ready for the initial settlement.
That is probably true, but then a success like that would result in a lot of interest from many parties (including NASA) and a lot of cash flow. All that could accelerate development a lot. Again, look what happened with RLV development in the last 10 years! Plus, even if there is no reactor ready for Mars 15 years from now, the colony will still be growing (assuming that enough people want to go) and so will the power requirements. They can start out with solar and batteries initially and then switch to fusion, once it becomes available.

The Helion Fusion Engine concept has the great virtue that if it works, it’s ready to scale in the most effective way, as a mass produced compact 50 MW reactor. The speed that Elon has moved from PowerPoints to giant mandrels for carbon fiber on the BFR has rattled my cynicism about hopeful tech. A 50MW fusion reactor popping up that fits perfectly in that BFR would be just what the Heinlein novel version of the 2020’s calls for.

Mars even turns out to be oddly favorable for deuterium.
https://www.newscientist.com/article/dn22572-heavy-hydrogen-excess-hints-at-martian-vapour-loss/ (https://www.newscientist.com/article/dn22572-heavy-hydrogen-excess-hints-at-martian-vapour-loss/)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/20/2018 07:00 am
Has anyone considered salvaging and using the nuclear reactors currently in orbit?  The Russians orbited over 30 reactors, most producing 2-3KW, and a couple larger ones that produced about 6KW (all electrical, the reactors produced much more thermal energy...which is also useful).  There was also SNAP-10A that the US launched, but it only produced about 500W.

My thought is that the reactors, or at least the cores (which were mostly ejected into a graveyard orbit) could be salvaged and transported to Mars, where the core or  even just the fuel rods could be placed into a reactor, ideally one specially constructed to accept multiple cores so as to obtain a greater output.  Doesn't seem like that difficult of an engineering task.

The advantage would be that these reactors get removed from orbit around the Earth, where they are a hazard, and will (after thousands of years) eventually decay and reenter the atmosphere.  There is also the advantage of not having the huge headache of launching nuclear material, and since under the OST the reactors are still property of Russia, they can be sold off by the government.
Welcome to the site.

I think you'll find the Russian reactors were in the 10s of Kws. They wanted to run ocean surveillance radar from them. This is pretty thirsty.

As for recovering the cores and recyling the fuel. Let's see.

They are in high orbit. So you'll need significant delta v to find and catch them.

They will be intensively radioactive as they are strong neutron emitters.  During construction you could handle the fuel elements of the SNAP 10a with nothing but rubber gloves (watch the videos of it being assembled). A BFS which took one aboard (after running) however would be strongly  irradiated.

You now have to break the (different) designs down and extract the actual enriched fuel. No one's developed that technology WRT these designs. Never designed for disassembly. Either need high energy processes or aggressive chemicals, even if you just take them to Mars so you can do this in something like Earth gravity.

It sounds very wasteful, but IRL it's simpler and easier to do things this way.
However for Mars a sustainable nuclear programme would be a very different proposition.

PWR's are the most common reactor design on Earth. They make great power sources for ICBM carrying submarines operated by a state with a navy and a substantial nuclear weapons programme. But Mars has no free bodies of water. Those design choices are not really very relevant there.  Especially the one about the availability of enriched Uranium as fuel.
Title: Re: Power options for a Mars settlement
Post by: josespeck on 04/20/2018 09:44 am
74,000,000 square miles are used for agriculture on Earth. I really don't think a few square miles for solar (which is just a kind of agriculture, just using photovoltaics instead of photosynthesis) is going to be that much of a problem for Mars (which has about the same land area as Earth). The area argument against solar is tired and not actually true when judged in proportion to other uses of land (particularly agriculture). And this applies much more strongly on Mars.

From a mass perspective, solar is superior to nuclear on Mars. And solar+batteries are a very good solution.

NO.

http://www.fao.org/fileadmin/user_upload/newsroom/docs/en-solaw-facts_1.pdf (http://www.fao.org/fileadmin/user_upload/newsroom/docs/en-solaw-facts_1.pdf)
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/20/2018 10:08 am
74,000,000 square miles are used for agriculture on Earth. I really don't think a few square miles for solar (which is just a kind of agriculture, just using photovoltaics instead of photosynthesis) is going to be that much of a problem for Mars (which has about the same land area as Earth). The area argument against solar is tired and not actually true when judged in proportion to other uses of land (particularly agriculture). And this applies much more strongly on Mars.

From a mass perspective, solar is superior to nuclear on Mars. And solar+batteries are a very good solution.

NO.

http://www.fao.org/fileadmin/user_upload/newsroom/docs/en-solaw-facts_1.pdf (http://www.fao.org/fileadmin/user_upload/newsroom/docs/en-solaw-facts_1.pdf)

NO?
The actual cultivated area is around 7 million, not 70 million (which is the total land area).
Is this your only comment?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/20/2018 12:38 pm
74,000,000 square miles are used for agriculture on Earth. I really don't think a few square miles for solar (which is just a kind of agriculture, just using photovoltaics instead of photosynthesis) is going to be that much of a problem for Mars (which has about the same land area as Earth). The area argument against solar is tired and not actually true when judged in proportion to other uses of land (particularly agriculture). And this applies much more strongly on Mars.

From a mass perspective, solar is superior to nuclear on Mars. And solar+batteries are a very good solution.

NO.

http://www.fao.org/fileadmin/user_upload/newsroom/docs/en-solaw-facts_1.pdf (http://www.fao.org/fileadmin/user_upload/newsroom/docs/en-solaw-facts_1.pdf)
Thanks for making my point. About 37 percent of the world is used for agriculture in total, if you include grazing. I accidentally used total surface of the Earth instead of just land area, but thanks for providing data that backs up my point.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/20/2018 04:56 pm
Okay, so what are the terms? No Helios scientific breakeven before end of 2019 UTC.

I consider scientific breakeven to be total input power equal to power generated by fusion. That's easier than engineering breakeven, which takes into account the efficiency of converting the heat to electricity.
I think that they have a chance to achieve scientific break even. There are a couple of caveats. It could be that Helion will only use D+D for their tests. Their Fusion Engine is supposed to extract He3 from the D+D- reaction exhaust and feed it back into the reactor as fuel for the following shot. The problem is that D+D releases less energy than D + He3 would and the extraction system might not be part of this test reactor yet. Since He3 is also very expensive, they might only do D+D shots for their experiments and then convert the resulting energy release of that into what it would have been with D+ He3, at least until they have fully optimized everything. Unlike going from D+D to D+T, going from D+D to D+He3 is actually easier, because the neutron wall loading is a lot less (among other things) and they won't need FLiBe tanks and all those complicated things that are needed for D+T burning Tokamaks. It is merely a cost saving measure if they don't do that right away.
So, I would like to include that caveat in the bet: Scientific break even with D+D result converted to D+He3 result. If you are OK with that.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/20/2018 05:01 pm
The Helion Fusion Engine concept has the great virtue that if it works, it’s ready to scale in the most effective way, as a mass produced compact 50 MW reactor. The speed that Elon has moved from PowerPoints to giant mandrels for carbon fiber on the BFR has rattled my cynicism about hopeful tech. A 50MW fusion reactor popping up that fits perfectly in that BFR would be just what the Heinlein novel version of the 2020’s calls for.

Mars even turns out to be oddly favorable for deuterium.
https://www.newscientist.com/article/dn22572-heavy-hydrogen-excess-hints-at-martian-vapour-loss/ (https://www.newscientist.com/article/dn22572-heavy-hydrogen-excess-hints-at-martian-vapour-loss/)
Yes, that is what I have been thinking about too. Plus, the direct power conversion solves a lot of problems that would come with steam cycles. I believe that a single Helion reactor could be transported to Mars in anywhere between one and three BFS launches, depending on a few factors. Also worth noting that these reactors need so little fuel that you could send fuel for years along with any of these 3 launches and it would make no measurable difference in weight and volume.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 04/20/2018 08:57 pm
Thanks for making my point. About 37 percent of the world is used for agriculture in total, if you include grazing. I accidentally used total surface of the Earth instead of just land area, but thanks for providing data that backs up my point.

It's a good point.

At this point long removed from the effort, I won't attest to the whether I did it right and was accurate in calculations.  However, I once was trying to spitball the cost of a massive solar project as a layman's perspective on what we could have alternatively done with certain large government expenses since 2000 in certain troublesome areas.

My recollection is that I validated a variety of numbers from various sources and did a back-of-the-napkin calculation that the entire US annual energy electricity production could be replicated in a square solar-field 30 miles on a side (900 sq mi).  As I recall, this accounted for US Electrity Consumption, then-current Efficiency, reasonable assumption about Solar hours/day and weather, but perhaps not accounting for panel angle-to-the-sun and transmission losses.

The operative point I think being that it easier to do a lot with a little groundspace than you might expect.

As an aside, I think the cost of those 900 sq mi of Solar was significantly higher than the expenditures I was comparing against, but it wasn't ridiculously so and therefore may have been a worthwhile alternative investment particularly given what you get out the back side.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/20/2018 10:16 pm
Yep. I read on another thread here that the larger your habitat volume, the longer it takes for the O2 mix to become seriously depleted.

And I recall also seeing that "air pockets" last far, far longer than people think. 

http://www.vocativ.com/198502/underwater-air-pocket-yangtze-river/index.html
"Hexdall calculated that, in an air pocket the size of a U-Haul moving van, it would take about 79 hours before you lost consciousness."
Yes, but its not the lack of oxygen thats the problem. Its the carbon dioxide build up that will get you in trouble first long before you run out of oxygen.
So you need first after a while CO2 scrubbing, and then later begin to need oxygen supplementation.
separate to solving these, you could have individual or room sized emergency systems based on either scrubbing or exhausting CO2 rich "air", and O2 supplementation from pressurised storage.

But for larger community and working spaces, plus for resilience, and avoiding excessive disruption from dust storms etc, you have plants, (which unfortunately need light input, which will in a dust storm be largely from likely scarce electrical power). However they should be considered a key part in maintaining breathable air.

Then there is large scale chemical scrubbing. One look at Wikipedia https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber (https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber), gave several reactions the first is:
Quote from: wikipedia
The dominant application for CO2 scrubbing is for removal of CO2 from the exhaust of coal- and gas-fired power plants. Virtually the only technology being seriously evaluated involves the use of various amines, e.g. monoethanolamine. Cold solutions of these organic compounds bind CO2, but the binding is reversed at higher temperatures:

CO2  +  2 HOCH2CH2NH2  ↔  HOCH2CH2NH3+  +  HOCH2CH2NHCO2−

And since it is reversible, when the storm has passed and more energy is available the CO2 is recovered for use in Sabatier, and the monoethanolamine is recovered for use next time. This would be built into the ECLSS breathable air management system. I am no expert on this, but at first sight something like this would be an excellent and reusable buffer for periods of lacking light and energy. As for O2, just a large reserve of pressurised/liquid? O2, that is output earlier from Sabatier.

I hadn't seen this. (picture) My schoolboy chemistry guess.... at amines used for reversable CO2 capture. NASA has an experimental "Thermal Amine Scrubber" headding to the ISS on CRS-15

Although in the context of our above thread:
Quote from: wikipedia - Carbon dioxide scrubber
The dominant application for CO2 scrubbing is for removal of CO2 from the exhaust of coal- and gas-fired power plants.
Is the sort of scale needed for a large settlement.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/20/2018 11:18 pm
Okay, so what are the terms? No Helios scientific breakeven before end of 2019 UTC.

I consider scientific breakeven to be total input power equal to power generated by fusion. That's easier than engineering breakeven, which takes into account the efficiency of converting the heat to electricity.
I think that they have a chance to achieve scientific break even. There are a couple of caveats. It could be that Helion will only use D+D for their tests. Their Fusion Engine is supposed to extract He3 from the D+D- reaction exhaust and feed it back into the reactor as fuel for the following shot. The problem is that D+D releases less energy than D + He3 would and the extraction system might not be part of this test reactor yet. Since He3 is also very expensive, they might only do D+D shots for their experiments and then convert the resulting energy release of that into what it would have been with D+ He3, at least until they have fully optimized everything. Unlike going from D+D to D+T, going from D+D to D+He3 is actually easier, because the neutron wall loading is a lot less (among other things) and they won't need FLiBe tanks and all those complicated things that are needed for D+T burning Tokamaks. It is merely a cost saving measure if they don't do that right away.
So, I would like to include that caveat in the bet: Scientific break even with D+D result converted to D+He3 result. If you are OK with that.
It’s easier to achieve scientific breakeven with D+T, but if they truly achieve it with D+D (ie not just extrapolated based on being harder than D+T), then I’ll concede. Same with D+He3.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/21/2018 03:52 am
It’s easier to achieve scientific breakeven with D+T, but if they truly achieve it with D+D (ie not just extrapolated based on being harder than D+T), then I’ll concede. Same with D+He3.
[/quote]
I am not sure they will do D+He3 experiments and as I said, the output vs input of D+D is lower. So, it would be fair to let the extrapolate from the D+D results to what they would have been had they used D+He3. What really counts is the tripple product of confinement time, density and temperature. If they achieve enough of that for D+He3 fusion with a Q<1, then they have scientifically achieved break even, even if the reactor was only fueled by D+D. The rest is then a matter of replacing the fuel with He3. I am not sure it makes a lot of sense to spend the extra money for that until everything has been fully optimized, but maybe they will decide to do a few shots with He3 just to proof that they can actually do it practically and not just scientifically.
Personally, I would already be quite ecstatic if they managed to do just scientific break even. It would proof their physics and scaling laws. The rest is engineering and that will IMHO be solved quickly once the funding gates open after they have achieved that milestone.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/21/2018 05:36 am
Then no deal. Has to be actual scientific breakeven. Dealing with the Tritium (or helium3) is part of the difficulty, and we’ve been dealing with extrapolations for the last half century. (In fact, breakeven in a narrow sense has been achieved at NIF... the pellet received less energy than it produced via fusion... although that doesn’t include the efficiency of the lasers or all the laser light which missed the pellet.)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/21/2018 06:46 am

At this point long removed from the effort, I won't attest to the whether I did it right and was accurate in calculations.  However, I once was trying to spitball the cost of a massive solar project as a layman's perspective on what we could have alternatively done with certain large government expenses since 2000 in certain troublesome areas.

My recollection is that I validated a variety of numbers from various sources and did a back-of-the-napkin calculation that the entire US annual energy production could be replicated in a square solar-field 30 miles on a side (900 sq mi).  As I recall, this accounted for US Electrity Consumption, then-current Efficiency, reasonable assumption about Solar hours/day and weather, but perhaps not accounting for panel angle-to-the-sun and transmission losses.

The operative point I think being that it easier to do a lot with a little groundspace than you might expect.

As an aside, I think the cost of those 900 sq mi of Solar was significantly higher than the expenditures I was comparing against, but it wasn't ridiculously so and therefore may have been a worthwhile alternative investment particularly given what you get out the back side.
Just to note

That's about 1/2 million acres of land.

What happens when the sun sets?

Cut the starting sunlight by about 1/2 for Mars.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/21/2018 08:12 am
If you're thinking of new power sources for agriculture enabling things, think what it actually enables if freight is costing $130/kg.

In order to make it worth it growing food, you need to get under $130/day/person or so to compete with dried foods, shipped from earth).

Baseline calories from potatos can be done for $7/day. Using an utterly  non-optimised solar power source.  (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512)(considering only power)

Baseline oxygen at 50% conversion efficiency from the sabatier process, for free along with your fuel manufacturing efforts is $1.5 (200W average).

A 'nice' diet, with 25% of the calories from pork, and a varied vegetable /potato diet costs around $30/day.

This implies that at least the simplest power costs for food and air are not meaningful, being easily payable on a minimum wage job anywhere in 'the west'.


Title: Re: Power options for a Mars settlement
Post by: AC in NC on 04/21/2018 03:40 pm

At this point long removed from the effort, I won't attest to the whether I did it right and was accurate in calculations.  However, I once was trying to spitball the cost of a massive solar project as a layman's perspective on what we could have alternatively done with certain large government expenses since 2000 in certain troublesome areas.

My recollection is that I validated a variety of numbers from various sources and did a back-of-the-napkin calculation that the entire US annual energy production could be replicated in a square solar-field 30 miles on a side (900 sq mi).  As I recall, this accounted for US Electrity Consumption, then-current Efficiency, reasonable assumption about Solar hours/day and weather, but perhaps not accounting for panel angle-to-the-sun and transmission losses.

The operative point I think being that it easier to do a lot with a little groundspace than you might expect.

As an aside, I think the cost of those 900 sq mi of Solar was significantly higher than the expenditures I was comparing against, but it wasn't ridiculously so and therefore may have been a worthwhile alternative investment particularly given what you get out the back side.
Just to note

That's about 1/2 million acres of land.

What happens when the sun sets?

Cut the starting sunlight by about 1/2 for Mars.

Strange response. :o  Just to reiterate, FWIW it was a back-of-the-napkin analysis for Earth not a PhD Thesis for Mars.
 

OF COURSE, there are additional factors I didn't originally account for and would have to be added for Mars.

Just to note:

Start by cutting the Capacity by 3 Orders of Magnitude IF Mars Electricity Demand is 500 MW-yrs.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/22/2018 08:16 pm
Then no deal. Has to be actual scientific breakeven. Dealing with the Tritium (or helium3) is part of the difficulty, and we’ve been dealing with extrapolations for the last half century. (In fact, breakeven in a narrow sense has been achieved at NIF... the pellet received less energy than it produced via fusion... although that doesn’t include the efficiency of the lasers or all the laser light which missed the pellet.)
That is a bit harsh. D+He3 is less difficult than D+D.  It is not like Tritium, which adds considerable difficulty to the reactor design, because it requires handling the high energy neutrons, plus all the cooling that comes with it.
He3 is just more expensive to buy than Deuterium. As I said, they might do experiments with He3 to destroy the last bits of doubt, but quite frankly, it seems like a waste of money to me to do that until they have completed every last test that they can do with just D+D. That said, their final reactor design would most likely achieve break even with D+D. But that is a bit harder, since from what I understand D+D releases only about 1.5 MeV in charged particles and I do not think that they will bother with a Brayton cycle to convert the rest.
Title: Re: Power options for a Mars settlement
Post by: Patchouli on 04/22/2018 08:28 pm
Early on fission does seem like the best bet but once you get some ISRU infrastructure in place solar starts looking better as you can store energy as methane and lox.

Of course if you can ever get a compact fusion reactor like the one Lockheed wants to build it'll make every other energy source seem quaint.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/22/2018 09:10 pm
Just to repeat the obvious. EM has the biggest battery factory on Earth... and He'll have the first one on Mars! He believes in solar and batteries, and they are available.

EM is massively decreasing the internal (ie for SX itself) cost of launch and transit to Mars.
The only down sides to solar, are the lower sunlight, nights, dust storms and dust. More panels overcome low sunlight, Batteries overcome night, generating electricity from methane and O2 overcome dust storms, and sloped panels with a "jiggler", or "windscreen wiper" overcome dust. Land is free and extensive!
IMO the initial steps will all be based on massive solar, and an overkill of batteries.

I expect Kilopower or similar fission reactors will be NASA's contribution early on, and their route to (limited) participation, without derailing EM's timeline. They will be a great help with ISRU, melting ice, and powering electric mining and construction vehicles, but not critical if not available.
Fusion looks like it could become viable (with HTSC's and +8T field strength), and therefore become an option in at least 10 years.

For mining water, in years to come, mirrors could be used as in the molten salt, solar generation systems, but the heat transfer liquid/system would take the heat directly into the mine. This would be coupled with electricity generation to make use of varied solar input and need. http://www.solarreserve.com/en/technology/molten-salt-energy-storage (http://www.solarreserve.com/en/technology/molten-salt-energy-storage)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/22/2018 09:17 pm
Strange response. :o  Just to reiterate, FWIW it was a back-of-the-napkin analysis for Earth not a PhD Thesis for Mars.
 

OF COURSE, there are additional factors I didn't originally account for and would have to be added for Mars.

Just to note:

Start by cutting the Capacity by 3 Orders of Magnitude IF Mars Electricity Demand is 500 MW-yrs.
Not really. Just my off the top of my head thoughts. TBH Putting the area in perspective. I was staggered how many acres in a square mile.

From a post of mine on page 2 of this thread
Quote
So you're starting at between 493W and 590W according to Colorado U [on the Mars surface]. in 2016 world record (1st solar CdTe) was 22.1%, giving about 108-130W/m^2

A minimal power level is 500Kw/100 people is 4630 m^2 worst case. So 10x that is 46300 m^2, a square about 216m on a side, per 100 people. At 60Kw/person it's 12x those numbers.

TBF it looks like dust does a lot of scattierng but little absorbing and a figure of 50w/m^2 in a dust storm may be reasonable.

So you'd have to double the minimal size (but at 60Kw/ person that's. 12x bigger)

Assuming 60Kw and 50w/m^ minimum even during a major dust storm that's a square of 22.1% efficient thin film about 334m on a side for each batch of 100 settlers. I do think the "waste" heat from such an array would be quite a useful raw materail for various processes, but it's not clear if that's worth the mass

Those settlers are going to be busy. Even if the film is hung on lightweight poles.

Now I wonder how much Cadmium and Tellurium there is on Mars....
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/22/2018 09:21 pm
Then no deal. Has to be actual scientific breakeven. Dealing with the Tritium (or helium3) is part of the difficulty, and we’ve been dealing with extrapolations for the last half century. (In fact, breakeven in a narrow sense has been achieved at NIF... the pellet received less energy than it produced via fusion... although that doesn’t include the efficiency of the lasers or all the laser light which missed the pellet.)
That is a bit harsh. D+He3 is less difficult than D+D.  It is not like Tritium, which adds considerable difficulty to the reactor design, because it requires handling the high energy neutrons, plus all the cooling that comes with it.
He3 is just more expensive to buy than Deuterium. As I said, they might do experiments with He3 to destroy the last bits of doubt, but quite frankly, it seems like a waste of money to me to do that until they have completed every last test that they can do with just D+D. That said, their final reactor design would most likely achieve break even with D+D. But that is a bit harder, since from what I understand D+D releases only about 1.5 MeV in charged particles and I do not think that they will bother with a Brayton cycle to convert the rest.
I'm saying they need to demonstrate scientific breakeven without an asterisk. Just doing D+D without scientific breakeven but with hypothetically "good enough" is not the same.

Scientific breakeven doesn't require converting the fusion energy to electricity. It only requires a fusion power greater than the total input power.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/22/2018 09:28 pm

Baseline calories from potatos can be done for $7/day. Using an utterly  non-optimised solar power source.  (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512)(considering only power)

A 'nice' diet, with 25% of the calories from pork, and a varied vegetable /potato diet costs around $30/day.

This implies that at least the simplest power costs for food and air are not meaningful, being easily payable on a minimum wage job anywhere in 'the west'.
This is OT for this thread but ask yourself seriously.

"Did I just spend half a million dollars to sit in a pressurized trailer and eat potatoes for the rest of my life?"

IOW The dietary options will have expand quite a lot pretty fast. 

And I don't get the prejudice against fish. They were a key part of the Andean Indians ability to grow crops at high altitudes by retaining the heat in the canals between their (relatively) small fields. You can have a wide variety of them and they are relatively easy to carry, as are guinea pigs, rats, rabbits, dogs and cats. All of which have been (are) eaten as food. Of course it might be an idea to bring along some plants to grow the cooking oil of your preference.

NASA estimated with artificial lighting that's 60Kw/person/day. On topic that's a  lot of solar that has to be built and kept on building out if the settlement is continuing to grow.

But that's without ISRU demands, which will be substantial. Inadequate ISRU propellant --> No going home for another 26 months.  :(
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/22/2018 09:41 pm

Baseline calories from potatos can be done for $7/day. Using an utterly  non-optimised solar power source.  (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512)(considering only power)

A 'nice' diet, with 25% of the calories from pork, and a varied vegetable /potato diet costs around $30/day.

This implies that at least the simplest power costs for food and air are not meaningful, being easily payable on a minimum wage job anywhere in 'the west'.

This is OT for this thread but ask yourself seriously.

"Did I just spend half a million dollars to sit in a pressurized trailer and eat potatoes for the rest of my life?"

IOW The dietary options will have expand quite a lot pretty fast. 

And I don't get the prejudice against fish. They were a key part of the Andean Indians ability to grow crops at high altitudes by retaining the heat in the canals between their (relatively) small fields. You can have a wide variety of them and they are relatively easy to carry, as are guinea pigs, rats, rabbits, dogs and cats. All of which have been (are) eaten as food. 

NASA estimated with artificial lighting that's 60Kw/person/day. On topic that's a  lot of solar that has to be built and kept on building out if the settlement is continuing to grow.

But that's without ISRU demands, which will be substantial. Inadequate ISRU propellant --> No going home for another 26 months.  :(
Continued OT...
IMO the farming will be for nutritious flavourful, and interesting additions to the diet... (tomatoes, rocket, basil, herbs) not potatoes. Basic calories will come from Earth for quite a few synods, as space meals, and dried foods like rice, beans, rasins, etc. So we don't have to calculate the Kw to provide 2000 calories per day! If power issues damage food production, the fallback will be rice, tubes of protein, and vitamin tablets! But it will not threaten the settlement.
Edit: a comma ","
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 04/22/2018 09:48 pm

Mars agriculture thread... (https://forum.nasaspaceflight.com/index.php?topic=35877.0)

WRT fish on Mars: tilapia
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/22/2018 11:34 pm
I'm saying they need to demonstrate scientific breakeven without an asterisk. Just doing D+D without scientific breakeven but with hypothetically "good enough" is not the same.

Scientific breakeven doesn't require converting the fusion energy to electricity. It only requires a fusion power greater than the total input power.
Meh, "scientific break even" sometimes also means "extrapolated break even". It is quite commonly done that way because of the difficulty of running experiments on target fuels. This is particularly true for D+T, where the Tritium not only costs a lot of money, but also causes severe engineering challenges that may not be in the (financial) scope of the experiment. Now it can be argued that for D+T, this is cheating because D+T is so much harder to handle from an engineering POV than D+D and a "real" reactor would have to be able to handle that. For D+He3, the opposite is true. The cross section for D+He3 is almost the same as D+D and the expected neutron wall loading from a D+He3 reactor is significantly lower than for D+D. So any reactor that can do D+D can also do D+He3. The potential issue that I see is that doing thousands of shots on D+He3 may be too expensive. But then He3 is not THAT expensive, so maybe they will use it anyway. Either way, I will hold the bet, even if you do not accept "extrapolated break even".
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/23/2018 06:12 am

Baseline calories from potatos can be done for $7/day. Using an utterly  non-optimised solar power source.  (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512)(considering only power)

A 'nice' diet, with 25% of the calories from pork, and a varied vegetable /potato diet costs around $30/day.

This implies that at least the simplest power costs for food and air are not meaningful, being easily payable on a minimum wage job anywhere in 'the west'.
This is OT for this thread but ask yourself seriously.

"Did I just spend half a million dollars to sit in a pressurized trailer and eat potatoes for the rest of my life?"

IOW The dietary options will have expand quite a lot pretty fast. 

The potato figure is mostly useful for a power baseline - setting what amount of electricity is the hard minimum (ish) for required power for food. (3kW)
The 60kW figure mentioned was for a greenhouse using relatively inefficient lighting, in poorly controlled conditions, and counting air conditioning too, as it was in a hot climate.
It is not a useful figure if your cooling is circulation to the outside.

Doubling the $7/day figure doable (with off-the-shelf solar) gets you a varied diet, with assorted veg, and a little meat on sunday. This may not be what the $5M ticket-holders want to eat, but it does equal a reasonable diet for employees.

Other power options - great. But if your power source does not cost under $60/W, landed on Mars, unoptimised solar beats it.

I note that the Hinkley Point power station in the UK is on track to cost $6/W, for a 3.5GW plant - obviously mass unconstrained.
Title: Re: Power options for a Mars settlement
Post by: JamesH65 on 04/23/2018 12:09 pm
Anyone done the numbers?

Assume a 1MW fusion reactor weight in at 200 tonnes (I have no idea), takes two BFS trips. Once down takes a couple of months to install and get going.

How many square KM's of solar plus battery backup is required to do 1MW? Google figures indicate about 1hectare (2.5 acres of panels, no gaps) How many BFS trips does it take, assuming you also need to carry the mounting frames and the batteries for overnight storage. And also take in to account packing density on the BFS.

But, more importantly, HOW LONG does it take to install? Solar farms take months to install on Earth.....
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/23/2018 12:22 pm
Anyone done the numbers?

Assume a 1MW fusion reactor weight in at 200 tonnes (I have no idea), takes two BFS trips. Once down takes a couple of months to install and get going.

How many square KM's of solar plus battery backup is required to do 1MW?

In this thread (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512) I come to the conclusion that 500kW takes 150 tons, without anything special done, for actually off the shelf commercial panels. Two trips gets you 1MW, in a square 200m on a side or so.
Including batteries, for 1MW average.

This is in the range of ten person-days work, if it takes a minute to pick a panel and stand off a cart, place it on the surface, and then move onto the next one, doing a panel a minute.
Considerably faster deployment could be imagined with a more sane solution.

Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/23/2018 12:28 pm
Anyone done the numbers?

Assume a 1MW fusion reactor weight in at 200 tonnes (I have no idea), takes two BFS trips. Once down takes a couple of months to install and get going.

How many square KM's of solar plus battery backup is required to do 1MW? Google figures indicate about 1hectare (2.5 acres of panels, no gaps) How many BFS trips does it take, assuming you also need to carry the mounting frames and the batteries for overnight storage. And also take in to account packing density on the BFS.

But, more importantly, HOW LONG does it take to install? Solar farms take months to install on Earth.....
It will not all be installed in one go. It will develop organically (ha ha) as the settlement grows. By the time fusion is available they will be a vast acreage of solar, and there will be manpower, large earth movers, cranes, loaders etc controlled remotely, autonomously and some with a human driver, so large expansions will not be too challenging.
When eventually available, sure fusion will be a great addition. However on earth that would require a lot of "civil engineering" to prepare: foundations, transmission lines, buildings etc. This is not a little kilopower reactor on a sled!

Apologises for not contributing numbers.... I may have to eventually. The first is fusion on Mars.... light, small, efficient, transportable (in kit form) and erect-able on Mars. Starting point today: The physics at last looks technically just about solved, but a working fusion reactor that provides a net output, and is stable for 10s of seconds has not been achieved. (Experimental) designs for expected success will becoming on line in the coming years.
Ball park guess for fusion on Mars, if EM has some input NET 14 years.
Edit spelling and added a bit.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/23/2018 12:57 pm
Quote from: speedevil
This is in the range of ten person-days work, if it takes a minute to pick a panel and stand off a cart, place it on the surface, and then move onto the next one, doing a panel a minute.

That's a seriously evil speed speedevil! Will you be there with a whip and stopwatch. Do you really think 5 ppl in suits, could get that installed and working in two days work!

Automated deployment, or unrolling long sections by machine may seem faster, but if you include site prep, unloading transport to exact location and grid connections etc there's a lot more to it.

But for manual/robotic piece by piece installation there's no way it will be that fast. First there's site prep, unless you are literally on a really flat gravelly surface. (both easy to drive stakes, and will not be moved in storms.)
Placing stakes and frames... 1. set up vehicle, 2. drive. pick  items, 3. place, 4. secure then come back with another setup to place the panels. Then suited humans to plug in connecting cables.  And the working day will be harder because of suits, harder to move, harder to grasp through thick gloves.... although gravity will make lifting easier. Battery  boxes need some kind of foundation, even if its plastic crates full of gravel! Some cables will have to be buried/covered to allow vehicles to cross....

sure the first ones will probably be just dropped in line, but that's like camping, not even a medium term solution.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/23/2018 02:23 pm
sure the first ones will probably be just dropped in line, but that's like camping, not even a medium term solution.
For the first ones, all you need is a short term solution.
However.
The martian wind tops out at 60mph (https://mars.nasa.gov/news/the-fact-and-fiction-of-martian-dust-storms/) and is about 1% as dense as earth.
This means that you do not need particularly secure mountings, even to cope with storm conditions. 60mph and 1% air pressure is very close to 6MPH winds on earth.
There are no wild animals, and other than meteorites, all that is needed to protect cabling is a fence to stop people wandering into it when drunk.

As an obvious point, the fact that rovers work at all on Mars pretty much means you can drag a cart with 50kg of solar panels.

Think less of rigid arrays of panels bolted to the ground with lots of labour, and more of setting up a very long row of folding card tables, with a string between each.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/24/2018 12:43 am
Anyone done the numbers?

Assume a 1MW fusion reactor weight in at 200 tonnes (I have no idea), takes two BFS trips. Once down takes a couple of months to install and get going.

It depends on the reactor design. Some designs like PPPLs FRC will be 5 meters long and 1.5 meters diameter. The PSS NIAC study for the Pluto orbiter assumes 1 ton for a 5 MW reactor but they still have a way to go until they are ready.
If you look at the SFS Z-Pinch or the DPF, you have about 2 by two by two meters for the core and shielding/FLiBe tank and conversion system. They are between 25 MWe (DPF) and 100 MWe (Z-Pinch).
They still need the pulsed power system and the Z-Pinch needs a Brayeton cycle.
Now going back to my personal safe bet, Helion. Their reactor is roughly the size of a standard shipping container, maybe slightly bigger if you add the power conversion system and the pulsed power system.
I would estimate about 100 tons for a reactor that produces 25 MWe.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 04/24/2018 04:54 am
"Did I just spend half a million dollars to sit in a pressurized trailer and eat potatoes for the rest of my life?"

Hah! We have problems stopping people eating potatoes; especially in the form of crisps/chips and chips/fries! People like potatoes and plenty have some most every day. But, I assume you meant a diet solely of potatoes?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/24/2018 02:42 pm
Hah! We have problems stopping people eating potatoes; especially in the form of crisps/chips and chips/fries! People like potatoes and plenty have some most every day. But, I assume you meant a diet solely of potatoes?
Excellent point.  :)

Consider my objections overcome.  I even see a whole new approach to funding.

"Pringles. Proud sponsors of the Mars Settlement Programme."  :)
"To share, and enjoy." :)
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/24/2018 04:01 pm
For the last few weeks I've been working on a project to simulate the electrical supply and demand for a Martian colony. I'd really appreciate any feedback people have. The simulator can be found here:

https://davedx.github.io/mars-power/ (https://davedx.github.io/mars-power/)

The source code is on Github.

The motivation behind this was to see what impact dust storms have on PV generation and how PV compares to nuclear (the model uses Kilopower modules here), and what kind of battery strategies could be used to try and ensure generation supply meets demand as often as possible even if a dust storm occurs.

Let me know what you think :)

Title: Re: Power options for a Mars settlement
Post by: deruch on 04/28/2018 03:58 am
For the last few weeks I've been working on a project to simulate the electrical supply and demand for a Martian colony. I'd really appreciate any feedback people have. The simulator can be found here:

https://davedx.github.io/mars-power/ (https://davedx.github.io/mars-power/)

The source code is on Github.

The motivation behind this was to see what impact dust storms have on PV generation and how PV compares to nuclear (the model uses Kilopower modules here), and what kind of battery strategies could be used to try and ensure generation supply meets demand as often as possible even if a dust storm occurs.

Let me know what you think :)
Very cool.   8)

I guess in your simulation the crew landed on the shore of a previously unknown Martian lake?    :D 

Sabatier requires water but you only have that and ECLSS in your power consumption budget and no drilling/digging/refining/pumping/etc. for getting the water needed to produce CH4.  Likewise no budget for condensing CO2.  Also, besides chilling out eating potatoes, what are the members of this colony doing while they watch CH4 being produced?  Are they exploring, doing science/research, watching TV, etc?  All of these things will require significant power over and above what your model seems to have budgeted.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/28/2018 09:53 am
For the last few weeks I've been working on a project to simulate the electrical supply and demand for a Martian colony. I'd really appreciate any feedback people have. The simulator can be found here:

https://davedx.github.io/mars-power/ (https://davedx.github.io/mars-power/)

The source code is on Github.

The motivation behind this was to see what impact dust storms have on PV generation and how PV compares to nuclear (the model uses Kilopower modules here), and what kind of battery strategies could be used to try and ensure generation supply meets demand as often as possible even if a dust storm occurs.

Let me know what you think :)
Nice work.

BTW, despite what people claim about thin film solar being light weight and highly volume efficient Tesla Solar does not actually use thin film technology.

It's either single crystal Silicon or "solar tiles" which seem to be glass but I'm not sure what's on the backside as the PV element.

Neither option is AFAIK weight optimized for Mars.

And as was  pointed out in a talk by one of the SX engineers they are looking for something like 500MW for ISRU use at around 500W/m^2 (on Mars surface).
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/28/2018 10:16 am
And as was  pointed out in a talk by one of the SX engineers they are looking for something like 500MW for ISRU use at around 500W/m^2 (on Mars surface).

I think you'll find it's 500kW.

At least near-term.
1000 tons of methane combustion energy is 4*10^7J/kg*10^6 = 4*10^13J.
A year is 3*10^7s, so a megawatt is the right order of magnitude.

With off-the-shelf non thin-film monocrystalline panels, and tesla batteries, you can get 500kW average per BFS cargo mass.

At 50% efficiency doing the proper calculation leads to a couple of BFS per synod refuelling capability per BFS cargo.
In the ebay powering mars thread (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512)

You get three per synod if you can turn off the methane generation during the night.

If you are assuming your BFS are going back, and believe the $130/kg number, actual purchase price of the cells is a non-trivial component - 30%.

If you can make your solar panels twice as light, but they cost over three times as much, this is not a win.
Title: Re: Power options for a Mars settlement
Post by: niwax on 04/28/2018 10:58 am
There is one relaxing factor in the initial ISRU needs: The two initial unmanned Mars missions. If they manage to carry the equipment needed for an ISRU proof of concept filling a single BFS in 2-4 years, any settlers arriving later would always have a way home and most of the fuel will have been produced when the decision is made to send humans. The mission could use enlarged onboard panels to run at a fraction of the rate necessary for regular operation and then be remodeled into a bigger fuel plant when the human workforce arrives with more solar cells.
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/28/2018 03:23 pm
For the last few weeks I've been working on a project to simulate the electrical supply and demand for a Martian colony. I'd really appreciate any feedback people have. The simulator can be found here:

https://davedx.github.io/mars-power/ (https://davedx.github.io/mars-power/)

The source code is on Github.

The motivation behind this was to see what impact dust storms have on PV generation and how PV compares to nuclear (the model uses Kilopower modules here), and what kind of battery strategies could be used to try and ensure generation supply meets demand as often as possible even if a dust storm occurs.

Let me know what you think :)
Very cool.   8)

I guess in your simulation the crew landed on the shore of a previously unknown Martian lake?    :D 

Sabatier requires water but you only have that and ECLSS in your power consumption budget and no drilling/digging/refining/pumping/etc. for getting the water needed to produce CH4.  Likewise no budget for condensing CO2.  Also, besides chilling out eating potatoes, what are the members of this colony doing while they watch CH4 being produced?  Are they exploring, doing science/research, watching TV, etc?  All of these things will require significant power over and above what your model seems to have budgeted.

That's true. It's an ongoing project, if I can get what people think are realistic numbers for activities that are essential like mining water, I can easily add it to the simulation (or if someone makes a pull request that's fine too!).

Has SpaceX talked about how they plan to extract water for the Sabatier process? All I've been able to find is that Elon said they need to find landing sites where there "is water", but not in detail how to extract it (and that autonomously too, given the first mission is unmanned).

Likewise for other human activities, colony building, tunnel boring. If we can calculate realistic numbers then I can add them in.
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/28/2018 03:26 pm
And as was  pointed out in a talk by one of the SX engineers they are looking for something like 500MW for ISRU use at around 500W/m^2 (on Mars surface).

I think you'll find it's 500kW.

At least near-term.
1000 tons of methane combustion energy is 4*10^7J/kg*10^6 = 4*10^13J.
A year is 3*10^7s, so a megawatt is the right order of magnitude.

With off-the-shelf non thin-film monocrystalline panels, and tesla batteries, you can get 500kW average per BFS cargo mass.

At 50% efficiency doing the proper calculation leads to a couple of BFS per synod refuelling capability per BFS cargo.
In the ebay powering mars thread (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512)

You get three per synod if you can turn off the methane generation during the night.

If you are assuming your BFS are going back, and believe the $130/kg number, actual purchase price of the cells is a non-trivial component - 30%.

If you can make your solar panels twice as light, but they cost over three times as much, this is not a win.

That's the point of this software... it goes beyond calculations and simulates other events such as dust storms that affect the variability of PV generation. Maybe 500 kWp just isn't enough.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/28/2018 03:27 pm
That's the point of this software... it goes beyond calculations and simulates other events such as dust storms that affect the variability of PV generation. Maybe 500 kWp just isn't enough.

Maybe it's not.
But it's almost certainly not 500MWp.
(the 500kW was average)
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/28/2018 03:32 pm
Yeah, even with a good, southerly spot with trackers, to get an average 500kW of power on Mars, you're going to need about a nameplate (i.e. Earth-side at noon) capacity of 4 Megawatts. Probably want more than that for margin and so you don't need as big of a battery or electrolysis plant.

Also, pet peave: the Sabatier Reaction doesn't need water, and is technically exothermic so it doesn't need (much) electricity, either. It just needs hydrogen and CO2. It's the production of the hydrogen by electrolysis that requires water and electricity.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/28/2018 04:08 pm
Yeah, even with a good, southerly spot with trackers, to get an average 500kW of power on Mars, you're going to need about a nameplate (i.e. Earth-side at noon) capacity of 4 Megawatts. Probably want more than that for margin and so you don't need as big of a battery or electrolysis plant.
The assumption on the above thread was 200W nameplate on earth = 20Wav on Mars, or pretty much exactly 5MW.
Trackers improve things.

Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/29/2018 02:59 pm
Yeah, even with a good, southerly spot with trackers, to get an average 500kW of power on Mars, you're going to need about a nameplate (i.e. Earth-side at noon) capacity of 4 Megawatts. Probably want more than that for margin and so you don't need as big of a battery or electrolysis plant.

Also, pet peave: the Sabatier Reaction doesn't need water, and is technically exothermic so it doesn't need (much) electricity, either. It just needs hydrogen and CO2. It's the production of the hydrogen by electrolysis that requires water and electricity.

Yep. I read this today, it's a great analysis of the requirements for an ISRU propellant plant: http://www.thespacereview.com/article/3479/1

It also includes an estimate for the power requirements of robotic water/ice mining, including producing purified water that can be used to break into hydrogen for the Sabatier input. Turns out the mining power requirements are quite high too: 7.5-kilowatt-hour to produce 33kg of water.

I've made an issue to add this to the simulator. :)
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/29/2018 04:48 pm
The BFS, at least the crewed one is going to have quite large solar panels on it to provide power during the journey. I wonder if some of these could become the basis for a solar power plant on the martian surface. The 2016 BFS was supposed to carry about 200 kW worth of solar panels. I can't remember what the downsized one was supposed to have. Anyone got numbers for this?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/29/2018 04:59 pm

Yep. I read this today, it's a great analysis of the requirements for an ISRU propellant plant: http://www.thespacereview.com/article/3479/1

It also includes an estimate for the power requirements of robotic water/ice mining, including producing purified water that can be used to break into hydrogen for the Sabatier input. Turns out the mining power requirements are quite high too: 7.5-kilowatt-hour to produce 33kg of water.
Yes. When you look at rigs to drill water wells on Earth I think they tend to run about 30Kw. The power issues is one part the bigger issue is to engineer one that runs unattended. This is a complex task in a hostile environment. Mostly, what do you do if something fails?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/29/2018 05:34 pm
Yeah, even with a good, southerly spot with trackers, to get an average 500kW of power on Mars, you're going to need about a nameplate (i.e. Earth-side at noon) capacity of 4 Megawatts. Probably want more than that for margin and so you don't need as big of a battery or electrolysis plant.

Also, pet peave: the Sabatier Reaction doesn't need water, and is technically exothermic so it doesn't need (much) electricity, either. It just needs hydrogen and CO2. It's the production of the hydrogen by electrolysis that requires water and electricity.

Yep. I read this today, it's a great analysis of the requirements for an ISRU propellant plant: http://www.thespacereview.com/article/3479/1

It also includes an estimate for the power requirements of robotic water/ice mining, including producing purified water that can be used to break into hydrogen for the Sabatier input. Turns out the mining power requirements are quite high too: 7.5-kilowatt-hour to produce 33kg of water.

I've made an issue to add this to the simulator. :)
Im going to have to disagree with your characterization of 7.5kWh to produce 33kg of water being “a lot.” The chemical energy of 1kg Of split water is over 4kWh per SINGLE kilogram of water, assuming perfect efficiency. With realistic efficiency, we’re talking more like 7.5kWh per SINGLE kilogram. So electrolysis still requires about 30 times more energy than mining and purifying the water.

The energy requirements for mining and purifying the water are basically a rounding error.
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 04/29/2018 05:50 pm
Yeah, even with a good, southerly spot with trackers, to get an average 500kW of power on Mars, you're going to need about a nameplate (i.e. Earth-side at noon) capacity of 4 Megawatts. Probably want more than that for margin and so you don't need as big of a battery or electrolysis plant.

Also, pet peave: the Sabatier Reaction doesn't need water, and is technically exothermic so it doesn't need (much) electricity, either. It just needs hydrogen and CO2. It's the production of the hydrogen by electrolysis that requires water and electricity.

Yep. I read this today, it's a great analysis of the requirements for an ISRU propellant plant: http://www.thespacereview.com/article/3479/1

It also includes an estimate for the power requirements of robotic water/ice mining, including producing purified water that can be used to break into hydrogen for the Sabatier input. Turns out the mining power requirements are quite high too: 7.5-kilowatt-hour to produce 33kg of water.

I've made an issue to add this to the simulator. :)
Im going to have to disagree with your characterization of 7.5kWh to produce 33kg of water being “a lot.” The chemical energy of 1kg Of split water is over 4kWh per SINGLE kilogram of water, assuming perfect efficiency. With realistic efficiency, we’re talking more like 7.5kWh per SINGLE kilogram. So electrolysis still requires about 30 times more energy than mining and purifying the water.

The energy requirements for mining and purifying the water are basically a rounding error.

I'm not so sure...

This NASA paper has tons of data about ice mining: https://www.nasa.gov/sites/default/files/atoms/files/mars_ice_drilling_assessment_v6_for_public_release.pdf

They quote 10 kW for 100 gal/day (378 liters), or 30-40 kW for 500 gal/day.

One BFR = 240,000 kg of CH4. The Sabatier process is CO2 + 4H2 -> CH4 + 2H2O.

So you'd need at least 480,000 kg of H2O assuming 100% efficiency and feeding all of the produced water back into the process, if I am calculating this correctly.

500 gal/day = 1892 liters/day = 253 days at 40 kW = 242,880 kWh.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/29/2018 05:58 pm
Please actually convert to per-kilogram numbers or you’ll just confuse yourself.

Using the figure of 30-40kW for a day equaling 500 gallons, still yields .48kWh/kg, still greater a factor of ten different from electrolysis (~7kWh/kg). Still nearly a rounding error.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/29/2018 06:35 pm

SNIP

You get three per synod if you can turn off the methane generation during the night.

SNIP


Electrolysis, not methane generation.  Methane generation can continue as long as there is enough hydrogen left in the buffer.  The hydrogen buffer is there to allow steady state operations, reducing catalyst degradation.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/29/2018 07:21 pm

SNIP

You get three per synod if you can turn off the methane generation during the night.

SNIP


Electrolysis, not methane generation.  Methane generation can continue as long as there is enough hydrogen left in the buffer.  The hydrogen buffer is there to allow steady state operations, reducing catalyst degradation.

The whole process from whatever it takes to gather resources on. If you can modulate down to match insolation, without peak/averages costing you more than 1/3 in terms of mass, means you can mostly skip batteries.

I was being less careful in my wording as I was correcting a three orders of magnitude implication (500MW vs  around 500kW) for near-term power use.
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 04/29/2018 08:19 pm
It may depend on what the ground is like below the surface.  Here in Florida the ground is very sandy, and below that it is limestone.  So the "drilling" rig they use for backyard sprinkling systems (between 30 and 100 feet) basically pumps water down under pressure and sucks it back up again.  There is not a rotating "bit" like they use up in New England that has to bore through granite.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/29/2018 08:48 pm
It may depend on what the ground is like below the surface.  Here in Florida the ground is very sandy, and below that it is limestone.  So the "drilling" rig they use for backyard sprinkling systems (between 30 and 100 feet) basically pumps water down under pressure and sucks it back up again.  There is not a rotating "bit" like they use up in New England that has to bore through granite.
I agree a normal rotating bit may not have much use.
Although a NASA study almost recommends relying on the H2O in Gypsum like rock and regolith etc, as there is not clear evidence of where solid ICE is, and it will be an effort to clear regolith load from above the ice.... I bet EM and SX overcome these issues by more prospecting from orbit, or with an additional lander (which no one has mentioned since Red Dragon was cancelled from 2018). Assumig the SX Mars base 1 has ICE to mine, they can mine it with drilling, heat, or machines. I expect they will use modded versions of "Cat" earth movers, some of which are already available as tele-operated, so adding a little autonomy will not be insurmountable. caterpillar has worked with NASA on off-earth equipment.
Once Kilopower is available, the "waste" heat from the temperature "low point" needed to maintain the heat gradient for the Stirling engines may somehow be directly employed in mining water from ice....
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/29/2018 08:57 pm
This may be difficult in terms of agreements with NASA, even on Mars... But a Kilopower without its Stirling engines, or power generation could use extended heat pipes as a direct water mining tool. Maybe the unit will need too much shielding to make it useable, but conversely secondary heat pipes may possibly be made 10's of metres long to provide heat for mining water at a distance from the reactor itself. This is using the power directly without all that electric mumbo-jumbo....
Mirrors could also be set up to heat a cathode using concentrated sunlight, and a high capacity heat pipe used to transfer this heat energy to mine large quantities of water.
Others have suggested habitats in ice caverns so made.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/29/2018 11:08 pm
This may be difficult in terms of agreements with NASA, even on Mars... But a Kilopower without its Stirling engines, or power generation could use extended heat pipes as a direct water mining tool. Maybe the unit will need too much shielding to make it useable, but conversely secondary heat pipes may possibly be made 10's of metres long to provide heat for mining water at a distance from the reactor itself. This is using the power directly without all that electric mumbo-jumbo....
Mirrors could also be set up to heat a cathode using concentrated sunlight, and a high capacity heat pipe used to transfer this heat energy to mine large quantities of water.
Others have suggested habitats in ice caverns so made.
It would be something of a waste not to produce electricity.  Kilo power is likely no more than ...30% efficient? so it already produces  70% of its output as heat.  And the electricity will be used to light plants, and 95% of that 30% will also turn into heat.  That should also be recoverable to melt ice.



Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/29/2018 11:16 pm
Y’all are still missing the point: energy for mining is tiny compared to the energy needed for electrolyzing that into fuel and oxygen.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/30/2018 08:08 am

SNIP

You get three per synod if you can turn off the methane generation during the night.

SNIP


Electrolysis, not methane generation.  Methane generation can continue as long as there is enough hydrogen left in the buffer.  The hydrogen buffer is there to allow steady state operations, reducing catalyst degradation.

The whole process from whatever it takes to gather resources on. If you can modulate down to match insolation, without peak/averages costing you more than 1/3 in terms of mass, means you can mostly skip batteries.

I was being less careful in my wording as I was correcting a three orders of magnitude implication (500MW vs  around 500kW) for near-term power use.

It's easy to make a minor mistake on a secondary point.  I do it far more often than I'd like.

1/3 of what in terms of mass? 

If I'm doing my math right, we need 77 kg of hydrogen per day to refuel one BFS per synod.  If we can run on battery regulated electrolysis 50% of the day, we need approximately 1 tonne of hydrogen buffer mass.  We'll need the fudge factor to account for maintenance, dust storms, and the like, so 5 tonnes is a more realistic number.  Also needed are the sun shield, waste heat disposal system(potentially heating water prior to electrolysis), and the wiring harnesses needed to connect and power the sensor net and control system.

Hopefully this is enough for speculation purposes.  I'm nowhere near considering mass optimization.  This is an extrapolation from my don't-blow-myself-up proof-of-concept design work.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/30/2018 09:14 am
The whole process from whatever it takes to gather resources on. If you can modulate down to match insolation, without peak/averages costing you more than 1/3 in terms of mass, means you can mostly skip batteries.

I was being less careful in my wording as I was correcting a three orders of magnitude implication (500MW vs  around 500kW) for near-term power use.

It's easy to make a minor mistake on a secondary point.  I do it far more often than I'd like.

1/3 of what in terms of mass? 

Total landed mass.
If your extraction hardware (whatever is the hardest part to scale) weighs more as it has to deal with instantaneous solar power, not average daily power from the solar panels, then batteries plus continual extraction hardware may be lighter.

From the ebay thread, you can fit around 750kW into 150 tons, or 500kW with batteries to smooth it over the whole day.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/30/2018 07:19 pm

SNIP

1/3 of what in terms of mass? 

Total landed mass.
If your extraction hardware (whatever is the hardest part to scale) weighs more as it has to deal with instantaneous solar power, not average daily power from the solar panels, then batteries plus continual extraction hardware may be lighter.

From the ebay thread, you can fit around 750kW into 150 tons, or 500kW with batteries to smooth it over the whole day.

I'm not understanding the logic of using total landing mass.  I'll do a quick estimate even though I don't yet see the point.

We'll use Robobeat's 7.5kWh per kg of water as our placeholder.  Hydrogen is close enough to 1/9th of the total mass of water.  To produce 77 kg of hydrogen per day we will need ~5200kWh.  Assuming our panels are producing at the rated capacity for 12 hours each day, we need 430kW of generation.  Using your 5kW/t figure we need roughly 86t of solar panels.  Since our panels won't be producing at the rated capacity for 12 hours each day we should use the 1t hydrogen buffer mass as our mass to compare.  We're already down to 1/87th of the landed mass and haven't accounted for the Sabatier reactor, electrolysis system, water collection and processing, or the assorted little bits.  I'm not going to estimate the rest of the system mass.  Keeping the buffer under 1/3 of landed mass is no problem.

I would think that a better mass to compare is the mass of batteries needed to run all night.  Using the same basic assumptions we'll need  ~16t of batteries to replace the 1t hydrogen buffer.  We don't need to fiddle with fractions because this is basically a like for like replacement.  The hydrogen buffer is clearly superior to batteries from a landed mass perspective.

The $64B question is, is the hydrogen buffer preferable to replacement catalysts and the tooling to refurbish the Sabatier reactor?  The best answer I can give you at this point is maybe.  In theory the buffer is better mass-wise but we all know what happens to theory once real world testing begins in earnest.  If I can minimize startup degradation so that the reactor can be restarted 100+ times, we can potentially end up with total landed mass savings. 

We might not be looking at actual saving though.  How much landed mass is one person-hour of Martian labor worth?  We are only going to have so many workers on Mars.  It could easily be worthwhile to send an extra tonne so human labor can do other things.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 04/30/2018 08:47 pm
I'm not understanding the logic of using total landing mass.  <snip>

We might not be looking at actual saving though.  How much landed mass is one person-hour of Martian labor worth?  We are only going to have so many workers on Mars.  It could easily be worthwhile to send an extra tonne so human labor can do other things.

I have not carefully read the above post, and need to, but as a more general point, what else would you be optimising for?
Surely the goal is to get capabilities on Mars, and the lighter you can do this (if it does not make it too much more expensive), the more capabilities you can fit in 150 tons. (modulo density limits).

To start with, at least, those initial capabilities would be improvements in landing safety, life support capacity and the capacity to manufacture propellant, and maintenance,but what you want after the next synod is an interesting question.


'What you should optimise for' is a fun question for subsequent synods, at least initially it's fairly simple.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 04/30/2018 09:10 pm
I'm not understanding the logic of using total landing mass.  <snip>

We might not be looking at actual saving though.  How much landed mass is one person-hour of Martian labor worth?  We are only going to have so many workers on Mars.  It could easily be worthwhile to send an extra tonne so human labor can do other things.

I have not carefully read the above post, and need to, but as a more general point, what else would you be optimising for?
Surely the goal is to get capabilities on Mars, and the lighter you can do this (if it does not make it too much more expensive), the more capabilities you can fit in 150 tons. (modulo density limits).

To start with, at least, those initial capabilities would be improvements in landing safety, life support capacity and the capacity to manufacture propellant, and maintenance,but what you want after the next synod is an interesting question.


'What you should optimise for' is a fun question for subsequent synods, at least initially it's fairly simple.
I think one thing to optimise for especially early on is:

  "likely-to-work-out-of-the-box-first-time and continue-reliably-with-no-input-or-servicing and overall-minimal-manpower-input"

 So a battery that just works, period... despite its mass, is better than something else that requires development and tending! Especially as all activity is compromised by power problems. (However even lots of batteries eventually run out so they are only part of a solution)

This as we all frequently repeat is very much one of EM's principals. (The BFS is not optimal mass for every mission... it is optimal amortization of design and manufacturing costs, to reduce individual mission cost, and so increase overall transport capability, (and hasten HSF to Mars) )
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 05/01/2018 03:12 am
I'm not understanding the logic of using total landing mass.  <snip>

We might not be looking at actual saving though.  How much landed mass is one person-hour of Martian labor worth?  We are only going to have so many workers on Mars.  It could easily be worthwhile to send an extra tonne so human labor can do other things.

I have not carefully read the above post, and need to, but as a more general point, what else would you be optimising for?
Surely the goal is to get capabilities on Mars, and the lighter you can do this (if it does not make it too much more expensive), the more capabilities you can fit in 150 tons. (modulo density limits).

To start with, at least, those initial capabilities would be improvements in landing safety, life support capacity and the capacity to manufacture propellant, and maintenance,but what you want after the next synod is an interesting question.


'What you should optimise for' is a fun question for subsequent synods, at least initially it's fairly simple.

I am optimizing for the terrestrial market.  That means low costs, specifically maintenance costs, are critical.  I have to make the money to get to Ceres* somehow and there is free renewable electricity being curtailed.  In some cases, people are even paying others to take electricity away.  This could result in a carbon neutral fracking replacement at a lower price.

My system will eventually be mass optimized.  That comes after proving theory works in practice.  My reaction chamber is currently at least 4 times what it needs to mass for terrestrial use.  The reasoning is that if I find yet another obvious-but-somehow-unpatented way to increase operating pressure without increasing costs I don't have to redesign the entire test rig.  The hydrogen buffer is modular, and since I plan to start testing at 1.5 bar, knowing that its current mass fraction is a fraction of a percent doesn't add anything to this thread. 

What is really important for this thread is a ballpark estimate of the hydrogen buffer mass.  5 tonnes per BFS, plus sun shield and connections, is enough to determine whether a hydrogen buffer or batteries are preferable for continuous operation.  Whether continuous operation is the right choice is a fact I have yet to grok in fullness.

* My goal is to start Ceres Organic Chemicals so I can provide things like fertilizer to the farmers, who are feeding the shovel makers.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 05/01/2018 04:15 am
I'm not understanding the logic of using total landing mass.  <snip>

We might not be looking at actual saving though.  How much landed mass is one person-hour of Martian labor worth?  We are only going to have so many workers on Mars.  It could easily be worthwhile to send an extra tonne so human labor can do other things.

I have not carefully read the above post, and need to, but as a more general point, what else would you be optimising for?
Surely the goal is to get capabilities on Mars, and the lighter you can do this (if it does not make it too much more expensive), the more capabilities you can fit in 150 tons. (modulo density limits).

To start with, at least, those initial capabilities would be improvements in landing safety, life support capacity and the capacity to manufacture propellant, and maintenance,but what you want after the next synod is an interesting question.


'What you should optimise for' is a fun question for subsequent synods, at least initially it's fairly simple.
I think one thing to optimise for especially early on is:

  "likely-to-work-out-of-the-box-first-time and continue-reliably-with-no-input-or-servicing and overall-minimal-manpower-input"

 So a battery that just works, period... despite its mass, is better than something else that requires development and tending! Especially as all activity is compromised by power problems. (However even lots of batteries eventually run out so they are only part of a solution)

This as we all frequently repeat is very much one of EM's principals. (The BFS is not optimal mass for every mission... it is optimal amortization of design and manufacturing costs, to reduce individual mission cost, and so increase overall transport capability, (and hasten HSF to Mars) )

Agree and disagree but we are drifting toward off-topic so I will keep this short.  If we save enough mass using a repairable system that we afford to send two extra people, having a person to repair the system is preferable.

Perhaps a thread discussing the value of human labor on Mars is in order.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 05/01/2018 10:03 am
I am optimizing for the terrestrial market.  That means low costs, specifically maintenance costs, are critical.  I have to make the money to get to Ceres* somehow and there is free renewable electricity being curtailed.  In some cases, people are even paying others to take electricity away.  This could result in a carbon neutral fracking replacement at a lower price.

My system will eventually be mass optimized.
Ah!
That makes sense.
My above posts were in the context of near-term mass trades on how much you can pack onto BFS, trying to base on current commercially available hardware as a realistic floor.

This makes costs to a first degree irrelevant. (for initial missions if they're under $1000/kg or so)
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 05/01/2018 10:45 pm
I am optimizing for the terrestrial market.  That means low costs, specifically maintenance costs, are critical.  I have to make the money to get to Ceres* somehow and there is free renewable electricity being curtailed.  In some cases, people are even paying others to take electricity away.  This could result in a carbon neutral fracking replacement at a lower price.

My system will eventually be mass optimized.
Ah!
That makes sense.
My above posts were in the context of near-term mass trades on how much you can pack onto BFS, trying to base on current commercially available hardware as a realistic floor.

This makes costs to a first degree irrelevant. (for initial missions if they're under $1000/kg or so)

My posts are in the context of near-term mass trades based on the commercially available components I am using to build my prototype.  If the University of Michigan thermal conductive plastic was commercially available then I would have lowered my hydrogen buffer mass estimate by whatever mass savings that material allows.  The same applies for any unobtainium you want to suggest.

I'm not sure how to make this clear without posting the design work I am planning on patenting.  The hydrogen buffer is a subsystem.  The plumbing for the subsystem is designed for the prototype subsystem because hydrogen storage is expensive.  I simply can't give you a good mass fraction because it is other subsystems, and the plumbing that ties them together, that are designed to go from the initial sub-kg/day testing at 1.5 bar to kg/hr tests at 50 bar(currently requires unobtainium).  The entire system is also designed so that any force from explosions is directed away from people and expensive hardware.  It is literally a test rig.  What I can do, and have already done, is to provide a mass estimate for a hydrogen buffer subsystem scaled to 77 kg/day without the excessive shielding.  I could reduce mass by doing things like replacing steel brackets with titanium, but this will push the cost above your $1000/kg or so(What is this based on?) figure.

Because I am designing using modular subsystems it is really easy to make macroeconomic comparisons once we have a buffer mass estimate.  Installing the buffer in an existing Sabatier system design is as simple as cutting the pipe between the electrolysis subsystem and the Sabatier reactor subsystem, then installing a pair of fittings(on the order of a kg or less, so insignificant).  We don't need to know the entire system mass to determine whether a hydrogen buffer makes sense.  All we need to compare are the subsystems that can replace the functionality of the buffer.  What we should be comparing is 1 tonne of hydrogen buffer to 16 tonnes of batteries or ?? tonnes of tooling, spare parts, and mass to support the worker who is refurbishing Sabatier reactors.  These options replace the functionality of the hydrogen buffer.  Knowing the total mass of solar panels needed is irrelevant at this level of detail.

Note: I haven't touched on storage losses.  While storage losses will be far greater using batteries before electrolysis(no need to store the energy lost in electrolysis) than hydrogen buffers, batteries already look bad enough.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/07/2018 03:31 am
Some recent Mars ISRU power and production numbers, in Mars ISRU:  State-of-the-Art and System Level Considerations (http://kiss.caltech.edu/workshops/isru/presentations/Sanders.pdf)

See esp.:  "Mars ISRU Pathfinder Demo Payload Options"

Production:  .48 kg/hr O2 & .12 kg/hr CH4 using 5.75 kW (ISRU power only, excluding other systems)

Application example:  Operating continuously without losses, that ISRU plant would fill one pair of SpaceX ITS tanks, using 41 TJ, over 228 Earth years.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/07/2018 04:41 am
The ISRU pathfinder is not terribly efficient. But right order of magnitude. Gonna need 100 times that amount of power.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/07/2018 11:56 am
The ISRU pathfinder is not terribly efficient.

Which design changes might best improve efficiency, quantitatively?
Title: Re: Power options for a Mars settlement
Post by: AncientU on 05/07/2018 01:07 pm
Some recent Mars ISRU power and production numbers, in Mars ISRU:  State-of-the-Art and System Level Considerations (http://kiss.caltech.edu/workshops/isru/presentations/Sanders.pdf)

See esp.:  "Mars ISRU Pathfinder Demo Payload Options"

Production:  .48 kg/hr O2 & .12 kg/hr CH4 using 5.75 kW (ISRU power only, excluding other systems)

Application example:  Operating continuously without losses, that ISRU plant would fill one pair of SpaceX ITS tanks, using 41 TJ, over 228 Earth years.

What supports this as 'state-of-the-art' except for NASA's PowerPoint title?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/07/2018 01:09 pm
The ISRU pathfinder is not terribly efficient.

Which design changes might best improve efficiency, quantitatively?
Things like propellant production tend to gain efficiency at large scale due to less heat loss.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 05/07/2018 01:58 pm
Application example:  Operating continuously without losses, that ISRU plant would fill one pair of SpaceX ITS tanks, using 41 TJ, over 228 Earth years.
Or with the above mentioned 500kW(av) power supply as fits into one BFS, about 2 years, around a quarter of what I guesstimated using 50% efficiency as implied by SpaceX.
If the equipment weighs 150 tons (including harvesting) that would be a BFS full of fuel per synod, per pair of landed BFSs.

At least it's pretty much the right order of magnitude.
Title: Re: Power options for a Mars settlement
Post by: deruch on 05/08/2018 02:45 pm
Some recent Mars ISRU power and production numbers, in Mars ISRU:  State-of-the-Art and System Level Considerations (http://kiss.caltech.edu/workshops/isru/presentations/Sanders.pdf)

See esp.:  "Mars ISRU Pathfinder Demo Payload Options"

Production:  .48 kg/hr O2 & .12 kg/hr CH4 using 5.75 kW (ISRU power only, excluding other systems)

Application example:  Operating continuously without losses, that ISRU plant would fill one pair of SpaceX ITS tanks, using 41 TJ, over 228 Earth years.

What supports this as 'state-of-the-art' except for NASA's PowerPoint title?

I think the "state of the art" in the title was saying that the presentation was going to give an overview on the state/status/developments of ISRU research.  Not that any particular demonstration/project represented the best currently possible with today's technology.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 08/14/2018 09:42 pm
The ISRU pathfinder is not terribly efficient.

Which design changes might best improve efficiency, quantitatively?
It's true going bigger usually helps but there is also work in the chemical industry on "process intensification" this shrinks process units, usually by things like photo etched metal channels diffusion bonded together, and merging multiple units so (for example) the outflow of one unit is cooled by the inflow of other unit and vice versa, allowing heat to be scavenged  and reused.

I'd suggest the unit NASA has built is more of a Proof of Concept that it can function on Mars, not that it's particularly optimized for making a lot of propellant fast.
Title: Re: Power options for a Mars settlement
Post by: RobLynn on 08/20/2018 12:16 am
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.

Flywheel energy storage makes a lot of sense.  With ultra-high cost and time to ship to Mars long life is critical, and manufacturing cost is unimportant.  A flywheel can last for at least 10's of thousands of full power cycles with high round-trip efficiencies of >90% and very high power levels possible (for things like electric launch catapults) without impacting overall life.

Mars has near-vacuum atmosphere making necessary vacuum casing very thin and light - and can pack dirt around it for RUD safety.  Minimal vacuum pumping is required (and near-infinite life magnetically levitated turbo molecular pump can exhaust straight to atmosphere), and lowered gravity reduces magnetic bearing lift requirements.

7GPa T1100G carbon fibres in unidirectional layup enables almost 2500000m²/s² specific strength = ~300Wh/kg thin-cylindrical flywheels, but more realistically perhaps 150-200Wh/kg, which is pretty competitive with state of the art lithium ion batteries (that can't be cycled too deeply anyway).

Big flywheels have lowered accelerations at rim, and so reduced sensitivity to small defects that might otherwise lead to delaminations or breakages, and less sensitivity to gas friction.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 08/20/2018 07:55 am
How do big flywheels handle planetary rotation? Also you could double the energy density by filling them with batteries.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/20/2018 09:29 am
7GPa T1100G carbon fibres in unidirectional layup enables almost 2500000m²/s² specific strength = ~300Wh/kg thin-cylindrical flywheels, but more realistically perhaps 150-200Wh/kg, which is pretty competitive with state of the art lithium ion batteries (that can't be cycled too deeply anyway).

If you want large reserve capacity, and keep them cool, even current lithium-ion may be good enough.
Reserve capacity of more than a day at 'hotel' loads pretty much inherently means you're cycling the batteries less.
Keeping them cool - 10C - also helps moderately.
Charging the whole thing only to 80% capacity - keeping a reserve which could be charged if an upcoming storm is spotted - helps a lot in terms of life.

In these sorts of conditions - cells that last a decade are not a huge stretch.

To provide 500kW for 8 hours is 'only' 20 tons of lithium-ion, with 100% depth of discharge, or 35 or so with enough reserve to last a decade.

Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/20/2018 09:32 am
How do big flywheels handle planetary rotation? Also you could double the energy density by filling them with batteries.
That doesn't work.
The energy is (if you look at it the right way) stored as the flywheel material being stretched, with a really weird rotary gearbox.
Adding mass to the flywheel reduces energy storage by slowing down the maximum RPM in exact proportion to the proportion of non structural mass added.
In other words, it's no better than a flywheel without the extra mass.
Planetary rotation is almost irrelevant - the rate is low enough that the forces on the bearing are quite small.
The forces are zero if you line up the gyro axis with the planets rotation.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 10:53 am
Steve Hoeser did an interesting writeup on the power budget needed to produce liquid oxygen and methane for the return trip home, looking at a variety of processes and techniques. Whatever the methodology, the energy requirements to produce fuel and oxidizer for BFR are considerable.

Part 1 (http://www.thespacereview.com/article/3479/1)
Part 2 (http://www.thespacereview.com/article/3484/1)
Part 3 (http://www.thespacereview.com/article/3487/1)

The final estimated power requirement is 16 gigawatts to extract, refine, produce, and condense the fuel and oxidizer needed for one BFR return.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/20/2018 10:59 am
The final estimated power requirement is 16 gigawatts to extract, refine, produce, and condense the fuel and oxidizer needed for one BFR return.
Gigawatt-hours. (1.8 megawatts continuous)
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 11:28 am
The final estimated power requirement is 16 gigawatts to extract, refine, produce, and condense the fuel and oxidizer needed for one BFR return.
Gigawatt-hours. (1.8 megawatts continuous)

I figured the "hours" part was implied.  ;) Whether you do it in 26 months or 12, it's still a nice round number to build on. What I'm wondering about at the moment is how one would store the refined product. Liquid methane and oxygen make for somewhat demanding pressure vessels, and the vessels, or components to fabricate them, need to fit inside of BFR(s). In-situ welding would be a tough sell to whoever was responsible for putting those things together.
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 08/20/2018 12:30 pm
Just as one would be jumped on here for confusing "propellant" with "fuel", or "thrust" with "ISP", as a EE I feel compelled to correct misuse of "Watts" when you mean "Watt hours".   They are entirely different things.   Using the traditional water analogy, Watts is flow (how big are my solar panels?  How thick do the wires have to be?) while watt-hours is volume (how big do my batteries have to be?)
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/20/2018 01:34 pm


The final estimated power requirement is 16 gigawatts to extract, refine, produce, and condense the fuel and oxidizer needed for one BFR return.
Gigawatt-hours. (1.8 megawatts continuous)

I figured the "hours" part was implied.  ;) Whether you do it in 26 months or 12, it's still a nice round number to build on. What I'm wondering about at the moment is how one would store the refined product. Liquid methane and oxygen make for somewhat demanding pressure vessels, and the vessels, or components to fabricate them, need to fit inside of BFR(s). In-situ welding would be a tough sell to whoever was responsible for putting those things together.

"hours" implied?   Why not "seconds"?

That's like saying the pressure was a kg.

I get 19000 hours in 26 months so more like 1 MWatt continuous.

Either way it is not as large sounding as "16 GWatts"...



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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: spacenut on 08/20/2018 01:56 pm
RobLynn is right about the flywheel concept.

In the 1970's power plants were thinking of building 300' (100m) diameter flywheels.  They would put them in the ground in case of breaking or destruction.  The wheels would be made from steel cable wire tightly wound.  A vacuum would be pulled on it to reduce air friction.  The idea was to run existing nuclear, hydro, and natural gas power plants at full capacity all the time whenever possible.  Excess power would turn the flywheels.  Then during peek air conditioning times, the flywheels would kick in to carry the extra load.  The flywheels would be placed near these large power plants.  It was estimated to be able to produce 1/3 more power for the grid without new power plants.  The idea was to get rid of the coal plants. 

Now on Mars this sounds like a very good idea coupled with solar, by using simple flywheel power at night.  Martian iron could be made into flywheels without bringing the heavy wire from earth.  Carbon from the atmosphere could be mixed with the iron to make steel wire.  Initially it might be cheaper to bring some wire until forging equipment can be brought from earth.  This would be cheaper than lithium batteries brought from earth.  It might not be as efficient, but it would work. 

In the 1970's flywheels were also considered in cars with an engine/generator combo.  At night you would plug it into your outlet at home, flywheel would spin up to max overnight.  Drive with flywheel produced power during the day.  The idea never really caught on because flywheels were as heavy as a big V8 engine, and the prevailing idea was to make cars lighter and smaller with smaller engines, less raw material. 
Title: Re: Power options for a Mars settlement
Post by: envy887 on 08/20/2018 02:11 pm
For the flywheel concept, UHMWPE fiber is stronger than steel cable and probably easier to make.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 06:31 pm
"hours" implied?   Why not "seconds"?

That's like saying the pressure was a kg.

I get 19000 hours in 26 months so more like 1 MWatt continuous.

Either way it is not as large sounding as "16 GWatts"...

(https://i.imgur.com/mQuMFg4.gif)

If you want it in a year, you need ~2 megawatts continuous. Time is still an independent variable if you want to send any ships back, without passengers, between synods. Whatever the launch interval, there's a need to figure out how to generate 16 Gigawatt Hours for fuel production between each launch from Mars.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/20/2018 06:58 pm
"hours" implied?   Why not "seconds"?

That's like saying the pressure was a kg.

I get 19000 hours in 26 months so more like 1 MWatt continuous.

Either way it is not as large sounding as "16 GWatts"...

(https://i.imgur.com/mQuMFg4.gif)

If you want it in a year, you need ~2 megawatts continuous. Time is still an independent variable if you want to send any ships back, without passengers, between synods. Whatever the launch interval, there's a need to figure out how to generate 16 Gigawatt Hours for fuel production between each launch from Mars.
I was going with 26 month since that's the frequency of launch...  The time that the ship is on the surface should not matter as long as there's enough storage tankage.



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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 07:11 pm
I was going with 26 month since that's the frequency of launch...  The time that the ship is on the surface should not matter as long as there's enough storage tankage.

I suspect storage tank assembly and production on Mars will be somewhat tricky. Metal cryogenic storage vessels need to be rather stout and leak proof. How do you bring tankage to Mars to store the produced fuels long enough for reflight? If there's any significant leak losses over 26 months, the power budget overhead stands to go up considerably.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 08/20/2018 07:13 pm
I was going with 26 month since that's the frequency of launch...  The time that the ship is on the surface should not matter as long as there's enough storage tankage.

I suspect storage tank assembly and production on Mars will be somewhat tricky. Metal cryogenic storage vessels need to be rather stout and leak proof. How do you bring tankage to Mars to store the produced fuels long enough for reflight? If there's any significant leak losses over 26 months, the power budget overhead stands to go up considerably.

Fortunately, if you arrive in a BFS you brought your own storage tanks with you.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 07:18 pm
Fortunately, if you arrive in a BFS you brought your own storage tanks with you.

Is that actually doable? It'll be desirable to keep the skin temperature of BFR above the freezing point of CO2, while the vehicle itself needs to be insulated enough to keep the re-liquification demands of the tanks to a minimum.
Title: Re: Power options for a Mars settlement
Post by: Patchouli on 08/20/2018 07:30 pm
Another thing to keep in mind a BFS should require less propellant to get home than it did to for the outward trip since it would be carrying less payload and you can better make use of aerobraking at Earth.
Fuel consumption on the return leg also can be reduced with a lunar flyby in some scenarios.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 07:36 pm
Another thing to keep in mind a BFS should require less propellant to get home than it did to for the outward trip since it would be carrying less payload and you can better make use of aerobraking at Earth.
Fuel consumption on the return leg also can be reduced with a lunar flyby in some scenarios.

For Mars to Earth downmass below 50 tons, I suppose, but the launch architecture does budget itself with that amount of return mass in mind. They probably want to bring back a lot of samples.  ;D


Title: Re: Power options for a Mars settlement
Post by: envy887 on 08/20/2018 08:39 pm
Fortunately, if you arrive in a BFS you brought your own storage tanks with you.

Is that actually doable? It'll be desirable to keep the skin temperature of BFR above the freezing point of CO2, while the vehicle itself needs to be insulated enough to keep the re-liquification demands of the tanks to a minimum.

It will need insulation anyway, to some extent, for TPS and to avoid ice formation on the launchpad, and to minimize heat transfer into the header tanks during coast and to minimize boiloff while being refueled in LEO. I'd think the additional mass penalty of insulating the main BFS tanks is much lower than that of bringing separate better-insulated tanks all the way form Earth just for that purpose.
Title: Re: Power options for a Mars settlement
Post by: matthewkantar on 08/20/2018 08:43 pm
To put it in familiar terms, the power requirement to refuel a BFS for Mars departure is roughly what would be required to run an average hand heeled hair dryer continuously for two years?
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/20/2018 08:54 pm
To put it in familiar terms, the power requirement to refuel a BFS for Mars departure is roughly what would be required to run an average hand heeled hair dryer continuously for two years?
No.
Two thousand years.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 09:01 pm
Fortunately, if you arrive in a BFS you brought your own storage tanks with you.

Is that actually doable? It'll be desirable to keep the skin temperature of BFR above the freezing point of CO2, while the vehicle itself needs to be insulated enough to keep the re-liquification demands of the tanks to a minimum.

It will need insulation anyway, to some extent, for TPS and to avoid ice formation on the launchpad, and to minimize heat transfer into the header tanks during coast and to minimize boiloff while being refueled in LEO. I'd think the additional mass penalty of insulating the main BFS tanks is much lower than that of bringing separate better-insulated tanks all the way form Earth just for that purpose.

I don't think BFS can afford the mass penalty of being its own vacuum insulated pressure vessel. They probably wouldn't need header tanks if they could.
Title: Re: Power options for a Mars settlement
Post by: mark_m on 08/20/2018 09:55 pm
Another thing to keep in mind a BFS should require less propellant to get home than it did to for the outward trip since it would be carrying less payload and you can better make use of aerobraking at Earth.
Fuel consumption on the return leg also can be reduced with a lunar flyby in some scenarios.
Wouldn't the Mars-to-Earth trip require extra propellant, to account for liftoff from the Mars surface with no refueling in Mars orbit? Or, perhaps more accurately, the same amount of propellant (full tanks), but with a lower payload capacity?
Title: Re: Power options for a Mars settlement
Post by: niwax on 08/20/2018 10:49 pm
Another thing to keep in mind a BFS should require less propellant to get home than it did to for the outward trip since it would be carrying less payload and you can better make use of aerobraking at Earth.
Fuel consumption on the return leg also can be reduced with a lunar flyby in some scenarios.
Wouldn't the Mars-to-Earth trip require extra propellant, to account for liftoff from the Mars surface with no refueling in Mars orbit? Or, perhaps more accurately, the same amount of propellant (full tanks), but with a lower payload capacity?


Mars surface -> LEO transfer happens to be almost identical to Earth surface -> LEO in delta-V. The ability to aerobrake into earth orbit is the only thing that gives you more payload than earth SSTO. So I wouldn't expect to be able to return the full 150t even when fully fueled.
Title: Re: Power options for a Mars settlement
Post by: RobLynn on 08/20/2018 11:08 pm
I get 19000 hours in 26 months so more like 1 MWatt continuous.

How big does that make the necessary PV field? On earth best insolation areas are about 2500kWh/year, on Mars insolation will be about half that. Thin film PV (for easy stowing and lowest weight) peak at about 20% efficiency so maybe can get 200kWh electricity per m² per year on Mars, or something like 20W/m² average.

So need something like 50000m² of thin film solar cells to refuel.  That seems rather unwieldy from a maintenance (and potentially dust cleaning) point of view, and also preventing it from being blown around.

Perhaps nuclear is necessary. 

Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/20/2018 11:25 pm
I get 19000 hours in 26 months so more like 1 MWatt continuous.

How big does that make the necessary PV field? On earth best insolation areas are about 2500kWh/year, on Mars insolation will be about half that. Thin film PV (for easy stowing and lowest weight) peak at about 20% efficiency so maybe can get 200kWh electricity per m² per year on Mars, or something like 20W/m² average.

So need something like 50000m² of thin film solar cells to refuel.  That seems rather unwieldy from a maintenance (and potentially dust cleaning) point of view, and also preventing it from being blown around.

Perhaps nuclear is necessary.

Some effort is spent working through the weight requirements for the ~1 megawatt continuous output needed to operate fueling infrastructure. The solar panels and batteries needed to run the gas processors, fuel reactors, and fuel liquification systems can fit into one BFR, but at the power to weight ratios available to Kilopower, two BFRs would be needed to land enough nuclear power. On the other hand, nuclear power is all but immune to dust storms, although it's likely that fuel operations will shut down during planet wide dust storms anyway to prevent dust from gunking up the CO2 purification system and fractional distillation equipment.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 08/21/2018 12:23 am
Which ever method they choose, I hope they choose two because it appeals to my engineering sense for resilience.
They'll want some form of emergency/backup power there are several possibilities and batteries are the most efficient. 
The mass requirements to haul them from Earth is considerable. 
Why not build Lead-Acid batteries on Mars? 
It's not hi-tech like the Lithium batteries it's easy and well understood and would get the job done.
I've asked this question in other threads... how common is Lead on Mars?  Is it easy to access?
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/21/2018 12:49 am
I get 19000 hours in 26 months so more like 1 MWatt continuous.

How big does that make the necessary PV field? On earth best insolation areas are about 2500kWh/year, on Mars insolation will be about half that. Thin film PV (for easy stowing and lowest weight) peak at about 20% efficiency so maybe can get 200kWh electricity per m² per year on Mars, or something like 20W/m² average.

So need something like 50000m² of thin film solar cells to refuel.  That seems rather unwieldy from a maintenance (and potentially dust cleaning) point of view, and also preventing it from being blown around.

Perhaps nuclear is necessary.

Some effort is spent working through the weight requirements for the ~1 megawatt continuous output needed to operate fueling infrastructure. The solar panels and batteries needed to run the gas processors, fuel reactors, and fuel liquification systems can fit into one BFR, but at the power to weight ratios available to Kilopower, two BFRs would be needed to land enough nuclear power. On the other hand, nuclear power is all but immune to dust storms, although it's likely that fuel operations will shut down during planet wide dust storms anyway to prevent dust from gunking up the CO2 purification system and fractional distillation equipment.
Kilopower is the wrong nuclear design for the job, just like thick glass Si PV panels are, so that's not a fair comparison.

If nuclear is brought in, it should be a high power/mass architecture, designed for Mars conditions, which can perform much better.

However, bootstrapping with Solar seems reasonable.

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/21/2018 12:52 am
If nuclear is brought in, it should be a high power/mass architecture, designed for Mars conditions, which can perform much better.

However, bootstrapping with Solar seems reasonable.

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ABCD: Always Be Counting Down

Kilopower is one of the higher power to mass ratio designs there is, and the Mars optimized designs are heavier than the ones for space probes. Kilopower is a reasonable benchmark for what's achievable with off-world nuclear power, but it would be possible to do better - assuming the Department of Energy gets the green light from Congress to help develop it.
Title: Re: Power options for a Mars settlement
Post by: Patchouli on 08/21/2018 01:13 am

Kilopower is one of the higher power to mass ratio designs there is, and the Mars optimized designs are heavier than the ones for space probes. Kilopower is a reasonable benchmark for what's achievable with off-world nuclear power, but it would be possible to do better - assuming the Department of Energy gets the green light from Congress to help develop it.

A molten salt reactor with a ORC turbine or a VHTR using helium as a coolant can get higher power to weight.
Reactors also tend to benefit from being scaled up so larger ones tend to be more efficient.

If you go solar instead early on I'd recommend at least making the system including propellant storage double sized since some of the methane and lox can be used for energy storage and fueling rovers.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/21/2018 01:30 am

Kilopower is one of the higher power to mass ratio designs there is, and the Mars optimized designs are heavier than the ones for space probes. Kilopower is a reasonable benchmark for what's achievable with off-world nuclear power, but it would be possible to do better - assuming the Department of Energy gets the green light from Congress to help develop it.

A molten salt reactor with a ORC turbine or a VHTR using helium as a coolant can get higher power to weight.
Reactors also tend to benefit from being scaled up so larger ones tend to be more efficient.

If you go solar instead early on I'd recommend at least making the system including propellant storage double sized since some of the methane and lox can be used for energy storage and fueling rovers.

VHTR looks like a very interesting technology. Still, I'd be hesitant, since a leak in the reactor could prove fatal - not because of radiation, but because it's a potential single point of failure for their survival if the depletion of non-replenish-able materials takes the reactor offline.
Title: Re: Power options for a Mars settlement
Post by: Zed_Noir on 08/21/2018 02:42 am

Kilopower is one of the higher power to mass ratio designs there is, and the Mars optimized designs are heavier than the ones for space probes. Kilopower is a reasonable benchmark for what's achievable with off-world nuclear power, but it would be possible to do better - assuming the Department of Energy gets the green light from Congress to help develop it.

A molten salt reactor with a ORC turbine or a VHTR using helium as a coolant can get higher power to weight.
Reactors also tend to benefit from being scaled up so larger ones tend to be more efficient.

If you go solar instead early on I'd recommend at least making the system including propellant storage double sized since some of the methane and lox can be used for energy storage and fueling rovers.

VHTR looks like a very interesting technology. Still, I'd be hesitant, since a leak in the reactor could prove fatal - not because of radiation, but because it's a potential single point of failure for their survival if the depletion of non-replenish-able materials takes the reactor offline.

How much mass does one of these VHTR unit take up? Including all the consumable stuff and reactor support equipment.
Title: Re: Power options for a Mars settlement
Post by: RobLynn on 08/21/2018 03:55 am
Kilopower is the wrong nuclear design for the job, just like thick glass Si PV panels are, so that's not a fair comparison.

If nuclear is brought in, it should be a high power/mass architecture, designed for Mars conditions, which can perform much better.

Supercritical CO2 generator with nuclear would be good, though probably unworkable at less than 100's-1000's kW scale.  If CO2 leaks it is easily replaced, and more efficient than Stirling.  Also exceptionally compact and power dense, so MW scale reactor and generator could probably be transported in one piece. (just add secondary coolant loop/radiator)

Stirling has terrible power to weight ratios - due mostly to the low speed linear alternators used.
Title: Re: Power options for a Mars settlement
Post by: Lar on 08/21/2018 03:36 pm
I think spending a few tonnes on ISRU solar cell making equipment might be good for BFS #3 or #4. That might be a great way to bootstrap.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/21/2018 06:48 pm
I think spending a few tonnes on ISRU solar cell making equipment might be good for BFS #3 or #4. That might be a great way to bootstrap.

For a total mass budget of 600 tons, I don't think you'll be able to squeeze in everything you need for mining, refining, shaping, and stamping the various lithium, cobalt, graphite, manganese, and aluminum needed to produce the batteries. On the other hand, 600 tons of high end lithium ion cells would probably meet all of their energy storage demands and then some for the first several years of the Mars colony's existence.
Title: Re: Power options for a Mars settlement
Post by: Tulse on 08/21/2018 07:01 pm
If you've got the gear to dig out air-tight tunnels, an alternative for power storage might be  compressed gas storage.  It may not be as efficient, but it's much lower tech than having to make your own batteries.
Title: Re: Power options for a Mars settlement
Post by: niwax on 08/21/2018 07:51 pm
If you've got the gear to dig out air-tight tunnels, an alternative for power storage might be  compressed gas storage.  It may not be as efficient, but it's much lower tech than having to make your own batteries.

If you want to concentrate high-tech to as few, light components as possible, something like this might be interesting: https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy/
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 08/21/2018 08:50 pm


The final estimated power requirement is 16 gigawatts to extract, refine, produce, and condense the fuel and oxidizer needed for one BFR return.
Gigawatt-hours. (1.8 megawatts continuous)

I figured the "hours" part was implied.  ;) Whether you do it in 26 months or 12, it's still a nice round number to build on. What I'm wondering about at the moment is how one would store the refined product. Liquid methane and oxygen make for somewhat demanding pressure vessels, and the vessels, or components to fabricate them, need to fit inside of BFR(s). In-situ welding would be a tough sell to whoever was responsible for putting those things together.

"hours" implied?   Why not "seconds"?

That's like saying the pressure was a kg.

I get 19000 hours in 26 months so more like 1 MWatt continuous.

Either way it is not as large sounding as "16 GWatts"...



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ABCD: Always Be Counting Down
Assuming you have 24 long days of course.

And that makes zero allowance for any interruption, IE dust storms.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 08/21/2018 09:11 pm
I would agree solar is the way to go initially.  However, you still have to have batteries or low tech flywheels to store extra solar power for night use.  Then dust storms and cleaning dust off the solar panels will be a maintenance problem.  Lithium batteries are going to eventually wear out. 

Long term power will have to rely on some type of nuclear power for a continuous power supply.  Then you could have solar built on towers to avoid as much surface dust as possible, but still require some type of storage for night use. 

This is one reason I have kind of changed my mind on lithium batteries.  I think low tech ISRU manufactured flywheels might be a cheaper long term solution for peek power storage and usage. 

A huge amount of power is going to be needed long term.  Greenhouses, habitats, electric vehicles for excavation, boring, mining and transportation.  Then laser powered ore melting and smelting after extraction.  I do not thing long term can function with solar/battery system alone. 
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 08/21/2018 09:24 pm
Quote
VHTR looks like a very interesting technology. Still, I'd be hesitant, since a leak in the reactor could prove fatal - not because of radiation, but because it's a potential single point of failure for their survival if the depletion of non-replenish-able materials takes the reactor offline.

How much mass does one of these VHTR unit take up? Including all the consumable stuff and reactor support equipment.
And indeed who is building one?

The first Kilopower unit has already undergone ground test and they are looking to scale up.

It's not a choice between Kilopower and a "better" nuclear system.

It's a choice between Kilopower and nothing.

Anyone looking at nuclear for Mars should consider very carefully the question of enrichment.

On Earth it's a no brainer. No one thinks twice about using LEU rather than natural Uranium.

But on Mars you would have 2 choices.
1) Bring it with you, and buy more on the open (Earth) market and ship it in
2) Set up an enrichment plant on Mars.

With it's weapons applications proliferation of Uranium enrichment technology makes the USG even more twitchy than missile technology. IE very twitchy indeed.

If you're going to develop a new system beyond PWR's (which make great power plants for nuclear submarines but are a pretty poor design otherwise in various ways) avoiding mandatory enrichment, while being able to use enriched fuel if available, would be a pretty good idea.
Title: Re: Power options for a Mars settlement
Post by: Lar on 08/21/2018 09:45 pm
300 tonnes of batteries, 300 tonnes of ISRU cell making equipment. That's my suggestion, or 1/2 that each if possible?
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/21/2018 10:01 pm
I think spending a few tonnes on ISRU solar cell making equipment might be good for BFS #3 or #4. That might be a great way to bootstrap.

One payload of QD solar panels would provide up to 1 GW of PV power (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).  Will any industry need need greater power in the first decade, or even the second?   

re: ISRU solar cells: 

I've seen some UofH manufacturing theory (http://www.niac.usra.edu/files/library/meetings/annual/jun00/433Ignatiev.pdf), and their initial experiments on regolith PV substrate (http://adsbit.harvard.edu//full/2004ESASP.567..173I/0000174.000.html).  They've struggled with manufacture of active materials and contacts, and anti-reflective coating. 

Quote
The regolith reduction and silicon production however, are very energy intensive processes, and there are still too many competing reduction processes to be able to localize to the one or two processes best suited for implementation on the Moon.  As a result, the initial material to be used for solar cell production on the Moon will need to be brought from Earth.

Maybe more suitable material can be found in martian sands. 

But what experiments did you find most promising?

Refs

Ignatiev, A., Freundlich, A., & Horton, C. (2004). Solar Cell Development on the Moon from In-Situ Resources. In Engineering, Construction, and Operations in Challenging Environments: Earth and Space 2004 (pp. 32-36).

Ignatiev, A., Freundlich, A., Duke, M., & Rosenberg, S. (2000). New architecture for space solar power systems: Fabrication of silicon solar cells using in-situ resources. NIAC Phase I Final Report.

Title: Re: Power options for a Mars settlement
Post by: RobLynn on 08/22/2018 12:46 am
...using LEU rather than natural Uranium.

But on Mars you would have 2 choices.
1) Bring it with you, and buy more on the open (Earth) market and ship it in
2) Set up an enrichment plant on Mars.

Nuclear fuel is easily made and transported from earth.  5-10kg of HEU (>95% U235) per MW/year at about $40k per kg fuel is pretty good economics (less than $0.5million per year for 1MW) once a suitable Martian reactor is available.   Submarine reactors operating on HEU can go 15-30 years between refuelling, which seems like a really really useful feature for Mars.  Perhaps something like the 5m³ 10MW thermal Chinese HTR-10 pebble bed that might work with a supercritical CO2 turbine.  High temperature is critical to achieving reasonable efficiency when you don't have an easily accessible cold heat sink like air or water.

While heavy water reactors can make direct use of un-enriched uranium they tend to be pretty enormous with huge inventories of deuterium, and use a lot of natural uranium (as can't extract much energy from it before it is too depleted for further use).
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/22/2018 01:27 am
One payload of QD solar panels would provide up to 1 GW of PV power (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).  Will any industry need need greater power in the first decade, or even the second?   

Yes. One BFR reflight from Mars to Earth needs 16 Gigawatt-hours to return to Earth. Send back ten of them, like the first ships to go to Mars because they represent a capital investment of ~$200 million each, and you'll need to generate 160 Gigawatt-hours over a time span of 26 months to do nothing but refuel the ships in time to depart on the next synod.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 12:48 pm
One payload of QD solar panels would provide up to 1 GW of PV power (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).  Will any industry need need greater power in the first decade, or even the second?   

Yes. One BFR reflight from Mars to Earth needs 16 Gigawatt-hours to return to Earth. Send back ten of them, like the first ships to go to Mars because they represent a capital investment of ~$200 million each, and you'll need to generate 160 Gigawatt-hours over a time span of 26 months to do nothing but refuel the ships in time to depart on the next synod.

160 GWH = 6E14 J.  A 1 GW max PV farm would generate on the order of 1E16 J in that timeframe.

For comparison:  Sizewell B outputs ~ 1 GW.

(http://www.neimagazine.com/uploads/newsarticle/4155083/images/448023/large/4-sizewell%20b-npp.jpg)
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/22/2018 12:48 pm
I think spending a few tonnes on ISRU solar cell making equipment might be good for BFS #3 or #4. That might be a great way to bootstrap.

One payload of QD solar panels would provide up to 1 GW of PV power (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).  Will any industry need need greater power in the first decade, or even the second?   
These are very far from off-the-shelf.
More importantly, you need to consider price.

Once you get over $25/(earth)W, even if your cells weigh nothing, you are better off just loading commercially available cheap panels (as outlined in the 'powering from ebay thread'  into a new-built BFS and not even bothering returning it.

If you are talking of ISRU BFS, where it returns enough to get the price down to the hoped-for $130/kg, that number drops to $2.5/W.
These limiting numbers drop considerably if you send unmodified commercial cells, with no packaging, and make the modules on mars.
Commercial cells are around 700W/kg. Meaning a one-use BFS can carry 100MW of cells, costing around $50M.
Total $200M including the BFS.

If your zero-weight cells are over $2/W, you're not better off.
Reusing the BFS makes that number under $1/W, and makes the dominant cost not the transit to Mars, but the purchase of the cells on earth.
As a corollary, manufacture of solar cells on Mars being economic, if ISRU works means that you are able to produce them more cheaply than on earth. (or have artificial constraints on the supply line limiting the number of BFS you can build)

(100MW peak of cells would work out as 10MW average on Mars, as flat properly oriented fixed panels.)

The latter case - ISRU works, and you're putting together modules on Mars, means you have costs of the order of $10/installed watt of continuous power on Mars.
That is $0.11/kWh or so over 10 years of operation.

This is notably cheaper than my electricity.
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 08/22/2018 12:55 pm
Another use for BFS cargo models that you do not bother to return, besides providing shelter space, or permanent equipment installation, is spare parts.   You could unbolt the engine assembly from the bottom and set them aside for repairs of of the ships.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 03:05 pm
I think spending a few tonnes on ISRU solar cell making equipment might be good for BFS #3 or #4. That might be a great way to bootstrap.

One payload of QD solar panels would provide up to 1 GW of PV power (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).  Will any industry need need greater power in the first decade, or even the second?   
These are very far from off-the-shelf.
More importantly, you need to consider price.

No, QD PV cost is not an issue.  For high-power Mars applications W/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848) is critical, and of course that's where QD PV shines.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/22/2018 03:38 pm
I think spending a few tonnes on ISRU solar cell making equipment might be good for BFS #3 or #4. That might be a great way to bootstrap.

One payload of QD solar panels would provide up to 1 GW of PV power (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).  Will any industry need need greater power in the first decade, or even the second?   
These are very far from off-the-shelf.
More importantly, you need to consider price.

No, QD PV cost is not an issue.  For high-power Mars applications W/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848) is critical, and of course that's where QD PV shines.

Err.
Please read the above post.
PV cost per watt matters, because it is (with BFR cost launch to Mars assuming ISRU ) the dominant cost, even with current commercial cells available in volume.

Unless your QD film is under $2/W or so (earth peak power), for the same total cost assigned to solar, it does not beat commercial cells, as a total installed system, even if you can magically transport it to Mars for free.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 07:38 pm
Unless your QD film is under $2/W or so (earth peak power), for the same total cost assigned to solar, it does not beat commercial cells, as a total installed system, even if you can magically transport it to Mars for free.

Odd hypotheticals.  No, QD mfg aims to cut PV $/W, so QD price isn't an issue.  Explore PV journals (http://www.pvresources.com/en/periodicals/periodicals.php) for trends and developments.

QD rating is presently 15.2 kW/kg.  Such an exceptional rating is important on Mars, as nothing is "magically transported to Mars for free".  One payload of QD PV would outdo five payloads of IMM PV.   You care about relative cost?  Well, that's your first datum.
Title: Re: Power options for a Mars settlement
Post by: RonM on 08/22/2018 07:55 pm
Unless your QD film is under $2/W or so (earth peak power), for the same total cost assigned to solar, it does not beat commercial cells, as a total installed system, even if you can magically transport it to Mars for free.

Odd hypotheticals.  No, QD mfg aims to cut PV $/W, so QD price isn't an issue.  Explore PV journals (http://www.pvresources.com/en/periodicals/periodicals.php) for trends and developments.

QD rating is presently 15.2 kW/kg.  Such an exceptional rating is important on Mars, as nothing is "magically transported to Mars for free".  One payload of QD PV would outdo five payloads of IMM PV.   You care about relative cost?  Well, that's your first datum.

When will these QD panels be ready as off the shelf products? They won't be an option until production units have been thoroughly tested. That might be fine for later settlement phases of Musk's plans, but they won't be ready for early exploration.

Note that something that looks good in the lab doesn't always make it to an industrial product. Many promising technologies end up too expensive to scale up.

BTW, that link was useless. If you want to use a link to support your views, link to a specific article or paper, not some site and suggest we explore for ourselves.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 08:53 pm
That might be fine for later settlement phases of Musk's plans, but they won't be ready for early exploration.

You don't know that.

QD PV is new commercial tech, with much investment, obvious space applications, etc.  Manufacturers are aiming for bulk commercial output in the coming year.  There's no particular reason to think QD PV, or something even better, won't be available for the first cargo flights.

If you want to post on PV tech that may not be "ready for early exploration", you might look into ISRU PV (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1849215#msg1849215).  The very slow progress beyond mere glass mfg is a bit discouraging.  And with GW PV payloads in the offing... why bother?
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/22/2018 09:18 pm
Unless your QD film is under $2/W or so (earth peak power), for the same total cost assigned to solar, it does not beat commercial cells, as a total installed system, even if you can magically transport it to Mars for free.

Odd hypotheticals.  No, QD mfg aims to cut PV $/W, so QD price isn't an issue.  Explore PV journals (http://www.pvresources.com/en/periodicals/periodicals.php) for trends and developments.

QD rating is presently 15.2 kW/kg.  Such an exceptional rating is important on Mars, as nothing is "magically transported to Mars for free".  One payload of QD PV would outdo five payloads of IMM PV.   You care about relative cost?  Well, that's your first datum.

Odd hypotheticals?
That a mars colony would not have infinite money?

You are assuming implicitly that the cost of launch is essentially infinite, compared to the cost of solar cells.
In this case, you want to optimise W/kg at all costs, as it goes directly to reducing launch mass, which saves overall $.

This is however false, in the case of the numbers published by spacex as aims, both for non-reusable BFS (about $1300/kg to Mars, and reusable BFS ($130/kg to Mars), the cost of commercial cells is close to, or significantly above the cost of launching those panels to Mars.

If the $/kg numbers you are working on are $100K/kg, then the optimisation is very different.

If you can save the cost of 5 BFS flights by shrinking the solar panel mass, but your new panels cost so much that they cost more than 5 BFS flights, your nice solar panels have not bought you anything.

I note also https://en.wikipedia.org/wiki/Nanosolar - as one example. A _LOT_ of thin-film solar cell vendors have failed to scale.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 09:53 pm
If you can save the cost of 5 BFS flights by shrinking the solar panel mass, but your new panels cost so much that they cost more than 5 BFS flights, your nice solar panels have not bought you anything.

QD PV uses cheap mfg methods by design:  low temperature, solution processing, etc.  All generally competitive with IMM mfg; hence the QD investment etc.  Your 5x $ hypothetical is inconsistent with the cost-effective character of QD PV business, and curious.  Why do you imagine QD PV to be so expensive?
Title: Re: Power options for a Mars settlement
Post by: whitelancer64 on 08/22/2018 10:10 pm
I think spending a few tonnes on ISRU solar cell making equipment might be good for BFS #3 or #4. That might be a great way to bootstrap.

One payload of QD solar panels would provide up to 1 GW of PV power (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).  Will any industry need need greater power in the first decade, or even the second?   
These are very far from off-the-shelf.
More importantly, you need to consider price.

No, QD PV cost is not an issue.  For high-power Mars applications W/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848) is critical, and of course that's where QD PV shines.

It is an issue. How much does one BFS payload of these solar panels cost?
Title: Re: Power options for a Mars settlement
Post by: whitelancer64 on 08/22/2018 10:21 pm
Perhaps ITS onboard solar arrays are no longer needed on the martian surface, as of 2018.  Quantum dot solar cells presently have an exceptional rating of 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848).  While too fragile for use as ITS solar arrays, they could serve well on the martian surface, e.g., for scaled ISRU.

These are far, far, far too fragile for use on the Martian surface

?  Polyethylene naphthalate is a high-performance material:  a common IC substrate, a tough fiber.  The solar cells are reported having "durable mechanical properties" suitable for use on satellites, for example.  Probably not suitable for the rigors of ITS adventures, but ok in space, generally.

As for Mars, if you eliminate the sand saltation problem by elevating the panels, what's the remaining hazard that renders the panels "far, far, far too fragile" to just... sit there?

Off the top of my head I can think of two, but they are doozies:

Day / night thermal cycles of around 100 C.

UV from the Sun.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/22/2018 10:36 pm
One big advantage of Mars over free space or the Moon is that the thin atmosphere still manages to shield basically all the vacuum UV (ie hard UV, UV shorter than 200nm).

Also, I’d like to see where these portable solar cell makers are that can produce full solar modules straight from ore and can fit in a BFR. I’d like to buy one. I don’t think they exist.
Title: Re: Power options for a Mars settlement
Post by: RonM on 08/22/2018 10:46 pm
That might be fine for later settlement phases of Musk's plans, but they won't be ready for early exploration.

You don't know that.

QD PV is new commercial tech, with much investment, obvious space applications, etc.  Manufacturers are aiming for bulk commercial output in the coming year.  There's no particular reason to think QD PV, or something even better, won't be available for the first cargo flights.

If you want to post on PV tech that may not be "ready for early exploration", you might look into ISRU PV (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1849215#msg1849215).  The very slow progress beyond mere glass mfg is a bit discouraging.  And with GW PV payloads in the offing... why bother?

You need to show recent information on production and cost to support your claim.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 10:58 pm
I’d like to see where these portable solar cell makers are that can produce full solar modules straight from ore and can fit in a BFR. I’d like to buy one. I don’t think they exist.

You might check the relevant references given previously (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1849215#msg1849215) in thread, and see where they lead.

Edit/Lar: No, LMT, you've been warned about this. Provide specific references.

Open Q:  What methods have come to light since 2004, successfully demonstrating practical production and use of active PV material, electrical contacts, or non-reflective coatings from regolith?

I'm not seeing many results in that area, but it's good to explore.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 11:10 pm
That might be fine for later settlement phases of Musk's plans, but they won't be ready for early exploration.

You don't know that.

QD PV is new commercial tech, with much investment, obvious space applications, etc.  Manufacturers are aiming for bulk commercial output in the coming year.  There's no particular reason to think QD PV, or something even better, won't be available for the first cargo flights.

If you want to post on PV tech that may not be "ready for early exploration", you might look into ISRU PV (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1849215#msg1849215).  The very slow progress beyond mere glass mfg is a bit discouraging.  And with GW PV payloads in the offing... why bother?

You need to show recent information on production and cost to support your claim.

Your assertion that "they won't be ready" doesn't square with the QD commercial activity everyone can see.

ISRU PV is very far behind QD PV wrt commercialization, don't you think?
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/22/2018 11:30 pm
Your assertion that "they won't be ready" doesn't square with the QD commercial activity everyone can see.

ISRU PV is very far behind QD PV wrt commercialization, don't you think?

Well, I can't see it. Can you show me what I'm missing with regards to commercialized QD panels?
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/22/2018 11:37 pm
Perhaps ITS onboard solar arrays are no longer needed on the martian surface, as of 2018.  Quantum dot solar cells presently have an exceptional rating of 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848).  While too fragile for use as ITS solar arrays, they could serve well on the martian surface, e.g., for scaled ISRU.

These are far, far, far too fragile for use on the Martian surface

?  Polyethylene naphthalate is a high-performance material:  a common IC substrate, a tough fiber.  The solar cells are reported having "durable mechanical properties" suitable for use on satellites, for example.  Probably not suitable for the rigors of ITS adventures, but ok in space, generally.

As for Mars, if you eliminate the sand saltation problem by elevating the panels, what's the remaining hazard that renders the panels "far, far, far too fragile" to just... sit there?

Off the top of my head I can think of two, but they are doozies:

Day / night thermal cycles of around 100 C.

UV from the Sun.

Both milder on Mars than in space; i.e., the inventors' intended deployment environment (http://pubs.rsc.org/-/content/articlehtml/2018/ee/c7ee02772a).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/22/2018 11:54 pm
Perhaps ITS onboard solar arrays are no longer needed on the martian surface, as of 2018.  Quantum dot solar cells presently have an exceptional rating of 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848).  While too fragile for use as ITS solar arrays, they could serve well on the martian surface, e.g., for scaled ISRU.

These are far, far, far too fragile for use on the Martian surface

?  Polyethylene naphthalate is a high-performance material:  a common IC substrate, a tough fiber.  The solar cells are reported having "durable mechanical properties" suitable for use on satellites, for example.  Probably not suitable for the rigors of ITS adventures, but ok in space, generally.

As for Mars, if you eliminate the sand saltation problem by elevating the panels, what's the remaining hazard that renders the panels "far, far, far too fragile" to just... sit there?

Off the top of my head I can think of two, but they are doozies:

Day / night thermal cycles of around 100 C.

UV from the Sun.

Both milder on Mars than in space; i.e., the inventors' intended deployment environment (http://pubs.rsc.org/-/content/articlehtml/2018/ee/c7ee02772a).

The references you provided are two papers from a single author talking about making QDPV in space.

The wiki entry (https://en.wikipedia.org/wiki/Quantum_dot_solar_cell) doesn't make it sound like they exist in practice in any applicable quantity.

Do you have any reason to believe these issues will be solved in the next 10-20 years?
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/23/2018 12:17 am
Perhaps ITS onboard solar arrays are no longer needed on the martian surface, as of 2018.  Quantum dot solar cells presently have an exceptional rating of 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848).  While too fragile for use as ITS solar arrays, they could serve well on the martian surface, e.g., for scaled ISRU.

These are far, far, far too fragile for use on the Martian surface

?  Polyethylene naphthalate is a high-performance material:  a common IC substrate, a tough fiber.  The solar cells are reported having "durable mechanical properties" suitable for use on satellites, for example.  Probably not suitable for the rigors of ITS adventures, but ok in space, generally.

As for Mars, if you eliminate the sand saltation problem by elevating the panels, what's the remaining hazard that renders the panels "far, far, far too fragile" to just... sit there?

Off the top of my head I can think of two, but they are doozies:

Day / night thermal cycles of around 100 C.

UV from the Sun.

Both milder on Mars than in space; i.e., the inventors' intended deployment environment (http://pubs.rsc.org/-/content/articlehtml/2018/ee/c7ee02772a).

The references you provided are two papers from a single author talking about making QDPV in space.

The wiki entry (https://en.wikipedia.org/wiki/Quantum_dot_solar_cell) doesn't make it sound like they exist in practice in any applicable quantity.

Do you have any reason to believe these issues will be solved in the next 10-20 years?

Why didn't you acknowledge that correction?  Do you think Mars has greater temperature swings and UV flux than space?

--

You've confused the QD references; check again.  Also it's better to note primary literature or at least trade journals (http://www.pvresources.com/en/periodicals/periodicals.php), not Wikipedia, when possible.  As you see, no one has updated the Wiki entry with the results of Zhang et al., first published 12/13/17.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/23/2018 12:34 am
Perhaps ITS onboard solar arrays are no longer needed on the martian surface, as of 2018.  Quantum dot solar cells presently have an exceptional rating of 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848).  While too fragile for use as ITS solar arrays, they could serve well on the martian surface, e.g., for scaled ISRU.

These are far, far, far too fragile for use on the Martian surface

?  Polyethylene naphthalate is a high-performance material:  a common IC substrate, a tough fiber.  The solar cells are reported having "durable mechanical properties" suitable for use on satellites, for example.  Probably not suitable for the rigors of ITS adventures, but ok in space, generally.

As for Mars, if you eliminate the sand saltation problem by elevating the panels, what's the remaining hazard that renders the panels "far, far, far too fragile" to just... sit there?

Off the top of my head I can think of two, but they are doozies:

Day / night thermal cycles of around 100 C.

UV from the Sun.

Both milder on Mars than in space; i.e., the inventors' intended deployment environment (http://pubs.rsc.org/-/content/articlehtml/2018/ee/c7ee02772a).

The references you provided are two papers from a single author talking about making QDPV in space.

The wiki entry (https://en.wikipedia.org/wiki/Quantum_dot_solar_cell) doesn't make it sound like they exist in practice in any applicable quantity.

Do you have any reason to believe these issues will be solved in the next 10-20 years?

Why didn't you acknowledge that correction?  Do you think Mars has greater temperature swings and UV flux than space?

--

You've confused the QD references; check again.  Also it's better to note primary literature or at least trade journals (http://www.pvresources.com/en/periodicals/periodicals.php), not Wikipedia, when possible.  As you see, no one has updated the Wiki entry with the results of Zhang et al., first published 12/13/17.
No intentional omissions...

But you have to admit that "the results of Zhang et al., first published 12/13/17" sounds less production than "the graph of world-wife installed QD-based systems, in MWatt" would.

Or even kWatt.

Also, I see in the article that the aerial efficiency is quite poor.  This matters when you consider the cost of framing, which in modern systems is in line with the cost of the conversion devices.

Low aerial efficiency --> more framing costs, more framing mass, more cleaning costs.

-----
ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: LMT on 08/23/2018 01:22 am
Why didn't you acknowledge that correction?  Do you think Mars has greater temperature swings and UV flux than space?
No intentional omissions...

Your "doozies" are still doozies, or dismissed?

Low aerial efficiency --> more cleaning costs.

"Areal"?

Mars cleans panels gratis (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1828349#msg1828349).
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/23/2018 01:33 am
So are we actually talking about technologies ready for primetime, or promising paper products that no one has a process for producing yet?
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/23/2018 02:12 am
So are we actually talking about technologies ready for primetime, or promising paper products that no one has a process for producing yet?

Anything plausibly available prior to settlement.

Is there a big production issue with, say, PV fabrication on PEN substrate at low temperature?  If not - and to my knowledge there's not - then mass-efficient QD PV is a prime candidate for settlement energy production.

Energy storage is another matter, and obviously more challenging.  Pumped-storage hydroelectricity could scale well for settlement use, if and where feasible.  But OT.

--

Did you agree with my note on the energy requirement for a fleet (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1849366#msg1849366)?  A 1 GW PV farm can launch a great fleet, yes?
Title: Re: Power options for a Mars settlement
Post by: RonM on 08/23/2018 03:07 am
That might be fine for later settlement phases of Musk's plans, but they won't be ready for early exploration.

You don't know that.

QD PV is new commercial tech, with much investment, obvious space applications, etc.  Manufacturers are aiming for bulk commercial output in the coming year.  There's no particular reason to think QD PV, or something even better, won't be available for the first cargo flights.

If you want to post on PV tech that may not be "ready for early exploration", you might look into ISRU PV (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1849215#msg1849215).  The very slow progress beyond mere glass mfg is a bit discouraging.  And with GW PV payloads in the offing... why bother?
You need to show recent information on production and cost to support your claim.
Your assertion that "they won't be ready" doesn't square with the QD commercial activity everyone can see.

If everyone can see it, then why don't you show us? Will there be commercially produced QD panels ready for testing before SpaceX sends its first BFS spacecraft to Mars? Who's making these QD panels? What will they cost?

Look, writing stuff like "activity everyone can see" instead of providing one useful link ruins your credibility.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/23/2018 04:19 am
Why didn't you acknowledge that correction?  Do you think Mars has greater temperature swings and UV flux than space?
No intentional omissions...

Your "doozies" are still doozies, or dismissed?

Low aerial efficiency --> more cleaning costs.

"Areal"?

Mars cleans panels gratis (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1828349#msg1828349).
Areal, yes.  Doozies, I lost you there.

QD cells, I see an experimental technology that offers some advantages and some disadvantages.


-----
ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 08/23/2018 05:38 am
So are we actually talking about technologies ready for primetime, or promising paper products that no one has a process for producing yet?
Good question.

Musk and SX's goal is to land 2 BFS's on Mars from the 2022 launch window. However they have also said they will stay on Mars permanently and it will be the next 2 that need to be refueled for return to Earth. That launch window is 26 months later in 2024

So to be worth considering any technology would have to have production up and running to produce viable quantities in time to deliver to SX to put on board their 2nd Mars expedition.

As a side point systems that don't need concentrators seem a better bet due to all the atmospheric diffusion  caused by dust and there should be a reasonable chance that the process can be migrated to Mars for mfg.

Keep in mind if the cells are made on Earth then every first flight of every BFS  added to the fleet will need to carry it's "refueling block" of cells with it. This would be a reasonable trade for early missions but a Mars mfg facility (even if the processed raw materials comer from Earth) would be a good candidate for early shipment.

I think the PV cell field is extensive enough that there are already plenty of viable candidate technologies outside SCS (although that's what Musk's companies mostly deal with) that one with a fairly low TRL is a poor candidate for being used.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/23/2018 06:26 am
Will there be commercially produced QD panels ready for testing before SpaceX sends its first BFS spacecraft to Mars?

I don't see why not, since "commercial testing" is already underway.  Just to pick examples, Solterra (http://www.solterrasolarcells.com/innovation/automatedproduction.php) has a fully automated production system for PV-tailored QD, dating from 2014 I think.  Substrate and scaling are market-dependent.  Also Nanoshel (https://www.nanoshel.com/sections/pbs-quantum-dots) sells several types of QD and finished QD solar cells.

writing stuff like "activity everyone can see" instead of providing one useful link ruins your credibility.

Everyone can see the commercial activity.  Will you see for yourself?
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/23/2018 06:41 am
if the cells are made on Earth then every first flight of every BFS  added to the fleet will need to carry it's "refueling block" of cells with it. This would be a reasonable trade for early missions but a Mars mfg facility (even if the processed raw materials comer from Earth) would be a good candidate for early shipment.

A factory to manufacture solar cells on Mars, using raw materials from Earth?

How could that improve on a cargo of finished solar panels?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 08/23/2018 07:12 am
A factory to manufacture solar cells on Mars, using raw materials from Earth?

How could that improve on a cargo of finished solar panels?
2 ways.
1)Raw materials can be packed tighter and are more damage resistant. The mass would be the same (although eliminating substantial amounts of packaging could reduce it a bit).

2)In principle a lot of a solar panel could be made fairly simply on Mars. That eliminates a substantial fraction of the mass of a PV panel that has to be brought up Earth's gravity well and landed on Mars.

Looking further ahead you'd want to mfg the active components on Mars as well.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/23/2018 08:18 am
Everyone can see the commercial activity.  Will you see for yourself?

I'm not willing to give you the benefit of the doubt on that without a link that's less than one year old and either offers a commercial product or an estimated time to market that is realistically less than five years away. If it's more than ten years away, it might work, if its five years away, it works but they don't know how to make it. 36 Months away, they're probably at the doorstep of having a product. If it's 18 months away, they're probably commercializing it.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/23/2018 01:40 pm
Will there be commercially produced QD panels ready for testing before SpaceX sends its first BFS spacecraft to Mars?

I don't see why not, since "commercial testing" is already underway.  Just to pick examples, Solterra (http://www.solterrasolarcells.com/innovation/automatedproduction.php) has a fully automated production system for PV-tailored QD, dating from 2014 I think.  Substrate and scaling are market-dependent.  Also Nanoshel (https://www.nanoshel.com/sections/pbs-quantum-dots) sells several types of QD and finished QD solar cells.

writing stuff like "activity everyone can see" instead of providing one useful link ruins your credibility.

Everyone can see the commercial activity.  Will you see for yourself?
You say "everyone", yet you're the only one who's posting about it - hence the "benefit of the doubt" comment above.

----

There is a problem with manufacturing solar panels on Mars - it is an energy intensive process.

On Earth, in large scales, solar panels have become net energy positive many years ago. But small scale production is less energy efficient, mars has half the insolation, and worse of all the energy is needed upfront, so if the energy payback time is maybe 10 years, you're talking about the power production cost of "10 years from now" - now.  That's a problem for a colony that's growing quickly.

This is another reason I think they'll end up with nuclear.



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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: RonM on 08/23/2018 02:07 pm
Will there be commercially produced QD panels ready for testing before SpaceX sends its first BFS spacecraft to Mars?

I don't see why not, since "commercial testing" is already underway.  Just to pick examples, Solterra (http://www.solterrasolarcells.com/innovation/automatedproduction.php) has a fully automated production system for PV-tailored QD, dating from 2014 I think.  Substrate and scaling are market-dependent.  Also Nanoshel (https://www.nanoshel.com/sections/pbs-quantum-dots) sells several types of QD and finished QD solar cells.

writing stuff like "activity everyone can see" instead of providing one useful link ruins your credibility.

Everyone can see the commercial activity.  Will you see for yourself?

I looked at those links and it supports my original statement of "That might be fine for later settlement phases of Musk's plans, but they won't be ready for early exploration." Nanoshel has QD solar cells, but they don't sell completed panels. They are selling components for researchers. Solterra says they're working on it, but don't have any products for sale. To be available for the initial planned SpaceX base and fuel production (2022 or 2024), QD panels need to be an off the shelf product today. They are not. Should be ready for a later settlement phase. It is a promising technology.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 08/23/2018 03:25 pm

Everyone can see the commercial activity.  Will you see for yourself?
I'm an interested person outside the industry- I dont know where to look. Help me out?
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/25/2018 03:02 pm
A factory to manufacture solar cells on Mars, using raw materials from Earth?

How could that improve on a cargo of finished solar panels?
2 ways.
1)Raw materials can be packed tighter and are more damage resistant. The mass would be the same (although eliminating substantial amounts of packaging could reduce it a bit).

2)In principle a lot of a solar panel could be made fairly simply on Mars. That eliminates a substantial fraction of the mass of a PV panel that has to be brought up Earth's gravity well and landed on Mars.

Looking further ahead you'd want to mfg the active components on Mars as well.

re (1.) no, any factory payloads for solar cell mfg and panel assembly would be far too massive to justify without ISRU. 

https://www.youtube.com/watch?v=fZ1SC-vUe_I

re (2.) see recent posts for unaddressed ISRU PV problems, which are very great.  Those aspects of ISRU PV aren't commercial or experimental, but largely theoretical.  NSF posters aren't holding notional ISRU PV tech to the same standards of TRL etc. as existing PV tech.  Why?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/25/2018 03:37 pm
A factory to manufacture solar cells on Mars, using raw materials from Earth?

How could that improve on a cargo of finished solar panels?
2 ways.
1)Raw materials can be packed tighter and are more damage resistant. The mass would be the same (although eliminating substantial amounts of packaging could reduce it a bit).

2)In principle a lot of a solar panel could be made fairly simply on Mars. That eliminates a substantial fraction of the mass of a PV panel that has to be brought up Earth's gravity well and landed on Mars.

Looking further ahead you'd want to mfg the active components on Mars as well.
No. there’s waste in manufacturing solar cells, and the cells themselves are incredibly dense and pack well. So a pallet of cells is a much better option.


Everyone talking about ISRU solar cells is incredibly naive. That requires basically full industry. But just assembling cells into panels and arrays is a lot easier.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/25/2018 03:38 pm
Everyone can see the commercial activity.  Will you see for yourself?

I'm not willing to give you the benefit of the doubt on that without a link that's less than one year old and either offers a commercial product or an estimated time to market that is realistically less than five years away. If it's more than ten years away, it might work, if its five years away, it works but they don't know how to make it. 36 Months away, they're probably at the doorstep of having a product. If it's 18 months away, they're probably commercializing it.

Vague post, and very odd.  You can follow the previous link to order (https://www.nanoshel.com/ordering) QD PV cells, and then wire them up as you like; not five years from now, but today.

And of course many commercial PV processes can be matched to satisfy market need.  No one has opened this particular market yet; i.e., with an RFP for "ultra-lightweight solar panels for Mars settlement:  1+ GW per payload".   :D  Your posts on "benefit of the doubt" and "paper products" are just uninformed.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/25/2018 03:58 pm
Nanoshel has QD solar cells, but they don't sell completed panels.

And it takes how long to wire solar cells into a panel?   :D

When someone puts out an RFP for GW martian panel farms, we'll see how quickly manufacturers fire off B&P.  Meanwhile the many existing and potentially applicable PV mfg processes give options, and reason to think suitable QD panels could be ready, if and when.  No one's even asked yet.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/25/2018 04:37 pm
The original post where quantum dots came up was in response to someone asserting they should use an ISRU plant instead.

Quantum dot solar panels are WAY, WAY closer to reality (in that they're not far from commercial availability, but are quite available for researchers) than a transportable ISRU plant for making solar cells.
Title: Re: Power options for a Mars settlement
Post by: RonM on 08/25/2018 05:20 pm
The original post where quantum dots came up was in response to someone asserting they should use an ISRU plant instead.

Quantum dot solar panels are WAY, WAY closer to reality (in that they're not far from commercial availability, but are quite available for researchers) than a transportable ISRU plant for making solar cells.

I don't think people realize how difficult it will be to setup modern industry on Mars. Building construction materials will be the first objective. The solar panels will have to come from Earth for a long time, but at some point early on the settlement could build the structure to support the panels.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 08/25/2018 09:01 pm
The original post where quantum dots came up was in response to someone asserting they should use an ISRU plant instead.

Quantum dot solar panels are WAY, WAY closer to reality (in that they're not far from commercial availability, but are quite available for researchers) than a transportable ISRU plant for making solar cells.

I don't think people realize how difficult it will be to setup modern industry on Mars. Building construction materials will be the first objective. The solar panels will have to come from Earth for a long time, but at some point early on the settlement could build the structure to support the panels.
Which is good.

The bulk of the mass will be in the structure supporting the cells, either at panel level or support frame level.

I think a lot of that could be made fairly early on, which would be good. 
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/25/2018 09:41 pm
Everyone can see the commercial activity.  Will you see for yourself?

I'm not willing to give you the benefit of the doubt on that without a link that's less than one year old and either offers a commercial product or an estimated time to market that is realistically less than five years away. If it's more than ten years away, it might work, if its five years away, it works but they don't know how to make it. 36 Months away, they're probably at the doorstep of having a product. If it's 18 months away, they're probably commercializing it.

Vague post, and very odd.  You can follow the previous link to order (https://www.nanoshel.com/ordering) QD PV cells, and then wire them up as you like; not five years from now, but today.

And of course many commercial PV processes can be matched to satisfy market need.  No one has opened this particular market yet; i.e., with an RFP for "ultra-lightweight solar panels for Mars settlement:  1+ GW per payload".   :D  Your posts on "benefit of the doubt" and "paper products" are just uninformed.

Since the literature I'm seeing for lead-sulfide solar cells right now is for 9% panels that have complications with temperature dependent behaviors and low voltage, a Mars-ready quantum dot cell still sounds like a paper product.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/25/2018 11:21 pm
A factory to manufacture solar cells on Mars, using raw materials from Earth?

How could that improve on a cargo of finished solar panels?
2 ways.
1)Raw materials can be packed tighter and are more damage resistant. The mass would be the same (although eliminating substantial amounts of packaging could reduce it a bit).

2)In principle a lot of a solar panel could be made fairly simply on Mars. That eliminates a substantial fraction of the mass of a PV panel that has to be brought up Earth's gravity well and landed on Mars.

Looking further ahead you'd want to mfg the active components on Mars as well.
No. there’s waste in manufacturing solar cells, and the cells themselves are incredibly dense and pack well. So a pallet of cells is a much better option.


Everyone talking about ISRU solar cells is incredibly naive. That requires basically full industry. But just assembling cells into panels and arrays is a lot easier.

Never mind the QD cell discussion for a second.

The energy payback time of modern solar panels, on Earth, in very high volume production, is about 1-2 years.

If you half the insolation, and double the energy cost since production volume on Mars will be a small fraction of terrestrial-scale production, then energy payback time becomes 4-8 years.

So if you bring a MWatt of power from Earth, and set it to work making new cells, it will be able to make another MWatt in 4-8 years.  That's pretty dismal and can't support an acceptable growth rate...  Especially since if you keep doing just that - you're making zero usable power....  If you use 50% of your output for real things and 50% for making new cells, then now your "double lifetime" is 8-16 years.



Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/26/2018 12:02 am
The original post where quantum dots came up was in response to someone asserting they should use an ISRU plant instead.

Quantum dot solar panels are WAY, WAY closer to reality (in that they're not far from commercial availability, but are quite available for researchers) than a transportable ISRU plant for making solar cells.

I don't think people realize how difficult it will be to setup modern industry on Mars. Building construction materials will be the first objective. The solar panels will have to come from Earth for a long time, but at some point early on the settlement could build the structure to support the panels.
Which is good.

The bulk of the mass will be in the structure supporting the cells, either at panel level or support frame level.

I think a lot of that could be made fairly early on, which would be good.

The original post (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304) on QD solar panels and their safe martian deployment was my own.  I also noted an ISRU method for panel support (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822354#msg1822354), to enable 1 GW per payload.

Nuclear fuel is easily made and transported from earth.

Why nuclear?  What need would a nuclear plant satisfy at the settlement?


You are kidding, right?  The need is gobs and gobs of power to sustain an industrial base.

The fact that you think you have a different solution does not make the need go away.

PV panels, whether flown from Earth or made locally, have some serious inherent issues.

You talk of GWatts of PV power, (larger than any field built on Earth) in a low-insolation environment and using low-efficiency cells, as if it were the simplest thing in the world.

This is "spec sheet engineering".  You pick out some disjointed benchmark numbers, go from lab to deployment in a couple of years, sprinkle scalability, and voila.

Nuclear power has issues too, but at least that approach is normally treated with more deference to the difficulties.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/26/2018 12:57 am
The original post where quantum dots came up was in response to someone asserting they should use an ISRU plant instead.

Quantum dot solar panels are WAY, WAY closer to reality (in that they're not far from commercial availability, but are quite available for researchers) than a transportable ISRU plant for making solar cells.

I don't think people realize how difficult it will be to setup modern industry on Mars. Building construction materials will be the first objective. The solar panels will have to come from Earth for a long time, but at some point early on the settlement could build the structure to support the panels.
Which is good.

The bulk of the mass will be in the structure supporting the cells, either at panel level or support frame level.

I think a lot of that could be made fairly early on, which would be good.
Yeah, I mean you could simply rest the solar panels on rocks at an angle (on a hill to reduce dust) as a start.

Some stuff wouldn't be TOO hard to make. I actually think a good CNC diamond saw bench may be a very good tool, allowing you to slice up rocks and meteorites into useful shapes without even requiring the energy to melt the material. You could easily produce structural frames for solar panels and other random things in this way. Diamond wire blades also last a long time and are lightweight to replace.

If you found a really big iron-nickel meteorite, you could slice it up in sheets (with a portable x-ray to identify flaws which would need to be avoided or patched), bend them with a press, and weld them into pressure vessels (used for habitat space or ISRU/energy storage). It wouldn't require a bunch of energy to do that, but you could also melt down the large amount of scrap that'd generate into a kind of cast iron-nickel alloy which could then be forged or milled as well.

Or perhaps smaller iron-nickel meteorites could be sliced up and welded into larger sheets in some sort of semi-automatic fashion.

Iron-nickel cable and basalt fiber would also come in handy.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/26/2018 12:59 am
The original post where quantum dots came up was in response to someone asserting they should use an ISRU plant instead.

Quantum dot solar panels are WAY, WAY closer to reality (in that they're not far from commercial availability, but are quite available for researchers) than a transportable ISRU plant for making solar cells.

I don't think people realize how difficult it will be to setup modern industry on Mars. Building construction materials will be the first objective. The solar panels will have to come from Earth for a long time, but at some point early on the settlement could build the structure to support the panels.
Which is good.

The bulk of the mass will be in the structure supporting the cells, either at panel level or support frame level.

I think a lot of that could be made fairly early on, which would be good.

The original post (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304) on QD solar panels and their safe martian deployment was my own.  I also noted an ISRU method for panel support (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822354#msg1822354), to enable 1 GW per payload.

Nuclear fuel is easily made and transported from earth.

Why nuclear?  What need would a nuclear plant satisfy at the settlement?


You are kidding, right?  The need is gobs and gobs of power to sustain an industrial base.

The fact that you think you have a different solution does not make the need go away.

PV panels, whether flown from Earth or made locally, have some serious inherent issues.

You talk of GWatts of PV power, (larger than any field built on Earth) in a low-insolation environment and using low-efficiency cells, as if it were the simplest thing in the world.

This is "spec sheet engineering".  You pick out some disjointed benchmark numbers, go from lab to deployment in a couple of years, sprinkle scalability, and voila.

Nuclear power has issues too, but at least that approach is normally treated with more deference to the difficulties.

You kidding, right? You think that an ISRU plant spitting out solar cells is easier than that?

BTW, there are a few Gigawatt-scale solar farms installed now: https://en.wikipedia.org/wiki/List_of_photovoltaic_power_stations
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/26/2018 01:24 am
A factory to manufacture solar cells on Mars, using raw materials from Earth?

How could that improve on a cargo of finished solar panels?
2 ways.
1)Raw materials can be packed tighter and are more damage resistant. The mass would be the same (although eliminating substantial amounts of packaging could reduce it a bit).

2)In principle a lot of a solar panel could be made fairly simply on Mars. That eliminates a substantial fraction of the mass of a PV panel that has to be brought up Earth's gravity well and landed on Mars.

Looking further ahead you'd want to mfg the active components on Mars as well.
No. there’s waste in manufacturing solar cells, and the cells themselves are incredibly dense and pack well. So a pallet of cells is a much better option.


Everyone talking about ISRU solar cells is incredibly naive. That requires basically full industry. But just assembling cells into panels and arrays is a lot easier.

Never mind the QD cell discussion for a second.

The energy payback time of modern solar panels, on Earth, in very high volume production, is about 1-2 years.

If you half the insolation, and double the energy cost since production volume on Mars will be a small fraction of terrestrial-scale production, then energy payback time becomes 4-8 years.

So if you bring a MWatt of power from Earth, and set it to work making new cells, it will be able to make another MWatt in 4-8 years.  That's pretty dismal and can't support an acceptable growth rate...  Especially since if you keep doing just that - you're making zero usable power....  If you use 50% of your output for real things and 50% for making new cells, then now your "double lifetime" is 8-16 years.
It's lower than 1-2 years now. Just a few months. Additionally, solar panels can last a really long time. Like 40-75 years.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 08/26/2018 01:32 am
I suspect it won't make sense to make solar cells on Mars until the installed solar power exceeds 10 Gigawatts, with additions of at least 1 Gigawatt per year. That's decades in the future, and it will likely include newer tech like quantum dots and/or pervoskite cells (both of which will likely be in large scale commercial use before the first humans land on Mars).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/26/2018 02:24 am
The original post where quantum dots came up was in response to someone asserting they should use an ISRU plant instead.

Quantum dot solar panels are WAY, WAY closer to reality (in that they're not far from commercial availability, but are quite available for researchers) than a transportable ISRU plant for making solar cells.

I don't think people realize how difficult it will be to setup modern industry on Mars. Building construction materials will be the first objective. The solar panels will have to come from Earth for a long time, but at some point early on the settlement could build the structure to support the panels.
Which is good.

The bulk of the mass will be in the structure supporting the cells, either at panel level or support frame level.

I think a lot of that could be made fairly early on, which would be good.

The original post (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304) on QD solar panels and their safe martian deployment was my own.  I also noted an ISRU method for panel support (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822354#msg1822354), to enable 1 GW per payload.

Nuclear fuel is easily made and transported from earth.

Why nuclear?  What need would a nuclear plant satisfy at the settlement?


You are kidding, right?  The need is gobs and gobs of power to sustain an industrial base.

The fact that you think you have a different solution does not make the need go away.

PV panels, whether flown from Earth or made locally, have some serious inherent issues.

You talk of GWatts of PV power, (larger than any field built on Earth) in a low-insolation environment and using low-efficiency cells, as if it were the simplest thing in the world.

This is "spec sheet engineering".  You pick out some disjointed benchmark numbers, go from lab to deployment in a couple of years, sprinkle scalability, and voila.

Nuclear power has issues too, but at least that approach is normally treated with more deference to the difficulties.

You kidding, right? You think that an ISRU plant spitting out solar cells is easier than that?

BTW, there are a few Gigawatt-scale solar farms installed now: https://en.wikipedia.org/wiki/List_of_photovoltaic_power_stations
No - I'm pointing out how ISRU is mathematically problematic for the purpose of making solar cslls.

If you somehow have enough power (earth flown ones, or nuclear) than ISRU for metal/plastic is just crazy hard  (look up energy cost of various materials).

Mars colonization must have a very large power source.

-----
ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/26/2018 02:26 am
A factory to manufacture solar cells on Mars, using raw materials from Earth?

How could that improve on a cargo of finished solar panels?
2 ways.
1)Raw materials can be packed tighter and are more damage resistant. The mass would be the same (although eliminating substantial amounts of packaging could reduce it a bit).

2)In principle a lot of a solar panel could be made fairly simply on Mars. That eliminates a substantial fraction of the mass of a PV panel that has to be brought up Earth's gravity well and landed on Mars.

Looking further ahead you'd want to mfg the active components on Mars as well.
No. there’s waste in manufacturing solar cells, and the cells themselves are incredibly dense and pack well. So a pallet of cells is a much better option.


Everyone talking about ISRU solar cells is incredibly naive. That requires basically full industry. But just assembling cells into panels and arrays is a lot easier.

Never mind the QD cell discussion for a second.

The energy payback time of modern solar panels, on Earth, in very high volume production, is about 1-2 years.

If you half the insolation, and double the energy cost since production volume on Mars will be a small fraction of terrestrial-scale production, then energy payback time becomes 4-8 years.

So if you bring a MWatt of power from Earth, and set it to work making new cells, it will be able to make another MWatt in 4-8 years.  That's pretty dismal and can't support an acceptable growth rate...  Especially since if you keep doing just that - you're making zero usable power....  If you use 50% of your output for real things and 50% for making new cells, then now your "double lifetime" is 8-16 years.
It's lower than 1-2 years now. Just a few months. Additionally, solar panels can last a really long time. Like 40-75 years.
How long they last doesn't help you in this respect.  It only helps, kinda, 20 years after the panel is installed.  If it lasts that long in Martian UV.

GWatt fields on Earth are half GWatt on Mars - that's what I meant.

-----
ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/26/2018 02:27 am
I suspect it won't make sense to make solar cells on Mars until the installed solar power exceeds 10 Gigawatts, with additions of at least 1 Gigawatt per year. That's decades in the future, and it will likely include newer tech like quantum dots and/or pervoskite cells (both of which will likely be in large scale commercial use before the first humans land on Mars).
Ok, once we're at terrestrial scales, I'm in.

This will take a while tho.

-----
ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/26/2018 02:49 am


Maybe they’ll use Kilopower to assist with hab power ....

One advantage of nuclear power is its high certainty of availability. Yes, you can use solar, storage and swtiching things off to cover nighttime and dust storms etc, but there is a certain comfort in having a steady power supply through such vicissitudes! I wouldn't be surprised if there was at least sufficient nuclear power to meet the minimum demands of operating the base/colony, especially life-support.

Actually, initially, Nuclear's biggest problem is availability, since it's a single discrete system that can fail all at once.

You'll need like.4 independent plants before you can blindly rely on it for the survival of the colony.

Solar is naturally a distributed architecture, and fails more gracefully when it does.

I am pretty sure initial power systems will be solar.

-----
ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: LMT on 08/26/2018 02:49 am
it will likely include newer tech like quantum dots and/or pervoskite cells

Unfortunately perovskite solar cells have brutal stability problems which have prevented their use in space, and may preclude use in space.  See the disappointing OSCAR stratospheric test results of Cardinaletti et al. 2018.

Refs.

Cardinaletti, I., Vangerven, T., Nagels, S., Cornelissen, R., Schreurs, D., Hruby, J., ... & Franquet, A. (2018). Organic and perovskite solar cells for space applications. Solar Energy Materials and Solar Cells, 182, 121-127.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/26/2018 03:01 am
You are kidding, right?  The need is gobs and gobs of power to sustain an industrial base.

The fact that you think you have a different solution does not make the need go away.

PV panels, whether flown from Earth or made locally, have some serious inherent issues.

You talk of GWatts of PV power, (larger than any field built on Earth) in a low-insolation environment and using low-efficiency cells, as if it were the simplest thing in the world.

This is "spec sheet engineering".  You pick out some disjointed benchmark numbers, go from lab to deployment in a couple of years, sprinkle scalability, and voila.

Nuclear power has issues too, but at least that approach is normally treated with more deference to the difficulties.

The incredulity isn't substantive, meekGee; just guff.  Replace the incredulous post with something substantive.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 08/26/2018 10:20 am
I think nuclear power needs to exist at least as a backup. When martian dust storms hit, which can take weeks, then you will still need power to at least run the basic necessities. Running the whole station for weeks on batteries sounds unrealistic.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/26/2018 10:30 am
I think nuclear power needs to exist at least as a backup. When martian dust storms hit, which can take weeks, then you will still need power to at least run the basic necessities. Running the whole station for weeks on batteries sounds unrealistic.
A dust storm obscuring 95% of the light still means you get ~5% power.
This may be - if you're doing ISRU - just fine for normal operations other than making fuel.
Especially considering fuel cells (or generators) running from your already generated propellant are an effective backup for very high power demands.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/26/2018 02:29 pm
A dust storm obscuring 95% of the light still means you get ~5% power.

And a GW PV farm weathering the storm with just 1% output still gives 10 MW. 
Title: Re: Power options for a Mars settlement
Post by: RonM on 08/26/2018 03:10 pm
The minimum baseline power requirement will be what is needed to keep the crew alive. Compared to ISRU needs, that baseline will be very low. If there's a concern that 1% to 5% PV output isn't enough, toss in a few Kilopower reactors to play it safe. Then there's no need to use methane from ISRU as a backup. Everything else can fail, but the Kilopower reactors will continue to sizzle.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 08/26/2018 03:56 pm
A mixed architecture would be much more resilient to failure PV, nuclear and batteries.  If there is a system issue with one family of power supply the other would cover the base load plus minimal ISRU power.

At some point the Lithium battery's will need to be replaced, how many cycles are they good for?  Lead-acid battery's are well known and easy to make.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/26/2018 06:08 pm
toss in a few Kilopower reactors to play it safe. Then there's no need to use methane from ISRU as a backup.

No, use methalox as backup, without nuclear reactors.

$.
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/26/2018 06:28 pm
At some point the Lithium battery's will need to be replaced, how many cycles are they good for?  Lead-acid battery's are well known and easy to make.

Methalox tanks are required anyway, and they last indefinitely.  Also if methalox were used only infrequently as emergency power backup, the fuel cells could be few and small, and they'd also last indefinitely.

$.
Title: Re: Power options for a Mars settlement
Post by: matthewkantar on 08/26/2018 06:32 pm
While dust storms were detected on Mars 200 plus years ago, actual weather data only goes back to the mid seventies. What is a hundred year storm on Mars like? A thousand year storm? Planning well means planning for the worst possible luck.

If SpaceX can convince the desk jockeys calling the shots to let them have a nifty little nuke or five, like the proposed Kilopower units, it would be silly to not have them on Mars.

Matthew
Title: Re: Power options for a Mars settlement
Post by: LMT on 08/26/2018 07:18 pm
If SpaceX can convince the desk jockeys calling the shots to let them have a nifty little nuke or five, like the proposed Kilopower units, it would be silly to not have them on Mars.

Kilopower units could have several uses.  Just to pick one:  autonomous mobile night operations, perhaps?

https://youtu.be/XkPKmzFPsho

[h/t link Nomadd]

Conceivably a few Kilopower units could be deployed for such a use.  Then in a time of dire emergency, with loss of e.g. PV, triboelectric and methalox power, those mobile systems could be recalled to the settlement, to plug their Kilopower units into the grid. 

This would be nuclear power at a scale of only some tens of kW, added to the grid only under unlikely emergency conditions.  It's not a case for settlement nuclear investment, but it might be one arguable case for use of nuclear power in the settlement, as it would call for no investment beyond that required already for the purposed mobile systems.
Title: Re: Power options for a Mars settlement
Post by: Patchouli on 08/26/2018 07:21 pm
While dust storms were detected on Mars 200 plus years ago, actual weather data only goes back to the mid seventies. What is a hundred year storm on Mars like? A thousand year storm? Planning well means planning for the worst possible luck.

If SpaceX can convince the desk jockeys calling the shots to let them have a nifty little nuke or five, like the proposed Kilopower units, it would be silly to not have them on Mars.

Matthew

It could make the difference from a dust storm being merely inconvenient or something the forces you to pack up and leave if that's even an option.
Title: Re: Power options for a Mars settlement
Post by: RotoSequence on 08/26/2018 07:27 pm
While dust storms were detected on Mars 200 plus years ago, actual weather data only goes back to the mid seventies. What is a hundred year storm on Mars like? A thousand year storm? Planning well means planning for the worst possible luck.

If SpaceX can convince the desk jockeys calling the shots to let them have a nifty little nuke or five, like the proposed Kilopower units, it would be silly to not have them on Mars.

Matthew

It could make the difference from a dust storm being merely inconvenient or something the forces you to pack up and go home.

When your return ticket is dependent on ISRU, your fuel and oxidizer farms must do their job, or you're not going home.
Title: Re: Power options for a Mars settlement
Post by: RonM on 08/26/2018 07:47 pm
If SpaceX can convince the desk jockeys calling the shots to let them have a nifty little nuke or five, like the proposed Kilopower units, it would be silly to not have them on Mars.

Kilopower units could have several uses.  Just to pick one:  autonomous mobile night operations, perhaps?

Conceivably a few Kilopower units could be deployed for such a use.  Then in a time of dire emergency, with loss of e.g. PV, triboelectric and methalox power, those mobile systems could be recalled to the settlement, to plug their Kilopower units into the grid. 

This would be nuclear power at a scale of only some tens of kW, added to the grid only under unlikely emergency conditions.  It's not a case for settlement nuclear investment, but it might be one arguable case for use of nuclear power in the settlement, as it would call for no investment beyond that required already for the purposed mobile systems.

Good, that's the kind of thinking needed for extreme emergencies. There has to be multiple options to maintain power. Most people on Earth can survive a total power outage, not so much on Mars.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 08/26/2018 07:51 pm
Fuel cells are easy to make and well understood but they are not efficient and you are consuming your fuel not making it.
Having multiple methods to produce power is important, you don't know when one might have a system wide problem. 
Kilopower is a successful proof of concept but it was designed to in more powerful configurations.
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 08/26/2018 09:40 pm
The wind may be blowing at 20 m/s but with an air density only 1% of Earth, you would barely feel it.  (Don't go by the opening scenes in "The Martian".)  The dust getting all over things is the bigger problem.  Various schemes have been discussed to deal with the problem, but in a pinch you send people out with brooms.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 08/26/2018 11:21 pm
A few BFS's could be left in place with their solar panels.  Engines could be removed and stored for any engines damaged upon landing and/or returned to earth on another return flight.  The BFS's could be used for a metholox farm and solar power.  The internal tanks could be used for metholox storage while the outside tanks could be used for habitats or used both sets of tanks for metholox storage.  Then excess metholox could be used for power production in case of other systems failures. 
Title: Re: Power options for a Mars settlement
Post by: speedevil on 08/27/2018 10:12 am
It could make the difference from a dust storm being merely inconvenient or something the forces you to pack up and go home.
When your return ticket is dependent on ISRU, your fuel and oxidizer farms must do their job, or you're not going home.
Removing ISRU from the critical loop takes at most some 6 BFS worth of fuel from Earth, and if you are happy with rendevous in LMO, two. (https://forum.nasaspaceflight.com/index.php?topic=46245)

Removing ISRU from the crew critical path can also be done if you ensure having the ISRU fuel produced before launching crew.



Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 08/27/2018 10:53 am
toss in a few Kilopower reactors to play it safe. Then there's no need to use methane from ISRU as a backup.

No, use methalox as backup, without nuclear reactors.

$.
And when the dust storm hits BEFORE they have had a chance to produce enough Methalox for those fuel cells (or generators)? They still will run out of power. Plus ISRU production will come to a grinding halt (or rather be used up as backup power). Then they could miss their return launch window and might have to stay another 2 years and if they are really unlucky, things might get worse even.
I would feel less worried, if the first crews had an already established return capability of sorts by the time they land (e.g. several tankers were landed first with enough fuel for them to make it back). Things get really hairy if some of the ISRU equipment gets damaged.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 08/27/2018 11:34 am
I thought that this was somewhat fitting for the discussion:
https://www.sciencealert.com/it-s-starting-to-look-like-one-of-our-favourite-mars-rovers-really-is-dead?utm_source=dlvr.it&utm_medium=twitter
Title: Re: Power options for a Mars settlement
Post by: Yaotzin on 08/27/2018 11:39 am
toss in a few Kilopower reactors to play it safe. Then there's no need to use methane from ISRU as a backup.

No, use methalox as backup, without nuclear reactors.

$.
And when the dust storm hits BEFORE they have had a chance to produce enough Methalox for those fuel cells (or generators)? They still will run out of power. Plus ISRU production will come to a grinding halt (or rather be used up as backup power). Then they could miss their return launch window and might have to stay another 2 years and if they are really unlucky, things might get worse even.
I would feel less worried, if the first crews had an already established return capability of sorts by the time they land (e.g. several tankers were landed first with enough fuel for them to make it back). Things get really hairy if some of the ISRU equipment gets damaged.
Solar would be sized to maintain critical life support in the worst storm, no reason not to. Methalox would be backup in case the power system itself goes down. And yes that would mean LOC if both happen together at the start..but that applies to nuclear or whatever too. If everything fails...

I can't see a justification for spending the kind of money that would be required to get them back immediately. We'd be talking hundreds of millions if not billions, just so they don't *maybe* have to stay longer. We're not even talking LOC - and even that would be basically impossible to justify ethically IMO.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 08/27/2018 12:10 pm
Solar would be sized to maintain critical life support in the worst storm, no reason not to. Methalox would be backup in case the power system itself goes down. And yes that would mean LOC if both happen together at the start..but that applies to nuclear or whatever too. If everything fails...

I can't see a justification for spending the kind of money that would be required to get them back immediately. We'd be talking hundreds of millions if not billions, just so they don't *maybe* have to stay longer. We're not even talking LOC - and even that would be basically impossible to justify ethically IMO.
Nuclear would be more reliable, unless we are talking huge solar farms that are way bigger than what is normally needed.

As for bringing the crew back. Unless I miscalculate, this would only take about 2 tankers full of fuel waiting on Mars (assuming 100 tons of fuel per tanker) plus one or maybe two more waiting in mars orbit. I think that all things considered, this would be a small price to pay for extra insurance of the first mission. Subsequent missions would benefit from the ISRU established by the first crew.   
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 08/27/2018 12:26 pm
As for bringing the crew back. Unless I miscalculate, this would only take about 2 tankers full of fuel waiting on Mars (assuming 100 tons of fuel per tanker) plus one or maybe two more waiting in mars orbit. I think that all things considered, this would be a small price to pay for extra insurance of the first mission. Subsequent missions would benefit from the ISRU established by the first crew.

This is something they may do if ISRU production of propellant fails. As a last resort to get the crew back after 4 or 6 years. Not something they will do as a precaution for the first mission.
Title: Re: Power options for a Mars settlement
Post by: Yaotzin on 08/27/2018 01:44 pm
Solar would be sized to maintain critical life support in the worst storm, no reason not to. Methalox would be backup in case the power system itself goes down. And yes that would mean LOC if both happen together at the start..but that applies to nuclear or whatever too. If everything fails...

I can't see a justification for spending the kind of money that would be required to get them back immediately. We'd be talking hundreds of millions if not billions, just so they don't *maybe* have to stay longer. We're not even talking LOC - and even that would be basically impossible to justify ethically IMO.
Nuclear would be more reliable, unless we are talking huge solar farms that are way bigger than what is normally needed.
Nuclear is less reliable on Earth, and it would be a prototype design on Mars for the first time. Compared to routinely used solar, which we've even actually used on Mars. There would be enormous reliability concerns around nuclear for a first mission.

Solar would have to be sized at something like 500kw average, and I can't see life support being more than a single digit percentage of that.

Besides, even the BFS's solar alone will need to be able to keep basic life support up in a storm. It needs to act as an emergency shelter and not immediately die upon landing after all.
Quote
As for bringing the crew back. Unless I miscalculate, this would only take about 2 tankers full of fuel waiting on Mars (assuming 100 tons of fuel per tanker) plus one or maybe two more waiting in mars orbit. I think that all things considered, this would be a small price to pay for extra insurance of the first mission. Subsequent missions would benefit from the ISRU established by the first crew.
Not too familiar with the dv budgets, but isn't Mars->Earth landing very similar to LEO->Mars landing, which takes ~7 tankers? All the calculations seem to assume pretty much filling up the BFS for a return trip. We can skimp on weight of course, but with dry mass 85t:cargo 150t, that would mean 2.5 tankers to return sans humans.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 08/27/2018 05:32 pm
Slide 11:  1 ton/day of ice
This is a nice number to work off of.  40 kg [100 lb] / hr.

So Wooster showed a slide with 40 kg/day ice extraction rate.

balancing the reactant equation:

2(H2O) + CO2 ==>  CH4 + 2(O2)

in terms of mass:

36 + 44 ==> 16 + 64

So 1 ton of water requires 1.2 tons of CO2, and produces 440 kg of methane.

Methane/O2 is 55 MJ/kg, so the energy stored is 24 GJ per day, which is 280 kWatt continuous.

However, this is output.  How much is lost during mining, electrolysis, Sabatier, etc...  That's a big unknown...

Wiki says electrolysis is 75% efficient.

Sabatier produces 165 kJ/mol so (~x30) 5MJ/kg of CO2, or 6 GJ per day...  That's 25% of waste heat. Some of it may be used to help with mining ice for example, but it certainly does not make it into the final product...   So that's another significant loss.  (Maybe some of the heat can help with electrolysis tho, so some of it may be recoverable)

I'd say a estimate of 1 MWatt power input in order achieve 280 kWatt of storage doesn't sound like much at all.


Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 08/27/2018 08:04 pm
Nuclear is less reliable on Earth

Citation please. Nuclear is one of the most reliable power sources that we have.
Compared to routinely used solar, which we've even actually used on Mars. There would be enormous reliability concerns around nuclear for a first mission.
What reliability concerns? Plus, it would be an additional power source.
What we have learned from solar in Mars is that it is not all that reliable. The solar powered Mars rovers are frequently out for months and only survive because of a nuclear powered heating element.

Not too familiar with the dv budgets, but isn't Mars->Earth landing very similar to LEO->Mars landing, which takes ~7 tankers?
Mars escape velocity is ~5 km/s, or about half of Earth. You don't have to bring the tanker with the landing fuel all the way to Mars.

AFAIK, it is 3.8 km/sec to get to Mars orbit. Using the Delta V calculator I get 200 tons of fuel for launch from Mars surface to Mars orbit. That is two tankers full (assuming 100 tons dry weight, 200 tons fuel and an Isp of 375).
A tanker waiting in Mars orbit could have a lot more fuel than a tanker that had to land on Mars.
Have another tanker waiting in LEO with fuel for landing. This would not cost 100s of millions or billions as Yaotzin claimed. It would be a rather marginal cost increase for the first Mars mission.
I assume that the first crewed missions to Mars won't have a full load of passengers. Rather I assume maybe 7 or 8 people total. So the cargo mass should be comparably small. Most of the cargo they take to Mars would probably be expected to stay there for future missions anyway.
In any case, I think that this would be a safety net in order to return a crew if ISRU turns out to be harder than anticipated.
Title: Re: Power options for a Mars settlement
Post by: Lar on 08/29/2018 07:26 pm

So that reads to me like something that will allow a swarm of wireless sensors scattered around the surface to be able to phone in readings once an hour, not something that's going to readily scale up to make enough propellant to get a BFS or three back to Earth every synod.
This is why numbers matter. Once we get the actual numbers, rather than exhortation to "read the link I gave you before" without actually doing the math, turns out this apparently isn't really useful. You will see losses in the cabling that swamp the actual power produced if you try to do anything with it, I expect.
Title: Re: Power options for a Mars settlement
Post by: Llian Rhydderch on 09/02/2018 05:36 am
After the pain of catching up on this thread tonight due to inadequate analysis and excessive armwaving, LMT is just about three posts short of being added to my IGNORE list.  What i usually do to forum posters who consistently fail to modify their behavior to comport with how we roll here, ::) and are being/have been repeatedly asked to mod their behavior by some of our most erudite and capable posters. >:(

Saves a lot of time in my future reading; but I never do it hastily.


I'm fairly confident I am not the only forum reader who has had to resort to a similar heuristic.   8)
Title: Re: Power options for a Mars settlement
Post by: Lar on 09/02/2018 02:35 pm
After the pain of catching up on this thread tonight due to inadequate analysis and excessive armwaving, LMT is just about three posts short of being added to my IGNORE list.  What i usually do to forum posters who consistently fail to modify their behavior to comport with how we roll here, ::) and are being/have been repeatedly asked to mod their behavior by some of our most erudite and capable posters. >:(

Saves a lot of time in my future reading; but I never do it hastily.


I'm fairly confident I am not the only forum reader who has had to resort to a similar heuristic.   8)

Let's not indulge in public appraisals, please. Leave that to the mod team.

But ignore lists are worthwhile things to investigate. As a mod I can't ignore anybody so I know that LMT has a good post once in a while. It would be awesome if they got better at admitting when they were wrong but we have a lot of posters who struggle with that.
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 09/02/2018 03:25 pm
It would be awesome if they got better at admitting when they were wrong but we have a lot of posters who struggle with that.
I do not.

 I've been trying to find a figure for the longest conceivable period a dust storm might shut down fuel production if they go mainly solar to run some possible scenarios, but have mainly managed to confuse myself with the possibilities. The rambling point being, an  emergency evacuation during a long dust storm would be almost impossible for even a very small solar powered settlement if they don't keep a large contingency fuel supply on hand.
 There are just too many assumptions without more data regarding survival mode power usage, Earth located BFRs or whatever ships available for unplanned trips, ability of Mars resident to survive on C-rations, scalability of heatpipe type nukes before you have to go to far more complicated, unreliable pumps, cost of a hundred 10kw Krusty type nukes compared to one big, more conventional reactor and all that. Cherry picking possible scenarios to support my case is pretty useless without a little more hard data.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 09/02/2018 03:59 pm
A small side note.

IIRC Bechtel was one of the key companies for the mfg of the reactor on the NSS Savannah.

That's important because there are very few non naval nuclear reactors that are conveniently sized for supporting Mars surface operations.  Any design of naval reactor is problematical due to its operating characteristics being potentially useful for anti submarine warfare purposes.

converting a sea going nuke to Mars use could involve removing stuff, such as reduction gear to drive a propeller, rather than a generator. Likewise the "waste" heat should have a number of uses in either settlement heating or accelerating various chemical processes.

While such a reactor is very unlikely to be "optimal" for Mars it would fit with SX's approach of getting something working and gradually adapting it to the environment.

The downside is it's in the 50-60 tonne range. So do you have one on each BFS, or just take one?
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 09/02/2018 05:53 pm
Since heat is so important for a mars base, what are people's thoughts on the various "heat battery" technoligies? (wiki: https://en.wikipedia.org/wiki/Thermal_Battery)

A RTG may only be some weak % efficent for electricity, and Sabatier being exothermic, there's plenty of heat sources, but they are inconviently complicated and generally assumed to be immobile, making them poorly suited for, say, dumping into an ice deposit for thermal mining.

Thermal storage would allow for coolant "Heat-ant" loops farther away from the heat source.
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 09/05/2018 07:21 am
Maybe this has been posted before. It's a pretty nice Idaho National Labs rundown of various reactor types and classes with a focus on a 2MW heat pipe model they're working on.
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2017/power/Ananth19349.pdf
Title: Re: Power options for a Mars settlement
Post by: aero on 10/07/2018 06:27 pm
What is the outlook for stored hydro on Mars? I envision an insulated reservoir at the top of a cliff or up a mountainside, coupled with another insulated reservoir at the bottom of the cliff via a hydroelectric generator with solar power used to pump the water back to the upper reservoir.

This approach requires enough water and iron or steel pipe as well as the pump and hydroelectric generator. It is interesting because pumps are very energy efficient and so are hydroelectric generators. Some Manufacturers claim electrical-in/water head power out efficiency of greater than 90% although testing found less, with measured efficiency between 85% to 90%. Compare this to the efficiency of other energy storage systems. As for converting stored hydro back into electrical power, hydroelectric generators are also about 90% efficient.

http://hydratek.com/wp-content/uploads/2015/04/Pump-Energy-Efficiency-Field-Testing-and-Benchmarking-in-Canada-Papa-et-al-2014.pdf (http://hydratek.com/wp-content/uploads/2015/04/Pump-Energy-Efficiency-Field-Testing-and-Benchmarking-in-Canada-Papa-et-al-2014.pdf)
https://www.mpoweruk.com/hydro_power.htm (https://www.mpoweruk.com/hydro_power.htm)

The above indicates the round trip efficiency of stored hydro is about 80% from start, solar power to pump water up from the lower reservoir to night time generation of electricity for consumption. The big remaining problem is finding enough water to fill the lower reservoir in the first place but water will be a, if not the key resource on Mars as it is required for the production of methane  and LOX.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/07/2018 06:46 pm
What is the outlook for stored hydro on Mars? I envision an insulated reservoir at the top of a cliff or up a mountainside, coupled with another insulated reservoir at the bottom of the cliff via a hydroelectric generator with solar power used to pump the water back to the upper reservoir.
Pretty terrible.
Fifty meters, times a thousand tons = m*g*h = joules.
Or, in numbers, 50m*3.5m/s^2*1000000kg = 175MJ, or 48kWh.

This is about the equivalent of burning twenty kilos of methalox, or about the same power stored in a 250kg battery.
Title: Re: Power options for a Mars settlement
Post by: aero on 10/07/2018 10:56 pm
What is the outlook for stored hydro on Mars? I envision an insulated reservoir at the top of a cliff or up a mountainside, coupled with another insulated reservoir at the bottom of the cliff via a hydroelectric generator with solar power used to pump the water back to the upper reservoir.
Pretty terrible.
Fifty meters, times a thousand tons = m*g*h = joules.
Or, in numbers, 50m*3.5m/s^2*1000000kg = 175MJ, or 48kWh.

This is about the equivalent of burning twenty kilos of methalox, or about the same power stored in a 250kg battery.

Your numbers are correct, but why such a small reservoir? It is true that the reservoir volume can be increased as energy storage need increases, but I don't see any reason to start with a 10x10x10 meter reservoir. Maybe 100x100x10 meter reservoirs. That would store 4800 kWh which would last overnight if the drain was no greater than 300 kW per hour, or for a week at a drain of 28 kW per hour.

But I just checked and found that my memory had failed me again. Li-ion battery charging is very efficient, like 99% efficient, so there is very little loss using Li-ion batteries for storage. It looks like the only real loss is the handy fish ponds the reservoirs would be.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/07/2018 11:03 pm
What is the outlook for stored hydro on Mars? I envision an insulated reservoir at the top of a cliff or up a mountainside, coupled with another insulated reservoir at the bottom of the cliff via a hydroelectric generator with solar power used to pump the water back to the upper reservoir.
Pretty terrible.
Fifty meters, times a thousand tons = m*g*h = joules.
Or, in numbers, 50m*3.5m/s^2*1000000kg = 175MJ, or 48kWh.

This is about the equivalent of burning twenty kilos of methalox, or about the same power stored in a 250kg battery.

Your numbers are correct, but why such a small reservoir? It is true that the reservoir volume can be increased as energy storage need increases, but I don't see any reason to start with a 10x10x10 meter reservoir. Maybe 100x100x10 meter reservoirs. That would store 4800 kWh which would last overnight if the drain was no greater than 300 kW per hour, or for a week at a drain of 28 kW per hour.

Water is going to be a limiting resource for some time.
Assuming you're going to be able to find 100000 tons may be optimistic.
Plus, you have to add onto the fixed costs of mass launched to mars, the amount needed to seal the reservoir and keep them liquid.
In principle, solid storage - with trains or similar up an incline is possible. But it is hard to make the initial mass competitive with batteries or others.
Title: Re: Power options for a Mars settlement
Post by: KelvinZero on 10/07/2018 11:11 pm
What is the outlook for stored hydro on Mars? I envision an insulated reservoir at the top of a cliff or up a mountainside, coupled with another insulated reservoir at the bottom of the cliff via a hydroelectric generator with solar power used to pump the water back to the upper reservoir.
Pretty terrible.
Fifty meters, times a thousand tons = m*g*h = joules.
Or, in numbers, 50m*3.5m/s^2*1000000kg = 175MJ, or 48kWh.

This is about the equivalent of burning twenty kilos of methalox, or about the same power stored in a 250kg battery.
Not so good for mars but an exciting option for earth IMO. Vast energy storage is the big issue in moving to alternative energy. All this doom and gloom about climate change and water shortages but maybe we should be thinking about creating new inland shorefront property in places that used to be just deserts. I think there was actually some nutty plan to do that in Australia before climate change even became an issue.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 10/08/2018 12:52 am
Pumped hydro on Mars only works for large altitude gradients. Would work well at Mellas Chasma. Heck, doesn't even need to be water. Could be weights on cables. Heck, you could produce energy by shoveling dirt at high altitude and dumping it at low altitude.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/08/2018 01:26 am
Pumped hydro on Mars only works for large altitude gradients. Would work well at Mellas Chasma. Heck, doesn't even need to be water. Could be weights on cables. Heck, you could produce energy by shoveling dirt at high altitude and dumping it at low altitude.

This is interesting in the longer term, when you can make steel locally, since all it really requires is making dumb RR steel.

Lay down a track down a long incline (Mars has them) and use electric dirt-mover engines driving up and down - braking (and charging) on the way down when full of dirt, powering up when empty.

It might even work without tracks, but rolling resistance will eat into the power produced.

If the place you're excavating has useful dirt, then it's a total win-win.

The trucks should be able to drive on and off the trucks, so they can pick up and dump the dirt in a flexible manner.

The trucks are a form of distributed generation - if one breaks down, not harm done, the system keeps on working.

This is really sweet.

(There are several proposals for earth-side power storage based on that, but for Mars-scale, it's not a bad way to generate electricity)
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/08/2018 02:50 pm
What is the outlook for stored hydro on Mars? I envision an insulated reservoir at the top of a cliff or up a mountainside, coupled with another insulated reservoir at the bottom of the cliff via a hydroelectric generator with solar power used to pump the water back to the upper reservoir.
Pretty terrible.
Fifty meters, times a thousand tons = m*g*h = joules.
Or, in numbers, 50m*3.5m/s^2*1000000kg = 175MJ, or 48kWh.

This is about the equivalent of burning twenty kilos of methalox, or about the same power stored in a 250kg battery.

Your numbers are correct, but why such a small reservoir? It is true that the reservoir volume can be increased as energy storage need increases, but I don't see any reason to start with a 10x10x10 meter reservoir. Maybe 100x100x10 meter reservoirs. That would store 4800 kWh which would last overnight if the drain was no greater than 300 kW per hour, or for a week at a drain of 28 kW per hour.

Water is going to be a limiting resource for some time.
Assuming you're going to be able to find 100000 tons may be optimistic.
Plus, you have to add onto the fixed costs of mass launched to mars, the amount needed to seal the reservoir and keep them liquid.

For settlement energy, your water mass would be much higher, (https://forum.nasaspaceflight.com/index.php?topic=40019.msg1518256#msg1518256) especially if scaled for dust storm duration (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1831007#msg1831007) - a natural requirement.

Moreover on unimproved ground your bedrock is a terrible heat sink (https://forum.nasaspaceflight.com/index.php?topic=34836.msg1614340#msg1614340).  You'd allocate much energy to reservoir heating, or else allocate significant industry to insulation.  Perhaps something like a Red Gold aerogel plant (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1863074#msg1863074) could be scaled up for reservoir insulation, so that your reservoir can be a net energy store.
Title: Re: Power options for a Mars settlement
Post by: Lemurion on 10/09/2018 01:03 am
Part of the problem is that certain otherwise useful options are significantly less useful on Mars than they are on Earth. I like stored hydro but the lower gravity is going to hurt it as a power storage option. Battery storage has the advantage that the batteries themselves are going to work just as well on Mars as they do on Earth. Yes, you'll need a larger solar array to generate the power for them, but the batteries themselves don't have to scale to offset reduced efficiency.



Title: Re: Power options for a Mars settlement
Post by: jpo234 on 10/09/2018 08:20 am
Don't know where exactly to put this, but I think it's vaguely relevant:

https://youtu.be/nsRNiv7EMfA
Title: Re: Power options for a Mars settlement
Post by: oiorionsbelt on 10/09/2018 05:11 pm
These Mark Watney type solar array deployment schemes seem inferior to the party blower idea proposed by EM.
They would enable solar panels to be deployed with compressed Martian air.

https://gifimage.net/party-blower-gif-9/
Title: Re: Power options for a Mars settlement
Post by: Lar on 10/10/2018 04:57 am
I wish to Lar that a new thread called "TE on Mars" be created, and a search and transfer procedure initiated to move the TE discussion there, since it has completely overwhelmed this thread.
Your wish is my scutwork.... I've carved out a lot of posts and moved them to a new thread titled Triboelectric Power

https://forum.nasaspaceflight.com/index.php?topic=46533.0

It is possible that I missed some. It is possible that I moved some by mistake. Use the report to mod on those posts and reference the other thread by number so whoever handles it finds it a lot easier.

Further discussion of TE in this thread is off topic.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/12/2018 03:51 pm
Part of the problem is that certain otherwise useful options are significantly less useful on Mars than they are on Earth. I like stored hydro but the lower gravity is going to hurt it as a power storage option. Battery storage has the advantage that the batteries themselves are going to work just as well on Mars as they do on Earth. Yes, you'll need a larger solar array to generate the power for them, but the batteries themselves don't have to scale to offset reduced efficiency.

Storage

Gravity isn't an issue; you could site your upper reservoir 2.6x higher (upslope) to get the same power.  Or you could go even higher, for more power, but that does call for novel equipment pressure specs. 

Water temperature and mass are real issues, though.  For example, dust storm power for 30 sols at 1 MW is 2.7 trillion J, plus conversion losses, plus energy for reservoir temperature regulation at, say, -100 C.  It's a hard challenge.

Alternately, a great battery cargo would be needed to deliver that same 2.7 trillion J.  For example, a farm of future Li rechargeable batteries, having optimistic specific energy of 1.3 million J/kg, would mass ~ 2100 t.

Or you could consider manufacturing a battery farm on Mars - but is there a plausible, low-mass production system?

NASA continues to explore fuel cells (https://solarsystem.nasa.gov/system/downloadable_items/716_Energy_Storage_Tech_Report_FINAL.PDF) for such reasons.


(http://www.lakematthew.com/wp-content/uploads/2018/10/Fig5-1.png)
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/12/2018 07:12 pm
toss in a few Kilopower reactors to play it safe. Then there's no need to use methane from ISRU as a backup.

No, use methalox as backup, without nuclear reactors.

$.
And when the dust storm hits BEFORE they have had a chance to produce enough Methalox for those fuel cells (or generators)? They still will run out of power. Plus ISRU production will come to a grinding halt (or rather be used up as backup power). Then they could miss their return launch window and might have to stay another 2 years and if they are really unlucky, things might get worse even.
I would feel less worried, if the first crews had an already established return capability of sorts by the time they land (e.g. several tankers were landed first with enough fuel for them to make it back). Things get really hairy if some of the ISRU equipment gets damaged.

Cheap GW vs. Expensive MW

One PV payload can give 1 GW max: more than enough to load near-term fleets, even allowing for months of storm shutdown.  And that PV GW would be cheaper than any foreseeable nuclear MW.  So I don't see reason for dedicated settlement nuclear at this point.  All-weather mobile systems might plug in to give a few tens of kW in a low-probability scenario (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1850608#msg1850608), but dedicated nuclear seems pointless now.

John Casani's guess (https://spacenews.com/op-ed-an-argument-for-space-fission-reactors/):

Quote from: John Casani
If KRUSTY is successful, the cost to bring a 1-kWe reactor to flight status should be relatively low: a few hundred million dollars...

--

Spare tanks are good.
Title: Re: Power options for a Mars settlement
Post by: DigitalMan on 10/12/2018 07:46 pm
One of the challenges of nuclear reactors not on earth is the fact that fuel for a nuclear reactor is produced on Earth and launched into space.  Getting approval for these launches could possibly take extraordinary amounts of time for SpaceX.

What would be the challenges of developing a source of fuel for a nuclear reactor on Mars?  I haven't seen any research into this but to be honest I haven't looked very carefully.
Title: Re: Power options for a Mars settlement
Post by: KelvinZero on 10/12/2018 10:18 pm
One of the challenges of nuclear reactors not on earth is the fact that fuel for a nuclear reactor is produced on Earth and launched into space.  Getting approval for these launches could possibly take extraordinary amounts of time for SpaceX.

What would be the challenges of developing a source of fuel for a nuclear reactor on Mars?  I haven't seen any research into this but to be honest I haven't looked very carefully.
Probably true about the political side, but I have often heard that fuel for (at least some designs of) nuclear reactors can be launched extremely safely.. they only become lethally riddled with radiation after being turned on.

Im interested in ISRU for fission plants too.. but Im thinking a bit further ahead: Saturn! :)

(I just stumbled across this chart that suggests a BFS could easily commute between the 9 or so moons of Saturn, mostly in less than a week. THAT is the Flash Gordon science fiction we were promised! )
http://www.projectrho.com/public_html/rocket/appmissiontable.php
https://en.wikipedia.org/wiki/Moons_of_Saturn
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/13/2018 01:29 am
Probably true about the political side, but I have often heard that fuel for (at least some designs of) nuclear reactors can be launched extremely safely.. they only become lethally riddled with radiation after being turned on.
This is true. It doesn't help the political case.
The fuel is a highly regulated substance, though this is slightly less bad if you are using low-enriched uranium.
You are entirely reliant on political whim on if you can launch this one, and have no guarantee of being able to launch the next one.
It is unclear nuclear is better than solar for Mars.

Over on the Powering martian civilisation from ebay (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512) thread, I ballparked mass costs of a 500kW continuous solar power plant at one BFS.
This is $150M or so, launched to, and left on Mars.
This sets a reasonable baseline limit on the cost of power to Mars. It can, even in severe storms, produce 50kW for very extended periods, including several days entirely without light.

This is likely to be considerably cheaper than the cost of even one 5kW continuous reactor, never mind ten, and has no proliferation or political concerns whatsoever.

I have a real trouble believing you can fit refining equipment suitable to process very low grade uranium ore into nearly pure, and then isotopically enriching the uranium, or extracting deuterium from water, for a 500kW reactor in under 150 tons.
This is certainly something to be thinking about only very far down the road. It may in principle be useful for polar installations.
But not soon.

Title: Re: Power options for a Mars settlement
Post by: Yaotzin on 10/13/2018 12:37 pm
Nuclear is less reliable on Earth

Citation please. Nuclear is one of the most reliable power sources that we have.
https://pris.iaea.org/PRIS/WorldStatistics/ThreeYrsUnplannedCapabilityLossFactor.aspx
Varies a lot but often over 5%, sometimes into the double digits. By contrast solar is around 0% (lack of moving parts is so handy). All big coal/gas/nuclear power plants are surprisingly unreliable.

Quote from: Elmar Moelzer
Compared to routinely used solar, which we've even actually used on Mars. There would be enormous reliability concerns around nuclear for a first mission.

What reliability concerns? Plus, it would be an additional power source.
What we have learned from solar in Mars is that it is not all that reliable. The solar powered Mars rovers are frequently out for months and only survive because of a nuclear powered heating element.
There currently exists no NPP that would function at all on Mars. It would be an entirely new design unlike anything on Earth, in an entirely new environment. If that's not a recipe for unreliability, I don't know what is. Far harder to fix problems there too, of course.

It's true that dust storms make solar unreliable, but it's not a LOM unreliability (for a base, can be for little rovers), so in the end it can be planned around and all comes down to cost. It's also a type of unreliability where the solution is "wait", where nuclear's requires something to be fixed, a huge problem on Mars. Nuclear's unreliability could be planned for too probably, but it only looks cost competitive if we assume it doesn't need to.

In the end the story for nuclear on Mars is very similar to the story on Earth. All its problems are probably solvable, but solutions cost money and make nuclear uncompetitive.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 10/13/2018 03:52 pm
For long time what ever power infrastructure they build they will need storage not just emergency but part of the normal flow while they build up the power capacity.
Fuel cells would work but consume what you are trying the produce and they are not efficient.
Li-Ion batteries are efficient but they are high tech to build and it will be a long time before they are made on Mars. 
Lead-acid batteries are simple to make and while they are a third the energy density of Li-Ion you don't care because you're not lifting them out of a gravity well.
Title: Re: Power options for a Mars settlement
Post by: Mongo62 on 10/13/2018 04:59 pm
What about a small SPS dropped off by a BFS Cargo ship in areostationary Mars orbit, with a rectenna on the ground? Would the microwaves be able to punch through a dust storm? The solar array itself could be smaller in area than a ground-based array, mainly due to 24 hour power production and always being at its optimum pointing angle, and since it is in zero-gee operating conditions it could be made very lightweight.

The main problems for SPS in Earth orbit are 1) power attenuation of the microwave beams due to raindrops (not an issue on Mars) and competition of the rectennas for territory with other uses (again, not an issue on Mars).
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/13/2018 05:08 pm
What about a small SPS dropped off by a BFS Cargo ship in areostationary Mars orbit, with a rectenna on the ground? Would the microwaves be able to punch through a dust storm? The solar array itself could be smaller in area than a ground-based array, mainly due to 24 hour power production and always being at its optimum pointing angle, and since it is in zero-gee operating conditions it could be made very lightweight.
There is no especial reason why this can't work - though it requires a rather more complex and expensive power system.
If you have ISRU anyway, and have backup propellant to return to earth, anything over that amount needed can simply be used as a nearly infinite battery with only benefits to you if you do not need it.
An internal combustion engine (or fuel cell, or gas turbine) is rather simpler to setup and design.
Eventually, SPS may be an interesting option.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/13/2018 09:37 pm
What about a small SPS dropped off by a BFS Cargo ship in areostationary Mars orbit, with a rectenna on the ground? Would the microwaves be able to punch through a dust storm? The solar array itself could be smaller in area than a ground-based array, mainly due to 24 hour power production and always being at its optimum pointing angle, and since it is in zero-gee operating conditions it could be made very lightweight.
There is no especial reason why this can't work - though it requires a rather more complex and expensive power system.
If you have ISRU anyway, and have backup propellant to return to earth, anything over that amount needed can simply be used as a nearly infinite battery with only benefits to you if you do not need it.
An internal combustion engine (or fuel cell, or gas turbine) is rather simpler to setup and design.
Eventually, SPS may be an interesting option.

In orbit, PV cumulative W/kg would be ~ 4x martian surface performance, but microwave conversion efficiency might be only 50%, after Jaffe et al. 2011.  That drops orbiting W/kg to 2x martian surface.  Then the EM propagation inverse-square law slashes power received at the rectenna, ruining performance relative to surface PV.  On Earth, geostationary space power is not commercially competitive - not even in theory - for the same reason (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1828166#msg1828166).

Refs.

Jaffe, P., Pasour, J., Gonzalez, M., Spencer, S., Nurnberger, M., Dunay, J., ... & Jenkins, P. (2011, March). Sandwich module development for space solar power. In Proceedings of the 28th International Symposium on Space Technology and Science.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 10/14/2018 09:20 am
One of the challenges of nuclear reactors not on earth is the fact that fuel for a nuclear reactor is produced on Earth and launched into space.  Getting approval for these launches could possibly take extraordinary amounts of time for SpaceX.

What would be the challenges of developing a source of fuel for a nuclear reactor on Mars?  I haven't seen any research into this but to be honest I haven't looked very carefully.
Probably true about the political side, but I have often heard that fuel for (at least some designs of) nuclear reactors can be launched extremely safely.. they only become lethally riddled with radiation after being turned on.

A new reactor will have only low enriched uranium on board, which is not particulary radioactive. It may be that for long mission life enrichment is up to 20%. Higher than that and you have worries about nuclear proliferation so it tends to be used for military only.

But with a half life of 700 million years, even pure U235 is not what you'd consider radioactive. It'sdecay mode is alpha decay, so you could handle it.

Once the reactor start, then all kinds of nasty fission products start to build up. These cause decay heat (which is what melted cores at Fukushima), may be biologically active (Radioactivr iodine is readily absorbed by nature), and also limit the life of the fuel rods (Xenon gas builds up in the fuel rods, slowing the reaction and making the rods brittle).

So it would be fine to send a reactor to Mars, as long as its not operating until it gets there.

Technically at least. Even politically - people don't object (much) to Uranium ore and even nuclear fuel being moved. They're more concerend about spent fuel.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 10/14/2018 09:35 am
What about a small SPS dropped off by a BFS Cargo ship in areostationary Mars orbit, with a rectenna on the ground? Would the microwaves be able to punch through a dust storm? The solar array itself could be smaller in area than a ground-based array, mainly due to 24 hour power production and always being at its optimum pointing angle, and since it is in zero-gee operating conditions it could be made very lightweight.
There is no especial reason why this can't work - though it requires a rather more complex and expensive power system.
If you have ISRU anyway, and have backup propellant to return to earth, anything over that amount needed can simply be used as a nearly infinite battery with only benefits to you if you do not need it.
An internal combustion engine (or fuel cell, or gas turbine) is rather simpler to setup and design.
Eventually, SPS may be an interesting option.

In orbit, PV cumulative W/kg would be ~ 4x martian surface performance, but microwave conversion efficiency might be only 50%, after Jaffe et al. 2011.  That drops orbiting W/kg to 2x martian surface.  Then the EM propagation inverse-square law slashes power received at the rectenna, ruining performance relative to surface PV.  On Earth, geostationary space power is not commercially competitive - not even in theory - for the same reason (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1828166#msg1828166).


The x4 factor might apply for an equatorial base in a dust storm free zone.

You link to a discussion which suggests that SSP might be commercially competitive if BFR makes the launch cost reductions it promises - and nothing in the discussion contradicted that. Especially for higher (Earth) latitudes where in winter a SPS will produce 40 times as much energy compared to equivalent panels on the ground.

For Mars, orbital power is even more attractive because the launch costs are effectively free. Whether the solar system is on Mars or in Mars orbit, it has already been launched from Earth. (The advantage of Space Solar for Mars would be even greater if Electric Thrust was used - but that's not SpaceX's direction).

The drawback of SPS with microwaves for Mars is one of scale. Even with the closer aerostationary orbit, it would still be effectiveonly from a GW scale. That issue could be overcome with laser power, but that needs new laser developments, and is still inefficient. Laser beaming would probably be viable if we used electric thrusters to deliver cargos to Mars, which would then serve as laser "beamers" to solar panels (and green houses) laid on the ground.  Laser beaming could also be used for mobile bases.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/14/2018 12:09 pm
What about a small SPS dropped off by a BFS Cargo ship in areostationary Mars orbit, with a rectenna on the ground? Would the microwaves be able to punch through a dust storm? The solar array itself could be smaller in area than a ground-based array, mainly due to 24 hour power production and always being at its optimum pointing angle, and since it is in zero-gee operating conditions it could be made very lightweight.
There is no especial reason why this can't work - though it requires a rather more complex and expensive power system.
If you have ISRU anyway, and have backup propellant to return to earth, anything over that amount needed can simply be used as a nearly infinite battery with only benefits to you if you do not need it.
An internal combustion engine (or fuel cell, or gas turbine) is rather simpler to setup and design.
Eventually, SPS may be an interesting option.

In orbit, PV cumulative W/kg would be ~ 4x martian surface performance, but microwave conversion efficiency might be only 50%, after Jaffe et al. 2011.  That drops orbiting W/kg to 2x martian surface.  Then the EM propagation inverse-square law slashes power received at the rectenna, ruining performance relative to surface PV.  On Earth, geostationary space power is not commercially competitive - not even in theory - for the same reason (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1828166#msg1828166).


The x4 factor might apply for an equatorial base in a dust storm free zone.

You link to a discussion which suggests that SSP might be commercially competitive if BFR makes the launch cost reductions it promises - and nothing in the discussion contradicted that. Especially for higher (Earth) latitudes where in winter a SPS will produce 40 times as much energy compared to equivalent panels on the ground.

For Mars, orbital power is even more attractive because the launch costs are effectively free. Whether the solar system is on Mars or in Mars orbit, it has already been launched from Earth. (The advantage of Space Solar for Mars would be even greater if Electric Thrust was used - but that's not SpaceX's direction).

The drawback of SPS with microwaves for Mars is one of scale. Even with the closer aerostationary orbit, it would still be effectiveonly from a GW scale. That issue could be overcome with laser power, but that needs new laser developments, and is still inefficient. Laser beaming would probably be viable if we used electric thrusters to deliver cargos to Mars, which would then serve as laser "beamers" to solar panels (and green houses) laid on the ground.  Laser beaming could also be used for mobile bases.

Competitiveness isn't a spacecraft issue; it's the same physical problem at any scale.  Laser conversion efficiency is close to microwave efficiency, but the inverse-square law still applies, ruining performance at the collector.  That's why no areostationary design is competitive with surface power at same mass.  Likewise, geosats.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/14/2018 12:17 pm
What about a small SPS dropped off by a BFS Cargo ship in areostationary Mars orbit, with a rectenna on the ground? Would the microwaves be able to punch through a dust storm? The solar array itself could be smaller in area than a ground-based array, mainly due to 24 hour power production and always being at its optimum pointing angle, and since it is in zero-gee operating conditions it could be made very lightweight.
There is no especial reason why this can't work - though it requires a rather more complex and expensive power system.
If you have ISRU anyway, and have backup propellant to return to earth, anything over that amount needed can simply be used as a nearly infinite battery with only benefits to you if you do not need it.
An internal combustion engine (or fuel cell, or gas turbine) is rather simpler to setup and design.
Eventually, SPS may be an interesting option.

In orbit, PV cumulative W/kg would be ~ 4x martian surface performance, but microwave conversion efficiency might be only 50%, after Jaffe et al. 2011.  That drops orbiting W/kg to 2x martian surface.  Then the EM propagation inverse-square law slashes power received at the rectenna, ruining performance relative to surface PV.  On Earth, geostationary space power is not commercially competitive - not even in theory - for the same reason (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1828166#msg1828166).


The x4 factor might apply for an equatorial base in a dust storm free zone.

You link to a discussion which suggests that SSP might be commercially competitive if BFR makes the launch cost reductions it promises - and nothing in the discussion contradicted that. Especially for higher (Earth) latitudes where in winter a SPS will produce 40 times as much energy compared to equivalent panels on the ground.

For Mars, orbital power is even more attractive because the launch costs are effectively free. Whether the solar system is on Mars or in Mars orbit, it has already been launched from Earth. (The advantage of Space Solar for Mars would be even greater if Electric Thrust was used - but that's not SpaceX's direction).

The drawback of SPS with microwaves for Mars is one of scale. Even with the closer aerostationary orbit, it would still be effectiveonly from a GW scale. That issue could be overcome with laser power, but that needs new laser developments, and is still inefficient. Laser beaming would probably be viable if we used electric thrusters to deliver cargos to Mars, which would then serve as laser "beamers" to solar panels (and green houses) laid on the ground.  Laser beaming could also be used for mobile bases.

Competitiveness isn't a spacecraft issue; it's the same physical problem at any scale.  Laser conversion efficiency is close to microwave efficiency, but the inverse-square law still applies, ruining performance at the collector.  That's why no areostationary design is competitive with surface power at same mass.  Likewise, geosats.
What's that about inverse-square law?

Not that I think SSP is viable, but all SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

-----
ABCD: Always Be Counting Down
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/14/2018 12:39 pm
SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

QD PV is 6.5 g / m2, for max ~ 60 W on Mars.

Tally your masses, and compare.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/14/2018 12:48 pm


SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

QD PV is 6.5 g / m2, for max ~ 60 W on Mars.

Tally your masses, and compare.

I was asking what the inverse square law has to do with anything.

And when comparing systems, use watt-hours per day avg, or else the numbers are meaningless.

SSP is a better idea on Mars than it is on Earth, but still loses out to ground power.

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: LMT on 10/14/2018 04:58 pm


SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

QD PV is 6.5 g / m2, for max ~ 60 W on Mars.

Tally your masses, and compare.

I was asking what the inverse square law has to do with anything.

And when comparing systems, use watt-hours per day avg, or else the numbers are meaningless.

SSP is a better idea on Mars than it is on Earth, but still loses out to ground power.

It cuts received power density with the square of distance, naturally.

If you calc the mass required to get 60 W / m2 out of your rectenna, you'll see why areosat and geosat SSP systems aren't competitive.  Then you can calc Wh too.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/14/2018 05:15 pm


SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

QD PV is 6.5 g / m2, for max ~ 60 W on Mars.

Tally your masses, and compare.

I was asking what the inverse square law has to do with anything.

And when comparing systems, use watt-hours per day avg, or else the numbers are meaningless.

SSP is a better idea on Mars than it is on Earth, but still loses out to ground power.

It cuts received power density with the square of distance, naturally.

If you calc the mass required to get 60 W / m2 out of your rectenna, you'll see why areosat and geosat SSP systems aren't competitive.  Then you can calc Wh too.
You mentioned it with respect to laser too.

On earth, given the possible wavelengths and height of GEO, SSP is a non-starter.

On Mars, with a lower orbit, and using a laser or short wavelength RF, receivers that capture the entire beam are practical, and so the inverse square law is completely moot.

It's still a losing proposition because of transmission losses and most importantly the batshit insane system complexity, but the fundamental law you're looking for is diffraction limit, not inverse square law.



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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: alexterrell on 10/14/2018 07:28 pm


SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

QD PV is 6.5 g / m2, for max ~ 60 W on Mars.

Tally your masses, and compare.

I was asking what the inverse square law has to do with anything.

And when comparing systems, use watt-hours per day avg, or else the numbers are meaningless.

SSP is a better idea on Mars than it is on Earth, but still loses out to ground power.

It cuts received power density with the square of distance, naturally.

If you calc the mass required to get 60 W / m2 out of your rectenna, you'll see why areosat and geosat SSP systems aren't competitive.  Then you can calc Wh too.

Why not 2KW/m2? That would be a sensible power density for laser transmission on Mars, handled by conventional solar panels.

The inverse square law just means you need a larger receiver or transmitter, which means you need a higher power level. That probably means microwave transmission from stationary orbit needs to be about 1GW on Mars and about 2-4GW on Earth.

If we can learn to affordably construct and maintain large, light weight objects in space, then space solar power will undercut ground based solar power at BFR launch rates.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 10/14/2018 07:38 pm
It's still a losing proposition because of transmission losses and most importantly the batshit insane system complexity, but the fundamental law you're looking for is diffraction limit, not inverse square law.

If you take moncrhomatic lasers from Mars orbit, then you're probably looking at a 20% of the efficiency compared to ground based PV.

Per MWh, I suspect ground based will be cheaper. However, if we add in the costs of handling intermittency - especially at high latitude - that may not be the case.

If we were to start from orbit (if we were to use SEP to send cargo to Mars), then it would make sense to leave the solar arrays in orbit, rather than taking them to the surface.

Lasers would also have the advantage of being able to cover multiple targets. A 2KW/m2 beam could even power large mobile exploratation vehicles. Microwaves have the efficiency advantage, but need to be on a scale of GW.

Thanks to the invesrse square law - there was another rule of thumb I saw that:
 Receiver_Diameter x Transmitter_Diameter > Wavelength x Distance).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/14/2018 07:58 pm
Problem with laser is that I'm not aware of a laser that's at 50% efficiency, nor a receiver that's there in reality.  In practice, 10% end to end, on top of the initial collection efficiency, is more realistic.

Also, you'll need to reject a lot of power in orbit since the transmitter is so bad.

On the flip side, surface PV has a built in 25% extra loss due to the daily cycle, so the transmission efficiency is not that out there.

PV cells in orbit can be much lighter amd don't get dirty.

But lastly - I ain't never seen multi MWatt continuous wave lasers yet, not to mention space-worthy ones.

I don't think anyone  SpaceX particularly, is buildong any for the Mars base. It a ton of complexity, a lot of undeveloped hardware, amd overall worse performance.  What's to like?

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ABCD: Always Be Counting Down
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/14/2018 08:58 pm
Problem with laser is that I'm not aware of a laser that's at 50% efficiency, nor a receiver that's there in reality.  In practice, 10% end to end, on top of the initial collection efficiency, is more realistic.
I have a 35% 6W blue one on my desk.

About the third hit on 'pump laser efficient' was this product brief of a 150W range of diode pump LASERs. (https://resource.lumentum.com/s3fs-public/technical-library-items/stdiodepumplaser-ds-cl-ae.pdf)

This lists 48% typical efficiency at 930nm.

This paper (http://dergipark.gov.tr/download/article-file/148089) gives the following graph of a typical monocrystalline cell efficiency.
(https://i.imgur.com/Gqi0yh4.jpg) This is comparable with other graphs I found.

The output peaks at 890nm or so, and is very close to this figure at 930nm.
The output current is around 0.5A/W, and at a cell output voltage of 0.56V (typical peak power voltage), this is 28% conversion efficiency.
(slightly better than this panels performance in normal sun per watt).

This hits 13.5% or so DC-DC efficiency, with the first parts I found. It would not surprise me to be able to hit 19% DC-DC efficiency, with better off-the-shelf solar panels.

I don't believe this makes any sense in the context of powering a surface installation for ISRU.
You are enormously better just putting it all on Mars, and overproducing and storing it for inclement weather.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/14/2018 09:06 pm
Problem with laser is that I'm not aware of a laser that's at 50% efficiency, nor a receiver that's there in reality.  In practice, 10% end to end, on top of the initial collection efficiency, is more realistic.
I have a 35% 6W blue one on my desk.

About the third hit on 'pump laser efficient' was this product brief of a 150W range of diode pump LASERs. (https://resource.lumentum.com/s3fs-public/technical-library-items/stdiodepumplaser-ds-cl-ae.pdf)

This lists 48% typical efficiency at 930nm.

This paper (http://dergipark.gov.tr/download/article-file/148089) gives the following graph of a typical monocrystalline cell efficiency.
(https://i.imgur.com/Gqi0yh4.jpg) This is comparable with other graphs I found.

The output peaks at 890nm or so, and is very close to this figure at 930nm.
The output current is around 0.5A/W, and at a cell output voltage of 0.56V (typical peak power voltage), this is 28% conversion efficiency.
(slightly better than this panels performance in normal sun per watt).

This hits 13.5% or so DC-DC efficiency, with the first parts I found. It would not surprise me to be able to hit 19% DC-DC efficiency, with better off-the-shelf solar panels.

I don't believe this makes any sense in the context of powering a surface installation for ISRU.
You are enormously better just putting it all on Mars, and overproducing and storing it for inclement weather.

Agreed 100% on the conclusion.  SSP, even on Mars, loses out.

As for the receiver efficiency, matched single junction cells reach very high efficiencies, when bathed with uniform light.

However, the light field produced by a laser is anything but uniform.  A combination of diffraction artifacts and atmospheric effects, it's just a random jumble of intensities.  Since the receiver is comprised of multiple cells, the resultant loss in efficiency is very large.

Title: Re: Power options for a Mars settlement
Post by: Asteroza on 10/15/2018 12:22 am
What about a small SPS dropped off by a BFS Cargo ship in areostationary Mars orbit, with a rectenna on the ground? Would the microwaves be able to punch through a dust storm? The solar array itself could be smaller in area than a ground-based array, mainly due to 24 hour power production and always being at its optimum pointing angle, and since it is in zero-gee operating conditions it could be made very lightweight.

The main problems for SPS in Earth orbit are 1) power attenuation of the microwave beams due to raindrops (not an issue on Mars) and competition of the rectennas for territory with other uses (again, not an issue on Mars).


There was a concept to do beamed power using a mod of the NASA DRM missions, so cargo bimodal nuclear rockets would be available to give power to ground receivers. Naturally, this presupposes a steady increasing collection of bimodal NTR's from cargo missions, but since the reactors are extant, it avoids landing full power systems in the cargo landers (base/ISRU had keepalive levels of solar PV/batteries but never full power). Since a SpaceX system won't naturally have an increasing collection of bimodal NTR's this makes the discussion moot, but there was a compelling case for beamed power from a fixed point in the sky. Whether swapping the reactors for a PV array in orbit makes things better or worse depends on the arrangements, but the HESPeruS design may be workable.

There is the interesting intersection where a large flexible blanket solar PV array on the ground could also incorporate rectenna elements, if one intends to use the solar PV for keepalive and use SPS microwave, rather than SPS laser.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 10/15/2018 02:53 am
Problem with laser is that I'm not aware of a laser that's at 50% efficiency, nor a receiver that's there in reality.  In practice, 10% end to end, on top of the initial collection efficiency, is more realistic.
I have a 35% 6W blue one on my desk.

About the third hit on 'pump laser efficient' was this product brief of a 150W range of diode pump LASERs. (https://resource.lumentum.com/s3fs-public/technical-library-items/stdiodepumplaser-ds-cl-ae.pdf)

This lists 48% typical efficiency at 930nm.

This paper (http://dergipark.gov.tr/download/article-file/148089) gives the following graph of a typical monocrystalline cell efficiency.
(https://i.imgur.com/Gqi0yh4.jpg) This is comparable with other graphs I found.

The output peaks at 890nm or so, and is very close to this figure at 930nm.
The output current is around 0.5A/W, and at a cell output voltage of 0.56V (typical peak power voltage), this is 28% conversion efficiency.
(slightly better than this panels performance in normal sun per watt).

This hits 13.5% or so DC-DC efficiency, with the first parts I found. It would not surprise me to be able to hit 19% DC-DC efficiency, with better off-the-shelf solar panels.

I don't believe this makes any sense in the context of powering a surface installation for ISRU.
You are enormously better just putting it all on Mars, and overproducing and storing it for inclement weather.
The problem is that pump lasers (diode lasers, usually), while very efficient, are not coherent enough to get to diffraction-limited performance.

And mm-wave frequency RF converters are very expensive and not as efficient. To get high efficiency and low cost and low weight, you need to use lower frequency, like used for your microwave oven.

That means your spot size is large. That means your minimum-viable-size for space based beamed power is really in the Gigawatts region, at least in my opinion. Many have proposed smaller systems, but the numbers work against you unless you're operating at very large scale.


Also, lasers and microwave electronics are expensive. The receivers for it are expensive as well. You're doing photon/electricity conversions 3 times instead of just once. cell-to-ground efficiency for microwaves is, realistically, 50% at most. Lasers is more like 25% (50% laser, 50% cell), at best. So you're paying a LOT.


Turns out batteries work great, and hydrogen production (used for methane and what would likely be the greatest energy consumer) doesn't mind being cycled on and off with available sunlight.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 03:13 am
.. and so, once again, we're left with two potential candidates..  solar, and nuclear.

I did btw look at an idea from upthread - running a quarry operation with a trolly system over a large elevation change, basically just moving sand downhill.

It's actually not all that bad, but it's a lot of infrastructure to set up.

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: Semmel on 10/15/2018 06:45 am
.. and so, once again, we're left with two potential candidates..  solar, and nuclear.

I did btw look at an idea from upthread - running a quarry operation with a trolly system over a large elevation change, basically just moving sand downhill.

It's actually not all that bad, but it's a lot of infrastructure to set up.

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ABCD: Always Be Counting Down

.. and wind turbines.

https://www.researchgate.net/profile/Henry_Haslach_Jr/publication/252363322_Wind_Energy_a_Resource_for_a_Human_Mission_to_Mars/links/5924402eaca27295a8b3a1a1/Wind-Energy-a-Resource-for-a-Human-Mission-to-Mars.pdf

From conclusions:
Quote
At the March 1985 Marshall Space Flight Center's Manned Mars Mission Study a 25 kW and a 100 kW nuclear plant were proposed for the mission. The reactor of the 100 kW system has a conical shape with a 4.3 meter base diameter and a height.of about 32 meters. The 100 kW with mass 2720 kg has a power output of 37 W/kg, while the 25 kW system has a 1500 kg mass and 177 produces 17 W/kg. None of the nuclear plant compo­nents have obvious multi-use capability.
The mass of the giromill has been estimated as 175 kg. Adding 100 kg for gearing, supports, and generator gives a total mass of about 275 kg. In a 14 rn/s wind, the giromill produces 2.1 kW for 7.64 W/kg. However, in the 25 rn/s winds estimated for slope winds, the turbine produces 12.13 kW or 44.1 W/kg. In terms of power produced per unit mass, wind energy is competitive with nuclear power.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 07:07 am
.. and so, once again, we're left with two potential candidates..  solar, and nuclear.

I did btw look at an idea from upthread - running a quarry operation with a trolly system over a large elevation change, basically just moving sand downhill.

It's actually not all that bad, but it's a lot of infrastructure to set up.

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ABCD: Always Be Counting Down

.. and wind turbines.

https://www.researchgate.net/profile/Henry_Haslach_Jr/publication/252363322_Wind_Energy_a_Resource_for_a_Human_Mission_to_Mars/links/5924402eaca27295a8b3a1a1/Wind-Energy-a-Resource-for-a-Human-Mission-to-Mars.pdf

From conclusions:
Quote
At the March 1985 Marshall Space Flight Center's Manned Mars Mission Study a 25 kW and a 100 kW nuclear plant were proposed for the mission. The reactor of the 100 kW system has a conical shape with a 4.3 meter base diameter and a height.of about 32 meters. The 100 kW with mass 2720 kg has a power output of 37 W/kg, while the 25 kW system has a 1500 kg mass and 177 produces 17 W/kg. None of the nuclear plant compo­nents have obvious multi-use capability.
The mass of the giromill has been estimated as 175 kg. Adding 100 kg for gearing, supports, and generator gives a total mass of about 275 kg. In a 14 rn/s wind, the giromill produces 2.1 kW for 7.64 W/kg. However, in the 25 rn/s winds estimated for slope winds, the turbine produces 12.13 kW or 44.1 W/kg. In terms of power produced per unit mass, wind energy is competitive with nuclear power.
I'm surprised that at 1% air density, the turbine is competitive, unless it's being compared to a crazy heavy nuclear reactor.

Can't download the PDF on my phone, so will leave it at that.

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: Semmel on 10/15/2018 08:38 am
I'm surprised that at 1% air density, the turbine is competitive, unless it's being compared to a crazy heavy nuclear reactor.

Can't download the PDF on my phone, so will leave it at that.


I think they compared it to the design proposed at that time (30 years ago). Today, there might be much more mass efficient nuclear reactor designs. But maybe also more mass efficient turbine designs, I didnt find a new study on this unfortunately. In any case, wind might be useful as an emergency power source during dust storms. The nice thing about dust storms is, that there should be more than average wind.. So maybe complementary to solar in order to keep humans and plants alive during dust storms but not enough for fuel production.

Also, come to speak of dust storms. Its not just that we need energy in this times... also plants would die for the lack of light. So a design where sunlight is used directly for plant growth is prone to fail due to dust storms. Therefore, plants have to be powered by lamps. Did we factor in plant lights for calculating the power needs of the colony?
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 10/15/2018 10:10 am
.. and so, once again, we're left with two potential candidates..  solar, and nuclear.

I did btw look at an idea from upthread - running a quarry operation with a trolly system over a large elevation change, basically just moving sand downhill.

It's actually not all that bad, but it's a lot of infrastructure to set up.

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ABCD: Always Be Counting Down

.. and wind turbines.

https://www.researchgate.net/profile/Henry_Haslach_Jr/publication/252363322_Wind_Energy_a_Resource_for_a_Human_Mission_to_Mars/links/5924402eaca27295a8b3a1a1/Wind-Energy-a-Resource-for-a-Human-Mission-to-Mars.pdf

From conclusions:
Quote
At the March 1985 Marshall Space Flight Center's Manned Mars Mission Study a 25 kW and a 100 kW nuclear plant were proposed for the mission. The reactor of the 100 kW system has a conical shape with a 4.3 meter base diameter and a height.of about 32 meters. The 100 kW with mass 2720 kg has a power output of 37 W/kg, while the 25 kW system has a 1500 kg mass and 177 produces 17 W/kg. None of the nuclear plant compo­nents have obvious multi-use capability.
The mass of the giromill has been estimated as 175 kg. Adding 100 kg for gearing, supports, and generator gives a total mass of about 275 kg. In a 14 rn/s wind, the giromill produces 2.1 kW for 7.64 W/kg. However, in the 25 rn/s winds estimated for slope winds, the turbine produces 12.13 kW or 44.1 W/kg. In terms of power produced per unit mass, wind energy is competitive with nuclear power.

It's one of these counterintuitive thrust vs. specific impulse kinda things. Wind power is equivalent to kinetic energy, which is 1/mv^2, and the v of that energy passing through gives you a v^3 relationship.

So even at 1/75 density, the v^3 means that Martian winds have 1/4 the power per unit area that they do on Earth. Whereas force is v^2 which means no impaled Watneys. With lower gravity, you can make inflatable turbine blades. 30m/s winds are possible in slope areas, with a turbine starting 15-20m off the ground.

One big advantage of simply having wind power is that during a dust storm, the amount of dust in the atmosphere is quite high, which increases air density and power (something the authors refer to as a "sandmill"). Nice to have a bit of bonus power in a pinch.

A recent study, with an experimental windmill tested in a wind tunnel:

https://www.hou.usra.edu/meetings/amazonian2018/pdf/4004.pdf

Note this is a small windmill idea to stick on landers, and wind velocity greatly increases with altitude even a few metres above ground. 10-20kW wind turbines are feasible.

And these:

https://www.lpi.usra.edu/publications/reports/CB-979/houston.pdf
https://spectrum.library.concordia.ca/36176/1/low_reynolds_number.doc (some useful equations there)

With the enormous height of a BFS, and assuming the first few are designed to become colony cores, you could conceivably rig some kind of turbine from them.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 01:12 pm


.. and so, once again, we're left with two potential candidates..  solar, and nuclear.

I did btw look at an idea from upthread - running a quarry operation with a trolly system over a large elevation change, basically just moving sand downhill.

It's actually not all that bad, but it's a lot of infrastructure to set up.

-----
ABCD: Always Be Counting Down

.. and wind turbines.

https://www.researchgate.net/profile/Henry_Haslach_Jr/publication/252363322_Wind_Energy_a_Resource_for_a_Human_Mission_to_Mars/links/5924402eaca27295a8b3a1a1/Wind-Energy-a-Resource-for-a-Human-Mission-to-Mars.pdf

From conclusions:
Quote
At the March 1985 Marshall Space Flight Center's Manned Mars Mission Study a 25 kW and a 100 kW nuclear plant were proposed for the mission. The reactor of the 100 kW system has a conical shape with a 4.3 meter base diameter and a height.of about 32 meters. The 100 kW with mass 2720 kg has a power output of 37 W/kg, while the 25 kW system has a 1500 kg mass and 177 produces 17 W/kg. None of the nuclear plant compo­nents have obvious multi-use capability.
The mass of the giromill has been estimated as 175 kg. Adding 100 kg for gearing, supports, and generator gives a total mass of about 275 kg. In a 14 rn/s wind, the giromill produces 2.1 kW for 7.64 W/kg. However, in the 25 rn/s winds estimated for slope winds, the turbine produces 12.13 kW or 44.1 W/kg. In terms of power produced per unit mass, wind energy is competitive with nuclear power.

It's one of these counterintuitive thrust vs. specific impulse kinda things. Wind power is equivalent to kinetic energy, which is 1/mv^2, and the v of that energy passing through gives you a v^3 relationship.

So even at 1/75 density, the v^3 means that Martian winds have 1/4 the power per unit area that they do on Earth. Whereas force is v^2 which means no impaled Watneys. With lower gravity, you can make inflatable turbine blades. 30m/s winds are possible in slope areas, with a turbine starting 15-20m off the ground.

One big advantage of simply having wind power is that during a dust storm, the amount of dust in the atmosphere is quite high, which increases air density and power (something the authors refer to as a "sandmill"). Nice to have a bit of bonus power in a pinch.

A recent study, with an experimental windmill tested in a wind tunnel:

https://www.hou.usra.edu/meetings/amazonian2018/pdf/4004.pdf

Note this is a small windmill idea to stick on landers, and wind velocity greatly increases with altitude even a few metres above ground. 10-20kW wind turbines are feasible.

And these:

https://www.lpi.usra.edu/publications/reports/CB-979/houston.pdf
https://spectrum.library.concordia.ca/36176/1/low_reynolds_number.doc (some useful equations there)

With the enormous height of a BFS, and assuming the first few are designed to become colony cores, you could conceivably rig some kind of turbine from them.

Wait...  At same velocity, you still get linear dependency to density.

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 10/15/2018 01:52 pm
Wait...  At same velocity, you still get linear dependency to density.

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ABCD: Always Be Counting Down



Yep. But the v^3 of the wind power equation simply means the same wind has to blow a little (~4x) faster to get the same power as on Earth. It's limited, but winds on Mars seem to be fairly constant.

(https://www.windpowerengineering.com/wp-content/uploads/2014/12/Wind-Power-calculation.jpg)

The k constant is for Imperial/metric conversion and can be ignored.

Mars surface winds are only around ~7m/s and 2.3W/m^2, but merely doubling the encountered windspeed (eg with a 15m mast) gives 23W/m^2. Better sites may yield better windspeeds, so they are at least an option. You only get a small amount of power compared to terrestrial windfarms, though there may be sites on Mars (slope winds) which provide power yields that are comparable.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 02:02 pm
Wait...  At same velocity, you still get linear dependency to density.

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ABCD: Always Be Counting Down



Yep. But the v^3 of the wind power equation simply means the same wind has to blow a little (~4x) faster to get the same power as on Earth. It's limited, but winds on Mars seem to be fairly constant.

(https://www.windpowerengineering.com/wp-content/uploads/2014/12/Wind-Power-calculation.jpg)

The k constant is for Imperial/metric conversion and can be ignored.
4x as fast is not "a little".  30 MPH is a nice wind.  120 is a major hurricane.

Is there information that Mars has winds that are consistent over the day and are 4x as fast?

If it does, that would bring it back to Earth levels - which we xan discuss separately. 

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 10/15/2018 03:22 pm
Wait...  At same velocity, you still get linear dependency to density.

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ABCD: Always Be Counting Down



Yep. But the v^3 of the wind power equation simply means the same wind has to blow a little (~4x) faster to get the same power as on Earth. It's limited, but winds on Mars seem to be fairly constant.

(https://www.windpowerengineering.com/wp-content/uploads/2014/12/Wind-Power-calculation.jpg)

The k constant is for Imperial/metric conversion and can be ignored.
4x as fast is not "a little".  30 MPH is a nice wind.  120 is a major hurricane.

Is there information that Mars has winds that are consistent over the day and are 4x as fast?

If it does, that would bring it back to Earth levels - which we xan discuss separately. 

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ABCD: Always Be Counting Down



The linked article which sparked this discussion assumed a 14m/s windspeed just off the ground. This is in good agreement with dust devil horizontal speed measurements and seems to fit with discarded parachute trajectories. Dust devils are a proxy for ambient wind speeds.

Dust devil horizontal speed measurement:
http://www.lmd.jussieu.fr/~aslmd/pub/REF/2014Icar..227....8R.pdf
Weibull distribution for Curiosity windspeeds: http://www-mars.lmd.jussieu.fr/granada2017/abstracts/viudez-moreiras_granada2017.pdf
Wind speed estimate of discarded heat shield/parachute:
https://meetingorganizer.copernicus.org/EPSC2017/EPSC2017-490.pdf
HIRISE dust devil windspeed measurement:
https://arxiv.org/pdf/1301.6130.pdf

Note for the dust devils that ambient winds appear to be "only" 12m/s at 10m off the ground, with 3/4 of the measured speeds being above 15m/s. The HIRISE analysis indicates faster ambient winds, which are in agreement with the Mars Climate Database (generated by the Global Climate Model).

Dust devil horizontal speed relation to ambient wind speeds:
http://oro.open.ac.uk/34313/
Dust devil speed is in agreement with wind speeds a few tens of metres above the surface, making a good proxy.

In any case, we will know a lot more once ExoMars lands, with its MARBL high altitude wind speed measurement system.

Wind won't be the only power option for Mars - but it can certainly complement solar even so due to advantages offered by reduced wind pressure and gravity. After all, we are discussing solar where the solar constant is less than 1/2 of Earth's.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/15/2018 03:25 pm


SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

QD PV is 6.5 g / m2, for max ~ 60 W on Mars.

Tally your masses, and compare.

I was asking what the inverse square law has to do with anything.

And when comparing systems, use watt-hours per day avg, or else the numbers are meaningless.

SSP is a better idea on Mars than it is on Earth, but still loses out to ground power.

It cuts received power density with the square of distance, naturally.

If you calc the mass required to get 60 W / m2 out of your rectenna, you'll see why areosat and geosat SSP systems aren't competitive.  Then you can calc Wh too.
You mentioned it with respect to laser too.

On earth, given the possible wavelengths and height of GEO, SSP is a non-starter.

On Mars, with a lower orbit, and using a laser or short wavelength RF, receivers that capture the entire beam are practical, and so the inverse square law is completely moot.

It's still a losing proposition because of transmission losses and most importantly the batshit insane system complexity, but the fundamental law you're looking for is diffraction limit, not inverse square law.

No, 1/r^2 must be factored in, regardless of EM frequency.  Short range lab tests (km scale) don't factor it in because they're short-range.  Any notional orbital SSP must factor it in explicitly, else the collector's output power will be badly overstated.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 03:30 pm
Wait...  At same velocity, you still get linear dependency to density.

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ABCD: Always Be Counting Down



Yep. But the v^3 of the wind power equation simply means the same wind has to blow a little (~4x) faster to get the same power as on Earth. It's limited, but winds on Mars seem to be fairly constant.

(https://www.windpowerengineering.com/wp-content/uploads/2014/12/Wind-Power-calculation.jpg)

The k constant is for Imperial/metric conversion and can be ignored.
4x as fast is not "a little".  30 MPH is a nice wind.  120 is a major hurricane.

Is there information that Mars has winds that are consistent over the day and are 4x as fast?

If it does, that would bring it back to Earth levels - which we xan discuss separately. 

-----
ABCD: Always Be Counting Down



The linked article which sparked this discussion assumed a 14m/s windspeed just off the ground. This is in good agreement with dust devil horizontal speed measurements and seems to fit with discarded parachute trajectories. Dust devils are a proxy for ambient wind speeds.

Dust devil horizontal speed measurement:
http://www.lmd.jussieu.fr/~aslmd/pub/REF/2014Icar..227....8R.pdf
Weibull distribution for Curiosity windspeeds: http://www-mars.lmd.jussieu.fr/granada2017/abstracts/viudez-moreiras_granada2017.pdf
Wind speed estimate of discarded heat shield/parachute:
https://meetingorganizer.copernicus.org/EPSC2017/EPSC2017-490.pdf
HIRISE dust devil windspeed measurement:
https://arxiv.org/pdf/1301.6130.pdf

Note for the dust devils that ambient winds appear to be "only" 12m/s at 10m off the ground, with 3/4 of the measured speeds being above 15m/s. The HIRISE analysis indicates faster ambient winds, which are in agreement with the Mars Climate Database (generated by the Global Climate Model).

Dust devil horizontal speed relation to ambient wind speeds:
http://oro.open.ac.uk/34313/
Dust devil speed is in agreement with wind speeds a few tens of metres above the surface, making a good proxy.

In any case, we will know a lot more once ExoMars lands, with its MARBL high altitude wind speed measurement system.

Wind won't be the only power option for Mars - but it can certainly complement solar even so due to advantages offered by reduced wind pressure and gravity. After all, we are discussing solar where the solar constant is less than 1/2 of Earth's.
14 m/s, divided by 4, is what - less than 8 mph.  You're not making power out of that...

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: LMT on 10/15/2018 03:45 pm
.. and so, once again, we're left with two potential candidates..  solar, and nuclear.

I did btw look at an idea from upthread - running a quarry operation with a trolly system over a large elevation change, basically just moving sand downhill.

It's actually not all that bad, but it's a lot of infrastructure to set up.

-----
ABCD: Always Be Counting Down

.. and wind turbines.

https://www.researchgate.net/profile/Henry_Haslach_Jr/publication/252363322_Wind_Energy_a_Resource_for_a_Human_Mission_to_Mars/links/5924402eaca27295a8b3a1a1/Wind-Energy-a-Resource-for-a-Human-Mission-to-Mars.pdf

From conclusions:
Quote
At the March 1985 Marshall Space Flight Center's Manned Mars Mission Study a 25 kW and a 100 kW nuclear plant were proposed for the mission. The reactor of the 100 kW system has a conical shape with a 4.3 meter base diameter and a height.of about 32 meters. The 100 kW with mass 2720 kg has a power output of 37 W/kg, while the 25 kW system has a 1500 kg mass and 177 produces 17 W/kg. None of the nuclear plant compo­nents have obvious multi-use capability.
The mass of the giromill has been estimated as 175 kg. Adding 100 kg for gearing, supports, and generator gives a total mass of about 275 kg. In a 14 rn/s wind, the giromill produces 2.1 kW for 7.64 W/kg. However, in the 25 rn/s winds estimated for slope winds, the turbine produces 12.13 kW or 44.1 W/kg. In terms of power produced per unit mass, wind energy is competitive with nuclear power.

Lower wind speeds present a hard problem for martian wind turbines.  James et al. 1999 compared a buoyant system against previous designs such as those of Haslach, Hemmet et al., Savonius, and Darrieus.  They noted that the "feasible wind speed" ranged from 22-30 m/s.  Table 1.

Refs.

James, G., Chamitoff, G., & Barker, D. (1999, August). Design and resource requirements for successful wind energy production on Mars. In Second International Mars Society Convention, Boulder, CO.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 03:56 pm


SSPs assume a large enough receiver, which jn the case of laser is very practical in size.

QD PV is 6.5 g / m2, for max ~ 60 W on Mars.

Tally your masses, and compare.

I was asking what the inverse square law has to do with anything.

And when comparing systems, use watt-hours per day avg, or else the numbers are meaningless.

SSP is a better idea on Mars than it is on Earth, but still loses out to ground power.

It cuts received power density with the square of distance, naturally.

If you calc the mass required to get 60 W / m2 out of your rectenna, you'll see why areosat and geosat SSP systems aren't competitive.  Then you can calc Wh too.
You mentioned it with respect to laser too.

On earth, given the possible wavelengths and height of GEO, SSP is a non-starter.

On Mars, with a lower orbit, and using a laser or short wavelength RF, receivers that capture the entire beam are practical, and so the inverse square law is completely moot.

It's still a losing proposition because of transmission losses and most importantly the batshit insane system complexity, but the fundamental law you're looking for is diffraction limit, not inverse square law.

No, 1/r^2 must be factored in, regardless of EM frequency.  Short range lab tests (km scale) don't factor it in because they're short-range.  Any notional orbital SSP must factor it in explicitly, else the collector's output power will be badly overstated.

Very roughly speaking, with 1 mm RF shooting over 10,000 km, a 100 m transmitter can create a 100 m spot.

With a 1 um NIR laser, a 1 m transmitter can create a 10 m spot.

Subject to these sizes, which are diffraction limited, where and how exactly are you going to factor in 1/r^2?

Here's a riddle for you.  Two comm sats have antennas that cover the same footprint.  Both provide the same power level to the receivers within the footprint.  One comm sat is in LEO, the other is in GEO, 100x as far.

Do you think the GEO sat transmitter needs to operate at:

A) 100^2=10,000x as much power
B) 100x as much power
C) 1x as much power
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/15/2018 04:54 pm
Two comm sats have antennas that cover the same footprint.  Both provide the same power level to the receivers within the footprint.  One comm sat is in LEO, the other is in GEO, 100x as far.

Do you think the GEO sat transmitter needs to operate at:

A) 100^2=10,000x as much power
B) 100x as much power
C) 1x as much power

(A), assuming same directivity etc.  If a method is to give very different result, I'd say the experiment needs to show clearly how the method's power density doesn't follow 1/r^2 in the far field (not near field).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 05:23 pm
Two comm sats have antennas that cover the same footprint.  Both provide the same power level to the receivers within the footprint.  One comm sat is in LEO, the other is in GEO, 100x as far.

Do you think the GEO sat transmitter needs to operate at:

A) 100^2=10,000x as much power
B) 100x as much power
C) 1x as much power

(A), assuming same directivity etc.  If a method is to give very different result, I'd say the experiment needs to show clearly how the method's power density doesn't follow 1/r^2 in the far field (not near field).

Read the question again.  "Same footprint".   

The minimal footprint is dictated by many considerations, such as diffraction limit, power density, etc.

The assumption is always that a receiver is built that is large enough to contain the transmission beam.  System parameters are chosen so that this is practical, or else the system is a non-starter.

Title: Re: Power options for a Mars settlement
Post by: LMT on 10/15/2018 06:44 pm
Two comm sats have antennas that cover the same footprint.  Both provide the same power level to the receivers within the footprint.  One comm sat is in LEO, the other is in GEO, 100x as far.

Do you think the GEO sat transmitter needs to operate at:

A) 100^2=10,000x as much power
B) 100x as much power
C) 1x as much power

(A), assuming same directivity etc.  If a method is to give very different result, I'd say the experiment needs to show clearly how the method's power density doesn't follow 1/r^2 in the far field (not near field).

Read the question again.  "Same footprint".   

The minimal footprint is dictated by many considerations, such as diffraction limit, power density, etc.

The assumption is always that a receiver is built that is large enough to contain the transmission beam.  System parameters are chosen so that this is practical, or else the system is a non-starter.

You posted a "riddle".  Well, that's the answer as I know it.  Now you should answer your riddle here yourself, quantitatively, with explicit reasoning.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 06:56 pm
Two comm sats have antennas that cover the same footprint.  Both provide the same power level to the receivers within the footprint.  One comm sat is in LEO, the other is in GEO, 100x as far.

Do you think the GEO sat transmitter needs to operate at:

A) 100^2=10,000x as much power
B) 100x as much power
C) 1x as much power

(A), assuming same directivity etc.  If a method is to give very different result, I'd say the experiment needs to show clearly how the method's power density doesn't follow 1/r^2 in the far field (not near field).

Read the question again.  "Same footprint".   

The minimal footprint is dictated by many considerations, such as diffraction limit, power density, etc.

The assumption is always that a receiver is built that is large enough to contain the transmission beam.  System parameters are chosen so that this is practical, or else the system is a non-starter.

You posted a "riddle".  Well, that's the answer as I know it.  Now you should answer your riddle here yourself, quantitatively, with explicit reasoning.
C, because the power level the receivers see is simply the transmitter power divided by the footprint, and it doesn't matter how far the transmitter is.

Think about it this way:  A 1 MWatt transmitter is covering 1E6 square meters.  What power levels do the receivers see?  1 Watt/m2, and the distance to the transmitter never entered the calculation.



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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: Semmel on 10/15/2018 07:21 pm
You posted a "riddle".  Well, that's the answer as I know it.  Now you should answer your riddle here yourself, quantitatively, with explicit reasoning.
C, because the power level the receivers see is simply the transmitter power divided by the footprint, and it doesn't matter how far the transmitter is.

Think about it this way:  A 1 MWatt transmitter is covering 1E6 square meters.  What power levels do the receivers see?  1 Watt/m2, and the distance to the transmitter never entered the calculation.

True, if the receiver is close compared to the diameter of the transmitter. Once the distance is many times larger than the diameter of the transmitter, the 1/r^2 law applied. You cannot have a perfectly parallel beam. A laser pointer (used for presentations) has a diameter of about 100m at ISS levels. There was an experiment not long ago which played with that. You can approximate that with complex gaussian beams if you want. Its pretty close to reality.

https://en.wikipedia.org/wiki/Gaussian_beam

See especially graphic

https://upload.wikimedia.org/wikipedia/commons/5/53/GaussianBeamWaist.svg

As long as you are close to the waist, as in your example, the power per unit area is roughly constant. As soon as you go farther away, the beam opens up. Its an approximation but a good proxy to visualize the the effect. And the opening angle is both waist diameter and wavelength dependent, just as one would expect for beam power transmission.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 08:05 pm
You posted a "riddle".  Well, that's the answer as I know it.  Now you should answer your riddle here yourself, quantitatively, with explicit reasoning.
C, because the power level the receivers see is simply the transmitter power divided by the footprint, and it doesn't matter how far the transmitter is.

Think about it this way:  A 1 MWatt transmitter is covering 1E6 square meters.  What power levels do the receivers see?  1 Watt/m2, and the distance to the transmitter never entered the calculation.

True, if the receiver is close compared to the diameter of the transmitter. Once the distance is many times larger than the diameter of the transmitter, the 1/r^2 law applied. You cannot have a perfectly parallel beam. A laser pointer (used for presentations) has a diameter of about 100m at ISS levels. There was an experiment not long ago which played with that. You can approximate that with complex gaussian beams if you want. Its pretty close to reality.

https://en.wikipedia.org/wiki/Gaussian_beam

See especially graphic

https://upload.wikimedia.org/wikipedia/commons/5/53/GaussianBeamWaist.svg

As long as you are close to the waist, as in your example, the power per unit area is roughly constant. As soon as you go farther away, the beam opens up. Its an approximation but a good proxy to visualize the the effect. And the opening angle is both waist diameter and wavelength dependent, just as one would expect for beam power transmission.
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.


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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: Semmel on 10/15/2018 09:46 pm
You posted a "riddle".  Well, that's the answer as I know it.  Now you should answer your riddle here yourself, quantitatively, with explicit reasoning.
C, because the power level the receivers see is simply the transmitter power divided by the footprint, and it doesn't matter how far the transmitter is.

Think about it this way:  A 1 MWatt transmitter is covering 1E6 square meters.  What power levels do the receivers see?  1 Watt/m2, and the distance to the transmitter never entered the calculation.

True, if the receiver is close compared to the diameter of the transmitter. Once the distance is many times larger than the diameter of the transmitter, the 1/r^2 law applied. You cannot have a perfectly parallel beam. A laser pointer (used for presentations) has a diameter of about 100m at ISS levels. There was an experiment not long ago which played with that. You can approximate that with complex gaussian beams if you want. Its pretty close to reality.

https://en.wikipedia.org/wiki/Gaussian_beam

See especially graphic

https://upload.wikimedia.org/wikipedia/commons/5/53/GaussianBeamWaist.svg

As long as you are close to the waist, as in your example, the power per unit area is roughly constant. As soon as you go farther away, the beam opens up. Its an approximation but a good proxy to visualize the the effect. And the opening angle is both waist diameter and wavelength dependent, just as one would expect for beam power transmission.
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.


-----
ABCD: Always Be Counting Down

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/15/2018 10:17 pm
Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.
The question was not a semantic one, it was clearly aimed to see if a poster had a very, very basic understanding of the subject.
If you are claiming to understand SPS and do not understand 1/r^2 does not usually simply apply to losses, you have just failed.

This is not a subtle trick question, it is fundamental to the very basics of SPS, nobody ever proposes power transmission in modes which throw away all of the power, which is why you beam it, and when you beam it, 1/r^2 does not simply apply, and may often be irrelevant.
It is a misunderstanding on the level of someone who seriously proposes replacing methalox with a water bottle rocket.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 10:23 pm
You posted a "riddle".  Well, that's the answer as I know it.  Now you should answer your riddle here yourself, quantitatively, with explicit reasoning.
C, because the power level the receivers see is simply the transmitter power divided by the footprint, and it doesn't matter how far the transmitter is.

Think about it this way:  A 1 MWatt transmitter is covering 1E6 square meters.  What power levels do the receivers see?  1 Watt/m2, and the distance to the transmitter never entered the calculation.

True, if the receiver is close compared to the diameter of the transmitter. Once the distance is many times larger than the diameter of the transmitter, the 1/r^2 law applied. You cannot have a perfectly parallel beam. A laser pointer (used for presentations) has a diameter of about 100m at ISS levels. There was an experiment not long ago which played with that. You can approximate that with complex gaussian beams if you want. Its pretty close to reality.

https://en.wikipedia.org/wiki/Gaussian_beam

See especially graphic

https://upload.wikimedia.org/wikipedia/commons/5/53/GaussianBeamWaist.svg

As long as you are close to the waist, as in your example, the power per unit area is roughly constant. As soon as you go farther away, the beam opens up. Its an approximation but a good proxy to visualize the the effect. And the opening angle is both waist diameter and wavelength dependent, just as one would expect for beam power transmission.
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.


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ABCD: Always Be Counting Down

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.
No, I'm talking about any size receiver.

If you're using mm wave, you can do 100m to 100m.

If 1um NIR laser, 1 m to 10 m.  (All very roughly).

Those are dictated by diffraction limits

Neither of these sizes are giant.  In the case of laser you'll probably open up the beam anyway.

The power transferred is not affected by range.  If you could magically bring the satellite closer, all you'll do is open up the beam so you don't punch holes in the receiver.

The claim that SSP loses efficiency because of range and 1/r2, which is what I'm arguing against, is just wrong.

SSp loses efficiency because of a bunch of other things but I'm getting tired of re-explaining...  Br back tomorrow.

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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: DAZ on 10/15/2018 10:52 pm
Present discussion aside, Professional Engineers have examined the subject of solar power stations extensively. The consensus has been that they are not only possible but practical. Practicality being limited by launch costs. The real discussion of their use on Earth mostly revolves around whether or not they are more cost-effective then just ground-based systems. Space solar power stations receive power almost continuously 24 hours a day while ground stations need to have battery backups or other types of systems to supplement their power during evening hours.

They do have one significant advantage for there use on Earth. As the cost of the receivers is nominal compared to the cost of the entire system you can have multiple receivers in different Geographic locations. You could then beam the power to these locations that are more in need of it depending on local usage. They can effectively follow the sun on the ground.  These locations could even be small out of the way Villages that are under supported by other power means.

There used on Mars, when combined with solar electric Tugs there is a possible multiplier Factor here. You can launch a solar tug at almost any time and make better use of your cargo ships. The tugs would then spiral out and depart at the optimum time to travel to Mars. This greatly increases deficiency of your earth-based launch system. Once the tugs arrive at Mars having already accomplished one task of delivered their cargo they could then be combined and used as a solar electric power station for Mars. Again like on Earth they could thin being their power two different places on Mars independent of where the sun is on Mars. This would greatly increase the efficiency of the ground stations as they would not need to have battery backups to keep everything running at full power during the night hours.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/15/2018 11:12 pm
There used on Mars, when combined with solar electric Tugs there is a possible multiplier Factor here. You can launch a solar tug at almost any time and make better use of your cargo ships. The tugs would then spiral out and depart at the optimum time to travel to Mars. This greatly increases deficiency of your earth-based launch system.
Another possible great benefit of martian SPS would be if ice deposits were found on Phobos or Deimos.
This means you get a large efficiency gain from the rocket equation for fuel used for shuttles from hohmann orbits or launching to earth or Mars.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/15/2018 11:43 pm
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/15/2018 11:57 pm
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)

Facepalm.

People think that physics and engineering are about memorizing equations. They even bring cheat sheets to tests, but still fail to solve the problems. The trick is how to apply the equations to the problem at hand in a sensible way, and you are failing at that.

The existence of the inverse square law in general, and the presence of the 1/r2 term in a formula you pulled out of a book in particular, do not argue one iota towards your case.  You're not applying the equation correctly.   r is not an independent variable in this discussion, and so showing an r^2 term in the denominator means squat.

I don't know how to explain it to you though, so I'll leave it at that.
Title: Re: Power options for a Mars settlement
Post by: Lemurion on 10/16/2018 12:31 am
The whole point with SSP is that while you definitely get less power than you do from surface solar, you do get power when you don't get surface solar. The question then becomes how much more is that power worth to the Martian infrastructure.

So what you really have to ask is whether SSP is going to cost you more than either not having that power available when surface solar is unavailable or whatever power alternative you choose to install. I personally don't think it's a good choice for the first few years, but I can see it being useful sometime down the line purely because it does offer continuous power. In fact I think it's about the only reasonable option for continuous power at Mars.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/16/2018 12:48 am
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)

Facepalm.

People think that physics and engineering are about memorizing equations. They even bring cheat sheets to tests, but still fail to solve the problems. The trick is how to apply the equations to the problem at hand in a sensible way, and you are failing at that.

The existence of the inverse square law in general, and the presence of the 1/r2 term in a formula you pulled out of a book in particular, do not argue one iota towards your case.  You're not applying the equation correctly.   r is not an independent variable in this discussion, and so showing an r^2 term in the denominator means squat.

I don't know how to explain it to you though, so I'll leave it at that.

A worked example illustrates the Friis formula.  Ex. 16.6.1. (http://eceweb1.rutgers.edu/~orfanidi/ewa/ch16.pdf)  It's a good basis for theme-and-variation, and a reference for those who wonder if some SSP config can get around Friis to compete with martian surface PV.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 10/16/2018 12:54 am
The inverse square law does mean that power goes down 1/r^2 if you keep the transmitter and/or receiver the same size (and start out with it right-sized).

But the other direction doesn't help much, either. Having the receiver (or transmitter) size proportional to r^2 is hardly great, either. The "just chicken wire mesh" thing is a lie. It's basically the same as installing a solar array (except the added complication of needing a filled array), so at some small scale, you're way better off just installing a solar array. It's only at large scale (i.e. gigawatts, or AT LEAST hundreds of megawatts) do you even approach ground based solar. Even including reduction in power from dust storms.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/16/2018 12:56 am
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)

Facepalm.

People think that physics and engineering are about memorizing equations. They even bring cheat sheets to tests, but still fail to solve the problems. The trick is how to apply the equations to the problem at hand in a sensible way, and you are failing at that.

The existence of the inverse square law in general, and the presence of the 1/r2 term in a formula you pulled out of a book in particular, do not argue one iota towards your case.  You're not applying the equation correctly.   r is not an independent variable in this discussion, and so showing an r^2 term in the denominator means squat.

I don't know how to explain it to you though, so I'll leave it at that.

A worked example illustrates the Friis formula.  Ex. 16.6.1. (http://eceweb1.rutgers.edu/~orfanidi/ewa/ch16.pdf)  It's a good basis for theme-and-variation, and a reference for those who wonder if some SSP config can get around Friis to compete with martian surface PV.

Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)

Facepalm.

People think that physics and engineering are about memorizing equations. They even bring cheat sheets to tests, but still fail to solve the problems. The trick is how to apply the equations to the problem at hand in a sensible way, and you are failing at that.

The existence of the inverse square law in general, and the presence of the 1/r2 term in a formula you pulled out of a book in particular, do not argue one iota towards your case.  You're not applying the equation correctly.   r is not an independent variable in this discussion, and so showing an r^2 term in the denominator means squat.

I don't know how to explain it to you though, so I'll leave it at that.

A worked example illustrates the Friis formula.  Ex. 16.6.1. (http://eceweb1.rutgers.edu/~orfanidi/ewa/ch16.pdf)  It's a good basis for theme-and-variation, and a reference for those who wonder if some SSP config can get around Friis to compete with martian surface PV.

There is no reason to "get around Friis", because nothing about that equation supports your reasoning.



-----
ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: LMT on 10/16/2018 01:42 am
The inverse square law does mean that power goes down 1/r^2 if you keep the transmitter and/or receiver the same size (and start out with it right-sized).

But the other direction doesn't help much, either. Having the receiver (or transmitter) size proportional to r^2 is hardly great, either. The "just chicken wire mesh" thing is a lie. It's basically the same as installing a solar array (except the added complication of needing a filled array), so at some small scale, you're way better off just installing a solar array. It's only at large scale (i.e. gigawatts, or AT LEAST hundreds of megawatts) do you even approach ground based solar. Even including reduction in power from dust storms.

Or apply that system mass instead toward scale-up of your surface PV farm, and never look back.

Free real estate, and microwave conversion and transmission losses = 0.0.  It's the SSP dream.   ;)
Title: Re: Power options for a Mars settlement
Post by: Mongo62 on 10/16/2018 03:16 am
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)

This equation is completely irrelevant to what we are talking about. It assumes that the receiving antenna is smaller than the beam size of the microwave (or optical) beam -- in which case the receiving antenna would indeed be subject to the inverse square rule. But in reality it would be the same size or slightly larger than the beam size, so that it captures all of the available beam power and the inverse square rule does not apply. As numerous posts have stated, at 1mm microwave wavelength, a 100m transmitting antenna in an areocentric orbit around Mars can form a microwave beam that can have 100% coverage using a 100m wide (or a bit wider, say 120m) receiving antenna on Mars.

I strongly suspect that the mass of such an SPS plus transmitting antenna, delivered to areocentric orbit, and the mass of the receiving antenna plus power conditioning equipment, delivered to the surface of Mars, would be considerably less than the mass of a solar power system plus energy storage with the same continuous power production, all delivered to the surface of Mars.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/16/2018 03:40 am
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)

This equation is completely irrelevant to what we are talking about. It assumes that the receiving antenna is smaller than the beam size of the microwave (or optical) beam -- in which case the receiving antenna would indeed be subject to the inverse square rule. But in reality it would be the same size or slightly larger than the beam size, so that it captures all of the available beam power and the inverse square rule does not apply. As numerous posts have stated, at 1mm microwave wavelength, a 100m transmitting antenna in an areocentric orbit around Mars can form a microwave beam that can have 100% coverage using a 100m wide (or a bit wider, say 120m) receiving antenna on Mars.

It's nothing to assert such a thing; you need to calculate instead.  e.g., alter reference Ex. 16.6.1. (http://eceweb1.rutgers.edu/~orfanidi/ewa/ch16.pdf) to demonstrate, if you can.  You might cross-check with meekGee, too.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/16/2018 03:54 am
Nobody said the beam is parallel...  I said same power, and same footprint.

When talking about a comm sat the footprint will be much larger than the sat.

For SSP, it depends. 

The point is, as long as you can match the spot size to the receiver, getting closer (for example) wont increase the amount of power received.

In the multiple choice question above, the answer is C.

Ohhh you are talking about really oversized receivers. Come on, we dont need this type of tricks here. We want to figure out how to power the *** colony, not play semantics on a multiple choice question.

And to quantify SSP transmission we'd use the far-field Friis formula (https://www.electronicdesign.com/energy/what-s-difference-between-em-near-field-and-far-field), which includes the inverse square term of course.  No combination of Friis formula terms makes SSP competitive against martian surface solar.  Any experiment claiming otherwise has to get past Friis and the inverse square first, with reasoning, and quantitatively.  Absent such experiment, there's no argument; just "semantics", etc. 

(http://cdn.everythingrf.com/live/friisformula4.png)

This equation is completely irrelevant to what we are talking about. It assumes that the receiving antenna is smaller than the beam size of the microwave (or optical) beam -- in which case the receiving antenna would indeed be subject to the inverse square rule. But in reality it would be the same size or slightly larger than the beam size, so that it captures all of the available beam power and the inverse square rule does not apply. As numerous posts have stated, at 1mm microwave wavelength, a 100m transmitting antenna in an areocentric orbit around Mars can form a microwave beam that can have 100% coverage using a 100m wide (or a bit wider, say 120m) receiving antenna on Mars.

It's nothing to assert such a thing; you need to calculate instead.  e.g., alter reference Ex. 16.6.1. (http://eceweb1.rutgers.edu/~orfanidi/ewa/ch16.pdf) to demonstrate, if you can.  You might cross-check with meekGee, too.

MeekGee was telling you the same thing.  The equation does not support your cause.   Shrug.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 10/16/2018 05:48 am
Ok, I understand now. You are right, distance das not matter as long as you collect the entire beam at the surface. And you would design it to be that way. Question is, is the development, deployment and running cost less than ground solar? Intuitively I would say no. Also it is undeniably more complicated than ground solar, which is a big minus. I guess we can file solar sat power as technically possible but interior to ground solar power. Unless you have a strong argument to the contrary without cherry picking.. would be nice to get back to the other options.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/16/2018 07:02 am
Ok, I understand now. You are right, distance das not matter as long as you collect the entire beam at the surface. And you would design it to be that way. Question is, is the development, deployment and running cost less than ground solar? Intuitively I would say no. Also it is undeniably more complicated than ground solar, which is a big minus. I guess we can file solar sat power as technically possible but interior to ground solar power. Unless you have a strong argument to the contrary without cherry picking.. would be nice to get back to the other options.
Yup, agreed.  Even in the Mars scenario, where things are aligned pretty well for SSP, I'm pretty sure it still loses out - mostly because of the staggering system complexity.



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ABCD: Always Be Counting Down

Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/16/2018 10:11 am
Ok, I understand now. You are right, distance das not matter as long as you collect the entire beam at the surface. And you would design it to be that way. Question is, is the development, deployment and running cost less than ground solar? Intuitively I would say no. Also it is undeniably more complicated than ground solar, which is a big minus. I guess we can file solar sat power as technically possible but interior to ground solar power. Unless you have a strong argument to the contrary without cherry picking.. would be nice to get back to the other options.
Yup, agreed.  Even in the Mars scenario, where things are aligned pretty well for SSP, I'm pretty sure it still loses out - mostly because of the staggering system complexity.

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ABCD: Always Be Counting Down

I'm not sure it doesn't eventually play a useful role - a SPS doing multiple duty for additional night power, and providing power to vehicles near Mars to do large electric burns may be nice indeed. (or even being a SEP tug).
But, if BFS gets even close to its design costs, near-term it doesn't make any sense - even if you assume panels setup by hand are the best way to put solar down as a lower limit on your cost, they seem to beat it considerably in cost, never mind complexity.

edit/Lar: Fix quotes
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 10/16/2018 10:26 am
Wait...  At same velocity, you still get linear dependency to density.

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ABCD: Always Be Counting Down



Yep. But the v^3 of the wind power equation simply means the same wind has to blow a little (~4x) faster to get the same power as on Earth. It's limited, but winds on Mars seem to be fairly constant.

(https://www.windpowerengineering.com/wp-content/uploads/2014/12/Wind-Power-calculation.jpg)

The k constant is for Imperial/metric conversion and can be ignored.
4x as fast is not "a little".  30 MPH is a nice wind.  120 is a major hurricane.

Is there information that Mars has winds that are consistent over the day and are 4x as fast?

If it does, that would bring it back to Earth levels - which we xan discuss separately. 

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ABCD: Always Be Counting Down



The linked article which sparked this discussion assumed a 14m/s windspeed just off the ground. This is in good agreement with dust devil horizontal speed measurements and seems to fit with discarded parachute trajectories. Dust devils are a proxy for ambient wind speeds.

Dust devil horizontal speed measurement:
http://www.lmd.jussieu.fr/~aslmd/pub/REF/2014Icar..227....8R.pdf
Weibull distribution for Curiosity windspeeds: http://www-mars.lmd.jussieu.fr/granada2017/abstracts/viudez-moreiras_granada2017.pdf
Wind speed estimate of discarded heat shield/parachute:
https://meetingorganizer.copernicus.org/EPSC2017/EPSC2017-490.pdf
HIRISE dust devil windspeed measurement:
https://arxiv.org/pdf/1301.6130.pdf

Note for the dust devils that ambient winds appear to be "only" 12m/s at 10m off the ground, with 3/4 of the measured speeds being above 15m/s. The HIRISE analysis indicates faster ambient winds, which are in agreement with the Mars Climate Database (generated by the Global Climate Model).

Dust devil horizontal speed relation to ambient wind speeds:
http://oro.open.ac.uk/34313/
Dust devil speed is in agreement with wind speeds a few tens of metres above the surface, making a good proxy.

In any case, we will know a lot more once ExoMars lands, with its MARBL high altitude wind speed measurement system.

Wind won't be the only power option for Mars - but it can certainly complement solar even so due to advantages offered by reduced wind pressure and gravity. After all, we are discussing solar where the solar constant is less than 1/2 of Earth's.
14 m/s, divided by 4, is what - less than 8 mph.  You're not making power out of that...

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ABCD: Always Be Counting Down



No, you're not getting that much electricity of an equivalent 3 or 4m/s which is around the cut-in speed for wind turbines on Earth. However at that speed, Semmel's article showed that a light (275kg) but still quite large giromill produced 2.1kW. Hardly a nuclear plant but that's not the point of wind:

You're designing for something to generate power when the sun isn't shining, and most critically extra power during a dust storm (and wind speeds are on the order of 20-25m/s at surface, and higher at the turbine height). The 22-25m/s that LMT quoted as feasible was for a study that examined wind power usefulness for a manned expedition as an emergency power source during dust storms. Weight-for-weight feasibility vs solar panels and fuel cells needs wind speeds of 28m/s and that would require special siting for slope winds. What LMT also neglected to mention was that 22-25m/s is required for one hour per day during a dust storm.

Mesoscale modeling shows strong, steady winds on the southwestern rim of Gale Crater (ho ho).
https://aeolisresearch.com/papers/newmanIC2017.pdf

Which is understandable given that there's a good 5000m difference in elevation between the northern floor and the southwestern rim. It's also faaaaar. 100km or so, so something you'd only do for a settlement, if you used Curiosity as the site of your Mars colony.

So it's an option. It's too heavy to ship from Earth as a core settlement power except if you site the base near strong winds, but attractive for day-round non-nuclear power and a fairly simple technology to augment with local resources.

Whether or not it becomes a more significant contributor to the settlement depends on economics: base location, manufacturing technologies, maintenance requirements and so on.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/16/2018 11:48 am
Ok, I understand now. You are right, distance das not matter as long as you collect the entire beam at the surface.

And in the far field, as here, the beam diverges as a point source, power density falling with 1/r^2; hence an unavoidably large and massive collector and other large system masses, for uncompetitive SSP.

Yup, agreed.  Even in the Mars scenario, where things are aligned pretty well for SSP, I'm pretty sure it still loses out - mostly because of the staggering system complexity.

Make it as simple as you like, for simple power calc.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/16/2018 03:09 pm
Mars SSP Design

Further example:

The 500 t areostationary design of Cougnet et al. 2004 delivers 100 kWe to a Mars base.

That mass, used instead as QD PV farm, delivers up to 3.3 GWe to the base: 33,000x SSP performance.  Daily energy delivery is ~ 8,000x SSP performance.

Refs.

Cougnet, C., Sein, E., Celeste, A., & Summerer, L. (2004, December). Solar power satellites for space exploration and applications. In Solar Power from Space-SPS'04 (Vol. 567, p. 151).
Title: Re: Power options for a Mars settlement
Post by: Lar on 10/16/2018 05:16 pm
The argument is stale. Move on.
Title: Re: Power options for a Mars settlement
Post by: Mongo62 on 10/16/2018 05:28 pm
Mars SSP Design

Further example:

The 500 t areostationary design of Cougnet et al. 2004 delivers 100 kWe to a Mars base.

That mass, used instead as QD PV farm, delivers up to 3.3 GWe to the base: 33,000x SSP performance.  Daily energy delivery is ~ 8,000x SSP performance.

Refs.

Cougnet, C., Sein, E., Celeste, A., & Summerer, L. (2004, December). Solar power satellites for space exploration and applications. In Solar Power from Space-SPS'04 (Vol. 567, p. 151).

I looked at the referenced report.

It provides several options using RF and laser power transmission. You selected the lowest-efficiency option, with an RF transmission antenna that is much too small to provide an adequately narrow beam. The receiving antenna only covers a small fraction of the beam area. Total system power efficiency is 0.51% in the option you chose. Also the actual SPS mass is 41t, with most of the other 459t apparently being the vehicle to get it into Mars orbit.

This paper was published in 2004, and I am sure that efficiencies would be substantially greater if the SPS system were to be designed today.
Title: Re: Power options for a Mars settlement
Post by: Lemurion on 10/16/2018 06:59 pm
Personally I think it might be a good idea to put something of a timeline or at least a schedule on the various options.

From what I can tell I think we're likely looking at something like this:

Phase 1: Solar/Batteries. This is what SpaceX already has and is comfortable using. They can leverage Tesla expertise and work from there.
Phase 2: Wind/Nuclear. Any settlement is going to need something for power during dust storms and these seem to be the best developed options. I think the combination of mass and politics will give wind an advantage here but I think nuclear is always going to be on the table for discussion whether it's actually deployed or not.
Phase 3: SSP. This may actually precede nuclear but I'm putting it in the third phase because it's the only system that has never been deployed at Earth.

Other systems may follow but I think these four are the most likely options.
Title: Re: Power options for a Mars settlement
Post by: deruch on 10/16/2018 11:42 pm
Personally I think it might be a good idea to put something of a timeline or at least a schedule on the various options.

From what I can tell I think we're likely looking at something like this:

Phase 1: Solar/Batteries. This is what SpaceX already has and is comfortable using. They can leverage Tesla expertise and work from there.
Phase 2: Wind/Nuclear. Any settlement is going to need something for power during dust storms and these seem to be the best developed options. I think the combination of mass and politics will give wind an advantage here but I think nuclear is always going to be on the table for discussion whether it's actually deployed or not.
Phase 3: SSP. This may actually precede nuclear but I'm putting it in the third phase because it's the only system that has never been deployed at Earth.

Other systems may follow but I think these four are the most likely options.

Ideally you want systems that either can't really fail (e.g. nuclear), can still operate at a lower effective level even with failures (e.g. PV+storage), or are "easily" repaired locally (wind?).  What does a settlement that is using SSP do if their beaming satellite fails?  Do they have the industrial means to build and launch a replacement?  Or do they have to rely on Earth to supply them?  Are they stockpiling satellites?
Title: Re: Power options for a Mars settlement
Post by: Lar on 10/17/2018 01:25 am
Personally I think it might be a good idea to put something of a timeline or at least a schedule on the various options.

From what I can tell I think we're likely looking at something like this:

Phase 1: Solar/Batteries. This is what SpaceX already has and is comfortable using. They can leverage Tesla expertise and work from there.
Phase 2: Wind/Nuclear. Any settlement is going to need something for power during dust storms and these seem to be the best developed options. I think the combination of mass and politics will give wind an advantage here but I think nuclear is always going to be on the table for discussion whether it's actually deployed or not.
Phase 3: SSP. This may actually precede nuclear but I'm putting it in the third phase because it's the only system that has never been deployed at Earth.

Other systems may follow but I think these four are the most likely options.

Ideally you want systems that either can't really fail (e.g. nuclear), can still operate at a lower effective level even with failures (e.g. PV+storage), or are "easily" repaired locally (wind?).  What does a settlement that is using SSP do if their beaming satellite fails?  Do they have the industrial means to build and launch a replacement?  Or do they have to rely on Earth to supply them?  Are they stockpiling satellites?

see this excellent post by Paul451 (and some of the posts near it) in the Homesteading thread

https://forum.nasaspaceflight.com/index.php?topic=41937.msg1866944#msg1866944

By the time you get to the bottom of that ISRU list and need the massive power that an SSPS brings you, yes, you do have the industrial means to build 99.9% (by mass) of the birds with only maybe the control electronics imported, and you have a fleet of BFS2s maintained locally and possibly even built locally (except for the control electronics) to launch replacements with.

One BFS2 can no doubt bring you enough control electronics for the next 100 years production of SSP and BFS2s (not that you would want to.. obsolescence is a thing) so stockpiling those is not a problem
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 10/17/2018 01:24 pm
One quick question.
So what is the percent power output of a solar array in worst dust storm conditions.
Given the huge size of array to power the ISRU propellant production. It seems to me that the array will enough for basic stuff even in the worst dust storm conditions as long as propellant production can be shutdown.

The size of batteries is always related to the size of demand that can't get reduced.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/17/2018 02:35 pm
One quick question.
So what is the percent power output of a solar array in worst dust storm conditions.
Given the huge size of array to power the ISRU propellant production. It seems to me that the array will enough for basic stuff even in the worst dust storm conditions as long as propellant production can be shutdown.

The size of batteries is always related to the size of demand that can't get reduced.
Worst dust storm case is well under ten percent for extended periods.
And yes, 'hotel load' can be dramatically lower than ISRU.

The size of batteries may be related to maintaining full power overnight, not hotel load, if it is desired to run the ISRU or other power expensive equipment overnight.

Internal combustion engines are at least 25% efficient burning methalox, meaning your ISRU tanks are massive batteries.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 10/17/2018 03:43 pm
One quick question.
So what is the percent power output of a solar array in worst dust storm conditions.
Given the huge size of array to power the ISRU propellant production. It seems to me that the array will enough for basic stuff even in the worst dust storm conditions as long as propellant production can be shutdown.

The size of batteries is always related to the size of demand that can't get reduced.
Worst dust storm case is well under ten percent for extended periods.
And yes, 'hotel load' can be dramatically lower than ISRU.

The size of batteries may be related to maintaining full power overnight, not hotel load, if it is desired to run the ISRU or other power expensive equipment overnight.

Internal combustion engines are at least 25% efficient burning methalox, meaning your ISRU tanks are massive batteries.
So about ~5% as a rough guide for planning?
I did a little googling and couldn't find anything very definitive.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/17/2018 03:57 pm
One quick question.
So what is the percent power output of a solar array in worst dust storm conditions.
Given the huge size of array to power the ISRU propellant production. It seems to me that the array will enough for basic stuff even in the worst dust storm conditions as long as propellant production can be shutdown.

The size of batteries is always related to the size of demand that can't get reduced.
Worst dust storm case is well under ten percent for extended periods.
And yes, 'hotel load' can be dramatically lower than ISRU.

The size of batteries may be related to maintaining full power overnight, not hotel load, if it is desired to run the ISRU or other power expensive equipment overnight.

Internal combustion engines are at least 25% efficient burning methalox, meaning your ISRU tanks are massive batteries.

That bit about using the ISRU tanks is what makes all the contingency talk moot.

Whatever the steady state power source is, there's plenty stored power for when it is down.  It can be an ICE, or it can even be a turbine, and it will provide both power and heat.

The focus should be about the primary source.  How to get the most Watt-hours per year, for the least amount of mass transported from Earth.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 10/17/2018 04:39 pm
Personally I think it might be a good idea to put something of a timeline or at least a schedule on the various options.

From what I can tell I think we're likely looking at something like this:

Phase 1: Solar/Batteries. This is what SpaceX already has and is comfortable using. They can leverage Tesla expertise and work from there.
Phase 2: Wind/Nuclear. Any settlement is going to need something for power during dust storms and these seem to be the best developed options. I think the combination of mass and politics will give wind an advantage here but I think nuclear is always going to be on the table for discussion whether it's actually deployed or not.
Phase 3: SSP. This may actually precede nuclear but I'm putting it in the third phase because it's the only system that has never been deployed at Earth.

Other systems may follow but I think these four are the most likely options.

That makes sense. It is also tied to how or whether SPS works out on Earth. Once an SPS is built, it would be relatively easy to attach electric thrusters and move it from Earth orbit to Mars orbit (or, if built from Phobos material, the opposite).

So if SPS works for Earth, it will be a default option for Mars. If nuclear and ground based solar work out better on Earth, then they will work out better on Mars.

(Though there are other factors - including the latitude of the base - SPS on Earth would be most useful for high latitude countries where ground solar is too intermittent. Where would the Mars base be?)
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/17/2018 04:43 pm
Mars SSP Design

Further example:

The 500 t areostationary design of Cougnet et al. 2004 delivers 100 kWe to a Mars base.

That mass, used instead as QD PV farm, delivers up to 3.3 GWe to the base: 33,000x SSP performance.  Daily energy delivery is ~ 8,000x SSP performance.

Refs.

Cougnet, C., Sein, E., Celeste, A., & Summerer, L. (2004, December). Solar power satellites for space exploration and applications. In Solar Power from Space-SPS'04 (Vol. 567, p. 151).

I looked at the referenced report.

It provides several options using RF and laser power transmission. You selected the lowest-efficiency option, with an RF transmission antenna that is much too small to provide an adequately narrow beam. The receiving antenna only covers a small fraction of the beam area. Total system power efficiency is 0.51% in the option you chose. Also the actual SPS mass is 41t, with most of the other 459t apparently being the vehicle to get it into Mars orbit.

re mass.  "41 t" is a completely different scenario: a rover.   ::)   Section 4.3 is the Mars base.  500 t covers power generation, transmission and reception, plus unspecified SEP propellant, for efficient Mars transfer and presumably station-keeping.  No additional vehicle.  It's just a big system, unavoidably.

re antenna sizing.  They sized to optimize.  Rectenna type and size "minimize the on-board projecting antenna sizing".  They analyzed the trade-offs.  You haven't.

You selected the lowest-efficiency option

They chose microwave over laser for the stated reasons:  "size constraints on the receiver can be somewhat relaxed for this application while laser transmission is still penalised in case of dust storms".

This paper was published in 2004, and I am sure that efficiencies would be substantially greater if the SPS system were to be designed today.

When an improvement bumps up SSP specific power by four orders of magnitude, it'll be in the ballpark of competitiveness - assuming PV specific power hasn't bumped up too.

Til then the topic is quite stale, yes, and may well be dropped.  Really any advocacy of a power idea that mocks the basic math grows stale quickly.
Title: Re: Power options for a Mars settlement
Post by: Mongo62 on 10/17/2018 10:13 pm
Space Based Solar Power is for Mars (https://www.researchgate.net/publication/283152553_Space_Based_Solar_Power_is_for_Mars)

Space Based Solar Power (SBSP) was first proposed by Isaac Asimov in 1941 and has been under active research since the 1970’s. While solar irradiation is around 30% higher in orbit, the main advantage of SBSP is the nearly 100% duty cycle, giving a factor of 2 to 3 improvement over ground based solar power under the most ideal surface conditions, but closer to 10 to 100 improvement compared to more realistic surface solar collection conditions. Elon Musk famously proclaimed SBSP dead with the statement “You’d have to convert photon to electron to photon back to electron. What’s the conversion rate?” However, even with conversion efficiency as bad as 10% in those last two steps, SBSP still has a small advantage in power production per square meter. The biggest obstacle to technology adoption is actually the cost of launch, which can be many thousands of Euros per kilogram, and the very expensive design, development and verification campaigns involved in space missions, multiplying the cost of power production by many thousands for modern low cost solar panels. Additionally, many unresolved issues of interference with Earth communication systems exist. On the other hand, on Mars, all of these disadvantages are turned on their head. Landing equipment safely on Mars is extremely difficult and expensive. Every additional kilogram to be landed on Mars requires extra fuel which requires extra fuel for the Earth launch. By modularizing the mission into in-space power production and on-surface power consumption, the cost of the mission is significantly reduced as is mission risk. Additionally, the major problems of dust and frost collection on rover solar panels are eliminated and the possibility to maintain limited operations during the Martian winter becomes plausible. Since rectenna have far less mass than any form of on-surface electrical production, power consumption from roving would be reduced. Since solar panels in orbit can last a decade or more, SBSP units could serve multiple missions on Mars over their lifetime, with surplus power sold to third parties. Finally, the SBSP units can serve dual functions as data up-links and navigation systems. Currently, the FCC places no restrictions on bandwidth usage on Mars, meaning that Mars is the perfect location to prove/showcase the major economic and engineering advantages this technology has on planetary bodies other than the Earth. It is not time to stab SBSP in the heart, but to move the focus to another world.



Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 10/17/2018 10:53 pm
SSP sucks for Mars settlement requirements. This shouldn’t be controversial, even if you quibble with LMT’s specifics. And it only makes any sense whatsoever at Gigawatt levels or higher. And at that point, making frames for solar cells is likely within local production capabilities, so you’re really competing with raw cells.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/18/2018 12:05 am
SSP sucks for Mars settlement requirements. This shouldn’t be controversial, even if you quibble with LMT’s specifics. And it only makes any sense whatsoever at Gigawatt levels or higher. And at that point, making frames for solar cells is likely within local production capabilities, so you’re really competing with raw cells.

Yup.  One of the stronger arguments of solar over nuclear is that it is simple and distributed.  SSP is neither, and further, it has never been done before, not in any relevant scale.

The initial metric for solar is "minimize mass of the components that are transported from Earth".
The eventual metric for solar is "minimize the amount of energy used for making a certain capacity on Mars using ISRU".

Those metrics also apply to other forms of power production such as nuclear.
Title: Re: Power options for a Mars settlement
Post by: KelvinZero on 10/18/2018 12:28 am
It was mentioned that you cannot exploit the simplistic watts/kg of thin film because of the mass of the support etc.

Does that have to be high tech? Could it just be sand rolled flat? Then your only ISRU would be a roller and filtering for the right grain size: not lumpy rocks, not dust so fine it is blown around by the mars wind -- though even that is only a problem around the edges of each strip. At the edges the roll could become plastic mesh. The holes make it lighter and tangle it in the pebbles (larger grained sand) that you lay over them.

I could imagine a robot doing this all in one pass.. Raking up the regolith, filtering into useful grainsize, laying it down, rolling it flat and dense, laying down the thin film, dribbling pebble/sand over the  mesh edges.

You do lose efficiency from tracking the sun but straight up is not too bad at the equator where apparently there are decent suspected water sources. Possibly reflectors could get some of this back? Or maybe better just to go for the low maintenance: just long flat strips with room for dusting robots to cruise up and down, blowing dust off with compressed air or brushes.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/18/2018 01:50 am
It was mentioned that you cannot exploit the simplistic watts/kg of thin film because of the mass of the support etc.

Does that have to be high tech? Could it just be sand rolled flat? Then your only ISRU would be a roller and filtering for the right grain size: not lumpy rocks, not dust so fine it is blown around by the mars wind -- though even that is only a problem around the edges of each strip. At the edges the roll could become plastic mesh. The holes make it lighter and tangle it in the pebbles (larger grained sand) that you lay over them.

I could imagine a robot doing this all in one pass.. Raking up the regolith, filtering into useful grainsize, laying it down, rolling it flat and dense, laying down the thin film, dribbling pebble/sand over the  mesh edges.

You do lose efficiency from tracking the sun but straight up is not too bad at the equator where apparently there are decent suspected water sources. Possibly reflectors could get some of this back? Or maybe better just to go for the low maintenance: just long flat strips with room for dusting robots to cruise up and down, blowing dust off with compressed air or brushes.
Aren't there grounding problems if solar cells don't have an adequate backing?
I was thinking you might send only high efficiency cells and mount them on a backing made locally with a sintered material (dust) in a magic 3D printer.  At 24+ plates per day that's a few thousand per year, so perhaps a useful area?
Title: Re: Power options for a Mars settlement
Post by: Semmel on 10/18/2018 08:44 am
How comes we are discussing about the most complex system the most? Simplicity is a huge factor in any systems where high reliability is key. SSP is just far more complex than any other method. You can't measure complexity in watts per square meter or watts per kg, but it is still a decision factor. What I am trying to say is, SSP would not be used, even if it was more efficient than ground solar. Only if there is a huge factor more, say, factor of 10 or something, it might be considered. All this talk about the details of how much mass and watts and beam diameter and all this kind of stuff is beside the point, because at best, SSP is marginally better than ground solar and not an option due to its complexity. We excluded it, lets move on.
Title: Re: Power options for a Mars settlement
Post by: KelvinZero on 10/18/2018 09:10 am
Aren't there grounding problems if solar cells don't have an adequate backing?
Do you have a link on that? Im trying to understand the difference between rolled and sintered dust in this context.

(edit: just read again.. you mean the photovoltaic material has to be sintered onto a base with the right properties, it is not just mechanical support?)

I had a look for a link but kept just finding electricians advice on grounding.. the big problem I could see is that perhaps this can't come in a roll like I imagined? Do these efficiency numbers come from super thin deposited films? (In which case I can imagine they certainly do need something like glass)
Title: Re: Power options for a Mars settlement
Post by: speedevil on 10/18/2018 10:14 am
It was mentioned that you cannot exploit the simplistic watts/kg of thin film because of the mass of the support etc.

Does that have to be high tech? Could it just be sand rolled flat?
The film in question is so ridiculously fine that it would need to be glued to a backing surface that needs to be pretty much dead flat.
It may also need a UV/dust cover layer of plastic in addition.
Some sort of mortared or epoxied sand could in principle work.

But making this sort of base is lots more complex than thicker solar panels - the semi-flexible solar panel I mentioned in the ebay thread (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512) gets 500kW average output per BFS, including an allowance for support frames.

This is with packaged for retail cells which get 50W/kg on earth (and rather less on Mars).

Bare cells, unpackaged, weigh around a tenth of this - or 7.5MW average per BFS (only during the day, the previous estimate used some of the mass for a battery for night-time usage, which isn't possible at this power).

You don't need to look at getting much more efficient than this in terms of packing, for a very simple reason.
150 tons of the cheapest 200um silicon solar cells, packed together closely already cost you enough that they cost you more than all the launches to get BFS to  Mars. (some $50M).

While there is room for improvement, if you spend more than around three times the cost of the cheapest commercial solar cells - shipped bare - you are better off just buying another BFS as it would be cheaper.

Commercially available thin film solutions are broadly in a similar mass range, before their outer coatings are applied.

The ebay thread was not to work out the optimal solution, it was to work out the stupidest commercial solution that performed reasonably, to give a backstop on costs.
If you remain with commercially available in volume components, but go with panel components, not whole panels, and accept some Martian fabrication and better prepared surfaces, it is not very hard to get ten times the average 500kW given.

Even at 'only' the 500kW average, that is each BFS landed supplying enough power to refuel two BFS per synod.
Title: Re: Power options for a Mars settlement
Post by: alexterrell on 10/19/2018 07:40 pm
How comes we are discussing about the most complex system the most? Simplicity is a huge factor in any systems where high reliability is key. SSP is just far more complex than any other method. You can't measure complexity in watts per square meter or watts per kg, but it is still a decision factor. What I am trying to say is, SSP would not be used, even if it was more efficient than ground solar. Only if there is a huge factor more, say, factor of 10 or something, it might be considered. All this talk about the details of how much mass and watts and beam diameter and all this kind of stuff is beside the point, because at best, SSP is marginally better than ground solar and not an option due to its complexity. We excluded it, lets move on.
Longer term, if SSP works for Earth (A big if, though the bare numbers, based on BFR launch costs, suggest it could), then the least complex solution for power on Mars would be to take a standard SSP station from Earth orbit to Mars orbit.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/20/2018 12:22 am
It was mentioned that you cannot exploit the simplistic watts/kg of thin film because of the mass of the support etc.

Does that have to be high tech? Could it just be sand rolled flat?
The film in question is so ridiculously fine that it would need to be glued to a backing surface that needs to be pretty much dead flat.
It may also need a UV/dust cover layer of plastic in addition.
Some sort of mortared or epoxied sand could in principle work.

But making this sort of base is lots more complex than thicker solar panels - the semi-flexible solar panel I mentioned in the ebay thread (https://forum.nasaspaceflight.com/index.php?topic=45477.msg1810512#msg1810512) gets 500kW average output per BFS, including an allowance for support frames.

This is with packaged for retail cells which get 50W/kg on earth (and rather less on Mars).

Bare cells, unpackaged, weigh around a tenth of this - or 7.5MW average per BFS (only during the day, the previous estimate used some of the mass for a battery for night-time usage, which isn't possible at this power).

You don't need to look at getting much more efficient than this in terms of packing, for a very simple reason.
150 tons of the cheapest 200um silicon solar cells, packed together closely already cost you enough that they cost you more than all the launches to get BFS to  Mars. (some $50M).

While there is room for improvement, if you spend more than around three times the cost of the cheapest commercial solar cells - shipped bare - you are better off just buying another BFS as it would be cheaper.

Commercially available thin film solutions are broadly in a similar mass range, before their outer coatings are applied.

The ebay thread was not to work out the optimal solution, it was to work out the stupidest commercial solution that performed reasonably, to give a backstop on costs.
If you remain with commercially available in volume components, but go with panel components, not whole panels, and accept some Martian fabrication and better prepared surfaces, it is not very hard to get ten times the average 500kW given.

Even at 'only' the 500kW average, that is each BFS landed supplying enough power to refuel two BFS per synod.

People miss the point of the ebay thread. 
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/20/2018 05:56 pm
The air is so thin, I doubt that wind by itself is the major factor.  I would be more concerned about surface "weathering" due to being sand-blasted by dust during storms.  I do not mean dust piling up on the surface, but a permanent scouring effect that would make the top surface less transparent.  Is there any data on that from existing missions?

Of course it would.  Even with lower density (as was pointed out in the power section), the wind has a macroscopic effect.  Foil would have to be inflated to resist that, since from a fatigue stand point, hardly anything is worse than flapping in the wind.

Still though - temperature cycles, pressures cycles, bulk motion of the inflated structure, sand abrasion - all of this will require a foil much thicker than LMT is imagining - probably by about a factor of 100....

The QD cells themselves are currently low efficiency, so unless they improve, they'll take up twice the area, and thus twice the mass of something like an Alta Devices cell.

Si cells, it depends how far they are thinned, and how heavy the substrate and structure end up being.  It'll be hard to make them negligible in mass, but give they are at 20+% efficiency, they need half the support mass that QD cells require today.
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 10/21/2018 09:23 pm
I have one of those "unisolar" solar panels out in the garage, almost 20 years old.  It uses a sprayed-on amorphous coating - in those days it was on sheet Aluminum, but needed a stiffening frame around it.  Of course on Mars the frame could be lighter.  But these days they are doing flexible versions that can withstand high winds in their roofing tile version.  Weight 1 Lb per square foot. peel-and-stick installation.   23 square feet generates 128 Watts at 24 Volts (on Earth) which is about one-third what the fancy panels will do.   Amorphous panels do not generate as much power per unit area, but have other advantages.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 10/21/2018 11:33 pm
23 square feet generates 128 Watts at 24 Volts (on Earth) which is about one-third what the fancy panels will do.   Amorphous panels do not generate as much power per unit area, but have other advantages.

Modern thin-film price-equivalent of a 15% commercial silicon panel would be around 12%. They aren't that far off.

And space-rated GaAs in thin-film runs at 28% or so. If you don't might paying extra.

[Read about this because of a comment from RobotBeat in the Settlements thread.]
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 11/07/2018 05:41 pm
We had discussions about backup power supply for the solar panels and the subject of methane fuel cells came up:

Finally, a Robust Fuel Cell that Runs on Methane at Practical Temperatures (http://www.rh.gatech.edu/news/613410/finally-robust-fuel-cell-runs-methane-practical-temperatures)
Title: Re: Power options for a Mars settlement
Post by: Tulse on 11/07/2018 05:54 pm
If the base is making methane, it's already producing hydrogen, so I don't see how moving to a methane fuel cell rather than a hydrogen one is all that beneficial -- it seems like it would just be adding inefficiency.
Title: Re: Power options for a Mars settlement
Post by: jpo234 on 11/07/2018 05:59 pm
If the base is making methane, it's already producing hydrogen, so I don't see how moving to a methane fuel cell rather than a hydrogen one is all that beneficial -- it seems like it would just be adding inefficiency.

They won't store hydrogen.
Title: Re: Power options for a Mars settlement
Post by: Tulse on 11/07/2018 06:08 pm
If the base is making methane, it's already producing hydrogen, so I don't see how moving to a methane fuel cell rather than a hydrogen one is all that beneficial -- it seems like it would just be adding inefficiency.

They won't store hydrogen.
Presumably they could if there is benefit to doing so, like powering more efficient fuel cells.  I think this largely comes down to what sort of penalty there is for running fuel cells that have to strip the hydrogen out of methane, versus feeding hydrogen directly.
Title: Re: Power options for a Mars settlement
Post by: Lemurion on 11/08/2018 12:16 am
If the base is making methane, it's already producing hydrogen, so I don't see how moving to a methane fuel cell rather than a hydrogen one is all that beneficial -- it seems like it would just be adding inefficiency.

They won't store hydrogen.
Presumably they could if there is benefit to doing so, like powering more efficient fuel cells.  I think this largely comes down to what sort of penalty there is for running fuel cells that have to strip the hydrogen out of methane, versus feeding hydrogen directly.

I'd actually be more likely to phrase it as whether the drawbacks of the methane fuel cells outweigh the drawbacks of hydrogen storage. My own expectation is that if the methane fuel cells are at all effective it's probably a better idea from their perspective to stick with methane rather than dealing with a separate hydrogen infrastructure.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 11/08/2018 04:56 pm
If the base is making methane, it's already producing hydrogen, so I don't see how moving to a methane fuel cell rather than a hydrogen one is all that beneficial -- it seems like it would just be adding inefficiency.

They won't store hydrogen.

Presumably they could if there is benefit to doing so, like powering more efficient fuel cells.  I think this largely comes down to what sort of penalty there is for running fuel cells that have to strip the hydrogen out of methane, versus feeding hydrogen directly.

I'd actually be more likely to phrase it as whether the drawbacks of the methane fuel cells outweigh the drawbacks of hydrogen storage. My own expectation is that if the methane fuel cells are at all effective it's probably a better idea from their perspective to stick with methane rather than dealing with a separate hydrogen infrastructure.

You have to go back to first principles. Which are that it is desirable to be able to use the methalox stocks, that you are creating anyway for ISRU propellant, as an emergency power supply. 'Emergency' because you don't want to use them, other than for propellant, having gone to a great deal of effort and expense to produce them in the first place! As such, you want the cheapest and simplest additional equipment that will do that job. That implies something that will tap the methalox directly to produce power - either a methane fuel cell or an internal combustion engine attached to a generator. Setting up a hydrogen production and storage system would seem an unnecessary complication.
Title: Re: Power options for a Mars settlement
Post by: biosehnsucht on 11/08/2018 10:58 pm
My personal vote would be to have both a methane ICE and a methane fuel cell, at least once humans are there.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/09/2018 12:54 pm
it is desirable to be able to use the methalox stocks, that you are creating anyway for ISRU propellant, as an emergency power supply. [...] As such, you want the cheapest and simplest additional equipment that will do that job. That implies something that will tap the methalox directly to produce power - either a methane fuel cell or an internal combustion engine attached to a generator.

Not just a generator, a heat exchanger. If the settlement is using solar PV as the main power source, then, outside of a rare "burned out the main lines" emergency repairs, each PV panel is, in effect, an independent power supply. So the only time you'll need to worry about backup power is during the extreme dust storms (as occurred recently. And repeat roughly decadally.) In that situation, heat might also be an issue, so methalox "combined heat and power" generators might be the ideal choice.

My personal vote would be to have both a methane ICE and a methane fuel cell, at least once humans are there.

IMO, better to have redundancy of similar tech (ie, several ICE+CHP generator sets) rather than different kinds of back-up. That reduces the number of parts you need to stock/ship/manufacture, and the skill-sets you need for maintenance.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/25/2018 11:05 pm
Got an email alert to activity on this thread, now deleted (presumably spam), but it got me thinking about the last thing I wrote...

it is desirable to be able to use the methalox stocks, that you are creating anyway for ISRU propellant, as an emergency power supply. [...] As such, you want the cheapest and simplest additional equipment that will do that job. That implies something that will tap the methalox directly to produce power - either a methane fuel cell or an internal combustion engine attached to a generator.
Not just a generator, a heat exchanger. If the settlement is using solar PV as the main power source, then, outside of a rare "burned out the main lines" emergency repairs, each PV panel is, in effect, an independent power supply. So the only time you'll need to worry about backup power is during the extreme dust storms (as occurred recently. And repeat roughly decadally.) In that situation, heat might also be an issue, so methalox "combined heat and power" generators might be the ideal choice.
[...]
IMO, better to have redundancy of similar tech (ie, several ICE+CHP generator sets) rather than different kinds of back-up. That reduces the number of parts you need to stock/ship/manufacture, and the skill-sets you need for maintenance.

Another item you'll be using a lot is vehicles. Either manned or teleop'd/robotic. Which means they require power systems. They'll almost certainly have electric drives, so that lends itself to battery storage. The mass/volume numbers favour battery/electric because any fuel burning (ICE or turbine) requires on-board oxygen, which means not just the mass of O₂ but also the mass of the heavy tanks, so batteries probably win on simple mass, and certainly win on simplicity.

But batteries often take a long time to recharge. That's okay, you just recharge overnight from the base power supply... But, assuming solar, overnight is when base is on it's own batteries. So in addition to the base battery system, you'd need the batteries in the vehicles PLUS that same amount of batteries again at the base getting charged in addition to the base's own storage. However, that only adds a day or two to the base's emergency power supply. Say a week if you get lucky and everything (vehicles, base, vehicle-bank-at-the-base) is fully charged. Not much bang for your buck.

So when we compare the vehicles having battery/electric vs methalox-genny/electric, and include that extra base requirement for batteries vs extra methalox production, how close is the methalox to batteries? Because if methalox is even a close second, it would be worth fitting the vehicles with methalox generators to use as emergency back up for the base. (And as a side benefit, you get faster "recharge" for the vehicles.)



If you accept my reasoning... Which power generator would make more sense? Fuel cell? Gas turbine+generator? ICE+generator? In terms of efficiency, reliability, ease of repair, size, etc.
Title: Re: Power options for a Mars settlement
Post by: RonM on 11/25/2018 11:55 pm
So when we compare the vehicles having battery/electric vs methalox-genny/electric, and include that extra base requirement for batteries vs extra methalox production, how close is the methalox to batteries? Because if methalox is even a close second, it would be worth fitting the vehicles with methalox generators to use as emergency back up for the base. (And as a side benefit, you get faster "recharge" for the vehicles.)



If you accept my reasoning... Which power generator would make more sense? Fuel cell? Gas turbine+generator? ICE+generator? In terms of efficiency, reliability, ease of repair, size, etc.

Hydrogen fuel cells are great, but fuel cells using carbon-based fuels like methane have problems with the leftover carbon gumming up the works. High maintenance.

Turbines are very efficient if large, but they don't scale down well. Great for locomotives and Abrams tanks, not good for car-sized vehicles. Turbines might be hard to produce locally.

ICE would be my choice for smaller vehicles and turbines for very large vehicles.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/26/2018 12:32 am
Turbines are very efficient if large, but they don't scale down well. Great for locomotives and Abrams tanks, not good for car-sized vehicles.

You can buy 5kW NG turbine-generators that mass 80kg all up. Call it 100kg when "Mars proofed". Not including fuel/ox tanks.

Turbines might be hard to produce locally.

They are also finicky about fuel quality, and restrictive about loading. Might not apply to these micro-gas-turbines. In which case, the efficiency gains and lower maintenance requirements might win out.

My gut says ICE. But my heart says "It's the 21st century!"
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 11/26/2018 12:59 am
I think they will have two different types of primary power (nuclear fission and solar) and batteries for storage and electric motors.  While they could build an ICE why bother, they are less efficient than electrics and are consuming you fuel to go home. 

If you want emergency back up power, as a last resort use methane fuel cells so you can use the methane directly don't convert and store the hydrogen first.

Title: Re: Power options for a Mars settlement
Post by: matthewkantar on 11/26/2018 02:24 am
Maybe the inefficiency of ICE tech won't be such a negative on mars where cabin heat requirements will be high.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 11/26/2018 03:38 am
Maybe... but you are still still consuming methane on regular basis as part of normal operations rather than an emergency only.
Title: Re: Power options for a Mars settlement
Post by: Cologan on 11/27/2018 09:28 am
we are talking about the ICE as emergency backup right ? as backup its not a horribly bad idea, depending on how rich in terms of fuel and oxygen the colony will get, something we can only guess for now. primary powersource i think we can agree its silly ? Unless for some reason you can still run a net plus in energy after factoring in refinery energydraw of said fuel&oxygen, and even then it would be silly. unless of course we wanna start terraforming from the get-go (insert sarcasm-sign here)

Solar&Kilopower reactors + some Tesla-derived batteries seem to be the more conservative options. Something i havent seen in a while is whether its worth figuring out if the colony, especially at the beginning, can utilize the Spaceships own solar panels. Some simple mechanism the panels could rest on would make the whole ordeal more simple, you can hook up the panels to the ISRU to make its own fuel. The area around the ship would be vacant anyways.

Will do a quick fly-by through this thread and see how unnecessary this post is, will delete if i didnt contribute anything.
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 11/27/2018 04:30 pm
Maybe... but you are still still consuming methane on regular basis as part of normal operations rather than an emergency only.
You're going to have some level of fuel consumption even for "emergency" generators anyway.

Best practice for internal-combustion-powered emergency generators includes running them periodically (on the order of an hour a week.   At least that's what they seemed to be doing with one near my office last decade).

I believe this keeps all the lubricants where they need to be and tests that they can start when needed...
Title: Re: Power options for a Mars settlement
Post by: speedevil on 11/27/2018 07:46 pm
Best practice for internal-combustion-powered emergency generators includes running them periodically (on the order of an hour a week.   At least that's what they seemed to be doing with one near my office last decade).
Methane generators have considerably longer lives due to the cleaner input and outputs, and as I understand longer test intervals.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 11/28/2018 03:19 am
I can't think of a reason to a methane ICE instead of a fuel cell...   An ICE is more complicated and has rotating parts.  A fuel cell has a couple of valves.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 11/28/2018 04:44 am
I can't think of a reason to a methane ICE instead of a fuel cell...   An ICE is more complicated and has rotating parts.  A fuel cell has a couple of valves.
A fuel cell has a couple of valves and a completely unmaintainable membrane that if it gets poisoned has to come from earth.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 11/28/2018 02:38 pm
Good point.  The membrane could be a replaceable item shipped from earth it has to be lighter than ICE spares...
Title: Re: Power options for a Mars settlement
Post by: Steve D on 11/28/2018 04:58 pm
On a standard ICE the nitrogen in air moderates the fuels burn and imparts a great deal of power to the piston as it expands from the heat of the fuel burning. An ICE (at least a standard one) would explode if all it was fed was methane and pure oxygen. Going fuel rich or oxygen rich wastes a lot of resources. How would this be fixed? Feed it air instead of oxygen, cool and recycle the nitrogen and replenish the oxygen? How would cooling work?
Title: Re: Power options for a Mars settlement
Post by: Semmel on 11/28/2018 05:04 pm
Feed it CO2 from the output?
Title: Re: Power options for a Mars settlement
Post by: Steve D on 11/28/2018 06:33 pm
Wouldnt that be like using a fire extinguisher on it?
 
Title: Re: Power options for a Mars settlement
Post by: speedevil on 11/28/2018 06:42 pm
On a standard ICE the nitrogen in air moderates the fuels burn and imparts a great deal of power to the piston as it expands from the heat of the fuel burning. An ICE (at least a standard one) would explode if all it was fed was methane and pure oxygen. Going fuel rich or oxygen rich wastes a lot of resources. How would this be fixed? Feed it air instead of oxygen, cool and recycle the nitrogen and replenish the oxygen? How would cooling work?
Exhaust gas recirculation (https://en.wikipedia.org/wiki/Exhaust_gas_recirculation) works fine in earthly cars.
You just run a fraction of the exhaust into the intake - possibly after cooling to drop out much of the water.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 11/28/2018 07:57 pm
Wouldnt that be like using a fire extinguisher on it?

No, CO2 only extinguishes flame by displacing oxygen. As long as you run at reasonable fuel/ox/inert ratios, it will work fine.

You can use both CO2 and water vapor as working fluids in an ICE.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/28/2018 08:00 pm
On a standard ICE the nitrogen in air moderates the fuels burn and imparts a great deal of power to the piston as it expands from the heat of the fuel burning. An ICE (at least a standard one) would explode if all it was fed was methane and pure oxygen. Going fuel rich or oxygen rich wastes a lot of resources. How would this be fixed? Feed it air instead of oxygen, cool and recycle the nitrogen and replenish the oxygen? How would cooling work?
Exhaust gas recirculation works fine in earthly cars.
You just run a fraction of the exhaust into the intake - possibly after cooling to drop out much of the water.
You need to cool about 60% of the combustion energy, as the genset is about 40% efficient.  You can cool the engine jacket, condense out the combustion water and recirculate the nitrogen and co2.  Co2 pressure will build up, so you need to capture it or exhaust it.  Don’t quite see how you can separate the co2 continuously.  Might be best to use water rather than nitrogen and a exhaust out part or the combustion products?  Sad to waste water and co2.  A large amine system ?
Or perhaps store the fuel as H2 rather than methane?  Just run the Sabatier as needed?  Solves the co2 problem .
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/28/2018 08:52 pm
On a standard ICE the nitrogen in air moderates the fuels burn and imparts a great deal of power to the piston as it expands from the heat of the fuel burning. An ICE (at least a standard one) would explode if all it was fed was methane and pure oxygen. Going fuel rich or oxygen rich wastes a lot of resources. How would this be fixed? Feed it air instead of oxygen, cool and recycle the nitrogen and replenish the oxygen? How would cooling work?
Exhaust gas recirculation works fine in earthly cars.
You just run a fraction of the exhaust into the intake - possibly after cooling to drop out much of the water.
You need to cool about 60% of the combustion energy, as the genset is about 40% efficient.  You can cool the engine jacket, condense out the combustion water and recirculate the nitrogen and co2.  Co2 pressure will build up, so you need to capture it or exhaust it.  Don’t quite see how you can separate the co2 continuously.  Might be best to use water rather than nitrogen and a exhaust out part or the combustion products?  Sad to waste water and co2.  A large amine system ?
Or perhaps store the fuel as H2 rather than methane?  Just run the Sabatier as needed?  Solves the co2 problem .
Most of the water can be condensed in a cold trap and excess CO2 can be exhausted to the atmosphere which is CO2 in any case so not a lot lost there - CO2 is cheap on Mars..
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 11/28/2018 09:41 pm
Or perhaps store the fuel as H2 rather than methane?

How hard would it be to ISRU an Zero Boiloff hydrogen tank?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/28/2018 11:36 pm
Or perhaps store the fuel as H2 rather than methane?

How hard would it be to ISRU an Zero Boiloff hydrogen tank?
not hard if it’s gaseous.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 11/28/2018 11:39 pm
Or perhaps store the fuel as H2 rather than methane?

How hard would it be to ISRU an Zero Boiloff hydrogen tank?
not hard if it’s gaseous.
You are saying Hydrogen becomes easier to contain as a gas than as a liquid? That seems odd to me.
Title: Re: Power options for a Mars settlement
Post by: envy887 on 11/29/2018 12:52 am
Or perhaps store the fuel as H2 rather than methane?

How hard would it be to ISRU an Zero Boiloff hydrogen tank?
not hard if it’s gaseous.
You are saying Hydrogen becomes easier to contain as a gas than as a liquid? That seems odd to me.

Well, you don't have to worry about boiloff.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 11/29/2018 06:53 am
Or perhaps store the fuel as H2 rather than methane?

How hard would it be to ISRU an Zero Boiloff hydrogen tank?
not hard if it’s gaseous.
You are saying Hydrogen becomes easier to contain as a gas than as a liquid? That seems odd to me.

Well, you don't have to worry about boiloff.
Ah- a technically correct answer. :p

Does gasous hydrogen have the same long term containment issues that liquid hydrogen does? I recall hearing of hydrogen leaking through solid metal, and similar issues.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 11/29/2018 07:09 am
Does gasous hydrogen have the same long term containment issues that liquid hydrogen does? I recall hearing of hydrogen leaking through solid metal, and similar issues.
'no' - in that if you have 100 tons of hydrogen - a million cubic meters or so at STP, diffusion is not an issue, leaks are. (which can be captured by a light outer shell).

This is a sphere some hundred meters in diameter, or a twenty meters in diameter at ~200 bar.

As an example if made from Al, it would be of the order of 20000 tons (at either pressurisation).

In principle a thin film could contain it at near atmospheric pressure, but now you have to deal with a hundred million cubic meters - and ...

If you can find large lava tubes, this would be excellent, and ideal of course.



Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 11/29/2018 07:14 am
Or perhaps store the fuel as H2 rather than methane?

How hard would it be to ISRU an Zero Boiloff hydrogen tank?
not hard if it’s gaseous.
You are saying Hydrogen becomes easier to contain as a gas than as a liquid? That seems odd to me.

Well, you don't have to worry about boiloff.

Either way, it seems a very large investment in Hydrogen storage facilities in terms of both mass and/or continual power requirements when compared with the straightforward technical fixes to enable a methalox ICE to operate. Also, how much Hydrogen will you store and what happens when you run out? In all likelihood you're still going to have methalox stores and therefore still need some way of utilising them as an emergency power source.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/29/2018 11:58 am
Or perhaps store the fuel as H2 rather than methane?

How hard would it be to ISRU an Zero Boiloff hydrogen tank?
not hard if it’s gaseous.
You are saying Hydrogen becomes easier to contain as a gas than as a liquid? That seems odd to me.

Well, you don't have to worry about boiloff.

Either way, it seems a very large investment in Hydrogen storage facilities in terms of both mass and/or continual power requirements when compared with the straightforward technical fixes to enable a methalox ICE to operate. Also, how much Hydrogen will you store and what happens when you run out? In all likelihood you're still going to have methalox stores and therefore still need some way of utilising them as an emergency power source.
The main reason you produce hydrogen is to produce methane for propellant.  And almost all of the energy involved in the process goes to the electrolysis of the water to create the hydrogen.  The Sabatier process itself is exothermic, it loses energy since methane has less chemical energy available than hydrogen.  The hydrogen is an energy battery.
To avoid hydrogen boiloff, of methane boiloff for that matter, you need to reduce heat gain, and then use refrigeration to remove the heat that remains, rather than hydrogen phase change(boiloff).  Refrigeration using compression to remove energy from -250C and disperse it in an environment at-50C is an inherently inefficient process, using more energy than it removes, but it is thorougly understood and available technology.  An hydrogen tank in an underground vault with aluminium walls is essentally a thermos bottle, with the main thermal transmission mechanism being radiation.  Insulation, plus low emissivity coatings, can probably reduce heat gain to a very small amount.  So the compression energy should be low. 
This being said, I expect almost half of the energy used at the colony will be the production of propellant, at least for quite some time until local production starts exceeding imports.  If we stop producing propellant during dust storms, the solar arrays can be repurposed to food production, the other large power drain on the colony.  The few curves I have seen of solar irradience during dust storms seemed to mention a power drop of 30%.  If this is correct, then the need for a backup power source becomes non existant. 
It would be absurd to burn propellant to produce propellant, after all.
Anybody have a number for reduction of power during dust storms, taking into account a mechanism on the solar panels to remove dust accumulation during the storm?
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 12/01/2018 05:39 am
(Snip previous posts for length)

The main reason you produce hydrogen is to produce methane for propellant.  And almost all of the energy involved in the process goes to the electrolysis of the water to create the hydrogen.  The Sabatier process itself is exothermic, it loses energy since methane has less chemical energy available than hydrogen.  The hydrogen is an energy battery.
To avoid hydrogen boiloff, of methane boiloff for that matter, you need to reduce heat gain, and then use refrigeration to remove the heat that remains, rather than hydrogen phase change(boiloff).  Refrigeration using compression to remove energy from -250C and disperse it in an environment at-50C is an inherently inefficient process, using more energy than it removes, but it is thorougly understood and available technology.  An hydrogen tank in an underground vault with aluminium walls is essentally a thermos bottle, with the main thermal transmission mechanism being radiation.  Insulation, plus low emissivity coatings, can probably reduce heat gain to a very small amount.  So the compression energy should be low. 
This being said, I expect almost half of the energy used at the colony will be the production of propellant, at least for quite some time until local production starts exceeding imports.  If we stop producing propellant during dust storms, the solar arrays can be repurposed to food production, the other large power drain on the colony.  The few curves I have seen of solar irradience during dust storms seemed to mention a power drop of 30%.  If this is correct, then the need for a backup power source becomes non existant. 
It would be absurd to burn propellant to produce propellant, after all.
Anybody have a number for reduction of power during dust storms, taking into account a mechanism on the solar panels to remove dust accumulation during the storm?


I think we're going off-track. Let's recap from first principles: SpaceX's plan relies on ISRU methalox propellant manufacture on Mars. The time over which the methalox is produced is a lot greater than the time during which it is used and therefore there will be a need to store methalox on Mars. Any store of methalox can be used to generate power given the appropiate equipment (ICE generator, methane fuel cell, whatever).

The proposal then is to take such equipment to Mars so that the methalox stores could be used to generate power in an emergency. The methalox stores are not being created to act as a power source; it's just that they inherently have that capability providing you have the equipment. IMO it would be irresponsible not to have that equipment. Hopefully, it will never have to be used, but it's better than dying. You can over-size your intended power production and intended forms of storage (batteries etc). You can diversify it (solar, nuclear etc). You can switch off non-essential equipment if necessary (including methalox production - it would of course be insane to use the methalox stores to produce power to keep methalox production going). It would be extremely unlikely that you'll ever need to utilise the methalox stores to produce power - which is good as you don't want to use them for anything other than their intended purpose of propelling rockets. But extremely unlikely things occasionally happen, so it's as well to have as many back-ups as possible. The ability to utilise the methalox store is the final back-up; used when all else fails.

Given that, I don't see the purpose of producing and storing hydrogen. Methalox has to be created and stored. Hydrogen does not; it's not going to be used as propellant, certainly. So why are you going to the trouble and expense, in terms of both mass and finacial budgets, of creating such a store? I suppose you could produce it as part of the intended operation of the power system, to store power during the night or dust storms etc. That requires an examination of the engineering trades between this and batteries etc. But you still have to produce the methalox stores anyway, so still have the opportunity to, and therefore the responsibility of being able to, use them for emergency power, so you're not saving anything in that regard. (NB If you store hydrogen with the idea of using it to produce methalox at a later date then you'll need a higher capacity methalox production plant, which will be under-utilised most of the time and is more expensive.)

I suppose you might have another reason to produce and store hydrogen - perhaps for Martian blimps? - and if you have a store of hydrogen you can use it as a source of power in an emergency (and therefore should be able to by a similar argument in respect of methalox). But, I don't see such usages in the early days of any base/colony, whereas methalox is going to be used right from the beginning.
Title: Re: Power options for a Mars settlement
Post by: NH22077 on 12/01/2018 07:02 pm
On a standard ICE the nitrogen in air moderates the fuels burn and imparts a great deal of power to the piston as it expands from the heat of the fuel burning. An ICE (at least a standard one) would explode if all it was fed was methane and pure oxygen. Going fuel rich or oxygen rich wastes a lot of resources. How would this be fixed? Feed it air instead of oxygen, cool and recycle the nitrogen and replenish the oxygen? How would cooling work?

I would build an ICE with the intake using outside air routed to a blower, to bring the intake manifold pressure up to 15psi.
The less complex method would be to inject gaseous methane & O2 into the intake manifold. With the exhaust routed outside.
Some EGR could be used to keep the intake charge warm. A more complex method would be to have separate methane & lox injectors on each cylinder. The liquid cooled engine would have a heat exchanger with the heat-pump for the Mars base's main ECLSS. That is if the ECLSS uses a water loop for heating & cooling. I would also have the genset indoors so a block heater & low temp bearings for the generator. Are not necessary, and that gives you a shirt sleeve environment for maintenance. In a room that could be sealed off if the valves sealing intake or exhaust went not in use go bad.

A conventional natural gas genset on Earth is about 35% efficient.

I also agree that it shouldn't be used except in an emergency.

Ned
Title: Re: Power options for a Mars settlement
Post by: Dao Angkan on 01/09/2019 10:42 pm
So this is a long thread, I haven't read it all. Before I go indepth ... has pumped storage been discussed yet?
Title: Re: Power options for a Mars settlement
Post by: NH22077 on 01/17/2019 12:26 pm
So this is a long thread, I haven't read it all. Before I go indepth ... has pumped storage been discussed yet?

Hi Dao,
Yes, pumped storage has been discussed up thread. Less gravity will mean less output for the same storage & elivation compared to Earth. SpaceX 1st bases r probably going to be on flat low lying areas. Lower in the atmostphere means less radiation. Flat makes for safer landings.

Ned
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 01/18/2019 12:57 am
Before I go indepth ... has pumped storage been discussed yet?

Yes, pumped storage has been discussed up thread. Less gravity will mean less output for the same storage & elivation compared to Earth. SpaceX 1st bases r probably going to be on flat low lying areas. Lower in the atmostphere means less radiation. Flat makes for safer landings.

We've probably also discussed that pumped storage is just a way of lifting and lowering mass. It doesn't matter what the mass is. Water is just convenient on some places on Earth because you have existing water sources, dams, pumps, etc. If there's nothing special about water at your site, you can just lift and drop any dumb mass. A lump of metal, a box of rubble, whatever, just substitute winches for pumps and gears for turbines.

(Reduction in gravity works both ways: in lower gravity you get less energy storage from any given amount of mass, but your equipment can also handle a proportionally larger amount of mass for the same size/mass/loading.)

I imagine that we've also discussed the inefficiencies of such systems. AIUI, net output is typically 80% of input, depending on the details of the system. But IMO, you should assume a locally made (ISRU) system will be cruder, and will be operated under less than ideal conditions, 70-80% might be a reasonable planning assumption.

("Under less than ideal conditions: You will often need to cycle the system in an inefficient way due to the supply/demand requirements of the base being more important than optimising the storage system itself.)
Title: Re: Power options for a Mars settlement
Post by: meekGee on 01/18/2019 04:09 pm
Actually I ran simple numbers on a power generation scheme where trucks drive up and down a slope, bringing down dirt and leaving it there.

Several variants, such as regular trucks on a dirt path, a railway, and an aerial tram.

There's something there, but it isn't as easy as you'd think.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/11/2019 03:02 pm
Quantum Dot PV Update

OP:  record-setting (2017) experimental QD PV solar cell rated at 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848)

Mar. 19 2019:  commercial plant (http://www.qmcdots.com/press/press.php) under construction, for production of QD PV solar cells and other QD devices.  Quantum Materials Corp / Amtronics CC.

Quantum Materials:  QD PV solution statement (http://www.qmcdots.com/products/products-solar.php)

Solterra subsidiary:  statement on QD PV automated flexographic printing (http://www.solterrasolarcells.com/innovation/flexographicprinting.php) 

Related:

Like the 2017 record-holder, a 2019 record-setting solar cell also leverages PEN substrate and Ag nanowire electrodes.  The active layer in this new record-holder is perovskite.  Rating:  29.4 kW/kg (https://pubs.rsc.org/en/content/articlelanding/2018/ta/c8ta10585e/unauth#!divAbstract)

(https://pubs.rsc.org/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=C8TA10585E)

Caveat:  Perovskite solar cell stability problems were noted in thread previously (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1850500#msg1850500).
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/11/2019 06:01 pm
Quantum Dot PV Update

OP:  record-setting (2017) experimental QD PV solar cell rated at 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848)

Mar. 19 2019:  commercial plant (http://www.qmcdots.com/press/press.php) under construction, for production of QD PV solar cells and other QD devices.  Quantum Materials Corp / Amtronics CC.

Quantum Materials:  QD PV solution statement (http://www.qmcdots.com/products/products-solar.php)

Solterra subsidiary:  statement on QD PV automated flexographic printing (http://www.solterrasolarcells.com/innovation/flexographicprinting.php) 

Related:

Like the 2017 record-holder, a 2019 record-setting solar cell also leverages PEN substrate and Ag nanowire electrodes.  The active layer in this new record-holder is perovskite.  Rating:  29.4 kW/kg (https://pubs.rsc.org/en/content/articlelanding/2018/ta/c8ta10585e/unauth#!divAbstract)

(https://pubs.rsc.org/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=C8TA10585E)

Caveat:  Perovskite solar cell stability problems were noted in thread previously (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1850500#msg1850500).

Interesting.  However, I would be concerned that the fairly low efficiency (10% if I read correctly) would mean that the overall cost of the panels to Mars would be higher because of support structures and such.
Perhaps if the support structure is produced in-situ then this would be advantageous?
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/11/2019 08:39 pm
I think they will have two different types of primary power (nuclear fission and solar) and batteries for storage and electric motors.  While they could build an ICE why bother, they are less efficient than electrics and are consuming you fuel to go home. 

If you want emergency back up power, as a last resort use methane fuel cells so you can use the methane directly don't convert and store the hydrogen first.

I agree.

For some reason, it seems like most people talk about either solar or nuclear, like they're mutually exclusive. 
I think nuclear and solar tend to compliment one another. People are generally more active during the day.
That's human nature. I don't see why it would be different on Mars. So nuclear supplies baseline power at night,
while solar provides the extra power needed during daylight hours.

They'll also need some batteries to smooth out the load curve, but nowhere near the number of batteries they'd require for a solar-only system.

Also, for some reason, it seems like a lot of people are only familiar with hydrogen fuel cells. There are actually many different types of fuel cells. They even have fuel cells that run on gasoline (https://www.technologyreview.com/s/426252/gasoline-fuel-cell-would-boost-electric-car-range/). So given that they'll need to store methane and oxygen separately, using methalox fuel cells as an emergency backup power source seems like a natural choice.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/11/2019 09:06 pm
The ARC reactor looks likeit would fit inside a 12m hull, with replacement tokomak sleeves being able to be shipped in a 9m Starship.

It wont be available for another 10-15 years, but that'll be right about the time mars colonization starts scaling up.

https://en.wikipedia.org/wiki/ARC_fusion_reactor
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/11/2019 11:05 pm
I would like to add a point about Sabatier reactors and hydrogen storage.  In my experience most catalyst degradation occurs at startup.  Steady state operation is preferable.  If we add a hydrogen buffer between the electrolysis unit and the Sabatier reactor we can regulate hydrogen flow for a fraction of the mass regulating using batteries.  I believe it is reasonable to expect that early Martian colonies will have at least some hydrogen storage.

So roughly how big is this hydrogen storage buffer?

Assuming each Starship requires 240 tonnes of methane we need to produce 60 tonnes of hydrogen.  Assuming a 720 sol production period we need a buffer that can store 83.3 kg to allow a one sol buffer.  83.3 kg isn't a lot, but when every bit counts...
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/11/2019 11:22 pm
I believe it is reasonable to expect that early Martian colonies will have at least some hydrogen storage.

Why?

Here's a quote (https://middleclasstech.wordpress.com/2015/01/14/elon-musk-hydrogen-fuel-cells-are-extremely-silly/) from Elon Musk:
Quote from: Elon Musk
Hydrogen has very low density. It’s a pernicious molecule that likes to get all over the place. If you get hydrogen leaks from invisible gas, you can’t even tell that it’s leaking. But then it’s extremely flammable, when it does, and has an invisible flame.

If you’re going to pick an energy storage mechanism, hydrogen is an incredibly dumb one to pick. You should just pick methane. That’s much, much easier...
Title: Re: Power options for a Mars settlement
Post by: ZChris13 on 04/11/2019 11:31 pm
Here's a quote (https://middleclasstech.wordpress.com/2015/01/14/elon-musk-hydrogen-fuel-cells-are-extremely-silly/) from Elon Musk:
Quote from: Elon Musk
Hydrogen has very low density. It’s a pernicious molecule that likes to get all over the place. If you get hydrogen leaks from invisible gas, you can’t even tell that it’s leaking. But then it’s extremely flammable, when it does, and has an invisible flame.

If you’re going to pick an energy storage mechanism, hydrogen is an incredibly dumb one to pick. You should just pick methane. That’s much, much easier...
Hydrogen doesn't burn in Martian Atmosphere
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/11/2019 11:34 pm
I believe it is reasonable to expect that early Martian colonies will have at least some hydrogen storage.

Why?

Here's a quote (https://middleclasstech.wordpress.com/2015/01/14/elon-musk-hydrogen-fuel-cells-are-extremely-silly/) from Elon Musk:
Quote from: Elon Musk
Hydrogen has very low density. It’s a pernicious molecule that likes to get all over the place. If you get hydrogen leaks from invisible gas, you can’t even tell that it’s leaking. But then it’s extremely flammable, when it does, and has an invisible flame.

If you’re going to pick an energy storage mechanism, hydrogen is an incredibly dumb one to pick. You should just pick methane. That’s much, much easier...
You have to have some hydrogen storage because electrolysis produces hydrogen and oxygen, not hydrogen and methane. That being said it is probably best to convert the hydrogen into methane as soon as possible.  You might also use it for steel production.

If you are going to store energy at the utility level, perhaps the best solution would be Pumped Heat Electrical Storage.
http://energystorage.org/energy-storage/technologies/pumped-heat-electrical-storage-phes
These installations use steel tanks and an inert gas such as argon as working medium, storing energy with an efficiency of 75 to 80%. A reversible compressor is used to both compress the working fluid and to extract the energy from the expanding gas. The use of materials readily available on Mars make this an attractive mid term storage solution.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/11/2019 11:45 pm
Natural gas generators on earth are NOT internal combustion engines.  They are not efficient enough.  They are converted jet engines that do double duty.  A jet engine turns a generator from the front of the turbine.  The exhaust is then run through a steam boiler to generate steam to turn another turbine behind it, usually an old coal fired boiler.  Thus generation the maximum amount of electricity with both mechanical energy conversion as well as heat conversion to electricity. 

Now on Mars a small jet engine running metholox fuel with both a generator and a steam generator can produce a huge amount of electricity at night.  The excess water produced can be ran back into the water system and used as heat for the colony when after making steam electricty.  It is also far more efficient than fuel cells. 

These engines on earth are already replacing coal as the number one producer of electricity. 

Methane for rockets to return to earth will already be made.  Excess could be used to produce electricity at night.  Solar power for daytime and metholox production. 

When Mars gets really big nuclear power may have to come into play. 

Liquid hydrogen is colder and more subject to leaks due to the small atoms.  Would cost more to keep cold. 

A small jet engine generator system with steam turbine added is a whole lot quicker and cheaper to bring to Mars than as components are currently "off the shelf" and far less expensive with more bang for the buck than anything other than solar on Mars.  Solar will be required initially anyway. 
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/11/2019 11:48 pm
That being said it is probably best to convert the hydrogen into methane as soon as possible.

Right.

That's why long-term hydrogen storage doesn't make sense to me, at least not at the scale required for an emergency backup for powering the colony.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/11/2019 11:53 pm
Here's a quote (https://middleclasstech.wordpress.com/2015/01/14/elon-musk-hydrogen-fuel-cells-are-extremely-silly/) from Elon Musk:
Quote from: Elon Musk
Hydrogen has very low density. It’s a pernicious molecule that likes to get all over the place. If you get hydrogen leaks from invisible gas, you can’t even tell that it’s leaking. But then it’s extremely flammable, when it does, and has an invisible flame.

If you’re going to pick an energy storage mechanism, hydrogen is an incredibly dumb one to pick. You should just pick methane. That’s much, much easier...
Hydrogen doesn't burn in Martian Atmosphere

True.  Obviously, Elon's quote above was referring to hydrogen on Earth.

But I still think the main points apply. For example, if you're combining hydrogen and oxygen in a fuel cell as a backup power source, and there's a rupture in the fuel cell, the burning hydrogen would be invisible.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 12:03 am
Natural gas generators on earth are NOT internal combustion engines.  They are not efficient enough.  They are converted jet engines that do double duty.  A jet engine turns a generator from the front of the turbine.  The exhaust is then run through a steam boiler to generate steam to turn another turbine behind it, usually an old coal fired boiler.  Thus generation the maximum amount of electricity with both mechanical energy conversion as well as heat conversion to electricity. 

Now on Mars a small jet engine running metholox fuel with both a generator and a steam generator can produce a huge amount of electricity at night.  The excess water produced can be ran back into the water system and used as heat for the colony when after making steam electricty.  It is also far more efficient than fuel cells. 

These engines on earth are already replacing coal as the number one producer of electricity. 

Methane for rockets to return to earth will already be made.  Excess could be used to produce electricity at night.  Solar power for daytime and metholox production. 

When Mars gets really big nuclear power may have to come into play. 

Liquid hydrogen is colder and more subject to leaks due to the small atoms.  Would cost more to keep cold. 

A small jet engine generator system with steam turbine added is a whole lot quicker and cheaper to bring to Mars than as components are currently "off the shelf" and far less expensive with more bang for the buck than anything other than solar on Mars.  Solar will be required initially anyway.
If you have solar during the day, then it makes more sense to divert some of the electricity into a thermal compression system rather than into an electrolysis + Sabatier+ gas turbine, because the overall efficiency of this triple conversion is much less efficient that the direct use of an electric motor to run a compressor, than can latter be reversed to run a generator.  And the heat involved seems to be somewhat less as well, so less wear overall.
As you mention, a large portion of the electricity will go directly to propellant production; but storing energy in the propellant is not optimum, again, if compression is sufficiently efficient and reversible.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/12/2019 02:11 am
Well, Mars is cold, excess heat can heat the colony.  The gas turbine not only will turn a generator, but the heat from the burning methane can make steam for steam power also, then used to heat the colony where needed. 

I worked for a natural gas company before retirement.  We tried fuel cells, and other exotic means.  The turbine is 90+ efficient in electric production, then the heat is about 90%+ used to make more electricity through steam.  Gas turbine engines placed at coal fired replacement plants almost doubled power output by using both the mechanical production + the heat production of electricity in combination. 
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/12/2019 02:58 am
I believe it is reasonable to expect that early Martian colonies will have at least some hydrogen storage.

Why?

Here's a quote (https://middleclasstech.wordpress.com/2015/01/14/elon-musk-hydrogen-fuel-cells-are-extremely-silly/) from Elon Musk:
Quote from: Elon Musk
Hydrogen has very low density. It’s a pernicious molecule that likes to get all over the place. If you get hydrogen leaks from invisible gas, you can’t even tell that it’s leaking. But then it’s extremely flammable, when it does, and has an invisible flame.

If you’re going to pick an energy storage mechanism, hydrogen is an incredibly dumb one to pick. You should just pick methane. That’s much, much easier...

From the part of my post you snipped:

Quote
In my experience most catalyst degradation occurs at startup.  Steady state operation is preferable.  If we add a hydrogen buffer between the electrolysis unit and the Sabatier reactor we can regulate hydrogen flow for a fraction of the mass regulating using batteries.

Ideally we want our Sabatier reactors running 24:39:35/7 to minimize maintenance.  Solar power is almost certain to be a major portion of the energy supply.  The problem is the sun doesn't shine at night.  In order to ensure we have hydrogen to operate 24:39:35/7 we need energy storage.  We can choose to store that energy before or after electrolysis losses.  Storing after electrolysis is preferable both mass, and, if done right, cost wise.

If that isn't enough there are other uses for hydrogen we will probably take with us to Mars.  Making ammonia with the Haber process gives a Martian colony the precursor to nitrogen fertilizer.  Methanol production is basically the same as methane production, but using carbon monoxide instead of carbon dioxide.  I did not include these in my previous post because I don't have the information to determine storage requirements.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/12/2019 07:16 am
The sabatier reaction can run continuously as long as there is hydrogen, it is exothermic. So produce enough hydrogen during sunlight hours. The question is does electrolysis too profit a lot from continuous operation? Enough to justify battery powered operation over night?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 11:58 am
Here is my table of energy/power requirements for a 1000 people colony that I made for the Mars society colony contest.  Basically 1 MW per 10 colonist.

Here is the colony design and all the spreadsheets.
https://sites.google.com/view/estepona-on-mars

So half the power is propellant production and 35% is greenhouses (I use artificially lit greenhouses).  The greenhouses are down at night as is fuel production, so power requirements go way way down.
Artificially lit greenhouses are mechanically cooled, since they required 300+watts per m2 of lighting (usual living area lighting is 10-20 W/m2).
The question then is what is the mass of Sabatier production vs the mass of energy storage.  And how energy intensive (lossy) is Sabatier with a night time shut down. Simplifying to a 12/24 production period vs 24/24 period, you need the same electrolysis equipment, but you can reduce Sabatier by 50% but then you need to  replace the mass with energy conversion and storage.

Globally, I think you want a well insulated base, since a poorly insulated base is extremely lossy, and is in real trouble if it loses power.  Now on Earth, you can't really loose the sun, but on Mars a power breakdown is bound to happen from time to time.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 12:05 pm
Well, Mars is cold, excess heat can heat the colony.  The gas turbine not only will turn a generator, but the heat from the burning methane can make steam for steam power also, then used to heat the colony where needed. 

I worked for a natural gas company before retirement.  We tried fuel cells, and other exotic means.  The turbine is 90+ efficient in electric production, then the heat is about 90%+ used to make more electricity through steam.  Gas turbine engines placed at coal fired replacement plants almost doubled power output by using both the mechanical production + the heat production of electricity in combination.
I think you may be overstating your case a bit.  Aren't combined gas cycles about 60-65% efficient overall?  There is a lot of heat that needs to be lost to close the cycle thermally, even if the individual elements are very efficient, as you rightly mention.
You are stuck with the carnot cycle efficiency, and the difference in temperature of the heat sinks.
Plus you would need some very large radiators on Mars as you can't run water cooling towers or cooling ponds on Mars.  The hotter your radiators, the smaller they are but the lower your system efficiency goes.
Not to forget storing the oxygen and then recompressing the combustion products to get the water and CO2 back.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/12/2019 12:30 pm
Methane is going to be produced regardless.  50% of solar power needed for methane production.  IF more methane is produced than needed for return rockets, then excess can burn in a gas turbine generator. 

Mars is cold, and heat will be needed at night to keep plants and people from freezing.  When people are sleeping at night, and electrical use is way down, then things will start cooling down. 

At night is when the gas turbine generator will burn producing electricity, as well as the excess heat from the exhaust will go into steam production producing more electricity.  Methane burns at about 1100 degrees F.  When making steam, most of the heat is extracted.  Exhaust is then cooled down to turn into steam and CO2.  CO2 goes to greenhouses or back into the Sabatier process.  Steam cools down by circulating into greenhouse heating and back to water reserves.  I was wrong about the efficiency.  The total efficiency from 40% from mechanical + heat(steam) recovery essentially doubles the efficiency for electrical production.  In theory up to 90% efficient.  All is not lost since excess heat is not wasted on the cold Martian nights.

Now, my idea is not a huge industrial size 747 jet engine, but a much smaller jet engine maybe even the size of a car engine.  My thoughs were the very low cost of installation of a turbine/steam generator, small size, and can be quickly put into use.  I also feel as if no excess heat will go to waste, but heat for large greenhouses will be needed to keep plants from freezing at night. 

Probably the only other way other than solar/battery, is a small nuclear power plant.  There are no known fossil fuels on Mars, and recently I read there may be methane on Mars, saving the energy from methane production.  Then there would be mining and extraction of the methane. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 01:18 pm
Methane is going to be produced regardless.  50% of solar power needed for methane production.  IF more methane is produced than needed for return rockets, then excess can burn in a gas turbine generator. 

Mars is cold, and heat will be needed at night to keep plants and people from freezing.  When people are sleeping at night, and electrical use is way down, then things will start cooling down. 

At night is when the gas turbine generator will burn producing electricity, as well as the excess heat from the exhaust will go into steam production producing more electricity.  Methane burns at about 1100 degrees F.  When making steam, most of the heat is extracted.  Exhaust is then cooled down to turn into steam and CO2.  CO2 goes to greenhouses or back into the Sabatier process.  Steam cools down by circulating into greenhouse heating and back to water reserves.  I was wrong about the efficiency.  The total efficiency from 40% from mechanical + heat(steam) recovery essentially doubles the efficiency for electrical production.  In theory up to 90% efficient.  All is not lost since excess heat is not wasted on the cold Martian nights.

Now, my idea is not a huge industrial size 747 jet engine, but a much smaller jet engine maybe even the size of a car engine.  My thoughs were the very low cost of installation of a turbine/steam generator, small size, and can be quickly put into use.  I also feel as if no excess heat will go to waste, but heat for large greenhouses will be needed to keep plants from freezing at night. 

Probably the only other way other than solar/battery, is a small nuclear power plant.  There are no known fossil fuels on Mars, and recently I read there may be methane on Mars, saving the energy from methane production.  Then there would be mining and extraction of the methane.
Energy is free.  Converting energy is what is expensive.
Even if we have methane on Mars, we need to separate enough oxygen from the atmosphere to burn it.  Then we need to run it through a combustion chamber, then through a gas turbine, then through a steam turbine, then through a condenser and then through some form of radiator.  The gas turbine and steam turbine turn turboalternators, and then we need transformers. These all require mass and expense, in particular the condenser will be a significant piece of steel, as far as I can guess.  As you know a gas plant is a massive piece of equipment when you include all the required support systems.
A nuclear reactor is also a massive piece of equipment, the core may be small but the steam  turbines (or gas turbine for a Brayton cycle), the coolers, the radiators and all the rest are not.
Solar photovoltaic power has the huge advantage that it has a very simple infrastructure, and that that cells have not finished being optimized. It can also be installed very close to point of use, so the system requirements are lower.  It forces the colony to follow the sun, however.  Good news, that is what plants have evolved for.  That is also what humans and animals have evolved for.  So following the sun is a 'natural' rhythm.
A colony (perhaps not a small exploratory base) will have significant thermal inertia, because it will be covered with a few meters or regolith, concrete or water for radiation protection.  It will also contain tonnes of atmosphere, tonnes of water and tonnes of walls, floors and structures.
A well insulated colony may lose as little as 1 degree per night.  That means it can essentially shut down for that period, and start heating again with the sun.  Just like we already do on Earth.
Forcing the colony to operate 24/24 is in fact pushing us into a mode of operation dictated by the equipment (power production likes a stable demand) rather than dictated by the colony needs.

That being said I can easily image a continuous production system for propellant production that uses a nuclear reactor and is separated form the colony varying load, operating 24/24.  That is what nuclear reactors are best at.
Title: Re: Power options for a Mars settlement
Post by: Tulse on 04/12/2019 01:47 pm
Even if we have methane on Mars, we need to separate enough oxygen from the atmosphere to burn it.  Then we need to run it through a combustion chamber, then through a gas turbine, then through a steam turbine, then through a condenser and then through some form of radiator.  The gas turbine and steam turbine turn turboalternators, and then we need transformers. These all require mass and expense, in particular the condenser will be a significant piece of steel, as far as I can guess.  As you know a gas plant is a massive piece of equipment when you include all the required support systems.
And, as implied above, such as system is also hugely mechanically complex.  In comparison, solar + batteries are essentially solid-state with no moving parts.  In a place where machining new parts is challenging, minimizing that problem for mission-critical power production would be vital to ensuring a robust system.

To be fair, a solar array that produced equivalent power to a gas turbine would also require a lot of mass, and take up an enormous area.  That's why I think its main advantage is mechanical simplicity.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/12/2019 01:56 pm
In-Glacier CAES

If a glacier is targeted for wells etc., some of the melt chambers might be repurposed for compressed air energy storage (CAES).  This would be a mass-efficient way to store energy overnight, as nearly all of the vessel mass is glacier ice.  Some energy is lost to the ice, but overnight I think losses would be low, even without vessel insulation.

Example:  In the clathrate thread a 10-atm LCH4 storage chamber (https://forum.nasaspaceflight.com/index.php?topic=44508.msg1934407#msg1934407) was envisioned (right). 

(http://www.lakematthew.com/wp-content/uploads/2017/12/MiningAndStorage_medres.png)

In the cartoon the pressurized storage chamber has an illustrative volume of ~ 800,000 m3 and pressure of 10 atm.  We might take 0.1 atm as the ambient pressure of waste gas (mostly CO2) stored in disused wells across the mine.  These could be first-pass numbers for a parallel CAES system.

Worth a calc?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 02:21 pm
In-Glacier CAES

If a glacier is targeted for wells etc., some of the melt chambers might be repurposed for compressed air energy storage (CAES).  This would be a mass-efficient way to store energy overnight, as nearly all of the vessel mass is glacier ice.  Some energy is lost to the ice, but overnight I think losses would be low, even without vessel insulation.

Example:  In the clathrate thread a 10-atm LCH4 storage chamber (https://forum.nasaspaceflight.com/index.php?topic=44508.msg1934407#msg1934407) was envisioned (right). 


In the cartoon the pressurized storage chamber has an illustrative volume of ~ 800,000 m3 and pressure of 10 atm.  We might take 0.1 atm as the ambient pressure of waste gas (mostly CO2) stored in disused wells across the mine.  These could be first-pass numbers for a CAES system.

Worth a calc?
Certainly worth a calc.  The question then become how expensive is Martian oxygen, energy wise?  Oxygen is such a ridiculously good oxidizer, breaking that bond always takes a lot of energy.
In fact, since the Sabatier reaction is exothermic, as CH4 has less intrinsic energy than H2, might it be argued that the methane is essentially useless as a propellant source, since liberating the oxygen requires as much energy as the propellant will be able to give back?
I guess there may be ways of getting the O2 out of CO2 that require less energy than electrolysis?  Or can the 0,13% of free oxygen in the martian atmosphere be compressed out into a useful resource?
Perhaps this was answered in the clathrate thread?
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 04/12/2019 04:06 pm
Moxie?
CO2-> O2 + CO
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 04:27 pm
Moxie?
CO2-> O2 + CO
Moxie use 300W to produce 10g/hr.  Or 300 J/s x 3600 = 1 MJ/10g, or 100 MJ/kg
https://mars.nasa.gov/mars2020/mission/instruments/moxie/

Electrolysis is 180 MJ/kg of hydrogen, H2O, 2 + 16 so that's 180/8 = 22 MJ/kg O2.   
https://en.wikipedia.org/wiki/Electrolysis_of_water#Industrial_output

Nope, not Moxie.  Industrial electrolysis wins.  Unless I got my numbers wrong.  Happens  ;-)
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/12/2019 04:45 pm
Solar power is almost certain to be a major portion of the energy supply.  The problem is the sun doesn't shine at night.  In order to ensure we have hydrogen to operate 24:39:35/7 we need energy storage...

Your logic is sound. It's your assumptions that I question.

As I said before, solar and nuclear tend to complement one another, not only in terms of meeting the demand curve, but also for redundancy.
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/12/2019 05:36 pm
Seems to me the answer is all of the above.

Start with solar to generate electricity. Batteries and/or hydrogen storage to keep sabatier running steady state. Add nuclear when it becomes available (at which point the batteries/hydrogen storage become less critical). Bring an emergency backup generator that can run on methane and oxygen to use when all else fails. Make sure that all of your plant can cope with changing things around (that is, that your process cycle should not be resistant to changing the timing of energy input)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 05:49 pm
Seems to me the answer is all of the above.

Start with solar to generate electricity. Batteries and/or hydrogen storage to keep sabatier running steady state. Add nuclear when it becomes available (at which point the batteries/hydrogen storage become less critical). Bring an emergency backup generator that can run on methane and oxygen to use when all else fails. Make sure that all of your plant can cope with changing things around (that is, that your process cycle should not be resistant to changing the timing of energy input)
So running the Sabatier reaction all night actually requires very little power as it is exothermic.  You produce the hydrogen during the day and consume it both during the day and during the night for incorporation into CH4.  No hydrogen burning at all.  So that way the Sabatier equipment is the smallest possible, you just need a way to store half a day's worth of hydrogen.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 04/12/2019 06:01 pm
With no crew the first systems will need to be self contained probably less efficient then an optimized ones. 
The first missions may test different processes to see what works. 
All with different power requirements. 
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 04/12/2019 06:15 pm
 Four month long dust storms seem to be getting treated as something to be planned for after the power design is set. Not a good philosophy. With the inability to return home without full tanks an bi-yearly windows, they need to be first line factors in the design.
 Granted, it makes everything a lot harder, but planning on the assumption that the weather will cooperate is a well paved road to disaster.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/12/2019 06:40 pm
Four month long dust storms seem to be getting treated as something to be planned for after the power design is set. Not a good philosophy. With the inability to return home without full tanks an bi-yearly windows, they need to be first line factors in the design.
 Granted, it makes everything a lot harder, but planning on the assumption that the weather will cooperate is a well paved road to disaster.
I agree.  It is certain the weather will not cooperate.  But what we need to plan for is a reduction in supplies and colonists if there is a long dust storm, not the inability to return home.  The colony must always have enough current supplies to outlast a dust storm.

The return fuel must be present before we send the ships to Mars.  for that purpose they need to unload quickly and return.  The supplies sent must match the return fuel.  If there is very little fuel, then send only essential supplies, if there is a full fuel load send a full complement of colonists.
If you have nuclear then this is not a constraint, but for a solar only colony I think this is the way to go.

The colony will need to produce fuel for crewed ships but also for a much larger number of cargo ships.  Anything from 3:1 to 10:1, depending on how well things go.  So there is a wide safety margin there as well.

With any luck nuclear reactor of adequate power and cost will exist in time.  But if not, we shouldn't give up on the idea of a colony, we just need to have an adaptable plan.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/12/2019 08:36 pm
One thing seems clear to me, they will need to take huge quantities of the most efficient solar panels possible on every ship to help ensure there is always enough power. And follow that up with nuclear power as soon as it becomes available.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/12/2019 09:33 pm
Four month long dust storms seem to be getting treated as something to be planned for after the power design is set. Not a good philosophy. With the inability to return home without full tanks an bi-yearly windows, they need to be first line factors in the design.
 Granted, it makes everything a lot harder, but planning on the assumption that the weather will cooperate is a well paved road to disaster.

If you have a means to produce emergency power from methane and LOX the worst thing that can happen is a cargo ship needs to stay on Mars. The one contingency to plan for is first arrival of people on Mars. If arrival coincides with a major dust storm and there is no stored propellant that's a problem. If they arrive after the dust storm season is over they have plenty of time to produce methane and LOX. We need to know how arrival in 2024 or 2026 correlate to dust storm season.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/13/2019 02:50 am
The sabatier reaction can run continuously as long as there is hydrogen, it is exothermic. So produce enough hydrogen during sunlight hours. The question is does electrolysis too profit a lot from continuous operation?

An electrode with a 22 g/m^2 99.99 pure platinum coating is sufficient for a full synod with restarts.  Avoiding restarts to save on coating should take this down to 19-20 g/m^2.  Platinum is currently trading around $30,000/kg.  A single kg should cover the difference for decades.  This is a problem that can easily be solved by spending a couple grand on Earth per synod.

Quote
Enough to justify battery powered operation over night?

Not anywhere near close.  Batteries, additional solar panels(we must account for storing electrolysis losses), better power lines, and other associated bits are going to mass on the order of 40 tonnes.

The primary limiting factor on electrolysis unit maintenance periods is impurities in the water supply.  Sure, we can drain the unit and replace the water, but crude builds up.  If you want to spend 38.5* tonnes of mass budget increasing electrolysis unit maintenance periods, improve water purification.

* 40 tonne battery concept mass estimate minus 1,500 kg for tank stretches to add hydrogen storage.**

**  I am waiting for the inevitable, "You need more than tank stretches to add hydrogen storage!!!"  While I could explain the why now, I'm curious what subsystems others are imagining.

Edit: Fixed quotes
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/13/2019 03:05 am
Certainly worth a calc.  The question then become how expensive is Martian oxygen, energy wise?  Oxygen is such a ridiculously good oxidizer, breaking that bond always takes a lot of energy.

The Martian surface appears to be covered in perchlorates, another ridiculously good oxidizer.  I'm thinking dump some dirt in a black tank of water, stir, then let the water evaporate to a condensing loop(and another tank).  The result a crust of salts that are easy to scrap off robotically.
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/13/2019 08:10 am
Four month long dust storms seem to be getting treated as something to be planned for after the power design is set. Not a good philosophy. With the inability to return home without full tanks an bi-yearly windows, they need to be first line factors in the design.
 Granted, it makes everything a lot harder, but planning on the assumption that the weather will cooperate is a well paved road to disaster.

One "nice" thing is that the power used to produce methane and oxygen for the return home is vastly greater than the power used for everything else.  The number I've heard is ~1 megawatt.  However, I would be surprised if it took more than a few 10's of kilowatts to run life support for a dozen or so colonists.

This means that in the case of a dust storm, your methane reserves will go a long way.  Also, if your solar panels are able to produce just a few percent of their normal output level, it's enough to keep everyone alive.  A good option is to send a couple insulated tanker variant Starships down initially.  That gives them enough initial fuel reserve to last for a very long time, and if all goes well, they're going to need the tanks to store what they produce anyway.

The big contingency is if the dust storm keeps their methane production shut down for long enough for them to miss their return window.  They're going to have to have enough supplies to last an extra 2 years, just in case.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/13/2019 12:54 pm
Certainly worth a calc.  The question then become how expensive is Martian oxygen, energy wise?  Oxygen is such a ridiculously good oxidizer, breaking that bond always takes a lot of energy.

The Martian surface appears to be covered in perchlorates, another ridiculously good oxidizer.  I'm thinking dump some dirt in a black tank of water, stir, then let the water evaporate to a condensing loop(and another tank).  The result a crust of salts that are easy to scrap off robotically.
Or better still let the suspended solids settle then pump the water out and let it evaporate in a separate tank. Incidentaly there are bacteria that can reduce perchlorate to oxygen. Just need to add the right enzymes to the black tank and oxygen would be given off, although unfortunately only in relatively small quantities so unlikely to be of great use.
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 04/13/2019 01:07 pm
 Instead of waiting 20 years for someone else to screw around with multi megawatt heatpipe reactors it might be time for Elon inc. to branch out again. Krusty features like self regulation and nothing to wear out but easily replaceable Sterlings would make it a pretty good option. About the only thing they'd have a hard time eventually doing on Mars is the fuel elements.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/13/2019 02:30 pm
Instead of waiting 20 years for someone else to screw around with multi megawatt heatpipe reactors it might be time for Elon inc. to branch out again. Krusty features like self regulation and nothing but easily replaceable Sterlings to wear out would make it a pretty good option. About the only thing they'd have a hard time eventually doing on Mars is the fuel elements.
In a talk in 2017 Shotwell mentioned that they had tried to get some nuclear material for experiments but that the regulations were too restrictive.  So they wanted to but couldn’t.
Will likely be kilopower and its descendants. Or buy from the Chinese ;-)
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/13/2019 03:04 pm
Given Musk's recent comment on a path to self sufficiency, I think it's important to consider not just initial power sources brought from Earth, but also ones produced entirely on Mars.

A very important is energy cost of power sources. (E.g. the energy payback period of solar panels).

For example suppose a Watt power source requires 2 Watt-years to build.

Suppose you already have a 1 GWatt source you brought from earth, and you want to grow to 8 GWatts self sufficiently.

Suppose you can set aside 50% of your GWatt for making new solar panels.  In order to make another GWatt, you need to wait 4 years.

So to enable a doubling every 4 years, you need to have a technology that has a 2-yr energy payback time, and give up 50% of your power.  This gets worse quickly as the payback period increases.

2 years payback is not easy. Mars has low insolation (doubling the period as measured on Earth), and fabrication techniques can't take advantage of truly mass-scale technology from Earth. Also, unlike on earth, every bit of plastic and metal costs ISRU energy much more than it costs on Earth.

So which power production technology costs the least, energy wise?
Title: Re: Power options for a Mars settlement
Post by: Jcc on 04/13/2019 04:43 pm
You have to consider that some portion of any technology for energy expansion will have to come from Earth on future cargo flights. The question is how to optimize the ISRU component in order to maximize energy expansion over time. For instance, does it make sense to bring in machinery and "ingredients" to grow photovoltaic crystals, or just import the cells and mount them on substrate produced from locally sourced materials, such as glass and iron. Would it make sense to use iron alloys for electrical conductors instead of copper if copper is not available?

There are a million questions to ask as to how to optimize investment in materials and energy, but I think that when the prospect of actually starting a Mars colony becomes real to people there will be many projects in academia and industry to try to answer those questions.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/13/2019 06:49 pm
Instead of waiting 20 years for someone else to screw around with multi megawatt heatpipe reactors it might be time for Elon inc. to branch out again. Krusty features like self regulation and nothing but easily replaceable Sterlings to wear out would make it a pretty good option. About the only thing they'd have a hard time eventually doing on Mars is the fuel elements.
In a talk in 2017 Shotwell mentioned that they had tried to get some nuclear material for experiments but that the regulations were too restrictive.  So they wanted to but couldn’t.
Will likely be kilopower and its descendants. Or buy from the Chinese ;-)
I still say SPARC and ARC will be more accessable options, if we can just get a 15m reactor demonstrator to Mars when they start to come online in 10-15 years.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/13/2019 08:09 pm
You have to consider that some portion of any technology for energy expansion will have to come from Earth on future cargo flights. The question is how to optimize the ISRU component in order to maximize energy expansion over time. For instance, does it make sense to bring in machinery and "ingredients" to grow photovoltaic crystals, or just import the cells and mount them on substrate produced from locally sourced materials, such as glass and iron. Would it make sense to use iron alloys for electrical conductors instead of copper if copper is not available?

There are a million questions to ask as to how to optimize investment in materials and energy, but I think that when the prospect of actually starting a Mars colony becomes real to people there will be many projects in academia and industry to try to answer those questions.

Initially, yes, and that's a different discussion, best titled "how to bootstrap power production".

But when Musk is talking about self sufficiency, the metrics change.

It's not "which question is correct", it's just two separate discussions.  One is pertinent to the first 10 synods, and the next takes over afterwards - obviously with some significant overlap.

In the first discussion, you try to minimize mass brought in from Earth, because that's likely the bottleneck.  (with the caveat that you also try to minimize energy usage on Mars, even if you have to lug some components all the way from Earth).

In the second discussion, the transport element is out.  You want to fabricate a GWatt power production capacity on Mars, while expending as little energy (GWatt-yrs) as possible.  Mass no longer matters.

For example, on Mars, plastics will be derivatives of the CH4 foodchain, whereas metals might be more easily obtainable from the ground for less energy, in which case the term "cheap plastic parts" might not have a direct translation to Martian.

Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 04/13/2019 10:20 pm
The one contingency to plan for is first arrival of people on Mars. If arrival coincides with a major dust storm and there is no stored propellant that's a problem. If they arrive after the dust storm season is over they have plenty of time to produce methane and LOX.

I expect that the first people to go to Mars won't even be allowed to set off until it is known that there is sufficient stored propellant on Mars for the return.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/13/2019 10:46 pm
The one contingency to plan for is first arrival of people on Mars. If arrival coincides with a major dust storm and there is no stored propellant that's a problem. If they arrive after the dust storm season is over they have plenty of time to produce methane and LOX.

I expect that the first people to go to Mars won't even be allowed to set off until it is known that there is sufficient stored propellant on Mars for the return.

I bet it's the opposite.  What you're describing is "ISRU first", which requires some very significant robotics to set up solar power and possibly ice mining.

The other option is "Boots First", which means they arrive there to find supplies and an ISRU plant still in boxes, but there's a plan to keep them supplied using more ships if they are unable to set up ISRU.   (Basically, the follow-on window will be all-cargo instead of cargo/people)

I think SpaceX is planning to use "Boots First"
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 04/14/2019 01:48 am
The one contingency to plan for is first arrival of people on Mars. If arrival coincides with a major dust storm and there is no stored propellant that's a problem. If they arrive after the dust storm season is over they have plenty of time to produce methane and LOX.

I expect that the first people to go to Mars won't even be allowed to set off until it is known that there is sufficient stored propellant on Mars for the return.

I bet it's the opposite.  What you're describing is "ISRU first", which requires some very significant robotics to set up solar power and possibly ice mining.

The other option is "Boots First", which means they arrive there to find supplies and an ISRU plant still in boxes, but there's a plan to keep them supplied using more ships if they are unable to set up ISRU.   (Basically, the follow-on window will be all-cargo instead of cargo/people)

I think SpaceX is planning to use "Boots First"
Gotta agree. Getting everything done by robotics is still science fiction. Right now, they can spend two years figuring out how to make a rock drill work when something doesn't go as planned. Filling a tank with methane will be a little harder than that.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/14/2019 04:03 am
The one contingency to plan for is first arrival of people on Mars. If arrival coincides with a major dust storm and there is no stored propellant that's a problem. If they arrive after the dust storm season is over they have plenty of time to produce methane and LOX.

I expect that the first people to go to Mars won't even be allowed to set off until it is known that there is sufficient stored propellant on Mars for the return.

I bet it's the opposite.  What you're describing is "ISRU first", which requires some very significant robotics to set up solar power and possibly ice mining.

The other option is "Boots First", which means they arrive there to find supplies and an ISRU plant still in boxes, but there's a plan to keep them supplied using more ships if they are unable to set up ISRU.   (Basically, the follow-on window will be all-cargo instead of cargo/people)

I think SpaceX is planning to use "Boots First"

From Elon's IAC 2017 slides:
Title: Re: Power options for a Mars settlement
Post by: geza on 04/14/2019 05:25 am
About Opportunity power crisis: "The rover's energy production dropped by half over the course of two days, and then half again in a single day" form here:
https://dailygalaxy.com/2018/06/nasa-will-opportunity-survive-mars-dust-storm-atmospheric-opacity-twice-as-high-as-ever-recorded/

That is, dust storm can cause much deeper power drop, than a factor of two. I did not find something more definite on the subject.

Yes, Boots First is the way SpaceX considers. Some robotic solar panel deployment is inevitable "before boots" for thermal control of the cargo landers and the for the surface exploration/experimentation. As a minimum, they will have to experiment with ISRU using imported water and, separately, with regolith mining and water extraction. For this they will need a rover capable of autonomously recharging themselves.

The sentence "Place power, mining and life support infrastructure." seems to indicate a little more before boots: deployment and validation of sufficient water production (therefore, oxigen production) capacity to help out the not-fully-closed life support system of the crew ships. Probably, the cargo landers deploy enough PV to power the crew landers upon arrival without further deployment. If so, the first crew will arrive when they long-term survival on the surface is guaranteed, if resupplied with food and spare parts in each synods.

That is, Elon's slide seems to indicate that the whole system of water production will be robotically deployed, but a much smaller scale than is needed for fuel production.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/14/2019 11:24 am
Yes, Boots First is the way SpaceX considers. Some robotic solar panel deployment is inevitable "before boots"...

The sentence "Place power, mining and life support infrastructure." seems to indicate a little more before boots: deployment and validation of sufficient water production (therefore, oxygen production) capacity to help out the not-fully-closed life support system of the crew ships. Probably, the cargo launders deploy enough PV to power the crew landers upon arrival without further deployment...

I read it differently.

The slide (https://amp.businessinsider.com/images/59ef673e9099243b2b8b4f2b-1334-750.jpg) says:
Quote from: Elon Musk's IAC 2017 slides
2022: CARGO MISSIONS
 - Land at least 2 cargo ships on Mars
 - Confirm water resources and identify hazards
 - Place power, mining and life support infrastructure for future flights

2024: CARGO & CREW MISSIONS
 - 2 crew ships take first people to Mars
 - 2 cargo ships bring more equipment and supplies
 - Set up propellant production plant
 - Build up base to prepare for expansion
(emphasis mine)

To me, the word "place" implies that they get it there, i.e. land it on the Mars surface. If they intended to deploy the power system on the first mission, I suspect the slide would have said something like "set up" or "build".

For the water resources slide bullet, he uses the words "confirm" and "identify".
Also, the site where I found the slide includes a full transcript (https://www.businessinsider.com/elon-musk-mars-iac-2017-transcript-slides-2017-10#-35) of Elon's presentation. When this slide was shown, Elon said:
Quote from: Elon Musk's IAC 2017 transcript
The goal of these initial missions is to find the best source of water — that's for the first mission. And then for the second mission, the goal is to build the propellant plant.

Again, if Elon meant that they indented to start "deployment and validation of sufficient water production" on the first mission, I don't think he would have used words like "find".

Rather, I suspect SpaceX's plan for the first mission includes one or more robotic rovers that will take samples and investigate the area. This may include some drilling, but I don't think it would include any deployment of water production systems. That would be for the second mission.

But as always, this is subject to interpretation.
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/14/2019 03:50 pm
They might plan to achieve only find, but if there is a little spare tonnage, maybe add some additional capability, whatever advances things...
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/14/2019 04:25 pm
To confirm water resources means some digging. Which needs power for the rovers/mining droids. So they will have to deploy at least some solar arrays. I expect while they are at it they would deploy at least enough to supplie the first manned landers. Ideally all the arrays, enough to begin propellant production soon after arrival of humans.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/14/2019 05:21 pm
Yes, Boots First is the way SpaceX considers. Some robotic solar panel deployment is inevitable "before boots"...

The sentence "Place power, mining and life support infrastructure." seems to indicate a little more before boots: deployment and validation of sufficient water production (therefore, oxygen production) capacity to help out the not-fully-closed life support system of the crew ships. Probably, the cargo launders deploy enough PV to power the crew landers upon arrival without further deployment...

I read it differently.

The slide (https://amp.businessinsider.com/images/59ef673e9099243b2b8b4f2b-1334-750.jpg) says:
Quote from: Elon Musk's IAC 2017 slides
2022: CARGO MISSIONS
 - Land at least 2 cargo ships on Mars
 - Confirm water resources and identify hazards
 - Place power, mining and life support infrastructure for future flights

2024: CARGO &amp; CREW MISSIONS
 - 2 crew ships take first people to Mars
 - 2 cargo ships bring more equipment and supplies
 - Set up propellant production plant
 - Build up base to prepare for expansion
(emphasis mine)

To me, the word "place" implies that they get it there, i.e. land it on the Mars surface. If they intended to deploy the power system on the first mission, I suspect the slide would have said something like "set up" or "build".

For the water resources slide bullet, he uses the words "confirm" and "identify".
Also, the site where I found the slide includes a full transcript (https://www.businessinsider.com/elon-musk-mars-iac-2017-transcript-slides-2017-10#-35) of Elon's presentation. When this slide was shown, Elon said:
Quote from: Elon Musk's IAC 2017 transcript
The goal of these initial missions is to find the best source of water — that's for the first mission. And then for the second mission, the goal is to build the propellant plant.

Again, if Elon meant that they indented to start "deployment and validation of sufficient water production" on the first mission, I don't think he would have used words like "find".

Rather, I suspect SpaceX's plan for the first mission includes one or more robotic rovers that will take samples and investigate the area. This may include some drilling, but I don't think it would include any deployment of water production systems. That would be for the second mission.

But as always, this is subject to interpretation.
I read it the same - simply place them by landing there.

I can see a rover or two with drilling equipment that can be stowed at one of the lower bays, but that's about it.

For power, it can recharge at SS. SS can either deploy some panels up top, or also run a fuel cell on extra propellant.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/14/2019 05:55 pm
To confirm water resources means some digging.

Or drilling. That's what they usually do when mining on Earth, i.e. drill around various places to find the areas with the richest deposits of whatever they're mining. Here's an example (https://www.charlotteobserver.com/news/business/article228475629.html?fbclid=IwAR1CzVFS2kA7sdu9G7UpIII9seLf10SYAkEWapaISWAuQgN2J_qq2_b4DSk) of that.

In any case, it seems clear that SpaceX's Mars plans are somewhat risky. The NASA Mars plans I've heard about always had IRSU up and running with enough fuel to return to Earth before even considering a crew launch. It's clear SpaceX's current plans don't include that.

And that's not necessarily a bad thing. I think we've been far too risk averse in human space flight recently.

With this in mind, I think it's possible that SpaceX plans for the first people who land on Mars to set up the solar arrays themselves. And the batteries for supplying power at night. A lot of batteries. And if those batteries arrive on one of the first 2 cargo Starships, maybe they can provide power to the rovers that are scouting for water before any crew arrive.

Of course, this assumes the Mars plans that Elon showed at IAC 2017 won't change, which is highly questionable.
As BFR starts getting real, someone may want to partner with SpaceX for the first mission, e.g. NASA, some billionaire, or some other company. That could change SpaceX's plans significantly.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/14/2019 06:23 pm
To confirm water resources means some digging.

Or drilling.

Elon Musk used the term mining droids consistently. Paul Wooster, in charge of Mars surface operations used the same term, showed a slide with the droids and strip mining to get to the ice. I stick with digging for water.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/14/2019 06:36 pm
It seems that it would be very useful to have two Starships landed next to each other to simplify sharing of resources such as power, ISRU facilities, batteries and making other cargo more easily accessible.

However I'm not sure it will be that easy. When a Starship lands it will blast dust sand and rock over a wide distance. Landing close to another Starship risks damaging it with debris as well as damaging and or blowing away any existing deployed solar array.

The second Starship could land 1-2km away which would eliminate blast damage, but then there’s the problem of cables and pipes for sharing power and propellants over an extended distance.
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/14/2019 06:48 pm
I would really expect them to initially land somewhere where there's surface ice available.  Drilling sounds too complex and with too many unknowns for a first landing. Surface ice can just be collected with an excavator and a dump truck.

As far as landing without ISRU success guarenteed, I imagine that for the first flight, they'll just land some tankers at the site.  Enough fuel to leave if things don't work out, and it gives them storage tanks for what they do produce, which is also useful.  The tankers would be designed for long term fuel storage with insulated walls.

Once ISRU production is up and running and they've built up a fuel reserve, they won't have to keep sending tankers any more.

I don't think we should count on the early cargo and fuel vehicles to ever return from Mars.  They'll be useful there, though.  Structures are going to be in short supply for a while.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/14/2019 07:29 pm
To confirm water resources means some digging.

Or drilling.

Elon Musk used the term mining droids consistently. Paul Wooster, in charge of Mars surface operations used the same term, showed a slide with the droids and strip mining to get to the ice. I stick with digging for water.

For sure, people won't be shoveling by hand, at least not usually...

And it's within today's automation to tell a mining drone to "dig a hole of diameter X at location Y".

What's not possible with autonomous machines is to deal with exceptions.  So every so often a person has to intervene.

What's also hard to do is to assemble.  Even assembling cars is difficult to do, not to mention doing the wiring and piping of a power/ISRU station.

They only have one year after landing before they have to decide if the next launch is crew/cargo or just cargo to help the first crew survive)

Within this year, the pilot crew (20 ppl?) have to build a MWatt+ power/ISRU plant.  That's a LOT of work, and they must use a lot of automation. 

With some effort, you can set up some autonomous operation that's beyond just "rove and drill", like maybe "prepare a flat landing pad" or "place beacons" - but that's still way below the bar of "ISRU first".

Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/15/2019 01:53 am
Within this year, the pilot crew (20 ppl?) have to build a MWatt+ power/ISRU plant.  That's a LOT of work...
Yes.

I'm starting to realize how rough it may be for the first crew with SpaceX's plan. They'll have to build the first infrastructure. Future crew missions can expand this infrastructure, but they'll have the original infrastructure to support that expansion. The first crew will be doing it from scratch.
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/15/2019 02:14 am
To confirm water resources means some digging.

Or drilling.

Elon Musk used the term mining droids consistently. Paul Wooster, in charge of Mars surface operations used the same term, showed a slide with the droids and strip mining to get to the ice. I stick with digging for water.

For sure, people won't be shoveling by hand, at least not usually...

And it's within today's automation to tell a mining drone to "dig a hole of diameter X at location Y".

What's not possible with autonomous machines is to deal with exceptions.  So every so often a person has to intervene.

What's also hard to do is to assemble.  Even assembling cars is difficult to do, not to mention doing the wiring and piping of a power/ISRU station.

They only have one year after landing before they have to decide if the next launch is crew/cargo or just cargo to help the first crew survive)

Within this year, the pilot crew (20 ppl?) have to build a MWatt+ power/ISRU plant.  That's a LOT of work, and they must use a lot of automation. 

With some effort, you can set up some autonomous operation that's beyond just "rove and drill", like maybe "prepare a flat landing pad" or "place beacons" - but that's still way below the bar of "ISRU first".

Honestly, I'd consider digging a hole to be a very difficult robotics problem.  It needs to be able to recognize and dig around chunks of rock and boulders (of which there are plenty on Mars), avoid getting stuck, avoid collapsing a hill on itself, navigate complex and changing (it is digging, after all) terrain, and so forth.

I don't think our current AI and robotics are up to it, frankly.

Assembling things is easy in comparison.  Even though it looks more complicated, it's just repeating a pattern over and over.  Predictable, does not require spatial reasoning.

There's a huge disconnect between what animals like us are good at and what computers and robots are good at.  A human can effortlessly walk through the woods, occasionally climbing over obstacles that get in our way or pushing through a thicket.  This is beyond the state of the art in robotics.  Conversely, a robot can absolutely crush any human in a game of chess.  It just goes to show how specialized our brains are at dealing with the sorts of tasks animals have to deal with to live their day to day lives.  We're so good at these things that we have convinced ourselves that they're easy.  But they aren't.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/15/2019 02:17 am
To confirm water resources means some digging.

Or drilling.

Elon Musk used the term mining droids consistently. Paul Wooster, in charge of Mars surface operations used the same term, showed a slide with the droids and strip mining to get to the ice. I stick with digging for water.

For sure, people won't be shoveling by hand, at least not usually...

And it's within today's automation to tell a mining drone to "dig a hole of diameter X at location Y".

What's not possible with autonomous machines is to deal with exceptions.  So every so often a person has to intervene.

What's also hard to do is to assemble.  Even assembling cars is difficult to do, not to mention doing the wiring and piping of a power/ISRU station.

They only have one year after landing before they have to decide if the next launch is crew/cargo or just cargo to help the first crew survive)

Within this year, the pilot crew (20 ppl?) have to build a MWatt+ power/ISRU plant.  That's a LOT of work, and they must use a lot of automation. 

With some effort, you can set up some autonomous operation that's beyond just "rove and drill", like maybe "prepare a flat landing pad" or "place beacons" - but that's still way below the bar of "ISRU first".

Honestly, I'd consider digging a hole to be a very difficult robotics problem.  It needs to be able to recognize and dig around chunks of rock and boulders (of which there are plenty on Mars), avoid getting stuck, avoid collapsing a hill on itself, navigate complex and changing (it is digging, after all) terrain, and so forth.

I don't think our current AI and robotics are up to it, frankly.

Assembling things is easy in comparison.  Even though it looks more complicated, it's just repeating a pattern over and over.  Predictable, does not require spatial reasoning.

There's a huge disconnect between what animals like us are good at and what computers and robots are good at.  A human can effortlessly walk through the woods, occasionally climbing over obstacles that get in our way or pushing through a thicket.  This is beyond the state of the art in robotics.  Conversely, a robot can absolutely crush any human in a game of chess.  It just goes to show how specialized our brains are at dealing with the sorts of tasks animals have to deal with to live their day to day lives.  We're so good at these things that we have convinced ourselves that they're easy.  But they aren't.
Digging is, no argument.

You can tell it to start, and it'll do fine for a day, and then something will go wrong, and if you're lucky it'll recognize it, stop, and wait for assistance before you need another tractor to bail it out.

Even human operators fail in that...
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/15/2019 02:28 am
<snips>

Honestly, I'd consider digging a hole to be a very difficult robotics problem.  It needs to be able to recognize and dig around chunks of rock and boulders (of which there are plenty on Mars), avoid getting stuck, avoid collapsing a hill on itself, navigate complex and changing (it is digging, after all) terrain, and so forth.

I don't think our current AI and robotics are up to it, frankly.

Assembling things is easy in comparison.  Even though it looks more complicated, it's just repeating a pattern over and over.  Predictable, does not require spatial reasoning.

There's a huge disconnect between what animals like us are good at and what computers and robots are good at.  A human can effortlessly walk through the woods, occasionally climbing over obstacles that get in our way or pushing through a thicket.  This is beyond the state of the art in robotics.  Conversely, a robot can absolutely crush any human in a game of chess.  It just goes to show how specialized our brains are at dealing with the sorts of tasks animals have to deal with to live their day to day lives.  We're so good at these things that we have convinced ourselves that they're easy.  But they aren't.
Digging is, no argument.

You can tell it to start, and it'll do fine for a day, and then something will go wrong, and if you're lucky it'll recognize it, stop, and wait for assistance before you meed another tractor to bail it out.

Even human operators fail in that...

I won't even give it a day.  Five minutes and it'll by trying to bash its shovel into a chunk of rock too big to move.  Regolith is likely to be a headache even for human operators!
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/15/2019 02:52 am
I won't even give it a day.  Five minutes and it'll by trying to bash its shovel into a chunk of rock too big to move.  Regolith is likely to be a headache even for human operators!

Quote from: Stephen Clark, Spaceflight Now
InSight scientists not sure stalled Mars heat probe can be recovered (https://spaceflightnow.com/2019/04/03/insight-scientists-not-sure-stalled-mars-heat-probe-can-be-recovered/)

April 3, 2019

Ground teams analyzing data from a heat probe that got stuck soon after it started digging into the Martian crust under NASA’s robotic InSight lander still hope they can free the mole from an obstruction that halted its progress more than a month ago, but the mission’s chief scientist says the chances of completing the heat probe experiment — one of InSight’s two main science instruments — may not look promising.

(https://mk0spaceflightnoa02a.kinstacdn.com/wp-content/uploads/2019/04/D000M0118_607019065EDR_F0000_0250M_-678x678.jpg)
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/15/2019 03:44 am
Well one thing that will be different about any SpaceX surface equipment is power.

With a SS nearby as a power source, rover can have much larger motors and battery packs.

A lot of the difficulty encountered by NASA's rovers is due to the fact that they are science probes  not bulldozers ...

Whether manned, autonomous or remote-operated, expect to see things like bobcats and mini excavators show up.
Title: Re: Power options for a Mars settlement
Post by: Lemurion on 04/15/2019 04:00 am
The more I see in this thread, the more I keep coming back to the importance of the question of time: Which options they deploy are going to depend on where they are in the timeline.

Everything is going to build out from an initial infrastructure of solar cells backed by batteries. We are currently sitting approximately five years out from the aspirational dates for Mars launches and that's the technology SpaceX has. The only catch here is the fear that major dust storms could kill solar for long periods of time. I personally think the way SpaceX is likely to approach this is by having so much capacity that they can just shut down ISRU and run life-support on the reduced capacity even if they have to EVA with push brooms every day.

Nuclear would be nice for a backup, but I don't know that SpaceX can swing either the technology or the politics in time.

Methane combustion sounds attractive, and I think it's possible but I don't know that SpaceX has done the necessary homework to get it running in time.

I would love to see more power flexibility but I think the law of diminishing returns is going to largely limit things to what's already available for at least the first few synods.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/15/2019 10:26 am
To confirm water resources means some digging.

Or drilling.

Elon Musk used the term mining droids consistently. Paul Wooster, in charge of Mars surface operations used the same term, showed a slide with the droids and strip mining to get to the ice. I stick with digging for water.

For sure, people won't be shoveling by hand, at least not usually...

And it's within today's automation to tell a mining drone to "dig a hole of diameter X at location Y".

What's not possible with autonomous machines is to deal with exceptions.  So every so often a person has to intervene.

What's also hard to do is to assemble.  Even assembling cars is difficult to do, not to mention doing the wiring and piping of a power/ISRU station.

They only have one year after landing before they have to decide if the next launch is crew/cargo or just cargo to help the first crew survive)

Within this year, the pilot crew (20 ppl?) have to build a MWatt+ power/ISRU plant.  That's a LOT of work, and they must use a lot of automation. 

With some effort, you can set up some autonomous operation that's beyond just "rove and drill", like maybe "prepare a flat landing pad" or "place beacons" - but that's still way below the bar of "ISRU first".
I doubt the first crew will be 20. The weight of the people, consumables and kit alone would be more than 50 tons assuming a 900 day mission.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/15/2019 12:11 pm
To confirm water resources means some digging.

Or drilling.

Elon Musk used the term mining droids consistently. Paul Wooster, in charge of Mars surface operations used the same term, showed a slide with the droids and strip mining to get to the ice. I stick with digging for water.

For sure, people won't be shoveling by hand, at least not usually...

And it's within today's automation to tell a mining drone to "dig a hole of diameter X at location Y".

What's not possible with autonomous machines is to deal with exceptions.  So every so often a person has to intervene.

What's also hard to do is to assemble.  Even assembling cars is difficult to do, not to mention doing the wiring and piping of a power/ISRU station.

They only have one year after landing before they have to decide if the next launch is crew/cargo or just cargo to help the first crew survive)

Within this year, the pilot crew (20 ppl?) have to build a MWatt+ power/ISRU plant.  That's a LOT of work, and they must use a lot of automation. 

With some effort, you can set up some autonomous operation that's beyond just "rove and drill", like maybe "prepare a flat landing pad" or "place beacons" - but that's still way below the bar of "ISRU first".
I doubt the first crew will be 20. The weight of the people, consumables and kit alone would be more than 50 tons assuming a 900 day mission.
Hence 2 ships pre-positioned, and two coming with.  And IMO they might even up that
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/15/2019 11:52 pm
Just to be clear, we're talking about 900 mT of landed mass for the first crew, which we're speculating at 20 people.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/16/2019 03:50 pm
Just to be clear, we're talking about 900 mT of landed mass for the first crew, which we're speculating at 20 people.
How do they get 900mT to Mars for the first crew?
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/16/2019 04:00 pm
Just to be clear, we're talking about 900 mT of landed mass for the first crew, which we're speculating at 20 people.
How do they get 900mT to Mars for the first crew?
300 tons (2x 150 ton starships) in 2022, plus 600 tons (2x 150 ton cargo and 2x 150 ton crew) in 2024

Presumably if the lift is only 100 tons, he'll just send 50% more starships.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/17/2019 07:18 am
300 tons (2x 150 ton starships) in 2022, plus 600 tons (2x 150 ton cargo and 2x 150 ton crew) in 2024
Exactly.  I think the value of refilling is just starting to sink in.

1 Starship launch + 5 tanker launches (6 total) gets you 150 mT of payload all the way to the surface of Mars.

The first crew will have 6 Starships on Mars. So for 36 total BFR launches, you get 900 mT of payload on Mars.

Quote from: Elon Musk IAC 2017
Now I want to talk about the value of orbital refilling. This is also extremely important. If you just fly BFR to orbit and don't do any refilling, it's pretty good — you'll get 150 tons to low earth orbit, and have no fuel to go anywhere else.

However, if you send up tankers and refill in orbit, you could refill the tanks up all the way to the top, and get 150 tons all the way to Mars.

And if the tanker has high reuse capability, then you're just paying for the cost of propellant. The cost of oxygen is extremely low, and the cost of methane is extremely low. So if that's all you're dealing with, the cost of refilling your spaceship on orbit is tiny, and you can get 150 tons all the way to Mars. So automated rendezvous, and docking, and refilling, absolutely fundamental.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/17/2019 12:14 pm
My understanding is that Starship can carry "100+" tons to LEO. The previous version was 150tons not the current one (unless I have missed something). So if it is only 100tons and you want 900tons on Mars that would require 9 Starships and 99 Superheavy launches. Which IMHO would be a tall order at the moment.

Hopefully the 100+ figure will morph closer to your 150 figure when we get the next announcement.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/17/2019 12:21 pm
My understanding is that Starship can carry "100+" tons to LEO. The previous version was 150tons not the current one (unless I have missed something). So if it is only 100tons and you want 900tons on Mars that would require 9 Starships and 99 Superheavy launches. Which IMHO would be a tall order at the moment.

Hopefully the 100+ figure will morph closer to your 150 figure when we get the next announcement.
Sure, but that just means sending 50% more rockets, 50% more tankers for the initial rockets, and another 75% of the initial tanker count (additional 50% tankers times 150% of initial planned fuel load is 75%) to top off the extra ships.

That's still less than double the number of launches.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/17/2019 12:28 pm
My understanding is that Starship can carry "100+" tons to LEO. The previous version was 150tons not the current one (unless I have missed something). So if it is only 100tons and you want 900tons on Mars that would require 9 Starships and 99 Superheavy launches. Which IMHO would be a tall order at the moment.

Hopefully the 100+ figure will morph closer to your 150 figure when we get the next announcement.

100+t is the temporary limit. It came when they decided to start flying without Raptor vac. With Raptor vac they will be back at 150t, that's my understanding. Maybe a little more more if stainless steel is indeed more mass efficient.

Edit: I expect that Raptor vac will be available by 2024, maybe not 2022.

Title: Re: Power options for a Mars settlement
Post by: envy887 on 04/17/2019 01:12 pm
My understanding is that Starship can carry "100+" tons to LEO. The previous version was 150tons not the current one (unless I have missed something). So if it is only 100tons and you want 900tons on Mars that would require 9 Starships and 99 Superheavy launches. Which IMHO would be a tall order at the moment.

Hopefully the 100+ figure will morph closer to your 150 figure when we get the next announcement.

Delta-v wise it an still land 225+ tonnes on Mars, assuming the entry aerodynamics work out with that loaded mass and you're willing to transfer payload in LEO.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/17/2019 01:18 pm
I doubt the first few Starships will carry anywhere near their max payloads. BUT that's fine when you're literally 100x the max payload we've ever landed on Mars.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/17/2019 03:14 pm
Good times when people think 9x100 ton starships are crazy, but 6 are reasonable.  Musk is getting to people...

The value of in-orbit fueling is that you bypass the rocket equation.  Your dry second stage becomes a fully-fueled one.  It's the only way to fly.

This is why chemical orbit-to-orbit ships don't make sense...  Even after you've supposedly captured into Earth orbit, you still need to bring up all the fuel, cargo, and people.  The fuel itself requires 5-6x the number of launches, plus at least one more for the payload, which then has to be transferred...  So basically, why bother.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/17/2019 04:51 pm
Good times when people think 9x100 ton starships are crazy, but 6 are reasonable.  Musk is getting to people...

The value of in-orbit fueling is that you bypass the rocket equation.  Your dry second stage becomes a fully-fueled one.  It's the only way to fly.

This is why chemical orbit-to-orbit ships don't make sense...  Even after you've supposedly captured into Earth orbit, you still need to bring up all the fuel, cargo, and people.  The fuel itself requires 5-6x the number of launches, plus at least one more for the payload, which then has to be transferred...  So basically, why bother.
Specialization makes sence when there's enough traffic to amortize the spacecraft just off the specialized traffic. That's one reason the SSTO crowd is so happy about SABER- Earth to Orbit is a trip that can easily pay for development of a specialized earth to orbit vehical. (see: every earth to orbit vehical so far)

A highly efficient earth to orbit vehical, transshipping and refueling a dedicated orbit to orbit vehical, transshipping to a dedicated  mars to orbit vehical or moon to orbit vehical, is basically the hub and spoke model we are all familiar with.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/17/2019 10:50 pm
Good times when people think 9x100 ton starships are crazy, but 6 are reasonable.  Musk is getting to people...

The value of in-orbit fueling is that you bypass the rocket equation.  Your dry second stage becomes a fully-fueled one.  It's the only way to fly.

This is why chemical orbit-to-orbit ships don't make sense...  Even after you've supposedly captured into Earth orbit, you still need to bring up all the fuel, cargo, and people.  The fuel itself requires 5-6x the number of launches, plus at least one more for the payload, which then has to be transferred...  So basically, why bother.
You do not bypass the rocket equation. But reusability is key as it makes the logistics easier to manage. Conceptually from a rocket equation perspective (ignoring practicalities) multiple launches are no different to building a wider rocket by joining individual rockets side to side. It still takes just as much propellant to launch the same amount of payload. The mass ratio is the same for one as for many.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/18/2019 02:21 am
Good times when people think 9x100 ton starships are crazy, but 6 are reasonable.  Musk is getting to people...

The value of in-orbit fueling is that you bypass the rocket equation.  Your dry second stage becomes a fully-fueled one.  It's the only way to fly.

This is why chemical orbit-to-orbit ships don't make sense...  Even after you've supposedly captured into Earth orbit, you still need to bring up all the fuel, cargo, and people.  The fuel itself requires 5-6x the number of launches, plus at least one more for the payload, which then has to be transferred...  So basically, why bother.
You do not bypass the rocket equation. But reusability is key as it makes the logistics easier to manage. Conceptually from a rocket equation perspective (ignoring practicalities) multiple launches are no different to building a wider rocket by joining individual rockets side to side. It still takes just as much propellant to launch the same amount of payload. The mass ratio is the same for one as for many.
Not bypass, but I think "Reset" is a good word. "Reset the rocket equation" for your spacecraft when your refuel.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/18/2019 03:04 am
Good times when people think 9x100 ton starships are crazy, but 6 are reasonable.  Musk is getting to people...

The value of in-orbit fueling is that you bypass the rocket equation.  Your dry second stage becomes a fully-fueled one.  It's the only way to fly.

This is why chemical orbit-to-orbit ships don't make sense...  Even after you've supposedly captured into Earth orbit, you still need to bring up all the fuel, cargo, and people.  The fuel itself requires 5-6x the number of launches, plus at least one more for the payload, which then has to be transferred...  So basically, why bother.
You do not bypass the rocket equation. But reusability is key as it makes the logistics easier to manage. Conceptually from a rocket equation perspective (ignoring practicalities) multiple launches are no different to building a wider rocket by joining individual rockets side to side. It still takes just as much propellant to launch the same amount of payload. The mass ratio is the same for one as for many.
Not bypass, but I think "Reset" is a good word. "Reset the rocket equation" for your spacecraft when your refuel.
Yup, better.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/18/2019 09:40 am
In any case, with several hundred mT of payload on Mars for the first crew, that opens up some possibilities for power options.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/18/2019 06:58 pm
In any case, with several hundred mT of payload on Mars for the first crew, that opens up some possibilities for power options.
Yes the possibilities are intriguing. The real tricky thing for the first missions will be getting the right balance between different types of payload because the trade-offs are many and complex.

For example propellant: do you take a little less to make cadence of the refuelling missions easier in the early days? Do you take extra propellant (and less cargo) to reduce the flight time to Mars? Or extra cargo and less propellant and risk a longer transfer? Or even extra propellant to land on the surface to reduce the burden on ISRU.

The same question can be asked of many other things. How much power generating capacity to take? The more you take the easier it will be to cope with dust storms and the faster the ISRU can be processed, but at the cost of taking less of everything else.

One thing IMO that there won’t be is the luxury of having so much cargo that these things will not be an issue, they will be an issue. And there will be plenty more difficult decisions to make. Everything from how many crew to take to how many chairs.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 04/18/2019 07:29 pm
For planning purposes it safer to plan on the reduced payload to the 2022 cargo flights and the higher payloads for the 2024 flights.
Also the cargo (slower) flights verses crewed (faster) flights will have different payloads.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/18/2019 08:34 pm
For planning purposes it safer to plan on the reduced payload to the 2022 cargo flights and the higher payloads for the 2024 flights.
Also the cargo (slower) flights verses crewed (faster) flights will have different payloads.

Yes I think the will want to make the first manned landing as similar as possible to the cargo landing a synod earlier. They may have more payload in the cargo ships.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/18/2019 10:02 pm
Do Mars dust storms last much more than a month?  Although they can cover the planet, they seem to be relatively brief, at least from what I was able to find in various papers.  For a solar powered colony, If the energy loss during a dust storm is 60% of it's normal gain, but these only happen 1 month out of 36, it means that for any given synod the fuel production drop will never be more than 1/24, or about 4%.
Doesn't seem all that significant.
Unless there are times when there are 2 storms per synod?  I guess we need to plan for the extreme and not the average.  In such a case the power for fuel production should be such that 8% extra fuel can be produced per synod, if required.  That's a fairly large amount.  Or the colony should be able to survive with 9/10th of the planed supplies.  Whatever is easier to do.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 04/19/2019 03:43 am
Do Mars dust storms last much more than a month?

The Oppy-killer storm started in late May and hit the rover in early June, it didn't peak until end of July, with another two full months to clear back down to pre-storm opacity levels. (Well, there was still higher dust levels in mid-September (Tau-1.5) than May, but by then that could have been seasonal, there were small regional storms in the southern hemisphere in mid-September. I don't have (Mars) year-on-year for comparison.)

Opportunity was particularly unlucky with that storm, it had started close by, so Oppy got shadowed early and heavily even before the storm went global. MSL was covered a week or so later, I think. The southern hemisphere was hit later still. The 2007 global storm, OTOH, started in the southern hemisphere, and I think both MER rovers got off lightly. (The one before that (2001) was a southern starter as well. Specifically a Helles storm, IIRC.)

In a normal year, it's not unusual for the opacity to average Tau >2 for more than a third of a Mars-year, along with regional storms creating localised opacities >3, but OTOH it'll be <1 for another third to half a Mars-year. Might as well say that you get one good Earth-year, followed by one bad one, even without storms. Of course, another year it might never go above 2. But IMO that's what you'd be planning around. So you would plan something to be "bursty". Given agriculture can't be (season, yes, but not one year on, one year off), is the fuel production year-on/year-off? Or is fuel production constant, but mining water is seasonal, since you can more easily stockpile water than LOx. Especially with the synod dates moving around the Mars-year. So... {Shrug}

(https://planetary.s3.amazonaws.com/assets/images/mer_updates/2018-07/20180802_5-Under-the-blanket-20180614-003530bSA.jpg) (https://planetary.s3.amazonaws.com/assets/images/mer_updates/2018-07/20180802_5-Under-the-blanket-20180614-003530bSA.jpg)
Title: Re: Power options for a Mars settlement
Post by: geza on 04/19/2019 07:30 am
Can anybody explain, how PV output is related to opacity/Tau?
Title: Re: Power options for a Mars settlement
Post by: hopalong on 04/19/2019 08:27 am
Higher the TAU, lower the amount of sunlight (energy) reaches the ground as it is scattered by the dust.

Less energy reaching the ground, and the PV panels, less power is produced, that what did it in for oppy, his PV panels could not produce enough power to keep his batteries charged.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/19/2019 02:37 pm
Do Mars dust storms last much more than a month?

The Oppy-killer storm started in late May and hit the rover in early June, it didn't peak until end of July, with another two full months to clear back down to pre-storm opacity levels. (Well, there was still higher dust levels in mid-September (Tau-1.5) than May, but by then that could have been seasonal, there were small regional storms in the southern hemisphere in mid-September. I don't have (Mars) year-on-year for comparison.)

Opportunity was particularly unlucky with that storm, it had started close by, so Oppy got shadowed early and heavily even before the storm went global. MSL was covered a week or so later, I think. The southern hemisphere was hit later still. The 2007 global storm, OTOH, started in the southern hemisphere, and I think both MER rovers got off lightly. (The one before that (2001) was a southern starter as well. Specifically a Helles storm, IIRC.)

In a normal year, it's not unusual for the opacity to average Tau >2 for more than a third of a Mars-year, along with regional storms creating localised opacities >3, but OTOH it'll be <1 for another third to half a Mars-year. Might as well say that you get one good Earth-year, followed by one bad one, even without storms. Of course, another year it might never go above 2. But IMO that's what you'd be planning around. So you would plan something to be "bursty". Given agriculture can't be (season, yes, but not one year on, one year off), is the fuel production year-on/year-off? Or is fuel production constant, but mining water is seasonal, since you can more easily stockpile water than LOx. Especially with the synod dates moving around the Mars-year. So... {Shrug}

(https://planetary.s3.amazonaws.com/assets/images/mer_updates/2018-07/20180802_5-Under-the-blanket-20180614-003530bSA.jpg) (https://planetary.s3.amazonaws.com/assets/images/mer_updates/2018-07/20180802_5-Under-the-blanket-20180614-003530bSA.jpg)
So they probably want to max out on the soalr panels and batteries for a few synods. That way they will have a lot more options in this tricky area. They could run in fast mode when there's no dust storm, they could run ISRU overnight from battery and hunker down when a storm arrives as they would still get some power (or just run ISRU slowly depending on the power available).
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/19/2019 02:39 pm
I think if you don't size your system for half of the time being really bad tau, and that it might last the better part of 12 months, you are asking for trouble. You can do load shedding but some power always has to be available for keepalive tasks (food production, heating/lighting, comms, etc). 

So that means maybe you need to size ISRU to produce twice as fast as you need if you assume perfect power steady state. 

IMHO.

(Long term, transmission lines tying different colonies together might be a solution. Another longer term solution is solar power sats.)
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/19/2019 02:48 pm
I think if you don't size your system for half of the time being really bad tau, and that it might last the better part of 12 months, you are asking for trouble. You can do load shedding but some power always has to be available for keepalive tasks (food production, heating/lighting, comms, etc). 

So that means maybe you need to size ISRU to produce twice as fast as you need if you assume perfect power steady state. 

IMHO.

(Long term, transmission lines tying different colonies together might be a solution. Another longer term solution is solar power sats.)
I woner if long term putting a solar farm on top of one of the volcanos would be benificial?
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/19/2019 03:03 pm
Since fuel production is going to be taking up the vast majority of their power budget, it seems likely that the settlement will be able to survive during severe dust storms simply by turning off the fuel production, with only minimal methane fuel cell usage.  With this in mind, maybe it would be simplest just to accept the possibility of loosing the better part of an (earth) year's production and plan for the astronauts possibly staying on Mars for an extra two years until the second return launch window opens.
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/19/2019 03:25 pm
Since fuel production is going to be taking up the vast majority of their power budget, it seems likely that the settlement will be able to survive during severe dust storms simply by turning off the fuel production, with only minimal methane fuel cell usage.  With this in mind, maybe it would be simplest just to accept the possibility of loosing the better part of an (earth) year's production and plan for the astronauts possibly staying on Mars for an extra two years until the second return launch window opens.
Or size the plant to produce 120% of the fuel needed in one year, but keep running and storing if the power's available. (or run the smelter and silicon foundry flat out maybe?... that's probably not first synod's cargo tho)

(as to what to do with the propellant if you have a lot of excess? Store it in orbit. When you have more than one ship, launch one, leave it in orbit, launch the other, tank up the first, return, repeat... Since you have to use fuel to loft it, you will reduce the amount you need to store groundside by more than the amount stored in orbit... that propellant in orbit is going to come in handy eventually even if not used for the first return)
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/19/2019 04:24 pm
Since fuel production is going to be taking up the vast majority of their power budget, it seems likely that the settlement will be able to survive during severe dust storms simply by turning off the fuel production, with only minimal methane fuel cell usage.  With this in mind, maybe it would be simplest just to accept the possibility of loosing the better part of an (earth) year's production and plan for the astronauts possibly staying on Mars for an extra two years until the second return launch window opens.
Or size the plant to produce 120% of the fuel needed in one year, but keep running and storing if the power's available. (or run the smelter and silicon foundry flat out maybe?... that's probably not first synod's cargo tho)

(as to what to do with the propellant if you have a lot of excess? Store it in orbit. When you have more than one ship, launch one, leave it in orbit, launch the other, tank up the first, return, repeat... Since you have to use fuel to loft it, you will reduce the amount you need to store groundside by more than the amount stored in orbit... that propellant in orbit is going to come in handy eventually even if not used for the first return)
Now I'm having Game Boy Brick flashbacks, imagining the "Pipe Dream" if the oversized methane plant had a good 2 years with clear skys and the crew has to scramble to plumb additional cargoships as storage tanks. (given a probably minimum of 1 km separation between the early landers for landing debris mitigation)
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/19/2019 05:22 pm
Since fuel production is going to be taking up the vast majority of their power budget, it seems likely that the settlement will be able to survive during severe dust storms simply by turning off the fuel production, with only minimal methane fuel cell usage.  With this in mind, maybe it would be simplest just to accept the possibility of loosing the better part of an (earth) year's production and plan for the astronauts possibly staying on Mars for an extra two years until the second return launch window opens.
Or size the plant to produce 120% of the fuel needed in one year, but keep running and storing if the power's available. (or run the smelter and silicon foundry flat out maybe?... that's probably not first synod's cargo tho)

(as to what to do with the propellant if you have a lot of excess? Store it in orbit. When you have more than one ship, launch one, leave it in orbit, launch the other, tank up the first, return, repeat... Since you have to use fuel to loft it, you will reduce the amount you need to store groundside by more than the amount stored in orbit... that propellant in orbit is going to come in handy eventually even if not used for the first return)

More like 150%.  From what people are saying, these dust storms are associated with some fairly long term atmospheric dust that reduces the amount of sun reaching the ground by a significant, if not crippling, amount.  Since the amount of solar panels you're going to need even under normal circumstances is pretty huge, it might be easiest to just send extra consumables than to greatly increase the solar panel area chasing down a guarenteed return date.  There's nothing wrong with a 10-20% chance of missing the earliest return window if they have supplies to wait it out comfortably.

Part of the problem is that we don't really have a good idea how bad these planet wide storms can get.  We only have three solid data points.  Were these three big storms on the mild side?  Fairly average?  Worse than normal?  Don't want to bet the survival of the colonists on such limited data.

Another problem is that the effeciency of the ISRU will be influenced by a lot of factors, some of which are pretty much unknown until we actually have people on the ground running the equipment.  What happens if the production is much lower than expected?  Worse, what if there turn out to be some design flaws that only show their heads under actual Martian conditions that result in early equipment failure?  We can't really test these things on Mars without human operators.  However, having the settlement able to survive through through two Earth-Mars launch windows takes a lot of pressure off of any sort of emergency supply missions that might come up.

Sending up some Starships to serve as insulated tanks also sounds like a good idea in general.  This lets them bring in a reserve in case of ISRU failure, and they're going to need insulated tanks anyway.  Until they have fully functional mining and foundary and machining capability, ALL equipment will have to be shipped from Earth.

Expect some Starships to be "expended" for use as makeshift buildings and tanks during the early colonization phases.  Even something as simple as having a cargo Starship there to use as a place to deploy some of their ISRU machinery to keep the dust away.  Hoisting things up and down will get old fast, though.  I wonder what it would take to either put the rocket on its side or else cut the cargo section off and lower it to the ground?  Definitely a fairly big crane.  Probably shouldn't count on any sort of heavy equipment for quite a while since it will be REALLY hard to get down out of the cargo hold and deploy.

I can't think of any reason it would be better to put a tanker in orbit than to just leave it on the ground.  They won't need orbital refueling to return since Mars' low gravity makes a single stage return completely doable.  But putting them in orbit makes them completely inaccessible.  Maybe they're be useful there as reserves sent from Earth, which could be on standby and just fly back to Earth if they're never needed?  This is assuming they have the delta-V to actually do so.
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/19/2019 05:41 pm
120% of the proellant needed in ONE year... that would be 240% with perfect skies, in two years. Hence my suggestion to store propellant in orbit. You use up a goodly fraction of it getting it there, reducing storage requirements.  This assumes ZBO
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 04/19/2019 06:47 pm
120% of the proellant needed in ONE year... that would be 240% with perfect skies, in two years. Hence my suggestion to store propellant in orbit. You use up a goodly fraction of it getting it there, reducing storage requirements.  This assumes ZBO

Part of the trade off is storing it on the ground verses storing it on orbit.  Which is more efficient?   
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/19/2019 06:52 pm
Since fuel production is going to be taking up the vast majority of their power budget, it seems likely that the settlement will be able to survive during severe dust storms simply by turning off the fuel production, with only minimal methane fuel cell usage.  With this in mind, maybe it would be simplest just to accept the possibility of loosing the better part of an (earth) year's production and plan for the astronauts possibly staying on Mars for an extra two years until the second return launch window opens.
Or size the plant to produce 120% of the fuel needed in one year, but keep running and storing if the power's available. (or run the smelter and silicon foundry flat out maybe?... that's probably not first synod's cargo tho)

(as to what to do with the propellant if you have a lot of excess? Store it in orbit. When you have more than one ship, launch one, leave it in orbit, launch the other, tank up the first, return, repeat... Since you have to use fuel to loft it, you will reduce the amount you need to store groundside by more than the amount stored in orbit... that propellant in orbit is going to come in handy eventually even if not used for the first return)

More like 150%.  From what people are saying, these dust storms are associated with some fairly long term atmospheric dust that reduces the amount of sun reaching the ground by a significant, if not crippling, amount.  Since the amount of solar panels you're going to need even under normal circumstances is pretty huge, it might be easiest to just send extra consumables than to greatly increase the solar panel area chasing down a guarenteed return date.  There's nothing wrong with a 10-20% chance of missing the earliest return window if they have supplies to wait it out comfortably.

How did you arrive at a 50% margin for dust storm risk mitigation, unless you're expecting dust storms for 1/3rd of the 780 day synodic cycle?

Obviously there will be other margins too (for initial ramp, underproduction, breakdowns, regular maintenance, etc). But 50% just for dust storms seems high.


Part of the problem is that we don't really have a good idea how bad these planet wide storms can get.  We only have three solid data points.  Were these three big storms on the mild side?  Fairly average?  Worse than normal?  Don't want to bet the survival of the colonists on such limited data.

What's the alternative? Wait decades for more data?

We have N=3, so set the bell curve standard deviation accordingly, set your requirement at the 99th percentile storm (or whatever number), and move on. But carrying extra solar panels isn't free either, since it comes with the opportunity cost of leaving behind other potentially life-saving supplies. So it's an optimization problem: what combination of supplies gives the most total risk mitigation for a given payload mass? And how does that balance against other goals, like quickly setting up colonization infrastructure?


Expect some Starships to be "expended" for... even something as simple as having a cargo Starship there to use as a place to deploy some of their ISRU machinery to keep the dust away.

Tents are far cheaper and easier.


Hoisting things up and down will get old fast, though.  I wonder what it would take to either put the rocket on its side or else cut the cargo section off and lower it to the ground?

"I do like the new apartment building, but hoisting things up and down in the elevator will get old fast. I wonder what it would take to either put the building on its side or else cut off the upper floors and lower them to the ground?"


I can't think of any reason it would be better to put a tanker in orbit than to just leave it on the ground.

I can think of several:

• Easier to insulate with no Martian atmosphere
• Stores 3x as much fuel per landed Starship (for the reasons Lar mentioned)
• No need to prepare another tank site on the tank farm
• Smaller tank farm needs smaller berm/hill for shielding
• Smaller tank farm has less setback, so shorter pipe runs to the colony and launch pad
• No connecting pipes at the tank farm, just reuse on-orbit refueling pipes
• Solar panels for ZBO refrigeration can be in near-constant sunlight (for high inclination/beta angle orbits, or other suitable orbits)

Your ZBO system needs large radiators even on the Martian surface, but on-orbit they can deploy only in microgravity (reusing Starship's radiator). And the radiated heat load should be far less than on the surface, because in a vacuum MLI can drive solar heating to very small values.

Does anyone know what max-Q is for ascent to LMO (assuming sensible throttle-down)? Could a Nomex-protected MLI blanket survive if suitably attached? Or is it a better plan overall to deploy in orbit?


They won't need orbital refueling to return since Mars' low gravity makes a single stage return completely doable.

True, but with reliable automated docking and refueling there's little penalty for doing so, and big potential savings (for the reasons outlined above).

But putting them in orbit makes them completely inaccessible.

Since the proposal is for Earth return fuel storage, that's not a problem. Obviously you don't launch fuel uphill if it might be needed later on the ground.

Maybe they're be useful there as reserves sent from Earth, which could be on standby and just fly back to Earth if they're never needed?  This is assuming they have the delta-V to actually do so.

No, sending the fuel from Earth would be worse. You can't send a fully-loaded Starship from Earth to Mars (it must burn that fuel to reach Mars), but you can fill it from the Martian surface using multiple tanker flights. And it's obviously impractical to send multiple tankers from Earth to refill a depot in LMO.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/19/2019 07:04 pm
"I do like the new apartment building, but hoisting things up and down in the elevator will get old fast. I wonder what it would take to either put the building on its side or else cut off the upper floors and lower them to the ground?"
We call it Urbal Sprawl.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 04/19/2019 07:36 pm
Higher the TAU, lower the amount of sunlight (energy) reaches the ground as it is scattered by the dust.

Less energy reaching the ground, and the PV panels, less power is produced, that what did it in for oppy, his PV panels could not produce enough power to keep his batteries charged.

Not the whole story. What killed Opportunity was that the ambient light level dropped due to dust in the atmosphere and that the dust settled on the rover's solar panels blocking whatever ambient light there was. Dust on the panels was a problem for both rovers even on the clearest and brightest days. The rovers had no means of removing the settled dust - which will not be true for a manned colony (I should hope!).

One possibility to consider are infra-red solar cells. IR is not scattered by dust (hence its popularity with astronomers).
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/19/2019 08:15 pm
I seem to remember hearing that the power output of solar panels doesn't scale linearly with the amount of light.

In other words, on a normal sunny day at noon you may have X amount of light, which produces Y amount of power.
But if the light on the solar panel is 1/2 X, then the power output may be significantly less than 1/2 Y.

Does anyone know more about this? Could it be a major factor in dust storms?
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 04/19/2019 08:17 pm
I know my solar panels produce about 6kW in sun and 2kW on a not too dark cloudy day.

Anybody know what percent for the rovers was reduced sun versus dust?
If it was 50% them cleaning panels sounds like it could be great during a storm.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/20/2019 10:31 am
I know my solar panels produce about 6kW in sun and 2kW on a not too dark cloudy day.

Anybody know what percent for the rovers was reduced sun versus dust?
If it was 50% them cleaning panels sounds like it could be great during a storm.

Did you use a light meter on both days? Human eyes are notoriously inaccurate at measuring light levels.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/20/2019 02:39 pm
The large storage tanks we used on the ground (when I was working with a gas company) were nothing but a giant thermos bottle.  Tank within a tank with about 3' of space between.  We pulled a vacuum on the space and put the liquid natural gas inside the inner tank.  Very little boil off.  We had refrigeration equipment to recycle the boiloff.  Temps ranged from 100 degrees F in summer to say around 10 degrees F in winter.  We had I 6 tanks that could supply my whole state with natural gas for 30 days in case of major power outage.  Longer with cutting off large industries that  had alternative fuel like propane, coal, or fuel oil.  Stretching out the gas with large industry using alternative fuels would last all the residential and small commercial about 3 months.  This is with over 500,000 customers.  So, storage on the ground is quite possible with very little energy needed for recooling.  On Mars it would require welding of large tanks, then pulling the vacuum on them.  Or smaller tanks that could fit inside the cargo bay of Starships that could be removed and clustered somewhere, and maybe bury in Martian soil for more daytime insulation.  Most ground storage would be used for Mars emergency power generation.

I do like the idea of having tanker Starships left in Mars orbit to take on excess metholox production.  Say a fully loaded return ship may need to top off before returning to earth to be able to land with a full 100-150 ton load of Martian products, samples or something.  Or an overloaded Mars bound ship needs to top off fuel to be able to land on Mars.  On orbit refueling will make for more tonnage of supplies delivered to Mars. 
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/20/2019 02:44 pm
As the Martian colony grows, there is no question that solar will not be enough power.  Small nuclear power plants will have to be brought in for large scale power production, especially for Martian industrial needs.  Mining, smelting, making of metals will all require huge amounts of power.  There is probably no coal on Mars for melting metals, so a lot of electrical power will be needed to power lasers or other equipment to melt the metals. 
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/20/2019 04:14 pm
As the Martian colony grows, there is no question that solar will not be enough power.  Small nuclear power plants will have to be brought in for large scale power production, especially for Martian industrial needs.  Mining, smelting, making of metals will all require huge amounts of power. There is probably no coal on Mars for melting metals, so a lot of electrical power will be needed

So build large solar fields. What's the problem?

These fields can even be located on top of your regolith-shielded buildings (which are preferably wide "warehouse" shapes to minimize radiation shielding cost; see the Envisioning Amazing Habs thread).

to power lasers or other equipment to melt the metals.

Lasers are only ~10% efficient. Better to use insulated induction-heating crucibles.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/20/2019 09:02 pm
The large storage tanks we used on the ground (when I was working with a gas company) were nothing but a giant thermos bottle.  Tank within a tank with about 3' of space between.  We pulled a vacuum on the space and put the liquid natural gas inside the inner tank.  Very little boil off.  We had refrigeration equipment to recycle the boiloff.  Temps ranged from 100 degrees F in summer to say around 10 degrees F in winter.  We had I 6 tanks that could supply my whole state with natural gas for 30 days in case of major power outage.  Longer with cutting off large industries that  had alternative fuel like propane, coal, or fuel oil.  Stretching out the gas with large industry using alternative fuels would last all the residential and small commercial about 3 months.  This is with over 500,000 customers.  So, storage on the ground is quite possible with very little energy needed for recooling.  On Mars it would require welding of large tanks, then pulling the vacuum on them.  Or smaller tanks that could fit inside the cargo bay of Starships that could be removed and clustered somewhere, and maybe bury in Martian soil for more daytime insulation.  Most ground storage would be used for Mars emergency power generation.

I do like the idea of having tanker Starships left in Mars orbit to take on excess metholox production.  Say a fully loaded return ship may need to top off before returning to earth to be able to land with a full 100-150 ton load of Martian products, samples or something.  Or an overloaded Mars bound ship needs to top off fuel to be able to land on Mars.  On orbit refueling will make for more tonnage of supplies delivered to Mars.

Do you know how hard the vacuum was in the gas storage tank you mentioned?
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/21/2019 01:24 am

Do you know how hard the vacuum was in the gas storage tank you mentioned?

I do not know how hard the vacuum was.  I do know the outside tanks were painted silver to reflect sunlight.  I worked in another area, mostly pipeline and regulation construction. 
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/21/2019 01:37 am
The large storage tanks we used on the ground (when I was working with a gas company) were nothing but a giant thermos bottle.  Tank within a tank with about 3' of space between.  We pulled a vacuum on the space and put the liquid natural gas inside the inner tank.  Very little boil off.  We had refrigeration equipment to recycle the boiloff.  Temps ranged from 100 degrees F in summer to say around 10 degrees F in winter.  We had I 6 tanks that could supply my whole state with natural gas for 30 days in case of major power outage.  Longer with cutting off large industries that  had alternative fuel like propane, coal, or fuel oil.  Stretching out the gas with large industry using alternative fuels would last all the residential and small commercial about 3 months.  This is with over 500,000 customers.  So, storage on the ground is quite possible with very little energy needed for recooling.  On Mars it would require welding of large tanks, then pulling the vacuum on them.  Or smaller tanks that could fit inside the cargo bay of Starships that could be removed and clustered somewhere, and maybe bury in Martian soil for more daytime insulation.  Most ground storage would be used for Mars emergency power generation.

I do like the idea of having tanker Starships left in Mars orbit to take on excess metholox production.  Say a fully loaded return ship may need to top off before returning to earth to be able to land with a full 100-150 ton load of Martian products, samples or something.  Or an overloaded Mars bound ship needs to top off fuel to be able to land on Mars.  On orbit refueling will make for more tonnage of supplies delivered to Mars.

Do you know how hard the vacuum was in the gas storage tank you mentioned?

Keep in mind that the Martian atmosphere itself is basically a vacuum.  0.6% of Earth's atmospheric pressure.  You probably wouldn't have to bother pulling a vacuum on your tanks beyond just opening them up.

As for welding tanks, you don't have to do this if there's a convenient tanker starship or two landed nearby, as you would do if you wanted to make sure you could return even if the ISRU fails.

Putting something in low orbit of Mars takes something along the lines of 4000 m/s of delta-V.  If a tanker has a 85 ton dry mass (pulling this from Wikipedia), and Raptor has an ISP of about 350, we find that to loft the tanker itself (which we don't otherwise have to do), empty, will take at LEAST 100 tons of fuel and oxidizer.  This is ignoring the rocket equation.  The real cost will be more like 150 tons.

For emphasis, 150 or so tons of fuel just to carry up the mass of the *empty* tanker!  This is entirely extra mass that you would not be returning if you left the tanker on the ground as infrastructure.

So, unless you expect 150 tons worth of boiloff on the surface that you won't have in orbit, putting a tanker up is a loss.

As far as carrying extra mass home from Mars, having a tanker in orbit will allow you to do that.  It will not allow you to bring an appreciable amount of extra mass from Earth, though, since by the time you're in Martian orbit, you've already done the vast majority of the work.  Reentry and landing doesn't take very much delta-V.
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/21/2019 02:32 am

So, unless you expect 150 tons worth of boiloff on the surface that you won't have in orbit,
Or if your plant produces 10 starships worth of propellant a synod but you only have 4 on the ground...
Quote
putting a tanker up is a loss.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/21/2019 02:40 am
I predict many Starships may be left on the ground.  They may have engines removed for spares, cargo areas for water storage for gravity fed water system for colony nearby, or even habitats.  I do think for continuous power 24-7 nuclear plants will be needed, especially if 24 hour manufacturing operations begin.  I think it would be cheaper than the cost of huge battery banks, especially weight wise transporting from earth.  Small 20 ton reactors have been designed.  They could be placed in craters or underground for long term safety.  They can be safely designed. 
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/21/2019 02:51 am

So, unless you expect 150 tons worth of boiloff on the surface that you won't have in orbit,
Or if your plant produces 10 starships worth of propellant a synod but you only have 4 on the ground...
Quote
putting a tanker up is a loss.

Putting them in orbit won't get you any more tankers to put fuel excess fuel in. ;)

Anyway, producing enough fuel to fill all their tanks like this is probably beyond their wildest dreams.  Eventually, getting big payloads back and storing large quantities of fuel might matter, but for the immediate future we care about making sure there's enough fuel to return 1 Starship with crew.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/21/2019 03:00 am

So, unless you expect 150 tons worth of boiloff on the surface that you won't have in orbit,
Or if your plant produces 10 starships worth of propellant a synod but you only have 4 on the ground...
Quote
putting a tanker up is a loss.

Putting them in orbit won't get you any more tankers to put fuel excess fuel in. ;)

Sure, but it means each tanker can hold ~3x as much fuel.
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/21/2019 03:05 am
Putting them in orbit won't get you any more tankers to put fuel excess fuel in. ;)
You're demonstrating that you haven't yet internalised the suggestion here. Fuel in orbit takes fuel to put there,  (and thus doesn't need to be kept in a tanker, since it got expended, reducing the number of tankers you need) but has value beyond fuel on the ground.  Everyone else in the thread gets that.

Let's move on. We all get it.
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/21/2019 03:28 am
I predict many Starships may be left on the ground.  They may have engines removed for spares, cargo areas for water storage for gravity fed water system for colony nearby, or even habitats.  I do think for continuous power 24-7 nuclear plants will be needed, especially if 24 hour manufacturing operations begin.  I think it would be cheaper than the cost of huge battery banks, especially weight wise transporting from earth.  Small 20 ton reactors have been designed.  They could be placed in craters or underground for long term safety.  They can be safely designed.

Long term, I agree that nuclear power is a very good option.  The Russians have actually launched several nuclear reactors on satellites, but these have all been in the low kilowattt range.  They will need around 1 megawatt for their fuel production according to SpaceX.  There has been research and even some level of testing for higher power systems, but to my knowledge none of these have ever flown, and most of this was done 20 years ago or more.

The biggest problem, though, is getting all this past regulators.  They tend to hate change and dealing with new ideas, and nuclear is a scary word.

All of this means that depending on nuclear power as a mission critical component is very risky.  The nice thing about solar power is that the technology exists right now and is readily available.
Title: Re: Power options for a Mars settlement
Post by: Keldor on 04/21/2019 03:57 am
Putting them in orbit won't get you any more tankers to put fuel excess fuel in. ;)
You're demonstrating that you haven't yet internalised the suggestion here. Fuel in orbit takes fuel to put there,  (and thus doesn't need to be kept in a tanker, since it got expended, reducing the number of tankers you need) but has value beyond fuel on the ground.  Everyone else in the thread gets that.

Let's move on. We all get it.

Sorry for being snarky - I did miss the point.

However, I do disagree with the premise that fuel in orbit has any extra value in a practical sense during the early years of the colony.

Eventually, maybe 20-30 years after the colony is first started, having orbital fuel supplies might make sense.  This is assuming that the colony has anything worth exporting to use that extra payload capacity, which is a big if.  Goods produced on Mars will be done at great difficulty and at great expense, and scientists might well be a lot better off actually visiting the colony than importing thousands of tons of rocks.

My perspective is more immediate than that, though.  I'm concerned about what the colony will need during the first few flights.  Fuel is going to be a very precious commodity for a while, and putting your reserves somewhere inaccessible to the ground, which orbit effectively is since the penalty for putting the tanker up and landing it again later is somewhere around half of the entire tanker's worth of fuel, seems like a really bad idea when you're worried about returning at all.

Note that if you're only interested in returning Starships, and don't need that extra payload, orbital tankers are a waste since that's just extra mass you're putting up there when Starship has all the fuel it needs when it leaves the ground.

As far as producing more fuel than you can store, this should never come up.  There will be plenty of jobs that need doing in order to live on Mars and especially to get anything done beyond basic survival.  You make as much fuel as you need, then you turn off the production and all the people who were running the machinery are now free to do any number of other things that are needed.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 04/21/2019 11:39 am
120% of the proellant needed in ONE year... that would be 240% with perfect skies, in two years. Hence my suggestion to store propellant in orbit. You use up a goodly fraction of it getting it there, reducing storage requirements.  This assumes ZBO
Part of the trade off is storing it on the ground verses storing it on orbit.  Which is more efficient?

Or in the ground. You can store methane in suitable rock layers. LOx not. But you free up tank space for more LOx.

You can also store methane as clathrates. Makes storage easier when it's a "room" temperature solid.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 04/21/2019 11:41 am
Can anybody explain, how PV output is related to opacity/Tau?

Higher the TAU, lower the amount of sunlight (energy) reaches the ground as it is scattered by the dust.
Less energy reaching the ground, and the PV panels, less power is produced,

PV's can cope with indirect sunlight and so are less affected than raw Tau figures suggest, at least until you get high values.

OTOH, PV's don't like being covered with dust. But then there's actually not much dust per square metre in a Martian dust storm, and during high winds you get more cleaning events. All of which means there's no nice linear Tau to PV-output equation, just "higher Tau means less power, very high Tau means no power" rule of thumb.



BTW, the formula for optical depth is Direct (or "Beam") Transmission (T) = e^(-Tau),
where T is between 0 and 1, or 0% to 100%. Ie, Tau=1, T=35%; Tau-2, T=14%, etc.

For scattered light, there's a nice readable report from the Viking mission data: http://large.stanford.edu/courses/2017/ph240/black1/docs/nasa-tm-102299.pdf (http://large.stanford.edu/courses/2017/ph240/black1/docs/nasa-tm-102299.pdf) which is full of data, neat tables and graphs of values, plus the equations to get there. For PV you want the total irradiance figures.

Additionally, the Opportunity team posted weekly reports which usually (always?) had both Tau and PV-output.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 04/21/2019 11:52 am
Re: over-production rates.

With the apparent seasonal variation in the amount of sunlight available, it seems logical to put any "annual" (Mars year) maintenance requiring the ISRU systems to be taken off-line into that period. But you'll also likely have longer term maintenance that needs to be done every 5-10 years. So you wait for the big storms and do it all then. Then you run during what is normally the off-season to make up for production short-falls, since everything should be running at peak efficiency following maintenance.

Additionally, the dust in the atmosphere might help reflect other types of radiation as well, so you have another reason to do a bunch of outside maintenance during a global dust storm.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/22/2019 11:24 pm
I've been trying to figure out a cost for Martian solar energy:

For this estimation I will use a solar panel array built on Earth with the following characteristics:

Solar array characteristics

Efficiency   30%   This would require the development of cheap multijunction production cells. Large volumes of production would keep the cost low.

Fill factor   80%   This is a conventional average for good quality cells.

Mass   3,5 kg/m2   This is the NASA 2018 BIG challenge target of 3 kg/m2, plus 0,5 kg/m2 for ancillary equipment

Cost on Earth   800 $/m2   An estimate based on an average cost of 500$/m2 for conventional panels on Earth (this is very optimistic)

Transported by SpaceX Starship with other cargo and unfolded on Mars semi-autonomously. For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

The design is a tracking array. This allows for more energy production with the same peak power characteristics. The added complexity is estimated to be a small cost compared to the transportation costs from Earth. The moving mechanism would be fitted with elements allowing for a self cleaning phase for dust removal. The panels are mounted on a single rotating and extending boom, that allows for tight packing at transportation and can be unfolded using traction from a vehicle that can also serve to transport and set down the array, eliminating the need and mass of self extension mechanisms.

Solar panel cost on Mars

The cost would be 800$/m2 + 3.5 kg/m2 x 500$/kg = 2550 $/m2 of solar panel on Mars.

Solar panel energy production

The solar constant is estimated at 590 W/m2 over the whole year. Atmospheric dust losses are set at 20%. An additional surface dust factor of 10% is included. This lowers the solar illumination to 413 W/m2. Using solar tracking for 10 hours per day, the available energy per day is calculated as 413 W/m2 x 10h x 3600 s/h = 14 868 000 J.

The actual energy production should be 14 868 000 x 30% x 80% = 3 568 320 joules per day.

The installed power, based on the 10 hours of operation, should be 413 W/m2 x 30% x 80% = 99 W/m2. The same cells on Earth would have a power of about 99 x 1300/413 = 300 W/m2. The mass ratio metric is then 300 W/m2 / 3 kg/m2 = 100 W/kg. this seems safely conservative compared to recent NASA projections.

The availability of the solar panels is estimated at 95%, to account for repairs, tracking failures and other problems.

So every year a m2 of panel would produce about 3 568 320 x 365 x 0,95 /1e9 = 1,23 GJ/m2.

With an estimated life time of 20 years the total energy produced would be 20 x 1,23 = 24,7 GJ/m2. When divided by the cost of 2 550$ the bare cost of the energy would be 103 $/GJ. Majoring in financing, profit and uncertainties, we could expect a multiplying factor of 1.5, for a final cost estimate of 150 $/GJ for martian solar power. In other units this is 0,15 $/MJ, or 0,55$ per kWh.

An estimate based on less speculative 22% silicon solar cells would suggest using 200$ / GJ.

Making sense?  This would be a fun number to have for evaluating projects.  Energy in this case would be about 10 times more expensive than on Earth.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/22/2019 11:51 pm
For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

Where did you get this number ?
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/23/2019 12:07 am
For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

Where did you get this number ?
that's 500,000 per ton, $50,000,000 for 100 tons. At "Less than falcon 1 cost" that'll buy 10 launches, more than enough to refuel. Probably a bit highballed.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 12:57 am
For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

Where did you get this number ?
I got it from the contest information for the Mrs Society Colony design contest.  However, it is quite conservative compared to the figures Musk used in 2016, that works out to 140 $ per kg.  But that was for the large 12m BFS.  I guess for the smaller 9m Spaceship 500$ per kg is 'reasonable'
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/23/2019 03:01 am
(https://forum.nasaspaceflight.com/assets/39785.0/1557973.jpg)

What's the purpose of the complex arcing shapes seen on the PV support "legs?" Would a simple A-frame be lighter and cheaper here?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 03:13 am
(https://forum.nasaspaceflight.com/assets/39785.0/1557973.jpg)

What's the purpose of the complex arcing shapes seen on the PV support "legs?" Would a simple A-frame be lighter and cheaper here?
Pure fun. 😊 or just a bit more seriously I think we can afford elegance in form at the price point I see for these.  Plus they are visual stand ins for lifting points and tie downs that a real design would have. I really wanted curves, too, the cells are so square.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/23/2019 04:28 am
(https://forum.nasaspaceflight.com/assets/39785.0/1557973.jpg)

What's the purpose of the complex arcing shapes seen on the PV support "legs?" Would a simple A-frame be lighter and cheaper here?
Pure fun.  or just a bit more seriously I think we can afford elegance in form at the price point I see for these.  Plus they are visual stand ins for lifting points and tie downs that a real design would have. I really wanted curves, too, the cells are so square.

I too favor elegance in form, but is this it?

Once you have thousands of these stacked next to each-other, the cost starts to add up. I've never understood the philosophy of "saving up" good engineering decisions to pay for bad ones. Why not just accept the win and make electricity even cheaper?

Seems better to put the costly aesthetic features someplace where there's lots of people around to enjoy them, and where the cost:benefit ratio is better. Rather than a parade of 100,000x copies of the same heavy "elegant" frame in some vast faraway PV farm...
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/23/2019 09:30 am
For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

Where did you get this number ?
I got it from the contest information for the Mrs Society Colony design contest.  However, it is quite conservative compared to the figures Musk used in 2016, that works out to 140 $ per kg.  But that was for the large 12m BFS.  I guess for the smaller 9m Spaceship 500$ per kg is 'reasonable'

Based on the 9m design shown at IAC 2017, I'm calculating around $240/kg.

Specifically, Musk said BFR cost per launch will be less than Falcon 1 (see first slide below). We know Falcon 1 was $6 million per launch. He also said refilling will allow BFR to land 150 mT on Mars, and showed a slide (also attached below) that implies it will take 6 total BFR launches to do that (1 Starship + 5 tankers).

So $6 million / 150 mT would be $40/kg for each BFR launch to LEO.  6 launches would be $240/kg to Mars.

Obviously these numbers are subject to change, but I haven't seen anything more recent from Elon or SpaceX, only speculation.  Let me know if I've missed something.

Launch costs seem like a really important factor for figuring out how much various Mars power options will cost.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 04/23/2019 11:08 am
(https://forum.nasaspaceflight.com/assets/39785.0/1557973.jpg)

What's the purpose of the complex arcing shapes seen on the PV support "legs?" Would a simple A-frame be lighter and cheaper here?
Pure fun. 😊 or just a bit more seriously I think we can afford elegance in form at the price point I see for these.  Plus they are visual stand ins for lifting points and tie downs that a real design would have. I really wanted curves, too, the cells are so square.

There would be a lot of circular type structures which they could be compatible with. The various radii elements could serve as spare strengthening / mounting hoops for tanks and habitats, or put in the arches of ISRU barrel vault type constructions.

EDIT: removed random attachments from another post.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/23/2019 11:49 am
For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

Where did you get this number ?
I got it from the contest information for the Mrs Society Colony design contest.  However, it is quite conservative compared to the figures Musk used in 2016, that works out to 140 $ per kg.  But that was for the large 12m BFS.  I guess for the smaller 9m Spaceship 500$ per kg is 'reasonable'

Based on the 9m design shown at IAC 2017, I'm calculating around $240/kg.

Specifically, Musk said BFR cost per launch will be less than Falcon 1 (see first slide below). We know Falcon 1 was $6 million per launch. He also said refilling will allow BFR to land 150 mT on Mars, and showed a slide (also attached below) that implies it will take 6 total BFR launches to do that (1 Starship + 5 tankers).

So $6 million / 150 mT would be $40/kg for each BFR launch to LEO.  6 launches would be $240/kg to Mars.

Obviously these numbers are subject to change, but I haven't seen anything more recent from Elon or SpaceX, only speculation.  Let me know if I've missed something.

Launch costs seem like a really important factor for figuring out how much various Mars power options will cost.
Also, if the lift target was dropped from 150 tons to 100 tons, the number of refueling flights would go from 6 to 9. That may also be a factor in the cost per kilo to mars surface.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 11:59 am


What's the purpose of the complex arcing shapes seen on the PV support "legs?" Would a simple A-frame be lighter and cheaper here?
Pure fun.  or just a bit more seriously I think we can afford elegance in form at the price point I see for these.  Plus they are visual stand ins for lifting points and tie downs that a real design would have. I really wanted curves, too, the cells are so square.

I too favor elegance in form, but is this it?

Once you have thousands of these stacked next to each-other, the cost starts to add up. I've never understood the philosophy of "saving up" good engineering decisions to pay for bad ones. Why not just accept the win and make electricity even cheaper?

Seems better to put the costly aesthetic features someplace where there's lots of people around to enjoy them, and where the cost:benefit ratio is better. Rather than a parade of 100,000x copies of the same heavy "elegant" frame in some vast faraway PV farm...
Who knows?  the fist version was a vertical stick.  Much easier to model.  That seemed unstable, so it evolved to a triangle.  That meant trouble on un-even ground, and did not offer much protection for the panels during transportation.  A full surface rectangle was a good protector, but had large surfaces that were structurally useless.  A semi circular shape seemed like a good compromise, with two attachment points to the ground and a higher interconnecting bar to complete the structure.  The large arch needed a small beam to attach it to the pivot point.  The curve gave the assembly a certain inherent energy absorption feature, that I felt would be useful when installed.  The whole had an amusing Victorian look, that I enjoyed.
So this is really seats of the pants design.  The result is certainly not optimised, and does not need to be, as the basic function of this design is not to reflect a future reality, but to suggest the possibility of a simple, robust,  deployed tracking solar array on Mars.
BTW the PV farm will be vast, but will be extremely close, as we want to reduce distance and transportation losses.  PV is particularly useful for point of use installation, after all. So these might well be 'in the face' of the colonists.  In particular if they do build domes, these will likely be set in a 'sea' of theses things.  So perhaps they will want them to be pretty.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/23/2019 12:18 pm
For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

Where did you get this number ?
I got it from the contest information for the Mrs Society Colony design contest.  However, it is quite conservative compared to the figures Musk used in 2016, that works out to 140 $ per kg.  But that was for the large 12m BFS.  I guess for the smaller 9m Spaceship 500$ per kg is 'reasonable'

Based on the 9m design shown at IAC 2017, I'm calculating around $240/kg.

Specifically, Musk said BFR cost per launch will be less than Falcon 1 (see first slide below). We know Falcon 1 was $6 million per launch. He also said refilling will allow BFR to land 150 mT on Mars, and showed a slide (also attached below) that implies it will take 6 total BFR launches to do that (1 Starship + 5 tankers).

So $6 million / 150 mT would be $40/kg for each BFR launch to LEO.  6 launches would be $240/kg to Mars.

Obviously these numbers are subject to change, but I haven't seen anything more recent from Elon or SpaceX, only speculation.  Let me know if I've missed something.

Launch costs seem like a really important factor for figuring out how much various Mars power options will cost.
Also, if the lift target was dropped from 150 tons to 100 tons, the number of refueling flights would go from 6 to 9. That may also be a factor in the cost per kilo to mars surface.
The main cost of transportation to Mars is a factor of the number of reuses for Booster, tanker and Starship + development costs.  Not propellant.  9 to 6 for 150 to 100 is the same cost, when brought back to $/kg delivered and number o flights per kg.  But the development costs for the large 12m core would have been about the same as the ones for the 9m core, with much higher capacity.
It would be great if the cost was 250$ per kg.  But we should recognize that at this point, a bit of conservatism in an estimate that is already based on a reduction of cost of 1 to 500 might not be a bad thing, if the result is a cost that is acceptable to colonists.  150$ per MJ is about the price of electricity in isolated communities in Quebec, here on Earth, where off grid villages depend on diesel powered gensets to produce power.  This supports the idea that a Mars colony may be closer to village than to a military antarctic outpost.
The 500$ per kg was the suggestion of the Mars Society.  They were dreaming of a Mars colony when the consensus was 200 000$ per kg.  I bow down to their experience in this and am happy to use their number :-)
I'm not sure I follow your argument. We're assuming 5 million dollars per launch, after amortization and maintenance. Having to launch 9 flights instead of 6 in preparation for departure to mars means a 50% increase in launch costs.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 12:26 pm
For the Cost of Transportation to Mars, I simply use the cost proposed by SpaceX for their transportation system, 500$ per kg to Mars.

Where did you get this number ?
I got it from the contest information for the Mrs Society Colony design contest.  However, it is quite conservative compared to the figures Musk used in 2016, that works out to 140 $ per kg.  But that was for the large 12m BFS.  I guess for the smaller 9m Spaceship 500$ per kg is 'reasonable'

Based on the 9m design shown at IAC 2017, I'm calculating around $240/kg.

Specifically, Musk said BFR cost per launch will be less than Falcon 1 (see first slide below). We know Falcon 1 was $6 million per launch. He also said refilling will allow BFR to land 150 mT on Mars, and showed a slide (also attached below) that implies it will take 6 total BFR launches to do that (1 Starship + 5 tankers).

So $6 million / 150 mT would be $40/kg for each BFR launch to LEO.  6 launches would be $240/kg to Mars.

Obviously these numbers are subject to change, but I haven't seen anything more recent from Elon or SpaceX, only speculation.  Let me know if I've missed something.

Launch costs seem like a really important factor for figuring out how much various Mars power options will cost.
Also, if the lift target was dropped from 150 tons to 100 tons, the number of refueling flights would go from 6 to 9. That may also be a factor in the cost per kilo to mars surface.
The main cost of transportation to Mars is a factor of the number of reuses for Booster, tanker and Starship + development costs.  Not propellant.  9 to 6 for 150 to 100 is the same cost, when brought back to $/kg delivered and number o flights per kg.  But the development costs for the large 12m core would have been about the same as the ones for the 9m core, with much higher capacity.
It would be great if the cost was 250$ per kg.  But we should recognize that at this point, a bit of conservatism in an estimate that is already based on a reduction of cost of 1 to 500 might not be a bad thing, if the result is a cost that is acceptable to colonists.  150$ per MJ is about the price of electricity in isolated communities in Quebec, here on Earth, where off grid villages depend on diesel powered gensets to produce power.  This supports the idea that a Mars colony may be closer to village than to a military antarctic outpost.
The 500$ per kg was the suggestion of the Mars Society.  They were dreaming of a Mars colony when the consensus was 200 000$ per kg.  I bow down to their experience in this and am happy to use their number :-)
I'm not sure I follow your argument. We're assuming 5 million dollars per launch, after amortization and maintenance. Having to launch 9 flights instead of 6 in preparation for departure to mars means a 50% increase in launch costs.
I misread your comment.  Oups!  And removed my reply that was completely off.
But now I see that it there forever.  Ah well.  You are right.  Launch cost will increase from the original 140 to 210 or more.  I guess The Mars Society was still incredulous and boosted it to 500$.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/23/2019 12:36 pm
Also, if the lift target was dropped from 150 tons to 100 tons, the number of refueling flights would go from 6 to 9. That may also be a factor in the cost per kilo to mars surface.

Yes, that would be true if the lift target was dropped from 150 tons to 100 tons.

But where does this information come from? Did Elon or someone else in SpaceX mention this, or is it speculation?
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/23/2019 12:56 pm
Also, if the lift target was dropped from 150 tons to 100 tons, the number of refueling flights would go from 6 to 9. That may also be a factor in the cost per kilo to mars surface.

Yes, that would be true if the lift target was dropped from 150 tons to 100 tons.

But where does this information come from? Did Elon or someone else in SpaceX mention this, or is it speculation?
Technically, the lift targets moved to "100+" when the all-sealevel Starship was revealed at the #DearMoon press conference. We assume "100+" means 100 for the same reason "Cheaper than Falcon 1" means "About the same as Falcon 1"- a worst case scenario for planning purposes.
Title: Re: Power options for a Mars settlement
Post by: Lar on 04/23/2019 02:55 pm
Twark Main: I think it's a little premature to be critiquing the design of the supports for the arrays as being too round. These are conceptual renders, not engineering drawings.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 03:15 pm
What I'm really interested in is comments regarding the methodology and conclusions for Energy costs of Solar on Mars.
In particular:
-I'm using a 1.5 multiplication factor for financing over 20 years, this might be totally wrong.
-800$ per m2 for 30% solar arrays may be Ok or may be way off, or may be Ok in 4 or 5 years.
-500 $ per kg seems very optimistic, but the comments in the thread up to this points are that this is pessimistic.  Do we have more than a single data point from SpaceX on this?
-Should I include significant installation costs?  How do commercial photoelectric arrays connect up to the grid?  What are the voltages and transformers required?

My ultimate goals would be
1- To do the same analysis for nuclear.
 
2- To use the concept of embodied energy to be able to establish costs for In-situ preparation of materials, vs transportation.  If it costs 500 $ per kg to transport a given resource, that itself costs 5$ per kg, for 505$ per kg, we can compare it to, for example, 30 MJ /kg of energy for local production of the same resource at 0,15 $/MJ, Plus the cost of production equipment spread out over a certain volume of production and it's own transportation cost.  And we can then quantify the benefits of in-situ production.


Title: Re: Power options for a Mars settlement
Post by: RonM on 04/23/2019 03:44 pm
Your financing estimate is too low. High risk ventures like a Mars settlement don't get financing, they get investors. Don't bother adding a financing estimate since that doesn't factor in the comparison between technologies. Got to have cash for whatever system is selected.

The systems being compared need to be complete power production systems. PV panels need additional equipment to produce useful current at the outlet end, including power storage.

Transportation costs based on an optimistic statement by SpaceX isn't all that useful. Use a range of costs from low to high. If costs are very low then ISRU production becomes less likely (unless higher cost is acceptable for self-sufficiency). Don't forget the costs of setting up factories to build the power system parts. It's going to be a WAG estimate anyway.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/23/2019 04:41 pm
How far away from the raptor exhaust do the solar panels need to be in order not to be blown over by the exhaust gas pressure or damaged by flying debris?

This might be an issue as I have heard figures of 1-2km spacing between starships to prevent blast damage. If those figures ares correct then thats a lot of cable.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/23/2019 05:13 pm
How far away from the raptor exhaust do the solar panels need to be in order not to be blown over by the exhaust gas pressure or damaged by flying debris?

This might be an issue as I have heard figures of 1-2km spacing between starships to prevent blast damage. If those figures ares correct then thats a lot of cable.
Debris may fly 1-2 km, but that's when landing in unimproved train, not a prepared pad.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 05:16 pm
How far away from the raptor exhaust do the solar panels need to be in order not to be blown over by the exhaust gas pressure or damaged by flying debris?

This might be an issue as I have heard figures of 1-2km spacing between starships to prevent blast damage. If those figures ares correct then thats a lot of cable.
Yes, the power infrastructure often gets hand waved in.  If we have DC step up and step down converters to , let's say, 25 kVolts, then step back down to 480 volts locally, then it's less of a problem (or more common AC transformers and DC-AC converters on the cells).   2#0 wires could carry 120 Ampères of un-grounded current (one go, one return), or about 3 MVA for a few kg/m, with insulation.  2 km might be 2 to 3 tonnes of equipment.  500 MCM cable might carry 10 MVA, which I think is more or less standard?  If there is an electrical engineer in the area, feel free to set us right!!
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/23/2019 08:14 pm
My ultimate goals would be
1- To do the same analysis for nuclear.

From an engineering standpoint, I think nuclear is a no-brainier.  They're already working on small modular 4th gen nuclear power plants.

That doesn't mean I'm against solar. I think solar and nuclear complement each other, not only in meeting the typical demand curve, but also for redundancy.

But politically, there are still too many people that are afraid of nuclear, even though it's proven to be the safest source of energy on earth.  Google "deaths per TWh" for details.

So getting approval to launch a nuclear payload from earth would probably be a challenge.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 08:29 pm
My ultimate goals would be
1- To do the same analysis for nuclear.

From an engineering standpoint, I think nuclear is a no-brainier.  They're already working on small modular 4th gen nuclear power plants.

That doesn't mean I'm against solar. I think solar and nuclear complement each other, not only in meeting the typical demand curve, but also for redundancy.

But politically, there are still too many people that are afraid of nuclear, even though it's proven to be the safest source of energy on earth.  Google "deaths per TWh" for details.

So getting approval to launch a nuclear payload from earth would probably be a challenge.
Exactly, so is the challenge worth the effort?   Is nuclear a nice to have, or a requirement?  I expect this has already been done to death earlier on in this thread, but I was trying to look at this through a 'new' angle, i.e. an estimated cost to see if solar only can support a colony, or if a reduction in cost from nuclear would be significant.
My guess at this point is that if they are close, no one will develop nuclear.
Which is too bad because i'd love a good reactor for deep space exploration.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/23/2019 08:40 pm
From what Musk said (https://www.businessinsider.com/elon-musk-mars-iac-2017-transcript-slides-2017-10#-35) at IAC 2017, it appears SpaceX is going all-solar:
Quote from: Elon Musk
So we should, particularly with six ships, have plenty of landed mass to construct the propellant depot, which will consist of a large array of solar panels — very large array — and then everything necessary to mine and refine water, and then draw the CO2 out of the atmosphere, and then create and store deep-cryo CH4 and O2.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/23/2019 08:58 pm
From what Musk said (https://www.businessinsider.com/elon-musk-mars-iac-2017-transcript-slides-2017-10#-35) at IAC 2017, it appears SpaceX is going all-solar:
Quote from: Elon Musk
So we should, particularly with six ships, have plenty of landed mass to construct the propellant depot, which will consist of a large array of solar panels — very large array — and then everything necessary to mine and refine water, and then draw the CO2 out of the atmosphere, and then create and store deep-cryo CH4 and O2.
Yes, Shotwell also confirmed this when she mentioned trying to get some nuclear material for exploring ideas about nuclear engines.  It didn't happen.  I guess nuclear would need to be looked at as a second stage of development.  When the colony starts to really grow.  But it's hard to see who would invest in nuclear on MArs if there is no market on Earth.
Title: Re: Power options for a Mars settlement
Post by: GregTheGrumpy on 04/23/2019 09:05 pm
<snip for size> ... But it's hard to see who would invest in nuclear on MArs if there is no market on Earth.

I would think the persons who would elect to go go Mars, on the whole, would find no problem with nuclear.  I find the who bug-a-boo around nuclear irrational.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/24/2019 12:29 am
Part II

Nuclear energy Design

Nuclear reactor designs for Mars might be based on the Kilopower 10 kW nuclear reactor. It uses Highly Enriched Uranium(HEU), presumably at 20% concentration.

Power   10 kW electric,  43 kW thermal,  solid core, sodium heat pipe cooled reactor. Stirling engines.
Efficiency   23%   
Mass of reactor   7 We / kg   
A 10 kWe reactor would include 43.7 kg of 235U and mass about 1430 kg.

Cost on Earth   400 000$   composed of:
5500 $/kg of HEU (240 000$)
100$ per kg for fabrication of the rest (140 000$)(ref needed).

Nuclear power station cost on Mars

Using 500$ per kg for transportation of 1430 kg and 400 000$ for construction, the cost is about 1 100 000$.

Nuclear energy production

The reactor, operating at 95% availability for 10 years will produce 10 000J x 10y x 365d x 24h x3 600s x0,95 = 3 e12J or 3000 GJ

When divided by the cost of 1 100 000$ the bare cost would be about 300 $/GJ. If we have the same multiplication factor of 1,5 then the final cost would be 500 $/GJ. this is about 3 times more expensive than solar.

If the nuclear reactor could be refurbished and refuelled for another ten years, for about 500 x 43,7 + 240 000 = 260 000$ then the cost would be 1 360 000 / 3000 = 226$/GJ x 1,5 = 339$/GJ or about twice the cost of solar.

So there might be little incentive for nuclear on Mars.  Of course the error on these figures may be so large that they overlap ,  Or I may have dropped a zero here or there  ;-)
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/24/2019 02:45 am
Cost for nuclear isn't the factor, I think.  24 hours a day operation is what I was thinking.  Solar is only good for a maximum of 12 hours.  Then ADD in the cost and weight of battery banks that has to be shipped to Mars for night storage.  So you have to have twice the solar panels to be able to charge for night time operations + the batteries for night use. 

lamontagne, no disrespect, you must not be from America.  We put our $ dollar signs in front of the amounts, was kind of hard to follow. 

Nuclear will not need battery storage, once the reactor is up and running.  American super carriers and submarines can operate for up to 50 years without refueling.  A lot depends on the nuclear design.  24 hour operation will be needed for large scale manufacturing and processing of metals and other operations.  So far Tesla batteries are supposed to be good for 10 years.  Solar panels will depend on dust storm scratches and damages.  Nuclear can run regardless of what the weather outside is doing and run at night.  It takes up less space too.  Solar panels will have to be located away from rocket launches and landings due to dust and the power transmitted over distance from a solar farm.  A completely self contained nuclear facility can be buried nearby but not to far away and not be affected by rocket traffic.   
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 04/24/2019 04:01 am
I haven't seen methanol energy storage considered yet.

Advantages:

- Methanol production can be very similar to methane production.  The critical difference is carbon monoxide, not carbon dioxide, is the carbon source.

- Methanol can be stored in bladders.

- Methanol can be turned into methane using microbes a Martian sewage treatment plant would use, perhaps methanogenic coccus.
https://jb.asm.org/content/jb/153/2/1051.full.pdf (https://jb.asm.org/content/jb/153/2/1051.full.pdf)

Disadvantages:

- A significant carbon monoxide source is needed*.

- I haven't done much homework on methanol production. That's all I have for now.

What I've tried to conceptualize is storing fuel on the Martian surface in what are basically glorified above-ground swimming pools.  The goals are ease of assembly, minimizing packed volume, and the flexibility to be used for a wide variety of liquids a Martian colony might want to store.

* I'm not sure that having a carbon monoxide source is actually a disadvantage.  Having carbon monoxide allows a range of useful chemistry.  One option to consider is using the Mond process to purify nickel.  Purified nickel can be used as the catalyst in Sabatier reactors.  What we really want from the coal we use in steel making is the carbon to make carbon monoxide.  Aluminium production using carbon monoxide is also possible.  Having carbon monoxide production makes sense.  If the longer term goal is providing carbon monoxide to Martian metallurgy proving the infrastructure creating a strategic methanol reserve makes a good bit of sense.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 04/24/2019 04:02 am
You will always need batteries as backup when the primary power is not available.  Especially when the power systems are new and growing. 
 
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/24/2019 04:05 am
Compare actual space-rated nuclear to actual space-rated solar.

The near-term nuclear is Kilopower. Solar is about 3 orders of magnitude cheaper, and can be just as light or lighter, even including the weight of the batteries and everything.

Nuclear is great. But solar is really, REALLY good. The main use will be producing propellant, maybe 90% of the use. That means if a dust storm reduces power by 90% for a couple weeks on average, just pause propellant production and you're good.

Or, if you prefer, use some of the propellant to run emergency generators (for the rare, once-in-a-couple-decades really long storm). Or use both solar and a small amount of nuclear.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 04/24/2019 05:45 am
1000!
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 04/24/2019 06:00 am
The design is a tracking array. This allows for more energy production with the same peak power characteristics. The added complexity is estimated to be a small cost compared to the transportation costs from Earth. The moving mechanism would be fitted with elements allowing for a self cleaning phase for dust removal. The panels are mounted on a single rotating and extending boom, that allows for tight packing at transportation and can be unfolded using traction from a vehicle that can also serve to transport and set down the array, eliminating the need and mass of self extension mechanisms.
How does this compare with just unrolling sheets of cells on the ground?   I'd think a panel assembly stiff enough to be rotated by a tracking mechanism would be substantially heavier than one that merely had to lie flat.   With a flat-on-the-ground system, you could send more cells and cover more area for the same mass budget; they'd have lower average production per cell but perhaps greater overall production, and you wouldn't have to worry about the tracking mechanism breaking while the panels were pointed the wrong way.   
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/24/2019 11:03 am
Solar is only good for a maximum of 12 hours.  Then ADD in the cost and weight of battery banks that has to be shipped to Mars for night storage.  So you have to have twice the solar panels to be able to charge for night time operations + the batteries for night use.

I suspect it's much less than 12 hours a day.

The angle of the sun has a lot to do with  it.  If the angle isn't optimal, the power output goes down significantly.

On earth, in the U.S., most areas get an average of 4-5 solar hours per day. For example, if a solar panel is rated for 200 watts, you'll get an average of 800-1000 watt-hours per day. Obviously, the panel will be generating power more than 4-5 hours/day, but for most of that time it'll be generating less than 200 watts, due to the angle of the sun and atmospheric conditions. So they came up with this solar hours/day figure to help calculate the amount of energy solar panels will generate in various locations.

This brings up a good point. We really should be talking about energy options for Mars, not power options.
Energy = Power x Time.
And especially with solar, we need to think in terms of Kilowatt hours (kWh), not Kilowatts (kW).

On Mars, I don't know what the average solar hours/day figure will be, but I suspect it'll be much less than 12.
Obviously, Mars doesn't have clouds like earth, but the angle of the sun hitting the solar panel still matters, and this will vary significantly throughout the Martian day.  I don't know where the first Starships will land, but it will need to be someplace where water ice is plentiful. If there's not enough water near the equator, they may go to a higher latitude. In this case, the amount of solar energy will be reduced.  There are other factors: For example, Mars is further from the sun, but it has a thinner atmosphere. I don't know all the specific details, but the main point is that solar power may be a lot more variable than many people are thinking.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 04/24/2019 11:57 am
The design is a tracking array. This allows for more energy production with the same peak power characteristics. The added complexity is estimated to be a small cost compared to the transportation costs from Earth. The moving mechanism would be fitted with elements allowing for a self cleaning phase for dust removal. The panels are mounted on a single rotating and extending boom, that allows for tight packing at transportation and can be unfolded using traction from a vehicle that can also serve to transport and set down the array, eliminating the need and mass of self extension mechanisms.
How does this compare with just unrolling sheets of cells on the ground?   I'd think a panel assembly stiff enough to be rotated by a tracking mechanism would be substantially heavier than one that merely had to lie flat.   With a flat-on-the-ground system, you could send more cells and cover more area for the same mass budget; they'd have lower average production per cell but perhaps greater overall production, and you wouldn't have to worry about the tracking mechanism breaking while the panels were pointed the wrong way.   


Unrolling on the ground at the equator, you get about 72% of the available energy compared to a 2-axis tracker. This ignores the effect of windblown dust, which would be less of an issue on a panel elevated off the ground and angling. Self-cleaning technology would take care of most of the dust.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/24/2019 01:23 pm
Cost for nuclear isn't the factor, I think.  24 hours a day operation is what I was thinking.  Solar is only good for a maximum of 12 hours.  Then ADD in the cost and weight of battery banks that has to be shipped to Mars for night storage.  So you have to have twice the solar panels to be able to charge for night time operations + the batteries for night use. 

lamontagne, no disrespect, you must not be from America.  We put our $ dollar signs in front of the amounts, was kind of hard to follow. 

Nuclear will not need battery storage, once the reactor is up and running.  American super carriers and submarines can operate for up to 50 years without refueling.  A lot depends on the nuclear design.  24 hour operation will be needed for large scale manufacturing and processing of metals and other operations.  So far Tesla batteries are supposed to be good for 10 years.  Solar panels will depend on dust storm scratches and damages.  Nuclear can run regardless of what the weather outside is doing and run at night.  It takes up less space too.  Solar panels will have to be located away from rocket launches and landings due to dust and the power transmitted over distance from a solar farm.  A completely self contained nuclear facility can be buried nearby but not to far away and not be affected by rocket traffic.   
The calculations are for 10 hrs solar, 24 hours nuclear, so it is included.
Reduced solar by 10% for dust and damage, and another 5% for maintenance.

Very little night storage required.  Stop hydrogen electrolysis, close down greenhouse lights, have a well insulated base, the requirements for batteries go way down.  I expect 5% battery backup would be enough.  In the long term would add some compressed air storage once in-situ is in place to make tanks.

French Canadian raised on the metric system  :-)  will rewrite to US standards.

Distance from landing is a non issue once a spaceport is built. And ships only  land once every two years.  And that's what high voltage transmission lines are for.  25 kV or 125 KV AC or DC can carry huge power loads on relatively small lines. .

You can't bury the radiators, at least the ones shown on NASA versions of kilopower.  Radiator damage would be just as bad, probably worse, than damages to solar panels.

Nuclear reactors, at least the big ones, don't modulate well.  Demand will vary on Mars and do Kilopower reactors react well to stops and starts?  Or do they just dump the heat?

Regarding Nuclear on submarines and carriers, let's not forget that money is no object there.

I'm not bashing nuclear, just trying to use objective numbers.  For the moment nuclear is the loser with my numbers.  I'll be glad to change them, given data. 
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/24/2019 01:27 pm
Space-rated nuclear is super expensive, but as a reliable backup for keep-alive power, it's not a bad idea if we're going to develop it anyway (which we should, see Kilopower uses for probes, etc). So most of the energy should be produced with solar and maybe a small amount of nuclear for resiliency.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/24/2019 01:32 pm
The design is a tracking array. This allows for more energy production with the same peak power characteristics. The added complexity is estimated to be a small cost compared to the transportation costs from Earth. The moving mechanism would be fitted with elements allowing for a self cleaning phase for dust removal. The panels are mounted on a single rotating and extending boom, that allows for tight packing at transportation and can be unfolded using traction from a vehicle that can also serve to transport and set down the array, eliminating the need and mass of self extension mechanisms.
How does this compare with just unrolling sheets of cells on the ground?   I'd think a panel assembly stiff enough to be rotated by a tracking mechanism would be substantially heavier than one that merely had to lie flat.   With a flat-on-the-ground system, you could send more cells and cover more area for the same mass budget; they'd have lower average production per cell but perhaps greater overall production, and you wouldn't have to worry about the tracking mechanism breaking while the panels were pointed the wrong way.
I would expect the very first arrays to be rolled out.  Then I think they will switch to tracking for the increase in energy (not power).  For the first generation the main product on Mars will be fuel, and therefore electrolysis will be used and that will run as long as there is light, so it can use all the energy. 
Tracking gives up to 40% more energy (but some say only 25%).  But all the numbers on that are rather fuzzy, because the technologies are changing so fast.
I expect tracking structure will be manufactured is situ as soon as possible.  This makes them unbeatably cheap.

I have made a 5% provision for repairs.  Colonists need to have something to do!
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/24/2019 01:41 pm
Tracking arrays also are a lot more dust-resistant. You can tilt them to remove dust, and being situated higher means you're less likely to get dust on them in the first place and if you do get dust that just tilting somehow won't remove (and that is pretty effective all by itself), it's easier for the wind to blow it off.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/24/2019 01:42 pm
Solar may be fine at first, but if you need 24 hours a day 7 days a week operations in metal smelting and manufacturing, you will eventually have to get nuclear power.  Fossil fuels aren't available on Mars and on earth, residential takes about 1/3 of the energy use, small commercial businesses and small industry takes about 1/3 and large industrial takes about 1/3 of all energy consumed.  If you go from small habitats and small scale food production to larger habitats, industrial production, and massive large scale food production there will need to be nuclear power. 

Lithium for batteries is a finite material, or other means of power storage will need to be worked out (flywheels maybe)  Nuclear only takes a small amount of material to operate for years.  Granite rock is 5% uranium and we have an abundance of mountains on earth.  Maybe on Mars also. 

I agree solar is best for starting, but for growing, it will require massive amounts of power that can be available 24 hours a day.  At least within 50 years after starting. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/24/2019 01:54 pm
Solar may be fine at first, but if you need 24 hours a day 7 days a week operations in metal smelting and manufacturing, you will eventually have to get nuclear power.  Fossil fuels aren't available on Mars and on earth, residential takes about 1/3 of the energy use, small commercial businesses and small industry takes about 1/3 and large industrial takes about 1/3 of all energy consumed.  If you go from small habitats and small scale food production to larger habitats, industrial production, and massive large scale food production there will need to be nuclear power. 

Lithium for batteries is a finite material, or other means of power storage will need to be worked out (flywheels maybe)  Nuclear only takes a small amount of material to operate for years.  Granite rock is 5% uranium and we have an abundance of mountains on earth.  Maybe on Mars also. 

I agree solar is best for starting, but for growing, it will require massive amounts of power that can be available 24 hours a day.  At least within 50 years after starting.
We also have an abundance of sun :-)  And crushing mountains and sifting out the uranium and then enriching it takes a lot of energy.  Of course, making panels is also expensive, but the cost keeps going down.
I absolutely agree that nuclear may be a long term solution.  However solar still has a lot of growth space available, and the cost of nuclear will need to be compared to the cost of cheap, locally produced energy storage systems.  This looks like compressed air storage to me, big dumb tanks but fancy compressors and generators.
The generators and compressors will essentially replicate the same elements in a nuclear power facility.  A reactor is also a big dumb tank, with a fancy core.  The differential will be safety systems and the cost of nuclear fuel.  Nuclear might win out because of the influence of dust storms and the effect of seasonal variations on industry.  The storage capacity of nuclear fuel would probably give it a good edge.

Until foods is produced out in the martian air, food production (greenhouses) will require a large fraction of industrial power, much more than on Earth.  And this will naturally be variable, unless it is entirely artificial and deliberately staggered to provide a steady load.
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 04/24/2019 02:18 pm
 One of the best features of the kilopower design is that it's self regulating with no moving parts. The core stays in a fairly narrow temperature range from the reaction decreasing if it gets hotter and increasing when you draw more heat. You can remove the heatpipe altogether without the reactor overheating. That same feature also keeps heat output constant as the fuel is used up. No moving parts in the core. They hope for a 40 year lifespan with no maintenance except Sterling replacement, which is designed to be fast and easy.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/24/2019 02:27 pm
One of the best features of the kilopower design is that it's self regulating with no moving parts. The core stays in a fairly narrow temperature range from the reaction decreasing if it gets hotter and increasing when you draw more heat. You can remove the heatpipe altogether without the reactor overheating. That same feature also keeps heat output constant as the fuel is used up. No moving parts in the core. They hope for a 40 lifespan with no maintenance except Sterling replacement, which is designed to be fast and easy.
I think you also need to replace the fuel?  I saw 10 years in a paper about them.  Seems like a great design.  Rooting for them to succeed and go on to bigger ones.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/24/2019 05:11 pm
One of the best features of the kilopower design is that it's self regulating with no moving parts...

The kilopower (https://www.nasa.gov/sites/default/files/atoms/files/ns_kilopower_fs_180111.pdf) design uses highly enriched uranium, which is highly radioactive.
In the event of a launch failure, it could end up becoming a dirty bomb.
That's why I suspect it will be hard to get approval to launch any significant amounts of highly enriched uranium.

By contrast, 4th generation reactors use non-radioactive materials as fuel (depleted uranium, thorium, etc.).
For example, we have enough depleted uranium to power earth for hundreds of years at today's energy levels.
Internally, a 4th generation reactor breeds (https://en.wikipedia.org/wiki/Breeder_reactor) radioactive fission fuel from these non-radioactive sources.
To get this breeding process started, they do require a small amount of radioactive fuel, e.g. Plutonium.
But this small amount of starter material probably wouldn't be hazardous in the event of a launch failure.

Bill Gates is funding a company that's working on a traveling wave reactor (https://en.wikipedia.org/wiki/Traveling_wave_reactor) for use in African rural areas.
These reactors last 60 years without any refueling. I don't know what the smallest viable TWR is,
but I have heard they're working on other types of small, modular 4th generation reactors.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 04/24/2019 05:27 pm
One of the best features of the kilopower design is that it's self regulating with no moving parts...

The kilopower (https://www.nasa.gov/sites/default/files/atoms/files/ns_kilopower_fs_180111.pdf) design uses highly enriched uranium, which is highly radioactive.
In the event of a launch failure, it could end up becoming a dirty bomb.
That's why I suspect it will be hard to get approval to launch any significant amounts of highly enriched uranium.

By contrast, 4th generation reactors use non-radioactive materials as fuel (depleted uranium, thorium, etc.).
For example, we have enough depleted uranium to power earth for hundreds of years at today's energy levels.
Internally, a 4th generation reactor breeds (https://en.wikipedia.org/wiki/Breeder_reactor) radioactive fission fuel from these non-radioactive sources.
To get this breeding process started, they do require a small amount of radioactive fuel, e.g. Plutonium.
But this small amount of starter material probably wouldn't be hazardous in the event of a launch failure.

Bill Gates is funding a company that's working on a traveling wave reactor (https://en.wikipedia.org/wiki/Traveling_wave_reactor) for use in African rural areas.
These reactors last 60 years without any refueling. I don't know what the smallest viable TWR is,
but I have heard they're working on other types of small, modular 4th generation reactors.
In 15 years MIT's SPARC fusion reactor should be coming online. Mars would be a natural place to test a reactor design, and if I'm reading the diagrams correctly, the reactor is only 12m or so across- an ITS class rocket could carry an entire reactor in one piece, without the problems associated with fissile materials.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/24/2019 05:36 pm
Reactors use so little fuel, the fuel can be launched separately in a lead box.  In case of rocket failure the lead box of a handful of fission material will be shielded when it crashes into the ocean.  It can then be recovered.  It can also be placed in a capsule with LAS in case of failure, it can be recovered.  Fuel is small compared to the reactor itself which can be launched separately. 

Problems with solar:  Dust storms, enough power for large greenhouses at night, and large industrial applications, battery storage with lithium in short supply, and large solar arrays that may take several launches for enough panels and batteries.

Problems with nuclear:  Radiation shielding, transport of fuel.  I see far fewer problems to be overcome here, especially when expanding needs arise since equipment is smaller. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/24/2019 06:02 pm
Reactors use so little fuel, the fuel can be launched separately in a lead box.  In case of rocket failure the lead box of a handful of fission material will be shielded when it crashes into the ocean.  It can then be recovered.  It can also be placed in a capsule with LAS in case of failure, it can be recovered.  Fuel is small compared to the reactor itself which can be launched separately. 

Problems with solar:  Dust storms, enough power for large greenhouses at night, and large industrial applications, battery storage with lithium in short supply, and large solar arrays that may take several launches for enough panels and batteries.

Problems with nuclear:  Radiation shielding, transport of fuel.  I see far fewer problems to be overcome here, especially when expanding needs arise since equipment is smaller.
Solar solutions: Insulate the greenhouses and use modern artificial lighting for plant growth.  Do not run large industrial processes at night, use compressed air storage rather than chemical batteries.
Dust storms are a real fundamental problem though.  Martian society relying solely on Solar would need to learn how to operate on low power levels during storms, that can last many months.

Nuclear solutions: Bury the reactor, shield the reactor with regolith.  Nuclear reactors need radiators that can be very expensive.  Space rated reactors do not quite exist yet
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/24/2019 06:16 pm
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/24/2019 06:16 pm
Reactors use so little fuel, the fuel can be launched separately in a lead box.  In case of rocket failure the lead box of a handful of fission material will be shielded when it crashes into the ocean.  It can then be recovered.  It can also be placed in a capsule with LAS in case of failure, it can be recovered.  Fuel is small compared to the reactor itself which can be launched separately.

I'm more concerned about the rocket exploding somewhere near the launch pad. Once it's out over the ocean, or high up in the atmosphere, exploded radioactive material would tend to disperse to non-harmful levels.

Yes, you could launch it separately in a capsule with a launch abort system, but we just saw one of those explode on the pad.

Yes, you could put it in a lead box, but how will that fare in an explosion?

Also, the kilopower white paper (https://www.nasa.gov/sites/default/files/atoms/files/ns_kilopower_fs_180111.pdf) said "The core is a solid block of a uranium alloy", so it may be significantly larger than pure uranium.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/24/2019 06:21 pm
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.

Are you sure (http://adsabs.harvard.edu/abs/1981Geokh.......10B)?
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 04/24/2019 06:48 pm
I've said this before, but wind power is still viable. Dust storm wind speeds generates viable energy for them.

"1% air density" I hear you all cry. The trick is that power per swept area varies as the cube of velocity. The turbines are huge, but also light. A 1 tonne turbine, about 50 metres tall, would produce 10kW+ in a 25m/s wind. Not hundreds of kW like on Earth for the same size, but it's dust storm power without nuclear. Enough to keep the lights on and some of the crops growing without dipping into fuel stocks.

https://spectrum.library.concordia.ca/36176/1/low_reynolds_number.doc
Title: Re: Power options for a Mars settlement
Post by: raketa on 04/24/2019 07:14 pm
One of the best features of the kilopower design is that it's self regulating with no moving parts...

The kilopower (https://www.nasa.gov/sites/default/files/atoms/files/ns_kilopower_fs_180111.pdf) design uses highly enriched uranium, which is highly radioactive.
In the event of a launch failure, it could end up becoming a dirty bomb.
That's why I suspect it will be hard to get approval to launch any significant amounts of highly enriched uranium.

By contrast, 4th generation reactors use non-radioactive materials as fuel (depleted uranium, thorium, etc.).
For example, we have enough depleted uranium to power earth for hundreds of years at today's energy levels.
Internally, a 4th generation reactor breeds (https://en.wikipedia.org/wiki/Breeder_reactor) radioactive fission fuel from these non-radioactive sources.
To get this breeding process started, they do require a small amount of radioactive fuel, e.g. Plutonium.
But this small amount of starter material probably wouldn't be hazardous in the event of a launch failure.

Bill Gates is funding a company that's working on a traveling wave reactor (https://en.wikipedia.org/wiki/Traveling_wave_reactor) for use in African rural areas.
These reactors last 60 years without any refueling. I don't know what the smallest viable TWR is,
but I have heard they're working on other types of small, modular 4th generation reactors.
We could use Starliner or Crew Dragon to bring on orbit. In case of failure of rocket, crew escape system will keep radioactive material inside cabin and land back on earth.
Title: Re: Power options for a Mars settlement
Post by: Magnus_Redin on 04/24/2019 07:32 pm
I have the boring and expensive opinion that diversity is of utmost importance for a Mars settlement.

Have several types of sun tracking and flat solar arrays with a power budget that allows normal operation with 100% failure of one type of array, tracker, power converter etc. Diversity is more important then finding the optimal system and making it perfect.

Have more then one type of nuclear reactor for exactly the same reason.

Have local large capacity UPS style battery storage for various critical functions. Use several types and use different types for redundant systems.

Have several types of large capacity long term battery energy storages.

What I find more interesting is the already established standards for AC and DC power on spaceships, ISS and aviation. Wich should be used in a Mars settlement and what should be added? Should we even have household 50 or 60 Hz? This is a kind of decision that one can get stuck with indefinitely, like Japan has two incopatible AC grids.
Title: Re: Power options for a Mars settlement
Post by: RonM on 04/24/2019 07:48 pm
What I find more interesting is the already established standards for AC and DC power on spaceships, ISS and aviation. Wich should be used in a Mars settlement and what should be added? Should we even have household 50 or 60 Hz? This is a kind of decision that one can get stuck with indefinitely, like Japan has two incopatible AC grids.

This is a good point. With something as difficult and expensive as building a Mars settlement, selecting the right grid standard will be key.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/24/2019 08:43 pm
A 1 tonne turbine, about 50 metres tall, would produce 10kW+ in a 25m/s wind. Not hundreds of kW like on Earth for the same size, but it's dust storm power without nuclear. Enough to keep the lights on and some of the crops growing without dipping into fuel stocks.

I like the idea of dipping into fuel stocks.  The first manned mission will have 2 crew ships for redundancy.  Two return ships would be more comfortable, but they only need 1 to get home. Assuming they can produce enough propellant for 2 ships under nominal conditions, if dust storms are more frequent than normal, they can dip into that extra propellant reserve and still have enough propellant for 1 ship.
Title: Re: Power options for a Mars settlement
Post by: Magnus_Redin on 04/24/2019 08:45 pm
There has been lots of stuff written on grid standards.

Three phase AC power is outstanding for cheap and robust high capacity grids that powers lots of heavy rotating machinery and has to transmit power over long distances.

16 2/3 Hz is the lowest frequenzy used in Europe, its 50/3 Hz to be able to use rotating converters and such are still maintained and new built next to be used next to the solid state ones due to their robustness and ability to produce reactive power. This is an historical artifact from very early grids when early technology low frequency motors gave  more torque and thus was used for electrified rail. In modern times it has been proposed for grid connecting offshore wind power plants with only transformers at sea and a converter on land, the key feature being the cable capacitance being a neglible annoyance when the frequency is low.

50 och 60 Hz do not matter, either is as good.

400 Hz is a common aviation standard. It was invented to save mass in the rotating machinery and transformers due to less iron being needed for the magnetic flux. This was done before solid state electronics and it also makes it easier to rectifie into a stable DC for high performance electronics and thus was also used for ground based radars etc. But it might not work with the needed cable lenghts.

The extremely common DC/DC converters are a simmilar idea since they use transformers at way higher internal frequency and thus the transformers can be realy tiny. It is nowadys fairly cheap to turn any AC/DC into any other AC/DC but you still add cost, power consumtion and failure points for every added unit.

Every battery bank or set of solar pannels will have DC/DC or DC/AC converters and the same will probably be true for small nuclear reactors.

The voltage level is for the short distances a trade off between the pysical security of low voltages and the less mass and space needs for high voltages. The difference in insulation needs and mass are almost identical for say 24 or 240V but you only need 1/10 of the copper. For long distances is higher voltages important for minimising transmission losses. Edisons DC powerplants could only feed city blocks, AC grids that can reach 400 kV or even 800 kV span continents.

The car industry has experimented a lot with intermediate DC voltages. 6V DC fell out of favor for being to weak and regular cars got stuck on 12V DC while trucks and tractors often run on 24V DC. This depended on lead acid batteries and the starter motor as the key capacity deciding component. Light hybrid cars are around 80 V DC and there there seems to be a sweet spot for securily using basically 12/24 V components in the wet, corrosive and nasty car environment for 10-20 years. This is maybe relevant for wet and dirty in space and on mars living spaces and preassurised industrial facilities? Todays heavy electric cars that can run for hundreds of km use hundreds of volts to have reasonably sized cables and power electronics.

One point with three phase 110/200V 60 Hz or 240/400V 50 Hz is that it would make it easier to import machinery if we suceed in getting the launch costs realy low and actually get a settlement going. I would then go for the higher voltage level for efficiency and get 50 Hz as a side effect.

Sady I know almost nothing about the ISS power systems.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/25/2019 12:13 am
Teslas have 480V DC supercharger stations,  for 400V batteries.  LEDs and solar panels are both DC.  Modern power electronics are available that can step up and down to practically any voltage with high efficiency. 
Large DC installations are also used in modern server farms.  And computers and all electronics are DC.
It is very likely that all martian vehicles will have batteries, and DC chargers.
More and more modern motors have variable frequency drives, and could just as well be DC with the VFD using DC to create variable AC and speed control of low cost squirrel cage motors.

So my guess is that it would be tempting to go DC for Mars and forget AC completely.  Overall it would probably be more efficient.

However, 60 HZ AC systems are so common and optimized that they make a lot of sense as well.  But it does seem strange to convert the DC to AC, then step up to high voltage, step down to distribution 480 or 240V or 120 and then eventually power mostly DC systems.



Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/25/2019 12:18 am
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.

Are you sure (http://adsabs.harvard.edu/abs/1981Geokh.......10B)?
I guess not. Previous sources suggested Mars was depleted in Uranium and Thorium, but if you've found evidence otherwise, I cannot say for sure.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/25/2019 12:24 am
Nuclear's greatest advantage on Mars, compared to solar, might be the energy stored in the fuel, rather than the reactor itself.  For short term overnight storage there are a number of possible technologies, but nothing beats nuclear for months and years of energy storage.  Stored propellant could be a kind of stopgap,  but it would make more sense to simply reduce/suspend fuel production during dust storms. Dust storms are not totally opaque, and photovoltaics still function up to a point.
Propellant production will use up to 40% of a colony's power until there is a wide range of in-situ production and the proportion of cargo from Earth goes down.  So shutting it down should give a colony the power needed for other operations.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/25/2019 12:45 am
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.

Are you sure (http://adsabs.harvard.edu/abs/1981Geokh.......10B)?
I guess not. Previous sources suggested Mars was depleted in Uranium and Thorium, but if you've found evidence otherwise, I cannot say for sure.
A quick literature search turns these up:
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA04257
And the joined paper.

It would seem that thorium is the same as on Earth in basaltic rocks, and there are a lot of those.  There may be concentrations due to ancient weathering/water. 
I didn't see anything explicitly stating less thorium or uranium ,but it wasn't much of a search  :-)
Title: Re: Power options for a Mars settlement
Post by: launchwatcher on 04/25/2019 05:48 am
The kilopower (https://www.nasa.gov/sites/default/files/atoms/files/ns_kilopower_fs_180111.pdf) design uses highly enriched uranium, which is highly radioactive.
Huh?   Highly enriched uranium is mostly u-235, with a half life of approximately 700 million years.  It is not dangerously reactive by itself.
Quote
In the event of a launch failure, it could end up becoming a dirty bomb.
Only if the fuelled reactor was operated prior to launch (converting some of the U-235 into mixed fission products, some of which which are dangerously radioactive).
Quote
That's why I suspect it will be hard to get approval to launch any significant amounts of highly enriched uranium.
I'd think the proliferation issue is the real worry (highly enriched u-235 is comparatively easy to make into a fission bomb).
Title: Re: Power options for a Mars settlement
Post by: Pete on 04/25/2019 06:16 am
  Granite rock is 5% uranium and we have an abundance of mountains on earth.

This info is wrong.

No, that's not strongly enough stated.

This statement is completely, absolutely, and I suspect deliberately lies.

Please look up some facts before commenting on this again.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/25/2019 06:50 am
Not exactly a lie, but I did read that in a book pushing nuclear power and I was suprised it said 5%.  I can't find the book right now.  I checked Wikipedia, some granite does have high concentrations of uranium and thorium.  This can create a radon problem with some granite counter tops.  But if there is granite on Mars, there may be enough to mine for nuclear power. 
Title: Re: Power options for a Mars settlement
Post by: Pete on 04/25/2019 07:59 am
The usual figure is 10 to 20 parts per million, for granite that is "rich" in uranium.

That's a bit less than the 50 000 ppm you are stating.


Granite's Uranium content is relevant only as a potential source of trace radioactive products, mainly Radon.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/25/2019 08:10 am
The book I read about was stating that America had the potential to support a population the size of China with our current standard of living.  The author stated that granite could be pulverized and the uranium extracted to supply all our power with nuclear power for centuries.  I read this about 40 years ago and it impressed me as to the power potential of nuclear power with very little fuel.  It was a paperback and I have gone through hundreds of books in my life.  I will try to find it.  The author dismissed the idea of us running out of resources.  He figured recycling of virtually everything with cheap abundant nuclear power and the invention of new replacement products for diminishing resources would not be a problem. 
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 04/25/2019 08:10 am
I checked Wikipedia, some granite does have high concentrations of uranium and thorium.  This can create a radon problem with some granite counter tops. 

That's radioactivity hysteria, plain and simple. There is no way a kitchen can collect enough Radon to get anywhere near problematic levels.

We have some problem with Radon in some old houses basements in the german Erzgebirge area. There are uranium mines there and Radon from tunnels and cracks in the bedrock can climb into very poorely vented basements and reach potentially harmful levels there. But this is an exceptional situation in an area with uranium rich minerals.

BTW OT there is a health industry around those old tunnels with very high Radon content in the air. People go there and spend hours a day for a while in those tunnels. They claim it cures their Rheuma for years.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 04/25/2019 09:08 am
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.

Are you sure (http://adsabs.harvard.edu/abs/1981Geokh.......10B)?
I guess not. Previous sources suggested Mars was depleted in Uranium and Thorium, but if you've found evidence otherwise, I cannot say for sure.

Very, very depleted. Th concentrations in parts of the US are up 13-14 ppm, on Mars you're lucky if you get 1ppm. If you were desperate, you could mine for it. Th/U ratios are similar to Earth, at around 4:1. The dirt in your back yard has a higher concentration than Mars. Some hydrothermal processes through impact melting may have enriched a few deposits, and there may well be some placer deposits too from rivers, but they're not going to be anywhere near Earth concentrations. Earth upper continental crustal concetration of Th goes up to 10ppm. U is lithophile, and is selectively crystallised out of the Earth's crust. You also see it in lunar mare material, where a similar range of concentrations is seen. Far higher than Mars, still.

At 1ppm Th, the overall energy content of the mined rock would only be around 5x that of coal.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 04/25/2019 09:20 am
One of the best features of the kilopower design is that it's self regulating with no moving parts...

The kilopower (https://www.nasa.gov/sites/default/files/atoms/files/ns_kilopower_fs_180111.pdf) design uses highly enriched uranium, which is highly radioactive.
In the event of a launch failure, it could end up becoming a dirty bomb.
That's why I suspect it will be hard to get approval to launch any significant amounts of highly enriched uranium.

By contrast, 4th generation reactors use non-radioactive materials as fuel (depleted uranium, thorium, etc.).
For example, we have enough depleted uranium to power earth for hundreds of years at today's energy levels.
Internally, a 4th generation reactor breeds (https://en.wikipedia.org/wiki/Breeder_reactor) radioactive fission fuel from these non-radioactive sources.
To get this breeding process started, they do require a small amount of radioactive fuel, e.g. Plutonium.
But this small amount of starter material probably wouldn't be hazardous in the event of a launch failure.

Bill Gates is funding a company that's working on a traveling wave reactor (https://en.wikipedia.org/wiki/Traveling_wave_reactor) for use in African rural areas.
These reactors last 60 years without any refueling. I don't know what the smallest viable TWR is,
but I have heard they're working on other types of small, modular 4th generation reactors.

Besides the ridiculously "let them eat yellowcake" aspect of it, the idea of Bill Gates working with the Chinese to plop miniature breeder reactors near where I happen to live would genuinely scare the crap out of me.

Fortunately that sounds like internet woo which will never happen.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/25/2019 09:29 am
That's radioactivity hysteria, plain and simple...

Yes.

And unfortunately, most of the population doesn't seem to understand the relative risks of nuclear power.
Contrary to popular belief, nuclear power is actually the safest source of energy on earth.
For example, nuclear power is an order of magnitude safer than rooftop solar.

When you google "deaths per twh", many sites say basically the same thing, but this (https://www.nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html) one comes up first in my search results.
Quote
But what about Chernobyl ?
The World Health Organization study in 2005 indicated that 50 people died to that point as a direct result of Chernobyl. 4000 people may eventually die earlier as a result of Chernobyl, but those deaths would be more than 20 years after the fact and the cause and effect becomes more tenuous.

Averaging about 2100 TWh from 1985-2005 or a total of 42,000 TWh. So those 50 deaths would be 0.0012 deaths/TWh. If those possible 4000 deaths occur over the next 25 years, then with 2800 TWh being assumed average for 2005 through 2030, then it would be 4000 deaths over 112,000 TWh generated over 45 years or 0.037 deaths/TWh. There are no reactors in existence that are as unsafe as the Chernobyl reactor was. Even the eight of that type that exist have containment domes and operate with lower void co-efficients.

The safety issues with Rooftop solar installations
Those who talk about PV solar power (millions of roofs) need to consider roof worker safety. About 1000 construction fatalities per year in the US alone. 33% from working at heights...

The world total was from about 1.5 million solar roofed homes. 30% of the solar power was from roof installed units. 1/6th of the 9 million roofing job accidents would be about 50 deaths from installing 1.5 million roofs if other countries had similar to US safety. The amount of roof installations is increasing as a percentage. 4 TWh from roofs PV. So 12.5 deaths per TWh from solar roof installations. Assuming 15 years as the average functional life or time until major maintenance or upgrade is required. The average yearly deaths from rooftop solar is 0.83/TWh. Those who want a lower bound estimate can double the life of the solar panels (0.44deaths/TWh). 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/25/2019 12:19 pm
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.

Are you sure (http://adsabs.harvard.edu/abs/1981Geokh.......10B)?
I guess not. Previous sources suggested Mars was depleted in Uranium and Thorium, but if you've found evidence otherwise, I cannot say for sure.

Very, very depleted. Th concentrations in parts of the US are up 13-14 ppm, on Mars you're lucky if you get 1ppm. If you were desperate, you could mine for it. Th/U ratios are similar to Earth, at around 4:1. The dirt in your back yard has a higher concentration than Mars. Some hydrothermal processes through impact melting may have enriched a few deposits, and there may well be some placer deposits too from rivers, but they're not going to be anywhere near Earth concentrations. Earth upper continental crustal concetration of Th goes up to 10ppm. U is lithophile, and is selectively crystallised out of the Earth's crust. You also see it in lunar mare material, where a similar range of concentrations is seen. Far higher than Mars, still.

At 1ppm Th, the overall energy content of the mined rock would only be around 5x that of coal.
Have you got a reference?  I'd like to add this to my analysis, in particular if thorium or uranium require more processing, the cost of the fuel will go up.  Contrary to solar, the transportation cost of nuclear fuel is not very high, most of the costs are production costs and in the thermal cycle elements.  As energy costs are likely to be higher on Mars, the cost of mining the Uranium and Thorium might make it un economical.  In such a case we might as well go with solar and wait hopefully for fusion.  Lots of deuterium on Mars  ;-)
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 04/25/2019 01:49 pm
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.

Are you sure (http://adsabs.harvard.edu/abs/1981Geokh.......10B)?
I guess not. Previous sources suggested Mars was depleted in Uranium and Thorium, but if you've found evidence otherwise, I cannot say for sure.

Very, very depleted. Th concentrations in parts of the US are up 13-14 ppm, on Mars you're lucky if you get 1ppm. If you were desperate, you could mine for it. Th/U ratios are similar to Earth, at around 4:1. The dirt in your back yard has a higher concentration than Mars. Some hydrothermal processes through impact melting may have enriched a few deposits, and there may well be some placer deposits too from rivers, but they're not going to be anywhere near Earth concentrations. Earth upper continental crustal concetration of Th goes up to 10ppm. U is lithophile, and is selectively crystallised out of the Earth's crust. You also see it in lunar mare material, where a similar range of concentrations is seen. Far higher than Mars, still.

At 1ppm Th, the overall energy content of the mined rock would only be around 5x that of coal.
Have you got a reference?  I'd like to add this to my analysis, in particular if thorium or uranium require more processing, the cost of the fuel will go up.  Contrary to solar, the transportation cost of nuclear fuel is not very high, most of the costs are production costs and in the thermal cycle elements.  As energy costs are likely to be higher on Mars, the cost of mining the Uranium and Thorium might make it un economical.  In such a case we might as well go with solar and wait hopefully for fusion.  Lots of deuterium on Mars  ;-)

From Mars Odyssey.

(https://grs.lpl.arizona.edu/resultsimages/Th_040305_NG_5x5_SmB10_016_EQ75_with2Logos_web.jpg)

https://grs.lpl.arizona.edu/latestresults.jsp?lrid=32

There are some wildly inaccurate numbers from the Mars 5 probe as well. We might still find something like a Compton-Belkovich Thorium Anomaly on Mars, buried under the dust. May as well trade volatiles with the Moon colonies for thorium. :P

https://en.wikipedia.org/wiki/Compton%E2%80%93Belkovich_Thorium_Anomaly
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/25/2019 04:03 pm
I'm not sure why we're worried about the amount of thorium or uranium on Mars.  The amount needed to power a 4th gen reactor would be relatively small, and they're not radioactive, so there are no issues launching it from earth.

By contrast, for a reactor that uses highly enriched uranium, I think it would be hard to get approval to launch.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/25/2019 04:47 pm
I'm not sure why we're worried about the amount of thorium or uranium on Mars.  The amount needed to power a 4th gen reactor would be relatively small, and they're not radioactive, so there are no issues launching it from earth.

By contrast, for a reactor that uses highly enriched uranium, I think it would be hard to get approval to launch.
Minor point - all isotopes of both Uranium and Thorium are radioactive. That said the vast majority of Thorium is found as the 232 isotope which has a massive half life so is only very mildly radioactive.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/25/2019 04:50 pm
I'm not sure why we're worried about the amount of thorium or uranium on Mars.  The amount needed to power a 4th gen reactor would be relatively small, and they're not radioactive, so there are no issues launching it from earth.

By contrast, for a reactor that uses highly enriched uranium, I think it would be hard to get approval to launch.
It's just that it would have been nice to produce the nuclear fuel locally.  If one of the goals or a Mars settlement is total independence from Earth and self reliance, then nuclear fuel from Earth would be a flaw in the program.
Asteroids do not seem to be particularly promising either, so we might be left with processes that need to treat huge quantities of minerals for a small quantity of thorium or uranium.
If that is the case and storms are really a problem, then either very large scale energy storage, or perhaps orbital solar, might be a long term requirement.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/25/2019 05:05 pm
It’s worth pointing out that Mars is depleted in fissionable fuels like Uranium and Thorium compared to the Earth.

Are you sure (http://adsabs.harvard.edu/abs/1981Geokh.......10B)?
I guess not. Previous sources suggested Mars was depleted in Uranium and Thorium, but if you've found evidence otherwise, I cannot say for sure.

Very, very depleted. Th concentrations in parts of the US are up 13-14 ppm, on Mars you're lucky if you get 1ppm. If you were desperate, you could mine for it. Th/U ratios are similar to Earth, at around 4:1. The dirt in your back yard has a higher concentration than Mars. Some hydrothermal processes through impact melting may have enriched a few deposits, and there may well be some placer deposits too from rivers, but they're not going to be anywhere near Earth concentrations. Earth upper continental crustal concetration of Th goes up to 10ppm. U is lithophile, and is selectively crystallised out of the Earth's crust. You also see it in lunar mare material, where a similar range of concentrations is seen. Far higher than Mars, still.

At 1ppm Th, the overall energy content of the mined rock would only be around 5x that of coal.
Have you got a reference?  I'd like to add this to my analysis, in particular if thorium or uranium require more processing, the cost of the fuel will go up.  Contrary to solar, the transportation cost of nuclear fuel is not very high, most of the costs are production costs and in the thermal cycle elements.  As energy costs are likely to be higher on Mars, the cost of mining the Uranium and Thorium might make it un economical.  In such a case we might as well go with solar and wait hopefully for fusion.  Lots of deuterium on Mars  ;-)

From Mars Odyssey.

(https://grs.lpl.arizona.edu/resultsimages/Th_040305_NG_5x5_SmB10_016_EQ75_with2Logos_web.jpg)

https://grs.lpl.arizona.edu/latestresults.jsp?lrid=32

There are some wildly inaccurate numbers from the Mars 5 probe as well. We might still find something like a Compton-Belkovich Thorium Anomaly on Mars, buried under the dust. May as well trade volatiles with the Moon colonies for thorium. :P

https://en.wikipedia.org/wiki/Compton%E2%80%93Belkovich_Thorium_Anomaly
So high concentration on Mars means 1 ppm, while dirt on Earth holds 6ppm.  Ouch.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/25/2019 11:05 pm
Minor point - all isotopes of both Uranium and Thorium are radioactive. That said the vast majority of Thorium is found as the 232 isotope which has a massive half life so is only very mildly radioactive.
Everywhere on earth is mildly radioactive (see image below).

All water is mildly radioactive due to trace amounts of certain hydrogen isotopes.

Uranium-238 (a.k.a. depleted Uranium) is not dangerous. As long as you don't eat the stuff, it's perfectly safe.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 04/26/2019 12:47 pm
In Guarapari, Brazil, the thorium-rich beach gives you a nice dice of 0.04mSv per hour, or 1.5x the dose standing on the surface of Mars.

Of course, if you happen to live in Ramsar, Iran, on top of radioactive hot springs with houses built from radioactive local resources, you enjoy about 1/2 the annual dose of living out in the open on Mars.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 04/26/2019 01:26 pm
It's just that it would have been nice to produce the nuclear fuel locally.  If one of the goals or a Mars settlement is total independence from Earth and self reliance, then nuclear fuel from Earth would be a flaw in the program.

Theoretically, yes. Practically, maybe not.

4th generation nuclear reactors use fuel that's safe to launch from earth, and they use it 100 times more efficiently, so the fuel lasts a lot longer, and there's much less waste.

For example, traveling wave reactors are never refueled.  The fuel that's installed at the time of manufacture will supply power for 40-60 years (https://en.wikipedia.org/wiki/TerraPower#Traveling_wave_reactor). So the containment vessel is sealed and never opened. This means the reactor itself can be used as a  storage container at the end of it's life.

Again, I'm not sure if a traveling wave reactor is the right type for Mars, but it's an example of how long a 4th generation reactor can run on a relatively small amount of fuel. There's sort of a renaissance in fission reactor design right now, and this could change the equation for nuclear power on Mars.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 04/26/2019 03:58 pm
Minor point - all isotopes of both Uranium and Thorium are radioactive. That said the vast majority of Thorium is found as the 232 isotope which has a massive half life so is only very mildly radioactive.
Everywhere on earth is mildly radioactive (see image below).

All water is mildly radioactive due to trace amounts of certain hydrogen isotopes.

Uranium-238 (a.k.a. depleted Uranium) is not dangerous. As long as you don't eat the stuff, it's perfectly safe.
Very true. A bit like Arsenic, its not dangerous as long as you don't eat it.
Title: Re: Power options for a Mars settlement
Post by: Thrustpuzzle on 05/22/2019 10:02 pm
A simple but very interesting Martian power requirements simulator (https://davedx.github.io/mars-power/), giving an idea of the balance of PV and/or kilopower reactors  and batteries needed for supporting humans and/or manufacturing CH4.

Fun to play with! It does not simulate dust storm effects on PV, but you can manually do so by reducing the PV count for the same effect.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/22/2019 10:30 pm
It does simulate dust storms. It doesn’t simulate degradation, I don’t think, but that’s a small effect and impacts kilopower as well to some extent.

If you right-click parts of the page in Chrome and select “inspect”, you can change the values to more than are listed in the drop-downs. Very useful. Can simulate how to provide for a crew of 40 with 100 tons of methane for Starship’s return.

I do wish the batteries started fully charged, as that’d be more realistic.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/23/2019 09:39 pm

Very, very depleted. Th concentrations in parts of the US are up 13-14 ppm, on Mars you're lucky if you get 1ppm. If you were desperate, you could mine for it. Th/U ratios are similar to Earth, at around 4:1. The dirt in your back yard has a higher concentration than Mars. Some hydrothermal processes through impact melting may have enriched a few deposits, and there may well be some placer deposits too from rivers, but they're not going to be anywhere near Earth concentrations. Earth upper continental crustal concetration of Th goes up to 10ppm. U is lithophile, and is selectively crystallised out of the Earth's crust. You also see it in lunar mare material, where a similar range of concentrations is seen. Far higher than Mars, still.

At 1ppm Th, the overall energy content of the mined rock would only be around 5x that of coal.
Indeed, on that basis on Earth it does not sound very competitive with coal.

But Mars has no coal deposits.  :(

Otherwise it's a minimum of 1 MW of solar running for a whole synod to generate the propellant for one SS to go home.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/24/2019 12:28 am

Very, very depleted. Th concentrations in parts of the US are up 13-14 ppm, on Mars you're lucky if you get 1ppm. If you were desperate, you could mine for it. Th/U ratios are similar to Earth, at around 4:1. The dirt in your back yard has a higher concentration than Mars. Some hydrothermal processes through impact melting may have enriched a few deposits, and there may well be some placer deposits too from rivers, but they're not going to be anywhere near Earth concentrations. Earth upper continental crustal concetration of Th goes up to 10ppm. U is lithophile, and is selectively crystallised out of the Earth's crust. You also see it in lunar mare material, where a similar range of concentrations is seen. Far higher than Mars, still.

At 1ppm Th, the overall energy content of the mined rock would only be around 5x that of coal.
Indeed, on that basis on Earth it does not sound very competitive with coal.

But Mars has no coal deposits.  :(

Otherwise it's a minimum of 1 MW of solar running for a whole synod to generate the propellant for one SS to go home.
1MW isn't too bad. 1MW average of solar would weigh much less than 1MW of kilopower.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/25/2019 01:29 pm

Very, very depleted. Th concentrations in parts of the US are up 13-14 ppm, on Mars you're lucky if you get 1ppm. If you were desperate, you could mine for it. Th/U ratios are similar to Earth, at around 4:1. The dirt in your back yard has a higher concentration than Mars. Some hydrothermal processes through impact melting may have enriched a few deposits, and there may well be some placer deposits too from rivers, but they're not going to be anywhere near Earth concentrations. Earth upper continental crustal concetration of Th goes up to 10ppm. U is lithophile, and is selectively crystallised out of the Earth's crust. You also see it in lunar mare material, where a similar range of concentrations is seen. Far higher than Mars, still.

At 1ppm Th, the overall energy content of the mined rock would only be around 5x that of coal.
Indeed, on that basis on Earth it does not sound very competitive with coal.

But Mars has no coal deposits.  :(

Otherwise it's a minimum of 1 MW of solar running for a whole synod to generate the propellant for one SS to go home.
1MW isn't too bad. 1MW average of solar would weigh much less than 1MW of kilopower.
True but that's a) For each SS you're planning to send back and b)That's baseline withou dust storms.

Basically without generator diversity you're betting your life on enough sun shining long enough to run the propellant plant. If you have some diversity, nuclear or geothermal seem to be the obvious candidates, you open up options.

Given we now have reasonable weather records for Mars why not choose a landing site and see if it can last a synod with no dust storms covering it.

If it does then landing there without a non-solar option would seem a reasonable risk. If no such site exists then it's not a case of if a sand storm hits but how long before it does and how long will it last.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/25/2019 01:49 pm
The simulator includes dust storms.
Title: Grid
Post by: LMT on 05/26/2019 03:39 pm
Grid


(http://tve-static-syfy.nbcuni.com/prod/image/707/523/180308_3681036_The_Expanse_Season_3_Official_Trailer_1500x844_1181861955562.jpg)


A challenge:  10/50 power

There are many ways to frame the challenge of global Mars power.  Just to try one framing:

Challenge:  Coordinate plausible methods to generate martian power and transmit it worldwide.  Configure deployment to support transmission of continuous power exceeding 10 MW in all seasons and weather, day and night, to sites below 50° latitude.

A first-pass approach, with Mars Lift

The suggested Mars Lift (http://www.lakematthew.com/press/press-release-november-7-2017/) might be used first not as an off-equator cargo transporter, but as an efficient cable deployment system.  A Mars Lift could attempt the challenge, connecting power equipment in a global flexible power distribution network:  a grid.
 
One analogy


https://www.youtube.com/watch?v=cDfKJXPYYQY 


Background

1.  Safe Deployment of Mars Lift (https://forum.nasaspaceflight.com/index.php?topic=37667.msg1947612#msg1947612)

2.  Mars Lift - From Equator to Glacier (https://forum.nasaspaceflight.com/index.php?topic=37667.msg1947706#msg1947706)

3.  A Conceptual Hybrid Power Harvester (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1866798#msg1866798)

4.  Quantifying Wind Power Harvest (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1867784#msg1867784)

Methods and considerations

Power generation:  The equator gets maximum sunlight, so grid farms are on the equator.  This is also the easiest latitude for Mars Lift operation.

Power transmission:  Farms might connect through monopolar, ultra high voltage direct current (UHVDC) power cables.  UHV (800+ kV) cuts cable heating and mass; it’s required for the grid.  Monopolar / single-wire earth return (SWER (https://www.esdnews.com.au/swer-still-going-strong/)) DC cuts cable mass and simplifies power distribution from DC farms.

Range:   UHVDC power is transmitted commercially on Earth beyond 3300 km, with total loss ~ 3% per 1000 km.  Performance improves under Mars night temperatures, where resistivity drops; with corresponding cut in required cable mass.  Also, martian power transmission losses are acceptably higher than terrestrial losses, as martian power is generated not from expensive fuels but from free electron sources.  Farm scale is simply increased to compensate.  Targeted range:  a useful transmission range of 8000 km might be a fair target.  If it’s attained, the grid can be configured to meet the 10/50 challenge:  10+ MW to 50° latitude, anytime.   (High-latitude transmission would also be possible, just with greater effort and loss.  However, crewed high-latitude sites are not commonly envisioned.)


(http://www.lakematthew.com/wp-content/uploads/2019/05/Midwinter_Night_Phlegra_Montes_Equidistant_Conic_Projection.png)

 
Fig. 1:  Night range illustration.  Phlegra Montes (center) midwinter midnight.  Shade coverage, equidistant projection.  Equatorial 10° longitude marks are 583 km apart.

Insulation:  The highly-conductive atmosphere produces arcing on uninsulated high-voltage lines, so insulation is needed.  Insulated cable can be deployed on the ground, without pylons; a very great convenience.  The insulator must be lightweight; options tbd.

Conductor:  Minimum useful conductor diameter depends on uncertain factors, but is conceivably < 1.5 cm.  Metal is too massive, but carbon is being introduced as lightweight graphite and carbon nanotubes (CNTs).  One example:  high-ampacity graphene/copper nanocomposite wire of Zhao et al. 2019.  Other advances are noted in the review of Zhang et al. 2019, which targets all-carbon power transmission:

Quote
"Although CNT/metal composites may possess copper-like electrical conductivities and even higher current carrying capacities, nonmetal conductors are still preferred for next generation electronics and power transmission, especially for deep space exploration. All-carbon-based conductors, such as CNT/C composite fibers, are expected to become competitive candidates in the near future."

For those authors “near future” is a “> 10 year” timeframe.  Thus carbon power cables might emerge only in the 2030s; coincidentally the notional Mars Lift timeframe.

That timing is not entirely coincidental.  Methods giving exceptional CNT bundle conductivity and ampacity, such as stretching and cross-linking (Zhang Table 4), can also increase strength of CNTs, as in Bai et al. 2018 and Filleter et al. 2011.  Therefore, there’s some reason to think that Mars Lift CNT cables might appear near the advent of strong all-carbon power transmission cables.  Enough reason for casual post, anyway.

Grid deployment


(http://www.lakematthew.com/wp-content/uploads/2019/05/Grid_Farms.png)

 
Fig. 2:  Cartoon of an initial grid configuration.  Grid farms (equatorial white squares) are connected by UHVDC power transmission line.  Crewed facilities at Phlegra Montes glacier and Gale Crater (white circles) connect to the grid. 

Pilot:  Sometimes a space elevator guide or pilot device is conceived as hanging from the descending tether tip, adjusting tether position for capture at a base station; essentially acting as a suspended spacecraft.  This “pilot” adjusts latitude and longitude with small chemical rockets or cold gas maneuvering jets.  It may have a powered reel, or climber / spool system, to play tether in and out, for control of tip altitude.

Pilot modification:  Here the pilot is modified for cable deployment.  Cable tech suggests many options.  Picking two:

1.  Independent pilot and cable positioning:  To increase mobility, the pilot’s climber gear can be shifted from tether to power cable.  Two “buffering” cable storage spool devices are placed below that climber, and a second climber is placed below the lower spool.  In operation, the first climber gear would ride cable above, to adjust pilot altitude, and the second climber gear would ride cable below, to adjust cable drop speed on the ground.  This gives independent control of pilot altitude and cable drop speed.

2.  Fixed cable mounts:  Where cable hangs across gorges, cumulative wind force may slide the cable over rock, fraying it.  The risk might be addressed by deploying fixed mounts at suspension points.  A drill system opens rock for insertion of a set of mounting “clips”.  Clips would secure the cable to a suspension point, tensioning suspension and preventing slide.

Survey:  A survey would precede deployment.  Airborne drones acquire close-range data to map out the safest path.  Where clips are needed the Mars Lift maneuvers to each location, and the pilot operator installs clips telerobotically, or else crews fly in to install them by hand.

After survey, deployment.  Where the cable crosses a clip, it’s laid into the open track and a clamp closes to secure the cable.

Deployment speed:  As with deployment of the off-equator Mars Lift (https://forum.nasaspaceflight.com/index.php?topic=37667.msg1947612#msg1947612), cable deployment speed is dictated by Phobos:  Phobos must not intercept the tether.  One scenario:  deployment of a grid segment from Apollinaris farm (Fig. 2, far right square):

1.  Mars Lift lowers tether and pilot past Phobos to equator, ~ 170° E, Apollinaris farm.  Notional descent speed below Phobos is 200 km/hr.  At Apollinaris farm the pilot attaches to a prepositioned pair of anchored power cable spool systems, ~ 1800 km total length.   

2.  The Arestation propels the Mars Lift eastward slowly as it lifts the pilot to cable-deployment altitude. 

3.  The pilot deploys cable along the equator at 35 km/hr average speed:   faster on open plains, slower on rough terrain.  Deployment crosses 30° of longitude (1775 km). 

4.  At end of deployment, the Mars Lift lowers the pilot to Nicholson farm (Fig. 2, far left square).  The pilot detaches the spools and the cable is anchored at the farm. 

5.  Mars Lift raises the unloaded tether and pilot past Phobos at 200 km/hr.

Phobos safety in this scenario: 

- Total deployment time below Phobos:  ~ 5 Earth days. 

- Closest Phobos approach:  With optimal timing of the deployment start, Phobos’ closest approach to the tether is ~ 60 km, arguably a safe distance. 

Repetition:  Deployment is repeated 12 times to circle the equator.  Further repetition gives additional wraps, for redundant cabling or greater grid capacity.
   
Repurposing for Mars Lift, with roadway:  After grid deployment the Mars Lift can transition into its long-term role as areostationary off-equator cargo transport system: e.g., a Phlegra Montes glacier Mars Lift.  As sketched previously (https://forum.nasaspaceflight.com/index.php?topic=37667.msg1947706#msg1947706), a primitive graded roadway would ease transport of the tether to this off-equator base station.  That roadway could serve also as path for UHVDC cable, which connects Phlegra Montes to the grid at Apollinaris farm.  This cable could be transported to Phlegra Montes as Starship cargo, part of the facility's power distribution payload.  The cable is simply deployed from truck at roadside.

Thereafter, if a major repair or upgrade of the grid were needed, the Mars Lift could revert temporarily to its cable-deployment role.  Weighted transport would drive the tether and pilot back to the equator.  The Arestation would draw in slack and then lift the tether and pilot past Phobos.  When the pilot clears Phobos, the Arestation propels the Mars Lift toward the longitude of prepositioned spools.  As before, Phobos dictates timing.

Impediments:  Equatorial traverse is infeasible in some regions.  Severe impediments are present, as in Fig. 3.   Any alternate grid deployment solution would need to manage the equatorial impediments at least as well as Mars Lift, or else shift the grid far from the equator, or else abandon impassable regions.


(http://www.lakematthew.com/wp-content/uploads/2019/05/Equator.png)

 
Fig. 3.  Some severe impediments to ground transport along the martian equator.  E.g., Pavonis Mons (left), Shalbatana Vallis (right).

Result:  Tackling the challenge 

How might such a grid tackle the post’s challenge?  One scenario:  a Phlegra Montes midwinter night:


(http://www.lakematthew.com/wp-content/uploads/2019/05/Grid_At_Night.png)

 
Fig. 4:  Cartoon of a grid scenario, showing grid farms (squares) in range of Phlegra Montes (upper center circle) on a midwinter night. 

Here the farms can be assumed hybrid:  PV augmented with minor atmospheric and wind triboelectric power, after the notional hybrid configuration (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1866798#msg1866798) and first-pass production estimate (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1867784#msg1867784).  In this scenario the grid powers Phlegra Montes through a sequence of worsening conditions:

1.  In midwinter at local midnight, the Phlegra Montes base is powered by the only sunlit farm within the targeted range:  Pavonis farm (Fig. 4, far right, white square).  10 MW requirement is readily met by the PV output of a Starship’s single-payload farm, which could exceed 50 MW in early morning.

2.  A regional storm centers on Pavonis, blotting out the sun and taking that farm’s PV offline.  However, the storm’s atmospheric disturbance generates minor atmospheric and wind triboelectric power at Pavonis, with combined output plausibly exceeding 10 MW.

3.  Storm winds calm, but dust does not clear.  Pavonis is now entirely offline.  Phlegra Montes must turn to other farms for power.  The other six farms in range are all in nighttime darkness.  However, calm equatorial air typically covers less than half the night (Fig. 5).  Therefore at least three of these farms can generate nighttime wind triboelectric power for Phlegra Montes, production altogether exceeding 10 MW.

4.  In this scenario triboelectric power (or, in a real pinch, on-site battery / nuclear power) would be required for up to 2.1 hours (the farm separation interval).  Then the next farm, Olympus, comes online at sunrise and begins transmission of PV power to Phlegra Montes.


(http://www.lakematthew.com/wp-content/uploads/2019/05/GCM_Winds_And_Temp.png)


Fig. 5.  Screen from Mars atmospheric Global Circulation Model (GCM) movie (https://www.giss.nasa.gov/research/briefs/1999_allison_x1/).  Atmospheric calm extends across only a small fraction of the equator; wind triboelectricity may be harvested elsewhere.  Notably, 10 m PV pylons encounter characteristic winds faster than surface winds, at ~ 20 m/s (72 km/hr).

Refs.

Bai, Y., Zhang, R., Ye, X., Zhu, Z., Xie, H., Shen, B., ... & Zhang, S. (2018). Carbon nanotube bundles with tensile strength over 80 GPa. (https://www.researchgate.net/profile/Fei_Wei4/publication/325128963_Carbon_nanotube_bundles_with_tensile_strength_over_80_GPa/links/5b12a8ac0f7e9b4981040cae/Carbon-nanotube-bundles-with-tensile-strength-over-80-GPa.pdf) Nature nanotechnology, 13(7), 589.

Filleter, T., Bernal, R., Li, S., & Espinosa, H. D. (2011). Ultrahigh strength and stiffness in cross‐linked hierarchical carbon nanotube bundles. (http://clifton.mech.northwestern.edu/~espinosa/publications/papers/Ultrahigh Strength and Stiffness in Cross-Linked Hierarchical Carbon Nanotube Bundles.pdf) Advanced Materials, 23(25), 2855-2860.

Zhang, S., Nguyen, N., Leonhardt, B., Jolowsky, C., Hao, A., Park, J. G., & Liang, R. (2019). Carbon‐Nanotube‐Based Electrical Conductors: Fabrication, Optimization, and Applications. (https://www.researchgate.net/profile/Songlin_Zhang6/publication/332244491_Carbon-Nanotube-Based_Electrical_Conductors_Fabrication_Optimization_and_Applications/links/5cae5c1ca6fdcc1d498c0906/Carbon-Nanotube-Based-Electrical-Conductors-Fabrication-Optimization-and-Applications.pdf) Advanced Electronic Materials, 1800811.

Zhao, K., Zhang, T., Ren, A., Yang, Y., Xiao, P., Ge, Z., ... & Chen, Y. (2019). High ampacity of superhelix graphene/copper nanocomposite wires by a synergistic growth-twisting-drawing strategy. (https://www.sciencedirect.com/science/article/pii/S000862231830856X) Carbon, 141, 198-208.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/26/2019 04:21 pm
I like this post, but can we move it to its own thread or the Mars section?
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 05/29/2019 07:57 pm
So the idea of orbiting solar power for mars is that it could provide continuous power for a mars base. (not in dust storm though).
What are the trades for solar panels in space and microwave transmission versus solar panels on surface and a big silver coated plastic sheet to reflect sunlight down to the panels at night for continuous power.

Something like a ring with plastic sheet between the ring. Ring could be an inflated tube maybe. Probably geo synchronous.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 05/29/2019 09:48 pm
So the idea of orbiting solar power for mars is that it could provide continuous power for a mars base. (not in dust storm though).
What are the trades for solar panels in space and microwave transmission versus solar panels on surface and a big silver coated plastic sheet to reflect sunlight down to the panels at night for continuous power.

Something like a ring with plastic sheet between the ring. Ring could be an inflated tube maybe. Probably geo synchronous.

In some ways the situation with orbital solar power on Mars is the reverse of orbital solar power on Earth. With Earth the big drawback with orbital solar is the cost of getting panels into orbit. With Mars the panels effectively (for the purpose of comparing space based and ground based power stations) start in Mars orbit so the cost is in taking them down to the surface.

I wonder if it would be possible to select a frequency for the power transmission that was not blocked or not blocked too badly by dust storms?

I don’t think that the orbital reflector would be at all practical or economic. I doubt it would appear as much more than a very bright star. Think of it this way, reflective materials that weighed as much as a solar panel would have to be capable of generating (very roughly) half a panels worth of electricity in reflected light.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/30/2019 04:57 pm
I don’t think that the orbital reflector would be at all practical or economic.

Likewise areostationary space solar power.  Cougnet et al. 2004 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508) laid out some brutal numbers.
Title: Re: Power options for a Mars settlement
Post by: Zed_Noir on 05/30/2019 11:32 pm
I don’t think that the orbital reflector would be at all practical or economic.

Likewise areostationary space solar power.  Cougnet et al. 2004 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508) laid out some brutal numbers.

@Mongo62 disagree with your conclusions.
Quote

I looked at the referenced report.

It provides several options using RF and laser power transmission. You selected the lowest-efficiency option, with an RF transmission antenna that is much too small to provide an adequately narrow beam. The receiving antenna only covers a small fraction of the beam area. Total system power efficiency is 0.51% in the option you chose. Also the actual SPS mass is 41t, with most of the other 459t apparently being the vehicle to get it into Mars orbit.

This paper was published in 2004, and I am sure that efficiencies would be substantially greater if the SPS system were to be designed today.
https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868093#msg1868093 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868093#msg1868093)
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/31/2019 01:03 am
I don’t think that the orbital reflector would be at all practical or economic.

Likewise areostationary space solar power.  Cougnet et al. 2004 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508) laid out some brutal numbers.

@Mongo62 disagree with your conclusions.
Quote

I looked at the referenced report.

It provides several options using RF and laser power transmission. You selected the lowest-efficiency option, with an RF transmission antenna that is much too small to provide an adequately narrow beam. The receiving antenna only covers a small fraction of the beam area. Total system power efficiency is 0.51% in the option you chose. Also the actual SPS mass is 41t, with most of the other 459t apparently being the vehicle to get it into Mars orbit.

This paper was published in 2004, and I am sure that efficiencies would be substantially greater if the SPS system were to be designed today.
https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868093#msg1868093 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868093#msg1868093)

Well, Zed_Noir, what's your judgment?

The info is there, so don't just pass notes, but evaluate.

The subject matter of this forum is good mental exercise, don't you think?
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 05/31/2019 01:11 am
I don’t think that the orbital reflector would be at all practical or economic.

Likewise areostationary space solar power.  Cougnet et al. 2004 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508) laid out some brutal numbers.
Thanks for that

Well it would seem that I was correct in my analysis as far as it went, but those modist advantages are dwarfed by the hopeless power transmission efficiency which is ridiculously low and means the whole thing is a non-starter as far as I can tell.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 05/31/2019 11:15 am
I don’t think that the orbital reflector would be at all practical or economic.

Likewise areostationary space solar power.  Cougnet et al. 2004 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508) laid out some brutal numbers.
Thanks for that

Well it would seem that I was correct in my analysis as far as it went, but those modist advantages are dwarfed by the hopeless power transmission efficiency which is ridiculously low and means the whole thing is a non-starter as far as I can tell.

As to my giant mirror proposal.
13000km for geostationary on mars
.3 degrees for sun angular at mars
13000*tan(.3)=68km
So a silvered solar sail 68km in diameter which must be kept very flat. Might not weigh much. Probably orbital forces will distort it too much. 100% transmission efficiency.

I think the biggest reason to have solar in orbit is too extend the power delivery into the night and thereby provide power 24/7.
Could also enhance power during the day by making it brighter than mars average by having extra solar.

EDIT: changed angular diameter of sun from .5 at earth to about .3 at mars.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 06/01/2019 05:55 am
13000km for geostationary on mars

13?
Title: Re: Power options for a Mars settlement
Post by: Keldor on 06/02/2019 03:34 am
I don’t think that the orbital reflector would be at all practical or economic.

Likewise areostationary space solar power.  Cougnet et al. 2004 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508) laid out some brutal numbers.
Thanks for that

Well it would seem that I was correct in my analysis as far as it went, but those modist advantages are dwarfed by the hopeless power transmission efficiency which is ridiculously low and means the whole thing is a non-starter as far as I can tell.

As to my giant mirror proposal.
13000km for geostationary on mars
.3 degrees for sun angular at mars
13000*tan(.3)=68km
So a silvered solar sail 68km in diameter which must be kept very flat. Might not weigh much. Probably orbital forces will distort it too much. 100% transmission efficiency.

I think the biggest reason to have solar in orbit is too extend the power delivery into the night and thereby provide power 24/7.
Could also enhance power during the day by making it brighter than mars average by having extra solar.

EDIT: changed angular diameter of sun from .5 at earth to about .3 at mars.

68km diameter and the lightest practical solar sail material I could find on Wikipedia (3 grams per meter^2) gives a mass of 10,000 tons.  This is before considering any sort of structure to keep it's shape whatsoever.

Even if you can somehow keep it the right shape, how do you handle stationkeeping?  A solar sail that size at Mars is big enough to produce ~ 1 ton force.  How do you counteract this in order to keep the mirror from flying out into space or crashing down into Mars?  As best as I can tell, the trend, if left uncorrected, will be to increase the eccentricity of the orbit until it crashes into Mars.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 06/02/2019 12:59 pm
I don’t think that the orbital reflector would be at all practical or economic.

Likewise areostationary space solar power.  Cougnet et al. 2004 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508) laid out some brutal numbers.
Thanks for that

Well it would seem that I was correct in my analysis as far as it went, but those modist advantages are dwarfed by the hopeless power transmission efficiency which is ridiculously low and means the whole thing is a non-starter as far as I can tell.

As to my giant mirror proposal.
13000km for geostationary on mars
.3 degrees for sun angular at mars
13000*tan(.3)=68km
So a silvered solar sail 68km in diameter which must be kept very flat. Might not weigh much. Probably orbital forces will distort it too much. 100% transmission efficiency.

I think the biggest reason to have solar in orbit is too extend the power delivery into the night and thereby provide power 24/7.
Could also enhance power during the day by making it brighter than mars average by having extra solar.

EDIT: changed angular diameter of sun from .5 at earth to about .3 at mars.

68km diameter and the lightest practical solar sail material I could find on Wikipedia (3 grams per meter^2) gives a mass of 10,000 tons.  This is before considering any sort of structure to keep it's shape whatsoever.

Even if you can somehow keep it the right shape, how do you handle stationkeeping?  A solar sail that size at Mars is big enough to produce ~ 1 ton force.  How do you counteract this in order to keep the mirror from flying out into space or crashing down into Mars?  As best as I can tell, the trend, if left uncorrected, will be to increase the eccentricity of the orbit until it crashes into Mars.
Polar orbit, reflecting on the terminator, so that  the force of the light pushes in a mostly normal/antinormal direction (toward the nightside), where martian gravity can compensate.
Title: Re: Power options for a Mars settlement
Post by: LMT on 06/06/2019 03:19 pm
Quantum Dot PV Update

OP:  record-setting (2017) experimental QD PV solar cell rated at 15.2 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848)

Mar. 19 2019:  commercial plant (http://www.qmcdots.com/press/press.php) under construction, for production of QD PV solar cells and other QD devices.  Quantum Materials Corp / Amtronics CC.

Quantum Materials:  QD PV solution statement (http://www.qmcdots.com/products/products-solar.php)

Solterra subsidiary:  statement on QD PV automated flexographic printing (http://www.solterrasolarcells.com/innovation/flexographicprinting.php) 

Related:

Like the 2017 record-holder, a 2019 record-setting solar cell also leverages PEN substrate and Ag nanowire electrodes.  The active layer in this new record-holder is perovskite.  Rating:  29.4 kW/kg (https://pubs.rsc.org/en/content/articlelanding/2018/ta/c8ta10585e/unauth#!divAbstract)

(https://pubs.rsc.org/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=C8TA10585E)

Caveat:  Perovskite solar cell stability problems were noted in thread previously (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1850500#msg1850500).

PV farm deployment concept, applicable to a base or a grid farm (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437):

Unroll flat with Renovagen Rapid Roll "i" (http://www.renovagen.com/products/rapid-roll-i/)-class mechanism.

Lift, angle and tension on 10-meter pylon wires.

DC distribution hw and other hw (e.g., triboelectricity rectifier/inverter (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850762#msg1850762)) would be incorporated into the deployment container.

Quote
"The integration of the Rapid Roll technology into a side-opening ISO shipping container, combined with inverters and a larger battery bank, creates an easily transportable self-sufficient solar power system capable of generating 10 times more power than competitive products. Deploying a huge solar array measuring 5 metres (20ft ISO) or 10 metres (40ft ISO) in width and up to 200 metres in length, this represents by far the largest containerised deployable solar array yet conceived. At this scale a multi-MW solar power plant could be deployed in a matter of hours – city-scale power sufficient for a large mining site or military main operating base."


(http://www.renovagen.com/wp-content/uploads/2016/09/rapid-roll-i-1-1024x1024.jpg)


(http://www.renovagen.com/wp-content/uploads/2016/09/rapid-roll-i-2.jpg)


(https://inhabitat.com/wp-content/blogs.dir/1/files/2010/04/FTL-Solar-Fabric-5.jpg)


https://www.youtube.com/watch?v=3YuSZvaP-9U
Title: Re: Power options for a Mars settlement
Post by: Dave G on 06/06/2019 05:16 pm
PV farm deployment concept, applicable to a base or a grid farm (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437):

Unroll flat with Renovagen Rapid Roll "i" (http://www.renovagen.com/products/rapid-roll-i/)-class mechanism.

Lift, angle and tension on 10-meter pylon wires.

DC distribution hw and other hw (e.g., triboelectricity rectifier/inverter (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850762#msg1850762)) would be incorporated into the deployment container.

I suspect crew members will set up the solar array. 

Remember, the plan says propellant production won't start until after crew members arrive on the surface.

The initial cargo missions just get everything in place, i.e. get the components on the Mars surface.
Title: Re: Power options for a Mars settlement
Post by: Lar on 06/06/2019 09:47 pm
PV farm deployment concept, applicable to a base or a grid farm (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437):

Unroll flat with Renovagen Rapid Roll "i" (http://www.renovagen.com/products/rapid-roll-i/)-class mechanism.

Lift, angle and tension on 10-meter pylon wires.

DC distribution hw and other hw (e.g., triboelectricity rectifier/inverter (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850762#msg1850762)) would be incorporated into the deployment container.

I suspect crew members will set up the solar array. 

Remember, the plan says propellant production won't start until after crew members arrive on the surface.

The initial cargo missions just get everything in place, i.e. get the components on the Mars surface.
I think there is a bit of wiggle around what "place" means in this context. To me it means at least getting it out of the ship but maybe not. ANY movement at all will require something, whether it be a mechanism or a bot, to do the moving.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 06/07/2019 12:29 am
It may be a bit out there, but with the first Mars cargo mission being delayed to 2024, Helion Energy's reactor could be ready just in time for the next synode after that. Their website now says that their prototypes have demonstrated that they can make it work. They now aim (!) to have a first commercial power plant ready in 6 years. Of course things get delayed and all that. That is life. But with a little bit of luck and maybe some extra funding from SpaceX, there could be a solid chance of that happening.
The advantage of the Helion Fusion Engine is that it uses direct conversion and only deuterium fuel (it breeds it's own Helium3).  The direct conversion means that it won't need a steam cycle and thus no (or relatively little) cooling panels.
Title: Re: Power options for a Mars settlement
Post by: Lar on 06/07/2019 03:12 am
It may be a bit out there, but with the first Mars cargo mission being delayed to 2024, Helion Energy's reactor could be ready just in time for the next synode after that. Their website now says that their prototypes have demonstrated that they can make it work. They now aim (!) to have a first commercial power plant ready in 6 years. Of course things get delayed and all that. That is life. But with a little bit of luck and maybe some extra funding from SpaceX, there could be a solid chance of that happening.
The advantage of the Helion Fusion Engine is that it uses direct conversion and only deuterium fuel (it breeds it's own Helium3).  The direct conversion means that it won't need a steam cycle and thus no (or relatively little) cooling panels.
While it's true that if there is a fusion breakthrough it changes a lot of things, that doesn't mean every thread that has anything to do with power has to discuss the latest fusion proposal. "Stick to TRL 7" or better seems prudent to me.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/07/2019 03:54 am
I think there is a bit of wiggle around what "place" means in this context. To me it means at least getting it out of the ship but maybe not. ANY movement at all will require something, whether it be a mechanism or a bot, to do the moving.

They will have to deploy at least some array. There are the mining droids that need powering and the ships need some power as well.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 06/07/2019 10:22 am
I think there is a bit of wiggle around what "place" means in this context. To me it means at least getting it out of the ship but maybe not.
I agree the wording is subject to interpretation, but if SpaceX is planning to fully set up the solar array, it seems to me like the slide would have said that directly, like it does for "Set up propellant production plant".

ANY movement at all will require something, whether it be a mechanism or a bot, to do the moving.
The cargo ships will carry batteries for the solar array. Lots of batteries. Starship's fan-folded solar array can keep these topped up in-transit. That may be enough for powering smaller bots to explore the area.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 06/07/2019 10:39 am
They will have to deploy at least some array. There are the mining droids that need powering and the ships need some power as well.

I agree that mining droids will be required for propellant production. Paul Wooster's presentation made this clear.

However, I suspect these larger mining droids won't be used for the initial unmanned phase of the mission, before propellant production starts.  They could get by with something much smaller to initially explore the area.

But as usual, this is all subject to interpretation. Your mileage may vary.
Title: Re: Power options for a Mars settlement
Post by: oiorionsbelt on 06/07/2019 03:29 pm

I suspect crew members will set up the solar array. 

Remember, the plan says propellant production won't start until after crew members arrive on the surface.

The initial cargo missions just get everything in place, i.e. get the components on the Mars surface.
I think there is a bit of wiggle around what "place" means in this context. To me it means at least getting it out of the ship but maybe not. ANY movement at all will require something, whether it be a mechanism or a bot, to do the moving.
Initial solar arrays may well be deployed by compressed air.
https://www.youtube.com/watch?v=_J4RxDZJ6Vg
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 06/07/2019 05:10 pm

I suspect crew members will set up the solar array. 

Remember, the plan says propellant production won't start until after crew members arrive on the surface.

The initial cargo missions just get everything in place, i.e. get the components on the Mars surface.
I think there is a bit of wiggle around what "place" means in this context. To me it means at least getting it out of the ship but maybe not. ANY movement at all will require something, whether it be a mechanism or a bot, to do the moving.
Initial solar arrays may well be deployed by compressed air.
https://www.youtube.com/watch?v=_J4RxDZJ6Vg
Personally, I'm partial to gravity-deployed  rolled cells tossed out of the Starship's hatches and hung on it's side like medieval banners.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/07/2019 05:56 pm
I like cell rolls lowered from aft cargo holds and rolled out to great distances. Big radial deploy pattern.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 06/07/2019 06:44 pm
I like cell rolls lowered from aft cargo holds and rolled out to great distances. Big radial deploy pattern.

I would think you could get some pretty simply deploy bots if that's all they had to do. Two wheels, big roll of panels between them, dropped out of the cargo holds, drive forward in any rough direction, essentially being steered by the unrolling film behind them, until they reach the end of the roll. Then stop. Bam! Done.

Now imagine I had photoshop skills and could put these together...

(https://www-robotics.jpl.nasa.gov/roboticImages/img811-413-browse.jpg) (https://www-robotics.jpl.nasa.gov/roboticImages/img811-413-browse.jpg)

(http://www.climatevisuals.org/sites/default/files/styles/clvi_photo_large/public/images/2018-04/h_01037891_0.jpg?itok=T3dZ_XiV) (http://www.climatevisuals.org/sites/default/files/styles/clvi_photo_large/public/images/2018-04/h_01037891_0.jpg?itok=T3dZ_XiV)

(https://www.blouinnews.com/sites/default/files/styles/640x432/public/images/story/2017_10_06/aerial-feb-2016-637x320-637x200_0.jpg?itok=E3sPqmDV) (https://www.blouinnews.com/sites/default/files/styles/640x432/public/images/story/2017_10_06/aerial-feb-2016-637x320-637x200_0.jpg?itok=E3sPqmDV)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/07/2019 07:50 pm
For the inflatable "party favor" PV, two air tubes on opposite sides should give rudimentary steering by adjusting the inflation speed between sides. It also gives a redundant option in case one tube is punctured during deployment, at the cost of some curvature. This could eliminate the deployment bot altogether, or relegate it to a redundant backup.

A wild variation on this idea would be to stretch a transparent protective film between the tubes, and use puffs of compressed atmosphere to cause a "wave" that shakes off dust.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/11/2019 09:53 pm
Yes, my premise was that the colonists are paying for this. If not them, then who?

Well if I were in Musk's position, I would be working toward capturing MASSIVE revenue streams using synergistic technologies such that I can essentially provide them subsidized to the colonization effort.  He's already showing that's exactly what he intends with Solar City, CommX, The Boring Company, and even Tesla,.  All of these are synergistic.  I can imagine at least two other major revenue producing businesses.  Remember, he wants to go.  He can't do all the lifting himself.  He'd be little different than captains that transported people to the new world in exchange for a period of indentured servitude.  Just with a more palatable division of labor and requirements.   

Remember Musk is holding the strings.  He's not under a fiduciary duty to maximize profit.  Let's say with 24hour reuse he can relaunch a Falcon9 for $1M.  When he's got the operation running full speed and making tons of money, he can give away pro-bono launches for cost all he wants.  Just because a revenue producing asset like a GSO sat will pay a list price of $40M doesn't mean Musk can't give away a heavily subsidized launch and probably structure it as some kind of charitable contribution and get a tax deduction.  He could also do something like provide heavily subsidized launches that still turn a profit to launch non-revenue-producing payloads that are desirable to place into space.   

Back-of-the-napkin estimates (https://en.wikipedia.org/wiki/Interplanetary_Transport_System#Fabrication_cost_projections) of payload costs $70/lb to Mars (and certainly far lower to other interesting destinations I can think ok) puts an enormous amount of business opportunity in play.

And it's with all this in mind that I think Musk gets into the Nuclear Business when profits permit.
AC in NC, I just cross posted this to the Eaely Ogganization, structure and economics of a mars base thread. It seemed to fit.


https://forum.nasaspaceflight.com/index.php?topic=39785.msg1682113#msg1682113 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1682113#msg1682113)


Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/18/2019 02:05 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/18/2019 02:25 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil

Short answer: Yes
kWh is energy and
1 kWh=3600000 joules

one watt second = 1 joule and go from there.

And if I get where you are going with nuclear. The questions is how do you get rid of waste heat?
Use it to heat living quarters? Ugh! I don't like fluids from a reactor flowing in my living space.
Radiate it? Big structures like solar panels. Size depends on temperature.
Cooling loops underground? Possible melting of permafrost and instability.
Air cooling? Not very dense air.

Title: Re: Power options for a Mars settlement
Post by: livingjw on 06/18/2019 02:28 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil

1) Electrical and thermal power output would be in kW.
2) Yes

John
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/18/2019 02:38 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil
The power is in kW
The energy is in kWh.  Or joules/s(W) x 3600s per hour.

The unit is not very efficient thermally, however this allows it to have simpler components, and a smaller radiator.  In a sense it wastes uranium, but saves on overall mass.
The radiator is on the secondary fluid system.  The heat pipes are the primary loop, these are the ones seeing radiation.
If you want you can have a third level loop for base heating.
The kilopower reactor is not well shielded.  You need to install it far from your base, or bury it hand have a cooling system in the soil, or add shielding and mass.  This disadvantages it a bit.
You can easily find images of it on MArs surface. The radiator is not that large
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/18/2019 02:43 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil
The power is in kW
The energy is in kWh.  Or joules/s(W) x 3600s per hour.

The unit is not very efficient thermally, however this allows it to have simpler components, and a smaller radiator.  In a sense it wastes uranium, but saves on overall mass.
The radiator is on the secondary fluid system.  The heat pipes are the primary loop, these are the ones seeing radiation.
If you want you can have a third level loop for base heating.
The kilopower reactor is not well shielded.  You need to install it far from your base, or bury it hand have a cooling system in the soil, or add shielding and mass.  This disadvantages it a bit.
You can easily find images of it on MArs surface. The radiator is not that large

So I haven't done the calcs.
What size is the radiator assuming water based cooling loop. How does it compare to the equivalent power solar array? Also the average power solar array?

thanks
I am lazy :)
Title: Re: Power options for a Mars settlement
Post by: Dave G on 06/18/2019 03:29 pm
The power is in kW
The energy is in kWh.  Or joules/s(W) x 3600s per hour.

Good point.  Many seem to confuse energy with power. 

The basic equation is: Energy = Power x Time

Each of these can have various types of units, for example:
Energy can be in kWh, joules, BTUs, ergs, calories, Kilotons of TNT, etc.
Power can be in watts, horsepower, etc.
Time can be seconds, minutes, hours, etc.

You can convert between these units using various online calculators.

A good example of all this is to ask the question: How much energy does a 100-watt light bulb use?
If you never turn it on, it uses no energy at all. If you turn it on for 10 hours it uses 1kWh.
Title: Re: Power options for a Mars settlement
Post by: Keldor on 06/18/2019 04:10 pm
Concerning kilowatt reactors in general, SpaceX has mentioned offhandedly that they're going to need something on the order of a megawatt for fuel production.

Since sending 100 or more kilowatt reactors seems like a really dumb way of doing it, they're going to have to design something from scratch.  It shouldn't be especially hard, though.  It's a fraction of the power used for a nuclear submarine, for instance.  The trickiest part is cooling.

Thinking about it, an open coolant system using ice for the ISRU may work.  They can feed in ice beyond the amount needed for ISRU production if needed, with the excess heat dumped into vaporizing the extra ice, which can then be vented to the environment, where it freezes back into "snow", and can be shoveled back into the system.  It can all be convenienly located so the vents dump the vapor right over the site they're already digging ice up from.  Since it is basically snow, it shouldn't greatly contribute to extra wear and tear on the mining equipment, provided it stays localized enough for easy recovery (though it might not...  Water vapor is a good deal lighter than CO2, so you're going to tend to get a updraft of steam going high into the sky).

Another option is not to bring the excess coolant all the way to vapor.  Instead, you melt it and heat it and pour out into a pool.  You're going to still be loosing a lot of water to boiloff, but hopefully enough will remain to allow most of it to be recycled.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/18/2019 04:13 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil
The power is in kW
The energy is in kWh.  Or joules/s(W) x 3600s per hour.

The unit is not very efficient thermally, however this allows it to have simpler components, and a smaller radiator.  In a sense it wastes uranium, but saves on overall mass.
The radiator is on the secondary fluid system.  The heat pipes are the primary loop, these are the ones seeing radiation.
If you want you can have a third level loop for base heating.
The kilopower reactor is not well shielded.  You need to install it far from your base, or bury it hand have a cooling system in the soil, or add shielding and mass.  This disadvantages it a bit.
You can easily find images of it on MArs surface. The radiator is not that large

So I haven't done the calcs.
What size is the radiator assuming water based cooling loop. How does it compare to the equivalent power solar array? Also the average power solar array?

thanks
I am lazy :)
There are too many options for a simple answer.
-If you can melt ice with the waste heat you have one answer.  (basically no radiator, but what is the mass of an ice melter?)
-If you heat the base, then it's a second answer.  You need to design the base first :-(
-If you just reject the heat its a third answer.  That one is available in the literature, or you can eyeball it from the various Youtube videos and pictures.
Same for solar, many answers
Do you have only solar?  Then you need to take storms into account, and design for the worst case that killed Opportunity, 20Watts out of 660 Watts nominal.
You can stop fuel production during storms, that reduces the solar required.
You can mix solar with nuclear.
You can burn some of your propellant store in a generator.  This sounds bad, but the time required overall might not be all that important.  Lots of power, but not much energy.

Solar vs nuclear has no real answer, IMHO.  Nuclear people argue one way, solar ones the other.  Nuclear doesn't quite exist yet, it's still a prototype.  Solar keeps improving, so its a moving target.  Solar also has a huge range of technologies, from simple but less efficient cells to expensive efficient cells.

Nuclear also should eventually scale well, with lower mass per kW the bigger the installation.  Solar is pretty linear, with no reduction with scale.

My own analysis, favoring solar, is here: http://marspedia.org/Cost_of_energy_on_Mars


Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/18/2019 04:56 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil
The power is in kW
The energy is in kWh.  Or joules/s(W) x 3600s per hour.

The unit is not very efficient thermally, however this allows it to have simpler components, and a smaller radiator.  In a sense it wastes uranium, but saves on overall mass.
The radiator is on the secondary fluid system.  The heat pipes are the primary loop, these are the ones seeing radiation.
If you want you can have a third level loop for base heating.
The kilopower reactor is not well shielded.  You need to install it far from your base, or bury it hand have a cooling system in the soil, or add shielding and mass.  This disadvantages it a bit.
You can easily find images of it on MArs surface. The radiator is not that large

So I haven't done the calcs.
What size is the radiator assuming water based cooling loop. How does it compare to the equivalent power solar array? Also the average power solar array?

thanks
I am lazy :)
There are too many options for a simple answer.
-If you can melt ice with the waste heat you have one answer.  (basically no radiator, but what is the mass of an ice melter?)
-If you heat the base, then it's a second answer.  You need to design the base first :-(
-If you just reject the heat its a third answer.  That one is available in the literature, or you can eyeball it from the various Youtube videos and pictures.
Same for solar, many answers
Do you have only solar?  Then you need to take storms into account, and design for the worst case that killed Opportunity, 20Watts out of 660 Watts nominal.
You can stop fuel production during storms, that reduces the solar required.
You can mix solar with nuclear.
You can burn some of your propellant store in a generator.  This sounds bad, but the time required overall might not be all that important.  Lots of power, but not much energy.

Solar vs nuclear has no real answer, IMHO.  Nuclear people argue one way, solar ones the other.  Nuclear doesn't quite exist yet, it's still a prototype.  Solar keeps improving, so its a moving target.  Solar also has a huge range of technologies, from simple but less efficient cells to expensive efficient cells.

Nuclear also should eventually scale well, with lower mass per kW the bigger the installation.  Solar is pretty linear, with no reduction with scale.

My own analysis, favoring solar, is here: http://marspedia.org/Cost_of_energy_on_Mars

I was asking for the panels "rejecting" the heat only answer.
No fans. Just panels radiating heat away.


Probably the best answer will be nuclear with lots of "rodwells" to melt ice and supply water for fuel and building materials(use water just like cement).
Title: Re: Power options for a Mars settlement
Post by: Keldor on 06/18/2019 05:01 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil
The power is in kW
The energy is in kWh.  Or joules/s(W) x 3600s per hour.

The unit is not very efficient thermally, however this allows it to have simpler components, and a smaller radiator.  In a sense it wastes uranium, but saves on overall mass.
The radiator is on the secondary fluid system.  The heat pipes are the primary loop, these are the ones seeing radiation.
If you want you can have a third level loop for base heating.
The kilopower reactor is not well shielded.  You need to install it far from your base, or bury it hand have a cooling system in the soil, or add shielding and mass.  This disadvantages it a bit.
You can easily find images of it on MArs surface. The radiator is not that large

So I haven't done the calcs.
What size is the radiator assuming water based cooling loop. How does it compare to the equivalent power solar array? Also the average power solar array?

thanks
I am lazy :)
There are too many options for a simple answer.
-If you can melt ice with the waste heat you have one answer.  (basically no radiator, but what is the mass of an ice melter?)
-If you heat the base, then it's a second answer.  You need to design the base first :-(
-If you just reject the heat its a third answer.  That one is available in the literature, or you can eyeball it from the various Youtube videos and pictures.
Same for solar, many answers
Do you have only solar?  Then you need to take storms into account, and design for the worst case that killed Opportunity, 20Watts out of 660 Watts nominal.
You can stop fuel production during storms, that reduces the solar required.
You can mix solar with nuclear.
You can burn some of your propellant store in a generator.  This sounds bad, but the time required overall might not be all that important.  Lots of power, but not much energy.

Solar vs nuclear has no real answer, IMHO.  Nuclear people argue one way, solar ones the other.  Nuclear doesn't quite exist yet, it's still a prototype.  Solar keeps improving, so its a moving target.  Solar also has a huge range of technologies, from simple but less efficient cells to expensive efficient cells.

Nuclear also should eventually scale well, with lower mass per kW the bigger the installation.  Solar is pretty linear, with no reduction with scale.

My own analysis, favoring solar, is here: http://marspedia.org/Cost_of_energy_on_Mars

The drop of power production could be (and probably is) much worse than the numbers we got back from Opportunity.  Remember, once power got low enough the rover shut off, so we don't know how low it truely got.  We need to use tau values measured by Curiosity to test solar panels in the lab to really get a good idea.

Before Opportunity went dark, they measured a tau > 10.  This corresponds to 99.995% of sunlight being blocked.  The dust storm that Opportunity and Spirit did in fact survive much earlier in their missions appears to have had a tau consistantly higher than 4 over the span of multiple months, corresponding to 98% of sunlight being blocked.  We can expect power production to potentially drop to 0 for extended periods.  Some backup source will be needed.

Now, it's hard to understate just how much fuel Starship needs to return.  This means that even a small fraction diverted through a fuel cell will be enough to keep life support running for some time.  The real danger is having several months of fuel production loss resulting in them missing their return window.  However, providing enough supplies to cover a contingency of staying on Mars an additional 2 years until the next launch window is perfectly reasonable.  The worst case is if a major dust storm happens to hit right around the time they arrive, preventing them from producing any reserve at all.  Presumably they would just bring enough fuel to provide life support in the case of complete production failure to last until a relief mission can be sent during the next launch window.  This could include ISRU v.2 (and more supplies) if they wanted to try again, or just a fleet of tankers carrying enough fuel to send them home at the cost of several expended Sharships otherwise.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/18/2019 05:06 pm
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil
The power is in kW
The energy is in kWh.  Or joules/s(W) x 3600s per hour.

The unit is not very efficient thermally, however this allows it to have simpler components, and a smaller radiator.  In a sense it wastes uranium, but saves on overall mass.
The radiator is on the secondary fluid system.  The heat pipes are the primary loop, these are the ones seeing radiation.
If you want you can have a third level loop for base heating.
The kilopower reactor is not well shielded.  You need to install it far from your base, or bury it hand have a cooling system in the soil, or add shielding and mass.  This disadvantages it a bit.
You can easily find images of it on MArs surface. The radiator is not that large

So I haven't done the calcs.
What size is the radiator assuming water based cooling loop. How does it compare to the equivalent power solar array? Also the average power solar array?

thanks
I am lazy :)
There are too many options for a simple answer.
-If you can melt ice with the waste heat you have one answer.  (basically no radiator, but what is the mass of an ice melter?)
-If you heat the base, then it's a second answer.  You need to design the base first :-(
-If you just reject the heat its a third answer.  That one is available in the literature, or you can eyeball it from the various Youtube videos and pictures.
Same for solar, many answers
Do you have only solar?  Then you need to take storms into account, and design for the worst case that killed Opportunity, 20Watts out of 660 Watts nominal.
You can stop fuel production during storms, that reduces the solar required.
You can mix solar with nuclear.
You can burn some of your propellant store in a generator.  This sounds bad, but the time required overall might not be all that important.  Lots of power, but not much energy.

Solar vs nuclear has no real answer, IMHO.  Nuclear people argue one way, solar ones the other.  Nuclear doesn't quite exist yet, it's still a prototype.  Solar keeps improving, so its a moving target.  Solar also has a huge range of technologies, from simple but less efficient cells to expensive efficient cells.

Nuclear also should eventually scale well, with lower mass per kW the bigger the installation.  Solar is pretty linear, with no reduction with scale.

My own analysis, favoring solar, is here: http://marspedia.org/Cost_of_energy_on_Mars

I was asking for the panels "rejecting" the heat only answer.
No fans. Just panels radiating heat away.


Probably the best answer will be nuclear with lots of "rodwells" to melt ice and supply water for fuel and building materials(use water just like cement).
4m in diameter per kilopower unit according to this source:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012354.pdf
Title: Re: Power options for a Mars settlement
Post by: Dave G on 06/18/2019 05:23 pm
Solar vs nuclear has no real answer, IMHO.  Nuclear people argue one way, solar ones the other.

Yes. For some reason, it seems like most people talk about either solar or nuclear, like they're mutually exclusive. 
By contrast, I think nuclear and solar tend to compliment one another.

People are generally more active during the day. That's human nature. I don't see why it will be different on Mars.
So nuclear supplies baseline power at night, while solar provides the extra power needed during daylight hours.
They'll also need some batteries to smooth out the load curve, but nowhere near the number of batteries they'd require for a solar-only system. And if either system fails, the other can provide enough power for emergency operations. So solar + nuclear provides redundancy.

But Musk's comments seem to indicate they're planning a solar-only solution, so I'm not sure how worthwhile it is diving into the details for a nuclear power source.

If anything, as others have proposed on this thread, I suspect they'll use methane fuel cells (https://www.machinedesign.com/materials/breakthrough-fuel-cell-runs-methane-practical-temperatures) as a redundant power source to cover temporary periods when there's not enough solar irradiation.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/18/2019 05:27 pm
4m in diameter per kilopower unit according to this source:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012354.pdf

So to do the calcs.
1 kW from nuclear requires
pi*2^2=12 sq. meters
or
1 m^2 produces 1/12 kW=80 W/m^2

solar
590 W/m^2

So even if solar is 1/3 for a day thats still 200 W/m^2
So is nuclear worth it with simple radiators?
Did I make a mistake in my calcs?

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/18/2019 05:38 pm
4m in diameter per kilopower unit according to this source:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012354.pdf

So to do the calcs.
1 kW from nuclear requires
pi*2^2=12 sq. meters
or
1 m^2 produces 1/12 kW=80 W/m^2

solar
590 W/m^2

So even if solar is 1/3 for a day thats still 200 W/m^2
So is nuclear worth it with simple radiators?
Did I make a mistake in my calcs?
Yes, you forgot solar is only 20-30% efficient, and you need to remove another 20% because Mars air is so opaque.  Solar works out to about 40W/m2 on average over a year.
And a kilopower is 10 kW, so its 800 W/m2.

Nuclear will cover 1/20 of the area of solar.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 06/18/2019 05:51 pm
I read this conversation.... what do you mean worth it? Your calculation appears to be considering if Kilopower is worth the "space", or area/volume it heats. And You seem to be considering the "waste" heat a problem.
Well the waste heat is not a problem, as if you use the Kilopower for electricity alone, it has to be places some distance from the base, where space is "free". (and each comes with sufficient radiotors built in) They are barely radioactive before startup, and become so during use. They self regulate so drawing more power (heat or electricity, which is also heat transformed into electricity via the included Stirling engines, causes a faster reaction, and reducing power drawn allows the reactor to slow naturally. If you have a use for the heat for example melting rodwells then the reactor is more valuable, and the space it takes up, is the space in and around the rodwells it melts.

It doesn't matter if Nuclear is 20x more area efficient. There is plenty of space! Transit mass matters at least at first. And special considerations launching nuclear material may matter, with the public and regulatory approval affecting schedule. (Edit:) Ease of installation matters, Solar is easier than most nuclear scenarios, assuming the Kilopower is partially below ground for safety. (/edit)

However IMO nuclear is only really needed where solar, with battery storage, and chemical storage (methane for an engine) are difficult to manage, such as a minimum backstop for long sandstorms, for bases near or beyond the "arctic" circles, where solar is not available for winter months, and obviously on our Moon with its 13 day night! Also for heat for rodwells etc, if solar isn't meeting the curve! (need and schedule). Also it needs trialling where it is not critical, so it is available when finally required. Perhaps I should not say this as I don't want to re-start this debate!
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/18/2019 05:55 pm
4m in diameter per kilopower unit according to this source:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012354.pdf

So to do the calcs.
1 kW from nuclear requires
pi*2^2=12 sq. meters
or
1 m^2 produces 1/12 kW=80 W/m^2

solar
590 W/m^2

So even if solar is 1/3 for a day thats still 200 W/m^2
So is nuclear worth it with simple radiators?
Did I make a mistake in my calcs?
Yes, you forgot solar is only 20-30% efficient, and you need to remove another 20% because Mars air is so opaque.  Solar works out to about 40W/m2 on average over a year.
And a kilopower is 10 kW, so its 800 W/m2.

Nuclear will cover 1/20 of the area of solar.

Whoops!
Thats why I like when other people are doing the calcs!

so I got 590W/m^2 from here:
https://www.firsttheseedfoundation.org/resource/tomatosphere/background/sunlight-mars-enough-light-mars-grow-tomatoes/
so 590W/m^2 *.30% eff panels=177W/m^2. 177W/m^2 / 3 for daily cycle=88W/m^2 so 80 versus 40 I can see being seasonality and the 20% atmosphere reduction.
 
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/18/2019 06:02 pm
I read this conversation.... what do you mean worth it? Your calculation appears to be considering if Kilopower is worth the "space", or area/volume it heats. And You seem to be considering the "waste" heat a problem.
Well the waste heat is not a problem, as if you use the Kilopower for electricity alone, it has to be places some distance from the base, where space is "free". (and each comes with sufficient radiotors built in) They are barely radioactive before startup, and become so during use. They self regulate so drawing more power (heat or electricity, which is also heat transformed into electricity via the included Stirling engines, causes a faster reaction, and reducing power drawn allows the reactor to slow naturally. If you have a use for the heat for example melting rodwells then the reactor is more valuable, and the space it takes up, is the space in and around the rodwells it melts.

It doesn't matter if Nuclear is 20x more area efficient. There is plenty of space! Transit mass matters at least at first. And special considerations launching nuclear material may matter, with the public and regulatory approval affecting schedule. (Edit:) Ease of installation matters, Solar is easier than most nuclear scenarios, assuming the Kilopower is partially below ground for safety. (/edit)

However IMO nuclear is only really needed where solar, with battery storage, and chemical storage (methane for an engine) are difficult to manage, such as a minimum backstop for long sandstorms, for bases near or beyond the "arctic" circles, where solar is not available for winter months, and obviously on our Moon with its 13 day night! Also for heat for rodwells etc, if solar isn't meeting the curve! (need and schedule). Also it needs trialling where it is not critical, so it is available when finally required. Perhaps I should not say this as I don't want to re-start this debate!

I was just trying to get a feel for the area of radiators for heat rejection versus solar panels which look the same. If the panels were to produce the same average power then the choice for would be simple. I believe there is a similar argument for SBPS for the size of the antenna versus solar panels.

Of course solar's intermittent nature changes the equation considerably. Also heat for melting ice.
 
Title: Re: Power options for a Mars settlement
Post by: Keldor on 06/18/2019 06:16 pm
4m in diameter per kilopower unit according to this source:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012354.pdf

So to do the calcs.
1 kW from nuclear requires
pi*2^2=12 sq. meters
or
1 m^2 produces 1/12 kW=80 W/m^2

solar
590 W/m^2

So even if solar is 1/3 for a day thats still 200 W/m^2
So is nuclear worth it with simple radiators?
Did I make a mistake in my calcs?
Yes, you forgot solar is only 20-30% efficient, and you need to remove another 20% because Mars air is so opaque.  Solar works out to about 40W/m2 on average over a year.
And a kilopower is 10 kW, so its 800 W/m2.

Nuclear will cover 1/20 of the area of solar.

Commercial solar panels give you something like 150-200W/m2 in good sunlight.  But this is on Earth.  Accounting for Mars being 150% further from the sun than Earth as well as atmosperic attunuation (careful with this one - Earth's atmosphere attenuates too), I get 50-60W/m2 during the day.  Divide that by 2 since night time is a thing and you have 25-30W/m2 long term average in good weather.

It's hard to qualify how effecient commercial panels are versus ones you'd put on Mars since there are conflicting factors.  On the one hand, solar panels that can survive on Mars are much less researched than panels for use on Earth.  On the other hand, on Mars, price isn't much of an issue.  Buying a panel that costs 5x as much for a 10% effeciency increase makes little sense on Earth, but on Mars, the cost of sending it out there completely overwhelms the cost of the panels themselves.

Anyway, as far as area goes, looking at the diameter of the kilowatt reactors is the wrong number.  If you pack them together like that they'll end up absorbing radiated heat from each other and be much less effecient.  Thankfully, the paper also provides numbers for absolute radiator area, which appears to be as good as 500W/m2.

But kilowatt reactors are really the wrong tool if you need to produce a megawatt of power, as they need to.  A small nuclear submarine class reactor might be the best option.  It shouldn't be too hard to change the coolant system to pumping through a large radiator array on Mars.  I'm getting that a 30MW reactor is 1.5m wide and 2m tall, and weighs 20 tons without coolant, which is well within Starship's payload capability.  Mind you, this only includes the core, the turbines and radiators are seperate, but still.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 06/18/2019 06:56 pm
I read this conversation.... what do you mean worth it? Your calculation appears to be considering if Kilopower is worth the "space", or area/volume it heats. And You seem to be considering the "waste" heat a problem.
Well the waste heat is not a problem, as if you use the Kilopower for electricity alone, it has to be places some distance from the base, where space is "free". (and each comes with sufficient radiotors built in) They are barely radioactive before startup, and become so during use. They self regulate so drawing more power (heat or electricity, which is also heat transformed into electricity via the included Stirling engines, causes a faster reaction, and reducing power drawn allows the reactor to slow naturally. If you have a use for the heat for example melting rodwells then the reactor is more valuable, and the space it takes up, is the space in and around the rodwells it melts.

It doesn't matter if Nuclear is 20x more area efficient. There is plenty of space! Transit mass matters at least at first. And special considerations launching nuclear material may matter, with the public and regulatory approval affecting schedule. (Edit:) Ease of installation matters, Solar is easier than most nuclear scenarios, assuming the Kilopower is partially below ground for safety. (/edit)

However IMO nuclear is only really needed where solar, with battery storage, and chemical storage (methane for an engine) are difficult to manage, such as a minimum backstop for long sandstorms, for bases near or beyond the "arctic" circles, where solar is not available for winter months, and obviously on our Moon with its 13 day night! Also for heat for rodwells etc, if solar isn't meeting the curve! (need and schedule). Also it needs trialling where it is not critical, so it is available when finally required. Perhaps I should not say this as I don't want to re-start this debate!

Any process that consumes what you are trying to produce (methane) will be expensive. 
Also fuel cells are not very efficient and should be used as a power source of last resort. 
Batteries are much more efficient and cheaper. 
Having multiple types of power makes the system resilient at the cost of complexity. 
Title: Re: Power options for a Mars settlement
Post by: Dave G on 06/18/2019 08:01 pm
Any process that consumes what you are trying to produce (methane) will be expensive. 
Only if you're using it regularly.  As a short-term backup solution to cover failures, it's just the opposite.
Title: Re: Power options for a Mars settlement
Post by: Lar on 06/18/2019 09:15 pm
If you need to mount flat radiators, can you put solar panels on them too? Is that even viable?
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 06/19/2019 01:18 am
If you need to mount flat radiators, can you put solar panels on them too? Is that even viable?

Err, no? If the radiator is in the same plane and a small type radiator (thus runs very hot), it will cook your PV and reduce power output. If it was orthogonal some IR from the radiator will still hit the PV or it's backing substrate due to proximity. Now if you were using some sort of lower temperature liquid for the heat transfer medium, you might be able to run tube radiators on top of rollable PV panels (use the liquid like a party favor blower to unroll the PV) if the temperature won't cook the PV.


It seems people are forgetting the Kilopower guys at Sandia were proposing a Megapower variant (1MW in a cargo container roughly), using a brayton cycle turbogenerator, and maybe a supercritical CO2 power cycle? Cooling the CO2 is a little problematic since you actually want to run the radiator hot, and not cool too much so that the CO2 solidifies (probably want to run the full cycle all supercritical, so that's pretty hot at the rejection temperature).
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/19/2019 01:21 am
The radiators are not that hot, somewhere between 30 and 90C, but they are kind of small.

Efficiency of solar cells goes down with heat, 0,25% per C (standard set at 25C) according to this:
https://www.civicsolar.com/support/installer/articles/how-does-heat-affect-solar-panel-efficiencies


Anyway, with the Paul451 rolls, who needs reactors anyway?  According to this handy calculation, I should be able to store at least 500m of cell in a single unit, if my 6mm allowance is correct, and almost 1km of cells if the thickness is 3mm!
https://www.handymath.com/cgi-bin/rollen.cgi

They're so long they are falling off the side of Mars in image 3!!!

Each unit produces a peak of about 150-200 kW of power.  Should include an inverter that converts to AC, then a transform to 20-30 kV, depending on the grid.  Lower voltages will require cables that would be much too large.

So a single one of these rolls might be equal to 15 to 20 kilopower units.

The megapower unit is still a gleam in the designer's eyes.  As far as I know.





Title: Re: Power options for a Mars settlement
Post by: watermod on 06/19/2019 02:12 am
If you need to mount flat radiators, can you put solar panels on them too? Is that even viable?

Some interesting links on the topic:
http://toughsf.blogspot.com/2017/11/advanced-solar-energy-in-space-part-i.html (http://toughsf.blogspot.com/2017/11/advanced-solar-energy-in-space-part-i.html)
http://toughsf.blogspot.com/2017/12/advanced-solar-energy-in-space-part-ii.html (http://toughsf.blogspot.com/2017/12/advanced-solar-energy-in-space-part-ii.html)
Title: Re: Power options for a Mars settlement
Post by: Norm38 on 06/19/2019 03:17 am
Just don’t forget to include the nighttime batteries in the mass budget.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/19/2019 03:20 am
Just don’t forget to include the nighttime batteries in the mass budget.
Solar still wins.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 06/19/2019 03:31 am
Just don’t forget to include the nighttime batteries in the mass budget.

Amount of batteries depends a lot on the ISRU machinery. If electrolysis needs to run all night a lot. If it can be shut off over night without damage to the equipment not so much. Longevity of electrolysis equipment may or may not depend on continuous operation.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 06/19/2019 03:41 am
Just don’t forget to include the nighttime batteries in the mass budget.

Please don't generalize be specific...
How about locally made lead-acid batteries?  Easy, efficient, low tech.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/19/2019 04:20 am
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil

Short answer: Yes
kWh is energy and
1 kWh=3600000 joules

one watt second = 1 joule and go from there.

And if I get where you are going with nuclear. The questions is how do you get rid of waste heat?
Use it to heat living quarters? Ugh! I don't like fluids from a reactor flowing in my living space.
Radiate it? Big structures like solar panels. Size depends on temperature.
Cooling loops underground? Possible melting of permafrost and instability.
Air cooling? Not very dense air.


Thank you all for your responses.

Here’s the core idea. Electrolysis is a major power hog for props ISRU. The higher the temp the more efficient.  KRUSTY ran ~800C core temp. The waste heat would be lower but my guess is still high enough to have significant impact on electrolysis power requirements. The calcs I hope to run will be a first hack at looking at how close a match a 10kw unit might be if thermally dedicated to electrolysis.

I’m working up through page 45 on his thread and have seen all the arguments pro/con on nuke power. ISTM a single power archetecture is a potential single point of failure. If the numbers work it’s another argument pro nuke.

Ignoring the practicality (easier said than done) of pinpoint landing near a water source, a single SS tricked out as a props factory makes sense. The tanks are a freebie. Cargo would be a 10kW kilopower, purification, electrolysis and sabitier (sp?) hardware. PV would still be needed. Extraction, PV and materials handling equipment probably on a second and maybe third SS. Core factory would need no deployment. It’s all plumbed in, wired up and waiting for water and PV hookup.

This would, at first glance, be an undersized load for an SS in both mass and volume (I think). Given that, as mentioned in an earlier post that I can not pinpoint, max electrode degradation occurs during startup, it makes sense to keep electrolysis running constantly. This implies H2, O2 and water storage. Oversized the sabitire and run it only during the day when PV is available with stored and concurrently produced H2. Sabiter is exothermic and can run with minimal power but blowing in the CO2 and the product liquification is power hungry.

The waste heat, after electrolysis, to be used to melt the the ore. Between the waste heat and low ambiant pressure it should be possible to purify by distillation without electrical power, except for pumps. I bet some clever design work could do away with some pumping. No filters required but the still would need cleaning.

A stock kilopower (not that there is such a thing) is only shielded around a portion of its circumference. Give it full shielding so the plumbing, always a problem, can be maintained.

If the gods smile this is all within the capabilities of a single SS.

Given enough time I think I could rough in the power numbers except for some glaring holes.
1) Can anybody point me to a table showing electrolysis efficiency vs temp?
2) I can find nothing on thermal transport from the Stirling’s to the OTS radiator. This would obviously have no purpose in the above proposal. Is a fluid used? What fluid?
2) What would a secondary coolant temp be following the Stirling cycle?


Phil


Title: Re: Power options for a Mars settlement
Post by: Semmel on 06/19/2019 09:18 am
The problem with nuclear is not that it wouldnt be technically desirable. The problem is to develop it in the first place, given the problems that are attached to getting nuclear material and setting up a lab to do it. I think the amount of paperwork to get any nuclear testing done is quite enormous and might be economically prohibitive to SpaceX.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 06/19/2019 11:51 am
Back several years ago, Russia developed a 20 ton reactor that could be used in space.  Now something like that could be launched unfueled to Mars.  The nuclear material to operate it can be launched in a lead box.  Small and heavy but not 20 tons separately if need be.  It can be placed in a hole or crater nearby to supplement solar at night and when the solar panels need cleaning of dust.  It's excess heat can be used to melt ice for water and fuel production. 

I think a small nuclear power facility could and should be developed for Mars.  If not initially, at least within 2 or 3 cycles of landings. 
Title: Re: Power options for a Mars settlement
Post by: krsears on 06/19/2019 01:19 pm
Back several years ago, Russia developed a 20 ton reactor that could be used in space.  Now something like that could be launched unfueled to Mars.  The nuclear material to operate it can be launched in a lead box.  Small and heavy but not 20 tons separately if need be.  It can be placed in a hole or crater nearby to supplement solar at night and when the solar panels need cleaning of dust.  It's excess heat can be used to melt ice for water and fuel production. 

I think a small nuclear power facility could and should be developed for Mars.  If not initially, at least within 2 or 3 cycles of landings.

Bechtel could solve the energy issue for Mars.  They have permission of the US Gov't to work with nuclear material, AND they are familiar with small reactors that put out large amounts of energy.

https://en.wikipedia.org/wiki/A1B_reactor

Kendall
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/19/2019 03:16 pm
One of the best features of the kilopower design is that it's self regulating with no moving parts. The core stays in a fairly narrow temperature range from the reaction decreasing if it gets hotter and increasing when you draw more heat. You can remove the heatpipe altogether without the reactor overheating. That same feature also keeps heat output constant as the fuel is used up. No moving parts in the core. They hope for a 40 year lifespan with no maintenance except Sterling replacement, which is designed to be fast and easy.


Spot on re: self regulation.


NASA says 10 year lifetime. I’ve also seen 12-15 years stated somewhere. Maybe this is the Stirling life expectancy?


Minor nit: one moving part. A control slug withdrawn from the core for startup can be reinserted to varying degrees to force a drop in output. This can go all the way to warm standby.


Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/19/2019 03:40 pm
Reactors use so little fuel, the fuel can be launched separately in a lead box.  In case of rocket failure the lead box of a handful of fission material will be shielded when it crashes into the ocean.  It can then be recovered.  It can also be placed in a capsule with LAS in case of failure, it can be recovered.  Fuel is small compared to the reactor itself which can be launched separately.

I'm more concerned about the rocket exploding somewhere near the launch pad. Once it's out over the ocean, or high up in the atmosphere, exploded radioactive material would tend to disperse to non-harmful levels.

Yes, you could launch it separately in a capsule with a launch abort system, but we just saw one of those explode on the pad.

Yes, you could put it in a lead box, but how will that fare in an explosion?

Also, the kilopower white paper (https://www.nasa.gov/sites/default/files/atoms/files/ns_kilopower_fs_180111.pdf) said "The core is a solid block of a uranium alloy", so it may be significantly larger than pure uranium.


For the 1kw prototype it was described as a cylinder roughly the size of a roll of paper towels. I got the impression that it scaled up by lengthining the core.


Phil
Title: Re: Power options for a Mars settlement
Post by: Kansan52 on 06/19/2019 04:25 pm
Apollo 13's 3.9 kg of plutonium reentered with no dispersal. IMO, fissionable material can be launched safely based on past accidents.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/19/2019 04:54 pm
PV farm deployment concept, applicable to a base or a grid farm (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437):

Unroll flat with Renovagen Rapid Roll "i" (http://www.renovagen.com/products/rapid-roll-i/)-class mechanism.

Lift, angle and tension on 10-meter pylon wires.

DC distribution hw and other hw (e.g., triboelectricity rectifier/inverter (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850762#msg1850762)) would be incorporated into the deployment container.

I suspect crew members will set up the solar array. 

Remember, the plan says propellant production won't start until after crew members arrive on the surface.

The initial cargo missions just get everything in place, i.e. get the components on the Mars surface.


SX plans are as supple as their engineering. I wouldn’t consider any plan this old and this far from implementation as cast in stone.


Phil
Title: Re: Power options for a Mars settlement
Post by: Lar on 06/19/2019 07:42 pm
Bechtel could solve the energy issue for Mars.  They have permission of the US Gov't to work with nuclear material, AND they are familiar with small reactors that put out large amounts of energy.

https://en.wikipedia.org/wiki/A1B_reactor

Kendall
Bechtel is a good firm to get onside if you can. They are privately held, so might take the long view on this stuff rather than wanting to be paid in full for R&D up front, and they also are a player in all kinds of construction and engineering projects. so yeah!
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 06/19/2019 11:58 pm
[...]

Am I interpreting your comments correctly, that you want to use the 30kW waste heat of the 10kW electrical generator to heat the electrolysis system? You have to remember that the rate of heat-flow scales with the fourth power of the temperature difference. For example, the size of heat-exchanges and radiators both scale with the fourth-power of the temperature difference. Stick another stage in the middle and (for eg) halve each side's temp difference, you reduce the rate of heat flow (hence power) by 16-fold, requiring 16 times the heat exchange surface area (or some other equivalent change.)

While it's sometimes possible to use waste heat in industrial processes, there are usually costs paid elsewhere.

Resistive and induction heaters are nearly 100% efficient. So often it's better to run the electrical system at its maximum efficiency and just use electric heaters, rather than run the electrical system at a much lower efficiency in order to tap off some low-grade waste heat.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/20/2019 02:36 am
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil

Short answer: Yes
kWh is energy and
1 kWh=3600000 joules

one watt second = 1 joule and go from there.

And if I get where you are going with nuclear. The questions is how do you get rid of waste heat?
Use it to heat living quarters? Ugh! I don't like fluids from a reactor flowing in my living space.
Radiate it? Big structures like solar panels. Size depends on temperature.
Cooling loops underground? Possible melting of permafrost and instability.
Air cooling? Not very dense air.


Thank you all for your responses.

Here’s the core idea. Electrolysis is a major power hog for props ISRU. The higher the temp the more efficient.  KRUSTY ran ~800C core temp. The waste heat would be lower but my guess is still high enough to have significant impact on electrolysis power requirements. The calcs I hope to run will be a first hack at looking at how close a match a 10kw unit might be if thermally dedicated to electrolysis.

I’m working up through page 45 on his thread and have seen all the arguments pro/con on nuke power. ISTM a single power archetecture is a potential single point of failure. If the numbers work it’s another argument pro nuke.

Ignoring the practicality (easier said than done) of pinpoint landing near a water source, a single SS tricked out as a props factory makes sense. The tanks are a freebie. Cargo would be a 10kW kilopower, purification, electrolysis and sabitier (sp?) hardware. PV would still be needed. Extraction, PV and materials handling equipment probably on a second and maybe third SS. Core factory would need no deployment. It’s all plumbed in, wired up and waiting for water and PV hookup.

This would, at first glance, be an undersized load for an SS in both mass and volume (I think). Given that, as mentioned in an earlier post that I can not pinpoint, max electrode degradation occurs during startup, it makes sense to keep electrolysis running constantly. This implies H2, O2 and water storage. Oversized the sabitire and run it only during the day when PV is available with stored and concurrently produced H2. Sabiter is exothermic and can run with minimal power but blowing in the CO2 and the product liquification is power hungry.

The waste heat, after electrolysis, to be used to melt the the ore. Between the waste heat and low ambiant pressure it should be possible to purify by distillation without electrical power, except for pumps. I bet some clever design work could do away with some pumping. No filters required but the still would need cleaning.

A stock kilopower (not that there is such a thing) is only shielded around a portion of its circumference. Give it full shielding so the plumbing, always a problem, can be maintained.

If the gods smile this is all within the capabilities of a single SS.

Given enough time I think I could rough in the power numbers except for some glaring holes.
1) Can anybody point me to a table showing electrolysis efficiency vs temp?
2) I can find nothing on thermal transport from the Stirling’s to the OTS radiator. This would obviously have no purpose in the above proposal. Is a fluid used? What fluid?
2) What would a secondary coolant temp be following the Stirling cycle?


Phil
The reactor waste heat will not be very hot.  For a 4m radiator, it's either 90C if only one side is radiating or 33C if both sides are radiating.  Expecting something in between, then 50C will not have much impact on Electrolysis.  The temperatures seem to be more in the 800C to get results.
This would need to be a 'topping' process, and is incompatible with kilopower design.

Better off melting ice and heating the base at night.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/20/2019 05:59 am
I'm working on an idea that fits into this thread but want to work through some details before I throw it out. Despite the numbers being available in this thread and elsewhere, if I don't work through it myself, I don't really understand it. Not being an engineer, I've got some very basic questions and would appreciate some help if anybody has the time.

According to https://en.wikipedia.org/wiki/Kilopower (https://en.wikipedia.org/wiki/Kilopower) a 10kW kilopower has a thermal output of 43.3kW. Looked for a primary source and came up dry. Edit: Any non fluff NASA stuff out there? Found it.

1) Are both the electrical and thermal outputs actually kWh?

2) Does this mean that 10kW of thermal is used in electrical production and the unit needs to shed 33.3kW thermal?


Phil

Short answer: Yes
kWh is energy and
1 kWh=3600000 joules

one watt second = 1 joule and go from there.

And if I get where you are going with nuclear. The questions is how do you get rid of waste heat?
Use it to heat living quarters? Ugh! I don't like fluids from a reactor flowing in my living space.
Radiate it? Big structures like solar panels. Size depends on temperature.
Cooling loops underground? Possible melting of permafrost and instability.
Air cooling? Not very dense air.


Thank you all for your responses.

Here’s the core idea. Electrolysis is a major power hog for props ISRU. The higher the temp the more efficient.  KRUSTY ran ~800C core temp. The waste heat would be lower but my guess is still high enough to have significant impact on electrolysis power requirements. The calcs I hope to run will be a first hack at looking at how close a match a 10kw unit might be if thermally dedicated to electrolysis.

I’m working up through page 45 on his thread and have seen all the arguments pro/con on nuke power. ISTM a single power archetecture is a potential single point of failure. If the numbers work it’s another argument pro nuke.

Ignoring the practicality (easier said than done) of pinpoint landing near a water source, a single SS tricked out as a props factory makes sense. The tanks are a freebie. Cargo would be a 10kW kilopower, purification, electrolysis and sabitier (sp?) hardware. PV would still be needed. Extraction, PV and materials handling equipment probably on a second and maybe third SS. Core factory would need no deployment. It’s all plumbed in, wired up and waiting for water and PV hookup.

This would, at first glance, be an undersized load for an SS in both mass and volume (I think). Given that, as mentioned in an earlier post that I can not pinpoint, max electrode degradation occurs during startup, it makes sense to keep electrolysis running constantly. This implies H2, O2 and water storage. Oversized the sabitire and run it only during the day when PV is available with stored and concurrently produced H2. Sabiter is exothermic and can run with minimal power but blowing in the CO2 and the product liquification is power hungry.

The waste heat, after electrolysis, to be used to melt the the ore. Between the waste heat and low ambiant pressure it should be possible to purify by distillation without electrical power, except for pumps. I bet some clever design work could do away with some pumping. No filters required but the still would need cleaning.

A stock kilopower (not that there is such a thing) is only shielded around a portion of its circumference. Give it full shielding so the plumbing, always a problem, can be maintained.

If the gods smile this is all within the capabilities of a single SS.

Given enough time I think I could rough in the power numbers except for some glaring holes.
1) Can anybody point me to a table showing electrolysis efficiency vs temp?
2) I can find nothing on thermal transport from the Stirling’s to the OTS radiator. This would obviously have no purpose in the above proposal. Is a fluid used? What fluid?
2) What would a secondary coolant temp be following the Stirling cycle?


Phil
The reactor waste heat will not be very hot.  For a 4m radiator, it's either 90C if only one side is radiating or 33C if both sides are radiating.  Expecting something in between, then 50C will not have much impact on Electrolysis.  The temperatures seem to be more in the 800C to get results.
This would need to be a 'topping' process, and is incompatible with kilopower design.

Better off melting ice and heating the base at night.

On my phone so multi-quote is hard. This is to Paul451 also.

Not being an engineer or a physicist I don’t know from nothin about 4th power etc... but I do realize that if the temp difference is slight the approach to thermal equalibrium for two objects in contact is at a slower rate than at a high temp diff. I think this is the same effect as what you spoke of with a clear quantification. Do I have this right?

Back to the heat. I do know that the kilopower thermal output is 43kW with some portion of that heating sodium hear pipes. Exact portion unknown. The heat pipes in turn deliver enough heat to the hot end of the Stirling’s to generate 10kWh. This leaves 33kW of heat knocking about the system. Since the earlier post i’ve run across a description of the radiator speaking of thermal transport from the Stirling via water heat pipes. Water implies ‘not very hot which is disappointing.

So where does all this heat go? AIUI a carnot cycle has a max theoretical effiency of 50%. If this is correct then the Stirling must receive at least 20kW to deliver 10kW mechanical and probably more to cover ineffiencies. The inneficiencies would, I think, appear as waste heat but I am unclear if this would result in the cold side being warmer than ideal theory predicts, or it would show up elsewhere in the mechanism, or both.

I’d expect the core would be throwing off a lot of heat that gets past the primary heat pipes. I could see this being 20+kW. I wonder if there’s any way to tap this without the core or neutron reflector getting weird and hosing the self regulation?

I want my 33kW for my electrolysis!!! Can’t I have just 10kW? Huh, please? Wahhhhhh!!! (End tantrum)

Is this just another Grand Idea relegated to the dust bin of NSF? Sniff.


Phil





Title: Re: Power options for a Mars settlement
Post by: Paul451 on 06/20/2019 07:10 am
Back to the heat. I do know that the kilopower thermal output is 43kW with some portion of that heating sodium hear pipes. Exact portion unknown. The heat pipes in turn deliver enough heat to the hot end of the Stirling’s to generate 10kWh. This leaves 33kW of heat knocking about the system.

The system pumps 43kW thermal to the hot-side of the Sterling engine. That 10kW electrical is the ~25% efficiency of the Sterling in extracting useful work from the difference between the hot-side (reactor) and the cold-side (the radiator cooling loop). The cold-side of the Sterling is then the hot-side for the radiator.

Every joule of heat produced by the reactor goes through the Sterling (well, in theory, in practice you lose some through the body of the reactor, obviously.) There's no extra energy knocking about. If you want heat, you are taking it from between the Sterling and the radiator, making both less efficient.
Title: Re: Power options for a Mars settlement
Post by: Pete on 06/20/2019 09:33 am
... AIUI a carnot cycle has a max theoretical effiency of 50%...

Nope.
The theoretical efficiency of a Carnot cycle engine is governed by the relative temperatures of the hot and cold side.

Basically, efficiency is 1 - (cold/hot)

Small temperature difference = low efficiency.
for Honking big temperature difference, efficiency can approach 100%

*actual* efficiency will be a bit less than this of course due to friction, conversion losses, etc.

In the case of kilopower under normal operating conditions, "hot" side is about 600c = 873K
and "cold" side is about 400c = 673K
(these due to the limitations of the sodium heat transfer method)
so efficiency is somewhere south of 23%
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 06/20/2019 11:44 am

Not being an engineer or a physicist I don’t know from nothin about 4th power etc... but I do realize that if the temp difference is slight the approach to thermal equalibrium for two objects in contact is at a slower rate than at a high temp diff. I think this is the same effect as what you spoke of with a clear quantification. Do I have this right?



4th power is for heat transfer as radiation. Convection and conduction are linear.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/20/2019 08:49 pm
Back to the heat. I do know that the kilopower thermal output is 43kW with some portion of that heating sodium hear pipes. Exact portion unknown. The heat pipes in turn deliver enough heat to the hot end of the Stirling’s to generate 10kWh. This leaves 33kW of heat knocking about the system.

The system pumps 43kW thermal to the hot-side of the Sterling engine. That 10kW electrical is the ~25% efficiency of the Sterling in extracting useful work from the difference between the hot-side (reactor) and the cold-side (the radiator cooling loop). The cold-side of the Sterling is then the hot-side for the radiator.

Every joule of heat produced by the reactor goes through the Sterling (well, in theory, in practice you lose some through the body of the reactor, obviously.) There's no extra energy knocking about. If you want heat, you are taking it from between the Sterling and the radiator, making both less efficient.


... AIUI a carnot cycle has a max theoretical effiency of 50%...

Nope.
The theoretical efficiency of a Carnot cycle engine is governed by the relative temperatures of the hot and cold side.

Basically, efficiency is 1 - (cold/hot)

Small temperature difference = low efficiency.
for Honking big temperature difference, efficiency can approach 100%

*actual* efficiency will be a bit less than this of course due to friction, conversion losses, etc.

In the case of kilopower under normal operating conditions, "hot" side is about 600c = 873K
and "cold" side is about 400c = 673K
(these due to the limitations of the sodium heat transfer method)
so efficiency is somewhere south of 23%


Paul451 and Pete. Thanks for having the patience while I try to wrap my head around this.

Following the thermal path:

Core generates heat. Some is lost but the bulk is drawn off by the sodium heat pipes. The heat pipes will loose some before getting to the Stirling. The Stirling will convert 10kW into mechanical and the generator will in turn convert the mechanical into electrical. Both the mechanical and the electrical will be less than 100% efficient. A cooling system will draw heat from the cold side of the Stirling. From the original 43kW we've lost 10kW to making electricity and an unknown, but probably small amount to other inefficiencies. For the sake of argument let's assign 3kW to all losses up to this point. We're left with 30kW of heat to work with.

In this mind experiment let's do away with the cold side heat pipes and radiators and wrap a water jacket around the cold side. This would be a full loss cooling system with the water, after heating, going on for electrolysis. Using Pete's numbers this should be ~400C, so we should expect it to flash into steam. Would this steam be at 400C or 200C?

From Wikipedia: https://en.wikipedia.org/wiki/High-temperature_electrolysis (https://en.wikipedia.org/wiki/High-temperature_electrolysis)

To be continued. The editor is hosing me and I keep loosing stuff.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/20/2019 09:08 pm
Contuinued

I'm dying here. It keeps eating my work, so real quick -

If the efficiency increase is linear with with temp increase, and the water entering the cooling jacket is 0C (I know, this would crack the Stirling) the .03% increase of efficiency with each degree of temp rise yealds 6% if the coolant leave the Stirling at 200C and 12% if it leaves at 400C. What would the exit temp actually be?

Heat is needed to melt the water ore and for final distillation. Electrically powered centrifugal separation (no filters needed) would precede distillation. Given that Stirling cooling sets a hard number for flow rate, is there a magic proportioning between electrolysis, melting and distilling that maximizes the use of thermal energy instead of electric? Energy is so dear on Mars that it seems any efficiency should be embraced if practical.

Or does this all go to the NSF dust bin. (Back of hand to forehead, a tear on cheek, a gentle sniff)

Phil
Title: Re: Power options for a Mars settlement
Post by: spacenut on 06/20/2019 09:37 pm
Mars is cold.  Any heat left over from any power production can be converted to melt ice for water and fuel production, heat greenhouses, and heat habitats and production or manufacturing buildings.  I do not believe solar power alone can produce enough power for an ever expanding colony. 
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 06/20/2019 10:00 pm
I don't think there will be any problem in using waste heat. It can be used for heating the habitat, melting ice for the electrolyser, distilling water for human consumption and (heaven forbid) distilling water before electrolysis, should that be necessary.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/20/2019 11:03 pm
Mars is cold.  Any heat left over from any power production can be converted to melt ice for water and fuel production, heat greenhouses, and heat habitats and production or manufacturing buildings.  I do not believe solar power alone can produce enough power for an ever expanding colony.
Yes, an article of faith among the ardently nuclear crowd.

I’m pro-nuclear, too, but if solar is all we’d had, Mars would still be fine. It’d favor sites closer to the equator, but that’s desirable anyway for entry and ascent anyway.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/21/2019 02:05 am
Contuinued

I'm dying here. It keeps eating my work, so real quick -

If the efficiency increase is linear with with temp increase, and the water entering the cooling jacket is 0C (I know, this would crack the Stirling) the .03% increase of efficiency with each degree of temp rise yealds 6% if the coolant leave the Stirling at 200C and 12% if it leaves at 400C. What would the exit temp actually be?

Heat is needed to melt the water ore and for final distillation. Electrically powered centrifugal separation (no filters needed) would precede distillation. Given that Stirling cooling sets a hard number for flow rate, is there a magic proportioning between electrolysis, melting and distilling that maximizes the use of thermal energy instead of electric? Energy is so dear on Mars that it seems any efficiency should be embraced if practical.

Or does this all go to the NSF dust bin. (Back of hand to forehead, a tear on cheek, a gentle sniff)

Phil
You will find joined here a spreadsheet showing an approximation of the kilopower thermal cycle.  First column of the Stirling tab.  It's probably a bit off because It was originally designed for a Brayton gas cycle.
So unfortunately you cannot have access to that nice high heat.  Because the Stirling engine is actually extracting a lot more than 25%, it's extracting something like 75%, but it immediately returns most of it to the compression part of the cycle to run the compressor piston as mechanical energy.  Expansion cools the gas, compression reheats the gas.  So the cooling stream through the radiator is a lot cooler than you would expect at first, just using the 25% to electricity value.  About 100C average.  Plus the surface temperature of the radiator is lower than the coolant temperature because the convective heat transfer between a gas in the cooling circuit and a surface is not all that good.  Heat pipes are tricky so that value may be off but probably not by more than 50C.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/21/2019 02:32 am
I don't think there  will be any problem in using waste heat. It can be used for heating the habitat, melting ice for the electrolyser, distilling water for human consumption and (heaven forbid) distilling water before electrolysis, should that be necessary.

The point of using thermal to assist electrolysis specifically is because it doesn’t  conribute 1:1, as temp rises it goes 1:1+. It increases efficiency. The other applications I spoke of are process coupled to electrolysis. With the SS turnkey props plant loadout I speculated about 1-2 pages back, they would be physically collocated. If you’ve worked with plumbing you’ll appreciate how much physical simplicity help long term.

After electrolysis, if there’s enough heat still available for distillation it might make sense. The heat would be right there for the taking and if you start transporting it too far losses start adding up. If there is a process that gains efficiency with temp that should of course have priority, especially if collocated.

Phil
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/21/2019 02:45 am
I don't think there  will be any problem in using waste heat. It can be used for heating the habitat, melting ice for the electrolyser, distilling water for human consumption and (heaven forbid) distilling water before electrolysis, should that be necessary.

The point of using thermal to assist electrolysis specifically is because it doesn’t  conribute 1:1, as temp rises it goes 1:1+. It increases efficiency. The other applications I spoke of are process coupled to electrolysis. With the SS turnkey props plant loadout I speculated about 1-2 pages back, they would be physically collocated. If you’ve worked with plumbing you’ll appreciate how much physical simplicity help long term.

After electrolysis, if there’s enough heat still available for distillation it might make sense. The heat would be right there for the taking and if you start transporting it too far losses start adding up. If there is a process that gains efficiency with temp that should of course have priority, especially if collocated.

Phil
Since the reactors are not making that much electrical power, you might consider converting one to a pure heat source.  Then you could run things as hot as you like. If the energy you gain is more than the electricity required for electrolysis then it's a win.
But as others say, the best use for the low grade heat is probably just melting water.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/21/2019 12:27 pm
Contuinued

I'm dying here. It keeps eating my work, so real quick -

If the efficiency increase is linear with with temp increase, and the water entering the cooling jacket is 0C (I know, this would crack the Stirling) the .03% increase of efficiency with each degree of temp rise yealds 6% if the coolant leave the Stirling at 200C and 12% if it leaves at 400C. What would the exit temp actually be?

Heat is needed to melt the water ore and for final distillation. Electrically powered centrifugal separation (no filters needed) would precede distillation. Given that Stirling cooling sets a hard number for flow rate, is there a magic proportioning between electrolysis, melting and distilling that maximizes the use of thermal energy instead of electric? Energy is so dear on Mars that it seems any efficiency should be embraced if practical.

Or does this all go to the NSF dust bin. (Back of hand to forehead, a tear on cheek, a gentle sniff)

Phil
You will find joined here a spreadsheet showing an approximation of the kilopower thermal cycle.  First column of the Stirling tab.  It's probably a bit off because It was originally designed for a Brayton gas cycle.
So unfortunately you cannot have access to that nice high heat.  Because the Stirling engine is actually extracting a lot more than 25%, it's extracting something like 75%, but it immediately returns most of it to the compression part of the cycle to run the compressor piston as mechanical energy.  Expansion cools the gas, compression reheats the gas.  So the cooling stream through the radiator is a lot cooler than you would expect at first, just using the 25% to electricity value.  About 100C average.  Plus the surface temperature of the radiator is lower than the coolant temperature because the convective heat transfer between a gas in the cooling circuit and a surface is not all that good.  Heat pipes are tricky so that value may be off but probably not by more than 50C.

That is really depressing. But if that's where the number go, so be it. Now I'd just like to understand it.

My software is stone age and can't work with xlsx, so I can't pick through your spreadsheet to see what's going on. Can look at it on my phone that's not all that satisfying.

How much difference would it make if the secondary cooling system, from heat pipes to radiator, were stripped away and replaced with a water jacket with 0C input? A low flow rate would give higher temp at the cost of Stirling efficiency and might only be needed intermittently. This would be a compromise with your idea of a thermal only reactor.

Quote: "Because the Stirling engine is actually extracting a lot more than 25%, it's extracting something like 75%, but it immediately returns most of it to the compression part of the cycle to run the compressor piston as mechanical energy.  Expansion cools the gas, compression reheats the gas."

My background is more hands on than working from formal theory but ISTM that this is a net wash. When you back off the throttle in your car and you feel what is commonly called 'compression breaking' it really isn't. What the piston taketh away on compression, it givith back on the power stroke - fuel or no fuel. The breaking comes from the intake stroke struggling against closed throttle plate and pulling 'vacuum'. In a diesel, with a fully open intake, there is no breaking action from backing off the throttle. The blap blap you might hear from a big truck slowing down comes from the jake breaks. This is a mechanism independent of the cam that opens the exhaust valve at the top of the compression stroke, releasing the compressed air so it can not contribute to the oncoming downstroke.

Sorry to be so truculent on this but I feel like my joules are being ripped of - so to speak. Grumble, grumble.

Phil

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/21/2019 12:53 pm
Contuinued

I'm dying here. It keeps eating my work, so real quick -

If the efficiency increase is linear with with temp increase, and the water entering the cooling jacket is 0C (I know, this would crack the Stirling) the .03% increase of efficiency with each degree of temp rise yealds 6% if the coolant leave the Stirling at 200C and 12% if it leaves at 400C. What would the exit temp actually be?

Heat is needed to melt the water ore and for final distillation. Electrically powered centrifugal separation (no filters needed) would precede distillation. Given that Stirling cooling sets a hard number for flow rate, is there a magic proportioning between electrolysis, melting and distilling that maximizes the use of thermal energy instead of electric? Energy is so dear on Mars that it seems any efficiency should be embraced if practical.

Or does this all go to the NSF dust bin. (Back of hand to forehead, a tear on cheek, a gentle sniff)

Phil
You will find joined here a spreadsheet showing an approximation of the kilopower thermal cycle.  First column of the Stirling tab.  It's probably a bit off because It was originally designed for a Brayton gas cycle.
So unfortunately you cannot have access to that nice high heat.  Because the Stirling engine is actually extracting a lot more than 25%, it's extracting something like 75%, but it immediately returns most of it to the compression part of the cycle to run the compressor piston as mechanical energy.  Expansion cools the gas, compression reheats the gas.  So the cooling stream through the radiator is a lot cooler than you would expect at first, just using the 25% to electricity value.  About 100C average.  Plus the surface temperature of the radiator is lower than the coolant temperature because the convective heat transfer between a gas in the cooling circuit and a surface is not all that good.  Heat pipes are tricky so that value may be off but probably not by more than 50C.

That is really depressing. But if that's where the number go, so be it. Now I'd just like to understand it.

My software is stone age and can't work with xlsx, so I can't pick through your spreadsheet to see what's going on. Can look at it on my phone that's not all that satisfying.

How much difference would it make if the secondary cooling system, from heat pipes to radiator, were stripped away and replaced with a water jacket with 0C input? A low flow rate would give higher temp at the cost of Stirling efficiency and might only be needed intermittently. This would be a compromise with your idea of a thermal only reactor.

Quote: "Because the Stirling engine is actually extracting a lot more than 25%, it's extracting something like 75%, but it immediately returns most of it to the compression part of the cycle to run the compressor piston as mechanical energy.  Expansion cools the gas, compression reheats the gas."

My background is more hands on than working from formal theory but ISTM that this is a net wash. When you back off the throttle in your car and you feel what is commonly called 'compression breaking' it really isn't. What the piston taketh away on compression, it givith back on the power stroke - fuel or no fuel. The breaking comes from the intake stroke struggling against closed throttle plate and pulling 'vacuum'. In a diesel, with a fully open intake, there is no breaking action from backing off the throttle. The blap blap you might hear from a big truck slowing down comes from the jake breaks. This is a mechanism independent of the cam that opens the exhaust valve at the top of the compression stroke, releasing the compressed air so it can not contribute to the oncoming downstroke.

Sorry to be so truculent on this but I feel like my joules are being ripped of - so to speak. Grumble, grumble.

Phil
There's a reason it's often caller waste heat :-)
The diesel cycle, by mr. Otto.  I think you need to look at the compression part, before the explosion, that requires work that is done along the crankshaft, but is not visible to the 'outside' of the system.  So there is internal braking, just like what I am describing.  The energy is added by the explosion, and removed by the PTO.  An unloaded engine needs to throttle way down, and reduce the compression work done, to stay stable.
A diesel is actually quite efficient, 40+%.  Much more efficient than kilopower.
Unfortunately, you need to remove the heat just when the system is at its coldest, before compression.  You cannot remove the heat after compression.  If you do, then your coolant returns cooler to the reactor, and the expansion part of the cycle will have less energy available.

.xls 97-2003 version joined.  Hope it works.  The spreadsheet needs some manual input, so tricky to use.  You need to match the electrical efficiency to the compression efficiency by hand.  Sorry.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 06/21/2019 03:32 pm
I don't think there  will be any problem in using waste heat. It can be used for heating the habitat, melting ice for the electrolyser, distilling water for human consumption and (heaven forbid) distilling water before electrolysis, should that be necessary.

The point of using thermal to assist electrolysis specifically is because it doesn’t  conribute 1:1, as temp rises it goes 1:1+. It increases efficiency. The other applications I spoke of are process coupled to electrolysis. With the SS turnkey props plant loadout I speculated about 1-2 pages back, they would be physically collocated. If you’ve worked with plumbing you’ll appreciate how much physical simplicity help long term.

After electrolysis, if there’s enough heat still available for distillation it might make sense. The heat would be right there for the taking and if you start transporting it too far losses start adding up. If there is a process that gains efficiency with temp that should of course have priority, especially if collocated.

Phil
The point I was making was that it might be necessary to distil the water before it is electrolysed. Hopefully this will not be required (except for drinking water) but we don't know for sure how pure the ice will be. It might well be contaminated by salt and silt to some extent. Glaciers tend to form cracks and dust containing perchlorates could easily enter.

If the water is contaminated by salts especially chlorinated salts then there is a danger that some chlorine would contaminate the oxygen side of the electrolysis.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/21/2019 05:52 pm
I don't think there  will be any problem in using waste heat. It can be used for heating the habitat, melting ice for the electrolyser, distilling water for human consumption and (heaven forbid) distilling water before electrolysis, should that be necessary.

The point of using thermal to assist electrolysis specifically is because it doesn’t  conribute 1:1, as temp rises it goes 1:1+. It increases efficiency. The other applications I spoke of are process coupled to electrolysis. With the SS turnkey props plant loadout I speculated about 1-2 pages back, they would be physically collocated. If you’ve worked with plumbing you’ll appreciate how much physical simplicity help long term.

After electrolysis, if there’s enough heat still available for distillation it might make sense. The heat would be right there for the taking and if you start transporting it too far losses start adding up. If there is a process that gains efficiency with temp that should of course have priority, especially if collocated.

Phil
The point I was making was that it might be necessary to distil the water before it is electrolysed. Hopefully this will not be required (except for drinking water) but we don't know for sure how pure the ice will be. It might well be contaminated by salt and silt to some extent. Glaciers tend to form cracks and dust containing perchlorates could easily enter.

If the water is contaminated by salts especially chlorinated salts then there is a danger that some chlorine would contaminate the oxygen side of the electrolysis.


Gotcha. Bit of seed stock needed.  OTOH I caught a paper showing efficiency improvements in electrolysis when an electrolyte is added. I’ll link it when I get back to a ‘puter.  Chlorine by itself probably wouldn’t be much help.


Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/21/2019 07:06 pm
That is really depressing. But if that's where the number go, so be it. Now I'd just like to understand it.

My software is stone age and can't work with xlsx, so I can't pick through your spreadsheet to see what's going on. Can look at it on my phone that's not all that satisfying.

How much difference would it make if the secondary cooling system, from heat pipes to radiator, were stripped away and replaced with a water jacket with 0C input? A low flow rate would give higher temp at the cost of Stirling efficiency and might only be needed intermittently. This would be a compromise with your idea of a thermal only reactor.

Quote: "Because the Stirling engine is actually extracting a lot more than 25%, it's extracting something like 75%, but it immediately returns most of it to the compression part of the cycle to run the compressor piston as mechanical energy.  Expansion cools the gas, compression reheats the gas."

My background is more hands on than working from formal theory but ISTM that this is a net wash. When you back off the throttle in your car and you feel what is commonly called 'compression breaking' it really isn't. What the piston taketh away on compression, it givith back on the power stroke - fuel or no fuel. The breaking comes from the intake stroke struggling against closed throttle plate and pulling 'vacuum'. In a diesel, with a fully open intake, there is no breaking action from backing off the throttle. The blap blap you might hear from a big truck slowing down comes from the jake breaks. This is a mechanism independent of the cam that opens the exhaust valve at the top of the compression stroke, releasing the compressed air so it can not contribute to the oncoming downstroke.

Sorry to be so truculent on this but I feel like my joules are being ripped of - so to speak. Grumble, grumble.

Phil
There's a reason it's often caller waste heat :-)
The diesel cycle, by mr. Otto.  I think you need to look at the compression part, before the explosion, that requires work that is done along the crankshaft, but is not visible to the 'outside' of the system.  So there is internal braking, just like what I am describing.  The energy is added by the explosion, and removed by the PTO.  An unloaded engine needs to throttle way down, and reduce the compression work done, to stay stable.
A diesel is actually quite efficient, 40+%.  Much more efficient than kilopower.
Unfortunately, you need to remove the heat just when the system is at its coldest, before compression.  You cannot remove the heat after compression.  If you do, then your coolant returns cooler to the reactor, and the expansion part of the cycle will have less energy available.

.xls 97-2003 version joined.  Hope it works.  The spreadsheet needs some manual input, so tricky to use.  You need to match the electrical efficiency to the compression efficiency by hand.  Sorry.

Thank you for the antique format. I really plan on moving onto linux at some point.

As for the behavior of a diesel piston I must say, Au contrair, mon capitan!

Picture a piston and cylinder with a blank head, no valves, no spark plug and no injector. Include rings with zero leakage. While we're at it put it at BDC pressurized to one atmosphere with the bottom of the piston exposed to one atmosphere of effectively infinite volume. This last is so there is no variation on the piston underside pressure throughout the cycle.

Turn the crank one half turn to TDC. The air will be compressed and grow hot. Turn the crank the tiniest smidge further past TDC and the cylinder will spring down with the same amount of force required to get it to TDC in the first place. And it will cool. There will be mechanical friction skewing the number. The compression will be exothermic and the rebound will be endothermic to the same degree. Endo and exothermic are probably not the correct terms but I think they get the idea across.

Add in the valves and injector, fuel and the combustion process, and this doesn't change. See: https://en.wikipedia.org/wiki/Compression_release_engine_brake (https://en.wikipedia.org/wiki/Compression_release_engine_brake) for an explanation of Jake brakes, who's sole purpose in the universe is to overcome this air spring rebound when braking.

The waste heat in the diesel cycle comes from a variety of source - some of which I may not be aware of.
1) The engine itself get hot and the cooling system draws this heat away. This energy is not available for work.
2) If unrestrained by the crank and with a cylinder arbitrarily long, the piston would travel quite a long ways. The length of the crank throw limits the linear travel of the piston well before this point setting up the hot gasses for expulsion while they still have the potential for more work.
3) Internal friction and ring blowby.

I don't grok Stirlings as well as Otto or Diesel so while I'm sure all three of these will affect them to some extent, I have no feel for the actual impact in the real world.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/21/2019 07:53 pm
I don't think there  will be any problem in using waste heat. It can be used for heating the habitat, melting ice for the electrolyser, distilling water for human consumption and (heaven forbid) distilling water before electrolysis, should that be necessary.

The point of using thermal to assist electrolysis specifically is because it doesn’t  conribute 1:1, as temp rises it goes 1:1+. It increases efficiency. The other applications I spoke of are process coupled to electrolysis. With the SS turnkey props plant loadout I speculated about 1-2 pages back, they would be physically collocated. If you’ve worked with plumbing you’ll appreciate how much physical simplicity help long term.

After electrolysis, if there’s enough heat still available for distillation it might make sense. The heat would be right there for the taking and if you start transporting it too far losses start adding up. If there is a process that gains efficiency with temp that should of course have priority, especially if collocated.

Phil
The point I was making was that it might be necessary to distil the water before it is electrolysed. Hopefully this will not be required (except for drinking water) but we don't know for sure how pure the ice will be. It might well be contaminated by salt and silt to some extent. Glaciers tend to form cracks and dust containing perchlorates could easily enter.

If the water is contaminated by salts especially chlorinated salts then there is a danger that some chlorine would contaminate the oxygen side of the electrolysis.


Gotcha. Bit of seed stock needed.  OTOH I caught a paper showing efficiency improvements in electrolysis when an electrolyte is added. I’ll link it when I get back to a ‘puter.  Chlorine by itself probably wouldn’t be much help.


Phil

Here's a short 5 pager https://ijettjournal.org/volume-7/number-1/IJETT-V7P217.pdf (https://ijettjournal.org/volume-7/number-1/IJETT-V7P217.pdf)

Quote:
CONCLUSIONS
... The mass flow of hydrogen increases with increasing the  temperature and concentration of electrolyte...
... the resistance decreases with increasing concentration and temperature of electrolyte at different currents studied...

It only looks at a max of 60C.

Alas, it's looking like there may not be all that much thermal available with a kilopower. I've been told this by those who presumable know better than I, but there is that 'defering to authority' thing that makes me want to build my own model. There is the minor issue of not understanding thermodynamics, but why should I let that stand in my way. 8)

Phil
 
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 06/21/2019 08:24 pm
A second, clearly inconsequential matter that you will surely easily overcome is the getting the necessary U-235 and getting  permission to use the Department of Energy's National Nuclear Security Administration (NNSA) site in Nevada!
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/21/2019 10:31 pm
A second, clearly inconsequential matter that you will surely easily overcome is the getting the necessary U-235 and getting  permission to use the Department of Energy's National Nuclear Security Administration (NNSA) site in Nevada!

Check out: https://forum.nasaspaceflight.com/index.php?topic=48324.msg1958180#msg1958180 (https://forum.nasaspaceflight.com/index.php?topic=48324.msg1958180#msg1958180)

Bad clip. Not the message. Read the thread. Discussion on early base organization & economics. I started off thinking ‘let NASA pound sand’. Got converted over to working with NASA. Just don’t let them take over.

They’re real proud of kilopower. It’s been done fast & cheap. If Elon can’t negotiate some kilopower as the part of cost of of getting in the game I would be more dumbfounded than if I saw a water tower hop.

Phil
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 06/21/2019 11:50 pm
I followed the news about Kilopower, the first new type of reactor in decades, in detail, with great interest. I agree NASA should provide some to the SpaceX Mars effort, and believe they will. Sorry about the tongue in cheek - I couldn't help myself. After the effort NASA had to go through to test their design and finally do the tests of the live working version at the NNSA site, you seemed to dismiss all this with "build my own model". However you may well eventually be proved right. If NASA mass produces Kilopower, engineers (like you?) may well ask for variations or be more closely involved with adaptions or redesign.... And modifying the heat removal from the cold end of the Stirling engine to warm a rodwell etc. isn't nuclear physics... just plumbing!
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/22/2019 12:25 am
I followed the news about Kilopower, the first new type of reactor in decades, in detail, with great interest. I agree NASA should provide some to the SpaceX Mars effort, and believe they will. Sorry about the tongue in cheek - I couldn't help myself. After the effort NASA had to go through to test their design and finally do the tests of the live working version at the NNSA site, you seemed to dismiss all this with "build my own model". However you may well eventually be proved right. If NASA mass produces Kilopower, engineers (like you?) may well ask for variations or be more closely involved with adaptions or redesign.... And modifying the heat removal from the cold end of the Stirling engine to warm a rodwell etc. isn't nuclear physics... just plumbingheak!

No problem wih tongue in cheek. I was going to respond with: stop by my local neighborhood reactor and borrow a couple cups, but I held myself in check. Dangit.

I figure if you’re carefully modifying the cold end of the stirling you wouldn’t disturbe the exquisite self regulation of the reactor itself. I might also be full of bs.

Nowhere near being an engineer but I did have Lionel when I was a kid.

Phil
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 06/22/2019 02:02 am
The problem with Kilopower is they're expensive and heavy. On the order of 4W/kg and $150 million per reactor (source: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf ). To provide the roughly 500kW average power needed to produce enough fuel for a Starship to return, then, it'd cost $7.5 billion and weigh 125 tons for the reactor equipment alone.

Solar should be a little lighter and a LOT cheaper.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 06/22/2019 02:04 am
the first new type of reactor in decades,

And this is why I think solar/battery will dominate. Nuclear isn't advancing generally; while there are proposals, in practice the industry has been in a rut for decades. With solar, I've seen god knows how many generations of technology over my lifetime, with a ~300x drop in costs (panel-only), halving every 5-6 years. Battery technology has seen similar improvements, with storage density doubling roughly every 8 years.

That non-space market is paying for the development, year after year of PV/Battery. But with nuclear, space applications will have to pay the entire cost of development, and the largest markets in space don't need and don't use nuclear power, so we are limited to non-commercial space agency funding. That means you only get one major development every 20-30yrs or so, and so everything rides on you picking the right design and it working out as hoped. (With normal technological development, you have dozens of competing ideas being thrown together to see what actually works best. With nuclear, you are trying to pick a winner before you start development.)
Title: Re: Power options for a Mars settlement
Post by: RonM on 06/22/2019 03:44 am
I think having one Kilopower during the early days of a Mars base would be a good idea. Something to keep the lights on and ECLSS running if everything else fails. The first crewed synod will be the most dangerous. Once ISRU is running at full capacity, later missions can bring less expensive backup systems.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 06/22/2019 11:55 am
I followed the news about Kilopower, the first new type of reactor in decades, in detail, with great interest. I agree NASA should provide some to the SpaceX Mars effort, and believe they will. Sorry about the tongue in cheek - I couldn't help myself. After the effort NASA had to go through to test their design and finally do the tests of the live working version at the NNSA site, you seemed to dismiss all this with "build my own model". However you may well eventually be proved right. If NASA mass produces Kilopower, engineers (like you?) may well ask for variations or be more closely involved with adaptions or redesign.... And modifying the heat removal from the cold end of the Stirling engine to warm a rodwell etc. isn't nuclear physics... just plumbing!

It is reasonably arguable that you can replace the electricity from a 10kW Kilopower unit with two tons total of solar power + batteries - commercially available for well under $50K. You need some more to deal with contingencies.
Even if Kilopower was provided to SpaceX actually free, with its ride paid by NASA, it may not be useful for SpaceX as a reliable power source.

This is because the device reliability is only a small part of the likelyhood of it working on Mars. You have to include the political and social risk of the various levels of NASA, administration and public opinion deciding not to fly the reactor or delaying it.
In addition, it doesn't really help with the ~1MW average you need to do manufacturing of propellant - it is implausible to imagine a hundred Kilopower units.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 06/22/2019 03:42 pm
the first new type of reactor in decades,

And this is why I think solar/battery will dominate. Nuclear isn't advancing generally; while there are proposals, in practice the industry has been in a rut for decades. With solar, I've seen god knows how many generations of technology over my lifetime, with a ~300x drop in costs (panel-only), halving every 5-6 years. Battery technology has seen similar improvements, with storage density doubling roughly every 8 years.

That non-space market is paying for the development, year after year of PV/Battery. But with nuclear, space applications will have to pay the entire cost of development, and the largest markets in space don't need and don't use nuclear power, so we are limited to non-commercial space agency funding. That means you only get one major development every 20-30yrs or so, and so everything rides on you picking the right design and it working out as hoped. (With normal technological development, you have dozens of competing ideas being thrown together to see what actually works best. With nuclear, you are trying to pick a winner before you start development.)

And that's why bases north of 40 degrees latitude where there's abundant near surface water ice won't happen before nukes are available.  The long winter has days that are just too short for solar production, return propellant and base operational electrical power.  Throw in a dust storm or so and really short on solar insolation north of the 30s.
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 06/22/2019 04:51 pm
The problem with Kilopower is they're expensive and heavy. On the order of 4W/kg and $150 million per reactor (source: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf ). To provide the roughly 500kW average power needed to produce enough fuel for a Starship to return, then, it'd cost $7.5 billion and weigh 125 tons for the reactor equipment alone.

Solar should be a little lighter and a LOT cheaper.
Some serious differences in estimates there. The guy giving the Krusty presentation in Pasadena thought $5 million each plus fuel for the 1KWe was a reasonable goal if they went into regular production. A big difference from occasional, single orders.
 I couldn't get him to day exactly what "fuel" meant. Anything from raw, enriched uranium to a finished core with the reflector was possible I guess.
 He speculated around 500kg for a 10KWe model, and guessed close to 40 tonnes for a 2MWe system.
Title: Re: Power options for a Mars settlement
Post by: raketa on 06/22/2019 07:19 pm
I will be not surprise Spacex is working on their cheaper alternative of  kilopower.
They mention  nuclear several times with Mars base development.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/22/2019 07:46 pm
In addition, it doesn't really help with the ~1MW average you need to do manufacturing of propellant - it is implausible to imagine a hundred Kilopower units.
The Kilopower team has a growth plan from 1Kw (probe) to 10Kw (probe and propulsion) to 100Kw.

I'm not sure if there is a projected 1MW unit design, but the core system has quite a lot of stretch.
Title: Re: Power options for a Mars settlement
Post by: joek on 06/22/2019 09:08 pm
Work on scaling KiloPower to MWe appears to be mostly focused on terrestrial applications.  DOE has awarded a number of contracts in the last few years, at least one appears to be based on KiloPower technology (Westinghouse eVinci).

Attached is an ancient (2013) presentation and excerpt of slide 48 which shows 2 MWe MegaPower reactor.

Unclear what would be needed to adapt this for Mars operation and transport.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 06/22/2019 09:12 pm
I will be not surprise Spacex is working on their cheaper alternative of  kilopower.
That almost does not fix the problems I raised above.
If you are developing your own nuclear reactor, you now have to get approval to develop a nuclear reactor, and all of the proliferation, regulatory and other concerns.
This is expensive.
Worse concerns arise if you are relying on launching this, because you now have the schedule issue on if you in fact get it working adding to the political questions about if you will be permitted to launch it.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/22/2019 10:31 pm
The problem with Kilopower is they're expensive and heavy. On the order of 4W/kg and $150 million per reactor (source: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf) ). To provide the roughly 500kW average power needed to produce enough fuel for a Starship to return, then, it'd cost $7.5 billion and weigh 125 tons for the reactor equipment alone.

Solar should be a little lighter and a LOT cheaper.

Please don't misunderstand. I'm advocating one kilopower for a self contained prop plant for thermal input to electrolysis that will improve efficiency and reduce power consumption, with remaining heat applied to other related processes as available. Alas, it appears that waste heat will not be available at a temperature that will be useful but I'm not fully convinced. I think in my original post I recognized the a 10kW kilopower would not have the power to carry prop production without significant PV.

It would be my expectation that NASA would supply kilopower on their dime as part of the cost of participation.  From a regulatory standpoint this would make nuke easier.

There is also the issue of not having all the power eggs in one basket. Strong opinions have solidified and it's been beat to death so let's not go there.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/22/2019 10:56 pm
the first new type of reactor in decades,

And this is why I think solar/battery will dominate. Nuclear isn't advancing generally; while there are proposals, in practice the industry has been in a rut for decades. With solar, I've seen god knows how many generations of technology over my lifetime, with a ~300x drop in costs (panel-only), halving every 5-6 years. Battery technology has seen similar improvements, with storage density doubling roughly every 8 years.

That non-space market is paying for the development, year after year of PV/Battery. But with nuclear, space applications will have to pay the entire cost of development, and the largest markets in space don't need and don't use nuclear power, so we are limited to non-commercial space agency funding. That means you only get one major development every 20-30yrs or so, and so everything rides on you picking the right design and it working out as hoped. (With normal technological development, you have dozens of competing ideas being thrown together to see what actually works best. With nuclear, you are trying to pick a winner before you start development.)

You might want to google kilopower. It is admittedly not yet in production but a prototype unit has been fired up and hammered with failure modes seven way from sunday. The low cost and rapidity of design was much more SX like than NASA like. On it's public face NASA is excited about it because is appears highly self regulating (runaway seems impossible short of armor piercing rounds) and is, by the standards of nuke power, inexpensive, light and small. And it seems to fit the bill for the distant exploration that NASA is interested in.

Mars or not, NASA gives every appearance of intent to continue developing it. If development continues at the rate it did up until the prototype testing, I would not be surprised to see a pre production model late this year or sometime next year.

All this is no claim that kilopower will dominate on Mars. Far from it. PV and batteries will do the heavy lifting. And if, for some reason it doesn't pan out, it won't go. I've seen some statements that SX has moved everything back two years but haven't seen anything from Elon's mouth. If this is true there is plenty of time to see if kilopower actually works out.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 06/22/2019 11:09 pm
The problem with Kilopower is they're expensive and heavy. On the order of 4W/kg and $150 million per reactor (source: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf) ). To provide the roughly 500kW average power needed to produce enough fuel for a Starship to return, then, it'd cost $7.5 billion and weigh 125 tons for the reactor equipment alone.

Solar should be a little lighter and a LOT cheaper.
Some serious differences in estimates there. The guy giving the Krusty presentation in Pasadena thought $5 million each plus fuel for the 1KWe was a reasonable goal if they went into regular production. A big difference from occasional, single orders.
 I couldn't get him to day exactly what "fuel" meant. Anything from raw, enriched uranium to a finished core with the reflector was possible I guess.
 He speculated around 500kg for a 10KWe model, and guessed close to 40 tonnes for a 2MWe system.

Namadd, When was the Pasadena presentation? Current numbers? Is there a transcript anywhere? The link in the post you're responding to was from 2013. I tend to like newer numbers, especially post prototype numbers.

Phil
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 06/23/2019 12:36 am
the first new type of reactor in decades,
And this is why I think solar/battery will dominate. Nuclear isn't advancing generally; while there are proposals, in practice the industry has been in a rut for decades. With solar, I've seen god knows how many generations of technology over my lifetime, with a ~300x drop in costs (panel-only), halving every 5-6 years. [...]
You might want to google kilopower. It is admittedly not yet in production

You've missed my point. By the time Kilopower is ready for in-space use, by the time it does what the designers hope, solar will have dropped in cost by half or three-quarters, with similar improvements in mass/watt and potential ISRU manufacture. Batteries will have doubled their energy density (although not by mass) and lifespan over the same period.

And if Kilopower doesn't work out, or doesn't scale as hoped, as other nuclear technologies (like pebble-bed) have failed to work out as advertised (in spite of having "been fired up and hammered with failure modes seven way from sunday"), then progress is zero for that whole generation of research. Progress in solar doesn't depend on one specific new development working, industrialising, scaling as advertised.

That is a difference in kind between the technologies.

there is plenty of time to see if kilopower actually works out.

And if it doesn't, you have nothing. Which means you can't count on it. Whereas you can predict a decade out where solar and battery tech will be, even if you don't know or care how it will get there.

That's the difference.



And that's why bases north of 40 degrees latitude where there's abundant near surface water ice won't happen before nukes are available.  The long winter has days that are just too short for solar production, return propellant and base operational electrical power.  Throw in a dust storm or so and really short on solar insolation north of the 30s.

No. Solar works better at higher latitudes on Mars than it does on Earth. [edit: Except for the increase in solar distance.] And it is certainly viable in the 40s on Earth. The reason is that same dust. Because modern PV cells can work with indirect light, the sunlight reflected off of dust in the atmosphere is perfectly usable. Amongst other things, that extends the effective length of the day. The rest is just adding more PV, more batteries (or other energy storage systems), and matching industrial demand to solar flux. It takes a lot before nuclear power is competitive with solar PV, and solar gets better every year.

I keep hoping there'll be a big breakthrough in nuclear -- it should be better -- but decade after decade, the industry fails to improve.
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 06/23/2019 05:39 am
The problem with Kilopower is they're expensive and heavy. On the order of 4W/kg and $150 million per reactor (source: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011723.pdf) ). To provide the roughly 500kW average power needed to produce enough fuel for a Starship to return, then, it'd cost $7.5 billion and weigh 125 tons for the reactor equipment alone.

Solar should be a little lighter and a LOT cheaper.
Some serious differences in estimates there. The guy giving the Krusty presentation in Pasadena thought $5 million each plus fuel for the 1KWe was a reasonable goal if they went into regular production. A big difference from occasional, single orders.
 I couldn't get him to day exactly what "fuel" meant. Anything from raw, enriched uranium to a finished core with the reflector was possible I guess.
 He speculated around 500kg for a 10KWe model, and guessed close to 40 tonnes for a 2MWe system.

Namadd, When was the Pasadena presentation? Current numbers? Is there a transcript anywhere? The link in the post you're responding to was from 2013. I tend to like newer numbers, especially post prototype numbers.

Phil
It was from the Mars society convention last year. Mostly from a personal conversation after the presentation. There are transcripts of the presentation somewhere in nsf. Hard to find on a phone in a San Antonio pub.
Title: Re: Power options for a Mars settlement
Post by: Jcc on 06/23/2019 12:58 pm
I certainly think the best solution is both nuclear and solar, even though neither source by itself could produce enough power to refuel a ship for next synod return in addition to keeping the crew alive and support building  the base. The more of both they have the better. If you have more solar power than could be stored in available batteries, then do extra electrolysis when the sun shines and store that in hydrogen and oxygen.

Ultimately, the contingency for not being able to refuel a ship for next synod return is to do it for a synod later return. Just need enough food and supplies.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/13/2019 03:03 am
This may have been discussed already, sorry if this is so.

For wind:
P = ½*n*p*As*v3 , where n is turbine efficiency, p is atmospheric density (kg/m3), As is swept area of the turbine (m2), and v is wind speed (m/s). The maximum efficiency is 16/27 (60%) as given by Betz’ law. On Mars, for a small 10m diameter turbine As=78m2, an efficiency of 31% , air density of 0,02 kg/m3 and a wind speed of 10 m/s, P= 487W.

For the above parameters a typical large wind turbines on Earth produces 12W/kg, where the mass includes blades, generator and tower. This is less than the 33 W/kg that can be reached by solar on Mars, but the availability may be higher. In particular, during dust storms on Mars the available solar power is very low but the average air speed is higher. As the power is to the cube of the air speed, the average wind power per kg would then be about equal to the sun power per kg, making the two forms of energy complementary. So a martian settlement might want to have a mix of solar and wind to increase its diversity of power sources.

For the same size of turbine, as the air on Earth is 50 times more dense, the same turbine will produce 50 times more power. However, the martian wind turbine could be built much lighter as it handles much less power, and possible have similar overall efficiencies and power/mass ratios.

My real question is does anyone know if the efficiencies that could be achieved are similar to those of Earth turbines?  Don't see why not, but have no proof that this is so either.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 07/13/2019 09:02 am
The small propellor drone of NASAs next Mars rover will do a lot in terms of proof of concept for Mars wind power.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/13/2019 12:40 pm
The small propellor drone of NASAs next Mars rover will do a lot in terms of proof of concept for Mars wind power.

How?
The mechanics of a small prop going at ~0.5* the speed of sound are almost irrelevant to a large slow wind turbine.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 07/13/2019 01:35 pm
Proof of concept is great for wind power. You would think we know how to build proper wheels. Yet curiosities wheels are chewed up on mars. You would think we know how to build solar panels and know how long it takes for them to dust over. Yet Opportunities solar panels stayed much cleaner than expected due to wind induced 'cleaning events'.
We think we know everything until we realise we don't. It's good to do proof of concept stuff. And even if its only to confirm that bearings work in the Martian dust the same as on earth for instance.
Title: Re: Power options for a Mars settlement
Post by: RonM on 07/13/2019 04:44 pm
In the USA we use wind power in places like Texas and the Midwest because the is wind blowing most of the time. Where I live in the Southeast most days are calm. We only get wind when a front moves through. So, we don't have wind farms around here. How regular are winds on Mars? There should be weather data from landers and rovers.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/13/2019 05:56 pm
In the USA we use wind power in places like Texas and the Midwest because the is wind blowing most of the time. Where I live in the Southeast most days are calm. We only get wind when a front moves through. So, we don't have wind farms around here. How regular are winds on Mars? There should be weather data from landers and rovers.
Yes there is data. 
Tha NASA mars fact sheet, for example: https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

Wind speeds:  2-7 m/s (summer), 5-10 m/s (fall), 17-30 m/s (dust storm) (Viking Lander sites)

Due to ground effects, we should expect the air higher up to move a little faster.  So there seems to b power available there.  I wonder what the turbine blades might look like though.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/13/2019 06:15 pm
Is there an intermediate DC voltage?  Something in the range of 20 kV DC technology?

As solar cells are DC, and rectifiers are available that can create more or less any voltage out of a set of power sources, and more and more lighting is LED (DC) might there be a point in going all DC?

And the large amounts of energy required for propellant production might use DC as well?

Illustrated is a Tesla power system, with added cooling in the back to take the low atmospheric density into account.  Each battery module is 50 kWh, and the central unit is 400A at 480V or about 200 kW.  Five of these combined with a lot of panels and you have a 1 MW power source, that's about right for Starship propellant production.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/13/2019 08:47 pm
A 120-300 kW wind turbine, 42m blade, chord tripled to account for the lower air density.
This would have about 1/3 of the energy to mass ratio of solar, but might come in useful during storms if nuclear doesn't arrive on time.  And as the winds are higher during storms the power increases to close to solar.
The tower could be 1mm steel, with  internal pressure and could mass as little as 2-3 tonnes, for example.
Title: Re: Power options for a Mars settlement
Post by: Semmel on 07/13/2019 09:10 pm
Lamontage, is erosion from dust in the atmosphere an issue for the rotor blades?
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/13/2019 09:48 pm

SNIP

This would, at first glance, be an undersized load for an SS in both mass and volume (I think). Given that, as mentioned in an earlier post that I can not pinpoint, max electrode degradation occurs during startup, it makes sense to keep electrolysis running constantly. This implies H2, O2 and water storage. Oversized the sabitire and run it only during the day when PV is available with stored and concurrently produced H2. Sabiter is exothermic and can run with minimal power but blowing in the CO2 and the product liquification is power hungry.

SNIP


Sorry I didn't see this sooner.  My attention has been focused elsewhere and I haven't been keeping up on this thread.

Sabatier reactor catalyst degradation is a major concern if you want to have daily start-stop operations.  In order to keep maintenance cycles reasonable you'll want to go with ruthenium everywhere.  Producing or recycling high purity ruthenium isn't easy, even here on Earth.  This restriction means the Mars base will be reliant on Earth for the foreseeable future.

Continuous operation means we avoid the catalyst degradation problem associated with startup.  Instead of needing ruthenium everywhere we can use nickel, except for leading edges.  High purity nickel can be produced using the Mond process, something that can be done relatively easily in an early Mars base.  We're talking about reducing Sabatier catalyst mass import requirements on the order of 10,000.  My opinion is steady state operation is the obvious choice.

Steady state Sabatier reactor operation does require a continuous hydrogen source.  This can be provided by a metal hydride hydrogen buffer.  The metal used can be high purity nickel manufactured by the same equipment that makes nickel Sabatier reactor catalysts.  Metal hydride hydrogen buffers are thermally regulated.  Releasing stored hydrogen involved heating the hydride.  The Sabatier reaction is exothermic, so we can use the heat produced when the reactor is running to release the hydrogen the Sabatier reactor needs to run.

Running continuous electrolysis requires a continuous electricity supply.  A continuous electricity supply is simple enough if we have nuclear power.  If we are limited to solar we are going to need massive banks of batteries.  Electrolysis electrodes need to be some kind of inert metal.  Once again nickel can be good enough, and easy enough to produce at an early Martian base.

I don't get the blowing in CO2 bit.  Nitrogen exasperates hydrogen embrittlement and leads to ammonia creation.  Ammonia creation increases catalyst degradation and requires an additional separation process after the reactor.  What we want to do is to compress the Martian atmosphere, separate the various gases, then store them in tanks.  This can be done separately from operating the Sabatier reactor.  Therefore the energy we need to account for for our CO2 supply is the energy for the control system that opens and closes the values between the CO2 tank an the reactor.

Ammonia is useful in its own right.  We'll almost certainly want a Haber Bosch reactor.  This can be a copy of the Sabatier reactor, also using locally sourced nickel.  Since the ammonia/methane demand ratio will almost certainly not match the nitrogen/CO2 ratio in the Martian atmosphere we do want to plan separate production lines.  Using energy that could be used to produce methane producing an unwanted ammonia surplus makes no sense to me.

For purposes of the recent discussions in this thread what we care about is energy needed by the electrolysis unit and the atmosphere compressor and separator.  The control systems, including coolant pumps, will be insignificant in comparison.  I used to have a wide array of useful papers but those were stored on a hard drive that died a couple months back.  Unfortunately the backs were on optical discs that were thrown out.  While I could spend the time tracking these down again figuring out how to efficiently separate and recirculate unreacted hydrogen and carbon dioxide is the far more pressing challenge.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/13/2019 10:17 pm
Lamontage, is erosion from dust in the atmosphere an issue for the rotor blades?
Well, it's hardly sandblasting velocities and densities.  However, 80 m/s at the wind tips, or 180 miles per hour for a very large turbine on Earth, I expect about the same velocities on Mars.... it's certainly a valid question.  The papers I read weren't particularly concerned.   For a dust devil loading of 7 x 10-5 kg/m3 average (https://pdfs.semanticscholar.org/29f8/4a06395af97a02061bdff74135b7415ed456.pdf)
we might gt 0,07 g/m3 x 80 m/s = 5,3 g/m2/s.  Sandblasting functions at 25 kg/m2 so about that rate per hour....
So yes, unless I missed something, there might be erosion during a storm as dense as a sand devil.

Now, how dense are martian storms?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/13/2019 11:04 pm

What we want to do is to compress the Martian atmosphere, separate the various gases, then store them in tanks.  This can be done separately from operating the Sabatier reactor.  Therefore the energy we need to account for for our CO2 supply is the energy for the control system that opens and closes the values between the CO2 tank an the reactor.

Putting the energy usage into a separate "account" doesn't change the energy requirements at all. The embodied energy is the same.

In fact putting gas in tanks and irreversibly expanding it through valves uses slightly more energy than operating a pump, due to Joule expansion. But this tiny energy inefficiency is overwhelmed by the practical operational advantages.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/13/2019 11:58 pm
As one of the uses for excess solar on Earth will be hydrogen production, there might be a market here to develop a more robust electrode system?
Title: Re: Power options for a Mars settlement
Post by: randomly on 07/14/2019 12:22 am
Hydrogen production from electrolysis is inefficient. From electrical energy in to electrolysis and then electrical energy out from fuel cells it's only about 20% efficient. On earth there will always be better things to use your electric power on than making hydrogen.
The only energy source that might be close to economical to produce hydrogen would be high temperature nuclear reactors, but I don't see that happening any time soon.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/14/2019 12:28 am
Hydrogen production from electrolysis is inefficient. From electrical energy in to electrolysis and then electrical energy out from fuel cells it's only about 20% efficient. On earth there will always be better things to use your electric power on than making hydrogen.
The only energy source that might be close to economical to produce hydrogen would be high temperature nuclear reactors, but I don't see that happening any time soon.
Efficiency doesn't really matter much if you have excess production capacity.  Hydrogen can be injected into natural gas pipelines and used with the natural gas.  But perhaps some of the forms of compressed gas storage are better methods than hydrogen production.  Hydrogen will be produced by solar because eventually it will be difficult to une natural gas.  But not very soon, and that's just one of our many possible futures.
So how effective and low mass are storage methods these days?
Title: Re: Power options for a Mars settlement
Post by: randomly on 07/14/2019 12:42 am
But there are always more economically attractive things to do than make hydrogen. Pumped hydro storage at 70+% round trip efficiency, or smelting aluminum, etc. etc.
Hydrogen production with electricity has a dismal economic return.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/14/2019 12:47 am
But there are always more economically attractive things to do than make hydrogen. Pumped hydro storage at 70+% round trip efficiency, or smelting aluminum, etc. etc.
Hydrogen production with electricity has a dismal economic return.
Not if you're using the hydrogen as hydrogen.  It's actually quite effective.  But as a storage medium to produce electricity i'll certainly agree that it sucks.
Also, if you burn the hydrogen to make heat, for example, then it's pretty effective.
But is industrial electrolysis of hydrogen even a thing?  Steam reformation seems much cheaper.
Title: Re: Power options for a Mars settlement
Post by: randomly on 07/14/2019 01:02 am
I'm only aware of electrolysis hydrogen production on small scales, it doesn't remotely compete with steam reformation of natural gas.
You would still be better off using the electricity directly for heating or cooling.

Bottom line is I just don't see any market in the near future for electrolysis hydrogen, and I'm skeptical we will ever see 'excess' solar power used that way.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/14/2019 01:29 am
I'm only aware of electrolysis hydrogen production on small scales, it doesn't remotely compete with steam reformation of natural gas.
You would still be better off using the electricity directly for heating or cooling.

Bottom line is I just don't see any market in the near future for electrolysis hydrogen, and I'm skeptical we will ever see 'excess' solar power used that way.
Don't really care one way or the other  :-)  But at least Musk is on record that he want to produce his own methane using solar, and that has to go through electrolysis.  What I would like to know if there is significant damage to electrodes in interrupted electrolysis.  What papers I've come across seem to concern mostly short lived experiments, each one proposing a revolutionary electrode magic.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 07/14/2019 01:51 am
I'm only aware of electrolysis hydrogen production on small scales, it doesn't remotely compete with steam reformation of natural gas.
You would still be better off using the electricity directly for heating or cooling.

Bottom line is I just don't see any market in the near future for electrolysis hydrogen, and I'm skeptical we will ever see 'excess' solar power used that way.
Don't really care one way or the other  :-)  But at least Musk is on record that he want to produce his own methane using solar, and that has to go through electrolysis.  What I would like to know if there is significant damage to electrodes in interrupted electrolysis.  What papers I've come across seem to concern mostly short lived experiments, each one proposing a revolutionary electrode magic.
Interrupted electrolysis does not damage electrodes for making hydrogen. It does for making aluminum because of the crazy process of making aluminum.

Large scale hydrogen electrolysis is a thing, it's just not as common as steam reformation. The largest plant is like 10-20MW or so. That'd be enough to provide enough lift capacity equivalent to all of SpaceX's current launch cadence (about 20-25 Falcon cores per year) and fuel up about 37 Starships going from Mars to Earth each synod.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 07/14/2019 01:54 am
A 120-300 kW wind turbine, 42m blade, chord tripled to account for the lower air density.
This would have about 1/3 of the energy to mass ratio of solar, but might come in useful during storms if nuclear doesn't arrive on time.  And as the winds are higher during storms the power increases to close to solar.
The tower could be 1mm steel, with  internal pressure and could mass as little as 2-3 tonnes, for example.
I thinknyou mean power density, not energy density...  And since  it only works when there's wind, you need to de-rate by that fraction (just like you do solar) and then ask yourself what's better - to build a wind tower for relatively rare dark and stormy days, or use the same mass for solar, and use either batteries or generators for dark and stormy days.

Since sunny days are the majority, and since the wind turbine power density already starts out low, I betcha the second solution will prove better.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/14/2019 02:31 am

What we want to do is to compress the Martian atmosphere, separate the various gases, then store them in tanks.  This can be done separately from operating the Sabatier reactor.  Therefore the energy we need to account for for our CO2 supply is the energy for the control system that opens and closes the values between the CO2 tank an the reactor.

Putting the energy usage into a separate "account" doesn't change the energy requirements at all. The embodied energy is the same.

In fact putting gas in tanks and irreversibly expanding it through valves uses slightly more energy than operating a pump, due to Joule expansion. But this tiny energy inefficiency is overwhelmed by the practical operational advantages.

I have no clue why you would think I am claiming the energy requirements change dramatically.  The separate accounts are for the various subsystems the energy use is coupled to.  As I thought I had explained in enough detail this is so we can take advantage of practical operational advantages.
Title: Re: Power options for a Mars settlement
Post by: Pete on 07/14/2019 02:21 pm
A 120-300 kW wind turbine, 42m blade..
The tower could be 1mm steel, with  internal pressure and could mass as little as 2-3 tonnes, for example.

You want to build a wind turbine that stands 110m hub-height, 162m with blades,
WITH the needed electrical bits to make it a generator AND make the whole thing rigid enough with air pressure to handle storm-level torque.
.
.
.
And you expect it will mass only 2-3 tonnes?


I believe you are off by about two MAGNITUDES on that estimate!
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/14/2019 06:01 pm
A 120-300 kW wind turbine, 42m blade..
The tower could be 1mm steel, with  internal pressure and could mass as little as 2-3 tonnes, for example.

You want to build a wind turbine that stands 110m hub-height, 162m with blades,
WITH the needed electrical bits to make it a generator AND make the whole thing rigid enough with air pressure to handle storm-level torque.
.
.
.
And you expect it will mass only 2-3 tonnes?


I believe you are off by about two MAGNITUDES on that estimate!
No, I don't expect that.  I was just wondering how light we might make the tower. And yes, at least one order of magnitude.  Perhaps even 1.5.

An entire 1.5 MW Earth based wind turbine masses about 200 tonnes.  Rotor and hub 32 tonnes, nacelle 60 tonnes and tower 110 tonnes.  According to the papers I referenced in earlier posts, the force on similarly sized tower operating on Mars would be one tenth of the force on an Earth tower, so proportionally is should mass about 20 tonnes.  Since its blades are 3 times as wide, one might guess at an overall mass of 26 tonnes.  To achieve this 1:10 ratio the turbine need to be optimised for a higher velocity than on Earth, 22 m/s rather than 10 m/s.
At these masses we are getting about 9W/kg at nominal design.  Solar is much more mass efficient, at a peak of about 100W/m2 for 3 kg/m2  or 33 W/kg.
An 150 kW generator will be about 1:10 of the mass of a 1.5 MW generator.
Using carbon fiber blades might allow us to keep about the same mass for the rotor and hub, although the walls will get very thin, so perhaps unstable.  A bit of internal pressure might help there.

As for the tower, at 12 tonnes 110m high and about 6m in diameter, or 2200m2 of wall= 5.5 kg/m2.  that's a little bit less than 1mm of steel, or about 2mm of aluminium.   My guess is that somewhere along the line the tower would have the correct theoretical strength, but crumple du to buckling of the thin walls.  Hence the internal pressure suggestion.
My first calculation was for a shorter 60m tower, with a smaller diameter, hence the 3 tonnes.
So perhaps 20 tonnes for the wind turbine on Mars with a bit of fancy design.

The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 

One would expect a Mars colony to shut down propellant production during storms and reserve its energy for life support.  Eventually, during very dark storms such as the one that killed Opportunity, secondary power sources would be required.  Nuclear is an obvious choice, but what to do if it is not available?

A 150 kVA genset masses 1850 kg.  This is another magnitude less mass.  It uses 2000 ft3 of natural gas per hour, or about 2 million BTU.  Or about 50 kg per hour or 1 tonne per day.

The genset seems like the safer bet, but perhaps a mid sized Mars colony would want both.

Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/14/2019 08:36 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 07/14/2019 09:21 pm
According to the papers I referenced in earlier posts, the force on similarly sized tower operating on Mars would be one tenth of the force on an Earth tower, so proportionally is should mass about 20 tonnes. [...]
Using carbon fiber blades might allow us to keep about the same mass for the rotor and hub, although the walls will get very thin, so perhaps unstable.  A bit of internal pressure might help there.
My guess is that somewhere along the line the tower would have the correct theoretical strength, but crumple du to buckling of the thin walls.  Hence the internal pressure suggestion.

There are other methods tested or proposed on Earth, but have been less practical because of the force of storm-winds and high gravity on Earth.

For example, because the blades are typically in front of the rotor-head, they have to be stiff enough not to hit the tower no matter how strong the wind. Trailing blades can flex much more, therefore be thinner and lighter (or longer for the same mass). There's some efficiency loss because of the turbulence caused by the tower, but this is more than compensated for by using longer blades. On Earth, taller towers require much higher strength, which tends to defeat the benefit of lighter blades. On Mars, lower gravity allows you to build higher, which favours trailing blades.

Similarly, there are designs for "kite" wind turbines. For eg, huge rotors that are allowed to lift themselves off the ground (such as the blimp concept, ironically called MARS (Magenn Air Rotor System.)) Or simple kites/sails which deploy and drag out a winch and then contract and are winched back in, powering a rotor on each pull-out.

Plus there are vertical wind turbines, which some advocates suggest works better on Mars. And ducted turbines, which drastically increases the efficiency, but aren't practical on Earth due to the mass, but might be better suited for Mars.

Trailing blades and Martian gravity might also allow a hybridising the tower-rotor with some elements of the lofted-rotor, where you optimise for tensile forces rather than compression.



Aside:

during the night or during dust storms,

AIUI from NASA comments, conventional tower-type wind-turbines don't work on Mars below about 30m/s wind speed. So only during storms. They don't help during normal nights, so don't augment that issue for solar. It's like having a wind-farm on Earth that only works during a hurricane.

That restriction might not apply for more Mars-optimised and low-speed optimised designs.



Personally I'm not a fan of wind, because it is improving much more slowly than PV and battery technology. Plus the further you drift from conventional Earth-use technology, the more you are paying for development, and the less you benefit from improvements on Earth.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 07/15/2019 12:21 am
One would expect a Mars colony to shut down propellant production during storms and reserve its energy for life support.  Eventually, during very dark storms such as the one that killed Opportunity, secondary power sources would be required.  Nuclear is an obvious choice, but what to do if it is not available?

Utilise your propellant stores.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 07/15/2019 02:19 am
One would expect a Mars colony to shut down propellant production during storms and reserve its energy for life support.  Eventually, during very dark storms such as the one that killed Opportunity, secondary power sources would be required.  Nuclear is an obvious choice, but what to do if it is not available?

Utilise your propellant stores.

Why use what is most precious, the normal flow should have enough resiliency for all but the most extreme emergencies.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 07/15/2019 08:37 am
One would expect a Mars colony to shut down propellant production during storms and reserve its energy for life support.  Eventually, during very dark storms such as the one that killed Opportunity, secondary power sources would be required.  Nuclear is an obvious choice, but what to do if it is not available?

Utilise your propellant stores.

Why use what is most precious, the normal flow should have enough resiliency for all but the most extreme emergencies.

Exactly.

For extreme emergencies, e.g. very dark storms such as the one that killed Opportunity, utilize your propellant stores as a backup power source.

I don't think anyone is suggesting that they would use propellant to make electricity during the normal ebb and flow of the power system.

It's a backup power source for emergencies.
Title: Re: Power options for a Mars settlement
Post by: Cheapchips on 07/15/2019 10:26 am
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.

The blades are a potential issue?  They tend to be single moulded pieces that are too big for SS.  They'd need an uncommon/custom bolt together design? Build something less efficient in situ?

You'd also need to transport the generator and a honking great crane from Earth?

It doesn't seem like something you'd want to be doing early on?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/15/2019 02:11 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.

The blades are a potential issue?  They tend to be single moulded pieces that are too big for SS.  They'd need an uncommon/custom bolt together design? Build something less efficient in situ?

You'd also need to transport the generator and a honking great crane from Earth?

It doesn't seem like something you'd want to be doing early on?

Hard to determine the exact requirement at this point.  How common are the events that killed Opportunity?  I certainly agree that very large turbines, that are useful on Earth because they optimize costs and tie into higher winds at higher altitudes might not be a good design for a system that would mainly be used during extreme weather events.  In most storm cases, I think that just cutting back fuel production will probably be enough, since fuel production will be, at least for a while, up to 90% of the power demand.  If the base also cuts down on food production and fabrication, and at the ultimate close down any larger heated public space, the power demand would be really low.  Just a few percent of the installed power.  I guess a reasonable approach would then be a small wind farm covering just a bit more than the most basic power demand, and a back-up methalox generator, just in case.

So if we suppose that there are 5 MW of installed solar to produce the methalox for 2 Starships over 2 years, 5% of this is 250 kW of power.  A small genset can handle this, burning 1.8 tonnes of methane per day.  If the dark period lasts 30 days, they we have burned about 100 tonnes of methane.  We need to produce 500 tonnes, so we need about 20% of two years, or 5 months of good solar production to be safe.

Then we can look into optimizing: 
-We can add even more solar and produce reserve methane faster, and depend on the genset.
-We can add windmills.
-..... can't think of anything else. 

40 tonnes of wind turbines can be replaced by 13 000 m2 of 3kg/m2 solar, producing 1 kWh per day per m2.  Supposing the embed energy of methane is about 130 MJ, or 36 kWh, 13 000 m2 produce 360 kg of methane per day.  So in 277 days the solar arrays would produce the back-up fuel required.

So after a bit less than a year, the back-up methane is produced, and the extra power for the rest of the two years to the next synod can be used to increase in-situ production of other goods, such as food or construction materials.

So, solar trumps wind?
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 07/15/2019 02:14 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.

The blades are a potential issue?  They tend to be single moulded pieces that are too big for SS.  They'd need an uncommon/custom bolt together design? Build something less efficient in situ?

You'd also need to transport the generator and a honking great crane from Earth?

It doesn't seem like something you'd want to be doing early on?
Is it possible to make inflatable of inflation reinforced foldable blades?
Title: Re: Power options for a Mars settlement
Post by: Steve D on 07/15/2019 04:18 pm
How much hydrogen would be stored before turning it into methane? Am assuming the hydrogen production isnt in lockstep with the methane production. Especially if hydrogen production is done during the day and methane production is an all day event. If there is enough hydrogen stored it could be used to supply fuel cells during an emergency. Am also assuming that there would be some warning of a dust storm coming so methane production could be stopped and enough hydrogen produced to keep essential equipment running through the storm.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/15/2019 04:25 pm
How much hydrogen would be stored before turning it into methane? Am assuming the hydrogen production isnt in lockstep with the methane production. Especially if hydrogen production is done during the day and methane production is an all day event. If there is enough hydrogen stored it could be used to supply fuel cells during an emergency. Am also assuming that there would be some warning of a dust storm coming so methane production could be stopped and enough hydrogen produced to keep essential equipment running through the storm.
Not much more than a day's production.  The methane is easier to store long term than the hydrogen, and it seems that the Sabatier reaction likes to operate continuously.  Gen-sets are quite efficient when running on natural gas (methane), and the emergency might last for up to a month, if I understand the light curves from Opportunity's demise correctly.
Batteries would be required to operate the Sabatier reaction pumps and accessories during the night. The Sabatier itself is exothermic and shouldn't need power.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/15/2019 04:29 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.

The blades are a potential issue?  They tend to be single moulded pieces that are too big for SS.  They'd need an uncommon/custom bolt together design? Build something less efficient in situ?

You'd also need to transport the generator and a honking great crane from Earth?

It doesn't seem like something you'd want to be doing early on?
Is it possible to make inflatable of inflation reinforced foldable blades?
Google gives us an Israeli design.  And there are the tethered designs as well.

But if my earlier post is correct, wind power loses to solar+methane storage+gen-set.  So wind would not be required, and would not offer higher safety than a gen-set.
Title: Re: Power options for a Mars settlement
Post by: Lar on 07/15/2019 06:26 pm
One thing about wind vs solar that I don't think I've seen mentioned.... (or not as much)... level of effort.

We've seen proposals for solar arrays that take very little effort to deploy. And it was pointed out above that the mass of wind towers and blades can be significantly less for their size than on Earth, because the loads on them are less.

But I suspect that the amount of hand labor needed to unpack, build, install, deploy wind towers per kilowatt of installed power capacity will be far higher than for cells. This needs to be taken into account as well I think. A lot of it is fiddly enough that I'm dubious it could be automated.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 07/15/2019 06:54 pm
Hard to determine the exact requirement at this point.  How common are the events that killed Opportunity?

You get a regional storms every Martian year, and a global storm on average every 3 Martian years (about 5 Earth years.) But the really heavy storms seem to happen decadally. The explanation I read was that the big storms clear away enough loose material that the next global storm is thinner, it takes a bunch of regional storms in the off-years to build up enough fines for the next big one.

But we've only really been tracking storms for a few decades, and only had a continuous presence in orbit and on the ground since Spirit landed. So we might not have a representative sample of Mars weather.

So if we suppose that there are 5 MW of installed solar to produce the methalox for 2 Starships over 2 years, 5% of this is 250 kW of power.  A small genset can handle this, burning 1.8 tonnes of methane per day.  If the dark period lasts 30 days, they we have burned about 100 tonnes of methane.  We need to produce 500 tonnes, so we need about 20% of two years, or 5 months of good solar production to be safe.

Not quite. As mentioned before, optical clarity tends to be seasonal, half a Mars year of clear skies, half of variable dusty. Effectively, one Earth-year on, one year off. You'll be focusing your propellant production on that good year. (During the off-year, you'll need the spare capacity for agriculture, assuming artificial lighting.) That means double the solar required, just during non-storm years. But worse, since the big storms happen during what should be the clear-sky season, so you effectively lose a whole Martian year. That means you'll need to double the installed PV again compared to what you would assume for continuous (daytime) production.

On the flip-side, even during Oppy-killer storms, there'll only be a few days at a time, intermittently over that worst month, where solar production drops to effectively zero; although you will have reduced production for about 3-5 months as the sky clears. Solar PV happily eats scattered light, so works during most dust storms, and dust in the sky reflects light when the sun is over the horizon, increasing the effective day-length. Additionally, during storms, the night-time temperature doesn't drop as much (the dust acts as a greenhouse layer), reducing demand on the batteries. Once you switch off propellant production, and reduce ag demand, you won't have many days where you'd need supplemental power from the methalox genset.

So, solar trumps wind?

In spite of all the inconveniences, yes. Setting up a wind-farm that only works once every 5 years at best, seems... inefficient.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 07/15/2019 07:02 pm
One thing about wind vs solar that I don't think I've seen mentioned.... (or not as much)... level of effort.

We've seen proposals for solar arrays that take very little effort to deploy. And it was pointed out above that the mass of wind towers and blades can be significantly less for their size than on Earth, because the loads on them are less.

But I suspect that the amount of hand labor needed to unpack, build, install, deploy wind towers per kilowatt of installed power capacity will be far higher than for cells. This needs to be taken into account as well I think. A lot of it is fiddly enough that I'm dubious it could be automated.

Strong points.  Tower/Nacelle/Blade assemblies do seem a logistics nightmare. 

I wonder though about something creative based on a vertical axis system.   Still perhaps not automated but a less labor-intensive emergency backup.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/16/2019 08:08 am
How much hydrogen would be stored before turning it into methane? Am assuming the hydrogen production isnt in lockstep with the methane production. Especially if hydrogen production is done during the day and methane production is an all day event. If there is enough hydrogen stored it could be used to supply fuel cells during an emergency. Am also assuming that there would be some warning of a dust storm coming so methane production could be stopped and enough hydrogen produced to keep essential equipment running through the storm.
Not much more than a day's production.  The methane is easier to store long term than the hydrogen, and it seems that the Sabatier reaction likes to operate continuously.  Gen-sets are quite efficient when running on natural gas (methane), and the emergency might last for up to a month, if I understand the light curves from Opportunity's demise correctly.
Batteries would be required to operate the Sabatier reaction pumps and accessories during the night. The Sabatier itself is exothermic and shouldn't need power.

For some perspective:

- Assuming 240 tonnes of methane we're looking at needing 60 tonnes of hydrogen per synod, per Starship.

- Assuming sufficient solar electricity is only available to produce methane 360 days each synod we need 166 2/3 kg of hydrogen per day, per Starship

- During daylight we can run directly off of electrolysis.  For simplicity's sake assume 10/24ths of the time is spent running direct.  This takes the storage requirement down to 97.22 kg stored hydrogen per day, per Starship.

Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.  Running continuously does not preclude throttling down when running on stored hydrogen.  In theory running at 10% throttle should be easy enough, although I haven't yet tried this myself.
Title: Re: Power options for a Mars settlement
Post by: Pete on 07/16/2019 01:42 pm

My first calculation was for a shorter 60m tower, with a smaller diameter, hence the 3 tonnes.


So sorry, but you cannot make a claim for 3 tonnes, while showing a picture of a tower that you admit will be 20 tons plus. In a business environment that would be called fraud.
In a science environment like this forum, it is just plain Falsified Data.
Which, if you were a scientist, you would know to be on of the the greatest sins possible.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 07/16/2019 01:52 pm

My first calculation was for a shorter 60m tower, with a smaller diameter, hence the 3 tonnes.


So sorry, but you cannot make a claim for 3 tonnes, while showing a picture of a tower that you admit will be 20 tons plus. In a business environment that would be called fraud.
In a science environment like this forum, it is just plain Falsified Data.
Which, if you were a scientist, you would know to be on of the the greatest sins possible.

Relax Francis.  Not as great a sin as not being good to our fellow long-time high-quality contributors.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/16/2019 03:06 pm

My first calculation was for a shorter 60m tower, with a smaller diameter, hence the 3 tonnes.


So sorry, but you cannot make a claim for 3 tonnes, while showing a picture of a tower that you admit will be 20 tons plus. In a business environment that would be called fraud.
In a science environment like this forum, it is just plain Falsified Data.
Which, if you were a scientist, you would know to be on of the the greatest sins possible.
Please read the post again.  I claimed 3 tonnes for the tower, not for the entire unit.  For the tower to work at this mass, it would probably need to be pressurized, because otherwise it would fail through buckling.  No doubt poorly worded, I was asking if the proposal made sense, more than presenting the idea as a finished process.

I do not claim to be a scientist.  I am an enthusiastic illustrator with an engineering background.  I expect to be corrected for my mistakes in all collegiality by more expert contributors.

And that being said, am I correct in my ultimate conclusion that wind power on Mars is less effective than solar+ genset+ propellant?  My main interest here being that I don't need to work anymore on the wind turbine design.  My ultimate goal is to make realistic illustrations, and these take time.  If they are showing elements that will not be built, I would like to avoid working for nothing.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 07/16/2019 05:32 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.

From what I'm reading in ISRU methane research, those two statements are not quite synonymous. Maintaining "constant temperature" is an issue during operation (because the reactors tend to get hot spots which sinter the catalyst and cold spots which promote coking), not just start/stop, and seems primarily related to nickel catalysts. Newer (only lab-scale) research seems to have eliminated catalyst degradation during start/stop, with only the issue of uniform heat-transfer during operation being the area of research focus.

(For example, a paper (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120016419.pdf) on ruthenium catalysts used 6 (varying duration) start/stop cycles in a 100hr test with no degradation, with operating runs as short as 3hrs or as long as 24. And they seem to treat that as a standardised catalyst test.)
Title: Re: Power options for a Mars settlement
Post by: sghill on 07/16/2019 05:50 pm

My first calculation was for a shorter 60m tower, with a smaller diameter, hence the 3 tonnes.


So sorry, but you cannot make a claim for 3 tonnes, while showing a picture of a tower that you admit will be 20 tons plus. In a business environment that would be called fraud.
In a science environment like this forum, it is just plain Falsified Data.
Which, if you were a scientist, you would know to be on of the the greatest sins possible.
Please read the post again.  I claimed 3 tonnes for the tower, not for the entire unit.  For the tower to work at this mass, it would probably need to be pressurized, because otherwise it would fail through buckling.  No doubt poorly worded, I was asking if the proposal made sense, more than presenting the idea as a finished process.

I do not claim to be a scientist.  I am an enthusiastic illustrator with an engineering background.  I expect to be corrected for my mistakes in all collegiality by more expert contributors.

And that being said, am I correct in my ultimate conclusion that wind power on Mars is less effective than solar+ genset+ propellant?  My main interest here being that I don't need to work anymore on the wind turbine design.  My ultimate goal is to make realistic illustrations, and these take time.  If they are showing elements that will not be built, I would like to avoid working for nothing.

Wind generators will not be built on Mars. I say this as someone who owned an institution scale solar and wind development company. Weight and volume to ship a wind turbine are prohibitive, when the equivalent weight and volume of solar panels can be used. But that's not the real reason wind won't be used.

The real reason is torque. It isn't enough to have gigantic windmills that can be moved the 1% atmospheric pressure on Mars. You also need air density to provide torque to create meaningful power from a generator.

On Mars at surface level, air pressure is 0.02kg/m3. Wind Pressure per meter of surface area in a 10 m/sec breeze is .5*0.02*102= .1kg = 100 grams= 1 apple.  On Earth at sea level, air pressure is 1.25kg/m3.  Wind Pressure per meter of surface area in a 10 m/sec breeze is .5*1.25*102= 62.5kg/m pressure per meter (assuming it's hitting perpendicular) = the mass of one average sized woman.
 
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/16/2019 06:17 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.

From what I'm reading in ISRU methane research, those two statements are not quite synonymous. Maintaining "constant temperature" is an issue during operation (because the reactors tend to get hot spots which sinter the catalyst and cold spots which promote coking), not just start/stop, and seems primarily related to nickel catalysts. Newer (only lab-scale) research seems to have eliminated catalyst degradation during start/stop, with only the issue of uniform heat-transfer during operation being the area of research focus.

(For example, a paper (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120016419.pdf) on ruthenium catalysts used 6 (varying duration) start/stop cycles in a 100hr test with no degradation, with operating runs as short as 3hrs or as long as 24. And they seem to treat that as a standardised catalyst test.)

That paper is the one that lead me to researching pulsating heat pipes(PHP).  PHPs allow the temperature control needed to keep nickel from degrading.  Using nickel is advantageous on Earth because ruthenium costs ~40 times more.  When it comes to Martian settlement we also want to consider ease of purification and other industrial uses.

Thanks for linking the paper.  That is one of the hundred I hadn't yet tracked down again.

Edit:  Here is an intro to PHPs.

https://www.electronics-cooling.com/2003/05/an-introduction-to-pulsating-heat-pipes/
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/16/2019 07:29 pm

My first calculation was for a shorter 60m tower, with a smaller diameter, hence the 3 tonnes.


So sorry, but you cannot make a claim for 3 tonnes, while showing a picture of a tower that you admit will be 20 tons plus. In a business environment that would be called fraud.
In a science environment like this forum, it is just plain Falsified Data.
Which, if you were a scientist, you would know to be on of the the greatest sins possible.
Please read the post again.  I claimed 3 tonnes for the tower, not for the entire unit.  For the tower to work at this mass, it would probably need to be pressurized, because otherwise it would fail through buckling.  No doubt poorly worded, I was asking if the proposal made sense, more than presenting the idea as a finished process.

I do not claim to be a scientist.  I am an enthusiastic illustrator with an engineering background.  I expect to be corrected for my mistakes in all collegiality by more expert contributors.

And that being said, am I correct in my ultimate conclusion that wind power on Mars is less effective than solar+ genset+ propellant?  My main interest here being that I don't need to work anymore on the wind turbine design.  My ultimate goal is to make realistic illustrations, and these take time.  If they are showing elements that will not be built, I would like to avoid working for nothing.

Wind generators will not be built on Mars. I say this as someone who owned an institution scale solar and wind development company. Weight and volume to ship a wind turbine are prohibitive, when the equivalent weight and volume of solar panels can be used. But that's not the real reason wind won't be used.

The real reason is torque. It isn't enough to have gigantic windmills that can be moved the 1% atmospheric pressure on Mars. You also need air density to provide torque to create meaningful power from a generator.

On Mars at surface level, air pressure is 0.02kg/m3. Wind Pressure per meter of surface area in a 10 m/sec breeze is .5*0.02*102= .1kg = 100 grams= 1 apple.  On Earth at sea level, air pressure is 1.25kg/m3.  Wind Pressure per meter of surface area in a 10 m/sec breeze is .5*1.25*102= 62.5kg/m pressure per meter (assuming it's hitting perpendicular) = the mass of one average sized woman.
The pressure should be 1.02 kg/m2, I believe.  And since it is designed for 30 m/s and not 10 m/s, since it is a storm system, and pressure goes up to the square of the velocity, then the pressure is a gigantic 9 kg/m2 :-) Not enough to change your conclusions, but at least there was some sense to asking the question.  But I agree that the answer seems to be that wind is not cost effective, even as a storm system. 
 
So all I need to model is a genset, i.e. a shipping container with water or air cooling.  Much simpler to model :-)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/16/2019 07:31 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.
not enough, never enough.... back to unrolling solar panels  :)
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/16/2019 07:55 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.
not enough, never enough.... back to unrolling solar panels  :)
Is it enough to cope with electrolysis - no.
Is it enough to be a useful potential addition that needs to take only the blades and a short bearing/tail to Mars to provide a useful amount of power especially for blackouts - is another question.

(https://upload.wikimedia.org/wikipedia/commons/thumb/f/fd/DK_Fanoe_Windmill01.JPG/400px-DK_Fanoe_Windmill01.JPG)
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 07/16/2019 08:02 pm
Which is the lower risk?

genset:
 ICU 25% eff.
 100's of moving parts
 complicated air induction system and lubrication system

fuel cell:
 50% eff.
 no moving parts
 useful waste heat
 lighter than genset
 more expensive than genset
 instant on
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/16/2019 08:17 pm
Which is the lower risk?

genset:
 ICU 25% eff.
 100's of moving parts
 complicated air induction system and lubrication system

fuel cell:
 50% eff.
 no moving parts
 useful waste heat
 lighter than genset
 more expensive than genset
 instant on
Are methane fuel cells rated for continuous operations for one month?  Do they exist up to MW power?  No experience with them, but by all means, if that's a better solution. 
Have worked on 4 MW gensets for mine power in northern Canada.  These are robust continuous operation machines.  these Gensets are usually counted at 40% efficiency for diesel ones, might be less for methane.  These will be pretty continuous loads so efficiency is high, not like a car. 
Waste heat of genset can be used to heat buildings too, so that is not such a gain.  Heat exchangers are usually required so that adds mass.  And if the main load is heat, and not light, you can just burn the methane in a boiler for unbeatable 80-90% efficiency.  So boiler + genset or fuel cells.  Still not wind.  Actually, for a mostly heat load, even less wind.

Although I hate the idea of just burning that nice methalox.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/16/2019 08:20 pm
Which is the lower risk?

genset:
 ICU 25% eff.
 100's of moving parts
 complicated air induction system and lubrication system

fuel cell:
 50% eff.
 no moving parts
 useful waste heat
 lighter than genset
 more expensive than genset
 instant on
Are methane fuel cells rated for continuous operations for one month?  Do they exist up to MW power?  No experience with them, but by all means, if that's a better solution. 
Have worked on 4 MW gensets for mine power in northern Canada.  These are robust continuous operation machines.  these Gensets are usually counted at 40% efficiency for diesel ones, might be less for methane.  These will be pretty continuous loads so efficiency is high, not like a car. 
Waste heat of genset can be used to heat buildings too, so that is not such a gain.  Heat exchangers are usually required so that adds mass.  And if the main load is heat, and not light, you can just burn the methane in a boiler for unbeatable 80-90% efficiency.  So boiler + genset or fuel cells.  Still not wind.  Actually, for a mostly heat load, even less wind.

Although I hate the idea of just burning that nice methalox.

Methane fuel cells aren't yet up to the task, as far as I know.  We're getting there though, so use in the mid to late 2020s isn't completely out of the question.

https://www.sciencedaily.com/releases/2018/10/181029130939.htm
Title: Re: Power options for a Mars settlement
Post by: Lar on 07/16/2019 08:38 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.
Naturally occuring as in "recently planted" ? (the 9m was what finally nudged me into getting your reference)
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 07/16/2019 09:11 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.
Naturally occuring as in "recently planted" ? (the 9m was what finally nudged me into getting your reference)

Now I'm wondering how effective a repurposed "Chomper" would be, that cuts the foreward aeroshell into 4 blades  and attaches them to a tail and carosel mechanisim that the chomper brought.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/16/2019 09:39 pm
The main use of this tower (or a number of smaller ones) would be during the night or during dust storms, when solar power is not available.  In particular the long winter dust storms than can go to very low tau. 
I do wonder how much you can get out of the naturally occurring ~55m*9m towers, with the addition of a 40m or so turbine.
Naturally occuring as in "recently planted" ? (the 9m was what finally nudged me into getting your reference)

Now I'm wondering how effective a repurposed "Chomper" would be, that cuts the foreward aeroshell into 4 blades  and attaches them to a tail and carosel mechanisim that the chomper brought.
Your wish is my command  ;)
I believe, in all sincerity, that it would be tremendously ineffective. 
Title: Re: Power options for a Mars settlement
Post by: Kansan52 on 07/16/2019 09:46 pm
Pack some blades, once landed and empty, turn the interior into a horizontal wind turbine space.
Title: Re: Power options for a Mars settlement
Post by: RoboGoofers on 07/16/2019 10:12 pm
Which is the lower risk?

genset:
 ICU 25% eff.
 100's of moving parts
 complicated air induction system and lubrication system

fuel cell:
 50% eff.
 no moving parts
 useful waste heat
 lighter than genset
 more expensive than genset
 instant on
Are methane fuel cells rated for continuous operations for one month?  Do they exist up to MW power?  No experience with them, but by all means, if that's a better solution. 
Have worked on 4 MW gensets for mine power in northern Canada.  These are robust continuous operation machines.  these Gensets are usually counted at 40% efficiency for diesel ones, might be less for methane.  These will be pretty continuous loads so efficiency is high, not like a car. 
Waste heat of genset can be used to heat buildings too, so that is not such a gain.  Heat exchangers are usually required so that adds mass.  And if the main load is heat, and not light, you can just burn the methane in a boiler for unbeatable 80-90% efficiency.  So boiler + genset or fuel cells.  Still not wind.  Actually, for a mostly heat load, even less wind.

Although I hate the idea of just burning that nice methalox.
What I keep thinking about re: using the fuel and oxidizer to weather a storm is that at what point do they just bug out? just head to orbit for a couple months and unfurl the ship solar panels and run closed-cycle until the storm subsides. or go on vacation to Phobos.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 07/16/2019 10:13 pm
Pack some blades, once landed and empty, turn the interior into a horizontal wind turbine space.
Cut in half in a flat vertical plane, then offset each half "cylinder-come-cone" horizontally equidistant from the CoR in that plane. Of course this assembly must be raised and  a bearing and disk inserted below, to allow it to rotate, along with a generator somewhere... child's play.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 07/16/2019 10:25 pm
Pack some blades, once landed and empty, turn the interior into a horizontal wind turbine space.
Cut in half in a flat vertical plane, then offset each half "cylinder-come-cone" horizontally equidistant from the CoR in that plane. Of course this assembly must be raised and  a bearing and disk inserted below, to allow it to rotate, along with a generator somewhere... child's play.
That's the interesting part of using a Chomper as the base. The shell is already elevated, and the bearing and disk can be pre-installed on earth,
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 07/16/2019 11:01 pm
[genset vs fuel cell comparison]

Methane burning gas turbine power stations run at about 30% efficiency. High-temp methane fuel-cells run at about 60% efficiency. That's a huge incentive for power generators to use the more efficient technology; if a fuel cell based peaker-plant was twice as expensive to build, it would pay for itself within around 4 years of continuous operation, after which their ongoing $/kWh cost halves.

Yet no-one uses methane fuel cells for commercial power production. That should be a big red flag to you that this isn't a mature or reliable technology.

fuel cell:
[...]
instant on

That seems backwards. You need to bring the fuel cell up to temperature before it can start producing power. Whereas gensets can start up within seconds.



Both ICE and gas turbines are known tech, used commercially at a myriad of scales, with predictable MTBF, in spite of their "hundreds of moving parts".

Additionally, using an ICE gives you machine-shop level maintenance. (Although in saying that, gas turbines are the same basic technology as the fuel pumps on Raptor engines. So if you have a machine shop capable of servicing Raptors (which seems advisable), they should be capable of servicing and rebuilding gas turbine power generators.)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/17/2019 02:31 am
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.

From what I'm reading in ISRU methane research, those two statements are not quite synonymous. Maintaining "constant temperature" is an issue during operation (because the reactors tend to get hot spots which sinter the catalyst and cold spots which promote coking), not just start/stop, and seems primarily related to nickel catalysts. Newer (only lab-scale) research seems to have eliminated catalyst degradation during start/stop, with only the issue of uniform heat-transfer during operation being the area of research focus.

(For example, a paper (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120016419.pdf) on ruthenium catalysts used 6 (varying duration) start/stop cycles in a 100hr test with no degradation, with operating runs as short as 3hrs or as long as 24. And they seem to treat that as a standardised catalyst test.)

That paper is the one that lead me to researching pulsating heat pipes(PHP).  PHPs allow the temperature control needed to keep nickel from degrading.  Using nickel is advantageous on Earth because ruthenium costs ~40 times more.  When it comes to Martian settlement we also want to consider ease of purification and other industrial uses.

Thanks for linking the paper.  That is one of the hundred I hadn't yet tracked down again.

Edit:  Here is an intro to PHPs.

https://www.electronics-cooling.com/2003/05/an-introduction-to-pulsating-heat-pipes/
What might be the size/mass of an Electrolysis and Sabatier unit to produce the propellant for a Starship vehicle?
For the martian atmosphere compressor, I find about 10 hp.  For the phase change of CO2, about 60 kW, or another 45 hp.  So that is fairly small.  But for electrolysis, about 1 MW of power so perhaps that might be the largest piece of equipment? I am familiar with a totally different type of electrolysis, aluminium, and each one of the cells in a line has about 1 MW of power.  And those are pretty big.


Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/17/2019 05:21 am
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.

From what I'm reading in ISRU methane research, those two statements are not quite synonymous. Maintaining "constant temperature" is an issue during operation (because the reactors tend to get hot spots which sinter the catalyst and cold spots which promote coking), not just start/stop, and seems primarily related to nickel catalysts. Newer (only lab-scale) research seems to have eliminated catalyst degradation during start/stop, with only the issue of uniform heat-transfer during operation being the area of research focus.

(For example, a paper (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120016419.pdf) on ruthenium catalysts used 6 (varying duration) start/stop cycles in a 100hr test with no degradation, with operating runs as short as 3hrs or as long as 24. And they seem to treat that as a standardised catalyst test.)

That paper is the one that lead me to researching pulsating heat pipes(PHP).  PHPs allow the temperature control needed to keep nickel from degrading.  Using nickel is advantageous on Earth because ruthenium costs ~40 times more.  When it comes to Martian settlement we also want to consider ease of purification and other industrial uses.

Thanks for linking the paper.  That is one of the hundred I hadn't yet tracked down again.

Edit:  Here is an intro to PHPs.

https://www.electronics-cooling.com/2003/05/an-introduction-to-pulsating-heat-pipes/
What might be the size/mass of an Electrolysis and Sabatier unit to produce the propellant for a Starship vehicle?
For the martian atmosphere compressor, I find about 10 hp.  For the phase change of CO2, about 60 kW, or another 45 hp.  So that is fairly small.  But for electrolysis, about 1 MW of power so perhaps that might be the largest piece of equipment? I am familiar with a totally different type of electrolysis, aluminium, and each one of the cells in a line has about 1 MW of power.  And those are pretty big.

Aluminium electrolysis is huge compared to a Sabatier system.  Production rates are critical here, and the mass/volume for solar panels and methalox storage isn't included, but if we can't refuel a Starship per synod for >2.5 tonnes and >6 m^3 we've done something wrong.

Note:  My personal preference is to have big horking storage tanks, as extra liquid water, purified liquid water, or methalox is very useful.  Violating Edison's Law, "Better" is the enemy of "good", can improve the above even more.  I personally don't believe in violating Edison's Law but not allowing excessive storage does not do this thread justice.  Liquid water/methalox masses/volumes are left out intentionally.

Note 2:  I am well aware of Akin's Law #30, "If you want to have a maximum effect on the design of a new engineering system, learn to draw. Engineers always wind up designing the vehicle to look like the initial artist's concept."  I can't draw in a format modern computers can understand.  Even still, I'm happy to use "paint" so someone more skilled than myself can render the concepts properly.

Note 3: I'd love to deploy this technology on Earth, but the water shortage in the sunny southwest problem vexes me. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/17/2019 02:28 pm
This seems like a real product:
http://www.arevah2gen.com/en/products-services/hydrogen-generators

Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/17/2019 02:50 pm
This seems like a real product:
http://www.arevah2gen.com/en/products-services/hydrogen-generators
Taking the 100kg of production of hydrogen per day upthread as accurate, and looking at the specs for those giving 4.4kWh/Nm^3, that is 1100m^3/day.
Or 4800kWh/day, or 200kWav.

~600kW operating.
This is in the 'E80' class, which is the first model to not fit in a standard 20 foot container, and needs to go to 40'.

The most pessimistic interpretation of weight (which I cannot find listed) would be ~20 tons, based on the load limit of the 20' container.

You're going to need some way to dump ~150kW of heat when on, though if you have a large enough (>50 tons) store of water, that can reduce to 50kW as it's always chilling, not only when operating.

Keeping several 100's kg of hydrogen is trivial if you can use one of the propellant tanks, perhaps with the feed/cooling water in the other one.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/17/2019 03:11 pm
This seems like a real product:
http://www.arevah2gen.com/en/products-services/hydrogen-generators
Taking the 100kg of production of hydrogen per day upthread as accurate, and looking at the specs for those giving 4.4kWh/Nm^3, that is 1100m^3/day.
Or 4800kWh/day, or 200kWav.

~600kW operating.
This is in the 'E80' class, which is the first model to not fit in a standard 20 foot container, and needs to go to 40'.

The most pessimistic interpretation of weight (which I cannot find listed) would be ~20 tons, based on the load limit of the 20' container.

You're going to need some way to dump ~150kW of heat when on, though if you have a large enough (>50 tons) store of water, that can reduce to 50kW as it's always chilling, not only when operating.

Keeping several 100's kg of hydrogen is trivial if you can use one of the propellant tanks, perhaps with the feed/cooling water in the other one.
So with this we are actually already too powerful for heating the habitats, and already need to start rejecting heat outside of the base?.
We can pre heat the water a bit
Melt ice
Have very lossy greenhouses, but that comes with problems
...  any other use for low grade heat?

And that's without the Sabatier excess heat as well.
And the excess heat of liquefaction of the gases.

So that leads me to wondering about air cooled systems on Mars, including forced flow fluid coolers or radiators that are freeze proof.  Don't think glycols would be safe enough at -60C, so are we down to ammonia and such?
Can we have very high rmp fans that make coolers more effective?  Compensate the low density with high velocity?
Some of the high temperatures in summer may actually be a problem for air cooling, so perhaps some kind of evaporating water bassins instead?  Single pass water towers on Mars?

Title: Re: Power options for a Mars settlement
Post by: rakaydos on 07/17/2019 03:19 pm
This seems like a real product:
http://www.arevah2gen.com/en/products-services/hydrogen-generators
Taking the 100kg of production of hydrogen per day upthread as accurate, and looking at the specs for those giving 4.4kWh/Nm^3, that is 1100m^3/day.
Or 4800kWh/day, or 200kWav.

~600kW operating.
This is in the 'E80' class, which is the first model to not fit in a standard 20 foot container, and needs to go to 40'.

The most pessimistic interpretation of weight (which I cannot find listed) would be ~20 tons, based on the load limit of the 20' container.

You're going to need some way to dump ~150kW of heat when on, though if you have a large enough (>50 tons) store of water, that can reduce to 50kW as it's always chilling, not only when operating.

Keeping several 100's kg of hydrogen is trivial if you can use one of the propellant tanks, perhaps with the feed/cooling water in the other one.
Just considering dimentions, is there a combination of 2 of the 20' container versions that cover the right production range? I ask because 8.5m internal radius can support 3x 20' shipping containers abrest, letting you use this COTS design straight, AND have a spare.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 07/17/2019 03:25 pm

So that leads me to wondering about air cooled systems on Mars, including forced flow fluid coolers or radiators that are freeze proof.  Don't think glycols would be safe enough at -60C, so are we down to ammonia and such?
Can we have very high rmp fans that make coolers more effective?  Compensate the low density with high velocity?
Some of the high temperatures in summer may actually be a problem for air cooling, so perhaps some kind of evaporating water bassins instead?  Single pass water towers on Mars?

Cooling into drilled well?
Hot water down well to melt ice?
Closed loop with non freezable coolant?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/17/2019 03:48 pm

So that leads me to wondering about air cooled systems on Mars, including forced flow fluid coolers or radiators that are freeze proof.  Don't think glycols would be safe enough at -60C, so are we down to ammonia and such?
Can we have very high rmp fans that make coolers more effective?  Compensate the low density with high velocity?
Some of the high temperatures in summer may actually be a problem for air cooling, so perhaps some kind of evaporating water bassins instead?  Single pass water towers on Mars?

Cooling into drilled well?
Hot water down well to melt ice?
Closed loop with non freezable coolant?
All good options.  I expect ice melting will be the most likely one.  Melt ice with circulating water, and have some kind of storage tank to start the loop if the system ever stops.
A surface field with a few thousand feet of PVC pipe, perhaps with ammonia or a higher pressure safer fluid might be the solution.  Heat transport through martian soil may not be all that good and might require too much pipe though.  Same thing with wells.  Kind of the reverse of what can happen with undersized wells in ground source heat pumps. 
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 07/17/2019 04:16 pm
[genset vs fuel cell comparison]

Methane burning gas turbine power stations run at about 30% efficiency. High-temp methane fuel-cells run at about 60% efficiency. That's a huge incentive for power generators to use the more efficient technology; if a fuel cell based peaker-plant was twice as expensive to build, it would pay for itself within around 4 years of continuous operation, after which their ongoing $/kWh cost halves.

Yet no-one uses methane fuel cells for commercial power production. That should be a big red flag to you that this isn't a mature or reliable technology.

fuel cell:
[...]
instant on

That seems backwards. You need to bring the fuel cell up to temperature before it can start producing power. Whereas gensets can start up within seconds.



Both ICE and gas turbines are known tech, used commercially at a myriad of scales, with predictable MTBF, in spite of their "hundreds of moving parts".

Additionally, using an ICE gives you machine-shop level maintenance. (Although in saying that, gas turbines are the same basic technology as the fuel pumps on Raptor engines. So if you have a machine shop capable of servicing Raptors (which seems advisable), they should be capable of servicing and rebuilding gas turbine power generators.)

I know little about these systems other than what I've read. 
I agree that ICE and gas turbines are known tech on earth.  Until enough infrastructure is built locally to support them I think the simplicity of fuel cells makes them the better choice.

Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/17/2019 05:10 pm
This seems like a real product:
http://www.arevah2gen.com/en/products-services/hydrogen-generators

That is a real product but it has bits we shouldn't need in a Martian propellant plant.

- Solar panels output DC.  I see no reason to convert to AC only to have to convert back to DC.

- The Sabatier reactor is a ~350 C heat source.  Distillation can replace the advanced reverse osmosis and electrodeionization units.

- The "heat exchanger cooled by a chiller at 4°C to obtain up 99.999% H2 purity" can be replaced by a hydrogen permeable membrane.  Here is an example: https://pro.tanaka.co.jp/en/products/Hydrogen_Permeable_Films.html (https://pro.tanaka.co.jp/en/products/Hydrogen_Permeable_Films.html)

In hindsight I should have put more disclaimers on my 2.5 tonne figure.  What is included is the distillation unit, electrolysis unit, hydrogen buffer(10 kg storage capacity), hydrogen permeable membrane, Sabatier reactor, control systems, and plumbing/wiring to connect the bits.  I haven't looked into fractional distillation of the Martian atmosphere in enough detail to estimate this subsystem's mass.  Heat rejection mass depends on what we want to use the waste heat for.  Water and methalox storage sold separately.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/17/2019 06:24 pm
This seems like a real product:
http://www.arevah2gen.com/en/products-services/hydrogen-generators

That is a real product but it has bits we shouldn't need in a Martian propellant plant.
It is at least interesting to answer the question 'what is the mass/price/volume of completely off the shelf hardware'. I do agree lots of bits would not be as required.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 07/17/2019 06:27 pm
It is at least interesting to answer the question 'what is the mass/price/volume of completely off the shelf hardware'. I do agree lots of bits would not be as required.

We call that the speebaydevil Benchmark.   ;)
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/17/2019 08:09 pm
This seems like a real product:
http://www.arevah2gen.com/en/products-services/hydrogen-generators

That is a real product but it has bits we shouldn't need in a Martian propellant plant.
It is at least interesting to answer the question 'what is the mass/price/volume of completely off the shelf hardware'. I do agree lots of bits would not be as required.

The integrated system doesn't answer questions though.  What we care about are the components needed for a Martian propellant plant.  Areva has an image of a PEM Electrolyser 15 Nm3/h stack[1].  What I can't find are mass/price/volume figures.

My estimate comes from applying a scaling factor to hardware sold by the Fuel Cell Store[2].  At least they give mass/price/volume for their smaller electrolysis units.  They also sell metal hydride hydrogen storage.

Whether we should be looking at acidic PEM or alkaline(KOH) electrolysis is an interesting side topic.  I figure I'll add a link to a useful paper to add some value to this post[3].

[1] http://www.arevah2gen.com/en/products-services (http://www.arevah2gen.com/en/products-services)
[2] https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-production-electrolyzers (https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-production-electrolyzers)
[3] http://jes.ecsdl.org/content/163/11/F3197.full.pdf (http://jes.ecsdl.org/content/163/11/F3197.full.pdf)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/17/2019 11:49 pm
Here is another supplier of hydrogen systems.  Belgian it seems.
And there are masses and volumes.
https://www.hydrogenics.com/wp-content/uploads/2-1-1-industrial-brochure_english.pdf?sfvrsn=2
Very similar specs to Areva.

And Areva has a fuel cell system, designed for one hour of back-up power.  Basically a big UPS.  Rather heavy for our needs and not visibly designed for continuous use.  Joined the file.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/18/2019 01:39 am
The Hydrogenics information is far more useful.  That brochure was from February, 2011, so I'd go with figures from their website.

It would be nice to see information about their efforts to switch to membranes but that would make selling current systems very difficult.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/18/2019 08:53 am
Don't think glycols would be safe enough at -60C, so are we down to ammonia and such?

One of the "lessons learned" from the ISS is that ammonia is a lot of trouble. The toxic atmosphere drills and training is costly. https://www.forbes.com/sites/quora/2013/05/31/how-would-the-iss-differ-if-it-was-being-designed-today/

The Russian Orbital Segment uses silicone oil for the exterior loop. Good down to -70C. http://www.clearcoproducts.com/heat-transfer-fluids-low.html

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/18/2019 12:40 pm
Don't think glycols would be safe enough at -60C, so are we down to ammonia and such?

One of the "lessons learned" from the ISS is that ammonia is a lot of trouble. The toxic atmosphere drills and training is costly. https://www.forbes.com/sites/quora/2013/05/31/how-would-the-iss-differ-if-it-was-being-designed-today/

The Russian Orbital Segment uses silicone oil for the exterior loop. Good down to -70C. http://www.clearcoproducts.com/heat-transfer-fluids-low.html
Interesting, specific heat about 40% that of water, seems good enough.  Perhaps not the best for the Sabatier reactor.  If needed a flat plate heat exchanger might be required there.  Although oil cooling in industrial processes is a common thing so perhaps no concern?  Might become a bit massive in large cooling loops, in-situ production seems unlikely?  Here ammonia, despite its faults, might be best.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/18/2019 04:13 pm
Don't think glycols would be safe enough at -60C, so are we down to ammonia and such?

One of the "lessons learned" from the ISS is that ammonia is a lot of trouble. The toxic atmosphere drills and training is costly. https://www.forbes.com/sites/quora/2013/05/31/how-would-the-iss-differ-if-it-was-being-designed-today/

The Russian Orbital Segment uses silicone oil for the exterior loop. Good down to -70C. http://www.clearcoproducts.com/heat-transfer-fluids-low.html
Interesting, specific heat about 40% that of water, seems good enough.  Perhaps not the best for the Sabatier reactor.  If needed a flat plate heat exchanger might be required there.  Although oil cooling in industrial processes is a common thing so perhaps no concern?  Might become a bit massive in large cooling loops, in-situ production seems unlikely?  Here ammonia, despite its faults, might be best.

Bingo to the bolded bit.
Title: Re: Power options for a Mars settlement
Post by: RoboGoofers on 07/18/2019 04:23 pm
Pardon me but I've lost the thread. How is this about power options? Why the extended discussion about producing hydrogen?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/18/2019 04:33 pm
Pardon me but I've lost the thread. How is this about power options? Why the extended discussion about producing hydrogen?
Back up power and the influence of the main usage of energy( electrolysis) on production.  If hydrogen needs to be produced  at all times then night time production influences design.  Would seem it does not but Sabatier is happier in continuous mode, hence, hydrogen storage sizing and requirements for excess production capacity can be defined
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 07/18/2019 04:33 pm
Pardon me but I've lost the thread. How is this about power options? Why the extended discussion about producing hydrogen?
Demand side scaling of required power sources.
Title: Re: Power options for a Mars settlement
Post by: RoboGoofers on 07/18/2019 05:01 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.  Running continuously does not preclude throttling down when running on stored hydrogen.  In theory running at 10% throttle should be easy enough, although I haven't yet tried this myself.
If it's just about maintaining reactor temperature within a temperature range, what about just a heating element for night? If so there's no need to run electrolysis at night or store hydrogen.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/18/2019 05:23 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.  Running continuously does not preclude throttling down when running on stored hydrogen.  In theory running at 10% throttle should be easy enough, although I haven't yet tried this myself.
If it's just about maintaining reactor temperature within a temperature range, what about just a heating element for night? If so there's no need to run electrolysis at night or store hydrogen.
Running the Sabatier full time might cut down on mass overhead
Title: Re: Power options for a Mars settlement
Post by: Lar on 07/18/2019 05:39 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.  Running continuously does not preclude throttling down when running on stored hydrogen.  In theory running at 10% throttle should be easy enough, although I haven't yet tried this myself.
If it's just about maintaining reactor temperature within a temperature range, what about just a heating element for night? If so there's no need to run electrolysis at night or store hydrogen.
Running the Sabatier full time might cut down on mass overhead
This is a fun set of trades to work since there are so MANY variables. Running full time either needs full time power (via battery or nuclear or wind) to produce the reactants, or large storage tanks. Every dial you turn changes every other value somehow.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/18/2019 06:51 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.  Running continuously does not preclude throttling down when running on stored hydrogen.  In theory running at 10% throttle should be easy enough, although I haven't yet tried this myself.
If it's just about maintaining reactor temperature within a temperature range, what about just a heating element for night? If so there's no need to run electrolysis at night or store hydrogen.

The temperature we care about is the reaction temperature, not the reactor temperature.  This is a subtle but important difference.

My design/concepts use a solar thermal element to heat cooling oil to near operating temperature before startup.  This isn't ideal but it does remove most of the internal heating elements needed for startup with low catalyst degradation, freeing up space for more cooling loops.  More cooling allows higher flow rates in a given sized reactor.

Pulsating heat pipes(PHP) were chosen because these are self regulating.  If a local hot spot develops the local PHP flow rates increase, bringing the temperature back down.  Cold spots result in lower local PHP flow rates.  No internal temperature sensors are needed for reaction temperature regulation, freeing even more space for cooling loops.

I don't claim to know everything so there very well may be a good way to ensure stable reaction temperatures through startup to steady state reaction temperature without removing cooling loops for internal heating elements and sensors.  What I do know is no option I've looked into is preferable to continuous operation powered by hydrogen stored in a buffer.

While I can see how to use heating elements a sensors to keep a non-producing reactor at >300 C, this is added complexity akin to what I described above, and, requires stored energy.  I'm seeing a large penalty over using more reaction chambers loaded with heating elements and sensors to allow restarts each morning.
Title: Re: Power options for a Mars settlement
Post by: ZChris13 on 07/18/2019 08:23 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.  Running continuously does not preclude throttling down when running on stored hydrogen.  In theory running at 10% throttle should be easy enough, although I haven't yet tried this myself.
If it's just about maintaining reactor temperature within a temperature range, what about just a heating element for night? If so there's no need to run electrolysis at night or store hydrogen.
-snipped for readability-
While I can see how to use heating elements a sensors to keep a non-producing reactor at >300 C, this is added complexity akin to what I described above, and, requires stored energy.  I'm seeing a large penalty over using more reaction chambers loaded with heating elements and sensors to allow restarts each morning.
So as I read this, there are three options:
1. Run continuously, even if at a reduced rate overnight, off of
   a. a hydrogen buffer
   b. stored energy to keep the hydrogen production running
2. Heating elements to bring the reactor up to operating temperature before startup every Sol you're not in a dust storm severe enough to curtail production
3. Deal with catalyst degradation from cold starts
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/18/2019 09:36 pm
Note on the last assumption:  The key to avoiding Sabatier reactor catalyst degradation is maintaining constant temperature.  This means keeping the reactor running continuously.  Running continuously does not preclude throttling down when running on stored hydrogen.  In theory running at 10% throttle should be easy enough, although I haven't yet tried this myself.
If it's just about maintaining reactor temperature within a temperature range, what about just a heating element for night? If so there's no need to run electrolysis at night or store hydrogen.
-snipped for readability-
While I can see how to use heating elements a sensors to keep a non-producing reactor at >300 C, this is added complexity akin to what I described above, and, requires stored energy.  I'm seeing a large penalty over using more reaction chambers loaded with heating elements and sensors to allow restarts each morning.
So as I read this, there are three options:
1. Run continuously, even if at a reduced rate overnight, off of
   a. a hydrogen buffer
   b. stored energy to keep the hydrogen production running
2. Heating elements to bring the reactor up to operating temperature before startup every Sol you're not in a dust storm severe enough to curtail production
3. Deal with catalyst degradation from cold starts

Basically. 

Any startup needs a heat source at the leading edge initiating the reaction.  This is where we want to definitely use ruthenium(must be sourced from Earth for the foreseeable future).  After that it is a series of complex trades.

When I do my trade studies for Mars one factor I consider is how does a specific technology enable development of Martian industry.  This is why I mentioned ammonia production.  I don't want to give away all of my secrets but the nickel foam I favor for most Sabatier reactor catalyst mass and the metal in metal hydride hydrogen storage is actually marketed for use in batteries as a substrate or electrode base.  If we use CO instead of CO2 we can make methanol using our Sabatier reactor.  Producing other metallic foams using the same production line is possible with a little foresight.  The various supply chains that various power options enable are overly broad for this particular thread.  We should acknowledge they exist though.  After all, these industries will need power as well.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 12:52 am
What I like about illustrating things in containers is that it's all lettering  :)

Do these seem about the correct size?  A 22 foot container, a 12 foot container and a cooler.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 02:06 am
Added the hydrogen tanks.  COPV, 60 Bar, french fabrication.  850 L each. See the datasheet joined.  A bit more than required, perhaps.

Made the Sabatier box a little bigger too.

This would be for the production of a single Starship; double the number for two.

Water tanks are elsewhere in the colony, methane and oxygen go to the Starship.

The cooler is a pure guess.  Forced convection will work on Mars, after all.  If required, I guess it might be some kind of adiabatic cooler.  Anyway, it should be idle part of the time as a lot of the heat will go to the colony.

This set would go to Mars on mission two.  Mission one would have a much smaller set, for demonstration purposes, perhaps a single cell.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 02:10 am
The Sabatier container looks about right if it's an 6 foot long x 6 foot wide x 8 foot high box, considering a person in a pressure suit will need room to be able to service components.  Your comment says 12 foot though.  That would put the height at ~18 feet.  I'm confused.

I'm assuming you've elected to depict battery storage, reverse osmosis, and chillers in the same container with the electrolysis units due to the very large size of the electrolysis container.  I don't get the choices, but the size roughly matches up with your 22 foot long figure.

I don't get why the cooler is there.  Why not dump low grade waste heat into the water storage tank instead?

Edit to reflect the new render with the hydrogen tanks:

910 liter metal hydride storage only requires a 4.5 inch diameter, 11.3 inch long tank.  https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/cl-910-metal-hydride

Even better, metal hydrides do not need a compressor.  Does it make sense why I don't use tanks yet?

Edit 2: Missed the pressure of 60 bar.  I'd like to see the compressor needed to fill these bad boys.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 02:20 am
The Sabatier container looks about right if it's an 6 foot long x 6 foot wide x 8 foot high box, considering a person in a pressure suit will need room to be able to service components.  Your comment says 12 foot though.  That would put the height at ~18 feet.  I'm confused.

I'm assuming you've elected to depict battery storage, reverse osmosis, and chillers in the same container with the electrolysis units due to the very large size of the electrolysis container.  I don't get the choices, but the size roughly matches up with your 22 foot long figure.

I don't get why the cooler is there.
 Why not dump low grade waste heat into the water storage tank instead?
Standard container sizes are 8 wide x 8-1/2 high x 20 feet long. 
I just assumed a cooler would be needed, even if only in backup.  In most installation I work with when waste heat is used, we don't assume the secondary usage will always be there.  I guess water heating and habitat heating might be considered as sufficiently redundant and we could do away with the cooler.

The hydrogen system is just a copy of the Areva arrangement.  I am not qualified to judge their design :-)
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 02:32 am
The Sabatier container looks about right if it's an 6 foot long x 6 foot wide x 8 foot high box, considering a person in a pressure suit will need room to be able to service components.  Your comment says 12 foot though.  That would put the height at ~18 feet.  I'm confused.

I'm assuming you've elected to depict battery storage, reverse osmosis, and chillers in the same container with the electrolysis units due to the very large size of the electrolysis container.  I don't get the choices, but the size roughly matches up with your 22 foot long figure.

I don't get why the cooler is there.
 Why not dump low grade waste heat into the water storage tank instead?
Standard container sizes are 8 wide x 8-1/2 high x 20 feet long. 
I just assumed a cooler would be needed, even if only in backup.  In most installation I work with when waste heat is used, we don't assume the secondary usage will always be there.  I guess water heating and habitat heating might be considered as sufficiently redundant and we could do away with the cooler.

The hydrogen system is just a copy of the Areva arrangement.  I am not qualified to judge their design :-)

Meanwhile I'm worried about how to keep water from freezing during dust storms.

Areva's arrangement uses a rectifier, reverse osmosis, and a chiller to dry the hydrogen gas.  The rectifier isn't needed unless we convert the DC solar panels output to AC, then convert back.  My preference is to not use the energy needed to convert solar DC to AC and back when possible.  Reverse osmosis makes sense if there isn't a giant heat source, say a Sabatier reactor, available.  I fully expect the complexity and bulk of chillers to be replaced with membranes soon enough.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 02:43 am
The Sabatier container looks about right if it's an 6 foot long x 6 foot wide x 8 foot high box, considering a person in a pressure suit will need room to be able to service components.  Your comment says 12 foot though.  That would put the height at ~18 feet.  I'm confused.

I'm assuming you've elected to depict battery storage, reverse osmosis, and chillers in the same container with the electrolysis units due to the very large size of the electrolysis container.  I don't get the choices, but the size roughly matches up with your 22 foot long figure.

I don't get why the cooler is there.  Why not dump low grade waste heat into the water storage tank instead?

Edit to reflect the new render with the hydrogen tanks:

910 liter metal hydride storage only requires a 4.5 inch diameter, 11.3 inch long tank.  https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/cl-910-metal-hydride

Even better, metal hydrides do not need a compressor.  Does it make sense why I don't use tanks yet?

Edit 2: Missed the pressure of 60 bar.  I'd like to see the compressor needed to fill these bad boys.
Is that 910 litres at standard atmospheric pressure and temperature (the little asterix)?  That's what I see in the specifications but I may be mistaken.  If so, then 100 kg of hydrogen is 100/0,08= 1300 m3 and 1 300 000 litres. At 910 litres each, I find 1300 little flasks are required.  And at 6,7 kg each that works out to 9 tonnes.  The COPV tanks are about six tonnes, so similar results?  Again, just reading the text, no expert here.

As far as the compressor goes, it's pretty low flow, so perhaps not that bad?  The Areva specs deliver the hydrogen at up to 35 bars (no idea why) so that put me onto the trace of the COPV tanks.

Joined a spreadsheet of a compressor for martian CO2, rapidly adapted for hydrogen.  May be all off, of course, but I'm finding a 10 HP compressor.  Perhaps some form of screw, but perhaps not at the very low feed rates.


Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 02:48 am
The Sabatier container looks about right if it's an 6 foot long x 6 foot wide x 8 foot high box, considering a person in a pressure suit will need room to be able to service components.  Your comment says 12 foot though.  That would put the height at ~18 feet.  I'm confused.

I'm assuming you've elected to depict battery storage, reverse osmosis, and chillers in the same container with the electrolysis units due to the very large size of the electrolysis container.  I don't get the choices, but the size roughly matches up with your 22 foot long figure.

I don't get why the cooler is there.
 Why not dump low grade waste heat into the water storage tank instead?
Standard container sizes are 8 wide x 8-1/2 high x 20 feet long. 
I just assumed a cooler would be needed, even if only in backup.  In most installation I work with when waste heat is used, we don't assume the secondary usage will always be there.  I guess water heating and habitat heating might be considered as sufficiently redundant and we could do away with the cooler.

The hydrogen system is just a copy of the Areva arrangement.  I am not qualified to judge their design :-)

Meanwhile I'm worried about how to keep water from freezing during dust storms.

Areva's arrangement uses a rectifier, reverse osmosis, and a chiller to dry the hydrogen gas.  The rectifier isn't needed unless we convert the DC solar panels output to AC, then convert back.  My preference is to not use the energy needed to convert solar DC to AC and back when possible.  Reverse osmosis makes sense if there isn't a giant heat source, say a Sabatier reactor, available.  I fully expect the complexity and bulk of chillers to be replaced with membranes soon enough.
I agree about the rectifier.  Makes no sense with modern electronics to convert to AC.  I've been asking around for information about systems at 6 or 7000V DC for transportation in a large colony but no info yet.
My guess is that the whole system would be at 480V DV, directly connected to the panels, with some kind of load management, of course. So yes, no more rectifier.  Eventually we'll get the whole system for two ships into a single container!

I think you've mentioned evaporation with waste heat rather than reverse osmosis?  From the Sabatier?
 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 02:54 am
The Sabatier container looks about right if it's an 6 foot long x 6 foot wide x 8 foot high box, considering a person in a pressure suit will need room to be able to service components.  Your comment says 12 foot though.  That would put the height at ~18 feet.  I'm confused.

I'm assuming you've elected to depict battery storage, reverse osmosis, and chillers in the same container with the electrolysis units due to the very large size of the electrolysis container.  I don't get the choices, but the size roughly matches up with your 22 foot long figure.

I don't get why the cooler is there.
 Why not dump low grade waste heat into the water storage tank instead?
Standard container sizes are 8 wide x 8-1/2 high x 20 feet long. 
I just assumed a cooler would be needed, even if only in backup.  In most installation I work with when waste heat is used, we don't assume the secondary usage will always be there.  I guess water heating and habitat heating might be considered as sufficiently redundant and we could do away with the cooler.

The hydrogen system is just a copy of the Areva arrangement.  I am not qualified to judge their design :-)

Meanwhile I'm worried about how to keep water from freezing during dust storms.

Areva's arrangement uses a rectifier, reverse osmosis, and a chiller to dry the hydrogen gas.  The rectifier isn't needed unless we convert the DC solar panels output to AC, then convert back.  My preference is to not use the energy needed to convert solar DC to AC and back when possible.  Reverse osmosis makes sense if there isn't a giant heat source, say a Sabatier reactor, available.  I fully expect the complexity and bulk of chillers to be replaced with membranes soon enough.

Keeping the whole base from freezing during a dust storm is also a problem!  I've been tempted to create large habitats and put everything into them.  Solving all the pesky heat and pressure questions and allowing direct use of Earth equipment.  Then you just cool the habitats, and we know how to do that.  Hard to decide which is easier.

Otherwise I see no end of heat tracing, radiant heaters, hermetic this and that and complexities of design.  But I may be overthinking all this.  A common failing of my part :D

Title: Re: Power options for a Mars settlement
Post by: CameronD on 07/19/2019 03:30 am
I agree about the rectifier.  Makes no sense with modern electronics to convert to AC.  I've been asking around for information about systems at 6 or 7000V DC for transportation in a large colony but no info yet.
My guess is that the whole system would be at 480V DV, directly connected to the panels, with some kind of load management, of course. So yes, no more rectifier.  Eventually we'll get the whole system for two ships into a single container!

If you're looking to distribute electrical power to a large colony, it actually makes a lot of sense to convert to AC - "modern electronics" has nothing to do with it.  HVDC means (very) large switchgear and higher heat losses with no easy means for going up and down in voltage to reduce the size and mass of your cables over long distances (a simple transformer won't work).  HVDC has advantages for point-to-point power transmission, but not for multiple consumers around a colony because "some kind of load management" actually requires some kind of rectifier/electronics stage to control it.

Another aspect to consider is connection with existing electronics:  For various reasons ISS uses 120VDC and many aircraft systems use 400Hz AC.  IMHO, whatever gets used up there will be somewhere around this.
Title: Re: Power options for a Mars settlement
Post by: groundbound on 07/19/2019 03:32 am

I agree about the rectifier.  Makes no sense with modern electronics to convert to AC. 

I have to quibble just a little with the assumption above. It is no longer 1985. Rectifiers can be made arbitrarily efficient and reliable for negligible cost for any system you are going to put on Mars. Furthermore they are everywhere and you can't get rid of them.

If all the architectural decisions favor DC, then sure,  rectifiers are just an unnecessary addition. But if you are going to ever change from one DC voltage to another, then it will go through a rectifier. Voltage converters contain them by necessity.

Of course none of this changes anything about system architectures. I'm just saying that rectifiers are a complete distraction. They just don't matter.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 06:57 am
I finally tracked down an image that shows an Areva gas skid in enough detail to be useful.  I'm still not quite sure how to properly upload someone else's image so I'm just going to link the PDF.

http://surfacefest.org/pastworkshops/2016/O12-H-PEM-electrolysis.pdf

One image we are very interested in is on page 7.  The gas skid is the larger section on the right.  One thing we can see is this has a lot of unused volume.  This isn't a problem on terrestrial container ships.  Cutting down on empty volume is far more important on Starship.  We can also see that there are a lot of little bits needed to support the two separator tanks.  Replacing most of these bits and the separator tanks with membranes will save a nice chunk of mass, volume, and complexity.  These savings extend to the electrical cabinet as well.

Is that 910 litres at standard atmospheric pressure and temperature (the little asterix)?  That's what I see in the specifications but I may be mistaken.  If so, then 100 kg of hydrogen is 100/0,08= 1300 m3 and 1 300 000 litres. At 910 litres each, I find 1300 little flasks are required.  And at 6,7 kg each that works out to 9 tonnes.  The COPV tanks are about six tonnes, so similar results?  Again, just reading the text, no expert here.

I did mention throttling at night is an option.  If we're running at 10% when electrolysis isn't running that 100 kg drops to 10 kg, taking the buffer mass down to ~900 kg.

Another mass savings option is to use bigger flasks.  As is usually the case "dry mass" doesn't scale linearly.  For example, if we use the 20 liter model we'd need 14 kg to store what the 910 liter model can store in only 6.7 kg.  Bump the storage capacity up by another ~50 times and we're down in the 5 tonne range to store 100 kg.

Metal hydrides are exothermic when filling and endothermic when emptying.  We can use waste heat from the Sabatier reactor during discharge.  The waste heat during filling can be used during distillation(see below).

Quote
As far as the compressor goes, it's pretty low flow, so perhaps not that bad?  The Areva specs deliver the hydrogen at up to 35 bars (no idea why) so that put me onto the trace of the COPV tanks.

I thought so as well, until I started looking to buy a hydrogen compressor.  These things are very difficult to build if we don't want them leaking like a sieve.

Delivering high pressure from electrolysis avoids having a compressor in most applications.  The 35 bar output is a selling point in favor of Areva's system.

I agree about the rectifier.  Makes no sense with modern electronics to convert to AC.  I've been asking around for information about systems at 6 or 7000V DC for transportation in a large colony but no info yet.
My guess is that the whole system would be at 480V DV, directly connected to the panels, with some kind of load management, of course. So yes, no more rectifier.  Eventually we'll get the whole system for two ships into a single container!

I don't know much about this, but I do know there is an arcing problem due to the nature of the Martian atmosphere.

Quote
He didn’t elaborate on the details of the instrument problem but said it had to do with a high-voltage power supply for its laser. “If I could convey one message to the science community, it is to think deeply about high-voltage power supplies on Mars, because they have been a real problem for us,” he said. “Mars is a terrible environment for such voltages, so we have trouble with arcing.”

https://spacenews.com/mars-2020-instrument-survives-termination-review/

Quote
I think you've mentioned evaporation with waste heat rather than reverse osmosis?  From the Sabatier?

Distillation.  The Sabatier reactor is a ~350 C heat source.  We can use this heat to boil water, then use a cooling loop to condense the steam.  Impurities are left behind during the process.  Bootleggers use this tech all the time to purify their moonshine.  Martian maintenance crews will have no problem fixing this system when it breaks. 

Reverse osmosis is great tech.  This isn't tech a Martian settlement will be able to maintain without a steady stream of replacement parts from Earth for the foreseeable future.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 01:03 pm
I agree about the rectifier.  Makes no sense with modern electronics to convert to AC.  I've been asking around for information about systems at 6 or 7000V DC for transportation in a large colony but no info yet.
My guess is that the whole system would be at 480V DV, directly connected to the panels, with some kind of load management, of course. So yes, no more rectifier.  Eventually we'll get the whole system for two ships into a single container!

If you're looking to distribute electrical power to a large colony, it actually makes a lot of sense to convert to AC - "modern electronics" has nothing to do with it.  HVDC means (very) large switchgear and higher heat losses with no easy means for going up and down in voltage to reduce the size and mass of your cables over long distances (a simple transformer won't work).  HVDC has advantages for point-to-point power transmission, but not for multiple consumers around a colony because "some kind of load management" actually requires some kind of rectifier/electronics stage to control it.

Another aspect to consider is connection with existing electronics:  For various reasons ISS uses 120VDC and many aircraft systems use 400Hz AC.  IMHO, whatever gets used up there will be somewhere around this.
Depends when and where, really.  120 V DC is fine for a while, but not for 1 MW, I expect.  30 000 Amps is just too  many amps.  My understanding is that Tesla power systems operate at up to 480V DC, to allow for rapid charging and that would seem fine for most needs for quite some time.  But still, that's 8000 Amperes.  And if the peak production load is a solar powered system, it's more like 6 MW of infrastructure that will be required to fuel 2 Starships.

So we want to minimize the mass of that infrastructure.  Shorts distribution paths and localised use.
The limitations of HVDC are the reason I'm wondering about mid-voltage DC.  I worked on the power stations for the new HVDC lines from Labrador to Newfoundland, so I saw just how large these systems are.  But these are sized to power a whole province!  What I'm wondering about is MW type systems.  Admittedly, if we want to implement low mass superconducting AC transformers Mars would be the place to do it.

Tesla power centers are sized for 625 kVa (from their web site) and can be used for solar, so we might want to size the H2 generator modules for a bit less than that.  That would be an Elyte E60 at 480 kVa, producing 60 Nm3/hr.  The two rectifiers (one in the Ariva module, one in the Tesla module) should probably be combined into a single unit, as there would be no need to transform to AC, but still need for control, switching, voltage adjustment, protection and all that.
600 kVA, 600 kW peak, is about 3000 m2 of panels, or 4-8000 kg.  Plus the Sabatier unit and the H2 storage, that would be a single production line.  The outputs would be 12 m3/h of low grade heat in water from the H2 unit, and 3,8 kJ/kg of higher grade heat  from the Sabatier in oil.  The hydrogen would be 4,8 kg/h for 12 hours, and methane  production would be 230 kg per day, or 9,6 kg/h for 24 hours.  So hydrogen might be sized for about 4,8 x 6 = 28,8 kg.

Going to have to make a formal spreadsheet of this  :) But six(?) of these lines would be required at least, and if the dust situation is bad, perhaps up to twelve(?).

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 02:49 pm
We used reverse osmosis in isolated mining construction camps, but admittedly,  flying to northern Canada is not the same as flying to Mars! Although replacement membranes cannot be that heavy?

Joined is a flyer from a hydrogen compressor supplier.  Does look like an expensive piece of equipment!  The PDC-PLW-60-22 looks interesting, but as you mention if the production cell can just run out gas at higher pressure, would be just as well do do without altogether.

Hydrogen in vehicles is really at high pressure,  700 bar!  That must cut down on tank size, at the cost of a big compressor.  for our use I expect we would want to reduce compression as much as possible.  Perhaps 30 Bar tanks would be lighter than 60 bar tanks, even if we need more of them?

Mahytek has some nice metal hydride tanks.  200 grams in 22 kg tanks.  About 11 tonnes for 100 kg of H2.
Title: Re: Power options for a Mars settlement
Post by: RoboGoofers on 07/19/2019 02:57 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 03:04 pm
Another solution, high pressure vehicle type 4 tanks.
500 bar, 260kg, stores 9.5 kg.  So about 3 tonnes for 100 kg.  Lightest yet, but we need to add the high pressure compressor.  This is for cars, so should be safe.
This compressor doesn't quite make it pressure wise, but has a higher volume flow rate, so might trade that for pressure in a similar design.  800 kg.  So this might be the winning package?  About 4 tonnes?
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/19/2019 03:14 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.
As someone who is actually designing a (admittedly only 12kWp) solar/battery system, it's not an issue.

Modern AC/DC converters are much, much smaller with lower power losses than they were.
And you need DC/DC converters anyway for the solar panels to make them all play together.

You will in any case not be using AC transformers running at 60/50hz to do the power conversion, so many of the traditional arguments in favour of AC go away, as voltage conversion is no longer a synonym for 'just a hunk of iron with wire wrapped round it'.

There is no particular reason that 650VDC is particularly easier or harder than 650VAC.
There are advantages on both sides.


On the topic of tanks and high pressure hydrogen compressors, I note again that either propellant tank of the SS can easily contain 100kg of H2 at the nominal working pressure of several bar.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 03:19 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.
Transformer mass and part of the rectifier mass.  About 20% reduction in losses.  But that's 20% of 4-5% so 1% overall and perhaps not that much of a big deal.

Joined a nice study of DC systems and their use in data centers and other high load DC systems.  I think an all DC system for methane production makes sense, and distribution up to a few hundred KVA in the habitats might make sense as well.  Distribution(regional) though might be AC as there doesn't seem to be DC distribution technologies.

Don't know if HVDC transport lines on Mars would work.  At least here in Quebec our big line from the North to the US uses ground return electrodes, and that might be a problem on Mars. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 03:28 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.
As someone who is actually designing a (admittedly only 12kWp) solar/battery system, it's not an issue.

Modern AC/DC converters are much, much smaller with lower power losses than they were.
And you need DC/DC converters anyway for the solar panels to make them all play together.

You will in any case not be using AC transformers running at 60/50hz to do the power conversion, so many of the traditional arguments in favour of AC go away, as voltage conversion is no longer a synonym for 'just a hunk of iron with wire wrapped round it'.

There is no particular reason that 650VDC is particularly easier or harder than 650VAC.
There are advantages on both sides.


On the topic of tanks and high pressure hydrogen compressors, I note again that either propellant tank of the SS can easily contain 100kg of H2 at the nominal working pressure of several bar.
Yes, and that's actually an argument for the idea of just leaving the fuel production units in one of the ships, rather than moving them outside.  Then you can have them inside a nice controlled environment, with the target tanks nearby.  You just need to feed water and power to the ship, and move the waste heat out.  CO2 can come in through the window, so to speak.  Once the ship is fuelled, then you can move your containerized and skidded assemblies to another ship, and repeat.  Or if you are using the local tanks for hydrogen to save a few tonnes of mass (seems fraught with difficulties, bu the way)  you can pump the oxygen and methane to a second ship.  Seems more difficult though. 

So, the idea would be containers, but left in the ship that is being fuelled, in a Earth normal environment in the ships's cargo hold.  Once the ship is fuelled these containers can be moved to another ship.
Title: Re: Power options for a Mars settlement
Post by: Lar on 07/19/2019 04:47 pm
Why would the ship environment be earth normal? I would not expect the cargo bay to be kept pressurised once on Mars... that's a lot of gas to scavenge, compress, save, release, replenish...
Title: Re: Power options for a Mars settlement
Post by: Pete on 07/19/2019 05:41 pm
I agree about the rectifier.  Makes no sense with modern electronics to convert to AC. 

Modern electronics? DC is fine.

Modern power electrical engineering? Not a chance! You want various different voltages. You want ability to transmit over significant distances. You want AC.

Title: Re: Power options for a Mars settlement
Post by: rakaydos on 07/19/2019 05:45 pm
I agree about the rectifier.  Makes no sense with modern electronics to convert to AC. 

Modern electronics? DC is fine.

Modern power electrical engineering? Not a chance! You want various different voltages. You want ability to transmit over significant distances. You want AC.
We can do those things without converting to AC, these days.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 05:53 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.

A trade to consider is, which requires more mass/volume:

- A support structure to anchor and angle the solar panels.

- Power lines and the associated hardware to take advantage of a hillside some distance away.

My expectation is the panels on the hillside will need to be anchored.  I doubt the hillside will be naturally perfect, so some support structure will be involved.  I'm having a hard time seeing how the distant hillside is better, even if we can get away without poles for the power lines.

On the topic of tanks and high pressure hydrogen compressors, I note again that either propellant tank of the SS can easily contain 100kg of H2 at the nominal working pressure of several bar.

I need to be convinced the seals are up to the task.  The tanks should be good, at least until the hydrogen embrittlement attacks the welds.  My big concern is the excessive size of the tanks.  My opinion is using these tanks for methane, oxygen, carbon dioxide, nitrogen, and argon should come first.

---------------

As to that compressor,

Quote
The DM-Series is engineered and tested for a long service life and uncomplicated maintenance. Thanks to magnetic coupling design, the compressor block can be easily dismounted and replaced on site in less than a half a day. The dismounted compressor block will then be refurbished in the factory to guarantee the shortest downtime and maximum availability.

Shipping back to the factory on Earth for refurbishment is going to be problematic.  Unsurprisingly I'm not seeing anything about expected maintenance cycles or the refurbishment process on Atlas Copco's website.

I would like to reiterate that one of the advantages of going with metal hydride hydrogen storage is we can use the same tooling we use to repair/refurbish the Sabatier reactor.

It occurs to me there may be common tooling for refurbishing methane and oxygen liquefaction equipment.  If so, this would eliminate one problem set with using a compressor and tanks for hydrogen storage.  The "small" natural gas liquefaction systems I've found so far are scaled for roughly one Starship per day.  This strikes me as two orders of magnitude overkill, and definitely too large for a hydrogen buffer, so I'll keep looking.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/19/2019 06:11 pm
I agree about the rectifier.  Makes no sense with modern electronics to convert to AC. 

Modern electronics? DC is fine.

Modern power electrical engineering? Not a chance! You want various different voltages. You want ability to transmit over significant distances. You want AC.
This argument presumes 50/60Hz and large power transformers.

When all of your transformers are running at >>50KHz, this argument is irrelevant, and the only argument for AC is that it may make arcs extinguish in some conditions easier.
DC is _NOT_ any harder to change voltages with any more. And may arguably be easier.

I note that a 500kW class distribution transformer weighs pretty much exactly the same as a Tesla with a 500kW three-phase DC-AC converter.
The actual DC-AC converter is ~40kg.

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/19/2019 06:30 pm
Why would the ship environment be earth normal?

Who said Earth normal? Lamontagne said "nice controlled environment."

I would not expect the cargo bay to be kept pressurised once on Mars... that's a lot of gas to scavenge, compress, save, release, replenish...

No need to keep it pressurized. This cycle would only be necessary if you needed to do maintenance in a shirt-sleeve environment (a nice capability btw), not all the time.

I presume that on the Mars surface the cargo area can act as a contingency airlock (with greater pump-down time and energy), while the central "turbolift" cylinder holds the primary airlock. If that's true then the necessary hardware is already on Starship.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 06:49 pm
Why would the ship environment be earth normal? I would not expect the cargo bay to be kept pressurised once on Mars... that's a lot of gas to scavenge, compress, save, release, replenish...
To keed development costs and times as low as possible.  If Earth normal conditions are maintained, Earth normal equipment could be used.  It would have to be tested for temporary exposure to Martian conditions though, and analysed for low gravity operations, but that's not the same as operating on Mars.
If we purge a 200m3 cargo bay, that 200 kg of air.  And we would just compress it, not throw it away. 

It a trade off again, how much do we save doing minimum adaptation, vs adapting equipment to Mars.
Of course doing Mars adaptations might become a speciality, with Mars rated control and power equipment and shop specializing in couversions, rather like sea rated equipment today.  It looks superficially like standard equipment, but has any number of adaptations due to corrosion resistance and environmental constraints.

Perhaps if someone in aeronautics can tell us if the equipment in the aircraft is mostly at exterior or interior pressure?  Or is it not even an issue?  At 30 000 feet you're getting close to Martian conditions.  If all the electronics and power are just fine, then I guess Mars rating may not be all that much of a problem.

And you will never be able to fully pressurize a container for maintenance, but you can pressurize Starship (I hope!  How should I know really  :).

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/19/2019 06:55 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.

A trade to consider is, which requires more mass/volume:

- A support structure to anchor and angle the solar panels.

- Power lines and the associated hardware to take advantage of a hillside some distance away.

or...

- Selecting a better site where the hillside is closer to the colony.

We literally have a whole planet to choose from. This should be possible, even in the presence of additional site constraints.


Shipping back to the factory on Earth for refurbishment is going to be problematic.

Obviously in this case you would bring spares instead.

Edit: and/or (if possible) package up any custom factory refurbishment tools into a kit so it can be refurbed on Mars.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 07:09 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.

A trade to consider is, which requires more mass/volume:

- A support structure to anchor and angle the solar panels.

- Power lines and the associated hardware to take advantage of a hillside some distance away.

- Selecting a better site where the hillside is closer to the colony.

We literally have a whole planet to choose from. This should be possible.

We could always terrace part of a hillside for the propellant plant.  This would completely eliminate the extra mass needed for power lines and associated bits.  That wasn't the comment I responded to though.  The comment I responded to had the solar panels 1 km away.

Quote
Shipping back to the factory on Earth for refurbishment is going to be problematic.

Obviously in this case you would bring spares instead.

Have I not been clear that one of my considerations is how to transition to Martian industry?  Shipping an even expanding set of spare parts is problematic.  Shipping a factory that can make the spare parts locally solves this problem.

I went slightly off-topic posting other uses for high purity nickel and nickel foam because I think it's relevant.

Edit: Fixed quotes.
Edit/Lar: Fixed snark.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 07:10 pm
No actual experience but this slightly biased Wikipedia article about Diaphragm compressors for hydrogen puts major maintenance at 10 times the one of classic reciprocating compressor.  So perhaps 40 -50 000 hours so at least two synods,  Not so bad. https://en.wikipedia.org/wiki/Diaphragm_compressor.

I'm beginning to think that the hydrogen aspect is already pretty advanced, with multiple suppliers, and that the Sabatier part may be the more magical item.

This looks a bit like vaporware, for example: https://www.atmostat-alcen.com/en/methanation/methamodr-0



Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/19/2019 07:18 pm

Have I not been clear that one of my considerations is how to transition to Martian industry?  Shipping an even expanding set of spare parts is problematic.  Shipping a factory that can make the spare parts locally solves this problem.


Perhaps for a while we may depend on some spare parts?  As this discussion is mostly analysed in the optics of SpaceX, one tonne of critical spare parts at a few hundred dollars per kg will not be all that expensive.  And although I hate to depend on a meme, additive manufacturing should be helpful for parts.




Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/19/2019 07:29 pm
What's wrong with AC? no need to jump through hoops to avoid it. It'll be used where appropriate. The solar farm would benefit from AC to minimize resistance power losses. With AC it can be a km away on a adequate slope instead of right next to the colony.

A trade to consider is, which requires more mass/volume:

- A support structure to anchor and angle the solar panels.

- Power lines and the associated hardware to take advantage of a hillside some distance away.

- Selecting a better site where the hillside is closer to the colony.

We literally have a whole planet to choose from. This should be possible.

We could always terrace part of a hillside for the propellant plant.  This would completely eliminate the extra mass needed for power lines and associated bits.

Terracing isn't free either, so now we have another trade.

That wasn't the comment I responded to though.  The comment I responded to had the solar panels 1 km away.

Yes, and I'm saying that whole scenario is unrealistic.

Edit: just to expand on this, the scenario is essentially "should we do X easy and Y hard, or X hard and Y easy?" But there's no clear reason why we're excluding "do X easy and Y easy," which seems like the obvious winner.

Shipping back to the factory on Earth for refurbishment is going to be problematic.

Obviously in this case you would bring spares instead.

Have I not been clear that one of my considerations is how to transition to Martian industry?

It will be interesting to see how much actual Martians care about this.

Fundamentally it comes down to ideological purity vs. practical cost considerations. Obviously in any issue where those happen to align, there's no problem.

Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 08:29 pm

Have I not been clear that one of my considerations is how to transition to Martian industry?  Shipping an even expanding set of spare parts is problematic.  Shipping a factory that can make the spare parts locally solves this problem.


Perhaps for a while we may depend on some spare parts?  As this discussion is mostly analysed in the optics of SpaceX, one tonne of critical spare parts at a few hundred dollars per kg will not be all that expensive.  And although I hate to depend on a meme, additive manufacturing should be helpful for parts.

The first couple synods should definitely rely on imported spare parts.  After that it is a question how soon local demand can justify importing production capability.  Starting with hardware that is part of that demand is a very good thing in my opinion. 

Additive manufacturing is what we want to use to create micro channel walls with embedded pulsating heat pipes.  The printed material should be a metal that conducts heat very well and is stable in the presence of the cooling oil chosen.  This is then protected by plating the outside of the component with a thin layer of nickel.  This layer can be deposited via the Mond process.  Using nickel creates additional surface area for the Sabatier reaction.  The rough finish from additive manufacturing is a benefit in this case, as it increases the surface area coated by nickel.

No actual experience but this slightly biased Wikipedia article about Diaphragm compressors for hydrogen puts major maintenance at 10 times the one of classic reciprocating compressor.  So perhaps 40 -50 000 hours so at least two synods,  Not so bad. https://en.wikipedia.org/wiki/Diaphragm_compressor.

I'm beginning to think that the hydrogen aspect is already pretty advanced, with multiple suppliers, and that the Sabatier part may be the more magical item.

This looks a bit like vaporware, for example: https://www.atmostat-alcen.com/en/methanation/methamodr-0

Diaphragm compressors have their advantages, but they still have extra mechanical bits, an extra cooling loop, and require far higher pressures.  All these extra bits are more things that can break.  I understand the companies that have patents on their versions of the bits wanting to sell their products.  We don't have to restrict ourselves to buying those bits though.

The same applies for complex chillers versus membranes.

You're right about the lack of fit-for-purpose Sabatier reactors on the market.  I've spent a lot of time looking over the last few years.  Most of what I've found are small system best described as similar to what is used in ISS' ECLSS.

The METAMOD® description is very limited but I can make an educated guess as to what they've done.  It seems like they've pressed plates covered in catalyst dust to the walls of a micro channel design.  The micro channels contain cooling channels, possible similar to those I described above.  The primary problem I had when I investigated this style is the catalyst debonding from the active plate.  Debonding catalysts result in local cold spots forming new boundary layers inside the micro channels.

Unfortunately we don't have flow rates, catalyst type, or maintenance period data.  On the bright side the box is similar in size to your rendering.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 08:57 pm

Terracing isn't free either, so now we have another trade.

Yes, we have another trade.  This tends to happen when we skirt primary considerations like proximity to the spaceport and a water supply that won't undermine the spaceport when we extract water.

Quote
That wasn't the comment I responded to though.  The comment I responded to had the solar panels 1 km away.

Yes, and I'm saying that whole scenario is unrealistic.

Edit: just to expand on this, the scenario is essentially "should we do X easy and Y hard, or X hard and Y easy?" But there's no clear reason why we're excluding "do X easy and Y easy," which seems like the obvious winner.

I don't see the nearest fit-for-purpose hillside being 1 km away from the optimal site between the spaceport and water supply being unrealistic.  I see a case study with an additional variable, Z, where Z could be very hard if we put our propellant plant in the wrong place.  For the purposes of this comment Z is either the difficulty of transporting water to the propellant plant or transporting methalox to the spaceport.

Quote
It will be interesting to see how much actual Martians care about this.

Fundamentally it comes down to ideological purity vs. practical cost considerations. Obviously in any issue where those happen to align, there's no problem.

People generally like having jobs.  This most likely won't change when the people are living on Mars.  The technology I am discussing is part of the supply chain for a wide variety of other jobs.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/19/2019 09:47 pm

Terracing isn't free either, so now we have another trade.

Yes, we have another trade.  This tends to happen when we skirt primary considerations like proximity to the spaceport and a water supply that won't undermine the spaceport when we extract water.

Who says we're skirting them?

That wasn't the comment I responded to though.  The comment I responded to had the solar panels 1 km away.

Yes, and I'm saying that whole scenario is unrealistic.

Edit: just to expand on this, the scenario is essentially "should we do X easy and Y hard, or X hard and Y easy?" But there's no clear reason why we're excluding "do X easy and Y easy," which seems like the obvious winner.

I don't see the nearest fit-for-purpose hillside being 1 km away from the optimal site between the spaceport and water supply being unrealistic.  I see a case study with an additional variable, Z, where Z could be very hard if we put our propellant plant in the wrong place.  For the purposes of this comment Z is either the difficulty of transporting water to the propellant plant or transporting methalox to the spaceport.

To quote myself, "We literally have a whole planet to choose from. This should be possible, even in the presence of additional site constraints."


It will be interesting to see how much actual Martians care about this.

Fundamentally it comes down to ideological purity vs. practical cost considerations. Obviously in any issue where those happen to align, there's no problem.

People generally like having jobs.  This most likely won't change when the people are living on Mars.

And economic regions don't manufacture things if they don't have a competitive advantage over importing them. This won't change if the economic region is Mars.

The technology I am discussing is part of the supply chain for a wide variety of other jobs.

That's not the only factor in the build vs. import tradeoff. Either way, you're still going with whichever option is cheaper (in the total value sense, not just sticker price). To the extent that that factors into total value it matters, but it's not an overriding concern.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/19/2019 10:34 pm
SNIP

That has no bearing on the build vs. import tradeoff. Either way, you're still going with whichever option is cheaper (in the total value sense, not just sticker price). To the extent that that factors into total value it matters, but it's not an overriding concern.

I've been laying out the case for why Martian nickel production makes sense.  If you want to continue ignoring that case, have a good day.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/19/2019 11:47 pm
SNIP

That has no bearing on the build vs. import tradeoff. Either way, you're still going with whichever option is cheaper (in the total value sense, not just sticker price). To the extent that that factors into total value it matters, but it's not an overriding concern.

I've been laying out the case for why Martian nickel production makes sense.  If you want to continue ignoring that case, have a good day.

Not ignoring it at all, just trying to keep it in perspective.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/20/2019 01:15 am
SNIP

That has no bearing on the build vs. import tradeoff. Either way, you're still going with whichever option is cheaper (in the total value sense, not just sticker price). To the extent that that factors into total value it matters, but it's not an overriding concern.

I've been laying out the case for why Martian nickel production makes sense.  If you want to continue ignoring that case, have a good day.

Not ignoring it at all, just trying to keep it in perspective.

I've touched on both the short and long term benefits.  Your vague retort doesn't give me anything to work with.  What are the problems with the big picture I am attempting to describe?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/20/2019 02:02 am
SNIP

That has no bearing on the build vs. import tradeoff. Either way, you're still going with whichever option is cheaper (in the total value sense, not just sticker price). To the extent that that factors into total value it matters, but it's not an overriding concern.

I've been laying out the case for why Martian nickel production makes sense.  If you want to continue ignoring that case, have a good day.

Not ignoring it at all, just trying to keep it in perspective.

I've touched on both the short and long term benefits.  Your vague retort doesn't give me anything to work with.  What are the problems with the big picture I am attempting to describe?

If you want to justify making it on Mars, it would help to have some cost numbers making that case. VI/VO.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 03:46 am
To get back to power, here is a flow, energy and mass diagram for the production of the propellant for a single Starship, during a two year period, based on the recent discussions.
I've added 50 tonnes of methane for emergency use and production losses.

The image shows one of the two production lines required per Starship.  Astronaut gives a bit of scale.

And i'll throw in a scaled image of the overall base, showing the solar panels.

I'm leaving the cooler in the image for the moment until I work out all the use cases for the heat, but the cooler mass is not there.

BTW nickel has about the same embodied energy as aluminium, so
Nickel   180-200 MJ/kg
Aluminum   190-230 MJ/kg

While the propellant has about 167 MJ/kg of methane.  Since the base might be producing the propellant for two Starships plus reserves, I.E 600 tonnes of methane, the production of 1 tonnes of nickel would require  about 1:400 of the energy produced per synod.  It might be an artisanal process, but it seems to fit into the power budget if such a production is required.

Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/20/2019 07:56 am

While the propellant has about 167 MJ/kg of methane.  Since the base might be producing the propellant for two Starships plus reserves, I.E 600 tonnes of methane, the production of 1 tonnes of nickel would require  about 1:400 of the energy produced per synod.  It might be an artisanal process, but it seems to fit into the power budget if such a production is required.

Thank you for this number.  It is nice to see someone else see nickel production isn't an energy hog we need to stress over for the purposes of this thread.

Now about that hydrogen storage...

As I've mentioned before, 10 kg daily storage per Starship per synod should be sufficient to prevent Sabatier reactor nickel catalyst degradation.  Metal hydrides don't require energy for a compressor to fill the tank.  Instead they need a heat sink.  This heat sink can be boiling water for the distillation unit.  Barring a few minutes near sunup and sundown this conveniently runs exactly when we need it to, while the electrolysis unit is running.  Releasing the hydrogen overnight can be done with the waste heat from the Sabatier reactor.  That 50 kWh/day is killing me because we simply don't need to use this.  The 8 tonnes of pressurized tanks + 1 tonne compressor is also killing me for a similar reason.

As to 10 tonnes for the Sabatier reactor, I guess I really need to be able to make pretty pictures.  This is a refuel a Starship per sol scale unit, all things considered.

I have no clue why you're sticking with Areva's terrestrial grid power, tap water, heat-source-free, chiller instead of membrane, hydrogen generator as a reference for the electrolysis unit, but you are.

I don't see the liquefaction plant anywhere.  Attached is a poor quality image of what the inputs should look like.

Edit: Removed duplicate attachment.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 03:01 pm
 I had the liquefaction as a part of the Sabatier package, insofar as I had thought about it at all.

As far as reducing production during the night to reduce storage, I guess my question is by how much this would increase the mass of the Sabatier reactor, since it would have to produce at a higher rate to compensate for the shorter time?  So it might boil down to a tank vs reactor mass optimisation, more tanks or more reactor depending on unit mass.

So the Sabatier reactor is at 300-400C, but has few thermal losses and all the 165 kJ/mole is in the water and the CH4 temperature, plus some H2?  And the whole mess is output from the reactor in a mixed stream of gas?  Guess you have to condensate out the water, then the methane and feed the h2 gas back to the reactor?

Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/20/2019 03:38 pm
So the Sabatier reactor is at 300-400C, but has few thermal losses and all the 165 kJ/mole is in the water and the CH4 temperature, plus some H2?  And the whole mess is output from the reactor in a mixed stream of gas?  Guess you have to condensate out the water, then the methane and feed the h2 gas back to the reactor?
I assume there is a nonzero amount of CO2 as well in the output.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 04:33 pm
Not quite complete but getting there?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 05:10 pm
Added compression power for methane and Oxygen.  Not so bad.

Basically, this is an electrolytic process; all the rest is accessories.
And it pretty much defines the colony power structure, 90% of the power ressources will go to propellant production.  And that's only if all the ships do not return, at least in the early years.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 05:45 pm
Here we go, all that work put to good use, I hope :-)

https://marspedia.org/Sabatier/Water_Electrolysis_Process

mr. Peterson should appreciate the link to nickel, I hope  ;D
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 07/20/2019 06:08 pm
Here we go, all that work put to good use, I hope :-)

https://marspedia.org/Sabatier/Water_Electrolysis_Process

mr. Peterson should appreciate the link to nickel, I hope  ;D

ISTM the article at that link needs to be corrected from mentioning the output ratio of oxygen/hydrogen to oxygen/methane, does it not?

Maybe I'm not understanding the articles rationale for mention that the methane can be converted to hydrogen?  IDK, sort of feels like it should be crisped up a bit.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 06:22 pm
Here we go, all that work put to good use, I hope :-)

https://marspedia.org/Sabatier/Water_Electrolysis_Process

mr. Peterson should appreciate the link to nickel, I hope  ;D

ISTM the article at that link needs to be corrected from mentioning the output ratio of oxygen/hydrogen to oxygen/methane, does it not?

Maybe I'm not understanding the articles rationale for mention that the methane can be converted to hydrogen?  IDK, sort of feels like it should be crisped up a bit.
Hum, I kind of did a datadump into the existing stuff and added my own mistakes, it would seem!!

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 06:45 pm
Here we go, all that work put to good use, I hope :-)

https://marspedia.org/Sabatier/Water_Electrolysis_Process

mr. Peterson should appreciate the link to nickel, I hope  ;D

ISTM the article at that link needs to be corrected from mentioning the output ratio of oxygen/hydrogen to oxygen/methane, does it not?

Maybe I'm not understanding the articles rationale for mention that the methane can be converted to hydrogen?  IDK, sort of feels like it should be crisped up a bit.
Thanks! Corrected.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/20/2019 07:12 pm
As far as reducing production during the night to reduce storage, I guess my question is by how much this would increase the mass of the Sabatier reactor, since it would have to produce at a higher rate to compensate for the shorter time?  So it might boil down to a tank vs reactor mass optimisation, more tanks or more reactor depending on unit mass.

The simplistic answer is Sabatier reactor mass increases by 24/(10 + 14*10%), or 24/11.4.  There are a lot of ways to tweak the design to drop this penalty to less than 2.  For purposes of what follows we'll assume the mass penalty is 2.

Design choices play a huge roll in determining the mass of a Sabatier reactor.  To illustrate let us consider a pressure vessel that uses 8 inch(219.075 mm) diameter 316L-80S pipe that masses 64.6 kg/meter.  Doubling the volume per meter of pipe can be done by using an 11.3 inch pipe.  11.3 inches isn't a standard size so we'll go with the mass for a 12 inch pipe, or 97.4 kg/m. 

https://titanium-stainless-steel.continentalsteel.com/viewitems/stainless-steel-pipes/stainless-steel-pipe--type-316l-schedule-80s (https://titanium-stainless-steel.continentalsteel.com/viewitems/stainless-steel-pipes/stainless-steel-pipe--type-316l-schedule-80s)

Scaling linearly from the figures given in Compact and Lightweight Sabatier Reactor for Carbon Dioxide Reduction  (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120016419.pdf) indicates we will need an internal volume of ~1.8 cubic meters to produce 420 kg of methane per day running at a constant flow rate.  The scaling relationship isn't actually linear but I don't have enough information to define the curve.  For now let's assume linear, knowing that our figures will be high.

Assuming the 12 inch pipe from above we need a pipe 3.57 meters long.  This doesn't account for micro channel walls which should consume ~20% of internal volume.  For safety's sake let's assume this is actually a third.  3.57*4/3 = 4.76 meters.  This means we are looking at 463 kg for the pressure vessel.

Assuming a nickel foam catalyst we're going to want a foam with a bulk density of <0.2 g/cm^3.  Neglecting recombination zones puts the maximum catalyst mass at 360 kg.

Nickel plated micro channel walls with embedded cooling channels are going to have a similar density without coolant.  We assumed about these require a third of the volume.  This puts our maximum mass at 120 kg.

I prefer to not give away all my secrets so I ask you to trust a figure of 200 kg for PHP coolant.

Summing brings us to a total of 1143 kg for the reactor that produces 420 kg of methane per day running at a constant flow rate.  As described in the beginning throttling to 10% will roughly double this figure.  Assuming we simply copy the reactor described above the Sabatier reactor mass penalty is ~1143 kg.

I want to be clear that there is a lot of heavy sandbagging involved in these calculations.  In reality 1143 kg is hundreds of kg too high.  That said, it is a decent sanity check figure.

Quote
So the Sabatier reactor is at 300-400C, but has few thermal losses and all the 165 kJ/mole is in the water and the CH4 temperature, plus some H2?  And the whole mess is output from the reactor in a mixed stream of gas?  Guess you have to condensate out the water, then the methane and feed the h2 gas back to the reactor?


That's it in a nutshell. 

Quote
I had the liquefaction as a part of the Sabatier package, insofar as I had thought about it at all.

The oxygen coming from the electrolysis unit will also be mixed with water vapor.  The Areva box you've been using doesn't contain a subsystem to dry the oxygen.  LOX and LCH4 are basically the same temperature, so we can use the same hardware to liquefy both.

Keeping the liquefaction bits out of the Sabatier package means we have a standard system we can use for other processes.  This is very handy if we want to use the Haber Bosch process to make nitrogen fertilizer for the agriculture I expect a Martian settlement to have.

-----------------------------------------

I must apologize.  I previously neglected to account for water produced in the Sabatier reactor.  This doubles hydrogen production requirements.  I know better.  My bad.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 07:35 pm

-----------------------------------------

I must apologize.  I previously neglected to account for water produced in the Sabatier reactor.  This doubles hydrogen production requirements.  I know better.  My bad.

And there is the whole point and value of these exchanges  :)


Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/20/2019 08:13 pm
Special metal hydride version!
Many tonnes saved!   ;)
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/20/2019 09:17 pm
1800 kg for the working bits and 1200 kg for an enclosure is in the ballpark.

I notice the Sabatier reactor mass was also reduced.

I'm still looking for a natural gas liquefaction system that isn't two orders of magnitude too big.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/21/2019 01:49 am
I'm still looking for a natural gas liquefaction system that isn't two orders of magnitude too big.
Air liquefaction plants may be in that range, and be mostly comparable once you remove the water and uprate the CO2 removal, as dry methane is similar to nitrogen/oxygen in nearly all properties.

I was looking at them to pull out O2/CO from the raw atmosphere a while back. (~0.2% each)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/21/2019 02:30 am
1800 kg for the working bits and 1200 kg for an enclosure is in the ballpark.

I notice the Sabatier reactor mass was also reduced.

I'm still looking for a natural gas liquefaction system that isn't two orders of magnitude too big.
Air liquide makes (made?) the TBF-80, at 2 tonnes per days seems close to what we need.   But not very much information available.
Title: Re: Power options for a Mars settlement
Post by: Lar on 07/21/2019 12:01 pm
have we worked the energy balances? Every time we have a temperature change in one direction required, we should be looking for a temperature change in the other direction that is also required.

Also the sabatier seems to be missing the output link? Or is it to the right? It might help to add arrows showing flow directions?
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/21/2019 02:03 pm
have we worked the energy balances? Every time we have a temperature change in one direction required, we should be looking for a temperature change in the other direction that is also required.
A lot of the cooling could be made rather easier if you could shovel dry ice into a hopper.
AIUI, it's likely that it will not optimise to go that far north/south though.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/21/2019 03:00 pm
have we worked the energy balances? Every time we have a temperature change in one direction required, we should be looking for a temperature change in the other direction that is also required.

Also the sabatier seems to be missing the output link? Or is it to the right? It might help to add arrows showing flow directions?
Added arrows and line weight for clarity.

About 70% of the energy goes into the propellant as chemical potential.  30% becomes waste heat.  Some of it can be reclaimed for station cooling and ice melting, but some needs to be wasted.  Melting and evaporating water ice may be the simplest way, or alternatively air coolers.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/21/2019 10:21 pm
have we worked the energy balances? Every time we have a temperature change in one direction required, we should be looking for a temperature change in the other direction that is also required.

Working the energy balances requires knowing what is needed to melt and purify Martian ice.  I believe it is reasonable to assume this will be the major heat sink we use for waste heat from the propellant plant.  What I have no clue about is how cold Martian ice is, and, what impurities it contains.

Food for thought:  We don't want to undermine the propellant plant.  Therefore the propellant plant should be some distance away from the ice mine.  It might be a good idea to pipe low grade waste heat to the ice mine.  Alternatively we might want to truck ice to the propellant plant.  Both options require power.  My gut tells me piping heat is probably preferable.  This is another trade we should consider working to find out for sure.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/26/2019 07:51 am

While the propellant has about 167 MJ/kg of methane.  Since the base might be producing the propellant for two Starships plus reserves, I.E 600 tonnes of methane, the production of 1 tonnes of nickel would require  about 1:400 of the energy produced per synod.  It might be an artisanal process, but it seems to fit into the power budget if such a production is required.

Thank you for this number.  It is nice to see someone else see nickel production isn't an energy hog we need to stress over for the purposes of this thread.

To make any build vs bring decision, you need to know how costly the total production process is. The energy cost of nickel production is a tiny fraction of the cost of these nickel foam catalysts, correct?

I don't understand why in-situ nickel production is being assumed without a quantitative economic case being made (namely, showing that the cost of producting a finished catalyst on Mars is lower than the cost of production on Earth plus shipping). So far it seems less costly to bring it from Earth.

I say this with disappointment btw, because I am certainly in the "backup of Earth's biosphere" crowd.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/26/2019 03:32 pm

While the propellant has about 167 MJ/kg of methane.  Since the base might be producing the propellant for two Starships plus reserves, I.E 600 tonnes of methane, the production of 1 tonnes of nickel would require  about 1:400 of the energy produced per synod.  It might be an artisanal process, but it seems to fit into the power budget if such a production is required.

Thank you for this number.  It is nice to see someone else see nickel production isn't an energy hog we need to stress over for the purposes of this thread.

To make any build vs bring decision, you need to know how costly the total production process is. The energy cost of nickel production is a tiny fraction of the cost of these nickel foam catalysts, correct?

I don't understand why in-situ nickel production is being assumed without a quantitative economic case being made (namely, showing that the cost of producting a finished catalyst on Mars is lower than the cost of production on Earth plus shipping). So far it seems less costly to bring it from Earth.

I say this with disappointment btw, because I am certainly in the "backup of Earth's biosphere" crowd.
Conditions will change with time.  I expect that for the first few years it will be bring, and eventually switch to make.  Nickel can be made on site for a reasonable cost.  Nickel foam may be something else again, although it doesn't look like the most complex process.  You have to be able to make polyurethane foam first though.
I don't see production as being assured, however it does seem possible if needed.  I do think there will be other priorities for a while, and that the mass of foam needed doesn't seem to be very large for quite some time.
I expect glass, steel and concrete equivalents production will see a lot more work done than nickel!
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/26/2019 03:52 pm
A question about maintenance.
Can ordinary equipment be maintained in the Martian atmosphere, in a space suit, or should we provide for all the equipment being installed in controlled environments?

Here is a view of the Sabatier and electrolytic packages installed in an expandable module, to allow for easier maintenance, as well as , perhaps, less difficult design specs.  I've also included a view of on the surface packages, for reference.

I expect we will need to design these types of modules for people anyway, labs and such so why not use them for production as well? 
These particular versions of the expandable modules have about 800 m3 of volume, so the are considerable smaller than the Bigelow 2100, and do not include radiation shielding so can be even less massive.

Title: Re: Power options for a Mars settlement
Post by: Lar on 07/26/2019 04:12 pm
I don't understand why in-situ nickel production is being assumed without a quantitative economic case being made (namely, showing that the cost of producting a finished catalyst on Mars is lower than the cost of production on Earth plus shipping). So far it seems less costly to bring it from Earth.

I say this with disappointment btw, because I am certainly in the "backup of Earth's biosphere" crowd.
Fair point. Numbers beat guesses.

That said, I'm going to guess that it might not be too bad to make it because there are a lot of nickel-iron meteorites just laying around that we want the iron out of so the nickel might be a side product.   

First synod? nope, bring it. 10th synod? might be better native. 100th synod? for sure native...

Not numeric, just guessing
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/26/2019 04:24 pm
To make any build vs bring decision, you need to know how costly the total production process is. The energy cost of nickel production is a tiny fraction of the cost of these nickel foam catalysts, correct?

I don't understand why in-situ nickel production is being assumed without a quantitative economic case being made (namely, showing that the cost of producting a finished catalyst on Mars is lower than the cost of production on Earth plus shipping). So far it seems less costly to bring it from Earth.

I say this with disappointment btw, because I am certainly in the "backup of Earth's biosphere" crowd.

I note as an aside that ~20mm nickel foam balls slightly dispersed seem very likely to be able to make reentry into Mars atmosphere at ~4km/s substantively intact. (sheparded through a 500m/s injection into mars capture orbit and a slow aerobrake before a fast entry.
Or, somewhere around 3000 tons could be carried by one starship, with ~40 retankings and ~20 lifts from earth.

Low energy ~3.8km/s departure - direct entry into atmosphere, landing over a 1km or so ellipse.

If we are assuming $5M per launch, that is of the order of $300M, or $100/kg, for refractory materials that can be surface collected. (neglecting cost of collection)

Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 07/27/2019 03:53 am
I'm still looking for a natural gas liquefaction system that isn't two orders of magnitude too big.
Air liquefaction plants may be in that range, and be mostly comparable once you remove the water and uprate the CO2 removal, as dry methane is similar to nitrogen/oxygen in nearly all properties.

I was looking at them to pull out O2/CO from the raw atmosphere a while back. (~0.2% each)

I know you’re looking for a finished package but the link below is for a home brew LN2 generator. If fed with pure CH4 or O2 instead of air it can be simplified. With an admittedly cursory read it looks practical and probably easily scaleable. SX does like to keep production in house after all.

https://www.instructables.com/id/Homemade-liquid-nitrogen-generator/ (https://www.instructables.com/id/Homemade-liquid-nitrogen-generator/)

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 07/27/2019 04:33 am
A question about maintenance.
Can ordinary equipment be maintained in the Martian atmosphere, in a space suit, or should we provide for all the equipment being installed in controlled environments?

Here is a view of the Sabatier and electrolytic packages installed in an expandable module, to allow for easier maintenance, as well as , perhaps, less difficult design specs.  I've also included a view of on the surface packages, for reference.

I expect we will need to design these types of modules for people anyway, labs and such so why not use them for production as well? 
These particular versions of the expandable modules have about 800 m3 of volume, so the are considerable smaller than the Bigelow 2100, and do not include radiation shielding so can be even less massive.

Lamontagne, I love your renders but that habitat reminds me of every dismal roach motel I’ve ever had the misfortune to stay in, but without a window. If the bathroom fan rattles it would be spot on perfect.

Phil


Edit: speeling
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/27/2019 04:34 am
Nickel foams are typically made on Earth by decomposing nickel carbonyl on a polyurethane foam base.  Here is a PDF that describes the Incofoam production process.

http://cnemcorp.com/uploads/3/2/3/6/3236864/porousmetals_metfoam_2005.pdf

Polyurethane is a product I expect a Martian biochemicals industry will begin producing within the first few synods.  Lower Martian gravity should result in more even cell formation, but testing is required to say for certain.  I'm going to guestimate five synods before we have a reliable source.  Before it makes sense to ship finished nickel foam catalysts from Earth.  After local production should be the better option.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/27/2019 05:23 am
A question about maintenance.
Can ordinary equipment be maintained in the Martian atmosphere, in a space suit, or should we provide for all the equipment being installed in controlled environments?

Here is a view of the Sabatier and electrolytic packages installed in an expandable module, to allow for easier maintenance, as well as , perhaps, less difficult design specs.  I've also included a view of on the surface packages, for reference.

I expect we will need to design these types of modules for people anyway, labs and such so why not use them for production as well? 
These particular versions of the expandable modules have about 800 m3 of volume, so the are considerable smaller than the Bigelow 2100, and do not include radiation shielding so can be even less massive.

As long as we plan enough clearance for gloved hands into the propellant plant design there is no good reason to put everything in pressure vessels.  My opinion is the best option is to use swappable modules with chunky disconnects.  The modules are then taken into a pressurized workshop when fiddly repairs are needed.

When I imagine a Martian propellant plant I picture something like NGIS ABL southwest of WV 956.  For hopefully obvious reasons they really don't like it when people stop uphill to take pictures, so hopefully Google Earth provides enough detail to see what I mean.

https://www.google.com/maps/@39.5596062,-78.8462609,648m/data=!3m1!1e3
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 07/27/2019 11:38 am
Nickel foams are typically made on Earth by decomposing nickel carbonyl on a polyurethane foam base.  Here is a PDF that describes the Incofoam production process.

http://cnemcorp.com/uploads/3/2/3/6/3236864/porousmetals_metfoam_2005.pdf

Polyurethane is a product I expect a Martian biochemicals industry will begin producing within the first few synods.  Lower Martian gravity should result in more even cell formation, but testing is required to say for certain.  I'm going to guestimate five synods before we have a reliable source.  Before it makes sense to ship finished nickel foam catalysts from Earth.  After local production should be the better option.
OT but this looks quite an interesting material for various applications.

It looks exactly like the sort of thing you'd want if you wanted to cool the skin of hypersonic aircraft, or anywhere else you wanted to bleed something into a fast flowing stream of something else.

The joker is the maximum use temperature of the underlying PU foam. For very high temperature applications you would need to graphitize the foam before Nickel deposition. That would make it a special order product. It would also likely be both rigid and brittle so you'd have to form it into the shape you wanted before the graphitization process.

That said. Intriguing. Open cell sponge with a Ni coat available OTS.
Title: Re: Power options for a Mars settlement
Post by: Lar on 07/27/2019 02:45 pm
AC in NC: A giant graphic of Marvin the Martian flipping us all off MIGHT not be exactly on topic... but it was too funny to just delete, moved it to you know where.

Joseph Peterson:  wonder why you tack bio on? Polyurethane seems more likely to come from straight chemical rather than biochemical. (but that's off topic... we had a thread somewhere talking about the possible growth in scope and number of products and production rates for the nascent martial chemical industry, starting from CH4 and NH3, both produced from atmosphere and water)

https://en.wikipedia.org/wiki/Polyurethane ... pretty complex synthesis since you need complex monomers...
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/27/2019 05:46 pm
The hard part here is how to keep close enough to on topic for this thread.

Polymerization is indeed an option.  We're starting with solar panels generating electricity, which splits water, followed by a bunch of not really topically chemical processes.

Bioplastics can start with mirrors, which reflect sunlight to genetically modified algae.

What almost certainly isn't an option is making plastic how we currently do on Earth, taking advantage of the millions of years of stored solar crude oil contains.  Remove the economies of scale the Earth petroleum industry creates and we need to reexamine the way things are done.  This is why I "tack bio on".

Title: Re: Power options for a Mars settlement
Post by: Lar on 07/27/2019 05:50 pm
The hard part here is how to keep close enough to on topic for this thread.

Polymerization is indeed an option.  We're starting with solar panels generating electricity, which splits water, followed by a bunch of not really topically chemical processes.

Bioplastics can start with mirrors, which reflect sunlight to genetically modified algae.

What almost certainly isn't an option is making plastic how we currently do on Earth, taking advantage of the millions of years of stored solar crude oil contains.  Remove the economies of scale the Earth petroleum industry creates and we need to reexamine the way things are done.  This is why I "tack bio on".


Fair enough. Feedstocks are feedstocks. But we really do have better threads for this.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/27/2019 09:45 pm
The hard part here is how to keep close enough to on topic for this thread.

Polymerization is indeed an option.  We're starting with solar panels generating electricity, which splits water, followed by a bunch of not really topically chemical processes.

Bioplastics can start with mirrors, which reflect sunlight to genetically modified algae.

What almost certainly isn't an option is making plastic how we currently do on Earth, taking advantage of the millions of years of stored solar crude oil contains.  Remove the economies of scale the Earth petroleum industry creates and we need to reexamine the way things are done.  This is why I "tack bio on".


Fair enough. Feedstocks are feedstocks. But we really do have better threads for this.

Agreed about the better threads.  For this thread what we care about is the power requirements for the electrolysis stack and atmosphere compressor.  With thoughtful design the rest of the propellant plant's power requirements are insignificant.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/28/2019 03:33 am
Agreed about the better threads.  For this thread what we care about is the power requirements for the electrolysis stack and atmosphere compressor.  With thoughtful design the rest of the propellant plant's power requirements are insignificant.
I should look this up, and not simply comment - but...

I assume that it is not possible to run the process with simply heated atmosphere and steam, rather than pressure?
This would obviously make the process need more volume, possibly catalyst and insulation.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 07/28/2019 03:36 am
Vandium Redox Flow Battery: https://www.avalonbattery.com/technology/

These are cheaper. (than Li Ion) It may be possible to transport the components from earth, and the electrolyte as dry chemicals, which are hydrated and assembled on Mars. Some types of flow battery can have large tanks of electrolyte allowing a larger energy storage for limited central battery infrastructure. This seems sensible if preparing for a sandstorm period, or even regular through-the night storage, or intermittent charging of larger Li Ion rover/vehicle batteries. Some of the chemistries are inexpensive.
 
I haven't noticed them at all on this thread or on NSF!
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/28/2019 02:08 pm
Vandium Redox Flow Battery: https://www.avalonbattery.com/technology/

These are cheaper. (than Li Ion) It may be possible to transport the components from earth, and the electrolyte as dry chemicals, which are hydrated and assembled on Mars. Some types of flow battery can have large tanks of electrolyte allowing a larger energy storage for limited central battery infrastructure. This seems sensible if preparing for a sandstorm period, or even regular through-the night storage, or intermittent charging of larger Li Ion rover/vehicle batteries. Some of the chemistries are inexpensive.
 
I haven't noticed them at all on this thread or on NSF!

If you're going with flow batteries, why not use nickel-hydrogen? Roughly double the volumetric and gravimetric energy density, and it has flight heritage with the ISS primary power system.

https://en.wikipedia.org/wiki/Nickel–hydrogen_battery (https://en.wikipedia.org/wiki/Nickel–hydrogen_battery)

https://en.wikipedia.org/wiki/Vanadium_redox_battery

Both battery technologies can be "dehydrated" to save shipping mass to Mars, but I'm not sure about the relative mass savings for each technology. For nickel-hydrogen the electrolyte is a 37% aqueous solution, but not sure for vanadium redox. This source (https://www.researchgate.net/post/How_do_I_make_the_vanadium_solution/) suggests roughly 2:1 ratio of VOSO4 to water. If you can make the high purity sulfuric acid on Mars it gets better, but it still doesn't approach Ni-H.

Downside is you need hydrogen tanks, but even with that the mass efficiency is still higher. And as discussed earlier, the nickel might be produced on Mars too.


edit: Ignore me, brain fart. Ni-H are not flow batteries.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/28/2019 02:26 pm
Vandium Redox Flow Battery: https://www.avalonbattery.com/technology/

These are cheaper. (than Li Ion) It may be possible to transport the components from earth, and the electrolyte as dry chemicals, which are hydrated and assembled on Mars.
Some of this is debatable.
The site you mention has a 10kW continuous power electrode unit weighing 3700kg, and stores 40kWh.
A substantial fraction of that will obviously be the flow component.

However, 40kWh of lithium weighs around 270kg in a near mars-ready form, and has a >95% charge/discharge efficiency, not 75%.
To supply 500kW for 18 hours of night would require 9000kWh of storage, which is with lithium 60 tons, and with this solution 800 tons. With the flow battery you need an additional 20% of power and 100kW of cooling.

Even with considerable derating of the lithium, it's hard to make a case that it's cheaper.


.


Title: Re: Power options for a Mars settlement
Post by: tenkendojo on 07/28/2019 03:31 pm
At 30 000 feet you're getting close to Martian conditions.  If all the electronics and power are just fine, then I guess Mars rating may not be all that much of a problem.

And you will never be able to fully pressurize a container for maintenance, but you can pressurize Starship (I hope!  How should I know really  :).

We need to get to at least above 30 000 Meters (100 000+ft) on  Earth atmosphere to get close to Martian conditions.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 07/28/2019 04:25 pm
Vandium Redox Flow Battery: https://www.avalonbattery.com/technology/

These are cheaper. (than Li Ion) It may be possible to transport the components from earth, and the electrolyte as dry chemicals, which are hydrated and assembled on Mars.
Some of this is debatable.
The site you mention has a 10kW continuous power electrode unit weighing 3700kg, and stores 40kWh.
A substantial fraction of that will obviously be the flow component.

However, 40kWh of lithium weighs around 270kg in a near mars-ready form, and has a >95% charge/discharge efficiency, not 75%.
To supply 500kW for 18 hours of night would require 9000kWh of storage, which is with lithium 60 tons, and with this solution 800 tons. With the flow battery you need an additional 20% of power and 100kW of cooling.

Even with considerable derating of the lithium, it's hard to make a case that it's cheaper.

Yes good points, I posted it quickly. And you are probably right. Thankyou for doing the maths - which I haven't. However it might deserve not total dismissal. The flow component (water based) can probably be expanded given simply more tanks electrolyte and water, to store energy for a longer time with possible less additional cost. I didn't spot the lower cycle efficiency, which increases the needed size, and the solar panel area. But that would have to be modelled. I still haven't looked up the cooling requirement, and it surprises me! I would have assumed overall it would have to be protected from freezing - especially if the energy is to be stored for longer! 60t of Li Ion batteries is a lot of Tesla Powerpacks. 800m^3 is I admit humongous - like 50m x 8x 2m - or 1/3 the volume of an Olympic swimming pool. But by the time Mars needs to store 9MWh overnight, construction will be scaled up!

Edit: When quoting the mass of lithium, are you giving the mass of the battery system needed, or the lithium only?
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/28/2019 04:36 pm
Quote from: SpeedEvil
Quote from: DistantTemple
These are cheaper. (than Li Ion) It may be possible to transport the components from earth, and the electrolyte as dry chemicals, which are hydrated and assembled on Mars.
The site you mention has a 10kW continuous power electrode unit weighing 3700kg, and stores 40kWh.
However, 40kWh of lithium weighs around 270kg in a near mars-ready form, and has a >95% charge/discharge efficiency, not 75%.
Edit: When quoting the mass of lithium, are you giving the mass of the battery system needed, or the lithium only?
I am quoting as-installed whole Tesla model 3 battery pack mass, rated for several G vibration loads, including cooling loop (though not external coolant). A percent or ten more mass would be needed to make a shippable pack of a hundred of these.

Title: Re: Power options for a Mars settlement
Post by: wes_wilson on 07/28/2019 09:16 pm
Probably like many of you, I spend too much time geeking out on random sites.  Anyway, I read something the other day that seemed like an interesting fit for this thread and after skimming back through all the prior pages I didn't see it discussed anywhere yet. 

TLDR: it's possible to use Iron and Iron Oxide as battery materials.  Iron is oxidized yielding heat to drive a generator and produce electricity while producing Iron Oxide.  The Iron Oxide is reduced back to Iron using renewable energy (presumably via solar on Mars) for future use. 

Things that piqued my interest
- Mars has lots of Iron Oxide, so it's a readily available resource.  ISRU is good.  Reduced need to carry high tech or high density battery materials to Mars. 
- Iron would oxidize slowly in present mars conditions so you could probably store it outside in huge piles with little infrastructure needed beyond a bulldozer or something to move around.  No worries about leaks or spills.
- Iron will probably be something the colony wants to produce anyway, so being able to use it in emergencies for energy is one less new tech stream that has to be established there.


These guys are working on a 100Kw plant with this approach. 
https://www.tue.nl/en/news/news-overview/13-09-2018-iron-powder-a-clean-alternative-fuel-for-industry-that-has-to-quit-natural-gas/

A couple other articles on it:
https://phys.org/news/2018-09-iron-powder-alternative-fuel-industry.html
https://www.mcgill.ca/newsroom/channels/news/could-metal-particles-be-clean-fuel-future-257172

Edit: We're talking about dust sized stuff here.  Not Iron ingots ;)
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 07/28/2019 11:11 pm
...snip...
TLDR: it's possible to use Iron and Iron Oxide as battery materials.  Iron is oxidized yielding heat to drive a generator and produce electricity while producing Iron Oxide.  The Iron Oxide is reduced back to Iron using renewable energy (presumably via solar on Mars) for future use. 

Things that piqued my interest
- Mars has lots of Iron Oxide, so it's a readily available resource.  ISRU is good.  Reduced need to carry high tech or high density battery materials to Mars. 
- Iron would oxidize slowly in present mars conditions so you could probably store it outside in huge piles with little infrastructure needed beyond a bulldozer or something to move around.  No worries about leaks or spills.
- Iron will probably be something the colony wants to produce anyway, so being able to use it in emergencies for energy is one less new tech stream that has to be established there.
snip...
Edit: We're talking about dust sized stuff here.  Not Iron ingots ;)
This seems particularly useful for long term storage.... for dust storm periods! You can gradually build up a vast reserve, then cope for many weeks if needed! Brilliant! And as you say, storage doesnt require tanks, or covers, or even any serious containment!
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/28/2019 11:37 pm
...snip...
TLDR: it's possible to use Iron and Iron Oxide as battery materials.  Iron is oxidized yielding heat to drive a generator and produce electricity while producing Iron Oxide.  The Iron Oxide is reduced back to Iron using renewable energy (presumably via solar on Mars) for future use. 

Things that piqued my interest
- Mars has lots of Iron Oxide, so it's a readily available resource.  ISRU is good.  Reduced need to carry high tech or high density battery materials to Mars. 
- Iron would oxidize slowly in present mars conditions so you could probably store it outside in huge piles with little infrastructure needed beyond a bulldozer or something to move around.  No worries about leaks or spills.
- Iron will probably be something the colony wants to produce anyway, so being able to use it in emergencies for energy is one less new tech stream that has to be established there.
snip...
Edit: We're talking about dust sized stuff here.  Not Iron ingots ;)
This seems particularly useful for long term storage.... for dust storm periods! You can gradually build up a vast reserve, then cope for many weeks if needed! Brilliant! And as you say, storage doesn't require tanks, or covers, or even any serious containment!
Aluminium batteries are another possibility.  But really, as the colony will be producing methane anyway, oxidizing methane still seems like the simplest idea to me.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 07/28/2019 11:43 pm
Methane needs tanks (even if they are melted out of a glacier). Iron dust just needs  room to place a small hill!
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 07/28/2019 11:58 pm
Methane needs tanks (even if they are melted out of a glacier). Iron dust just needs  room to place a small hill!
What is the efficiency of the process used to de-oxidize the iron in the first place? Because that is where the energy really comes from.
Without coal handy, you can either use hydrogen, that you have already electrolyzed in the first place, or carbon monoxide, and that's also obtained by reacting CO2 with hydrogen....  so iron will always be less effective than hydrogen or methane.  The sabatier reaction being exothermic, it's doesn't consume much energy, so methane is a better battery than iron.
Plus you have all those spaceship tanks to use. 
And yes, methane can be stored pretty cheaply in underground formations.  Lava tubes, for example... nice large volumes at low pressure.  Or sand formations with lava on top.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 07/29/2019 12:12 am
Yes that does make good sense. However, we shouldn't shut down lateral thinking too quickly. Because Mars is different from Earth; geology, gravity, space, life, atmosphere, radiation etc as well as human actions being harder or effectively more expensive. etc. Things like storing iron dust outside where on earth it would get ruined by rain. And conversely pumped storage is OK on earth, but hard on Mars as water would freeze. So because of these differences we will probably miss great solutions! Also if a solution for one thing fits into a web of other solutions like using the iron dust for iron and steel, OR burning it for energy.... then it might be worth keeping it on the back burner.
Here's another - pumped storage using dust/soil/sand. Only much use where there is a high relief (geography term)
And with a lower gravity not so effective!
Title: Re: Power options for a Mars settlement
Post by: wes_wilson on 07/29/2019 01:24 am
Methane needs tanks (even if they are melted out of a glacier). Iron dust just needs  room to place a small hill!
What is the efficiency of the process used to de-oxidize the iron in the first place? Because that is where the energy really comes from.
Without coal handy, you can either use hydrogen, that you have already electrolyzed in the first place, or carbon monoxide, and that's also obtained by reacting CO2 with hydrogen....  so iron will always be less effective than hydrogen or methane.  The sabatier reaction being exothermic, it's doesn't consume much energy, so methane is a better battery than iron.
Plus you have all those spaceship tanks to use. 
And yes, methane can be stored pretty cheaply in underground formations.  Lava tubes, for example... nice large volumes at low pressure.  Or sand formations with lava on top.

I did some searching on efficiency before posting because that's the obvious question, and I couldn't find much.  I found one site saying round trip efficiency of mid 40% to high 50% range but there were no citations.  That would make it slightly worse than methane.

Not saying it's a good fit, but that it's a novel concept for energy storage that hasn't been kicked around in this thread and the materials needed for it would be in great abundance pretty much everywhere on the planet. 

Solid storage does have some advantages over liquid storage.  There's no limit to how large you can make a pile, while storage of methane is going to be limited by the size of your storage tank.  If you want to transport the solid from one place to another then trucks can just drive it and drop it off; if you want to transport liquids you need equal size tanks (double capacity overall) at the origin and destination.  Basically, with liquid, your capacity to capture excess energy production will always be gated by your storage availability while with solids there's no gate.   

Reduced iron will have a place in the supply chain for construction purposes so reducing iron is likely to be on the tech tree of any establishment that's developing industry.  Having the ability to use it as a backup for emergencies might be a good idea, even if Methane is the go-to day/day fuel.

Agree though that methane's probably the more logical choice as those processes are far more mature and well known but things like this may be where Mars tech diverges from Earth tech.   




 





 


Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/29/2019 01:54 am
Agreed about the better threads.  For this thread what we care about is the power requirements for the electrolysis stack and atmosphere compressor.  With thoughtful design the rest of the propellant plant's power requirements are insignificant.
I should look this up, and not simply comment - but...

I assume that it is not possible to run the process with simply heated atmosphere and steam, rather than pressure?
This would obviously make the process need more volume, possibly catalyst and insulation.

Lar has been giving the off topic warning so I will be brief.  The Sabatier reaction uses hydrogen, not water.  What you want is a different process, preferably one that separates the methane and oxygen before they decide to revert back to water and carbon dioxide.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/29/2019 02:12 am
I'm going to throw this out there.

Quote
The purpose of this White Paper is to describe and evaluate the potential of aluminum-water
reactions for the production of hydrogen for on-board hydrogen-powered vehicle applications.
Although the concept of reacting aluminum metal with water to produce hydrogen is not new,
there have been a number of recent claims that such aluminum-water reactions might be
employed to power fuel cell devices for portable applications such as emergency generators and
laptop computers, and might even be considered for possible use as the hydrogen source for fuel
cell-powered vehicles.

https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/aluminium_water_hydrogen.pdf
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 07/29/2019 02:24 am
Iron/Iron-oxide batteries are at the beginning of their (modern re-)development cycle. Lithium ion is close to the end.

While there might be other, better solutions coming out of labs and into meaningful industrial-scale production by the time Martian colonists need it, IMO it is the wrong approach to focus on every novel lab-scale announcement when talking about the topic-of-record in this thread. (In other threads, esp. in Advanced Concepts, go nuts.)

Lithium ion is a known quantity. Whatever tech ends up being used, it won't be worse. It might not, however, be much better. So when comparing power generation and storage combinations, then (again, IMO) use numbers from lithium ion. If you can solve the problem with that, you can obviously solve it with anything better than that. OTOH, if you can only solve the problem with the most promising lab-scale numbers for an experimental technology, in reality you can't solve the problem.

[Joseph: You are the biggest "offender" in that [edit: for the last few pages only]. Not because it's off-topic for the site (well, IMO it's not), it's that it's a distraction in this one thread. Why not start a topic or three in the Advanced Concept section focused on your interests,

eg, "Breakthroughs in energy storage and their ISRU suitability"

and repost the various concepts/announcements/papers you have posted here, and those you find in the future. Even if it ends up being just a link-to-papers thread, there are others like that on the site which people appreciate having in one spot and maintained by one reliable dedicated person. (Although I suspect it will attract plenty of discussion, to the point where you may have to create a second thread for links-to-papers only. Disco vs updo.)]
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/29/2019 02:49 am
Iron/Iron-oxide batteries are at the beginning of their (modern re-)development cycle. Lithium ion is close to the end.

While there might be other, better solutions coming out of labs and into meaningful industrial-scale production by the time Martian colonists need it, IMO it is the wrong approach to focus on every novel lab-scale announcement when talking about the topic-of-record in this thread. (In other threads, esp. in Advanced Concepts, go nuts.)

Lithium ion is a known quantity. Whatever tech ends up being used, it won't be worse. It might not, however, be much better. So when comparing power generation and storage combinations, then (again, IMO) use numbers from lithium ion. If you can solve the problem with that, you can obviously solve it with anything better than that. OTOH, if you can only solve the problem with the most promising lab-scale numbers for an experimental technology, in reality you can't solve the problem.

[Joseph: You are the biggest "offender" in that. Not because it's off-topic for the site (well, IMO it's not), it's that it's a distraction in this one thread. Why not start a topic or three in the Advanced Concept section focused on your interests,
eg, "Breakthroughs in energy storage and their ISRU suitability"
and repost the various concepts/announcements/papers you have posted here, and those you find in the future. Even if it ends up being just a link-to-papers thread, there are others like that on the site which people appreciate having in one spot and maintained by one reliable dedicated person. (Although I suspect it will attract plenty of discussion, to the point where you may have to create a second thread for links-to-papers only. Disco vs updo.)]

The biggest offender??? 

Most of my comments in this thread have been about commercially available products and their application in methalox plants that use water electrolysis and Sabatier reactors, not advanced concepts.

How about this.  Why not suggest a good place to put a "How to build a methalox plant" thread?  We're talking about century+ old chemistry, so advanced concepts isn't the right place.  This tech isn't specific to any one body in the solar system.  We can even use it in orbit.  Missions to Mars, asteroids, or in-space hardware aren't a good fit.  SpaceX isn't the only company developing methalox, so company specific isn't right either.
Title: Re: Power options for a Mars settlement
Post by: Keldor on 07/29/2019 03:24 am
Storage space for methane is actually something they'll have in abundance.  Initially, they're going to need all sorts of supplies, so it seems likely there will be multiple cargo Starships sitting around.  Rockets are basically big tanks with engines on one end...

As far as reuse, at first they're going to have their work cut out for them just to produce enough fuel to return a single starship with the crew.  Eventually, they'll have their in situ production high enough and supply demand low enough that they'll be able to return every arriving Starship, and even later, the colony will have spare resources to divert to start sending back the older Starships that have been sitting there for years.   Keep in mind, though, that at this point, the older vehicles will have depreciated in value quite a bit.  I strongly suspect that many of the cargo vehicles from the early mission will be there to stay.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 07/29/2019 03:43 am
[Joseph: You are the biggest "offender" in that. Not because it's off-topic for the site (well, IMO it's not), it's that it's a distraction in this one thread. Why not start a topic or three in the Advanced Concept section focused on your interests, eg, "Breakthroughs in energy storage and their ISRU suitability" [...]
The biggest offender???  Most of my comments in this thread [...]

I intended by comment to be constructive. If you felt like it was an attack, I apologise.

How about this.  Why not suggest a good place to put a "How to build a methalox plant" thread?  We're talking about century+ old chemistry, so advanced concepts isn't the right place.

Fusion is over 70 years old. You can make a Farnsworth Fusor in your basement. But fusion threads go in AC. (Unless it's fringe physics, then it goes in AC's freaky step-sister "New Physics".) Metal batteries are over a century old, but novel developments in the field belong in AC.

Because...

This tech isn't specific to any one body in the solar system.  We can even use it in orbit.  Missions to Mars, asteroids, or in-space hardware aren't a good fit.  SpaceX isn't the only company developing methalox, so company specific isn't right either.

So we have AC for all the things that don't fit anywhere else.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 07/29/2019 04:33 am

I intended by comment to be constructive. If you felt like it was an attack, I apologise.

Thank you.  My initial intent was only to clarify the electrolysis electrode vs Sabatier catalyst degradation mistake.  Unfortunately that lead us down a rabbit hole. 

Quote
How about this.  Why not suggest a good place to put a "How to build a methalox plant" thread?  We're talking about century+ old chemistry, so advanced concepts isn't the right place.

Fusion is over 70 years old. You can make a Farnsworth Fusor in your basement. But fusion threads go in AC. (Unless it's fringe physics, then it goes in AC's freaky step-sister "New Physics".) Metal batteries are over a century old, but novel developments in the field belong in AC.

Because...

This tech isn't specific to any one body in the solar system.  We can even use it in orbit.  Missions to Mars, asteroids, or in-space hardware aren't a good fit.  SpaceX isn't the only company developing methalox, so company specific isn't right either.

So we have AC for all the things that don't fit anywhere else.

OK, but this is simple stuff, once one does their homework.  I'll write up something for AC, but the first line is going to be a big bold disclaimer that none of the components are actually advanced concepts.

Comparing off the shelf tech to fusion baffles me.

I haven't posted anything about metal batteries.  You are confusing me with someone else.
Title: Re: Power options for a Mars settlement
Post by: speedevil on 07/29/2019 04:59 am
Agreed about the better threads.  For this thread what we care about is the power requirements for the electrolysis stack and atmosphere compressor.  With thoughtful design the rest of the propellant plant's power requirements are insignificant.
I should look this up, and not simply comment - but...

I assume that it is not possible to run the process with simply heated atmosphere and steam, rather than pressure?
This would obviously make the process need more volume, possibly catalyst and insulation.

Lar has been giving the off topic warning so I will be brief.  The Sabatier reaction uses hydrogen, not water.  What you want is a different process, preferably one that separates the methane and oxygen before they decide to revert back to water and carbon dioxide.
Typo.

I meant hydrogen, not water.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 08/01/2019 08:00 am
Agreed about the better threads.  For this thread what we care about is the power requirements for the electrolysis stack and atmosphere compressor.  With thoughtful design the rest of the propellant plant's power requirements are insignificant.
I should look this up, and not simply comment - but...

I assume that it is not possible to run the process with simply heated atmosphere and steam, rather than pressure?
This would obviously make the process need more volume, possibly catalyst and insulation.

Lar has been giving the off topic warning so I will be brief.  The Sabatier reaction uses hydrogen, not water.  What you want is a different process, preferably one that separates the methane and oxygen before they decide to revert back to water and carbon dioxide.
Typo.

I meant hydrogen, not water.

Alrighty then.

Pressure Increases the efficiency of Sabatier reactor catalyst surface area, but this isn't the key factor.  The key factor using non-advanced concepts is cleaning the methane after the Sabatier reactor.

Personal (off-topic) Log: 

I've spent the last few days trying to figure out how to make Pau451l's suggestion that the technology-Sabatier-reactors-need-are-somehow-advanced-concepts into a series of advanced concepts posts into single thread worthy of NSF.  As of now I have no clue how to make this old/high-school-advanced-chemistry tech into a series worthy of advanced concepts.  What I need most is the "Hey, Dumas!!!" kick in the heinie so I can put this information somewhere.  This stuff isn't hard if one forgoes 'patent rights' and "Drill, baby drill!!!"

If only there were a, simplistic concepts that aren't economically viable here on Earth section...
Title: Re: Power options for a Mars settlement
Post by: Ionmars on 08/01/2019 08:39 am
Regarding the burning of iron to produce energy.

You should not store your refined iron powder exposed to the Mars’ atmosphere because it will introduce contaminants. The atmosphere contains molecule-sized particles that circulate the planet, which include iron oxide particles. But it also includes other species that would also precipitate onto your pure iron pile. e.g. basalt particles.

The atmosphere could actually be a source of iron, but it will need to be refined.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 08/01/2019 10:05 am
Regarding the burning of iron to produce energy.

You should not store your refined iron powder exposed to the Mars’ atmosphere because it will introduce contaminants. The atmosphere contains molecule-sized particles that circulate the planet, which include iron oxide particles. But it also includes other species that would also precipitate onto your pure iron pile. e.g. basalt particles.

The atmosphere could actually be a source of iron, but it will need to be refined.

Agreed, but with a caveat.  Clairton Coke Works piles their coke below the Clairton-Glassport Bridge. (https://www.google.com/maps/place/Clairton+Mill+Works+United+States+Steel+Corporation/@40.3118344,-79.8917855,831m/data=!3m1!1e3!4m5!3m4!1s0x8834fcb540c1c1c5:0xbb53b739b567f184!8m2!3d40.2965903!4d-79.8738442)  Yes, some of the coke oxidizes.  This is OK because the cost of building a 'shelter' is much greater than the cost of letting coke oxidize.

I really don't want to derail the thread, but economics is important.  A pile of metallic dust has value.  We need to do a trade study to determine whether the reduced dust is worth storing.  For what it's worth(FWIW): I can say that here on Earth storing piles of reduced resources makes sense.
Title: Re: Power options for a Mars settlement
Post by: Ionmars on 08/01/2019 10:50 am
...
...
Agreed, but with a caveat.  Clairton Coke Works piles their coke below the Clairton-Glassport Bridge. (https://www.google.com/maps/place/Clairton+Mill+Works+United+States+Steel+Corporation/@40.3118344,-79.8917855,831m/data=!3m1!1e3!4m5!3m4!1s0x8834fcb540c1c1c5:0xbb53b739b567f184!8m2!3d40.2965903!4d-79.8738442)  Yes, some of the coke oxidizes.  This is OK because the cost of building a 'shelter' is much greater than the cost of letting coke oxidize.

I really don't want to derail the thread, but economics is important.  A pile of metallic dust has value.  We need to do a trade study to determine whether the reduced dust is worth storing.  For what it's worth(FWIW): I can say that here on Earth storing piles of reduced resources makes sense.
To cover refined iron dust on Mars, a tarpaulin equivalent should suffice.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 08/02/2019 07:36 pm
Page 7 of the 39A EA indicates Starship propellant capacity is increasing to "up to 1,500 MT".  This means our power requirement calculations for the propellant plant have been too low.

I suggest we wait for the post-hop update to see if we get more details before rerunning the numbers.
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 08/21/2019 06:58 pm
Chiron on the News now says:

"President Trump Signs Off on Launch of Nuclear Power into Outer Space"

https://www.space.com/trump-nuclear-spacecraft-launch-guidelines.html

Thought it might be more geared toward power but doesn't seem to preclude it either.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 08/21/2019 07:51 pm
This was one of the things talked about at the meeting yesterday it's good to see forward motion.
Title: Re: Power options for a Mars settlement
Post by: Lar on 08/21/2019 09:53 pm
I'd love a thread that dug into the best way to do methane production and the nuances of it. Don't fret too hard about where to put it. Just start it. We can always move it later. It is very helpful for the starting post to link to other relevant threads. The chemical industry one seems apt to me and this one.
Title: Re: Power options for a Mars settlement
Post by: FutureSpaceTourist on 10/13/2019 05:53 am
https://twitter.com/erdayastronaut/status/1183119630061178883

Quote
How big of a solar field will it take to run an ISRU plant on Mars? Will the first couple starships be mostly packed with solar / batteries / ISRU gear? Would you run nuclear for ISRU / colony power if given the opportunity?

twitter.com/elonmusk/status/1183150883162349569

Quote
Depends on total system efficiency & how long the propellant plant can run to refill Starship, so 1 to 10MW as a rough guess

https://twitter.com/elonmusk/status/1183150916473516032

Quote
Solar
Title: Re: Power options for a Mars settlement
Post by: Bogeyman on 11/11/2019 06:41 pm
I don't know if this is the correct thread here (if not, please move somewhere else), but I just stumbled over this and this is just beyond awesome:
https://www.youtube.com/watch?v=AIrH01N9AsE
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/11/2019 09:06 pm
I don't know if this is the correct thread here (if not, please move somewhere else), but I just stumbled over this and this is just beyond awesome:
https://www.youtube.com/watch?v=AIrH01N9AsE
It looks awesome but is a somewhat ironic choice for this thread. The power requirements would be beyond all decent contemplation, so in terms of power options for a Mars settlement it requires all of the power options for many many years.
Title: Re: Power options for a Mars settlement
Post by: Nathan2go on 11/12/2019 01:59 am
For fuel production Mars, it's hard to imagine anything beating solar PV.  And fuel will be the vast majority of the power usage.  There's no need for batteries, just turn-off the electrolyzers at night.

But for always-on power to support life support etc, nukes have got to beat batteries (after the first few hours at least).

An RTG (Radio-isotope-decay thermal generator) is more suitable than a nuclear fission reactor for a commercial nuclear power source.  RTGs don't involve chain reactions, their power generation can't be sped up, and their active materials can't be used to make a nuclear explosion.  The government regulations and security will make fission unaffordable for space start-ups, but RTG pose essentially no risk to the public, so they need no such regulation (dirty-bombs are a myth;  there is simply no way to make one that is more effective than a simple nail-bomb).

I like RTGs powered by https://en.wikipedia.org/wiki/Strontium-90 (https://en.wikipedia.org/wiki/Strontium-90) or perhaps Cesium-137.  NASA likes building their RTGs using Pu-238, which has less decay in output power over the course of a 10 year mission (87 year half-life).  Sr-90 and Cs-137 have half-lives of about 30 years, so they last long enough for commercial products and they have similar energy density.  But the important difference is that in moving away from plutonium, we'll also move away from government regulation and security concerns.  Sr-90 is a pure beta emitter, so no radiation other than heat can escape the cladding material around the strontium.***

The normal reasons to choose a fission reactor over an RTG are:
1) The core starts at zero power and no radio-activity.  This solves the problem of how to keep the core cool during launch and transit.  But another solution that works for RTGs is to use a rocket with a steel payload compartment, such as Starship!  Maybe the RTGs are modular, and put out 1kW each;  if they mount on the 120 m^2 bay door, we could easily pass 120 kW to ambient air via convection, and radiate a similar amount with the door open.  We'd probably want to blow air through the payload bay during prep and launch, but it is nice to know the rocket won't melt if the blowers turn-off accidentally.

2) Material availability.  Uranium fission cores can be made by the existing supply chain.  But strontium would require a new supply.  If we re-processed spent fuel from a commercial nuclear industry, the stuff would be readily available. (maybe it will be available from a Chinese supplier, since they are building fast reactors now).

It is interesting to note that nuclear power and solar will each play important roles in space settlement.  One can imagine the first wave of large extraterrestrial cities being built in equatorial LEO, because LEO the cheapest & fastest location to travel to, and equatorial orbits have the lowest radiation levels.  (See Globus-Marotta, "The High Frontier, an Easier Way" https://books.google.com/books/about/The_High_Frontier.html?id=f6hRvQEACAAJ&source=kp_book_description).

The next wave of settlements will be in elliptical orbits, to get better access to solar energy for farming, with lower transport cost than going all the way to Lagrangia.  But the radiation levels are high, so maybe you need shielding material from the Moon, which requires rocket fuel from the Lunar poles, which require making power in a permanently shaded crater, which requires nuclear power (beamed power has other issues).   Mass drivers require very large demand and also benefit from nuclear power.

*** Edit: as noted down-thread, beta emitters like strontium-90 will also emit secondary x-ray photons, so radiation shielding will be required. The Pu-238 in NASA's RTGs is an alpha emitter.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/12/2019 04:15 am
I don't know if this is the correct thread here (if not, please move somewhere else), but I just stumbled over this and this is just beyond awesome:
[Hassell/EOC Mars Hab proposal]

It was previously posted on the Envisioning Amazing Martian Habitats (https://forum.nasaspaceflight.com/index.php?topic=41427.0) thread, along with the other entries in NASA's Mars hab contest.

(First mention of the early contest was on the first page, the only other mention I can find with a quick search is here (https://forum.nasaspaceflight.com/index.php?topic=41427.msg1930562#msg1930562). But I know I or someone else discussed/debated/criticised the results of each round.)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/12/2019 05:14 am
For fuel production Mars, it's hard to imagine anything beating solar PV.  And fuel will be the vast majority of the power usage.  There's no need for batteries, just turn-off the electrolyzers at night.

But for always-on power to support life support etc, nukes have got to beat batteries (after the first few hours at least).

Beat batteries on mass? Probably. Beat batteries on total cost? Unlikely.


Also, life support systems can use a similar trick as fuel production to buffer energy without needing batteries:

• For oxygen supply, store excess O2 production as LOX. This will already be done on Mars as part of the methalox production process.

• For CO2 scrubbing, regenerate a reserve supply of LiOH beds (the regeneration step uses the vast majority of the energy).

• For potable water, stabilize with iodine and store it in a tank.

• For habitat heating, super-insulate the habitat and use a thermal mass battery (ideally this thermal mass function could be combined with the radiation shielding regolith and/or water. And naturally, you can burn stored methalox too.

• For dehumidification, hygroscopic interior cob walls (made of in-situ material) can buffer a surprising amount of humidity. These can also be done as a cob surface finish over Compressed Mars Blocks or other materials.

• For stored food there are many options (MREs, bulk food, etc).

The engineering trade-off here is exactly the same as for fuel production electrolysis: oversizing the production system (or more likely, carrying a larger number of identical oxygen/water/CO2 modules) and having additional consumable storage capacity. Of course such a critical system as life support probably demands this type of multi-level redundancy anyway.

Increasing those system margins a bit more yields plenty of energy storage within the life support system itself, and the "always-on power" requirement almost disappears. Your life support electricity requirements drop to just ventilation (for the CO2 scrubbers), dehumidification (needed for steady-state operation after few days when the hygroscopic cob surfaces become hydrated to their upper design limit) and LED lighting.

Obviously each of these "energy storage systems" (and numerous other possible options) would need to pass an engineering cost-trade analysis against simply carrying an equivalent amount of batteries. But I think they're all sound (with the possible exception of the cob walls, but I'm a sucker for cob walls :D).


Edit: oops, forgot that the CO2 scrubbers require dehumidified air to function. C'est la vie! Cob walls, we hardly knew yee.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 11/12/2019 12:56 pm

I like RTGs powered by https://en.wikipedia.org/wiki/Strontium-90 (https://en.wikipedia.org/wiki/Strontium-90) or perhaps Cesium-137.  NASA likes building their RTGs using Pu-238, which has less decay in output power over the course of a 10 year mission (87 year half-life).  Sr-90 and Cs-137 have half-lives of about 30 years, so they last long enough for commercial products and they have similar energy density.  But the important difference is that in moving away from plutonium, we'll also move away from government regulation and security concerns.  Sr-90 is a pure beta emitter, so no radiation other than heat can escape the cladding material around the strontium.

X-rays. Try putting a gieger counter up to one of the many tritium sources you can buy from amazon. Beta rays(electrons) are absorbed but generate x-rays.
Title: Re: Power options for a Mars settlement
Post by: Eka on 11/12/2019 03:33 pm

I like RTGs powered by https://en.wikipedia.org/wiki/Strontium-90 (https://en.wikipedia.org/wiki/Strontium-90) or perhaps Cesium-137.  NASA likes building their RTGs using Pu-238, which has less decay in output power over the course of a 10 year mission (87 year half-life).  Sr-90 and Cs-137 have half-lives of about 30 years, so they last long enough for commercial products and they have similar energy density.  But the important difference is that in moving away from plutonium, we'll also move away from government regulation and security concerns.  Sr-90 is a pure beta emitter, so no radiation other than heat can escape the cladding material around the strontium.

X-rays. Try putting a gieger counter up to one of the many tritium sources you can buy from amazon. Beta rays(electrons) are absorbed but generate x-rays.
Yep, just bury them a safe distance away.
Title: Re: Power options for a Mars settlement
Post by: 1 on 11/12/2019 08:50 pm
To be fair, Nathan did include the words "cladding material" in his statement; and it would be quite easy to chose a material stack-up that would block x-rays. Burying the RTG isn't strictly needed, but is still a good idea because it provides very cheap insurance against a flaw in/failure of the cladding material.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 11/12/2019 09:09 pm

I like RTGs powered by https://en.wikipedia.org/wiki/Strontium-90 (https://en.wikipedia.org/wiki/Strontium-90) or perhaps Cesium-137.  NASA likes building their RTGs using Pu-238, which has less decay in output power over the course of a 10 year mission (87 year half-life).  Sr-90 and Cs-137 have half-lives of about 30 years, so they last long enough for commercial products and they have similar energy density.  But the important difference is that in moving away from plutonium, we'll also move away from government regulation and security concerns.  Sr-90 is a pure beta emitter, so no radiation other than heat can escape the cladding material around the strontium.

X-rays. Try putting a gieger counter up to one of the many tritium sources you can buy from amazon. Beta rays(electrons) are absorbed but generate x-rays.

AKA bremsstrahlung radiation. Same basic principle as an x-ray tube.
Title: Re: Power options for a Mars settlement
Post by: Nathan2go on 11/17/2019 04:10 am

I like RTGs powered by https://en.wikipedia.org/wiki/Strontium-90 (https://en.wikipedia.org/wiki/Strontium-90) or perhaps Cesium-137.  NASA likes building their RTGs using Pu-238, which has less decay in output power over the course of a 10 year mission (87 year half-life).  Sr-90 and Cs-137 have half-lives of about 30 years, so they last long enough for commercial products and they have similar energy density.  But the important difference is that in moving away from plutonium, we'll also move away from government regulation and security concerns.  Sr-90 is a pure beta emitter, so no radiation other than heat can escape the cladding material around the strontium.

X-rays. Try putting a gieger counter up to one of the many tritium sources you can buy from amazon. Beta rays(electrons) are absorbed but generate x-rays.
Oh right, thanks for the explanation.
The betas come out at energies of up to 2.3 MeV, so the secondary x-rays could be rather penetrating.  Rather than thick cladding, maybe burying them is a better solution.

The power density of strontium titanate is 0.256 W/g or 3.9 kg/kW, which is small compared to a likely radiation shield it would need.  It still might be possible to ship to Mars/Luna with only light shielding in un-crewed cargo ships.

I'm still hopeful that such a product could have a lower regulatory burden, therefore lower cost than plutonium though.

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/17/2019 07:27 am

I like RTGs powered by https://en.wikipedia.org/wiki/Strontium-90 (https://en.wikipedia.org/wiki/Strontium-90) or perhaps Cesium-137.  NASA likes building their RTGs using Pu-238, which has less decay in output power over the course of a 10 year mission (87 year half-life).  Sr-90 and Cs-137 have half-lives of about 30 years, so they last long enough for commercial products and they have similar energy density.  But the important difference is that in moving away from plutonium, we'll also move away from government regulation and security concerns.  Sr-90 is a pure beta emitter, so no radiation other than heat can escape the cladding material around the strontium.

X-rays. Try putting a gieger counter up to one of the many tritium sources you can buy from amazon. Beta rays(electrons) are absorbed but generate x-rays.
Oh right, thanks for the explanation.
The betas come out at energies of up to 2.3 MeV, so the secondary x-rays could be rather penetrating.  Rather than thick cladding, maybe burying them is a better solution.

The power density of strontium titanate is 0.256 W/g or 3.9 kg/kW, which is small compared to a likely radiation shield it would need.  It still might be possible to ship to Mars/Luna with only light shielding in un-crewed cargo ships.

I'm still hopeful that such a product could have a lower regulatory burden, therefore lower cost than plutonium though.

That's the power density of only the radionuclide itself. The whole device (taking the GPHS-RTG as a prototypical example) achieves only 0.005 W/g of electrical output, plus 0.072 W/g of waste heat. And building and certifying the device is far more costly than solar.
Title: Re: Power options for a Mars settlement
Post by: Eka on 11/17/2019 01:07 pm
Page 32 plus of this for some different numbers. Kilopower units. 1 to 10kW. A 10kW unit is expected to be 5W per kg. Would need many of them to make fuel. I know much mow powerful semi trailer sized reactors were built and tested. Sadly a few were built, stored a long time, then sold for scrap, never having been fueled. Would have been ideal to modify and send to Mars.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150021391.pdf
Title: Re: Power options for a Mars settlement
Post by: Nathan2go on 11/17/2019 06:39 pm
... GPHS-RTG as a prototypical example) achieves only 0.005 W/g of electrical output, plus 0.072 W/g of waste heat. And building and certifying the device is far more costly than solar.
Regarding the power density of the complete system, we need to consider modern designs from the Kilopower program, which is more representative of products for crewed bases than the 1960s era small (200W scale) systems.  I.e. if we are not supportive of  modern space nuclear power programs, we won't know what the options are.

Regarding cost to build, don't forget that most of the cost could be Space construction, which is orders of magnitude more costly than building things on Earth.  PV could be a lot more surface area and a lot more construction labor.  Again, we won't know until we see the competing designs.

... A 10kW unit is expected to be 5W per kg. Would need many of them to make fuel. I know much mow powerful semi trailer sized reactors were built and tested. ...

For RTGs, there is no critical mass, so there may not be an advantage to going with a few big units, rather than staying with a very large number of modular units in the 1-30 kW range.  On Mars and Luna, the bulky part of any thermal power system is getting rid of waste heat.  You can't do convection or conduction very well.  So maybe you need of the order of 1 sq. meter of radiating area for every kW of waste heat.  Sounds similar to PV, except that it runs day & night, and doesn't degrade at Mars distance or at polar locations (i.e. where the water is), or when the sky is full of dust.
Title: Re: Power options for a Mars settlement
Post by: Eka on 11/17/2019 08:14 pm
... A 10kW unit is expected to be 5W per kg. Would need many of them to make fuel. I know much mow powerful semi trailer sized reactors were built and tested. ...

For RTGs, there is no critical mass, so there may not be an advantage to going with a few big units, rather than staying with a very large number of modular units in the 1-30 kW range.  On Mars and Luna, the bulky part of any thermal power system is getting rid of waste heat.  You can't do convection or conduction very well.  So maybe you need of the order of 1 sq. meter of radiating area for every kW of waste heat.  Sounds similar to PV, except that it runs day & night, and doesn't degrade at Mars distance or at polar locations (i.e. where the water is), or when the sky is full of dust.
OK, the big reactors I mentioned being scrapped were of a standard fission reactor design like used in the big power plants, just smaller. They were designed to run a military base. Size, they fit on a semi trailer. I think most of them required extra shielding for operation.

Military reactors. Not seeing the one I remember.
https://en.wikipedia.org/wiki/Army_Nuclear_Power_Program (https://en.wikipedia.org/wiki/Army_Nuclear_Power_Program)
To bad MM-1 didn't get built.
Quote
While initially meant to power bases and field operations, the program was shifted to the Army's "Energy Depot Concept" to investigate the production of synthetic fuels. The reactor and associated trailers would produce liquid fuels for tanks, trucks, armored personnel carriers, and aircraft and drastically reduce the vulnerable petroleum logistical supply chain. The associated trailers would use chemical conversion processes to convert the reactor's waste heat energy into useful fuels using elements universally found in air and water (hydrogen, oxygen, nitrogen and carbon), potentially producing methanol, liquid hydrogen and/or ammonia.

New portable DOD reactor program soon?
https://thebulletin.org/2019/02/the-pentagon-wants-to-boldly-go-where-no-nuclear-reactor-has-gone-before-it-wont-work/ (https://thebulletin.org/2019/02/the-pentagon-wants-to-boldly-go-where-no-nuclear-reactor-has-gone-before-it-wont-work/)
Quote
The Defense Department’s request for information (RFI) was issued on January 18 by the Strategic Capabilities Office, which reports to the Under Secretary of Defense for Research and Engineering. It seeks information on “innovative technologies and approaches” for demonstration of a prototype reactor with a threshold power of 1 to 10 megawatts of electricity. The RFI specifies that the reactor, at a minimum, should be less than 40 tons total weight; small enough to be transported by truck, ship, and aircraft; able to run for at least three years without refueling; and capable of semi-autonomous operation.
Sounds near perfect for Mars. A longer fuel life would be preferable. Spent fuel could be stored in water pools like they do on Earth. They have an aggressive timeline.
Quote
Such research is time-consuming, but proponents of micro-reactors want to move fast. The 2018 US Army report refers to a demonstration date of 2023, and the Idaho National Laboratory (INL), which hopes to return to its glory days as a site for building and testing experimental reactors, believes that with sufficient resources it can demonstrate such a reactor as early as 2021. To have even the slightest chance of meeting such aggressive deadlines, high-maturity reactor designs would already have to be on the shelf and construction-ready. But the options available today do not provide cause for optimism.

Another interesting project. A small sealed reactor that is designed tamper proof, 10MW to 100MW capacity. 200t to 500t total weight. Was from back in 2004, and one was supposed to be built by now, but program was dropped. Sounds like an interesting program to resurrect. SS18 would be able to loft. A smaller one may be able to be built, and fit on a SS8.
https://en.wikipedia.org/wiki/Small,_sealed,_transportable,_autonomous_reactor (https://en.wikipedia.org/wiki/Small,_sealed,_transportable,_autonomous_reactor)
Title: Re: Power options for a Mars settlement
Post by: Eka on 11/17/2019 08:23 pm
Goldmine of information: ;D
https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx (https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx)
Just updated Nov 2019.
Title: Re: Power options for a Mars settlement
Post by: Eka on 11/18/2019 01:02 am
Something I'm noticing many of these reactors could also generate heat for heating habitats. Also for melting subsurface water, or water at the poles.

Not immediately usable on Mars. Needs infrastructure that would take time to build. Needs SS18 for launch. Can be sent without fuel, and fueled with Mars sourced fuel rods if refinement infrastructure is there. Fuel could also be sent on a special SS trip in a very rugged containment vessel.

NuScale Power 60MW electrical, 200MW thermal, Small Modular Reactor, 700t in three sections, tallest is 23m tall. To big for SS9, but SS18 should be able to handle it. 24 Month refueling cycle is less than ideal. Uses standard light water reactor low enrichment fuel rods. Needs a below grade containment water pool to operate in. Uses the pool for no power passive cooling when off, and during emergency shutdowns. If all control power is shut off, the reactor naturally goes into a safe mode. Sounds like the reactor could be ignored for years if the pool size is large enough. With designed pool size, 5 months without any maintenance, and the only required maintenance is just adding water. Up to 12 reactors could be placed in one containment pool. Uses steam turbines to generate power. After turbine steam could be used for heating and water extraction too. The steam condenser obviously would need changing for use on Mars. Total cost for the Idaho demonstration project is expected to be $2.5B, and will have 12 reactors for 685 MWe produced.
https://www.nuscalepower.com/technology/technology-overview (https://www.nuscalepower.com/technology/technology-overview)

Title: Re: Power options for a Mars settlement
Post by: DAZ on 11/18/2019 02:21 am
I was very disappointed with the article from the Bulletin of the Atomic Scientists.  It seemed to intentionally ignore the simplest solutions while simultaneously pointing out the worst of all previous old designs.  It ignores molten salt reactor designs.  It’s almost as if they’re trying to intentionally discourage the use of atomic power.  What they say about the reactor designs that they do discuss is essentially accurate but almost none of it applies to liquid-fueled molten salt reactor designs.  The solid fuel reactor designs that are either water-cooled or gas-cooled depend on engineering designs for their safety.  And as they point out these designs can be defeated by an intentional attack.  A liquid-fueled molten salt reactor design is inherently safe because the physics will not allow it to be anything other than inherently safe.

The World Nuclear Association article mentions many reactor types.  Buried way down near the bottom, they mention liquid-fueled thorium reactors.  These reactors are molten salt cooled reactor with the thorium fuel suspended in the coolant.  These can be either burner or breeder designs.  With a burner design it is very much possible to build (theoretically) an LFTR that is inherently safe, could last with five years between refueling, and highly efficient.  This last part also means that they can be much smaller in physical design and weight.  You could scale the design from anywhere from about 1 MW up to 1 GW.  A 10 MW design could be in something the size of 1 to 3 tractor-trailers size vehicles.  This is possible because the thorium reactions operate in the thermal neutron range which means the reactor sizes can be very much smaller.  Being a molten salt design they can operate at much higher temperatures in the much smaller package.  With these higher temperatures you don’t need to use steam turbines, which are inherently large and heavy.  Instead of steam you can use supercritical CO2.  These are approximately 1/10 the size of the same size steam turbines.  Many of these advantages were not brought out in this article.

Much new work is being accomplished on molten salt reactor designs.  Many startup companies are looking at having prototype designs up and operating in 5 to 8 years.  The original work on these designs was started in the 60s but was not in favor as all of the previous work had been done on solid fuel designs based on the highest efficiency of making nuclear bomb grade material.  Although it is technically possible to use LFTR design to make nuclear bomb material, it is poorly suited to this task.  Because it operates in the thermal range it generates by orders of magnitude less Long live radioactive material.

If you were to hit one with a bomb, you would scatter the coolant only as far as the bomb would throw the coolant.  The coolant would then rapidly cool and solidify.  The coolant used is not soluble in water.  So it would pretty much stay wherever it landed.  Within a few months you could walk around and start picking it up with tongs and putting them in containers.  It would be much easier to decontaminate the site then it would be for most chemical spills.  Even when you wish to decommission the reactor is still much easier to deal with than its solid fuel counterpart.  You drain the liquid fuel into multiple small containers that are well shielded.  These are then easy to transport safely.  The reactor itself is still slightly radioactive due to neutron activation, but after about six months it too can be safely transported.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/18/2019 01:35 pm
For fuel production Mars, it's hard to imagine anything beating solar PV.  And fuel will be the vast majority of the power usage.  There's no need for batteries, just turn-off the electrolyzers at night.

But for always-on power to support life support etc, nukes have got to beat batteries (after the first few hours at least).

Beat batteries on mass? Probably. Beat batteries on total cost? Unlikely.


Also, life support systems can use a similar trick as fuel production to buffer energy without needing batteries:

• For oxygen supply, store excess O2 production as LOX. This will already be done on Mars as part of the methalox production process.

• For CO2 scrubbing, regenerate a reserve supply of LiOH beds (the regeneration step uses the vast majority of the energy).

• For potable water, stabilize with iodine and store it in a tank.

• For habitat heating, super-insulate the habitat and use a thermal mass battery (ideally this thermal mass function could be combined with the radiation shielding regolith and/or water. And naturally, you can burn stored methalox too.

• For dehumidification, hygroscopic interior cob walls (made of in-situ material) can buffer a surprising amount of humidity. These can also be done as a cob surface finish over Compressed Mars Blocks or other materials.

• For stored food there are many options (MREs, bulk food, etc).

The engineering trade-off here is exactly the same as for fuel production electrolysis: oversizing the production system (or more likely, carrying a larger number of identical oxygen/water/CO2 modules) and having additional consumable storage capacity. Of course such a critical system as life support probably demands this type of multi-level redundancy anyway.

Increasing those system margins a bit more yields plenty of energy storage within the life support system itself, and the "always-on power" requirement almost disappears. Your life support electricity requirements drop to just ventilation (for the CO2 scrubbers), dehumidification (needed for steady-state operation after few days when the hygroscopic cob surfaces become hydrated to their upper design limit) and LED lighting.

Obviously each of these "energy storage systems" (and numerous other possible options) would need to pass an engineering cost-trade analysis against simply carrying an equivalent amount of batteries. But I think they're all sound (with the possible exception of the cob walls, but I'm a sucker for cob walls :D ).


Edit: oops, forgot that the CO2 scrubbers require dehumidified air to function. C'est la vie! Cob walls, we hardly knew yee.


Dehumidifying can be done via heat exchanger. Chill, condense, drain. Cold is one resource Mars has plenty off. This is low energy too.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 11/18/2019 02:27 pm
I was very disappointed with the article from the Bulletin of the Atomic Scientists.  It seemed to intentionally ignore the simplest solutions while simultaneously pointing out the worst of all previous old designs.  It ignores molten salt reactor designs.  It’s almost as if they’re trying to intentionally discourage the use of atomic power.  >

That is precisely their purpose. That their Executive Chair is an anti-nuclear ex-politician says much.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/18/2019 03:58 pm
[SNIP]


Dehumidifying can be done via heat exchanger. Chill, condense, drain. Cold is one resource Mars has plenty off.

The issue is not a scarcity of cold outside. The issue is the scarcity of warmth inside. ;)

This is low energy too.

This is only "low energy" in the same way that holding the front door wide open in the wintertime is "low energy" because the door is easy to push.

A modern dehumidifier will condense 3-4 units of latent heat for each unit of electricity needed, and all that heat energy remains within the hab thermal envelope (effectively making the dehumidifiers into "400-500% efficient" space heaters). So an open-loop dehumidification system would need 3-4x as much power delivered as heat energy (cue someone explaining "energy quality" :D).

It would be a nice backup redundant system (especially since your CO2 scrubbers don't work without dehumidification), but it's not particularly low power.


Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/19/2019 11:29 am
[SNIP]


Dehumidifying can be done via heat exchanger. Chill, condense, drain. Cold is one resource Mars has plenty off.

The issue is not a scarcity of cold outside. The issue is the scarcity of warmth inside. ;)

This is low energy too.

This is only "low energy" in the same way that holding the front door wide open in the wintertime is "low energy" because the door is easy to push.

A modern dehumidifier will condense 3-4 units of latent heat for each unit of electricity needed, and all that heat energy remains within the hab thermal envelope (effectively making the dehumidifiers into "400-500% efficient" space heaters). So an open-loop dehumidification system would need 3-4x as much power delivered as heat energy (cue someone explaining "energy quality" :D ).

It would be a nice backup redundant system (especially since your CO2 scrubbers don't work without dehumidification), but it's not particularly low power.

You really need to stop injecting facts into my noodling. You can prove ANYTHING with facts.  ::)

Phil
Title: Re: Power options for a Mars settlement
Post by: Nathan2go on 11/21/2019 05:03 am
I was very disappointed with the article from the Bulletin of the Atomic Scientists. ....  It ignores molten salt reactor designs.    ...

Fun fact: the modern molten salt reactor concept was revived by an engineer at NASA, Kirk Sorenson, who was digging through the archives of Oakridge National Labs, looking for a reactor technology that was suitable for space applications.  He got a small bit of funding to scan the old 1960's era documents and put them on the internet.  He got excited about the potential benefits here on Earth, and then built the Energy From Thorium website, and kicked-off the movement.  Now Terrestrial Energy and Thorcon are in a race to build the first commercial molten salt reactors.

That said, there are a few misconceptions in your comment. 

Operating in the thermal neutron spectrum makes the reactor bigger, not smaller.  For thermal reactors, for every liter of fuel in the core, there are over 10 liters of moderator (i.e water or graphite), which is needed to slow down the neutrons.  Probably most space reactors have been fast-spectrum to avoid the extra core volume.  The advantage of thermal is that you need much less fissile fuel in the core, and lower enrichment to make it critical (the slow moving neutrons are much more reactive) - a cost benefit; plus several safety benefits such as with slow neutrons it's easier to guarantee that the reaction won't get out of control and make a big boom.

Molten salt does make the system small, because the salts are really good heat carriers per unit volume: almost as good as water, but much better than liquid metal or gas.  Also, the higher temp makes it easier to get rid of shutdown/after heat by radiation, rather than using huge ponds of water.

Regarding turbine size, steam turbines on Mars and the Moon will be small too.  The biggest part of a steam turbine is the low pressure sections: they go all the way from about 100 bar for the tiny high pressure first stages, to 0.1 bar for the huge low pressure stages.  They include such low pressure stages in order to get as much heat energy as possible out of the steam, before dumping the remaining energy (~30C) into the cooling towers/ocean.  But that thin Martian air is a poor heat conductor, so maybe we won't use cooling towers at all.  Maybe we'll use radiant coolers (like on a space probe RTG).  These work best at rather high temps, say 100-300C.  So the lowest pressure turbine stages are 1 bar or above, 10x smaller than normal.  This also means you need a turbine inlet temp that's much higher to get reasonable efficiency, so water cooled reactors won't work (300C max), hence the interest in molten salt or gas cooled (700+ C max).

Lastly, the reduction in long-lived radioactivity is a result of reprocessing the spent fuel, and returning the trans-uranics to the reactor to be burned as part of the renewed fuel.  Reprocessing is cheaper for a fuel that starts and ends in liquid form, but still might be too complex to bother for early Mars bases.  The Travelling Wave reactor is a cool alternative solution to the breeder problem, that does not require re-processing (hence could be attractive for a Mars base), but again without reprocessing, you'll need to dispose of that long-lived waste; also I think these use sodium coolant, which means the temp is limited to 450C so the efficiency won't be as good as for molten salt.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 11/21/2019 12:05 pm
The Travelling Wave reactor is a cool alternative solution to the breeder problem, that does not require re-processing (hence could be attractive for a Mars base), but again without reprocessing, you'll need to dispose of that long-lived waste...

As I understand it, TerraPower's Traveling Wave Reactor doesn't require additional effort to dispose of waste.

Their small modular reactors are completely self-contained, with enough fuel installed at manufacture to last 40-60 year (https://en.wikipedia.org/wiki/TerraPower#Traveling_wave_reactor)s. When that runs out, the sealed reactor container becomes the means of disposal.
It's designed to last thousands of years buried underground.

So when it's installed, they bury it a safe distance away from the settlement. After 40-60 years, when the fuel is spent, they bury a new one next to it and leave the old one buried there. The reactor itself is the means of disposal.

Also, since the main fuel source is not radioactive, launching from Earth is relatively safe.
Depleted uranium is less toxic than lead (https://www.ncbi.nlm.nih.gov/pubmed/24594921).

It's also worth mentioning that nuclear power is the safest source of electricity on Earth.
The number of deaths per terawatt-hour is lowest for nuclear.

To be clear, I think solar and nuclear are an ideal combination.
People generally use more electricity during daylight hours.
So nuclear supplies the baseline power, and solar provides the extra power during daylight.
If either system fails, the other provides a backup.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/09/2019 02:18 am
Power for a Martian settlement.  Propellant and food production are the main power drains.
This is for a large growing colony, that is producing most of its own food and propellant for all ships.

Numbers are per person.

I'm thinking, like Dave G. above, that in the long term we might want a nuclear base load, perhaps 10-20% of installed power would be good, just to get the colony through dust storms.  This is probably not sustainable on Mars alone, would need input from Earth or asteroids.  I guess in the first few decades we will know definitively if there are any reasonable uranium or thorium ore deposits on Mars.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/09/2019 02:23 am
The Travelling Wave reactor is a cool alternative solution to the breeder problem, that does not require re-processing (hence could be attractive for a Mars base), but again without reprocessing, you'll need to dispose of that long-lived waste...

As I understand it, TerraPower's Traveling Wave Reactor doesn't require additional effort to dispose of waste.

Their small modular reactors are completely self-contained, with enough fuel installed at manufacture to last 40-60 year (https://en.wikipedia.org/wiki/TerraPower#Traveling_wave_reactor)s. When that runs out, the sealed reactor container becomes the means of disposal.
It's designed to last thousands of years buried underground.

So when it's installed, they bury it a safe distance away from the settlement. After 40-60 years, when the fuel is spent, they bury a new one next to it and leave the old one buried there. The reactor itself is the means of disposal.

Also, since the main fuel source is not radioactive, launching from Earth is relatively safe.
Depleted uranium is less toxic than lead (https://www.ncbi.nlm.nih.gov/pubmed/24594921).

It's also worth mentioning that nuclear power is the safest source of electricity on Earth.
The number of deaths per terawatt-hour is lowest for nuclear.

To be clear, I think solar and nuclear are an ideal combination.
People generally use more electricity during daylight hours.
So nuclear supplies the baseline power, and solar provides the extra power during daylight.
If either system fails, the other provides a backup.
I think the potential deaths per TWh of nuclear are significant.  In particular if the quantity of generation goes up.  They've been lucky.  And very very very very careful :-)
Title: Re: Power options for a Mars settlement
Post by: RobLynn on 12/09/2019 07:01 pm
I was very disappointed with the article from the Bulletin of the Atomic Scientists. ....  It ignores molten salt reactor designs.    ...

Fun fact: the modern molten salt reactor concept was revived by an engineer at NASA, Kirk Sorenson, who was digging through the archives of Oakridge National Labs, looking for a reactor technology that was suitable for space applications.  He got a small bit of funding to scan the old 1960's era documents and put them on the internet.  He got excited about the potential benefits here on Earth, and then built the Energy From Thorium website, and kicked-off the movement.  Now Terrestrial Energy and Thorcon are in a race to build the first commercial molten salt reactors.

That said, there are a few misconceptions in your comment. 

Operating in the thermal neutron spectrum makes the reactor bigger, not smaller.  For thermal reactors, for every liter of fuel in the core, there are over 10 liters of moderator (i.e water or graphite), which is needed to slow down the neutrons.  Probably most space reactors have been fast-spectrum to avoid the extra core volume.  The advantage of thermal is that you need much less fissile fuel in the core, and lower enrichment to make it critical (the slow moving neutrons are much more reactive) - a cost benefit; plus several safety benefits such as with slow neutrons it's easier to guarantee that the reaction won't get out of control and make a big boom.

Molten salt does make the system small, because the salts are really good heat carriers per unit volume: almost as good as water, but much better than liquid metal or gas.  Also, the higher temp makes it easier to get rid of shutdown/after heat by radiation, rather than using huge ponds of water.

Regarding turbine size, steam turbines on Mars and the Moon will be small too.  The biggest part of a steam turbine is the low pressure sections: they go all the way from about 100 bar for the tiny high pressure first stages, to 0.1 bar for the huge low pressure stages.  They include such low pressure stages in order to get as much heat energy as possible out of the steam, before dumping the remaining energy (~30C) into the cooling towers/ocean.  But that thin Martian air is a poor heat conductor, so maybe we won't use cooling towers at all.  Maybe we'll use radiant coolers (like on a space probe RTG).  These work best at rather high temps, say 100-300C.  So the lowest pressure turbine stages are 1 bar or above, 10x smaller than normal.  This also means you need a turbine inlet temp that's much higher to get reasonable efficiency, so water cooled reactors won't work (300C max), hence the interest in molten salt or gas cooled (700+ C max).

Lastly, the reduction in long-lived radioactivity is a result of reprocessing the spent fuel, and returning the trans-uranics to the reactor to be burned as part of the renewed fuel.  Reprocessing is cheaper for a fuel that starts and ends in liquid form, but still might be too complex to bother for early Mars bases.  The Travelling Wave reactor is a cool alternative solution to the breeder problem, that does not require re-processing (hence could be attractive for a Mars base), but again without reprocessing, you'll need to dispose of that long-lived waste; also I think these use sodium coolant, which means the temp is limited to 450C so the efficiency won't be as good as for molten salt.

Elysium's fast spectrum chloride salt reactor looks very promising.  ~600°C for high thermal efficiency (less waste heat to get rid of). Control relies on thermal expansion of salt - reduce cooling and salt naturally expands reducing reactivity/output, though can also drain reactor as necessary, makes control mostly passive.  Long-term very efficient in fuel use (runs on un-enriched Uranium) and low waste, though need many tonnes of enriched fuel to start breeding from U238 or Thorium).  Overall simplicity, efficiency and modest mass are a good match for Mars base.
Title: Re: Envisioning Amazing Martian Habitats
Post by: sghill on 12/10/2019 03:49 pm
From a tile-game strategy POV, you've trapped your core making expansion harder. I would've put the solar times on the other side of what I assume are the first two landers-cum-storage-tanks? Unless there a special resource tile in that area that hasn't been accessed yet but needs to be kept for future expansion once you level up your processing plant.
I almost always lose at board games.  Terrible at strategy.  In this case, I would expect that the solar panels could be moved to open up a road, at the cost of wasted energy and time. Guess that's one of the lessons this type of analysis might highlight :-)
That's an important real life tradeoff as well. Do you site something close by, to make things more efficient now, and then move it later, or do you site it a ways out, at the cost of less efficiency now but no loss of production later.

I used to scout PV panel sites all the time. So I'll throw in my two cents.

First, I am going to repeat a conversation we had a few years back ( https://forum.nasaspaceflight.com/index.php?topic=37808.msg1416755#msg1416755 ) about AC versus DC power on Mars and restate that the power grid on Mars is almost certainly going to be DC instead of AC power. Why? Because you get roughly a ten to one efficiency bump (or alternatively, you need 10 times fewer panels) over AC systems.  This really isn't a problem for all but the most commoditized equipment (cheap coffee makers and such).

It matters in the context of Lar's question in two ways:

First, thin film panels can come in spools and be rolled out and fixed to the ground with camping stakes, then moved further away when the need arises- a happy problem.

Second, DC power systems are horribly inefficient for transmitting long distances. On Mars, this is also a happy problem to have because it means you have a growing civilization there. However, the transmission distances for even a modest sized town are so miniscule that the distance losses are pretty irrelevant.

Finally, let's assume the town is growing so much that the original site needs to be moved further back. I doubt "all" available land will be filled up during the useful lifetime of the original panel farm (about 25-30 years on Earth), so they may just scrap the old site and use the panel mounts at a new site. Even if they do still want to keep those older panels, they can move the panel farm in segments to it's new location. The whole farm doesn't come off-line for the move, just individual strings.





Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: Twark_Main on 12/10/2019 04:56 pm
[snip]

I used to scout PV panel sites all the time. So I'll throw in my two cents.

First, I am going to repeat a conversation we had a few years back ( https://forum.nasaspaceflight.com/index.php?topic=37808.msg1416755#msg1416755 ) about AC versus DC power on Mars and restate that the power grid on Mars is almost certainly going to be DC instead of AC power. Why? Because you get roughly a ten to one efficiency bump (or alternatively, you need 10 times fewer panels) over AC systems.

How do you figure?

Because at first glance, those numbers seem quite impossible. For example, the Tesla Powerwall 2 (which includes the DC-to-AC inverter inside) has an efficiency of 89% in the AC version, and 92% in the DC version. This efficiency number includes inverter losses in addition to battery round-trip loss, but let's be generous and assume the latter is zero.

https://electrek.co/2016/10/28/tesla-powerwall-2-game-changer-in-home-energy-storage-14-kwh-inverter-5500/

That means that even if the DC system operated at 100% efficiency, it would only produce 1/.89 = 1.12x as much power as the AC system, not 10x.

How did you calculate 10x?
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: lamontagne on 12/10/2019 05:09 pm
From a tile-game strategy POV, you've trapped your core making expansion harder. I would've put the solar times on the other side of what I assume are the first two landers-cum-storage-tanks? Unless there a special resource tile in that area that hasn't been accessed yet but needs to be kept for future expansion once you level up your processing plant.
I almost always lose at board games.  Terrible at strategy.  In this case, I would expect that the solar panels could be moved to open up a road, at the cost of wasted energy and time. Guess that's one of the lessons this type of analysis might highlight :-)
That's an important real life tradeoff as well. Do you site something close by, to make things more efficient now, and then move it later, or do you site it a ways out, at the cost of less efficiency now but no loss of production later.

I used to scout PV panel sites all the time. So I'll throw in my two cents.

First, I am going to repeat a conversation we had a few years back ( https://forum.nasaspaceflight.com/index.php?topic=37808.msg1416755#msg1416755 ) about AC versus DC power on Mars and restate that the power grid on Mars is almost certainly going to be DC instead of AC power. Why? Because you get roughly a ten to one efficiency bump (or alternatively, you need 10 times fewer panels) over AC systems.  This really isn't a problem for all but the most commoditized equipment (cheap coffee makers and such).

It matters in the context of Lar's question in two ways:

First, thin film panels can come in spools and be rolled out and fixed to the ground with camping stakes, then moved further away when the need arises- a happy problem.

Second, DC power systems are horribly inefficient for transmitting long distances. On Mars, this is also a happy problem to have because it means you have a growing civilization there. However, the transmission distances for even a modest sized town are so miniscule that the distance losses are pretty irrelevant.

Finally, let's assume the town is growing so much that the original site needs to be moved further back. I doubt "all" available land will be filled up during the useful lifetime of the original panel farm (about 25-30 years on Earth), so they may just scrap the old site and use the panel mounts at a new site. Even if they do still want to keep those older panels, they can move the panel farm in segments to it's new location. The whole farm doesn't come off-line for the move, just individual strings.
With modern HVDC technology even distance s no longer an issue.  You need pretty expensive rectifier stations though.  And you probably can't have ground return on Mars, so any transmission infrastructure will have some added costs for the ground return wiring, and the magic 3x120 degrees phase addition = no return might give AC an edge.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/10/2019 06:27 pm
Grid Battery, 10x10

In the "Grid" (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437) concept, there is a gap in power coverage.  While the grid might give 10/50 power (10 MW to 50 deg latitude) continuously under most circumstances, the calm late-night hours following a regional storm would open a gap.  Here the regional farms' suggested PV, atmospheric triboelectric, and wind triboelectric power sources fail concurrently.  Here the grid can't deliver the contracted minimum 10 MW, and we might scale the issue beyond the scenario's nominal 2.1 hour gap to address a greater round-number gap of, say, 10 hours.

What batteries might best fill this 10x10 gap?

One approach:  saltwater battery farm

(https://www.altestore.com/blog/wp-content/uploads/2016/03/aquion-salt-water-battery-module-at-altestore.com_-300x271.jpg)

Image:  Aquion saltwater battery module (http://aquionenergy.com/technology/deep-cycle-battery/), 1.3 m wide, 48V 579AH.

Aquion batteries use NaClO4 electrolyte, and such batteries can also use a blended electrolyte (https://patents.google.com/patent/US8298701B2/en).  For example, KClO4 and Mg(ClO4)2 can be blended in.  All of these perchlorate salts are readily obtained from martian regolith fines, through evaporation of a cleaned regolith brine; therefore, ISRU water and salt can give most of the battery mass.

Such a battery operates well at -5 C, and salts prevent freezing.  The exothermal discharge reaction could maintain the operating temperature during night operation on Mars. 

To meet 10x10 requirement, we can estimate (https://www.altestore.com/blog/2016/03/the-rise-of-aquion-batteries-clean-safe-energy-storage/#.Xe_j4dJOnb1) a need for ~ 5000 modules patterned after the Aquion example.  They'd cover an area a bit larger than a football field.  Dry battery case cargo would comprise roughly two Starship payloads.

Other battery options at 10x10 scale?
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 12/10/2019 07:21 pm
After a quick google search for Grid Battery...
Can you point me some specs?  Thanks.

Efficiency, charging cycle and lifetime and cost.
How do these compare to lead acid batteries? 
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/10/2019 07:36 pm
After a quick google search for Grid Battery...
Can you point me some specs?  Thanks.

Efficiency, charging cycle and lifetime and cost.
How do these compare to lead acid batteries?

You wouldn't want to bulk-ship massive lead batteries to Mars.

Grid scenario details and battery performance #s at links above.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 12/10/2019 09:43 pm
After a quick google search for Grid Battery...
Can you point me some specs?  Thanks.

Efficiency, charging cycle and lifetime and cost.
How do these compare to lead acid batteries?

You wouldn't want to bulk-ship massive lead batteries to Mars.

Grid scenario details and battery performance #s at links above.

Lead is on Mars. 
Title: Re: Power options for a Mars settlement
Post by: Lar on 12/10/2019 10:26 pm
Lead is on Mars. 

In similar concentrations or similar extraction difficulty levels as the salts?

A low efficiency battery that can be 99.5% ISRU is attractive even if better density is available from imports...
Title: Re: Power options for a Mars settlement
Post by: Nomadd on 12/10/2019 11:29 pm
After a quick google search for Grid Battery...
Can you point me some specs?  Thanks.

Efficiency, charging cycle and lifetime and cost.
How do these compare to lead acid batteries?

You wouldn't want to bulk-ship massive lead batteries to Mars.

Especially considering that Lithium ion will probably hit a 10 to 1 weight advantage over the best lead acid in a few years, with a much longer lifespan.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 12/11/2019 12:25 am
After a quick google search for Grid Battery...
Can you point me some specs?  Thanks.

Efficiency, charging cycle and lifetime and cost.
How do these compare to lead acid batteries?

You wouldn't want to bulk-ship massive lead batteries to Mars.

Especially considering that Lithium ion will probably hit a 10 to 1 weight advantage over the best lead acid in a few years, with a much longer lifespan.

Lithium ion batteries as a finished product  will be imported from Earth for a long time. 
I thought lead was available on Mars. 
I was looking for a easy to build batteries on Mars to supplement lithium ion batteries. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/11/2019 02:19 am
After a quick google search for Grid Battery...
Can you point me some specs?  Thanks.

Efficiency, charging cycle and lifetime and cost.
How do these compare to lead acid batteries?

You wouldn't want to bulk-ship massive lead batteries to Mars.

Especially considering that Lithium ion will probably hit a 10 to 1 weight advantage over the best lead acid in a few years, with a much longer lifespan.

Lithium ion batteries as a finished product  will be imported from Earth for a long time. 
I thought lead was available on Mars. 
I was looking for a easy to build batteries on Mars to supplement lithium ion batteries.
Do we really need batteries?  Except for vehicles and possibly the very early base?  Let's say we use compressed gas storage, or pumped storage (Mars has a lot of very high cliffs that might be just right for that technology) can we produce on Mars the physical elements of the storage system  that can compensate for the lower efficiency by allowing for the delivery of more solar panels? 

Let's say we use some other system with 15% more losses
And we store about 10% of our energy production
We need 15/10 =1,5% more solar to compensate.

So the effect of lower efficiency is minimal, what matters more is lower mass of transported material per kWh of storage.  Zinc-air or potassium air might be used, although they may depend on Earth's oxygen rich atmosphere.
Compressed air storage needs heavy tanks.  If the steel can be produced cheaply on Mars, they might be competitive.
Steel requires about 15 kWh/kg of energy to produce, and 1m2 of solar panel on mars produces about 1kWh per day.
So over two weeks you might be able to produce a 1 kg pressure vessel.  Wonder how much energy that could store?


Title: Re: Power options for a Mars settlement
Post by: Paul451 on 12/11/2019 08:28 am
or pumped storage (Mars has a lot of very high cliffs that might be just right for that technology)

Pumped energy storage is weak unless you have an existing (or reasonably creatable) large, open, high altitude reservoir and dam that you can pump into.

It's that E=m.g.h, ~1kWhr per tonne per metre of height (on Mars). To make up for a low height (and in this case, low-g) you need a high mass, which means a large reservoir/dam system. Not an issue if you have a dam that can store millions of tonnes of water behind it. But if you need to pump into limited sized tanks at the top of a cliff, then to make up for that low usable mass, you need a ridiculously big height. (Given the lack of surface water storage, it's probably as equipment/construction/labour/maintenance efficient to use a system that elevates bulk dry mass (for eg, regolith/waste.))

But whatever you use, the numbers are crap even if you ignore the efficiency losses in recovering the energy. (I suspect the same is true of pressurised gas energy storage. Of course, not as dumb an idea as triboelectric generation, but still.)
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: Twark_Main on 12/11/2019 10:04 am
[snip]
With modern HVDC technology even distance s no longer an issue.  You need pretty expensive rectifier stations though.  And you probably can't have ground return on Mars, so any transmission infrastructure will have some added costs for the ground return wiring, and the magic 3x120 degrees phase addition = no return might give AC an edge.

If using 3 phase AC, does that mean we can baseline a colony to use the T-pylon from Bystrup? When made of steel the design is half as heavy as a conventional UK A-frame transmission pylon (10 tonnes vs 20 tonnes). A good start.

It could be made of Mars steel, or lightweight materials like carbon or basalt fiber. I would imagine a lightweight design which replaces the upper cross-arm with a prefab truss, and switching from a monopole to a guyed mast (two diagonal guy wires extending from each cross-arm). Heavier monopoles would only be used where space is limited.

Incidentally, the triangular conductor layout results in a smaller EMF footprint than the three-in-a-row configuration.
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: lamontagne on 12/11/2019 10:54 am
As far as I know, the cheapest type of pylon is the guyed wire type, when you have the space for it.

T-pylon seems like a nice solution when you are worried about visual impact.  Which is most of the time on Earth, but not so much on Mars.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/11/2019 11:00 am
or pumped storage (Mars has a lot of very high cliffs that might be just right for that technology)

Pumped energy storage is weak unless you have an existing (or reasonably creatable) large, open, high altitude reservoir and dam that you can pump into.

It's that E=m.g.h, ~1kWhr per tonne per metre of height (on Mars). To make up for a low height (and in this case, low-g) you need a high mass, which means a large reservoir/dam system. Not an issue if you have a dam that can store millions of tonnes of water behind it. But if you need to pump into limited sized tanks at the top of a cliff, then to make up for that low usable mass, you need a ridiculously big height. (Given the lack of surface water storage, it's probably as equipment/construction/labour/maintenance efficient to use a system that elevates bulk dry mass (for eg, regolith/waste.))

But whatever you use, the numbers are crap even if you ignore the efficiency losses in recovering the energy. (I suspect the same is true of pressurised gas energy storage. Of course, not as dumb an idea as triboelectric generation, but still.)
Yes, the tank costs probably kill most of the pressure/gravity storage system ideas.  Mars does have a large number of high cliffs though.  But in the long term in may have extensive lithium salt beds as well, who knows?
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/11/2019 04:04 pm
the numbers are crap even if you ignore the efficiency losses in recovering the energy. (I suspect the same is true of pressurised gas energy storage. Of course, not as dumb an idea as triboelectric generation, but still.)

We shouldn't mock numbers we don't know.  Adiabatic compressed air energy storage (ACAES) has > 70% round-trip efficiency.  And if you can implement ACAES in ice chambers (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1935540#msg1935540), you don't need to build storage vessels.

If.

Also, Baumgaertner (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1865539#msg1865539) and Seol (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1867784#msg1867784) know martian triboelectricity rather well.  You might think twice about calling them "dumb".

--

But re batteries: 

What alternate martian ISRU system might give batteries that serve better than perchlorate saltwater batteries, in a farm scenario (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2024040#msg2024040)?

(http://aquionenergy.com/wp-content/uploads/2016/02/stack_02.jpg)

Image:  Aquion's Aspen saltwater battery

Those Aquion battery modules (http://aquionenergy.com/technology/deep-cycle-battery/) have desirable qualities:  good sub-zero performance, long service life, non-corrosive chemistry, easy infrequent maintenance, no moving parts, etc.  And the ISRU loading process seems relatively straightforward, since it uses abundant electrolytes that require no manufacturing beyond evaporative salt harvest.

So these batteries would ship as empty shells, to be filled with water and perchlorate salts on-site.  What alternate battery system might be cheaper / lighter / simpler, in this scenario?
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: sghill on 12/11/2019 04:23 pm
As far as I know, the cheapest type of pylon is the guyed wire type, when you have the space for it.

T-pylon seems like a nice solution when you are worried about visual impact.  Which is most of the time on Earth, but not so much on Mars.

If Mars has grown to the point that long distance transmission lines are needed, this whole conversation is a moot point...
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/11/2019 04:37 pm
Let's say we use... pumped storage (Mars has a lot of very high cliffs that might be just right for that technology) can we produce on Mars the physical elements of the storage system  that can compensate for the lower efficiency...

Well, pumped-storage hydroelectricity has > 80% round-trip efficiency, on Earth or Mars.  And a 100,000 m3 reservoir at 1 km elevation would have PE to meet the illustrative 10x10 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2024040#msg2024040) power requirement.

Assuming terrain is suitable for such a reservoir, how might you construct and operate it under martian conditions, while holding cargo mass to the two payloads (max 300 t total) required for an equivalent saltwater battery farm?
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 12/11/2019 05:11 pm
I'm not saying this can't be done.  I'm saying there are a lot of unknowns, building this unique infrastructure would  take a lot of effort. 

Look at all the places batteries are used today. 
Using existing and well understood technology
Batteries could be a bridge and reserve between different power systems. 
Lithium ion batteries (imported for years) and some form of locally built battery. 
Title: Re: Power options for a Mars settlement
Post by: Eka on 12/11/2019 10:30 pm
Assuming terrain is suitable for such a reservoir, how might you construct and operate it under martian conditions, while holding cargo mass to the two payloads (max 300 t total) required for an equivalent saltwater battery farm?
With some methods that prevent frozen pipes... Oops, did I just use up all the stored power?

The salt batteries sound like a lot easier to implement.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 12/12/2019 05:04 am
the numbers are crap even if you ignore the efficiency losses in recovering the energy. (I suspect the same is true of pressurised gas energy storage. Of course, not as dumb an idea as triboelectric generation, but still.)
We shouldn't mock numbers we don't know.  Adiabatic compressed air energy storage (ACAES) has > 70% round-trip efficiency.

I actually said "even if you ignore the efficiency losses", I was pointedly treating the numbers as theoretical perfect efficiency and just looking at scale.

(However: In reality, that "> 70%" comes from simulations (71-74%), it doesn't come from the few small-scale systems that have been built. In simulation, pumped storage gets 90+%. In practice, around 70% for good sites. Lofted bulk mass can get 80% or better in practice, even on small scales. But again, it's the scale that sucks. Batteries typically run at better than 90%. A very bad battery is more efficient than a good pumped storage system.)

And if you can implement ACAES in ice chambers (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1935540#msg1935540), you don't need to build storage vessels.

The link was to your own speculation. (And misunderstands the adiabatic part. You need an insulated storage vessel for the heat, and it only works as long as you can retain that heat. A) That still limits your scale. B) Is worthless for long dust-storms that are preventing day-time energy production.)

Of course, not as dumb an idea as triboelectric generation, but still.)
Also, Baumgaertner (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1865539#msg1865539) and Seol (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1867784#msg1867784) know martian triboelectricity rather well.  You might think twice about calling them "dumb".

Again you only linked to your own previous comments, and the following comments by others pointed out that the paper at the start of the thread briefly mentions the need for alternative Mars power, but that the body of the paper didn't provide support for it, and you either misread it or didn't understand it. (They also criticised the conclusions in the paper itself as being unsupported by the body, or requiring naive assumptions.)

It's also worth noting that the "NG" in TENG stands for nanogeneration. This is a lab development where the typical MEMS-surface is on the scale of a drink coaster and requires clean-room conditions to operate. You are picturing something on the scale of a wind-turbine farm and comparing it with mature deployed technology. Actual TENG research is aiming for things on the scale of small remote or wearable sensors, etc. Nano-generation for micro-devices where batteries and solar are impractical. Large scale applications are the fluff in the university press release, or in the intro to a NASA funding proposal.
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: Oersted on 12/12/2019 09:26 am
If using 3 phase AC, does that mean we can baseline a colony to use the T-pylon from Bystrup? When made of steel the design is half as heavy as a conventional UK A-frame transmission pylon (10 tonnes vs 20 tonnes). A good start.

I see a lot of these T-pylons. Visually they are more obtrusive than steel lattice structures, despite protestations to the contrary from architects and designers. The thick towers look much heavier, visually, than classic A-frames. AFAIK the major reason for T-Pylons is reduced maintenance. I don't know if the usual A-frames aren't just a good for Mars.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/12/2019 01:42 pm
And if you can implement ACAES in ice chambers (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1935540#msg1935540), you don't need to build storage vessels.

The link was to your own speculation. (And misunderstands the adiabatic part. You need an insulated storage vessel for the heat, and it only works as long as you can retain that heat. A) That still limits your scale. B) Is worthless for long dust-storms that are preventing day-time energy production.)


You misunderstood the adiabatic heat store.  That's a simple thing:  e.g., roll out aerogel insulation, lay down a heat-exchange loop, and cover with regolith gravel.  Rock self-insulates to store heat overnight, as needed in the 10x10 scenario.  No vessel.  And it scales of course.

Of course, not as dumb an idea as triboelectric generation, but still.)
Also, Baumgaertner (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1865539#msg1865539) and Seol (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1867784#msg1867784) know martian triboelectricity rather well.  You might think twice about calling them "dumb".

Again you only linked to your own previous comments, and the following comments by others pointed out that the paper at the start of the thread briefly mentions the need for alternative Mars power, but that the body of the paper didn't provide support for it, and you either misread it or didn't understand it. (They also criticised the conclusions in the paper itself as being unsupported by the body, or requiring naive assumptions.)

It's also worth noting that the "NG" in TENG stands for nanogeneration. This is a lab development where the typical MEMS-surface is on the scale of a drink coaster and requires clean-room conditions to operate. You are picturing something on the scale of a wind-turbine farm and comparing it with mature deployed technology. Actual TENG research is aiming for things on the scale of small remote or wearable sensors, etc. Nano-generation for micro-devices where batteries and solar are impractical. Large scale applications are the fluff in the university press release, or in the intro to a NASA funding proposal.

No, Baumgaertner and Seol study triboelectricity as a source of Mars facility power, and the linked posts give refs and highlights.  You call their work "fluff" and "dumb", but that's just Paul451's view, not shared by NASA or the greater research community.

But do you understand why, for example, martian atmospheric triboelectricity can be harvested off solar panels (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1866798#msg1866798), at MW scale, during the storms you lament above?
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: KSHavre on 12/12/2019 02:41 pm
If using 3 phase AC, does that mean we can baseline a colony to use the T-pylon from Bystrup? When made of steel the design is half as heavy as a conventional UK A-frame transmission pylon (10 tonnes vs 20 tonnes). A good start.

I see a lot of these T-pylons. Visually they are more obtrusive than steel lattice structures, despite protestations to the contrary from architects and designers. The thick towers look much heavier, visually, than classic A-frames. AFAIK the major reason for T-Pylons is reduced maintenance. I don't know if the usual A-frames aren't just a good for Mars.

I think we are heading off track here, but my 2 or 3 cents:

Burying lines for short distances keeps them safe from vehicle accidents, and away from bouncing colonists trying to jump high enough to tap the lines (only on a dare of course)!

But save the weight of wire; it will be a long time before the colony outgrows the distance wireless power transmission would be viable.

And frankly, I want a refund on my ticket if you string a bunch of wires around the Mars-scape.... >:(
Title: Re: Power options for a Mars settlement
Post by: Lar on 12/12/2019 05:43 pm
No, Baumgaertner and Seol study triboelectricity as a source of Mars facility power, and the linked posts give refs and highlights.  You call their work "fluff" and "dumb", but that's just Paul451's view, not shared by NASA or the greater research community.

But do you understand why, for example, martian atmospheric triboelectricity can be harvested off solar panels (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1866798#msg1866798), at MW scale, during the storms you lament above?
(mod)
LMT: We gave you a triboelectric thread, didn't we?... here it is https://forum.nasaspaceflight.com/index.php?topic=46533 (notice how it's in "Advanced concepts"... that's because it's an advanced concept! Not like solar cells or batteries or nuclear power)

The salt water battery stuff you brought up seems like a fruitful area for discussion (although I worry about extreme cold, it's not insurmoutable). Triboelectric isn't. That's partly on you because of your inability to take critiques or to provide good sources[1].   ... strongly advise you stay away from it.  Not up for debate.

1 - linking to yourself is not 'providing good sources' ... that's not up for debate either.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/12/2019 07:02 pm
(notice how it's in "Advanced concepts"... that's because it's an advanced concept! Not like solar cells or batteries or nuclear power)

And I didn't bring it up.  Sure, folks can see the old thread for e.g. Baumgaertner's method (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1865539#msg1865539) of "stealing the storm's thunder".

The salt water battery stuff you brought up seems like a fruitful area for discussion (although I worry about extreme cold, it's not insurmoutable).

Well, it's hard to imagine an ISRU battery liquid that would withstand extreme cold better.  With perchlorate salt concentration of 3 M (https://patents.google.com/patent/US8298701B2/en), the battery wouldn't even begin to freeze above -40 C.  Thermal inertia would slow freezing.  And even in midwinter there's no particular challenge: a light aerogel wrap would prevent freeze-up between discharges, even under CO2 snow.

And don't forget, the battery heats itself, up to 100 C, when it discharges. 

Where's the cause for worry?
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: Tulse on 12/12/2019 08:14 pm
With wireless power transmission wouldn't you have the problem of bouncing colonists frying themselves by jumping into the beam?
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/12/2019 08:33 pm
r/Mars

Energy Options on Mars - Is there anything besides nuclear that is remotely viable? (https://www.reddit.com/r/Mars/comments/e9raou/energy_options_on_mars_is_there_anything_besides/)

Different ideas there.  Some of the mentioned concepts are arguably "advanced", so presumably out-of-scope here.
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: KSHavre on 12/12/2019 10:52 pm
With wireless power transmission wouldn't you have the problem of bouncing colonists frying themselves by jumping into the beam?

True! I was originally going to advocate underground; to save building all the towers along they way, but still a lot of wire. So 2 towers tall enough not to fry people are probably lighter and smaller than a bunch of towers along the way, and all the wire you would need. Thinking about the total system?

And, if someone dared me, I would more likely try to tap a power line with a wooden stick, than see if microwave or laser beams would actually fry my brains; I hope there is a limit to stupid human tricks... ;-p

We should probably pick topic up in the thread for Power Options for a Settlement on Mars:

https://forum.nasaspaceflight.com/index.php?topic=39785.1380
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: Twark_Main on 12/12/2019 11:34 pm
As far as I know, the cheapest type of pylon is the guyed wire type, when you have the space for it.

Thanks for that, quite a beautiful (and efficient) tensile design. Bucky Fuller would be proud. :D


If Mars has grown to the point that long distance transmission lines are needed, this whole conversation is a moot point...

What makes you say that?  ???

A Mars colony could be using high voltage transmission (not necessarily long distance) earlier than you think. It's the most mass efficient way to transmit large amounts of power: from a nearby microwave rectenna array, or from the solar farm to the sabatier reactor (ideally co-located, but later expansion phases may not be as close).

Or say you have two bases, <500 km apart. It would be nice to have an interconnect between their microgrids for additional electricity redundancy.

Frequency would likely be DC, or possibly 400 Hz (for the same reasons it's used in aircraft).
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: WormPicker959 on 12/13/2019 03:41 am
Doesn't high frequency cause more losses in long range transmission compared to lower frequency?

As far as I know, the cheapest type of pylon is the guyed wire type, when you have the space for it.

Thanks for that, quite a beautiful (and efficient) tensile design. Bucky Fuller would be proud. :D


If Mars has grown to the point that long distance transmission lines are needed, this whole conversation is a moot point...

What makes you say that?  ???

A Mars colony could be using high voltage transmission (not necessarily long distance) earlier than you think. It's the most mass efficient way to transmit large amounts of power: from a nearby microwave rectenna array, or from the solar farm to the sabatier reactor (ideally co-located, but later expansion phases may not be as close).

Or say you have two bases, <500 km apart. It would be nice to have an interconnect between their microgrids for additional electricity redundancy.

Frequency would likely be DC, or possibly 400 Hz (for the same reasons it's used in aircraft).
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: Twark_Main on 12/13/2019 07:58 am
[snip]
Frequency would likely be DC, or possibly 400 Hz (for the same reasons it's used in aircraft).

Doesn't high frequency cause more losses in long range transmission compared to lower frequency?

Doh, yep. Thanks. HVDC it is?

It's rather an interesting question: what frequency would a grid use if starting with 21st century technology? 50-60 Hz was optimized for AC motors and incandescent lights (both rather inefficient by modern standards). But increasingly the grid is interacting with wall warts/chargers, LEDs, high efficiency digital motor controllers, battery chargers (possibly bidirectional) and solar inverters. The heart of all these is the switching power supply.

It seems like all of these switching power supplies would become simpler/cheaper/more efficient if the grid used DC, because the rectification and LF smoothing stages get deleted. But DC could have safety issues with arc termination.i would be curious what household voltage would be best for a DC grid.

These posts really should be moved to the power options thread...
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: LMT on 12/13/2019 03:08 pm
HVDC it is?

UHVDC SWER would be extremely mass-efficient.


Grid

Power transmission:  Farms might connect through monopolar, ultra high voltage direct current (UHVDC) power cables.  UHV (800+ kV) cuts cable heating and mass; it’s required for the grid.  Monopolar / single-wire earth return (SWER) DC cuts cable mass and simplifies power distribution from DC farms.

Range:   UHVDC power is transmitted commercially on Earth beyond 3300 km, with total loss ~ 3% per 1000 km.  Performance improves under Mars night temperatures, where resistivity drops; with corresponding cut in required cable mass.  Also, martian power transmission losses are acceptably higher than terrestrial losses, as martian power is generated not from expensive fuels but from free electron sources.  Farm scale is simply increased to compensate.  Targeted range:  a useful transmission range of 8000 km might be a fair target.  If it’s attained, the grid can be configured to meet the 10/50 challenge:  10+ MW to 50° latitude, anytime...

Insulation:  The highly-conductive atmosphere produces arcing on uninsulated high-voltage lines, so insulation is needed.  Insulated cable can be deployed on the ground, without pylons; a very great convenience.  The insulator must be lightweight; options tbd.

Conductor:  Minimum useful conductor diameter depends on uncertain factors, but is conceivably < 1.5 cm.  Metal is too massive, but carbon is being introduced as lightweight graphite and carbon nanotubes (CNTs).  One example:  high-ampacity graphene/copper nanocomposite wire of Zhao et al. 2019.  Other advances are noted in the review of Zhang et al. 2019, which targets all-carbon power transmission...

(http://www.lakematthew.com/wp-content/uploads/2019/05/Grid_Farms.png)

Cartoon of an initial grid configuration.  Grid farms (equatorial white squares) are connected by UHVDC power transmission line.  Crewed facilities at Phlegra Montes glacier and Gale Crater (white circles) connect to the grid.

These posts really should be moved to the power options thread...
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: KSHavre on 12/13/2019 04:53 pm
HVDC it is?

UHVDC SWER would be extremely mass-efficient.


Grid

Power transmission:  Farms might connect through monopolar, ultra high voltage direct current (UHVDC) power cables.  UHV (800+ kV) cuts cable heating and mass; it’s required for the grid.  Monopolar / single-wire earth return (SWER) DC cuts cable mass and simplifies power distribution from DC farms.

Range:   UHVDC power is transmitted commercially on Earth beyond 3300 km, with total loss ~ 3% per 1000 km.  Performance improves under Mars night temperatures, where resistivity drops; with corresponding cut in required cable mass.  Also, martian power transmission losses are acceptably higher than terrestrial losses, as martian power is generated not from expensive fuels but from free electron sources.  Farm scale is simply increased to compensate.  Targeted range:  a useful transmission range of 8000 km might be a fair target.  If it’s attained, the grid can be configured to meet the 10/50 challenge:  10+ MW to 50° latitude, anytime...

Insulation:  The highly-conductive atmosphere produces arcing on uninsulated high-voltage lines, so insulation is needed.  Insulated cable can be deployed on the ground, without pylons; a very great convenience.  The insulator must be lightweight; options tbd.

Conductor:  Minimum useful conductor diameter depends on uncertain factors, but is conceivably < 1.5 cm.  Metal is too massive, but carbon is being introduced as lightweight graphite and carbon nanotubes (CNTs).  One example:  high-ampacity graphene/copper nanocomposite wire of Zhao et al. 2019.  Other advances are noted in the review of Zhang et al. 2019, which targets all-carbon power transmission...

(http://www.lakematthew.com/wp-content/uploads/2019/05/Grid_Farms.png)

Cartoon of an initial grid configuration.  Grid farms (equatorial white squares) are connected by UHVDC power transmission line.  Crewed facilities at Phlegra Montes glacier and Gale Crater (white circles) connect to the grid.

These posts really should be moved to the power options thread...

Before this thread moves, I have to chime in again. One of the main reasons AC won over DC, was due to the power generation technology. they were building a very few extremely large power plants to sell to many cities. AC was more efficient for high volume long distance transmission. Earth is already switching to distributed power over very sort distances, and removing the DC-AC-DC gear and losses.

A couple articles discussing this, there are many:

https://chrisgammell.com/can-dc-power-an-entire-home/
https://hackaday.com/2017/03/06/what-voltage-for-the-all-dc-house/

Huge power plants and a massive grid is really a step back in (whole) system design. Elon said it well, he rewards his engineers to remove parts not add them!

For the few cases where you need to move medium distances, solar field to launch pad to protect the solar panels is the ONLY one I can think of, wireless is viable.

If you start with solar, then switching from DC to AC, then transmit, then convert AC to DC for consumption is a waste of energy, cost and more components/raw materials.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/13/2019 08:55 pm
the numbers are crap even if you ignore the efficiency losses in recovering the energy. (I suspect the same is true of pressurised gas energy storage. Of course, not as dumb an idea as triboelectric generation, but still.)

We shouldn't mock numbers we don't know.  Adiabatic compressed air energy storage (ACAES) has > 70% round-trip efficiency.  And if you can implement ACAES in ice chambers (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1935540#msg1935540), you don't need to build storage vessels.

If.

Also, Baumgaertner (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1865539#msg1865539) and Seol (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1867784#msg1867784) know martian triboelectricity rather well.  You might think twice about calling them "dumb".

--

But re batteries: 

What alternate martian ISRU system might give batteries that serve better than perchlorate saltwater batteries, in a farm scenario (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2024040#msg2024040)?

(http://aquionenergy.com/wp-content/uploads/2016/02/stack_02.jpg)

Image:  Aquion's Aspen saltwater battery

Those Aquion battery modules (http://aquionenergy.com/technology/deep-cycle-battery/) have desirable qualities:  good sub-zero performance, long service life, non-corrosive chemistry, easy infrequent maintenance, no moving parts, etc.  And the ISRU loading process seems relatively straightforward, since it uses abundant electrolytes that require no manufacturing beyond evaporative salt harvest.

So these batteries would ship as empty shells, to be filled with water and perchlorate salts on-site.  What alternate battery system might be cheaper / lighter / simpler, in this scenario?

Looking at that site I couldn’t find any clear specs. One of the dimensions was 1.3m and some crazy high amp-hour rating. Would you have any info on wet and dry mass? Are there any charts showing max optimal discharge rate v temp?  Volts v discharge state, actual usable capacity would be good too.

They look interesting if the numbers are good.


Thanks

Phil
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/14/2019 03:22 am
I couldn’t find any clear specs.

Some Aquion battery details:  1 (https://www.modernoutpost.com/wp-content/uploads/2017/01/Aquion_Energy_M110-LS83_M110-L083_Product_Specification_Sheet.pdf) 2 (https://www.altestore.com/blog/2016/03/the-rise-of-aquion-batteries-clean-safe-energy-storage/#.Xe_j4dJOnb1) 3 (https://patents.google.com/patent/US8298701B2/en)

--

I assumed shipment of dry battery cases.  But going a step further, could you ship only circuit inserts?  That is, manufacture cases on Mars, and ship just the cathodes, anodes, cotton separators and current collector plates.  If you did that, your cargo mass might be < 1% of battery mass.

That improvement would require a solid ISRU system for production of cryogenic plastics, and I don't know if that should be assumed. 

Pros and cons: 

There's need for "indoor" polyethylene plastics.  They're easily manufactured, but also quickly destroyed by cold or UV.  Hence indoor use, only.  And because those plastics are used only indoors, need is limited; i.e., hab space is limited, severely. 

There's much greater need for "outdoor" plastics, where space and growth are essentially unlimited.  But these must be true cryogenic plastics, and stabilized, to withstand both cold and UV. 

Q:  Is there an ISRU method for production of cryogenic plastics?  These are specialty plastics, so manufacturing methods should be assumed proprietary, and ISRU production infeasible, by default.  A plausible ISRU method should list the essential manufacturing steps explicitly.


(https://www.ensingerplastics.com/-/media/ensinger/graphics/shapes/service-temperature-50.ashx?as=1&la=en&h=1074&w=423&iar=1&hash=FD0E924308602C92EA433195258D1E0013FF75F6)


Image:  Ensinger plastics (https://www.ensingerplastics.com/en/shapes/plastic-material-selection/low-temperature):  showcasing short-term and long-term service temperature ranges.

Martian ISRU plastics for saltwater battery cases should probably have a minimum long-term service range of -150 C to +100 C.

--

A further complicating factor:  oxidizing chemistry

Ultra High Molecular Weight Polyethylene (UHMW-PE (https://www.emcoplastics.com/uhmw-faqs/)) can handle cryogenic temperatures, but cannot withstand oxidizing solutions such as bleach (sodium hypochlorite).  So it's likely UHMW-PE can't withstand a saltwater battery's oxidizing perchlorate solution.

--

Alternate ISRU materials for battery cases?

--

Using Airloy X60 for battery cases

Airloy X60 (http://www.airloy.com/category/productlines/) is a structural material with good properties.  It withstands cryogenic temperatures, UV and oxidizing solutions, and it's an excellent thermal and electrical insulator.  Its porosity is extraordinarily fine, making it water-repellent, with a further moisture-proof option (http://www.aerogeltechnologies.com/airloy/about-airloy-ultramaterials/).  And with density as low as 0.2 g/cm3, a moisture-proof variant of X60 would seem attractive for use in ultra-lightweight, thermally self-insulating battery cases.

If battery cases were shipped as Airloy X60 cargo, the battery payload mass required to meet the notional 10x10 grid battery requirement  (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2024040#msg2024040)(10 MW for 10 hours), would drop below 100 t.

That's < 1 ton of battery cargo per MWh.  Has anyone sketched such an ultra-lightweight battery cargo previously?

(https://s3-prod.plasticsnews.com/s3fs-public/NEWS_181119930_AR_-1_LJLBRPBXUJXM.jpg)

(http://www.aerogeltechnologies.com/wp-content/uploads/2015/05/vlcsnap-2017-04-13-09h57m16s147-1024x576.png)
Title: Re: Re: Envisioning Amazing Martian Habitats
Post by: Twark_Main on 12/14/2019 07:06 am
I have used the "Report" feature to request that posts #2674 and later (excepting #2675 and #2677) be moved to Power Options. Not sure what else I can do...

Before this thread moves, I have to chime in again. One of the main reasons AC won over DC, was due to the power generation technology. they were building a very few extremely large power plants to sell to many cities. AC was more efficient for high volume long distance transmission. Earth is already switching to distributed power over very sort distances, and removing the DC-AC-DC gear and losses.

A couple articles discussing this, there are many:

https://chrisgammell.com/can-dc-power-an-entire-home/
https://hackaday.com/2017/03/06/what-voltage-for-the-all-dc-house/

Huge power plants and a massive grid is really a step back in (whole) system design. Elon said it well, he rewards his engineers to remove parts not add them!

Agreed.  We're moving to autonomous microgrids with solar and batteries, which can disconnect and reconnect from their neighbors as needed to maximize efficiency and reliability.

For the few cases where you need to move medium distances... wireless is viable.

The problem is the efficiency. For HVDC lines it's only a few percent, but wireless is far more.

"Viable" isn't just about comparing the mass of the wireless power hardware vs towers and wires and power electronics. It's about the mass (and installation/maintenance labor) of all the extra solar panels you need to compensate for the inefficiency of wireless transmission.

solar field to launch pad to protect the solar panels is the ONLY one I can think of

If you're beaming solar power from orbit to a receiving rectenna array on the ground (for reliable power in dust storms), you probably want to position that receiver array a few km from your city. So that's another one.

If you start with solar, then switching from DC to AC, then transmit, then convert AC to DC for consumption is a waste of energy, cost and more components/raw materials.

I agree whole-heartedly.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/14/2019 11:39 pm
Insulated 477 wire is 810 kg per km.  About 600 amps rated, probably more on Mars.  600 A x 400V = 240 000 kVA or about 240 kW of power.
So we could not connect up a very large solar farm at low voltage in DC.  100 km would be 810 tonnes, but we would want to increase the voltage.

Anyone know if HVDC ground return would work on Mars?  Would have thought the frozen soil conductivity was too poor.  So we might always need two wires?
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/15/2019 12:28 am
Insulated 477 wire is 810 kg per km.  About 600 amps rated, probably more on Mars.  600 A x 400V = 240 000 kVA or about 240 kW of power.
So we could not connect up a very large solar farm at low voltage in DC.  100 km would be 810 tonnes, but we would want to increase the voltage.

Anyone know if HVDC ground return would work on Mars?  Would have thought the frozen soil conductivity was too poor.  So we might always need two wires?

No one transmits power long-distance at battery voltage.  Step-up / step-down transformers are ubiquitous because efficient.  That's why UHVDC (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025020#msg2025020) exists, right?

And SWER (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025020#msg2025020) would work on Mars, yes.  Arctic SWER is already demonstrated (https://www.commonwealthnorth.org/download/past_study_groups/rural-alternative-energy-study-group/2011/HVDC%20Ph1%20Final%20Report.pdf).

Quote from: Denali Commission
(https://www.alaskapublic.org/wp-content/uploads/2019/04/DenaliCommissionSeal.jpg) (https://dcivweuyzxz66.cloudfront.net/about-universities/alaska-village-electric.jpg)

A 10-mile single-phase AC SWER line was constructed to connect the village of Shungnak to Kobuk in northwestern Alaska.  The line and the SWER system worked successfully...   Like the Bethel – Napakiak SWER line, this line also successfully demonstrated SWER viability in permafrost regions.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/15/2019 02:51 am
Insulated 477 wire is 810 kg per km.  About 600 amps rated, probably more on Mars.  600 A x 400V = 240 000 kVA or about 240 kW of power.
So we could not connect up a very large solar farm at low voltage in DC.  100 km would be 810 tonnes, but we would want to increase the voltage.

Anyone know if HVDC ground return would work on Mars?  Would have thought the frozen soil conductivity was too poor.  So we might always need two wires?

No one transmits power long-distance at battery voltage.  Step-up / step-down transformers are ubiquitous because efficient.  That's why UHVDC (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025020#msg2025020) exists, right?

And SWER (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025020#msg2025020) would work on Mars, yes.  Arctic SWER is already demonstrated (https://www.commonwealthnorth.org/download/past_study_groups/rural-alternative-energy-study-group/2011/HVDC%20Ph1%20Final%20Report.pdf).

Quote from: Denali Commission
(https://www.alaskapublic.org/wp-content/uploads/2019/04/DenaliCommissionSeal.jpg) (https://dcivweuyzxz66.cloudfront.net/about-universities/alaska-village-electric.jpg)

A 10-mile single-phase AC SWER line was constructed to connect the village of Shungnak to Kobuk in northwestern Alaska.  The line and the SWER system worked successfully...   Like the Bethel – Napakiak SWER line, this line also successfully demonstrated SWER viability in permafrost regions.
Really interesting paper, thanks!  But however, from Wikipedia SWER:
'Experience in Alaska shows that SWER needs to be grounded below permafrost, which is high-resistance.[6]'

I would expect Martian permafrost to extend down kilometers, making SWER difficult.  Of course, the reality may be different, there may be layers of salty water that would make excellent conductors.  But perhaps we should plan for two wire HVDC, and be happy if the reality is better.

Because a Martian settlement is so energy intensive, even fairly small ones will require higher voltages.  An artificially lit greenhouse operating at 500 W/m2 and 480V DC would hit 200 amps at about 200m2.  That's not a very large greenhouse.  And an fuel producing plant will also gobble up power in about the same proportions.  And you may not want ground return HVDC inside the colony perimeter.  So Medium voltage (MVDV) dual wire in the 5 000 to 50 000 Volt range may happen fairly quickly.  Nad we may need to include a grounding grid in a colony built on permafrost, although I guess the risk of getting a shock in a spacesuit should be low.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/15/2019 03:08 am
The question that might arise about using 120 DC is what about the more powerful types of electrical equipment, nominally ovens (ranges) and dryers.  I guess we might have vacuum dryers on Mars? Or would we lose too much nitrogen that way?

120V is usually limited to 1500W, so that's ok for microwave ovens and such but a bit weak for other uses.  In England at 230V they have really potent tea kettles!

So should we go for lower of higher voltages for local distribution?
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/15/2019 03:32 am
Quote from: Wik
"SWER needs to be grounded below permafrost, which is high-resistance."

You wouldn't stick grounding wires in a block of ice, on Mars or at home.

Mafic rock is common on Mars, with resistivity orders of magnitude lower than that of ice-rich patches.  You ground SWER in the rock.

(https://gpg.geosci.xyz/_images/resistivity_table1.png)

Image:  Conductivities and resistivities of common rocks (https://gpg.geosci.xyz/content/physical_properties/physical_properties_conductivity.html)
Title: Re: Power options for a Mars settlement
Post by: Barley on 12/15/2019 05:53 am

Alternate ISRU materials for battery cases?


Glass.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/15/2019 08:08 am

Alternate ISRU materials for battery cases?


Glass.

Borosilicate glass (e.g. Pyrex) has very low coefficient of thermal expansion, to withstand temperature swings.  But the ISRU boron, fluxes and stabilizers for production of that glass -- even possible?  If not possible, would you want to ship those materials for this particular purpose?

Is there an easier ISRU glass to hold warm batteries on a cryogenic night?
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 12/15/2019 09:34 am
Re: Thermal expansion.

AIUI, basalts are pretty low too. Better than common glass. Around the same as borosilicates, depending on the composition. Worse than pure silica.
Title: Re: Power options for a Mars settlement
Post by: magnemoe on 12/15/2019 10:14 pm
The question that might arise about using 120 DC is what about the more powerful types of electrical equipment, nominally ovens (ranges) and dryers.  I guess we might have vacuum dryers on Mars? Or would we lose too much nitrogen that way?

120V is usually limited to 1500W, so that's ok for microwave ovens and such but a bit weak for other uses.  In England at 230V they have really potent tea kettles!

So should we go for lower of higher voltages for local distribution?
Norway here and yes 2-3 KW heaters and similar is pretty common.
Our ovens tend to have their own cabling, yes we use electricity for them and can draw a lot if you both run the oven and multiple plates, steak in oven, then potatoes and other vegetables.
Farms and workshops tend to use plenty of 3 phase equipment still 230V for stuff like grain elevators and compressors, light industry and you have the 400 volt standard.
Heavy industry tend to want 10KV inn, if its energy intensive like an aluminium plant you probably talk 20-50 KV.

On the other hand, having 24 V for lighting with led lamps and various sensors and surround speakers makes sense too.
As its simple, safe and you can fix it yourself.
Not totally safe, still remember trying to add some amplifier to my car and got an short circuit who made the wire burn like an fuse. Battery was disconnected very brute force.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/16/2019 05:04 am
X60 in the grid

Cases:  Airloy X60 is an ultra-lightweight thermal insulator with good strength:  950 MPa (http://www.airloy.com/category/productlines/) compressive strength.  Thermal insulation and strength are needed in a martian saltwater battery case.  Neither glass nor stone offers both properties, so it seems neither is competitive for this application.

Cables:  X60 remains ductile (http://www.airloy.com/category/performance/) at cryogenic temperatures, and the moisture-proof option (http://www.aerogeltechnologies.com/airloy/about-airloy-ultramaterials/) may minimize electrical conductivity, so that X60 might conceivably serve as ultra-lightweight electrical insulator for power transmission cables.  Tbd.

Manufacture:  Martian CO2 can be applied in the supercritical drying process (https://www.sciencedirect.com/science/article/pii/S1877705813007583/pdf?md5=4fff766557d150a312154ac8272202df&isDTMRedir=Y&pid=1-s2.0-S1877705813007583-main.pdf&_valck=1) for aerogel production; hence, for X60 production.

Quote from: Aerogel Technologies, LLC
Airloy property notes: (http://www.airloy.com/category/properties/)

Water and Moisture Resistance

Airloys are generally hydrophobic (water-repelling) and are stable against moisture and humidity.  Airloys can also be prepared with enhanced hydrophobic character that enables them to remain unaffected even when submerged under water for long periods of time.

Machinability and Adherability

Airloys can be cut, drilled, turned, milled, and tapped just like other advanced engineering materials–steps that classic aerogels rarely survive.  For high-volume parts, airloys can be custom molded into specific three-dimensional shapes.  Airloys can also be glued and laminated to each other and to other materials such as carbon fiber reinforced plastics (CFRPs) and fiberglass (GFRPs). These features make airloys more than just technological wonders but actually practical for real-world engineering applications.

Electrical Conductivity and Surface Area

Airloys tailored for thermal and structural applications are electrically insulating with dielectric constants as low as 1.1 and typically boast surface areas of 200-800 m2 g-1 – orders of magnitude higher than conventional materials. Airloys can also be made electrically conducting with specific surface areas as high as 3000 m2 g-1.   This combination of conductivity and ultrahigh surface area in a mechanically robust form factor make conductive airloys uniquely valuable for advanced battery media, supercapacitor / ultracapacitor electrodes, desalination systems, fuel cells, and other electrochemical devices.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/17/2019 09:47 pm
Vanadium for X60

Vanadium (V) oxytripropoxide is the critical feedstock for X60.  If vanadium can be sourced locally, ISRU X60 manufacture becomes at least conceivable.  Given the potential value (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025609#msg2025609) of X60 to martian power systems, and to other outdoor structures, a cursory search for martian vanadium - and refinery methods - seems worthwhile.

Vanadium Ore

Chondritic meteorites provide vanadium, concentrated most especially in chromite at ~ 0.5 wt% [Mason & Fleischer 1979].  Accumulation of chromite in martian water channels and valleys was expected [Burns 1991], and it was in fact detected in Gale Crater in the Bagnold Dune Field [O'Connell‐Cooper et al. 2018].

Image (attached):  Namib Dune, Bagnold Dune Field, Gale Crater, Mars.  NASA/JPL-Caltech/MSSS.

So apparently martian dunes can contain appreciable vanadium ore.

A rotating dry magnet system can separate chromite granules from silicates at the dune site.  Ore granules would be transported to a refinery for extraction of chromium and vanadium metals.

Vanadium Refining

Some conceivable vanadium refinery steps, just for discussion:

1.  Produce sodium metavanadate (NaVO3) via sodium salt roasting process:  Mix ore granules with NaCl, plus chlorate and perchlorate oxidizers, and roast at 850 C.

2.  Leach out NaVO3 in water.

3.  Precipitate NaVO3 with sulfuric acid.

4.  Purify:  Dissolve NaVO3 in sodium carbonate solution, and add ammonium chloride to precipitate V2O5.

5.  Convert to gel:  Convert V2O5 to vanadium (V) oxytripropoxide gel via some version of hydrolysis and condensation [Fontenot et al. 2000], [Fears 2015].

6.  Expand the gel into X60 via CO2 supercritical drying.

Red Gold Refinery Extension

Vanadium processing and X60 production could be thought of as an extension of the notional "Red Gold (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1859890#msg1859890)" mining facility.  Most of the required machinery and chemistry would be present there already, including:

- semi-autonomous open-pit mining robotics
- magnetic separators
- water
- NaCl salt
- chlorate and perchlorate oxidizers
- sodium carbonate
- ammonium chloride

The sulfuric acid of step (3.) is not produced at the Red Gold refinery, but as it happens, refinery waste can give sulfuric acid via the contact process.  For example, react refinery waste H2S with CO2 over catalytic waste FeS or NiS at ~ 700 C to give SO2 [Alderman et al. 2019].  Then convert SO2 to sulfuric acid with oxidizers over, of all things, V2O5 catalyst (https://sinocata.com/portfolio-items/sulfuric-acid/).

Potential Application to Facility, Power, and Revenue Scaling

A Red Gold X60 extension could initiate mass-production of a variety of lightweight, insulated, durable outdoor structures.  Also, perchlorate solution from the Red Gold facility could serve as electrolyte in batteries.  Together these products would offer the prospect of a battery farm that may scale as needed.  The battery farm could target round-the-clock industrial power for round-the-clock Red Gold refinery operations.  This would roughly triple Red Gold production, and triple revenue, with a corresponding acceleration of martian ventures. 

Refs.

Alderman, N. P., Peneau, V., Viasus, C. J., Korobkov, I., Vidjayacoumar, B., Albahily, K., & Gambarotta, S. (2019). Syn-gas from waste: the reduction of CO2 with H2S. Reaction Chemistry & Engineering, 4(4), 763-771.

Burns, R. G. (1991). Evolution of ore deposits on terrestrial planets. In Resources of Near-Earth Space.

Fears, T. M. (2015). Synthesis and characterization of vanadium oxide nanomaterials.

Fontenot, C. J., Wiench, J. W., Pruski, M., & Schrader, G. L. (2000). Vanadia gel synthesis via peroxovanadate precursors. 1. In situ laser Raman and 51V NMR characterization of the gelation process. The Journal of Physical Chemistry B, 104(49), 11622-11631.

Mason, B. H., & Fleischer, M. (1979). Cosmochemistry: Meteorites. US Department of the Interior, Geological Survey.

O'Connell‐Cooper, C. D., Thompson, L. M., Spray, J. G., Berger, J. A., VanBommel, S. J., Gellert, R., ... & DeSouza, E. (2018). Chemical diversity of sands within the linear and barchan dunes of the Bagnold Dunes, Gale Crater, as revealed by APXS onboard Curiosity. Geophysical Research Letters, 45(18), 9460-9470.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/18/2019 02:50 am
Power for one person in a mature settlement.
The bus AMP values are for largish habitat/production modules, although 600 Amps may not be enough for a large greenhouse.

Solar powered, with methane powered genset for the bad days.  Fuel for the genset comes from propellant overproduction.  Batteries to get through the night.

Links up to a larger distribution network using MVDC, medium Voltage DC.  Joined a nice Siemens White paper on the subject.

I would expect most things to be on the 400 V DC bus.  In Canada we already have 347-600V heating and motors in most commercial buildings, with the power circuits isolated from the control circuits to reduce the risk of shock.  Consumer products on plugs would be on the 120V DC bus.  Lighting would be on the 24V bus, but greenhouse lighting would be on the 400V bus.
Title: Re: Power options for a Mars settlement
Post by: Barley on 12/19/2019 07:39 am

Alternate ISRU materials for battery cases?


Glass.

Borosilicate glass (e.g. Pyrex) has very low coefficient of thermal expansion, to withstand temperature swings.  But the ISRU boron, fluxes and stabilizers for production of that glass -- even possible?  If not possible, would you want to ship those materials for this particular purpose?

Is there an easier ISRU glass to hold warm batteries on a cryogenic night?
Since 1998 Pyrex(TM) has been made out of soda-lime glass, not borosilicate.  Purists argue that vintage Pyrex is better, but the new stuff works well enough.

In any case I believe the issue with glass is rapid temperature change, which results it large thermal gradients, differential expansion and cracked glass.  Fairly modest temperature regulation helps a lot.

Thermal insulation and strength are needed in a martian saltwater battery case.  Neither glass nor stone offers both properties, so it seems neither is competitive for this application.
The strength requirements for a battery case are rather modest.  Glass lead-acid batteries worked well.  There is no need for the same material to serve all functions.  Dry dirt in large quantities is a reasonable thermal insulator.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/19/2019 02:21 pm
Since 1998 Pyrex(TM) has been made out of soda-lime glass, not borosilicate.

::)

Quote from: Tom Kuntzleman (https://www.chemedx.org/blog/pyrex-any-other-name)
Did you know that Pyrex glassware used in chemistry labs is different than Pyrex glassware used in kitchens?  Pyrex glass used in chemistry experiments is made of borosilicate glass, whereas the Pyrex used when baking is made of soda lime glass.  What’s the difference?  Borosilicate glass is resistant to thermal shock, but soda lime glass is not.

https://www.youtube.com/watch?v=OPetc9bpu5s
Title: Re: Power options for a Mars settlement
Post by: Barley on 12/20/2019 12:29 am
Since 1998 Pyrex(TM) has been made out of soda-lime glass, not borosilicate.

::)

Quote from: Tom Kuntzleman (https://www.chemedx.org/blog/pyrex-any-other-name)
Did you know that Pyrex glassware used in chemistry labs is different than Pyrex glassware used in kitchens?  Pyrex glass used in chemistry experiments is made of borosilicate glass, whereas the Pyrex used when baking is made of soda lime glass.  What’s the difference?  Borosilicate glass is resistant to thermal shock, but soda lime glass is not.

https://www.youtube.com/watch?v=OPetc9bpu5s
Borosilicate glass is more resistant to thermal shock, but soda lime glass Pyrex(tm) casseroles routinely go from a 225C oven to a 20C room so it has some resistance to thermal shock.

As far as I can see there is nothing in batteries that requires instantaneous exposure to a liquid with a 100C temperature difference.  Avoiding doing something that serves no purpose would be well within the realm of modest thermal management.

ISRU is about using what you can get, not about saying there is some better material 300,000,000 km away so you can't possibly use what you can get. ::)
Title: Re: Power options for a Mars settlement
Post by: ZChris13 on 12/21/2019 03:35 pm
-big snip regarding thermal shock in glass batteries-
Sudden temperature changes are only one way to get thermal stress fractures. You could also have wildly different temperatures on either side of the glass causing breakage, for example in a battery on Mars. Begin opinions without numbers: they would need to be insulated from the ground, which is the only thing that should provide enough flux to cause a big differential. The atmosphere would be too thin for that, maybe.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/21/2019 04:09 pm
there is nothing in batteries that requires instantaneous exposure to a liquid with a 100C temperature difference.  Avoiding doing something that serves no purpose would be well within the realm of modest thermal management.

ISRU is about using what you can get, not about saying there is some better material 300,000,000 km away so you can't possibly use what you can get. ::)

You overlooked the 100C+ thermal gradient that's forced across the glass nightly when the battery discharges.  That's thermal shock.

And I certainly didn't say, "there is some better material 300,000,000 km away so you can't possibly use what you can get." 

And you got a basic fact wrong on Pyrex, but didn't admit it.   ::)

--

Absent insulation, thermal shock would be common.  But if insulation is strong, there's no need for the glass case anyway; the insulation becomes the case.  Hence a look at ISRU X60 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2026311#msg2026311).

If you wanted a strong ISRU specialty glass, you might look at the challenge of producing fused quartz from, say, opaline silica (https://www.hou.usra.edu/meetings/lpsc2017/pdf/2038.pdf).
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/22/2019 03:17 am
there is nothing in batteries that requires instantaneous exposure to a liquid with a 100C temperature difference.  Avoiding doing something that serves no purpose would be well within the realm of modest thermal management.

ISRU is about using what you can get, not about saying there is some better material 300,000,000 km away so you can't possibly use what you can get. ::)

You overlooked the 100C+ thermal gradient that's forced across the glass nightly when the battery discharges.  That's thermal shock.

100 K temperature cycle over 8 hours through a relatively thermally conductive solid? Not exactly "shock."

And I certainly didn't say, "there is some better material 300,000,000 km away so you can't possibly use what you can get."

I don't think anyone interpreted that as a direct quote, but rather as a reductio-ad-absurdum counterargument.

And you got a basic fact wrong on Pyrex, but didn't admit it.   ::)

What basic fact is that?

Afaict they corrected you with "Pyrex(tm) isn't always borosilicate anymore," and you corrected them with "Pyrex(tm) is still sometimes borosolicate." One-for-one, if you ask me. ;)

Absent insulation, thermal shock would be common.  But if insulation is strong, there's no need for the glass case anyway; the insulation becomes the case.

"Insulation" doesn't mean it works as a structural material.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/23/2019 03:41 pm
100 K temperature cycle over 8 hours through a relatively thermally conductive solid? Not exactly "shock."

Battery discharge forces a 100C+ thermal gradient across the glass, unavoidably, because inner and outer surfaces are in direct, conductive contact with a 100C+ difference.  That's thermal shock, all right. 

[He wrote] a reductio-ad-absurdum counterargument.

Straw-man, with your addition.

"Insulation" doesn't mean it works as a structural material.

X60 is structural by design, noted previously (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025609#msg2025609).   ::)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/23/2019 05:46 pm
100 K temperature cycle over 8 hours through a relatively thermally conductive solid? Not exactly "shock."

Battery discharge forces a 100C+ thermal gradient across the glass, unavoidably, because inner and outer surfaces are in direct, conductive contact with a 100C+ difference.  That's thermal shock, all right.

Sorry I missed it. I read the links you posted but I didn't see anything about that. Where are you seeing this?

Not sure what "straw-man" you mean.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/23/2019 10:22 pm
One of the uses for Power in a Mars habitat will be water production.  Here are a few numbers I have been working on to get a baseline for this operation.
Seems clear to me that a great use of the excess heat from the habitat will be melting water, but it's nice to add some numbers to the intuition.   Although written as though the numbers were authoritative, it's still mostly guess work  :-)

Water extraction
Water will be available from a number of sources on Mars. However, it is not yet clear if the water will contain contaminants, and what will be the nature of these.

Melting
Water will mostly be in a frozen state and will need to be heated to be melted. This required about 336 kJ per kg for the phase change from ice to water. Heating the water from Mars ambient temperature to the water treatment process temperature will also require about 4,18 kJ/kg x 70C = 292 kJ/kg for a total of 628 kJ/kg.

Crushing and milling
Water at freezing temperature has a hardness of about 1.5 Mohs[1]. This puts it between talc and gypsum, so relatively soft. However, ice gets harder as it gets colder. At -70C its hardness on the Mohs is about 6, or just below the hardness of quartz. So drilling through cold martian ice will be very close to drilling through granite, that has a hardness of 6 to 7.

Typical hard rock grinding mills operate at about 10 kWh per tonne. If the ice is still at -70C then crushing it might require up to 36 kJ/kg. This is significantly less than the power required to melt the ice, so it is likely ice will be crushed at the source to be made transportable, but melted at the settlement, ideally using waste heat.

Transportation
Transportation of water on Mars will probably mostly be done using heavy trucks. These use about 2,4 kJ/kg/km on Earth. For a water source 15 km away, the energy to move the ice will be similar to the energy to extract the ice, but still less than 5% of the energy required to melt the ice. Rail might reduce the energy significantly, and the lower martian gravity might help as well.

Recycled water will incur none of the above costs. So water treatment is interesting as an energy efficiency measure at the settlement.
https://marspedia.org/Water_Infrastructure
Title: Re: Power options for a Mars settlement
Post by: AC in NC on 12/24/2019 12:32 am
Crushing and milling
Water at freezing temperature has a hardness of about 1.5 Mohs[1]. This puts it between talc and gypsum, so relatively soft. However, ice gets harder as it gets colder. At -70C its hardness on the Mohs is about 6, or just below the hardness of quartz. So drilling through cold martian ice will be very close to drilling through granite, that has a hardness of 6 to 7.

Wouldn't there be a substantial friction bonus that would make the granite comparison less of a factor that that hardness might otherwise suggest?  Not sure how the "drilling dynamics" would work in that regard.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/24/2019 04:46 pm
Crushing and milling
Water at freezing temperature has a hardness of about 1.5 Mohs[1]. This puts it between talc and gypsum, so relatively soft. However, ice gets harder as it gets colder. At -70C its hardness on the Mohs is about 6, or just below the hardness of quartz. So drilling through cold martian ice will be very close to drilling through granite, that has a hardness of 6 to 7.

Wouldn't there be a substantial friction bonus that would make the granite comparison less of a factor that that hardness might otherwise suggest?  Not sure how the "drilling dynamics" would work in that regard.
We'd certainly save on water used for processing!  And on cooling water as well.  The energy used in mining comes from breaking the chemical bonds between the mineral's components.  I expect the on site mining would try to create the largest blocks possible, and thereby reduce the milling energy significantly.  There are some interesting gas based methods that might be used.   But no use in running the ice though a ball mill to turn it into sand, if it is going to be melted anyway.  So my 10-20 kWh/ton is probably high.
It might be difficult to extract solid ice with a backhoe or a shovel though.  Might make sense to use a locally produced explosive, something made from methane and oxygen, to blast the ice into usable fragments.  Or cut thin grooves and then break the ice using some kind of expansion device?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/24/2019 05:00 pm
Table extracted from the hard Rock Miner's handbook.

If the Ice is as hard as rock, then I expect the work required should be close to rock.

I guess this means that a vehicle using, for example, 4 x 100 kWh Tesla batteries (a Tesla semi based vehicle) might be able to produce 20-80 tonnes of water per day for shipping to a settlement.  That's enough water for quite a large installation. A Starship requires a bit less than 700 tonnes of water per year for propellant production, so 40 t/day x 300 days / 700 tonnes = 17 Starships fuelled.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/27/2019 12:10 pm
Crushing and milling
Water at freezing temperature has a hardness of about 1.5 Mohs[1]. This puts it between talc and gypsum, so relatively soft. However, ice gets harder as it gets colder. At -70C its hardness on the Mohs is about 6, or just below the hardness of quartz. So drilling through cold martian ice will be very close to drilling through granite, that has a hardness of 6 to 7.

Wouldn't there be a substantial friction bonus that would make the granite comparison less of a factor that that hardness might otherwise suggest?  Not sure how the "drilling dynamics" would work in that regard.
We'd certainly save on water used for processing!  And on cooling water as well.  The energy used in mining comes from breaking the chemical bonds between the mineral's components.  I expect the on site mining would try to create the largest blocks possible, and thereby reduce the milling energy significantly.  There are some interesting gas based methods that might be used.   But no use in running the ice though a ball mill to turn it into sand, if it is going to be melted anyway.  So my 10-20 kWh/ton is probably high.
It might be difficult to extract solid ice with a backhoe or a shovel though.  Might make sense to use a locally produced explosive, something made from methane and oxygen, to blast the ice into usable fragments.  Or cut thin grooves and then break the ice using some kind of expansion device?

I think what AC in NC was getting at is the heat produced by drilling for example, would raise the temp and soften the ice, hopefully making the drilling easier.

Combine the drilled holes (or ground in scoring) with a concussion, mechanical or explosive, to cleave off blocks. Memories of a 1 ft thick concrete/limestone wall in my basement, a big impact driver with a large bit, a sledge hammer and a lot of sweat. Without the holes I couldn’t have broken that wall by hand.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/27/2019 01:13 pm
Has anybody looked at solar thermal on mars? A target hit by mirrors, covered with PV and backed with cooling coils would have higher conversion efficiency than thermal or PV alone. The cooling coils keep the PV from going toasty. With the thermal happening in a concentrated space it’s easier to insulate from the cold ambient.

https://en.m.wikipedia.org/wiki/Photovoltaic_thermal_hybrid_solar_collector (https://en.m.wikipedia.org/wiki/Photovoltaic_thermal_hybrid_solar_collector)

This wouldn’t be for general application but for where raw heat is needed along with electrical power. I’m thinking props ISRU specifically and industrial processes in general.

Tracking absolutely needed so not a good fit for the first couple missions.

Side note: packing containers, pallets etc should be designed for breakdown and reuse as mirror/PV panel frames. Mirrors can be aluminized membrane. If the early missions end up with time on their hands (yeah, right) they can start building frames.

Phil
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 12/27/2019 05:17 pm
Has anybody looked at solar thermal on mars?

The problem with concentrators is the dust in the atmosphere. It affects solar concentrators long before it affects PV, so you can be below 10% solar thermal when the PV is still over 70%. It doesn't seem worth the effort of all the tracking systems and associated maintenance of moving parts.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/27/2019 06:04 pm
Has anybody looked at solar thermal on mars?

The problem with concentrators is the dust in the atmosphere. It affects solar concentrators long before it affects PV, so you can be below 10% solar thermal when the PV is still over 70%. It doesn't seem worth the effort of all the tracking systems and associated maintenance of moving parts.

Are there any figures on thermal input on mars over time? I didn’t realize it was this bad. That would definitely kill this idea.

OTOH if it’s not as bad as it appears the PITA of tracking hits breakeven at some (undefined) level. Terrestrial has smaller thermal excursions but faces wind and moisture in all its forms. Moisture is what really messes with outdoor machinery.

As a first hack on structure I’d use 25x25x1.5mm (1x1x1/16”) aluminum angle but it really depends on what’s available. I just weighed an 8’ length and it comes out to 458g. A 1x2m frame would mass 1.127kg but would weigh 428g on mars. So figure 600-700g with some reinforcing and reflective film. Doesn’t take much mechanism or power to move this.

If your figures are for worst case but it only happens once per synod for a couple of weeks it could still make sense. It’s all in the numbers.

Phil
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 12/27/2019 06:25 pm
Are there any figures on thermal input on mars over time? I didn’t realize it was this bad. That would definitely kill this idea.

Argh. Not in my bookmarks. IIRC the last time I posted it, it was in the Envisioning Amazing Mars Habitats thread. But I can't find it.

It was a paper based around the Viking lander results. It was a nice split of direct and indirect sunlight levels over the Martian year. Concentrated sunlight requires direct sunlight, but PV can handle indirect (indeed, to some extent, benefits from indirect light, effectively extending the daylight hours.)

But in summary, the approx. two years of the Martian year split into approx. 12 months of clear-skies, and 12 months of varying high dust levels, not including the monster storms once every five Martian years or so.

I suspect that many systems on Mars will have to be built around that one-on/one-off cycle. Refuelling, maintenance, growing seasons, etc.

(Pedantry: "Synod" means the synodic-period between a synchronisation of Earth and Mars' relative positions, not the Martian year itself. The synod is 780 Earth-days, the Martian year is 687 Earth-days (or 758 and 668 Martian sols respectively.))



Edit: Found it as soon as I posted, of course. {sigh} http://large.stanford.edu/courses/2017/ph240/black1/docs/nasa-tm-102299.pdf (http://large.stanford.edu/courses/2017/ph240/black1/docs/nasa-tm-102299.pdf).

The useful stuff is in the tables starting at page 18. Magic words are "beam", "diffuse", and "global" surface insolation, meaning direct sunlight, indirect sunlight, and total light (direct+indirect), respectively. The table on page 16, "at the top of the atmosphere" is the equivalent to the surface location at that time of year if there was no atmosphere. That's your comparison point to match the time-of-year. "Tau" is the measure of optical clarity.

Note how quickly "beam insolation" (direct sunlight) drops when the Tau goes above 0.5, and how it falls off a cliff when it's above 1. By contrast, global insolation (which includes indirect) doesn't really hurt until Tau>2 or 3. Now look at the graphs on pages 20/21, how much of the year is spent above Tau=1, and how much is spent below Tau=0.5.
Title: Re: Power options for a Mars settlement
Post by: Barley on 12/27/2019 06:46 pm

Crushing and milling
Water at freezing temperature has a hardness of about 1.5 Mohs[1]. This puts it between talc and gypsum, so relatively soft. However, ice gets harder as it gets colder. At -70C its hardness on the Mohs is about 6, or just below the hardness of quartz. So drilling through cold martian ice will be very close to drilling through granite, that has a hardness of 6 to 7.

Is hardness relevant here?  Glass is harder than steel, but I can reduce a block of glass to rubble much more easily than a block of steel.  What happens to -70C ice when you hit it with a hammer?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/27/2019 07:40 pm

Crushing and milling
Water at freezing temperature has a hardness of about 1.5 Mohs[1]. This puts it between talc and gypsum, so relatively soft. However, ice gets harder as it gets colder. At -70C its hardness on the Mohs is about 6, or just below the hardness of quartz. So drilling through cold martian ice will be very close to drilling through granite, that has a hardness of 6 to 7.

Is hardness relevant here?  Glass is harder than steel, but I can reduce a block of glass to rubble much more easily than a block of steel.  What happens to -70C ice when you hit it with a hammer?
Great question! 
https://www.researchgate.net/figure/Compressive-strength-and-density-of-ice-versus-a-variety-of-rock-types-data-from_fig3_272743517
There was some work done in the Greenland ice base, and the referenced paper puts the shear strength of ice at about five to ten times less the one of rock.  Seems to have to do with density more than anything.  I think it's clear that as ice gets colder it gets tougher.
So the actual work to break the ice would probably be an order of magnitude less than rock.  I think melting the ice makes even less sense, then.  Digging up the ice with a system similar to what is used fo coal might be the best technique to use?
Anyway, as far as power goes, digging up the ice will probably not be a large usage. 
Title: Re: Power options for a Mars settlement
Post by: Norm38 on 02/13/2020 02:19 pm
From the Zubrin discussion on The Space Show, it makes perfect sense for SpaceX to focus only on solar for the start of his Mars base.  There's no reason for SpaceX to mess around with nuclear power.
The US government has the DOE labs for that.  Let NASA take the lead on the nuclear reactor designs, roll them out when they're ready.

When there are football fields of solar panels on Mars, the market and motivation will be there to add nuclear to the mix.
Title: Re: Power options for a Mars settlement
Post by: Eka on 02/15/2020 07:43 am
From the Zubrin discussion on The Space Show, it makes perfect sense for SpaceX to focus only on solar for the start of his Mars base.  There's no reason for SpaceX to mess around with nuclear power.
The US government has the DOE labs for that.  Let NASA take the lead on the nuclear reactor designs, roll them out when they're ready.

When there are football fields of solar panels on Mars, the market and motivation will be there to add nuclear to the mix.
I think SpaceX needs to light a fire under DOE and NASA to get the issue solved, or it will hold back development on the Moon and Mars. This sort of thing drags out for decades, which I bet is why EM is going with solar.

I've seen some interesting designs, but will they work in the reduced gravity? Lower gravity means slowed convective cooling.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/15/2020 06:36 pm
From the Zubrin discussion on The Space Show, it makes perfect sense for SpaceX to focus only on solar for the start of his Mars base.  There's no reason for SpaceX to mess around with nuclear power.
The US government has the DOE labs for that.  Let NASA take the lead on the nuclear reactor designs, roll them out when they're ready.

When there are football fields of solar panels on Mars, the market and motivation will be there to add nuclear to the mix.
I think SpaceX needs to light a fire under DOE and NASA to get the issue solved, or it will hold back development on the Moon and Mars. This sort of thing drags out for decades, which I bet is why EM is going with solar.

So nuclear technology "drags out for decades," but it's solar that will "hold back development on the Moon and Mars?" That makes no sense.

If you had said "holds back development of the outer planets," then I would agree with you, but at Moon/Mars distances from the Sun solar is quite competitive with nuclear in mass/cost.

I've seen some interesting designs, but will they work in the reduced gravity? Lower gravity means slowed convective cooling.

Not sure which interesting designs you refer to, but Kilopower and its ilk use heat pipes, which are largely unaffected by changes in gravity. They rely on wicking, not convective transfer (ie a thermosiphon). Kilopower's radiators shed heat to their surroundings via (what else?) radiation, so convection isn't required there either.
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 02/15/2020 08:55 pm
From the Zubrin discussion on The Space Show, it makes perfect sense for SpaceX to focus only on solar for the start of his Mars base.  There's no reason for SpaceX to mess around with nuclear power.
The US government has the DOE labs for that.  Let NASA take the lead on the nuclear reactor designs, roll them out when they're ready.

When there are football fields of solar panels on Mars, the market and motivation will be there to add nuclear to the mix.
I think SpaceX needs to light a fire under DOE and NASA to get the issue solved, or it will hold back development on the Moon and Mars. This sort of thing drags out for decades, which I bet is why EM is going with solar.

So nuclear technology "drags out for decades," but it's solar that will "hold back development on the Moon and Mars?" That makes no sense.

If you had said "holds back development of the outer planets," then I would agree with you, but at Moon/Mars distances from the Sun solar is quite competitive with nuclear in mass/cost.

I've seen some interesting designs, but will they work in the reduced gravity? Lower gravity means slowed convective cooling.

Not sure which interesting designs you refer to, but Kilopower and its ilk use heat pipes, which are largely unaffected by changes in gravity. They rely on wicking, not convective transfer (ie a thermosiphon). Kilopower's radiators shed heat to their surroundings via (what else?) radiation, so convection isn't required there either.

Further to the discussion of the effectiveness (or not) of convective heat transfer for nuclear reactor cooling, its actually kind of a non-issue.  To the best of my knowledge, nuclear reactors do not rely on convection anyway (except, perhaps, in certain post-scram emergency cooling scenarios).  Core cooling is pretty much entirely advective if for no other reason than you'll be able to get a heck of a lot more coolant through the core (and thus extract more heat) by pumping the coolant instead of relying on thermally induced density gradients.  There may be some reason or other why micro-gravity would effect reactor operation, but this isn't one of them.
Title: Re: Power options for a Mars settlement
Post by: Eka on 02/16/2020 04:23 pm
From the Zubrin discussion on The Space Show, it makes perfect sense for SpaceX to focus only on solar for the start of his Mars base.  There's no reason for SpaceX to mess around with nuclear power.
The US government has the DOE labs for that.  Let NASA take the lead on the nuclear reactor designs, roll them out when they're ready.

When there are football fields of solar panels on Mars, the market and motivation will be there to add nuclear to the mix.
I think SpaceX needs to light a fire under DOE and NASA to get the issue solved, or it will hold back development on the Moon and Mars. This sort of thing drags out for decades, which I bet is why EM is going with solar.

So nuclear technology "drags out for decades," but it's solar that will "hold back development on the Moon and Mars?" That makes no sense.

If you had said "holds back development of the outer planets," then I would agree with you, but at Moon/Mars distances from the Sun solar is quite competitive with nuclear in mass/cost.

I've seen some interesting designs, but will they work in the reduced gravity? Lower gravity means slowed convective cooling.

Not sure which interesting designs you refer to, but Kilopower and its ilk use heat pipes, which are largely unaffected by changes in gravity. They rely on wicking, not convective transfer (ie a thermosiphon). Kilopower's radiators shed heat to their surroundings via (what else?) radiation, so convection isn't required there either.
I'm referring to the half mega watt plus mass producible reactor designs.


Further to the discussion of the effectiveness (or not) of convective heat transfer for nuclear reactor cooling, its actually kind of a non-issue.  To the best of my knowledge, nuclear reactors do not rely on convection anyway (except, perhaps, in certain post-scram emergency cooling scenarios).  Core cooling is pretty much entirely advective if for no other reason than you'll be able to get a heck of a lot more coolant through the core (and thus extract more heat) by pumping the coolant instead of relying on thermally induced density gradients.  There may be some reason or other why micro-gravity would effect reactor operation, but this isn't one of them.
Yes it is in those scram and shutdown modes that the cooling is convective. Otherwise forced when normally operating.

Due to the dust storms Mars colonies will need some baseline production from nuclear to get them through. I suppose they could make some emergency fuel cells that run on CH4/O2 and use up propellant.
Title: Re: Power options for a Mars settlement
Post by: Anjin_ on 02/16/2020 05:03 pm
There's also the option of using solar panels fastened onto a heavy duty kevlar fabric folded up like origami. There was a group at Princeton that put out a paper on a concept:

http://bigidea.nianet.org/wp-content/uploads/2018/03/2018-BIG-Idea-Final-Paper_Princeton-1.pdf

Quote
The Horus uses an expanding ring structure to unfold a solar membrane, exposing 1,061 m2 of solar panels to Martian sunlight and producing an average of 130 kW per year on the equator, with a maximum 155kW at perihelion and a minimum of 103 kW at aphelion. The solar panels rest on a foldable membrane that, including all structural elements, packs into a volume of 10 m^3; the entire payload weighs approximately 1,390 kg.

10m^3 in volume when stowed isn't too bad at all considering the amount of cargo volume in a Starship with no human life support inside.

So at 130kW per 1.4 tons, you could get up to 1MW with just 10.7 tons. (8 units would be 11.2 tons) Even if you double the mass, it is still a fraction of a Starship's payload capacity. You'd need 8 of these packets that each can expand to the 1061 m^2 size. Setting them up for an initial colony would probably go much much faster if you only need to deploy 8 units.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 02/18/2020 04:33 am
Probably have to increase that area of solar panels by about 20% since SpaceX is aiming for a flat, mid-latitude site. If there are sloping surfaces, such as large dunes or hills, that would help a bit although each array is a hexagon 42m across and is only suspended at its centre and at the corners.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 02/18/2020 08:33 am
There's also the option of using solar panels fastened onto a heavy duty kevlar fabric folded up like origami. There was a group at Princeton that put out a paper on a concept:

http://bigidea.nianet.org/wp-content/uploads/2018/03/2018-BIG-Idea-Final-Paper_Princeton-1.pdf

Quote
The Horus uses an expanding ring structure to unfold a solar membrane, exposing 1,061 m2 of solar panels to Martian sunlight and producing an average of 130 kW per year on the equator, with a maximum 155kW at perihelion and a minimum of 103 kW at aphelion. The solar panels rest on a foldable membrane that, including all structural elements, packs into a volume of 10 m^3; the entire payload weighs approximately 1,390 kg.
Sounds good but how close to production is it?
10m^3 in volume when stowed isn't too bad at all considering the amount of cargo volume in a Starship with no human life support inside.

So at 130kW per 1.4 tons, you could get up to 1MW with just 10.7 tons. (8 units would be 11.2 tons) Even if you double the mass, it is still a fraction of a Starship's payload capacity. You'd need 8 of these packets that each can expand to the 1061 m^2 size. Setting them up for an initial colony would probably go much much faster if you only need to deploy 8 units.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/18/2020 09:48 am
From the Zubrin discussion on The Space Show, it makes perfect sense for SpaceX to focus only on solar for the start of his Mars base.  There's no reason for SpaceX to mess around with nuclear power.
The US government has the DOE labs for that.  Let NASA take the lead on the nuclear reactor designs, roll them out when they're ready.

When there are football fields of solar panels on Mars, the market and motivation will be there to add nuclear to the mix.
I think SpaceX needs to light a fire under DOE and NASA to get the issue solved, or it will hold back development on the Moon and Mars. This sort of thing drags out for decades, which I bet is why EM is going with solar.

I've seen some interesting designs, but will they work in the reduced gravity? Lower gravity means slowed convective cooling.

I also listened to Dr. Zubrin's interview on The Space Show (https://www.thespaceshow.com/show/11-feb-2020/broadcast-3459-dr.-robert-zubrin). As always, he made many compelling arguments.
I don't always agree with everything he says, but he's changed my views about things on several occasions in the past.

In the case of using nuclear power on Mars, he said this would need to be driven by the government, not SpaceX.
In other parts of the interview, he seemed to have a very low opinion of NASA's current plans for human spaceflight.
He also said that it's quite possible SpaceX will land the first Starships on Mars before NASA lands people back on the Moon.

In addition, Zubrin said he personally spoke with Musk about nuclear, and Elon said they're only going to use solar.

So while I still think nuclear and solar would be a great combination, especially considering Starship can deliver 100+ tons to Mars,
it seems quite clear that this is not going to happen any time soon. The initial SpaceX Mars missions will use solar only.

So in my mind, the only real questions are:
 - How many kWh of batteries are they going to need?
 - For solar powered ISRU produced methane and LOX, will they also allow this to be used as an emergency backup power source?
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 02/18/2020 12:35 pm

So in my mind, the only real questions are:
 - How many kWh of batteries are they going to need?
 - For solar powered ISRU produced methane and LOX, will they also allow this to be used as an emergency backup power source?
It seems to be the KISS way. No system is the best system. No part is the best part.
You need solar for ISRU.
You need a lot of fuel for return.
It will provide the months long backup power with only the addition of a generator.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 02/18/2020 02:36 pm
For long term moon or Mars colonization, nuclear is going to have to be in the mix.  Near the moon's equator, you are going to have 14 days of dark, nuclear will be needed, or use minimum battery consumption and hold off on mining or other work, just survival mode.  For Mars 12+ hours of night is doable for battery use. 

In my opinion using a lot of cobalt and lithium for the batteries is going to tax those two minerals and eventually batteries will be expensive and limited.  There is a lot more uranium and thorium that can be used for much longer times going nuclear. 

Russia, several years ago designed a nuclear power plant that was less than 10 or 20 tons they could have launched into space for long term space use.  It can be done, and it can be done quickly like 4-5 years if someone would just do it.  The reactors can be launched without fuel rods which could be launched separately in shielding for the reactor to be fueled and started after being installed on the moon or Mars.  I suggest using small thorium reactors for higher safety.  Technology can also be used on earth.   
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 02/18/2020 03:49 pm

In my opinion using a lot of cobalt and lithium for the batteries is going to tax those two minerals and eventually batteries will be expensive and limited.  There is a lot more uranium and thorium that can be used for much longer times going nuclear. 
 

News today says tesla will be using batteries without any cobalt.
Lithium is everywhere and lots of it.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/18/2020 04:27 pm

In my opinion using a lot of cobalt and lithium for the batteries is going to tax those two minerals and eventually batteries will be expensive and limited.  There is a lot more uranium and thorium that can be used for much longer times going nuclear. 
 

News today says tesla will be using batteries without any cobalt.
Lithium is everywhere and lots of it.

Also the cobalt and lithium are all still present for recycling at the end of the battery's life, but the uranium and thorium are (slowly) destroyed in the process.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/18/2020 04:37 pm
For long term moon or Mars colonization, nuclear is going to have to be in the mix...

I guess it comes down to what people think this thread is about.

For me, a "Mars settlement" is the people who live/work there for the initial missions.
Eventually, this will grow into a "Mars colony" with many more people living there.

With this in mind, when it comes to nuclear power, my thoughts are:
Mars settlement: No
Mars colony: Yes
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/18/2020 06:06 pm
So in my mind, the only real questions are:
 - How many kWh of batteries are they going to need?
 - For solar powered ISRU produced methane and LOX, will they also allow this to be used as an emergency backup power source?
It seems to be the KISS way. No system is the best system. No part is the best part.
You need solar for ISRU. You need a lot of fuel for return. It will provide the months long backup power with only the addition of a generator.

Except you don't actually need "months" of backup for solar. If you have enough PV capacity to produce shiploads¹ of propellant within a synod, then you have enough to support minimal base ops when not producing propellant, even if the light levels are at 10% of average. So even during in those months long decadal global dust storms, you only need to worry about emergency levels of power during a few days². Outside of that, PV will still be sufficient during the day to keep the batteries topped up.

The best part is no part.



¹ Ship

² Yes, National Geographic, you will be able to keep seedlings from freezing. You cretins.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/18/2020 06:08 pm
For me, a "Mars settlement" is the people who live/work there for the initial missions.
Eventually, this will grow into a "Mars colony" with many more people living there.

Generally people are using "settlement" as a synonym for colony because colony has negative historical overtones.
Title: Re: Power options for a Mars settlement
Post by: Star-Drive on 02/18/2020 06:45 pm
For long term moon or Mars colonization, nuclear is going to have to be in the mix.  Near the moon's equator, you are going to have 14 days of dark, nuclear will be needed, or use minimum battery consumption and hold off on mining or other work, just survival mode.  For Mars 12+ hours of night is doable for battery use. 

In my opinion using a lot of cobalt and lithium for the batteries is going to tax those two minerals and eventually batteries will be expensive and limited.  There is a lot more uranium and thorium that can be used for much longer times going nuclear. 

Russia, several years ago designed a nuclear power plant that was less than 10 or 20 tons they could have launched into space for long term space use.  It can be done, and it can be done quickly like 4-5 years if someone would just do it.  The reactors can be launched without fuel rods which could be launched separately in shielding for the reactor to be fueled and started after being installed on the moon or Mars.  I suggest using small thorium reactors for higher safety.  Technology can also be used on earth.   

You folks might want to review the Los Alamos / NASA plans for the Kilo-power and Mega-power reactor programs.  See below URL and attached paper and slides on this topic. 

https://www.nextbigfuture.com/2018/01/kilopower-megapower-reactors-would-revolutionize-energy-safety-and-space-and-military-applications.html

With a family of space-qualified, fail-safe U-235 fission reactor systems with radiators in the 10.0 kWe to 2.0 MWe power range with the smallest weighing ~1,300 using highly enriched Uranium (HEU) fuel to 2,300kg using Low enriched uranium (LEU) fuel, and the largest 2 MWe reactor weighing in at ~35 mT, could easily be provided to Space-X by NASA at little to no cost to SpaceX, if SpaceX played their political cards wisely.

BTW, the reason the NASA Opportunity rover died on Mars during the dust storm that killed it's power generation capability was that the solar isolation at the Opportunity site was reduced to less than 1.0% of the normal sunlight reaching the Martian ground.  And that super low light condition lasted for months.  If I was a martian explorer and/or colonist, I would demand that there was a power backup available that did NOT require sun light from day one of the landing mission needed for survival. 
Title: Re: Power options for a Mars settlement
Post by: gideonlow on 02/18/2020 08:20 pm
BTW, the reason the NASA Opportunity rover died on Mars during the dust storm that killed it's power generation capability was that the solar isolation at the Opportunity site was reduced to less than 1.0% of the normal sunlight reaching the Martian ground.  And that super low light condition lasted for months.  If I was a martian explorer and/or colonist, I would demand that there was a power backup available that did NOT require sun light from day one of the landing mission needed for survival.

While Oppy did in-fact experience a huge reduction in power generation soon after the dust storm began, it was not all due to reduced solar insolation from atmospheric dust.  Much of the reduction is likely to have come from the solar panels being coated in dust directly.  A human presence would allow regular cleaning of a solar farm and very likely a significantly higher continued level of power.  Not to say such a storm doesn't need to be planned for, but survival might be less difficult than implied by the rover's demise.
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/18/2020 08:22 pm
The problem with Kilopower is right there in the name. We need megawatts not kilowatts. But it's a promising avenue and if it can be scaled up non linearly with mass, it's worthy of inclusion. As discussed upthread. It's only 30 pages, you mean you haven't read all of it??? LOL
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/18/2020 10:35 pm
the solar isolation at the Opportunity site was reduced to less than 1.0% of the normal sunlight reaching the Martian ground.  And that super low light condition lasted for months.

Incorrect. The lowest light conditions did not last for months, you can see that from Curiosity's daily Tau reports during the storm, instead there were individual 1% days scattered over several months of reduced 10-15% sunlight. Oppy couldn't start up on 10% of power and it took months before the skies cleared enough for Oppy to (in theory, it obviously didn't happen) generate enough power to wake up.

The 1% days are indeed the emergencies for a settlement. But they don't last for months. The 10% days do. However, because of ISRU, you will have more than 10 times the PV area you need to run your basic life-support systems. And if you reduce the lighting for the ag section, you have enough power even for the 1% days. (Plants don't instantly die just because the lights are reduced for a day or two. It just lowers your yield. Sucks, but doesn't mean death. And you plan for it. Just as you plan your routine growing vs maintenance cycles around the seasonal variations.)

Basic life-support will be a tiny part of the power requirements of a Martian settlement. Most of the demand is "industrial" and "agricultural".
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/18/2020 10:49 pm
While Oppy did in-fact experience a huge reduction in power generation soon after the dust storm began, it was not all due to reduced solar insolation from atmospheric dust.  Much of the reduction is likely to have come from the solar panels being coated in dust directly.

No. Before Oppy stopped transmitting, the Tau (optical clarity) levels still correlating pretty well with the PV production rates. It dropped to around 10% of the pre-storm rates for several days, draining the reserves. And Curiosity's daily reports showed that there were individually worse days. Oppy didn't have the reserves to survive prolonged 10% PV rates, it was living on batteries, the 1% days were the straw that broke the camel's back.

Judging by previous storms, there's only a build up of dust after the storm clears, as the dust settles out. But even that's not huge. The amount of dust in the air during a storm is surprisingly small, equivalent to micrometres per square-metre. These aren't like dust-storms on Earth that leave everything covered.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/18/2020 11:00 pm
the solar isolation at the Opportunity site was reduced to less than 1.0% of the normal sunlight reaching the Martian ground.  And that super low light condition lasted for months.

Incorrect. The lowest light conditions did not last for months, you can see that from Curiosity's daily Tau reports during the storm, instead there were individual 1% days scattered over several months of reduced 10-15% sunlight. Oppy couldn't start up on 10% of power and it took months before the skies cleared enough for Oppy to (in theory, it obviously didn't happen) generate enough power to wake up.

The 1% days are indeed the emergencies for a settlement. But they don't last for months. The 10% days do. However, because of ISRU, you will have more than 10 times the PV area you need to run your basic life-support systems. And if you reduce the lighting for the ag section, you have enough power even for the 1% days. (Plants don't instantly die just because the lights are reduced for a day or two. It just lowers your yield. Sucks, but doesn't mean death. And you plan for it. Just as you plan your routine growing vs maintenance cycles around the seasonal variations.)

Basic life-support will be a tiny part of the power requirements of a Martian settlement. Most of the demand is "industrial" and "agricultural".

And in a worst-case scenario, they could use some of the ISRU produced methane/LOX as an emergency backup power source.

In any case, Musk told Zubrin they're not going to use nuclear power. 
Title: Re: Power options for a Mars settlement
Post by: spacenut on 02/19/2020 02:11 am
Musk may not use nuclear power initially, but if Mars settlements are installed, NASA will want to be part of it.
This may mean NASA will provide the nuclear power in exchange for some research facilities at the Mars settlement.  To expand it only makes sense. 

Even in America's power system, there are multiple power sources.  Nuclear about 20%, natural gas about 37% now.  Coal < 30% and dropping.  About 10% from hydro and another 10% from wind/solar sources.  Natural gas (methane on Mars) is growing while coal is decreasing.  This has resulted in America cutting CO2 production faster than any country in the world percentage wise.  Also American vehicles are using less fuel as more hybrids and electrics come into play. 

Mars too will need multiple power sources.  If something happens to one, there should always be a backup.  All agree solar initially with methane as backup and later nuclear.  Wind might be a source at some future time where canyons or such areas have higher wind conditions on Mars.  There will be no water power, coal, or fuel oil, unless it is somehow discovered on Mars, but that would mean some type of carbon based life form that once lived on Mars as well as ancient oceans. 
Title: Re: Power options for a Mars settlement
Post by: 50_Caliber on 02/19/2020 02:16 am
the solar isolation at the Opportunity site was reduced to less than 1.0% of the normal sunlight reaching the Martian ground.  And that super low light condition lasted for months.

Incorrect. The lowest light conditions did not last for months, you can see that from Curiosity's daily Tau reports during the storm, instead there were individual 1% days scattered over several months of reduced 10-15% sunlight. Oppy couldn't start up on 10% of power and it took months before the skies cleared enough for Oppy to (in theory, it obviously didn't happen) generate enough power to wake up.

The 1% days are indeed the emergencies for a settlement. But they don't last for months. The 10% days do. However, because of ISRU, you will have more than 10 times the PV area you need to run your basic life-support systems. And if you reduce the lighting for the ag section, you have enough power even for the 1% days. (Plants don't instantly die just because the lights are reduced for a day or two. It just lowers your yield. Sucks, but doesn't mean death. And you plan for it. Just as you plan your routine growing vs maintenance cycles around the seasonal variations.)

Basic life-support will be a tiny part of the power requirements of a Martian settlement. Most of the demand is "industrial" and "agricultural".

And in a worst-case scenario, they could use some of the ISRU produced methane/LOX as an emergency backup power source.

In any case, Musk told Zubrin they're not going to use nuclear power.

Is Musk so dead-set against nuclear that SPS might be on the table?
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 02/19/2020 09:15 am
the solar isolation at the Opportunity site was reduced to less than 1.0% of the normal sunlight reaching the Martian ground.  And that super low light condition lasted for months.

Incorrect. The lowest light conditions did not last for months, you can see that from Curiosity's daily Tau reports during the storm, instead there were individual 1% days scattered over several months of reduced 10-15% sunlight. Oppy couldn't start up on 10% of power and it took months before the skies cleared enough for Oppy to (in theory, it obviously didn't happen) generate enough power to wake up.

The 1% days are indeed the emergencies for a settlement. But they don't last for months. The 10% days do. However, because of ISRU, you will have more than 10 times the PV area you need to run your basic life-support systems. And if you reduce the lighting for the ag section, you have enough power even for the 1% days. (Plants don't instantly die just because the lights are reduced for a day or two. It just lowers your yield. Sucks, but doesn't mean death. And you plan for it. Just as you plan your routine growing vs maintenance cycles around the seasonal variations.)

Basic life-support will be a tiny part of the power requirements of a Martian settlement. Most of the demand is "industrial" and "agricultural".

And in a worst-case scenario, they could use some of the ISRU produced methane/LOX as an emergency backup power source.

In any case, Musk told Zubrin they're not going to use nuclear power.

Is Musk so dead-set against nuclear that SPS might be on the table?
Mars isn't exactly short on sun facing slopes.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/19/2020 10:19 am
Musk may not use nuclear power initially, but if Mars settlements are installed, NASA will want to be part of it.
Yes, but NASA tends to move slowly. The only exception was during the Cold War.

Even in America's power system, there are multiple power sources.  Nuclear about 20%, natural gas about 37% now.  Coal < 30% and dropping.  About 10% from hydro and another 10% from wind/solar sources...
Note that solar panels currently only account for 1.4% of our total electricity (link here (https://www.eia.gov/tools/faqs/faq.php?id=427&t=3)).

Natural gas... is growing while coal is decreasing.  This has resulted in America cutting CO2 production faster than any country in the world percentage wise...
That depends on what time frame your're looking at. In the 80's and 90's, France ramped up nuclear power in a big way.
Today, France is around 70% nuclear (link here (https://en.wikipedia.org/wiki/Nuclear_power_in_France)). Meanwhile, Germany has shunned nuclear and concentrated on renewables.
The result is that today, per-capita CO2 emissions in Germany are about twice what they are in France.
This is one of the reasons I've changed my mind and become pro-nuclear.

But for a Mars settlement, Musk has made it pretty clear. They're only using solar panels. They're not using nuclear.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/19/2020 11:14 am
Is Musk so dead-set against nuclear that SPS might be on the table?

Doubtful.  Musk has been consistently against space-based solar power. Here's a quote (link here (http://shitelonsays.com/transcript/elon-musk-panel-bta-2012-2013-01-28)):
Quote from: Elon Musk
What do you get from being in orbit? You get twice as much sun - best case - but you've got to do a conversion... you've got to turn those electrons into photons and turn those photons back into electrons on the ground, and that double conversion is going to get you back to where you started, basically...

Also remember that with Tesla, Musk is selling the concept that solar panels and batteries are the answer.
He's even talked about power plants that cover thousands of square miles with solar panels (link here (https://www.popularmechanics.com/science/green-tech/a30188222/elon-musk-solar-farm/)).

To be clear, I think rooftop solar panels are great, but for powering industry and dense urban areas, there are better solutions.
For example, solar-thermal power plants store excess energy as heat in the form of molten salt. Way cheaper than batteries.
I also think solar and nuclear are complementary. Nuclear supplies baseline power at night, solar provides power during the day.

But since Musk only sells solar panels and batteries, he has a vested interest in playing down other competing solutions.
And given that the first Mars settlement will attract huge amounts of media attention, if Musk can do it with just solar panels and batteries, that will be a ton of free advertising for Tesla.
Title: Re: Power options for a Mars settlement
Post by: 50_Caliber on 02/19/2020 01:47 pm
Is Musk so dead-set against nuclear that SPS might be on the table?

Doubtful.  Musk has been consistently against space-based solar power. Here's a quote (link here (http://shitelonsays.com/transcript/elon-musk-panel-bta-2012-2013-01-28)):
Quote from: Elon Musk
What do you get from being in orbit? You get twice as much sun - best case - but you've got to do a conversion... you've got to turn those electrons into photons and turn those photons back into electrons on the ground, and that double conversion is going to get you back to where you started, basically...

Also remember that with Tesla, Musk is selling the concept that solar panels and batteries are the answer.
He's even talked about power plants that cover thousands of square miles with solar panels (link here (https://www.popularmechanics.com/science/green-tech/a30188222/elon-musk-solar-farm/)).

To be clear, I think rooftop solar panels are great, but for powering industry and dense urban areas, there are better solutions.
For example, solar-thermal power plants store excess energy as heat in the form of molten salt. Way cheaper than batteries.
I also think solar and nuclear are complementary. Nuclear supplies baseline power at night, solar provides power during the day.

But since Musk only sells solar panels and batteries, he has a vested interest in playing down other competing solutions.
And given that the first Mars settlement will attract huge amounts of media attention, if Musk can do it with just solar panels and batteries, that will be a ton of free advertising for Tesla.

I wonder if he might change his mind once one of the early proto-colonies has a planet-wide dust storm  that lasts for weeks or months.
Title: Re: Power options for a Mars settlement
Post by: M.E.T. on 02/19/2020 02:00 pm
Is Musk so dead-set against nuclear that SPS might be on the table?

Doubtful.  Musk has been consistently against space-based solar power. Here's a quote (link here (http://shitelonsays.com/transcript/elon-musk-panel-bta-2012-2013-01-28)):
Quote from: Elon Musk
What do you get from being in orbit? You get twice as much sun - best case - but you've got to do a conversion... you've got to turn those electrons into photons and turn those photons back into electrons on the ground, and that double conversion is going to get you back to where you started, basically...

Also remember that with Tesla, Musk is selling the concept that solar panels and batteries are the answer.
He's even talked about power plants that cover thousands of square miles with solar panels (link here (https://www.popularmechanics.com/science/green-tech/a30188222/elon-musk-solar-farm/)).

To be clear, I think rooftop solar panels are great, but for powering industry and dense urban areas, there are better solutions.
For example, solar-thermal power plants store excess energy as heat in the form of molten salt. Way cheaper than batteries.
I also think solar and nuclear are complementary. Nuclear supplies baseline power at night, solar provides power during the day.

But since Musk only sells solar panels and batteries, he has a vested interest in playing down other competing solutions.
And given that the first Mars settlement will attract huge amounts of media attention, if Musk can do it with just solar panels and batteries, that will be a ton of free advertising for Tesla.

Really don’t think that’s his motivation. There are a bunch of hurdles to clear to get a nuclear reactor to Mars, compared to solar panels and batteries. Using both in the long term might well happen.
Title: Re: Power options for a Mars settlement
Post by: Star-Drive on 02/19/2020 02:10 pm
The problem with Kilopower is right there in the name. We need megawatts not kilowatts. But it's a promising avenue and if it can be scaled up non linearly with mass, it's worthy of inclusion. As discussed upthread. It's only 30 pages, you mean you haven't read all of it??? LOL

Lar:  I'll be glad to read up thread in this sub-forum when time permits, but I would appreciate it if people would in return download and read the URL and Kilo-power report I posted upthread which showed that this Los Alamos nuclear reactor approach is easily scalable from 1.0 kW up to 2.0 MWe dependent on the need.  If Musk doesn't want to use it, that's his privilege, but its his and his proposed Mars colony's loss.

 nets2019-KilopowerMass-Poston.pdf (980.71 kB - downloaded 0 times.)

Best,
Title: Re: Power options for a Mars settlement
Post by: Star-Drive on 02/19/2020 02:13 pm
the solar isolation at the Opportunity site was reduced to less than 1.0% of the normal sunlight reaching the Martian ground.  And that super low light condition lasted for months.

Incorrect. The lowest light conditions did not last for months, you can see that from Curiosity's daily Tau reports during the storm, instead there were individual 1% days scattered over several months of reduced 10-15% sunlight. Oppy couldn't start up on 10% of power and it took months before the skies cleared enough for Oppy to (in theory, it obviously didn't happen) generate enough power to wake up.

The 1% days are indeed the emergencies for a settlement. But they don't last for months. The 10% days do. However, because of ISRU, you will have more than 10 times the PV area you need to run your basic life-support systems. And if you reduce the lighting for the ag section, you have enough power even for the 1% days. (Plants don't instantly die just because the lights are reduced for a day or two. It just lowers your yield. Sucks, but doesn't mean death. And you plan for it. Just as you plan your routine growing vs maintenance cycles around the seasonal variations.)

Basic life-support will be a tiny part of the power requirements of a Martian settlement. Most of the demand is "industrial" and "agricultural".

Paul451:  Thanks much for the correction and clarifications.

Best, Paul M.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 02/19/2020 02:21 pm
Musk is not dead set against nuclear.  He said there was too much red tape, and waiting like 10 years to get something approved.  Same with the Mars rocket.  He has studied and thought about nuclear ion propulsion, SEP propulsion, etc, etc.  He said liquid fuel is cheap, and refueling is cheaper than many of the alternatives. 

I think he is pragmatic enough to realize nuclear power is the only realistic long term solution to Mars power sources, especially if large scale industry is going to be built.  He is banking on NASA bringing that into the solutions.  He is just trying to kick start space exploration and colonization that has been stagnant since the early 1970's using existing technology to its maximum efficiency.  Like rockets and solar power.  Less red tape. 

Even to power America, it can't be done with solar alone.  Nuclear, natural gas engines, both take up far less space and produce more power than thousands of square miles of solar panels that only work in the daytime, or wind turbines that only work when the wind blows 20mph or greater consistently. 

The fear of nuclear power is unfounded based on new technologies.  The use of breeder reactors to use spent fuel rods and thorium reactors would greatly reduce nuclear waste as well as be safer to operate.  Small scale reactors can easily be brought to Mars with Starships to back up solar, and to crank up manufacturing on Mars to make Mars more self sufficient. 

Large scale use of greenhouses using grow lights will take a lot of power.  Smelting of metals will take a huge amount of power.  Not counting chemicals that will need to be produced, as well as return rocket fuel, for trips to and from Mars.  A dust storm coming up could play havoc on something you are right in the middle of doing if power is down. 

I know of a fiberglass factory near me.  They have to keep the equipment hot 24-7 or if the equipment shuts down, they have to physically go into the machines and chip out the cold glass and restart the machines.  This can take hours or days.  Industrial production will need continuous uninterrupted power supply. 
Title: Re: Power options for a Mars settlement
Post by: Star-Drive on 02/19/2020 02:45 pm
Musk is not dead set against nuclear.  He said there was too much red tape, and waiting like 10 years to get something approved.  Same with the Mars rocket.  He has studied and thought about nuclear ion propulsion, SEP propulsion, etc, etc.  He said liquid fuel is cheap, and refueling is cheaper than many of the alternatives. 

I think he is pragmatic enough to realize nuclear power is the only realistic long term solution to Mars power sources, especially if large scale industry is going to be built.  He is banking on NASA bringing that into the solutions.  He is just trying to kick start space exploration and colonization that has been stagnant since the early 1970's using existing technology to its maximum efficiency.  Like rockets and solar power.  Less red tape. 

Even to power America, it can't be done with solar alone.  Nuclear, natural gas engines, both take up far less space and produce more power than thousands of square miles of solar panels that only work in the daytime, or wind turbines that only work when the wind blows 20mph or greater consistently. 

The fear of nuclear power is unfounded based on new technologies.  The use of breeder reactors to use spent fuel rods and thorium reactors would greatly reduce nuclear waste as well as be safer to operate.  Small scale reactors can easily be brought to Mars with Starships to back up solar, and to crank up manufacturing on Mars to make Mars more self sufficient. 

Spacenut: 

"Musk is not dead set against nuclear.  He said there was too much red tape, and waiting like 10 years to get something approved."

Believe it or not, NASA management is painfully aware of this DOE regulations driven fact, and in response NASA collaborated with Los Alamos Labs to come up with a pre-approved and developed reactor design that can be effectively viewed as an off-the-shelf, scalable reactor technology with much less regulatory red-tape attached to its procurement by commercial vendors like SpaceX.  That is why they had Los Alamos come up with two (2) reactor designs with one of them using powerplant grade, (low (~20%) enriched uranium or LEU), that requires much less regulatory oversite than bomb grade, ~93% highly enriched uranium (HEU), even though the LEU reactor weighs twice as much as the HEU version.  Sometimes it's best to trade system mass for system availability and lower cost...

Best, Paul M.
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/19/2020 02:58 pm
The problem with Kilopower is right there in the name. We need megawatts not kilowatts. But it's a promising avenue and if it can be scaled up non linearly with mass, it's worthy of inclusion. As discussed upthread. It's only 30 pages, you mean you haven't read all of it??? LOL

Lar:  I'll be glad to read up thread in this sub-forum when time permits, but I would appreciate it if people would in return download and read the URL and Kilo-power report I posted upthread which showed that this Los Alamos nuclear reactor approach is easily scalable from 1.0 kW up to 2.0 MWe dependent on the need.  If Musk doesn't want to use it, that's his privilege, but its his and his proposed Mars colony's loss.

 nets2019-KilopowerMass-Poston.pdf (980.71 kB - downloaded 0 times.)

Best,
Interesting paper and not too long, with plenty of pictures. So an easy read. But they only scale from 1kw to 10kw.  What will the mass of a 1 megawatt plant be? The paper doesn't say. If it's a linear scaling, it's a non starter.   I wish they had done several sizes instead of just two so we could get some idea of what the scaling  curve looks like.

Also, there is a lot of armwaving about changes needed to get over 50kw... changes from stirling to brayton, changes in how the fuel has to be cast, and other things.

Net net, interesting paper, doesn't answer my question.
Title: Re: Power options for a Mars settlement
Post by: Star-Drive on 02/19/2020 03:13 pm
The problem with Kilopower is right there in the name. We need megawatts not kilowatts. But it's a promising avenue and if it can be scaled up non linearly with mass, it's worthy of inclusion. As discussed upthread. It's only 30 pages, you mean you haven't read all of it??? LOL

Lar:  I'll be glad to read up thread in this sub-forum when time permits, but I would appreciate it if people would in return download and read the URL and Kilo-power report I posted upthread which showed that this Los Alamos nuclear reactor approach is easily scalable from 1.0 kW up to 2.0 MWe dependent on the need.  If Musk doesn't want to use it, that's his privilege, but its his and his proposed Mars colony's loss.

 nets2019-KilopowerMass-Poston.pdf (980.71 kB - downloaded 0 times.)

Best,
Interesting paper and not too long, with plenty of pictures. So an easy read. But they only scale from 1kw to 10kw.  What will the mass of a 1 megawatt plant be? The paper doesn't say. If it's a linear scaling, it's a non starter.   I wish they had done several sizes instead of just two so we could get some idea of what the scaling  curve looks like.

Net net, interesting paper, doesn't answer my question.

Lar:  If you take the time to read the NextBigFuture article URL I also pointed to in my first post in this tread, you are correct that the Kilo-Power reactor family is currently only sized up to 10kWe, which is what NASA wanted for their immediate needs, but it is easily expandable up to 100 kWe as well.  There is also a similar Mega-Power (MWe) reactor series in the works that will fill in the power production gap of the Kilo-Power reactor series from 100 kWe up to 2.0 MWe dependent on customer demand.

https://www.nextbigfuture.com/2018/01/kilopower-megapower-reactors-would-revolutionize-energy-safety-and-space-and-military-applications.html

PS: Find attached a slide with the LANL 2 MWe reactor proposal that weighs in around 35mT.  Needless to say that this 2.0 MWe concept reactor is not anywhere close to a space-qualified, off-the-shelf system like the Kilo-Power units are, but it first requires a viable market for same to be identified.

Best,
Title: Re: Power options for a Mars settlement
Post by: oiorionsbelt on 02/19/2020 06:06 pm
SpaceX were trying and having difficulty, getting nuclear material for their own nuclear program.
Title: Re: Power options for a Mars settlement
Post by: Eka on 02/19/2020 06:40 pm
(Plants don't instantly die just because the lights are reduced for a day or two. It just lowers your yield. Sucks, but doesn't mean death. And you plan for it. Just as you plan your routine growing vs maintenance cycles around the seasonal variations.)
Um, no. If it happens at the wrong times of the growth cycle, the plants will fail to produce food period. The solution to this is staggered plantings so only a portion of the crop is in any one stage at the same time. The portion that gets hit by lack of light at a critical time can be aborted and replanted.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 02/20/2020 12:06 am
Staggered plantings in greenhouses would also mean fresh food on a continuous bases.  If yield is greater than consumption each time, the food could be canned or frozen for future use and in case there is a greenhouse problem.  Having greater production than consumption is a good thing long term.  In either case a lot of power is needed not only for plant growth, but for canning or freezing.  Freezing may only need an above ground unit that isn't heated, because Mars is cold already.  So that wouldn't require a lot of power, except during the blanching process. 
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/20/2020 01:48 am
Staggered plantings in greenhouses would also mean fresh food on a continuous bases.  If yield is greater than consumption each time, the food could be canned or frozen for future use and in case there is a greenhouse problem.  Having greater production than consumption is a good thing long term.  In either case a lot of power is needed not only for plant growth, but for canning or freezing.  Freezing may only need an above ground unit that isn't heated, because Mars is cold already.  So that wouldn't require a lot of power, except during the blanching process.

I'm assuming the initial missions will bring enough dry food to last a couple of years.
I'm also thinking greenhouse yield will normally be greater than consumption, which will only increase the food stores.

With this in mind, by using just solar panels and a reasonable amount of battery storage,
if there was a dust storm that lasted for months, food shouldn't be an issue.

In 10-20 years, as the settlement grows into something larger, they'll want to start manufacturing stuff on Mars in earnest.
When that happens, I think nuclear power will start becoming a lot more attractive.
But until then, I suspect solar panels and batteries will work fine, assuming they use ISRU methane/LOX as an emergency backup.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 02/20/2020 03:21 am
Well, when the headlines say "power options" then we have to discuss nuclear.  We all know SpaceX is going to use solar to start with and it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use. 

Going beyond solar, the immediate viable option for emergencies only would be methane generators using some of the methane for return rocket fuel until the problems are taken care of. 

Then beyond that nuclear is the only available option.  Unless it is discovered, there is no coal or oil on Mars, so that would mean nuclear after solar. 

I would prefer NASA to use the SLS wasted money on small scale nuclear power plants to be used on the moon or Mars at this point, especially after SpaceX gets Starship flying.  Then just pay SpaceX for moon or Mars launches, equipment, habitats etc.  By 2030 I think nuclear power for Mars will have to be taken seriously. 
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/20/2020 04:03 am
There's a thread for discussing scaling agriculture on Mars (https://forum.nasaspaceflight.com/index.php?topic=35877.0).
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/20/2020 04:30 am
(Plants don't instantly die just because the lights are reduced for a day or two. It just lowers your yield.
Um, no. If it happens at the wrong times of the growth cycle, the plants will fail to produce food period.

No. The equivalent of a couple of overcast days doesn't prevent crops from growing or fruiting. (As I said, you aren't facing months of zero power, even in the worst storms. That's not how it works.) The reason you do staggered production is so that: a) you get a continuous rather than seasonal supply of food; and b) the use of resources and consumption/production of gases is more constant.

Similarly with industrial facilities, dust storms don't just happen without warning. There's a long build up. You have several weeks to prepare. Long enough to properly shut down equipment. You use the time to do maintenance.

This has been discussed in the Scaling Ag and Amazing Habitats threads: Mars has annual variation in atmospheric clarity, essentially 12-14 months of clear skies (Tau <1) and 8-10 months of crappy skies (Tau >2). So you'd time your production and agricultural cycles around this, one (Earth) year of high productivity, one (Earth) year of middling productivity during which you'd schedule your maintenance, sterilisation and upgrades. During the decadal storms, you'd pull everything off-line and do the once-a-decade major overhauls while everyone is free from their regular jobs. Nothing to panic over.
Title: Re: Power options for a Mars settlement
Post by: hoardsbane on 02/20/2020 06:28 am
Well, when the headlines say "power options" then we have to discuss nuclear.  We all know SpaceX is going to use solar to start with and it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use. 

Do we need (bulk storage) batteries? 

Could you just oversize methane/hydrogen and oxygen production and storage (only slight impact on the associated solar farm due the efficiency differences?) and use fuel cells or internal combustion engines (waste heat being useful) and the surplus fuel/O2 for times when there is insufficient insolation (night and storms)?

Some batteries are obviously beneficial (e.g. reliability, system restarts), but the mass budget for incremental fuel/oxidiser production, storage and generation may be less than for the equivalent battery storage.



Thoughts?
Title: Re: Power options for a Mars settlement
Post by: Yaotzin on 02/20/2020 07:16 am
Well, when the headlines say "power options" then we have to discuss nuclear.  We all know SpaceX is going to use solar to start with and it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use. 
It's unlikely that batteries to power the electrolyzer will be more efficient than oversizing it, so along with the generally higher power demand during the day while people are awake/working, it is likely that only a tiny portion of generation would be stored for night.
Quote
Then beyond that nuclear is the only available option.  Unless it is discovered, there is no coal or oil on Mars, so that would mean nuclear after solar. 
There's no free oxygen on Mars, so coal/oil wouldn't be a power source even if discovered.
Quote from: hoardsbane
Do we need (bulk storage) batteries?

Could you just oversize methane/hydrogen and oxygen production and storage (only slight impact on the associated solar farm due the efficiency differences?) and use fuel cells or internal combustion engines (waste heat being useful) and the surplus fuel/O2 for times when there is insufficient insolation (night and storms)?

Some batteries are obviously beneficial (e.g. reliability, system restarts), but the mass budget for incremental fuel/oxidiser production, storage and generation may be less than for the equivalent battery storage.



Thoughts?
Electricity->methane->electricity is apparently ~30-38% efficient (43-54% if you can use the heat too), so something like double to triple the solar plus small increases in electrolyzer etc, vs 10-25% more solar for batteries plus rather heavy batteries. Might well be lighter.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 02/20/2020 07:28 am
Is Musk so dead-set against nuclear that SPS might be on the table?

Doubtful.  Musk has been consistently against space-based solar power. Here's a quote (link here (http://shitelonsays.com/transcript/elon-musk-panel-bta-2012-2013-01-28)):
Quote from: Elon Musk
What do you get from being in orbit? You get twice as much sun - best case - but you've got to do a conversion... you've got to turn those electrons into photons and turn those photons back into electrons on the ground, and that double conversion is going to get you back to where you started, basically...

Also remember that with Tesla, Musk is selling the concept that solar panels and batteries are the answer.
He's even talked about power plants that cover thousands of square miles with solar panels (link here (https://www.popularmechanics.com/science/green-tech/a30188222/elon-musk-solar-farm/)).

To be clear, I think rooftop solar panels are great, but for powering industry and dense urban areas, there are better solutions.
For example, solar-thermal power plants store excess energy as heat in the form of molten salt. Way cheaper than batteries.
I also think solar and nuclear are complementary. Nuclear supplies baseline power at night, solar provides power during the day.

But since Musk only sells solar panels and batteries, he has a vested interest in playing down other competing solutions.
And given that the first Mars settlement will attract huge amounts of media attention, if Musk can do it with just solar panels and batteries, that will be a ton of free advertising for Tesla.

I wonder if he might change his mind once one of the early proto-colonies has a planet-wide dust storm  that lasts for weeks or months.
I suspect he has thought of that and will take sufficient to provide basic power during the worst of the dust storms and still be able to produce sufficient propellant when the weather clears.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/20/2020 10:32 am
We all know SpaceX is going to use solar to start with and it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use. 
It's unlikely that batteries to power the electrolyzer will be more efficient than oversizing it, so along with the generally higher power demand during the day while people are awake/working, it is likely that only a tiny portion of generation would be stored for night.

Excellent point.

Dr. Zubrin also mentioned this in his recent interview on The Space Show (https://www.thespaceshow.com/show/11-feb-2020/broadcast-3459-dr.-robert-zubrin) (starting at 1:11:00 into the mp3 audio program).
Quote from: Dr. Robert Zubrin, The Space Show, 11 Feb 2020
To refuel a Starship you need at least 600kW if not a mW depending on how their weights ultimately turn out to be...
ISRU doesn't need, how can I put it, reliable power...
Life support you must have power all the time, period.
ISRU, so long as the average power is enough to get the job done, it can proceed in stops and starts.

So it appears that night time power demand may be a small fraction of what is used during the day.

With this in mind, the amount of batteries required may be much less than some people are estimating.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/20/2020 10:50 am
Do we need (bulk storage) batteries? 
Some batteries are obviously beneficial (e.g. reliability, system restarts), but the mass budget for incremental fuel/oxidiser production, storage and generation may be less than for the equivalent battery storage.

Electricity->methane->electricity is apparently ~30-38% efficient (43-54% if you can use the heat too), so something like double to triple the solar plus small increases in electrolyzer etc, vs 10-25% more solar for batteries plus rather heavy batteries. Might well be lighter.

Where do these efficiency numbers come from?

I ask because high efficiency power systems on Earth can often get quite large and heavy.
By contrast, using ISRU methane/LOX as an emergency backup may use a much smaller generator.

But if there are smaller lighter generators with those types of efficiency numbers, then yes,
it may be better for the settlement to run primarily using ISRU methane/LOX power at night, as hoardsbane suggests.

By the way, batteries aren't perfect. They also have some efficiency losses.
A quick Google search popped up numbers around 80-90% for Li-ion charge/discharge efficiency.
Also, the kWh rating of a battery pack often assumes something close to room temperature.
At very cold temperatures, Li-ion batteries can lose nearly half of their kWh capacity.
So keeping the batteries warm in a Martian climate may affect their overall efficiency.

Also, if you charge to 100% and discharge to 0%, Li-ion doesn't last very long. Maybe 500 charge/discharge cycles.
To get them to last longer, I've heard Li-ion needs to stay somewhere between 25% to 85% charge, or something like that.
So tuning the batteries for better longevity may also affect the amount of batteries required.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/20/2020 12:51 pm
Salt Water Battery

By the way, batteries aren't perfect. They also have some efficiency losses.
A quick Google search popped up numbers around 80-90% for Li-ion charge/discharge efficiency.
Also, the kWh rating of a battery pack often assumes something close to room temperature.
At very cold temperatures, Li-ion batteries can lose nearly half of their kWh capacity.
So keeping the batteries warm in a Martian climate may affect their overall efficiency.

Also, if you charge to 100% and discharge to 0%, Li-ion doesn't last very long. Maybe 500 charge/discharge cycles.
To get them to last longer, I've heard Li-ion needs to stay somewhere between 25% to 85% charge, or something like that.
So tuning the batteries for better longevity may also affect the amount of batteries required.

The Aquion salt water battery has interesting properties. 

It can discharge 100%, with > 90% efficiency, to 3000 cycles.  And unlike a Li-ion battery, it maintains its kWh capacity when cold.

Because it's just ISRU saltwater, you could scale as far as you like, for any desired industry, with essentially unlimited service life.  You'd fill batteries, and refill them, on-site, shipping only stacked thin shells -- and that would save tremendous cargo mass, don't you think?

Aquion battery modules (https://www.solarquotes.com.au/blog/aquion-salt-water-battery/) have desirable qualities:  good sub-zero performance, long service life, non-corrosive chemistry, easy infrequent maintenance, no moving parts, etc.  And the ISRU loading process seems relatively straightforward, since it uses abundant electrolytes that require no manufacturing beyond evaporative salt harvest.

So these batteries would ship as empty shells, to be filled with water and perchlorate salts on-site. 

Aquion battery details:  1 (https://www.modernoutpost.com/wp-content/uploads/2017/01/Aquion_Energy_M110-LS83_M110-L083_Product_Specification_Sheet.pdf) 2 (https://www.altestore.com/blog/2016/03/the-rise-of-aquion-batteries-clean-safe-energy-storage/#.Xe_j4dJOnb1) 3 (https://patents.google.com/patent/US8298701B2/en)

Also, one approach to ISRU evaporative perchlorate salt harvest (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1857626#msg1857626).
Title: Re: Power options for a Mars settlement
Post by: spacenut on 02/20/2020 02:20 pm
Back when I was working, natural gas (methane) fuel cells were only 40-45% efficient in the transfer of energy from chemical to electrical.  It was far more efficient to burn the gas in a turbine to produce electricity. 

Re-chargeable batteries will probably be used for storage of power for night use.  Cheap flywheels made from Mars iron ore could also be used. 

What the colonists will probably have to do initially is turn off all power but essential power at night.  Use batteries for essential power.  Then recharge and start work during the day. 

I think also at some point solar will need to be elevated and be able to track the sun for more efficiency during the day. 
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/20/2020 02:48 pm
Well, when the headlines say "power options" then we have to discuss nuclear.  We all know SpaceX is going to use solar to start with and it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use. 

Do we need (bulk storage) batteries? 

Could you just oversize methane/hydrogen and oxygen production and storage (only slight impact on the associated solar farm due the efficiency differences?) and use fuel cells or internal combustion engines (waste heat being useful) and the surplus fuel/O2 for times when there is insufficient insolation (night and storms)?

Some batteries are obviously beneficial (e.g. reliability, system restarts), but the mass budget for incremental fuel/oxidiser production, storage and generation may be less than for the equivalent battery storage.



Thoughts?

Review the thread. The trades have been discussed in detail.

My take: it's probably prudent to have a turbine generator set you can fuel from methalox but only for backup during the decadal storms, not as a general energy storage system. Prior to having nuclear, it may make more sense to size ISRU methalox production so that you only run it during the day time, that way you don't need really large battery farms. If you can ISRU the batteries themselves (salt water batteries may be ideal for this, as LMT alludes to, but there are other low tech batteries) then after you have a vast farm, you run methalox 24/7, effectively doubling your output without increasing plant size ( to a first order ).

There are people with different views.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 02/20/2020 02:51 pm
Would Cryogenic energy storage be of any use on Mars? Obviously they would need to use CO2 rather than air but in principle it should work in a similar fashion.Compress and cool the Martian atmosphere and store the liquid or solid under modest pressure until it's needed then allow it to boil or sublime and allow the resultant pressurised gas to power a turbine.

https://www.highviewpower.com/technology/ (https://www.highviewpower.com/technology/)

Modifications to the basic Highview setup would be needed but in principle I think it should work. With all the Starships Musk is planning to send to Mars there should be some spare tankage available as well as compressors and cryogenic equipment for ISRU. Thoughts?
Title: Re: Power options for a Mars settlement
Post by: spacenut on 02/20/2020 02:52 pm
Studies will have to be done by SpaceX to find out the most bang for the buck.  Also, weight or mass will have to be taken into consideration if equipment has to be transported to Mars.  Solar initially is fine, but they will have to have some kind of backup power when dust storms occur. 
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/20/2020 05:47 pm
Well, when the headlines say "power options" then we have to discuss nuclear.  We all know SpaceX is going to use solar to start with and it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use.

In addition to Yaotzin's point above (that the usage will likely not be constant), also if your panels aren't tracking then the solar output needs to be pi times what you will actually use, to account for cosine losses.


...
Dr. Zubrin also mentioned this in his recent interview on The Shape Show (https://www.thespaceshow.com/show/11-feb-2020/broadcast-3459-dr.-robert-zubrin) (starting at 1:11:00 into the mp3 audio program).
Quote from: Dr. Robert Zubrin, The Shape Show, 11 Feb 2020
To refuel a Starship you need at least 600kW if not a mW depending on how their weights ultimately turn out to be...
ISRU doesn't need, how can I put it, reliable power...
Life support you must have power all the time, period.
ISRU, so long as the average power is enough to get the job done, it can proceed in stops and starts.

Er, it's The Space Show.

Note that The Space Show's creator requires quotes be accompanied by a proper citation (see the second paragraph of that page), so here it is:

Livingston, D. (Host and Founder) & Zubrin, R. (Guest). (2020, February 11). The Space Show Broadcast 3459 Dr. Robert Zubrin [Audio podcast]. https://www.thespaceshow.com/show/11-feb-2020/broadcast-3459-dr.-robert-zubrin
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 02/20/2020 05:49 pm
An interesting discussion about earth infrastructure but apply to mars. 
Many topics raised in this thread are discussed.

Center for Strategic & International Studies: Innovation in Storage and Battery Technologies
https://www.youtube.com/watch?v=PZM7EklTCPs
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/20/2020 06:15 pm
CAES

Would Cryogenic energy storage be of any use on Mars? Obviously they would need to use CO2 rather than air but in principle it should work in a similar fashion.Compress and cool the Martian atmosphere and store the liquid or solid under modest pressure until it's needed then allow it to boil or sublime and allow the resultant pressurised gas to power a turbine.

https://www.highviewpower.com/technology/ (https://www.highviewpower.com/technology/)

Modifications to the basic Highview setup would be needed but in principle I think it should work. With all the Starships Musk is planning to send to Mars there should be some spare tankage available as well as compressors and cryogenic equipment for ISRU. Thoughts?

Site down?

One advantage of compressed-air energy storage (CAES) over ISRU batteries is that it can be implemented earlier in base development, without requiring the ISRU battery industry of e.g. salt water electrolyte manufacture (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048640#msg2048640).

For example, CAES can be scaled at sites having abundant ice, via pressurized melt chambers (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1935540#msg1935540) and a regolith gravel adiabatic heat store (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2024717#msg2024717).  Here the dedicated supporting industry is relatively simple, conceivably just CO2-mediated aerogel manufacture (https://www.sciencedirect.com/science/article/pii/S1877705813007583/pdf?md5=4fff766557d150a312154ac8272202df&isDTMRedir=Y&pid=1-s2.0-S1877705813007583-main.pdf&_valck=1) (from minor cargo), electric ice melt, and regolith dozing -- industry plausibly required already for other purposes early in base development.

LCH4 can also be used in a CAES system; again, with little dedicated supporting industry.  Wang et al. 2017 leverages both LCO2 and LCH4, wherein LCH4 acts as cold source and heat sink.

Quote from: Wang et al. 2017
No matter how the heat source mass flow rate or temperature varies, both the CO2 turbine and the NG [CH4] turbine could almost keep the designed values of efficiency, which implies the feasibility of the applied control strategy.

Refs.

Wang, J., Wang, J., Dai, Y., & Zhao, P. (2017). Off-design performance analysis of a transcritical CO2 Rankine cycle with LNG as cold source. International Journal of Green Energy, 14(9), 774-783.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/20/2020 07:26 pm
...it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use.

...if your panels aren't tracking then the solar output needs to be pi times what you will actually use, to account for cosine losses.

On Earth, real tracking boosts performance just 30% (https://www.sciencedirect.com/science/article/abs/pii/S1364032117308936), 20% (https://www.researchgate.net/profile/George_Cristian_Lazaroiu/publication/281554970_2015_ECM_Lazaroiu_Longo_Roscia_Pagano/links/55ed8f0e08aeb6516268ea9c.pdf), or even less (https://www.sciencedirect.com/science/article/abs/pii/S1364032111002772).  Mars light diffusion (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010257.pdf) would cut into even those small gains.  It seems simpler and net gain to replace tracking hw mass with more panels.  As kW/kg improves, this rationale also improves.
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/20/2020 08:43 pm
...it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use.

...if your panels aren't tracking then the solar output needs to be pi times what you will actually use, to account for cosine losses.

On Earth, real tracking boosts performance just 30% (https://www.sciencedirect.com/science/article/abs/pii/S1364032117308936), 20% (https://www.researchgate.net/profile/George_Cristian_Lazaroiu/publication/281554970_2015_ECM_Lazaroiu_Longo_Roscia_Pagano/links/55ed8f0e08aeb6516268ea9c.pdf), or even less (https://www.sciencedirect.com/science/article/abs/pii/S1364032111002772).  Mars light diffusion (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010257.pdf) would cut into even those small gains.  It seems simpler and net gain to replace tracking hw mass with more panels.  As kW/kg improves, this rationale also improves.


I think you're probably right but working the trades might reveal that ISRU frames and imported bearings/motors are a better trade than more panels, at least before you can ISRU panels. (or it might not) Once you can ISRU panels, even low efficiency ones, all trades need to be redone.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/20/2020 09:11 pm
...it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use.

...if your panels aren't tracking then the solar output needs to be pi times what you will actually use, to account for cosine losses.

On Earth, real tracking boosts performance just 30% (https://www.sciencedirect.com/science/article/abs/pii/S1364032117308936), 20% (https://www.researchgate.net/profile/George_Cristian_Lazaroiu/publication/281554970_2015_ECM_Lazaroiu_Longo_Roscia_Pagano/links/55ed8f0e08aeb6516268ea9c.pdf), or even less (https://www.sciencedirect.com/science/article/abs/pii/S1364032111002772).  Mars light diffusion (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010257.pdf) would cut into even those small gains.  It seems simpler and net gain to replace tracking hw mass with more panels.  As kW/kg improves, this rationale also improves.


I think you're probably right but working the trades might reveal that ISRU frames and imported bearings/motors are a better trade than more panels, at least before you can ISRU panels. (or it might not) Once you can ISRU panels, even low efficiency ones, all trades need to be redone.

Well, ISRU pylons (https://forum.nasaspaceflight.com/index.php?topic=41937.msg1869018#msg1869018) make sense, either way.  But what are the prospects for ISRU panels?  (Massive) regolith substrate (https://www.researchgate.net/publication/245139940_First_demonstration_of_photovoltaic_diodes_on_lunar_regolith-based_substrate) seems feasible with small infrastructure, but PV active layers?
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/20/2020 09:11 pm
...it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use.

...if your panels aren't tracking then the solar output needs to be pi times what you will actually use, to account for cosine losses.

On Earth, real tracking boosts performance just 30% (https://www.sciencedirect.com/science/article/abs/pii/S1364032117308936), 20% (https://www.researchgate.net/profile/George_Cristian_Lazaroiu/publication/281554970_2015_ECM_Lazaroiu_Longo_Roscia_Pagano/links/55ed8f0e08aeb6516268ea9c.pdf), or even less (https://www.sciencedirect.com/science/article/abs/pii/S1364032111002772)...
Doesn't this depend on your latitude?  For example, would tracking boost performance more if you're near the equator?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/20/2020 09:41 pm
...it will have to have battery backup, so the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use.

...if your panels aren't tracking then the solar output needs to be pi times what you will actually use, to account for cosine losses.

On Earth, real tracking boosts performance just 30% (https://www.sciencedirect.com/science/article/abs/pii/S1364032117308936), 20% (https://www.researchgate.net/profile/George_Cristian_Lazaroiu/publication/281554970_2015_ECM_Lazaroiu_Longo_Roscia_Pagano/links/55ed8f0e08aeb6516268ea9c.pdf), or even less (https://www.sciencedirect.com/science/article/abs/pii/S1364032111002772).  Mars light diffusion (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010257.pdf) would cut into even those small gains.  It seems simpler and net gain to replace tracking hw mass with more panels.  As kW/kg improves, this rationale also improves.

Oops, sorry for the confusion. I was making an argument for using the correct numeric constants, not for tracking PV.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/20/2020 09:55 pm
Do we need (bulk storage) batteries? Could you just oversize methane/hydrogen and oxygen production and storage [...] and use fuel cells or internal combustion engines (waste heat being useful) and the surplus fuel/O2 for times when there is insufficient insolation (night and storms)?
Some batteries are obviously beneficial (e.g. reliability, system restarts), but the mass budget for incremental fuel/oxidiser production, storage and generation may be less than for the equivalent battery storage.

We went through the numbers earlier in the thread. The inefficiency of electrolysing the water back into hydrogen and oxygen, combined with the losses from the generator itself makes batteries a superior option. (Or at least, no better than break even.) And since you've already got solar plus batteries, you benefit from having lots of units of one type of thing, rather than unique systems with different requirements. If you have excess PV capacity, you can throw some panels out in the wilderness on comms arrays, or science stations, or set up power generating waystations along vehicle routes (so they recharge without returning to base). Etc etc. Similarly, the same battery packs used in vehicles get used in the habitat, so you can swap and salvage as required. Same packs would get used in the Starships, for the same reason.

You want, as much as possible, to have easy exchange of parts between systems. You do not want a dense ecosystem of unique or small-batch items. That also favours more solar, more batteries, over an emergency methalox generators that mostly doesn't get used.



Re: Battery lifecycle.

Lithium and many other types of batteries can be recycled. You aren't consuming anything irrevocably. (Well, there's going to be losses, but you can import the difference. The bulk mass is salvageable.) Additionally, you can extend the useful life of batteries by passing them through phases: Vehicle packs (range matters), outbuilding power, main settlement power, distant stations, then recycle the electrodes. Between phases, you remove dead or dying cells from the pack and put them in recycling, the rest of the pack can go back into use.



the solar output has to be about double what you actually will use, because it also has to charge the batteries for night use.
In addition to Yaotzin's point above (that the usage will likely not be constant), also if your panels aren't tracking then the solar output needs to be pi times what you will actually use, to account for cosine losses.

Not quite. Modest amounts of dust in Mars' atmosphere spreads the sunlight out without dimming it, and modern panels can accept a wide angle-of-incidence, so you aren't limited to a simple cross-sectional-area (cosine angle). No tracking required. Additionally, the same diffraction of sunlight produces more light before sunrise and after sunset, extended the "day". Mars is oddly well suited for PV solar.

The only thing that would be useful is to slightly raise the angle of the panels towards the equator. Without wind, a simple length of wire on the high-side, suspended by pegs or rods. Nothing elaborate. Presumably, given that you need an electrical connection down the length, that could be your wire.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/20/2020 10:29 pm
Doesn't this depend on your latitude?  For example, would tracking boost performance more if you're near the equator?

Mars light diffusion (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010257.pdf) would cut into even those small gains.

Actually, the untrackable diffuse fraction increases with decreasing latitude.  Tables II, III. (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010257.pdf)
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/20/2020 10:39 pm
the same diffraction of sunlight produces more light before sunrise and after sunset, extended the "day". Mars is oddly well suited for PV solar.

Mars twilight flux?
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/21/2020 02:21 am
the same diffraction of sunlight produces more light before sunrise and after sunset, extended the "day". Mars is oddly well suited for PV solar.

Mars twilight flux?

It's < 3% of noon max.  Appelbaum & Flood 1990.  Comparable to storm blackout.

So martian twilight is not suited to PV -- but it is suited to atmospheric triboelectricity.  E.g., attach balloons to the dormant solar panels, and modest power production continues after sunset. 

Image:  Baumgaertner 2016, illustration 9. 

Refs.

Appelbaum, J., & Flood, D. J. (1990). Solar radiation on Mars. Solar Energy, 45(6), 353-363.

Baumgaertner, A. (2016). Power to Mars.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/21/2020 08:34 am
And since you've already got solar plus batteries, you benefit from having lots of units of one type of thing, rather than unique systems with different requirements....

the same battery packs used in vehicles get used in the habitat, so you can swap and salvage as required. Same packs would get used in the Starships, for the same reason.

You want, as much as possible, to have easy exchange of parts between systems. You do not want a dense ecosystem of unique or small-batch items.
Good point. 

This reminds me of Apollo 13 where they had to put a square peg in a round hole (https://history.nasa.gov/SP-350/ch-13-4.html) because different companies had designed the LEM and Command Module. While this was an ingenious fix, it may have been better if they had used common interchangeable lithium hydroxide canisters.

So as a general rule, yes, you want to have easy exchange of parts between systems, but there are exceptions.

That also favours more solar, more batteries, over an emergency methalox generators that mostly doesn't get used.
With dust storms that could last for months, the amount of batteries required to handle this scenario may be much larger than a backup methalox generator.

Also, when designing for fault tolerance, it's often more reliable to use a different type of system as an emergency backup.

So this may be one exception to the general rule of trying to use interchangeable parts wherever possible.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 02/21/2020 08:58 am
the same diffraction of sunlight produces more light before sunrise and after sunset, extended the "day". Mars is oddly well suited for PV solar.

Mars twilight flux?

It's < 3% of noon max.  Appelbaum & Flood 1990.  Comparable to storm blackout.

So martian twilight is not suited to PV -- but it is suited to atmospheric triboelectricity.  E.g., attach balloons to the dormant solar panels, and modest power production continues after sunset. 

Image:  Baumgaertner 2016, illustration 9. 

Refs.

Appelbaum, J., & Flood, D. J. (1990). Solar radiation on Mars. Solar Energy, 45(6), 353-363.

Baumgaertner, A. (2016). Power to Mars.

The Baumgartner paper assumes that :
a) a Martian Global Electrical Circuit exists (still unproven)
and
b) has current density thousands of times greater than Earth's (based on a 2001 paper)
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/21/2020 12:36 pm
the same diffraction of sunlight produces more light before sunrise and after sunset, extended the "day". Mars is oddly well suited for PV solar.

Mars twilight flux?

It's < 3% of noon max.  Appelbaum & Flood 1990.  Comparable to storm blackout.

So martian twilight is not suited to PV -- but it is suited to atmospheric triboelectricity.  E.g., attach balloons to the dormant solar panels, and modest power production continues after sunset. 

Image:  Baumgaertner 2016, illustration 9. 

Refs.

Appelbaum, J., & Flood, D. J. (1990). Solar radiation on Mars. Solar Energy, 45(6), 353-363.

Baumgaertner, A. (2016). Power to Mars.

The Baumgartner paper assumes that :
a) a Martian Global Electrical Circuit exists (still unproven)
and
b) has current density thousands of times greater than Earth's (based on a 2001 paper)

Oh, the science (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850474#msg1850474) was never controversial; there just hasn't been a lander instrument.  ExoMars launched with such an instrument, Micro-ARES, within (DREAMS (https://exploration.esa.int/web/mars/-/58430-dreams-surface-operations)).

There's no real basis to the forum's longstanding resistance (pun) to that power method.  Explore the science; be more intellectually aggressive.

Image:  "Schiaparelli - without heat shield and back cover."  ESA/ATG medialab.

Quote from: Baumgaertner
While still not directly observed, there are many indications that a GEC exists on Mars. It is driven by dust storms, which frequently occur on Mars. The dust storms are created by solar heating of the Martian surface. Therefore, the GEC is effectively driven by solar insolation similar to the GEC on Earth.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/21/2020 01:44 pm
...

There's no real basis to the forum's longstanding resistance (pun) to that power method.  Explore the science; be more intellectually aggressive.

I don't want someone with this philosophy designing the colony I live in.

When human lives are on the line, the last thing you want is to be "intellectually aggressive," especially with unknown variables. As Akin reminds us (https://spacecraft.ssl.umd.edu/akins_laws.html),

Quote
Law #44: Space is a completely unforgiving environment. If you screw up the engineering, somebody dies (and there's no partial credit because most of the analysis was right...)
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/21/2020 02:45 pm
There's no real basis to the forum's longstanding resistance (pun) to that power method.  Explore the science; be more intellectually aggressive.

I don't want someone with this philosophy designing the colony I live in.

When human lives are on the line, the last thing you want is to be "intellectually aggressive," especially with unknown variables.

Being intellectually aggressive (https://ludwig.guru/s/intellectually+aggressive) is a way to manage unknowns, and make progress.  Healthy.

Re "lives are on the line": you're pitching (literally) a bouncy house (https://forum.nasaspaceflight.com/index.php?topic=49532.msg2048150#msg2048150) for Starship landings. 

Save the histrionics.

Edit/Lar: save the accusations of bad faith against others.
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/21/2020 02:49 pm
I think you're probably right but working the trades might reveal that ISRU frames and imported bearings/motors are a better trade than more panels, at least before you can ISRU panels. (or it might not) Once you can ISRU panels, even low efficiency ones, all trades need to be redone.

Well, ISRU pylons (https://forum.nasaspaceflight.com/index.php?topic=41937.msg1869018#msg1869018) make sense, either way.  But what are the prospects for ISRU panels?  (Massive) regolith substrate (https://www.researchgate.net/publication/245139940_First_demonstration_of_photovoltaic_diodes_on_lunar_regolith-based_substrate) seems feasible with small infrastructure, but PV active layers?
Yes, low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/21/2020 02:53 pm
There seems to be an increase in sniping. People are liable to lose posts if we can't be excellent to each other. If I edited one of your posts, the next time I see sniping, you're going to lose the entire post, because I don't have time to edit things.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/21/2020 03:11 pm
low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.

Lunar ISRU PV would need significant refining, too; maybe molten oxide electrolysis (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiT4uvSg-PnAhVjHjQIHXVxBOEQFjABegQIBRAE&url=http%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunarisru2019%2Fpdf%2F5012.pdf&usg=AOvVaw3At_1Ypea9h9HZRAhPeD7P) gives a starting point.  Its liquid metal output could go to a refinery, such as an electrolysis cell.  How might you stage a refinery, to produce e.g. purified silicon for PV?
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/21/2020 05:57 pm
low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.

Lunar ISRU PV would need significant refining, too; maybe molten oxide electrolysis (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiT4uvSg-PnAhVjHjQIHXVxBOEQFjABegQIBRAE&url=http%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunarisru2019%2Fpdf%2F5012.pdf&usg=AOvVaw3At_1Ypea9h9HZRAhPeD7P) gives a starting point.  Its liquid metal output could go to a refinery, such as an electrolysis cell.  How might you stage a refinery, to produce e.g. purified silicon for PV?
I can't find the paper right now, but I remember they postulated making cells directly on the ground. No refining. Efficiency was terrible but they didn't care. Basically a robotic device loaded with the necessary trace elements, and connection wire, would sinter lunar regolith that was high silicon content and during the sintering process turn it into low efficiency cells and bond wire to it
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/21/2020 06:45 pm
With dust storms that could last for months, the amount of batteries required to handle this scenario may be much larger than a backup methalox generator.

Again, while the decadal dust storms can last for months, the worst storm conditions do not last months, but an odd day or two here and there. If you shut down ISRU propellant production as the storm approaches, you have enough extra PV capacity to keep the batteries topped up, along with surplus batteries. You only run your batteries down during the absolute worst days. So your methalox generator would only be used for a few days every ten years.

OTOH, having surplus batteries (and PV) gives you more capacity during clear sky periods to waste power on non-essential, experimental activities. Sintering regolith into roads and building materials, for example. High-temp material processing for chemical extraction. Expanding water "mining" into new areas. Adding new ISRU processes, to reduce dependence of Earth. Exploring and doing science over wider areas (vehicles use power, lab equipment is stupidly power-hungry). It also provides routine over-capacity for mundane failures, without tapping into your propellant storage.

(BTW, vehicle battery packs can also be used to supplement the habitat's storage during the worst periods in the middle of the worst dust storms. During the less-than-worst parts of the storm, you can still generate enough extra power to keep the vehicles topped up and use them for EVAs. If you turn off your production systems, you free up staff for maintenance runs on outlying equipment.)

You can also delay planting new Ag spaces during this period, giving you more spare capacity to continue the remaining Ag spaces to harvest. During the very bad periods, you reduce the lighting in the Ag spaces that are in their grow-cycle. Turn it down, not off. Equivalent of a few overcast days. In nature, that's a 20-fold variation between sunny and overcast days, 95% reduction in power levels. (Plants slow or stop growing, they don't die unless it persists.) You can also transition some crops from grow-cycle to an early flowering/fruiting cycle (switch from 18hr light cycle to 12hr light cycle, cutting power use by a third) and accept a reduced yield. You'd have a food reserve intended to cover you losing two entire crop cycles to contamination/disease or blow-out, so covering a reduced-yield dust-storm is already built into the system.

There really isn't a scenario other than "interstellar cloud blocks out the sun" that requires using a methalox generator.

[edit: than/that]



Contradicting myself, if the genny set masses only a few tonnes to cover the core life-support requirements... WTF not.
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/21/2020 09:01 pm
Contradicting myself, if the genny set masses only a few tonnes to cover the core life-support requirements... WTF not.
I think we all fall into the trap of thinking pre fuel-rich architecture from time to time, especially for follow on loads of cargo. WTF not indeed. It's only a few tonnes. Also WTF not lots of extra cells too. And nuke when it comes available.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/21/2020 10:17 pm
There's no real basis to the forum's longstanding resistance (pun) to that power method.  Explore the science; be more intellectually aggressive.

I don't want someone with this philosophy designing the colony I live in.

When human lives are on the line, the last thing you want is to be "intellectually aggressive," especially with unknown variables.

Being intellectually aggressive (https://ludwig.guru/s/intellectually+aggressive) is a way to manage unknowns, and make progress.  Healthy.

"Make progress" = "learn stuff" = "make mistakes." I don't want to rely on a bleeding-edge system for survival, I want a nice known (as much as can be) solution. Certainly we should do experiments on such things, but that's no substitute for a nice low-risk system.

Re "lives are on the line": you're pitching (literally) a bouncy house (https://forum.nasaspaceflight.com/index.php?topic=49532.msg2048150#msg2048150) for Starship landings.

Is HIAD "literally" a bouncy house? Because if so, NASA could've saved a lot of R&D and just rented one.

Besides, what I'm proposing in that thread is more like a kiddy pool (there was some confusion on this point, since resolved). Starship wouldn't actually sit on the inflated portion, just on a flexible thermal shield / landing pad which is deployed by one or more outer inflatable toruses. But that's a topic for the other thread.

Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/22/2020 01:30 am
Re "lives are on the line": you're pitching (literally) a bouncy house (https://forum.nasaspaceflight.com/index.php?topic=49532.msg2048150#msg2048150) for Starship landings.

I should point out that I am Spartacus proposed the bouncy castle, not Twark_Main.

And since you're using it as a comparison with your TE-power proposal: I proposed the inflatable landing-pad as an exercise in taking an idea to its extreme to show that the maths sort-of works, in a thread where we are throwing out extreme ideas for fun.

If you are saying that your TE-power proposal is you taking a micro-scale effect and exaggerating it for a bit of silly fun, then I don't see why you would criticise the skepticism towards it. Just as I don't criticise Twark_Main's skepticism about my bouncy-castle landing-pad.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/22/2020 02:15 am
There's no real basis to the forum's longstanding resistance (pun) to that power method.  Explore the science; be more intellectually aggressive.
I don't want someone with this philosophy designing the colony I live in.
When human lives are on the line, the last thing you want is to be "intellectually aggressive," especially with unknown variables.
Being intellectually aggressive (https://ludwig.guru/s/intellectually+aggressive) is a way to manage unknowns, and make progress.  Healthy.
"Make progress" = "learn stuff" = "make mistakes." I don't want to rely on a bleeding-edge system for survival, I want a nice known (as much as can be) solution. Certainly we should do experiments on such things, but that's no substitute for a nice low-risk system.

This reminds me of the adage: "Good/Cheap/Fast — you can only pick two".  In this case, I'd say Good = Lower Risk.

Of these 3 design factors, it seems clear to me that Musk is prioritizing "Fast".
For example, in a YouTube interview with Garrett Reisman, a former NASA astronaut who now works for SpaceX said:
Quote from: Garrett Reisman
In fact, he (Elon Musk) measures pretty much every major decision by whether or not it brings the day when we have a self-sustainable colony on Mars sooner or later.  That's the prism by which he makes every... Every single decision he makes, he makes it through that prism.

Also, given that SpaceX doesn't have unlimited funds, cost must also be a priority.

So if you believe the adage that you can only pick 2 of the 3 design criteria above,
it shouldn't surprise people if SpaceX's plans for Mars are willing to accept higher levels of risk.

For example, Dr. Zubrin's Mars Direct plan has the ISRU return propellant ready and waiting before any crew leaves Earth.
By contrast, Musk's plan clearly shows propellant production starting after the first crew arrives (see attached slide).
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/23/2020 01:36 am
Musk may not use nuclear power initially, but if Mars settlements are installed, NASA will want to be part of it.
This may mean NASA will provide the nuclear power in exchange for some research facilities at the Mars settlement.  To expand it only makes sense. 

Even in America's power system, there are multiple power sources.  Nuclear about 20%, natural gas about 37% now.  Coal < 30% and dropping.  About 10% from hydro and another 10% from wind/solar sources.  Natural gas (methane on Mars) is growing while coal is decreasing.  This has resulted in America cutting CO2 production faster than any country in the world percentage wise.  Also American vehicles are using less fuel as more hybrids and electrics come into play. 

Mars too will need multiple power sources.  If something happens to one, there should always be a backup.  All agree solar initially with methane as backup and later nuclear.  Wind might be a source at some future time where canyons or such areas have higher wind conditions on Mars.  There will be no water power, coal, or fuel oil, unless it is somehow discovered on Mars, but that would mean some type of carbon based life form that once lived on Mars as well as ancient oceans.

You spoke of SX playing it’s cards right in an earlier post. The way those cards play is something like what you say here. The trick is to get NASA involved in the early missions without letting them take over.

Sell NASA some number of  seats and some specific cargo capacity. Provide all habitat, ECLSS and food once on mars. Part of the price is providing a reactor. It should be an easy sell because it is to the benefit of all.

The secret to SX’s mission independence is to not depend on the reactors output. Plan on SX operations being 100% solar and see the nuke power as being strictly emergency backup. NASA can use its output in any way they want with the contractual requirement that it is, in the end, an emergency backup. If the reactor is big enough this might stretch to covering props production during a killer dust storm so everybody can rotate home on time.

After the first missions, as SX is bringing outside vendors in to maintain vital services, the DOE difficulties about privately owned reactors will morph into a routine application for a municipal power reactor. One of the outside vendors would be a company that routinely operates reactors earthqside.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/23/2020 02:00 am
Musk may not use nuclear power initially, but if Mars settlements are installed, NASA will want to be part of it.
Yes, but NASA tends to move slowly. The only exception was during the Cold War.

Even in America's power system, there are multiple power sources.  Nuclear about 20%, natural gas about 37% now.  Coal < 30% and dropping.  About 10% from hydro and another 10% from wind/solar sources...
Note that solar panels currently only account for 1.4% of our total electricity (link here (https://www.eia.gov/tools/faqs/faq.php?id=427&t=3)).

Natural gas... is growing while coal is decreasing.  This has resulted in America cutting CO2 production faster than any country in the world percentage wise...
That depends on what time frame your're looking at. In the 80's and 90's, France ramped up nuclear power in a big way.
Today, France is around 70% nuclear (link here (https://en.wikipedia.org/wiki/Nuclear_power_in_France)). Meanwhile, Germany has shunned nuclear and concentrated on renewables.
The result is that today, per-capita CO2 emissions in Germany are about twice what they are in France.
This is one of the reasons I've changed my mind and become pro-nuclear.

But for a Mars settlement, Musk has made it pretty clear. They're only using solar panels. They're not using nuclear.

While he’s made it clear that PV is what he intends to use, I’ve not seen anything indicating that Musk dislikes nuclear per se. He has PV and he doesn’t have a reactor.

The political and administrative barriers (close but not quite the same) are high and unless he plays his cards right the only way he’d get a reactor is by groveling. He doesn’t want anybody having him by the short and curlies that way.

Phil
Title: Re: Power options for a Mars settlement
Post by: Lar on 02/23/2020 02:21 am
Getting a reactor as an add on AFTER an all solar (or solar + methalox genset) solution is up and running will be WAY easier. He won't have to grovel, NASA will be trying to stay relevant and a reactor is a way to do that.
Title: Re: Power options for a Mars settlement
Post by: oiorionsbelt on 02/23/2020 03:22 am

.......
While he’s made it clear that PV is what he intends to use, I’ve not seen anything indicating that Musk dislikes nuclear per se. He has PV and he doesn’t have a reactor.
........


Phil
Indeed, Elon/SpaceX are not only not opposed to nuclear, they were actively pursuing it.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/23/2020 01:28 pm
Getting a reactor as an add on AFTER an all solar (or solar + methalox genset) solution is up and running will be WAY easier...
It can also happen way sooner.

I think we're witnessing a fundamental transformation in human space flight.
20 years ago, human space flight was exclusively the domain of governments.
10 years ago, the prevailing wisdom was that governments would do BEO while private industry might do LEO (maybe).
5 years ago, people were starting to consider a public/private partnership for BEO crew missions.
Today, many are starting to believe the first footprints on Mars will be completely privately funded.

This latest paradigm is even more possible considering SpaceX wants to get to Mars as soon as possible,
while at the same time NASA is bogged down with SLS, Orion, the Lunar Gateway, and some to-be-announced lunar lander.

With this in mind, it's quite possible SpaceX won't want any ties with NASA for their initial Mars crew missions.
This may be part of the reason SpaceX is developing Starship at their South Texas launch site.

If this scenario comes to pass, then nuclear power will be a non-starter for the initial Mars settlement.
Title: Re: Power options for a Mars settlement
Post by: wes_wilson on 02/23/2020 03:21 pm
Getting a reactor as an add on AFTER an all solar (or solar + methalox genset) solution is up and running will be WAY easier. He won't have to grovel, NASA will be trying to stay relevant and a reactor is a way to do that.

Agree.  Biggest issue with nuclear is everyone wants NIMBY and if Mars is anything it's NIMBY.  Building, testing, mining, researching, and operating nuclear entirely at Mars might be much simpler and less objectionable than on Earth.  The people who live there will want it and if they're doing (the nuclear parts of it) entirely on Mars then no risks to the people here who oppose it.  Bits and pieces can still go from here to there, just not the nuclear material.

My guess is it starts with solar, grows with solar, and nuclear is one of the technologies truly cultivated and advanced on Mars by people living there.  It's a Chapter two issue & solution in the Mars story.  Nasa & the military may be both be interested in funding research there that can later be applied here.





Title: Re: Power options for a Mars settlement
Post by: matthewkantar on 02/23/2020 05:08 pm
Thinking about the possibilities is exciting. Endless free land to spread out PV panels, a whole new planet to prospect for raw materials. Exploiting fissile materials tens of millions of miles from any red tape is very appealing.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/23/2020 06:14 pm
Getting a reactor as an add on AFTER an all solar (or solar + methalox genset) solution is up and running will be WAY easier...
It can also happen way sooner.

I think we're witnessing a fundamental transformation in human space flight.
20 years ago, human space flight was exclusively the domain of governments.
10 years ago, the prevailing wisdom was that governments would do BEO while private industry might do LEO (maybe).
5 years ago, people were starting to consider a public/private partnership for BEO crew missions.
Today, many are starting to believe the first footprints on Mars will be completely privately funded.

This latest paradigm is even more possible considering SpaceX wants to get to Mars as soon as possible,
while at the same time NASA is bogged down with SLS, Orion, the Lunar Gateway, and some to-be-announced lunar lander.

With this in mind, it's quite possible SpaceX won't want any ties with NASA for their initial Mars crew missions.
This may be part of the reason SpaceX is developing Starship at their South Texas launch site.

If this scenario comes to pass, then nuclear power will be a non-starter for the initial Mars settlement.

As I said earlier (sorry, still don’t know how to work quotes):

“...SX playing it’s cards right... The way those cards play is something like what you say here. The trick is to get NASA involved in the early missions without letting them take over.”

SX and NASA is a live-hate thing. NASA can throw a monkey wrench so many different ways and also be helpful in so many ways. It’s better to have them on your side but at arms length. Stealing their thunder would not be good.

As SS matures and mars starts looking like a real thing NASA will start getting nervous about looking irrelevant. Especially if their BEO plans bog down and are ridiculously expensive. (Taking bets here). The most obvious way to keep them cooperative is to give them a seat at the table as a junior partner with the optics showing them as equals and graciously accept the funding and  nuke power.

Allow them ~1/3 the seats and cargo space on the first crewed mission, provide room and board on mars and let the NASA presence on mars evolve into a separate but parallel effort. With SS promising to be so radically cheap SX can sell them as many seats and as much cargo space as they want without impacting SX plans to any great degree.

This solves several problems with one blow. Part of the cost of these services would reasonably be enough nuke power to allow a base to evolve rapidly and eventually transform into a settlement. Electrical power gives amazing leverage.

Another problem at least mitigated is developing a Martian economy (another thread. Let’s only hit this glancingly). Initially SX will have no choice but to operate infrastructure. In the long term NASA will have to either supply their own infrastructure or farm it out. This is where other businesses get involved.

With NASA as an initial anchor tenant there is a business case for third party vendors. Can NASA do this less expensively? I doubt it. After 3-4 synods the place will look more like Antarctica today than it did during the first days of the IGY. Only after this is there a chance to morph into a settlement. And a settlement will need power. Nuke and PV will both have a role. Only the balance is, in my mind, the question.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/23/2020 06:22 pm
Thinking about the possibilities is exciting. Endless free land to spread out PV panels, a whole new planet to prospect for raw materials. Exploiting fissile materials tens of millions of miles from any red tape is very appealing.

If only it were so. Check out the outer Space Treaty (yet another thread). SX will have to adhere to US laws and regulations. If SX goes ‘rogue’ and cuts NASA out of the picture they might see red tape without end.

Phil
Title: Re: Power options for a Mars settlement
Post by: wes_wilson on 02/23/2020 07:34 pm
Thinking about the possibilities is exciting. Endless free land to spread out PV panels, a whole new planet to prospect for raw materials. Exploiting fissile materials tens of millions of miles from any red tape is very appealing.

If only it were so. Check out the outer Space Treaty (yet another thread). SX will have to adhere to US laws and regulations. If SX goes ‘rogue’ and cuts NASA out of the picture they might see red tape without end.

Phil

Well, I wasn't suggesting anyone go rogue although I know that's a theme sometimes here lol.  My perspective was that much like it was easier to get permission to land boosters on a barge than it was to land at Kennedy; it may be easier to get permission to build and test reactors at Mars than to build and test reactors in the middle of Los Angeles. 

All subject to US control & regulation per the OST; but consent of said government made much easier to obtain by not being near populations of objecting and protesting citizens. 

Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/23/2020 11:09 pm
Thinking about the possibilities is exciting. Endless free land to spread out PV panels, a whole new planet to prospect for raw materials. Exploiting fissile materials tens of millions of miles from any red tape is very appealing.

If only it were so. Check out the outer Space Treaty (yet another thread). SX will have to adhere to US laws and regulations. If SX goes ‘rogue’ and cuts NASA out of the picture they might see red tape without end.

Phil

Well, I wasn't suggesting anyone go rogue although I know that's a theme sometimes here lol.  My perspective was that much like it was easier to get permission to land boosters on a barge than it was to land at Kennedy; it may be easier to get permission to build and test reactors at Mars than to build and test reactors in the middle of Los Angeles. 

All subject to US control & regulation per the OST; but consent of said government made much easier to obtain by not being near populations of objecting and protesting citizens.

Wes, I was less than clear. By rogue I meant doing mars without NASA. Not the best word choice and in the context of another post.

The power requirements for refinement and even low enrichment would in itself suggest that an earth supplied reactor would be handy. This, like everything else can be done with PV but that always seems to put a crimp in things.

It takes x MW to do y. I keep seeing rovers, for example, being limited in speed because the battery swap/charging stations can’t keep up if the batteries go flat too quick. More panels fix this but eventually the base would be surrounded by so many panels there’d be no place to land a ship within reasonable distance. Ok, maybe a bit of hyperbole.

And what’s wrong with a reactor in LA? They get so much sun a little more radiation isn’t going to hurt.  8)

Phil

Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/24/2020 10:39 am
The trick is to get NASA involved in the early missions without letting them take over...

NASA can throw a monkey wrench so many different ways and also be helpful in so many ways...

Allow them ~1/3 the seats and cargo space on the first crewed mission...

I think we're getting to the crux of the issue.  If the first Mars crewed missions include NASA astronauts,
I believe that would impact many aspects of the mission architecture, including power options.
For example, if NASA were involved, then nuclear power becomes an option.

Also, every plan I've seen from NASA has the ISRU return propellant ready and waiting before the first crew departs Earth.
By constant, as I've shown before, Musk's plan clearly shows propellant production starting after the first crew arrives.
Since Musk's plan exposes the crew to significantly more risk, I doubt NASA would accept this.

And as you dig into the details, I suspect there are a many other power options would be affected if NASA were involved.

Note: At the ground breaking ceremony for the South Texas launch site, Musk said:
Quote from: Elon Musk
It very well could be the first person to go to another planet could launch from this location
(link here (https://www.texastribune.org/2014/09/22/brownsville-spacex-facility-might-land-first-mars/)).

If the first crew to Mars included NASA astronauts, I believe the mission would launch from Florida, not Texas.
Also note that Elon said this back in 2014. So it appears that SpaceX has seriously considered going "rouge" for quite a while.

With this in mind, let's look at the pros and cons of having NASA astronauts in the first crewed missions.

Obviously, NASA has a lot of experience to offer, but SpaceX could obtain this experience in other ways.
For example, SpaceX could hire NASA's former head of human spaceflight. Note: When you hire a high-level guy like this,
it's not unusual for some of the people who worked under him to move to the new company as well.
So SpaceX may now be in a position to cherry-pick some of the best and brightest minds at NASA.

Some have mentioned the possibility of leveraging NASA's communication network for Mars missions, but with Starlink, SpaceX is no stranger to communications.  There's even a dedicated NSF forum thread for setting up a Mars Starlink network (link here (https://forum.nasaspaceflight.com/index.php?topic=48336.0;all)).

As for NASA wanting to throw a monkey wrench to hinder rouge SpaceX Mars missions, I don't see the motivation.
Most of the people at NASA seem to be fans of SpaceX. Part of NASA's mission is to promote commercial space.
Also, NASA is a government agency. As such, they basically do what they're told by Congress. They have little power of their own.

I realize that for some, the idea that NASA wouldn't have a part to play in the first crewed missions may seem like heresy,
but it seems obvious to me that SpaceX has considered this possibility for many years, and I see this reflected in Musk's plans
for power options, e.g. all solar, no nuclear, propellant production after the first crew arrives, etc.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 02/24/2020 11:11 am
The trick is to get NASA involved in the early missions without letting them take over...

NASA can throw a monkey wrench so many different ways and also be helpful in so many ways...

Allow them ~1/3 the seats and cargo space on the first crewed mission...

I think we're getting to the crux of the issue.  If the first Mars crewed missions include NASA astronauts,
I believe that would impact many aspects of the mission architecture, including power options.
For example, if NASA were involved, then nuclear power becomes an option.

Also, every plan I've seen from NASA has the ISRU return propellant ready and waiting before the first crew departs Earth.
By constant, as I've shown before, Musk's plan clearly shows propellant production starting after the first crew arrives.
Since Musk's plan exposes the crew to significantly more risk, I doubt NASA would accept this.

And as you dig into the details, I suspect there are a many other power options would be affected if NASA were involved.

Note: At the ground breaking ceremony for the South Texas launch site, Musk said:
Quote from: Elon Musk
It very well could be the first person to go to another planet could launch from this location
(link here (https://www.texastribune.org/2014/09/22/brownsville-spacex-facility-might-land-first-mars/)).

If the first crew to Mars included NASA astronauts, I believe the mission would launch from Florida, not Texas.
Also note that Elon said this back in 2014. So it appears that SpaceX has seriously considered going "rouge" for quite a while.

With this in mind, let's look at the pros and cons of having NASA astronauts in the first crewed missions.

Obviously, NASA has a lot of experience to offer, but SpaceX could obtain this experience in other ways.
For example, SpaceX could hire NASA's former head of human spaceflight. Note: When you hire a high-level guy like this,
it's not unusual for some of the people who worked under him to move to the new company as well.
So SpaceX may now be in a position to cherry-pick some of the best and brightest minds at NASA.

Some have mentioned the possibility of leveraging NASA's communication network for Mars missions, but with Starlink, SpaceX is no stranger to communications.  There's even a dedicated NSF forum thread for setting up a Mars Starlink network (link here (https://forum.nasaspaceflight.com/index.php?topic=48336.0;all)).

As for NASA wanting to throw a monkey wrench to hinder rouge SpaceX Mars missions, I don't see the motivation.
Most of the people at NASA seem to be fans of SpaceX. Part of NASA's mission is to promote commercial space.
Also, NASA is a government agency. As such, they basically do what they're told by Congress. They have little power of their own.

I realize that for some, the idea that NASA wouldn't have a part to play in the first crewed missions may seem like heresy,
but it seems obvious to me that SpaceX has considered this possibility for many years, and I see this reflected in Musk's plans
for power options, e.g. all solar, no nuclear, propellant production after the first crew arrives, etc.
Perhaps NASA is not so much the issue. SpaceX needs to come to an understanding with the US administration and figure out what can and what can't fly politically.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 02/24/2020 12:29 pm
Perhaps NASA is not so much the issue. SpaceX needs to come to an understanding with the US administration and figure out what can and what can't fly politically.

Yes, but that starts to veer off the topic of this thread.

My point is: If the first Mars crewed missions include NASA astronauts, that may limit the power options available to SpaceX.

For example, NASA may require ISRU return propellant production to be completed before the first crew departs Earth.
NASA may also want SpaceX to use some amount of nuclear power, at least as a backup.
I believe both of these scenarios would delay the first crewed mission by some number of years.
Since Musk wants to get humans to Mars as soon as possible, this may be a reason for SpaceX to exclude NASA from the first crew.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/24/2020 12:48 pm
There's no real basis to the forum's longstanding resistance (pun) to that power method.  Explore the science; be more intellectually aggressive.
I don't want someone with this philosophy designing the colony I live in.
When human lives are on the line, the last thing you want is to be "intellectually aggressive," especially with unknown variables.
Being intellectually aggressive (https://ludwig.guru/s/intellectually+aggressive) is a way to manage unknowns, and make progress.  Healthy.
"Make progress" = "learn stuff" = "make mistakes." I don't want to rely on a bleeding-edge system for survival, I want a nice known (as much as can be) solution. Certainly we should do experiments on such things, but that's no substitute for a nice low-risk system.

This reminds me of the adage: "Good/Cheap/Fast — you can only pick two".  In this case, I'd say Good = Lower Risk.

Of these 3 design factors, it seems clear to me that Musk is prioritizing "Fast".
For example, in a YouTube interview with Garrett Reisman, a former NASA astronaut who now works for SpaceX said:
Quote from: Garrett Reisman
In fact, he (Elon Musk) measures pretty much every major decision by whether or not it brings the day when we have a self-sustainable colony on Mars sooner or later.  That's the prism by which he makes every... Every single decision he makes, he makes it through that prism.

Also, given that SpaceX doesn't have unlimited funds, cost must also be a priority.

So if you believe the adage that you can only pick 2 of the 3 design criteria above,
it shouldn't surprise people if SpaceX's plans for Mars are willing to accept higher levels of risk.

For example, Dr. Zubrin's Mars Direct plan has the ISRU return propellant ready and waiting before any crew leaves Earth.
By contrast, Musk's plan clearly shows propellant production starting after the first crew arrives (see attached slide).

While I agree that SpaceX conops shows greater risk tolerance than NASA conops from the past, the logic used here seems wishy-washy.

We could equally say that Good = High Performance (ie reliable 24.5/7 power, but with a higher associated cost than solar), making this an argument against nuclear.

Title: Re: Power options for a Mars settlement
Post by: Ludus on 02/24/2020 07:41 pm
Getting a reactor as an add on AFTER an all solar (or solar + methalox genset) solution is up and running will be WAY easier. He won't have to grovel, NASA will be trying to stay relevant and a reactor is a way to do that.

Once SpaceX has facts on the ground on Mars or is even close to it, attitudes will change. Their whole approach is radically different from any prior planning. Los Alamos (LANL) designed Kilopower for the traditional few person flags and footprints missions but SpaceX needs a Mars specific version of their Megapower/eVinci reactor that was scaled up for terrestrial use. They’d love to support that once the funding/planning starts to take seriously the idea that there will be that large a presence on Mars.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/24/2020 10:46 pm
The trick is to get NASA involved in the early missions without letting them take over...

NASA can throw a monkey wrench so many different ways and also be helpful in so many ways...

Allow them ~1/3 the seats and cargo space on the first crewed mission...

I think we're getting to the crux of the issue.  If the first Mars crewed missions include NASA astronauts,
I believe that would impact many aspects of the mission architecture, including power options.
For example, if NASA were involved, then nuclear power becomes an option.

Also, every plan I've seen from NASA has the ISRU return propellant ready and waiting before the first crew departs Earth.
By constant, as I've shown before, Musk's plan clearly shows propellant production starting after the first crew arrives.
Since Musk's plan exposes the crew to significantly more risk, I doubt NASA would accept this.

And as you dig into the details, I suspect there are a many other power options would be affected if NASA were involved.

Note: At the ground breaking ceremony for the South Texas launch site, Musk said:
Quote from: Elon Musk
It very well could be the first person to go to another pla Kim net could launch from this location
(link here (https://www.texastribune.org/2014/09/22/brownsville-spacex-facility-might-land-first-mars/)).

If the first crew to Mars included NASA astronauts, I believe the mission would launch from Florida, not Texas.
Also note that Elon said this back in 2014. So it appears that SpaceX has seriously considered going "rouge" for quite a while.

With this in mind, let's look at the pros and cons of having NASA astronauts in the first crewed missions.

Obviously, NASA has a lot of experience to offer, but SpaceX could obtain this experience in other ways.
For example, SpaceX could hire NASA's former head of human spaceflight. Note: When you hire a high-level guy like this,
it's not unusual for some of the people who worked under him to move to the new company as well.
So SpaceX may now be in a position to cherry-pick some of the best and brightest minds at NASA.

Some have mentioned the possibility of leveraging NASA's communication network for Mars missions, but with Starlink, SpaceX is no stranger to communications.  There's even a dedicated NSF forum thread for setting up a Mars Starlink network (link here (https://forum.nasaspaceflight.com/index.php?topic=48336.0;all)).

As for NASA wanting to throw a monkey wrench to hinder rouge SpaceX Mars missions, I don't see the motivation.
Most of the people at NASA seem to be fans of SpaceX. Part of NASA's mission is to promote commercial space.
Also, NASA is a government agency. As such, they basically do what they're told by Congress. They have little power of their own.

I realize that for some, the idea that NASA wouldn't have a part to play in the first crewed missions may seem like heresy,
but it seems obvious to me that SpaceX has considered this possibility for many years, and I see this reflected in Musk's plans
for power options, e.g. all solar, no nuclear, propellant production after the first crew arrives, etc.

The last mission profile made public was boots then ISRU and yes, this is higher risk than NASA would accept. The issue isn't ISRU. The issue is a return ticket in hand. Without going into detail, There are plausible mission profiles with enough props delivered to the surface to make orbit and a tanker on orbit. This would probably satisfy NASA and introduce nothing to ding the timeline.

I don’t have the slightest doubt SX can do mars without NASA. It’s yet another trade space with parameters mushier than engineers like. If including NASA is the cost of nuke power, so be it. I get the willies thinking about undiversified power, especially if it can be done at reasonable cost. Cost being something more complex than just money.

Power is so central to everything that has to happen, even on the first mission, that it can easily become the bottleneck. There are good arguments that PV and batteries both cost and mass less than nuke at any chosen capacity. There is argument that if carefully planned, a base could eke out survival through a decadal dust storm, but ISTM that power is one mission resource where both belt and suspenders are warranted. And a surplus of power is the key resource that allows exploitation of unexpected opportunity.

As Freewheelin Franklin said, “Power will get you through times of no sunlight better than sunlight will get you through times of no power.” Or something like that.

Personal impression only but I see NASA as a (junior) partner having more pros than cons. Nuke power and anchor tenant being at the top of the list. Initially I was opposed but the more I thought about it the better I liked it.

Musk is a driven but supple and flexible guy. He will do whatever it takes to establish a long term presence on mars. If teaming with NASA (on his terms) improves the odds...

BTW, Monkey wrench was probably too hard edged a term. It takes only one aparatchik with an attitude to induce high impedance that not even Congress can overcome easily. Anybody with civil service experience knows how this works.

Phil
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/25/2020 01:58 am
So it appears that SpaceX has seriously considered going "rouge" for quite a while.

I hope that was intentional.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/26/2020 08:47 pm
With dust storms that could last for months, the amount of batteries required to handle this scenario may be much larger than a backup methalox generator.

Again, while the decadal dust storms can last for months, the worst storm conditions do not last months, but an odd day or two here and there.

Power is so central to everything that has to happen, even on the first mission, that it can easily become the bottleneck. There are good arguments that PV and batteries both cost and mass less than nuke at any chosen capacity. There is argument that if carefully planned, a base could eke out survival through a decadal dust storm, but ISTM that power is one mission resource where both belt and suspenders are warranted.

For planning:

Quote

The Fact and Fiction of Martian Dust Storms (https://www.nasa.gov/feature/goddard/the-fact-and-fiction-of-martian-dust-storms)

“Every year there are some moderately big dust storms that pop up on Mars and they cover continent-sized areas and last for weeks at a time,” said Michael Smith, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Beyond Mars’ large annual storms are massive storms that occur more rarely but are much larger and more intense.

“Once every three Mars years (about 5 ½ Earth years), on average, normal storms grow into planet-encircling dust storms, and we usually call those ‘global dust storms’ to distinguish them,” Smith said.

2007 global storm blackout (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1830907#msg1830907) (< 5% light transmission): 

- Spirit:  ~ 3 weeks
- Opportunity:  ~ 4 weeks

See:  Lemmon et al. 2015.

Refs.

Lemmon, M. T., Wolff, M. J., Bell III, J. F., Smith, M. D., Cantor, B. A., & Smith, P. H. (2015). Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. Icarus, 251, 96-111.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/27/2020 01:03 am
low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.

Lunar ISRU PV would need significant refining, too; maybe molten oxide electrolysis (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiT4uvSg-PnAhVjHjQIHXVxBOEQFjABegQIBRAE&url=http%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunarisru2019%2Fpdf%2F5012.pdf&usg=AOvVaw3At_1Ypea9h9HZRAhPeD7P) gives a starting point.  Its liquid metal output could go to a refinery, such as an electrolysis cell.  How might you stage a refinery, to produce e.g. purified silicon for PV?
I can't find the paper right now, but I remember they postulated making cells directly on the ground. No refining. Efficiency was terrible but they didn't care. Basically a robotic device loaded with the necessary trace elements, and connection wire, would sinter lunar regolith that was high silicon content and during the sintering process turn it into low efficiency cells and bond wire to it

Impure PV fiber isn't easily fabricated in situ, but I think it shouldn't require additional active-layer cargo.  Or you're thinking of something else? 

1 (https://www.nature.com/articles/srep06283) 2 (https://mitmrsec.mit.edu/sites/default/files/documents/Recent%20Progress%20and%20Perspectives%20of%20Thermally%20Drawn%20Multimaterial%20Fiber%20Electronics.pdf)
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/27/2020 07:15 am
your TE-power proposal is you taking a micro-scale effect and exaggerating it for a bit of silly fun

NASA paid Ames and gave iTech recognition to Ion Power Group for their Mars facility power research, explicitly.  If someone imagines that was "silly fun", well, that's on him. 

I wonder how many here understand how, for example, Baumgaertner's balloons would work, as in Illustration 9 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048909#msg2048909).  Can you explain that figure plainly yourself, Paul451?
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/29/2020 06:44 am
2007 global storm blackout (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1830907#msg1830907) (< 5% light transmission):
[...]
Lemmon, M. T., Wolff, M. J., Bell III, J. F., Smith, M. D., Cantor, B. A., & Smith, P. H. (2015). Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. Icarus, 251, 96-111.

"Transmission" refers to optical depth, also called Tau, the measure of the inverse_log of direct insolation. The paper explains it in pretty good detail.

For solar power you also need to include indirect insolation, in order to get total insolution. Total insolation is the actual "flat plain" amount of sunlight available to a PV panel. Typically measured in Watts/square_metre, also called flux.

Which you could just read it straight off the very paper you cited. https://arxiv.org/ftp/arxiv/papers/1403/1403.4234.pdf (https://arxiv.org/ftp/arxiv/papers/1403/1403.4234.pdf)

During the global dust storm of Mars-year 28 (2008mid-2007), when Tau reached around 5 at both sites (much less than 1% direct insolation), the total insolation went from the seasonal range of 120-170 Wm-2 down to 50 Wm-2. So a drop of just 2/3rds. Which supports the point I made.

Attached:
Figure 1: Year-on-year optical depth. Y-axis scale cuts off the top of the Year-28 storm, but I included it because it shows the label-key and the whole year.
Figure 2: Year-on-year optical depth. Zooming on a specific season, and increasing the Y-axis to show the Year-28 storm.
Figure 3: Total solar insolation for the same years.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/29/2020 06:47 am
Baumgaertner's balloons [...] as in Illustration 9 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048909#msg2048909).  Can you explain that figure plainly yourself, Paul451?

It's a drawing of a graph, not a graph.

It doesn't actually show real data, not even simulated data. It's just made up. It literally has no scientific basis whatsoever.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/29/2020 06:56 am
NASA paid Ames and gave iTech recognition to Ion Power Group for their Mars facility power research, explicitly.  If someone imagines that was "silly fun", well, that's on him.

iTech is one of NASA's wild-speculation contests. An entry that made the finals in the same year was about mining Helium-3. So yes, it's "silly fun". Nothing like their more serious SBIR contests.

(I'm not objecting. These sillier contests cost NASA very little and they let NASA explore speculative, fringe ideas. 99% will be worthless, but it's the 1% gold in the dirt that moves on to more serious funding contests and perhaps actual tech-development programs.)
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/29/2020 04:22 pm
Again, while the decadal dust storms can last for months, the worst storm conditions do not last months, but an odd day or two here and there.

But no, they're not decadal, and worst conditions don't last a day or two, clearly (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2051211#msg2051211).   We should keep the facts in mind.

During the global dust storm of Mars-year 28 (2008), when Tau reached around 5 at both sites (much less than 1% direct insolation), the total insolation went from the seasonal range of 120-170 Wm-2 down to 50 Wm-2. So a drop of just 2/3rds. Which supports the point I made.

Tau is reported during storms because transmission translates most directly into PV power.  Diffuse light is secondary.  That light is reddened, and it has a low-angle component, so it contributes less PV power per unit flux.

That's why your numbers don't match the reality of e.g. Opportunity's 2007 crisis.  Daily output crashed from 700 Wh to < 130 Wh min requirement, forcing sleep mode.  That wouldn't have happened if storm PV power matched your simple statement. 

Power is the OP.  Calculate power where you can, and check against some references and history, to make sure you're in the ballpark.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/29/2020 04:49 pm
NASA paid Ames and gave iTech recognition to Ion Power Group for their Mars facility power research, explicitly.  If someone imagines that was "silly fun", well, that's on him.

iTech is one of NASA's wild-speculation contests. An entry that made the finals in the same year was about mining Helium-3. So yes, it's "silly fun". Nothing like their more serious SBIR contests.

(I'm not objecting. These sillier contests cost NASA very little and they let NASA explore speculative, fringe ideas. 99% will be worthless, but it's the 1% gold in the dirt that moves on to more serious funding contests and perhaps actual tech-development programs.)

"99% worthless" is your hyperbole.  And notably, you didn't give reason for thinking Baumgaertner's work itself is worthless.  Misdirection.

Here's the actual energy semifinalist list (https://www.powerelectronics.com/technologies/alternative-energy/article/21864159/nasa-selects-top-25-semifinalists-in-energy-competition).  Thread participants might want to explore the new tech.

Quote
NASA iTech is an initiative by NASA’s Space Technology Mission Directorate (STMD) to find innovative ideas that address important problems here on Earth and also hold potential to overcome critical technology hurdles in future space exploration.

NASA has teamed up with the U.S. Department of Energy’s (DOE) Advanced Research Projects Agency‑Energy (ARPA-E) to identify transformational technologies to improve how energy is generated, distributed and stored. These game-changing ideas may come from small or large businesses, academia, and other government organizations that may not have previously had a forum to present their solutions to NASA.

“Making it into the top 25 as a semifinalist for a NASA iTech cycle is no easy feat for the entrepreneurs. The quality and creativity of the proposals we receive to address some of space exploration’s toughest technical objectives are always very impressive, and it’s tough to make the cut,” said Kira Blackwell, NASA iTech program executive for STMD. “This cycle is unique, as it addresses groundbreaking approaches within energy-specific focus areas that could solve important problems here on Earth and in the space community.”

In March, the iTech Challenge issued a call for ideas within energy focus areas such as Fuel Cells and Regenerative Fuel Cells; High-energy-density Batteries and Supercapacitors; Solar Power Systems; Small Fission Power Systems; and Innovative Power Management and Distribution, including Smart Grids and Wireless Power Transfer.


Title: Re: Power options for a Mars settlement
Post by: LMT on 02/29/2020 05:10 pm
Baumgaertner's balloons [...] as in Illustration 9 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048909#msg2048909).  Can you explain that figure plainly yourself, Paul451?

It's a drawing of a graph, not a graph.

It doesn't actually show real data, not even simulated data. It's just made up. It literally has no scientific basis whatsoever.

No, the atmospheric physicist (https://scholar.google.com/citations?user=ZLs1R3sAAAAJ&hl=en&oi=sra) isn't making things up here.  ::) 

The paper (https://ionpowergroup.com/wp-content/uploads/2016/07/MARS-REPORT-Power-to-Mars-FINAL.pdf) gives some background science, and I noted some more (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850474#msg1850474).  You might highlight some updates; that would be useful.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 02/29/2020 06:13 pm
Baumgaertner's balloons [...] as in Illustration 9 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048909#msg2048909).  Can you explain that figure plainly yourself, Paul451?

It's a drawing of a graph, not a graph.

It doesn't actually show real data, not even simulated data. It's just made up. It literally has no scientific basis whatsoever.

No, the atmospheric physicist (https://scholar.google.com/citations?user=ZLs1R3sAAAAJ&hl=en&oi=sra) isn't making things up here.  ::) 

The paper (http://www.academia.edu/download/57265698/Power-to-Mars.v08_updateJuly2018.pdf) gives some background science, and I noted some more (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850474#msg1850474).  You might highlight some updates; that would be useful.
Can you explain what the graph in question means by "With simulated noise"?
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/29/2020 06:34 pm
Baumgaertner's balloons [...] as in Illustration 9 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048909#msg2048909).  Can you explain that figure plainly yourself, Paul451?

It's a drawing of a graph, not a graph.

It doesn't actually show real data, not even simulated data. It's just made up. It literally has no scientific basis whatsoever.

No, the atmospheric physicist (https://scholar.google.com/citations?user=ZLs1R3sAAAAJ&hl=en&oi=sra) isn't making things up here.  ::) 

The paper (http://www.academia.edu/download/57265698/Power-to-Mars.v08_updateJuly2018.pdf) gives some background science, and I noted some more (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850474#msg1850474).  You might highlight some updates; that would be useful.
Can you explain what the graph in question means by "With simulated noise"?

He didn't cite, but it looks like typical DC output noise (https://pv-magazine-usa.com/2019/09/05/recognizing-and-combating-power-quality-issues-in-solar-power-systems/).
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 02/29/2020 06:58 pm
The noise is an example of possible output. Window dressing for the idea, nothing more.

Edit: before anyone gets tetchy with me, I am offering an explanation, that's it.
Title: Re: Power options for a Mars settlement
Post by: oiorionsbelt on 02/29/2020 07:03 pm
The noise is an example of possible output. Window dressing for the idea, nothing more.

I thought you were addressing the thread. :)
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/29/2020 07:08 pm
The noise is an example of possible output. Window dressing for the idea, nothing more.

Edit: before anyone gets tetchy with me, I am offering an explanation, that's it.

Well, you'd think his experience with DC systems would give him reason for scaling the noise as he did. 

But as for the "idea", do you think you've got a read on where the figure's power is coming from?  There's a lot of "noise" in thread; it's not obvious participants understand.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/29/2020 08:53 pm
Tau is reported during storms because transmission translates most directly into PV power.

Incorrect. Even your own claimed figures show a reduction to 20%, not a reduction to <2% as would be expected by Tau=4, or <1% as would be expected by Tau=5.

So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%.

That wouldn't have happened if storm PV power matched your simple statement.
Power is the OP.  Calculate power where you can, and check against some references and history, to make sure you're in the ballpark.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/29/2020 09:03 pm
The noise is an example of possible output. Window dressing for the idea, nothing more.

That was my point. Baumgaertner doesn't have actual figures. Not even a simulation. His graph is a drawing to show visually how his concept might work if his non-existent device works as he supposes. TRL=0.

I'm not criticising Baumgaertner for that, it's clearly all he intended and he would expect a reasonable person to understand that. I'm criticising LMT for referring to it as if it is some kind of actual data, demanding that others "explain his figures", with all the associated appeal to authority.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/29/2020 10:01 pm
The noise is an example of possible output. Window dressing for the idea, nothing more.

That was my point. Baumgaertner doesn't have actual figures. Not even a simulation. His graph is a drawing to show visually how his concept might work if his non-existent device works as he supposes. TRL=0.

I'm not criticising Baumgaertner for that, it's clearly all he intended and he would expect a reasonable person to understand that. I'm criticising LMT for referring to it as if it is some kind of actual data, demanding that others "explain his figures", with all the associated appeal to authority.

He explains Illustration 9 in Section 3, and summarizes GEC modeling in Section 5. 

Also, the "TRL-0" assertion is incorrect (https://www.nasa.gov/sites/default/files/trl.png).  One can judge actual TRL from the patents (https://ionpowergroup.com/patents/), etc.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/29/2020 10:06 pm
Tau is reported during storms because transmission translates most directly into PV power.

Incorrect. Even your own claimed figures show a reduction to 20%, not a reduction to <2% as would be expected by Tau=4, or <1% as would be expected by Tau=5.

So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%.

What I said (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512) is correct.  It shows why you can't reconcile your statement with the actual 2007 power numbers.
Title: Re: Power options for a Mars settlement
Post by: Eka on 03/01/2020 02:47 am
Baumgaertner's balloons [...] as in Illustration 9 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048909#msg2048909).  Can you explain that figure plainly yourself, Paul451?

It's a drawing of a graph, not a graph.

It doesn't actually show real data, not even simulated data. It's just made up. It literally has no scientific basis whatsoever.

No, the atmospheric physicist (https://scholar.google.com/citations?user=ZLs1R3sAAAAJ&hl=en&oi=sra) isn't making things up here.  ::) 

The paper (http://www.academia.edu/download/57265698/Power-to-Mars.v08_updateJuly2018.pdf) gives some background science, and I noted some more (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1850474#msg1850474).  You might highlight some updates; that would be useful.
Can you explain what the graph in question means by "With simulated noise"?
Solar output during the day varies minute to minute as the sun light reaching the solar panels varies. This is because of variations in the atmosphere. Yes, it may look cloudless and consistent to you, but it changes. It isn't a nice smooth curve.
Title: Re: Power options for a Mars settlement
Post by: Lar on 03/01/2020 02:58 am
low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.

Lunar ISRU PV would need significant refining, too; maybe molten oxide electrolysis (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiT4uvSg-PnAhVjHjQIHXVxBOEQFjABegQIBRAE&url=http%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunarisru2019%2Fpdf%2F5012.pdf&usg=AOvVaw3At_1Ypea9h9HZRAhPeD7P) gives a starting point.  Its liquid metal output could go to a refinery, such as an electrolysis cell.  How might you stage a refinery, to produce e.g. purified silicon for PV?
I can't find the paper right now, but I remember they postulated making cells directly on the ground. No refining. Efficiency was terrible but they didn't care. Basically a robotic device loaded with the necessary trace elements, and connection wire, would sinter lunar regolith that was high silicon content and during the sintering process turn it into low efficiency cells and bond wire to it

Impure PV fiber isn't easily fabricated in situ, but I think it shouldn't require additional active-layer cargo.  Or you're thinking of something else? 

1 (https://www.nature.com/articles/srep06283) 2 (https://mitmrsec.mit.edu/sites/default/files/documents/Recent%20Progress%20and%20Perspectives%20of%20Thermally%20Drawn%20Multimaterial%20Fiber%20Electronics.pdf)

Not thinking of fiber either. You're overcomplexifying, The idea Spudis et al referred to was akin to sintering, Rather than forming wafers, the surface is glassified, then a second pass etches and dopes as needed. Right there on graded ground.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 03/01/2020 03:09 am
low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.

Lunar ISRU PV would need significant refining, too; maybe molten oxide electrolysis (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiT4uvSg-PnAhVjHjQIHXVxBOEQFjABegQIBRAE&url=http%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunarisru2019%2Fpdf%2F5012.pdf&usg=AOvVaw3At_1Ypea9h9HZRAhPeD7P) gives a starting point.  Its liquid metal output could go to a refinery, such as an electrolysis cell.  How might you stage a refinery, to produce e.g. purified silicon for PV?
I can't find the paper right now, but I remember they postulated making cells directly on the ground. No refining. Efficiency was terrible but they didn't care. Basically a robotic device loaded with the necessary trace elements, and connection wire, would sinter lunar regolith that was high silicon content and during the sintering process turn it into low efficiency cells and bond wire to it

Impure PV fiber isn't easily fabricated in situ, but I think it shouldn't require additional active-layer cargo.  Or you're thinking of something else? 

1 (https://www.nature.com/articles/srep06283) 2 (https://mitmrsec.mit.edu/sites/default/files/documents/Recent%20Progress%20and%20Perspectives%20of%20Thermally%20Drawn%20Multimaterial%20Fiber%20Electronics.pdf)

Not thinking of fiber either. You're overcomplexifying, The idea Spudis et al referred to was akin to sintering, Rather than forming wafers, the surface is glassified, then a second pass etches and dopes as needed. Right there on graded ground.
That definitely won't work.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 03/01/2020 04:02 am
Tau is reported during storms because transmission translates most directly into PV power.

Incorrect. Even your own claimed figures show a reduction to 20%, not a reduction to <2% as would be expected by Tau=4, or <1% as would be expected by Tau=5.

So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%.

What I said (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512) is correct.  It shows why you can't reconcile your statement with the actual 2007 power numbers.

What you said was correct, except the part where you said "transmission translates most directly into PV power." That was the statement Paul451 was responding to. Neither horizontal flux nor beam irradiance (aka transmission) perfectly match the PV output, but the horizontal flux is closer.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/01/2020 04:23 am
Again, while the decadal dust storms [...]
But no, they're not decadal

Since 1873 there have been 12 global dust storms, treating 1977 as two separate storms. (McKim (2008) and adding 2018.) Regional dust storms occur with a 1/3 annual frequency. Local storms occur in several locations each year and are the reason the Mars year tends to divide into ~12 months of good skies and ~12 months of reduced clarity.

We should keep the facts in mind.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/01/2020 04:31 am
Tau is reported during storms because transmission translates most directly into PV power.
What you said was correct, except the part where you said "transmission translates most directly into PV power."

What part did he say that was correct?

"Tau is reported during storms because [claim]" is also wrong. They report daily Tau from every platform[**], whether there's a storm or not, whether the platform is solar or nuclear-powered, because it's a standard observation they've been making since the Viking landers. (Possibly earlier, but I can't find any Mariner refs.) They don't only report it during storms and they don't report it "because" of its application to PV power.

** [Edit: Technically, Odyssey and Maven can't report Tau, they "contribute". Whatever that means.]
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/01/2020 04:41 am
Baumgaertner doesn't have actual figures. Not even a simulation. His graph is a drawing to show visually how his concept might work if his non-existent device works as he supposes. TRL=0.
Also, the "TRL-0" assertion is incorrect (https://www.nasa.gov/sites/default/files/trl.png).

TRL-1 requires "basic principles observed and reported". As has been noted before, Baumgaertner's concept requires that the TE effect due to Mars airborne dust is three-orders-of-magnitude higher than seen on Earth. Something you have previously admitted has not been observed.

So "less than TRL-1".
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 03/01/2020 04:49 am
Tau is reported during storms because transmission translates most directly into PV power.
What you said was correct, except the part where you said "transmission translates most directly into PV power."

What part did he say that was correct?

Everything he wrote after that sentence is 100% correct (cue the "challenge accepted!" :D).

"Tau is reported during storms because [claim]" is also wrong. They report daily Tau from every platform, whether there's a storm or not, whether the platform is solar or nuclear-powered, because it's a standard observation they've been making since the Viking landers. (Possibly earlier, but I can't find any Mariner refs.) They don't only report it during storms and they don't report it "because" of its application to PV power.

Yep, I noticed that. I chose not to point it out because A) I was being nice and trying not to pile on, and B) it didn't have much relevance to the actual topic. But hey, you do you.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/01/2020 05:09 am
cue the "challenge accepted!"

Don't tempt me.

I was being nice

I've heard of that, it seems overrated.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 03/01/2020 05:24 am
I was being nice

I've heard of that, it seems overrated.

Then I'll remember not to waste any on you in the future. :D You're not the only one here who can deliver merciless hypercorrections to any tiny error or imprecision. :P

Anyway, we've drifted way off-topic. Back to power options please.

Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/01/2020 02:51 pm
...
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/01/2020 03:00 pm
low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.

Lunar ISRU PV would need significant refining, too; maybe molten oxide electrolysis (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiT4uvSg-PnAhVjHjQIHXVxBOEQFjABegQIBRAE&url=http%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunarisru2019%2Fpdf%2F5012.pdf&usg=AOvVaw3At_1Ypea9h9HZRAhPeD7P) gives a starting point.  Its liquid metal output could go to a refinery, such as an electrolysis cell.  How might you stage a refinery, to produce e.g. purified silicon for PV?
I can't find the paper right now, but I remember they postulated making cells directly on the ground. No refining. Efficiency was terrible but they didn't care. Basically a robotic device loaded with the necessary trace elements, and connection wire, would sinter lunar regolith that was high silicon content and during the sintering process turn it into low efficiency cells and bond wire to it

Impure PV fiber isn't easily fabricated in situ, but I think it shouldn't require additional active-layer cargo.  Or you're thinking of something else? 

1 (https://www.nature.com/articles/srep06283) 2 (https://mitmrsec.mit.edu/sites/default/files/documents/Recent%20Progress%20and%20Perspectives%20of%20Thermally%20Drawn%20Multimaterial%20Fiber%20Electronics.pdf)

Not thinking of fiber either. You're overcomplexifying, The idea Spudis et al referred to was akin to sintering, Rather than forming wafers, the surface is glassified, then a second pass etches and dopes as needed. Right there on graded ground.
That definitely won't work.

My opinion: ISRU propellant makes sense, but I suspect making solar cells on Mars won't happen for a while.
Here's a quote from Elon Musk just 2 days ago saying:
Quote from: Elon Musk 2020-02-28
We sit on top of a massive base of infrastructure. The economy is... You can think of all the things that are mined and then refined, and then many steps in the refinement. In order to produce your phone, or your toaster even, there's a vast base of industry that's required to produce even a simple household item. It's very difficult.


However, assembling things on Mars is a different matter.
For example, they could ship solar cells from Earth and assemble them into panels.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/02/2020 03:19 am
low efficiency panels might well be created out of entirely lunar ISRU materials (except for trace elements), as Spudis et al researched. But not necessarily out of martian without siginficant refining.

Lunar ISRU PV would need significant refining, too; maybe molten oxide electrolysis (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiT4uvSg-PnAhVjHjQIHXVxBOEQFjABegQIBRAE&url=http%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunarisru2019%2Fpdf%2F5012.pdf&usg=AOvVaw3At_1Ypea9h9HZRAhPeD7P) gives a starting point.  Its liquid metal output could go to a refinery, such as an electrolysis cell.  How might you stage a refinery, to produce e.g. purified silicon for PV?
I can't find the paper right now, but I remember they postulated making cells directly on the ground. No refining. Efficiency was terrible but they didn't care. Basically a robotic device loaded with the necessary trace elements, and connection wire, would sinter lunar regolith that was high silicon content and during the sintering process turn it into low efficiency cells and bond wire to it

Impure PV fiber isn't easily fabricated in situ, but I think it shouldn't require additional active-layer cargo.  Or you're thinking of something else? 

1 (https://www.nature.com/articles/srep06283) 2 (https://mitmrsec.mit.edu/sites/default/files/documents/Recent%20Progress%20and%20Perspectives%20of%20Thermally%20Drawn%20Multimaterial%20Fiber%20Electronics.pdf)

Not thinking of fiber either. You're overcomplexifying, The idea Spudis et al referred to was akin to sintering, Rather than forming wafers, the surface is glassified, then a second pass etches and dopes as needed. Right there on graded ground.
That definitely won't work.

Hmm.  I'd like to see an actual paper.

Solar cell silicon has ~ 1 ppm impurity.  Much more than that, and resistance spikes, rendering the silicon useless for PV.  E.g., Hopkins 1985.

The useful doping impurities are typically boron and phosphorous, and they're useful only if the bulk impurities are removed first.

In PV fibers, impure silicon is used, but even that technically low-purity silicon is 99.98% pure.  Moreover, the fiber draw segregates impurities:  even very poor PV performance requires this.

Refs.

Hopkins, R.H., 1985. Impurities in silicon solar cells.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/02/2020 04:39 pm
Tau is reported during storms because transmission translates most directly into PV power.

Incorrect. Even your own claimed figures show a reduction to 20%, not a reduction to <2% as would be expected by Tau=4, or <1% as would be expected by Tau=5.

So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%.

What I said (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512) is correct.  It shows why you can't reconcile your statement with the actual 2007 power numbers.

What you said was correct, except the part where you said "transmission translates most directly into PV power." That was the statement Paul451 was responding to. Neither horizontal flux nor beam irradiance (aka transmission) perfectly match the PV output, but the horizontal flux is closer.

130 Wh min

Transmission is the #1 factor, which is why it's reported, and why you didn't show otherwise.

You two might work together, as an exercise:

You're both ignoring the fact that power dropped far more than you imagine during the 2007 Opportunity crisis.  I explained (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512), but it's easy to see that Paul's imagined < 2/3 drop would have avoided the well-known, well-understood crisis.  So you might rethink Mars PV power, together, and give reasoning that matches the historical fact.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/02/2020 05:07 pm
Again, while the decadal dust storms [...]
But no, they're not decadal

Since 1873 there have been 12 global dust storms, treating 1977 as two separate storms. (McKim (2008) and adding 2018.) Regional dust storms occur with a 1/3 annual frequency. Local storms occur in several locations each year and are the reason the Mars year tends to divide into ~12 months of good skies and ~12 months of reduced clarity.

We should keep the facts in mind.

No, your statement was just incorrect.  It's not true that "decadal dust storms can last for months," and "the worst storm conditions [last] an odd day or two."  Any global dust storm can last for months, and these storms occur about every 5.5 years.  And of course the worst conditions don't last "an odd day or two".   Mars power options must square with the facts there.

Also, you didn't actually give a reference.  If you do, check especially for all storms (global or regional) that lasted more than a month.  I'm not sure, but you might find that some regions encounter month+ storms more frequently than every 5.5 years.  Regional tallies would be useful.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/02/2020 07:08 pm
Baumgaertner doesn't have actual figures. Not even a simulation. His graph is a drawing to show visually how his concept might work if his non-existent device works as he supposes. TRL=0.
Also, the "TRL-0" assertion is incorrect (https://www.nasa.gov/sites/default/files/trl.png).

TRL-1 requires "basic principles observed and reported". As has been noted before, Baumgaertner's concept requires that the TE effect due to Mars airborne dust is three-orders-of-magnitude higher than seen on Earth. Something you have previously admitted has not been observed.

So "less than TRL-1".

That's not how TRL is judged, obviously.  Likewise, you can't say there's "no simulation", and "no scientific basis whatsoever" behind the paper, patents, tested devices, etc.  All untrue.

Comparison:  Posters might judge the TRL and "scientific basis" of this related device (http://www-mars.lmd.jussieu.fr/granada2017/abstracts/montmessin_granada2017.pdf).
Title: Re: Power options for a Mars settlement
Post by: spacenut on 03/02/2020 07:30 pm
One I think nuclear power is a must to get started ASAP is because massive amounts of power are needed to mine and smelt metals.  Metal mining and smelting is the foundation of modern society.  Right behind agriculture.  Iron, copper, lead, zinc, tin, bauxite, nickel, chromium are all needed for anything modern to be made, including microchips.

Second, if there is no oil or coal on Mars, carbon based products, plastics and such will have to be made via power starting with the sabatier process for making methane.  From methane using abundant power you can chain the methane molecules to make other hydrocarbons.  These can also be made from sawdust if trees are grown for fruit and nuts, and later for wood products such as simple toilet paper. 

Then you have the chemical industry that has to get started.  Everything from drugs, cleaners, ammonia and nitrates agriculture etc.

Earth's power production started with hydroelectric generation as well as steam generation with old fashioned steam engines.  No coal or plentiful hydrocarbons eliminates the steam generation process.  No rivers eliminates the hydroelectric production.  That only leaves solar and nuclear.  Even sabatier methane has to have power so that is eliminated except for emergencies.  Start with solar then ASAP bring in nuclear.

Mars will never get independent of earth without massive amounts of power that solar/batteries alone cannot give. 
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/02/2020 11:32 pm
[...]
Tau is reported during storms because transmission translates most directly into PV power.
Incorrect. Even your own claimed figures show a reduction to 20%, not a reduction to <2% as would be expected by Tau=4, or <1% as would be expected by Tau=5.
So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%.
[...]
130 Wh min
Transmission is the #1 factor, which is why it's reported, and why you didn't show otherwise.

I already did, you even quoted it above. Using your own supplied (if uncited) figures combined with the figures from the paper you did cite, show that total insolation is highly predictive of PV power levels, while direct beam insolation (what you call "transmission") is not. Since that's what I've been saying all along, you proved my point.

A Mars base would have gotten through the 2007 global storm without any risk. PV production would have dropped to 20% of normal levels, but if you suspend ISRU propellant production, that would have left sufficient capacity for the rest of the habitat activities to be at comfortable power levels.

The 2018 storm would have been worse. PV power dropping to 10% or so, with individual days dropping to single digit percentages. But the Martians still would have survived without any extreme emergency power saving measures. And for most of the storm period, would have had sufficient power to conduct EVAs, maintenance, etc.



Again, while the decadal dust storms [...]
But no, they're not decadal
Since 1873 there have been 12 global dust storms, treating 1977 as two separate storms. (McKim (2008) and adding 2018.)
No, your statement was just incorrect.  It's not true that "decadal dust storms can last for months," and "the worst storm conditions [last] an odd day or two."  Any global dust storm can last for months, and these storms occur about every 5.5 years.  And of course the worst conditions don't last "an odd day or two".
[...]
Also, you didn't actually give a reference.

Well, one of us didn't.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/02/2020 11:55 pm
Baumgaertner doesn't have actual figures. Not even a simulation. His graph is a drawing to show visually how his concept might work if his non-existent device works as he supposes. TRL=0.
Also, the "TRL-0" assertion is incorrect (https://www.nasa.gov/sites/default/files/trl.png).
TRL-1 requires "basic principles observed and reported" [...]
That's not how TRL is judged, obviously.

{laughs} The bit in the quote-marks is taken directly from the NASA image you linked to.

Do you actually read the things you link to?

Likewise, you can't say there's "no simulation", and "no scientific basis whatsoever" behind the paper, patents, tested devices, etc.  All untrue.
Comparison:  Posters might judge the TRL and "scientific basis" of this related device (http://www-mars.lmd.jussieu.fr/granada2017/abstracts/montmessin_granada2017.pdf).

The linked paper (and the image) is for a small E-field sensor that was meant to be carried aboard a failed lander. (Something similar will fly on future missions.) It is not a triboelectric generator. The existence of a sensor does not validate the concept of TE-generation as a viable power source on Mars. The graphed data in the paper, relating to field testing (no-pun-intended) on Earth also clearly makes nonsense of the constant flat power-curve in the fake Baumgaertner graph you linked to earlier.

If you actually read any of this stuff, instead of trying to shotgun anything that you can at critics in the hope that something sticks, you might understand why these ideas are criticised.

[edit: typo]
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/03/2020 12:13 am
One I think nuclear power is a must to get started ASAP is because massive amounts of power are needed to mine and smelt metals.
[...]
That only leaves solar and nuclear.
[...]
Start with solar then ASAP bring in nuclear.
[...]
Mars will never get independent of earth without massive amounts of power that solar/batteries alone cannot give.

You went from "Mars needs lots of power" with lots of examples and reasoning, to "Only solar and nukes are options" with plenty of justification, and then "Solar isn't enough" with zero justification. I don't see how nuclear is automatically so vastly superior. It has a higher power density, obviously, but when you look at they cost/mass/complexity/etc, I'm not seeing the supposed huge advantage.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 03/03/2020 06:34 am
One I think nuclear power is a must to get started ASAP is because massive amounts of power are needed to mine and smelt metals.
[...]
That only leaves solar and nuclear.
[...]
Start with solar then ASAP bring in nuclear.
[...]
Mars will never get independent of earth without massive amounts of power that solar/batteries alone cannot give.

You went from "Mars needs lots of power" with lots of examples and reasoning, to "Only solar and nukes are options" with plenty of justification, and then "Solar isn't enough" with zero justification. I don't see how nuclear is automatically so vastly superior. It has a higher power density, obviously, but when you look at they cost/mass/complexity/etc, I'm not seeing the supposed huge advantage.
Indeed.

For ongoing build out of a settlement metal processing is going to have be possible. Without coal, oil or natural gas you're kind of stuffed.  It's either concentrated solar (which does exist on earth and is capable of 2000c+ temperatures with sufficiently big mirrors) or high temperature nuclear.

Nuclear for "process heat" has been talked about since the 70's. I think the Russians have some on shore desalination plants run on nuclear heat but that's about it.  Most actual power reactors are PWR or BWR's at about 300c, totally inadequate for melting ore or a lot of other tasks unless you build a power plant and run electric furnaces (which complicates your supply chain still further).

For large scale metal working you're talking the kind of power levels of an NTR engine essentially. GW, not MW.  :(

For near term viable nuclear power generation you're looking at Kilopower units in the 10-100Kw range, possibly as a cluster. 

That's the only real near term nuclear system that stands a chance of being available in time to be useful.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 03/03/2020 12:50 pm
Here in Quebec, we use hydro almost exclusively, for a population of 8 million people and an industrial base that includes aluminium smelters and electric arc furnaces for iron production.  These were implanted here because the electrical power is cheaper here.  Hydro is just a form of solar, but with a better daily range and no night time power dip.  If the rains ever stopped, we would be 'kaput'.  But the rains do not fail, just like the sun doesn't fail. 
Solar photoelectric infrastructure is totally capable of supporting heavy industry, as long as there is investment in some form of storage or some adaptation of the industrial processes to smooth out the peaks.

Quebec closed down its only nuclear reactor power station because it was not economical to run.  Hydro-Quebec pays a few hundred million dollars per year for a peaking gas plant that has never been used, just in case.

And we have winters as well.  A fair percentage of heating power in winter is natural gas.  Because natural gas is so absurdly cheap and burning it for heat is much more efficient than burning it for electricity.

In the long run, most industrial energy on Mars will be used to produce food.  This is already the case on Earth, we just don't need to pay for the sun most of the time :-)  Our cities are all surrounded by gigantic low efficiency solar converter fields, that in the case of Quebec spend a good part of the year under a thick layer of snow.  We just don't produce food in winter, and plants survive overnight, even if the temperatures dips down by 10C or more every night.

Title: Re: Power options for a Mars settlement
Post by: spacenut on 03/03/2020 09:38 pm
I still do not see solar power as a long term solution with dust storms, extensive battery storage for night use, etc.  With nuclear power you can run smelters 24-7.  Shut down and start up of metal smelting is energy wasteful and time consuming.  Otherwise you are going to have acres and acres of solar power panels to maintain, and if you use mirrors to smelt metal, it can only be done in daytime for a few hours.  Then, there is dust storms again to have to deal with. 

Another thing you mentioned is agriculture.  Mars doesn't have millions of square miles of arable land.  All plants are will have to be inside in giant greenhouses.  That is going to take a lot of power.  Then there is return rocket fuel for rockets returning to earth. 

It is going to take GW of power to establish a permanent self sufficient colony, and I just don't see it being solar.  Nuclear is going to have to be factored in.  This is where NASA and the US government will have to chip in and help with.  Too much red tape for SpaceX to deal with. 
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/03/2020 09:52 pm
[ list of things that need power]
It is going to take GW of power to establish a permanent self sufficient colony, and I just don't see it being solar.  Nuclear is going to have to be factored in.

You did it again.

You provided a list of things that will need a lot of power, and then just declared that only nuclear can do it.

"Acres of solar power"? So what? It's not like we are cutting down forests to install them. Thin film pegged to wire-risers over open ground.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/03/2020 10:03 pm
And just to contradict myself, there is one advantage to nukes, which arises from a problem of operating large nuclear reactors on Mars.

On Earth, reactors need access to water for the cooling systems. Without that, you are reliant on convection/radiation. On Mars, the amount of convection depends on wind-speed. 5m/s wind-speed will provide as much cooling as you get from radiation. (5m/s is the average wind-speed on Mars, although it's highly variable.)

So large reactors on Mars will need "acres" of radiators, with complex plumbing and control systems to circulate hot fluid from the turbines to Mars' atmosphere.

Or you could dump it into ice. To the point where the amount of melt-water will vastly exceed any demand from agriculture, industry and propellant production.

Not simple, especially if you don't want to lose the water. It still requires lots of plumbing and control systems, plus careful engineering to prevent any melt-water cavity from collapsing. But it would be interesting.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 03/04/2020 02:37 am
I still do not see solar power as a long term solution with dust storms, extensive battery storage for night use, etc.  With nuclear power you can run smelters 24-7.  Shut down and start up of metal smelting is energy wasteful and time consuming.  Otherwise you are going to have acres and acres of solar power panels to maintain, and if you use mirrors to smelt metal, it can only be done in daytime for a few hours.  Then, there is dust storms again to have to deal with. 

Another thing you mentioned is agriculture.  Mars doesn't have millions of square miles of arable land.  All plants are will have to be inside in giant greenhouses.  That is going to take a lot of power.  Then there is return rocket fuel for rockets returning to earth. 

It is going to take GW of power to establish a permanent self sufficient colony, and I just don't see it being solar.  Nuclear is going to have to be factored in.  This is where NASA and the US government will have to chip in and help with.  Too much red tape for SpaceX to deal with.
Let's try to put production numbers into perspective:

On Earth, at this time:
We produce about 250 kg of steel per person.  Steel requires about 35 MJ/kg for  finished product
We produce about 1000 kg of concrete per person.  Concrete requires about 2 MJ/kg.
We produce about 1000 kg of food per person.  Food requires about 1500 MJ/kg.

So food production requires about 750 times more power than concrete, and 160 times more power than steel production.

Concrete and steel will be marginal productions, from the point of view of power.  They barely register.  So they cannot in any way justify the requirement for nuclear power on Mars.  No matter how many GW are required for steel and concrete, hundred of times more GW are required for food (and biomass).

Food is perfectly adapted to solar cycles because of a few billion years of evolution.  So solar is by far the most logical choice.





Title: Re: Power options for a Mars settlement
Post by: lamontagne on 03/04/2020 02:57 am
The US is 9.8 million km square.  It has about 18% arable land, so about 1,76 millions of square km of food producing land.

This area receives about 1000 W/m2 from the sun.  So the solar input for food production in the US is about 1 760 000 GW.
The electrical production of the US is about 1000 GW of power.  So more than 1000 times less than what is required for food.

This is enough to feed 350 million people.  And comes out to about 0,005 GW per person.  So if agriculture was no more efficient on Mars than on the Earth a 1 million people colony would require 5000 GW of power to grow food.  And food production would cover about 5000 m2 per person, or half an hectare.

Food requires a lot more energy than we usually think it does.  Everything else is marginal.
Title: Re: Power options for a Mars settlement
Post by: Lar on 03/04/2020 03:16 am

Not thinking of fiber either. You're overcomplexifying, The idea Spudis et al referred to was akin to sintering, Rather than forming wafers, the surface is glassified, then a second pass etches and dopes as needed. Right there on graded ground.
That definitely won't work.

This is an old paper and it's entirely possible that the authors are confused. But they seemed to think it would work.

https://www.newscientist.com/article/dn6892-lunar-colony-to-run-on-moon-dust-and-robots/

I missed that they are suggesting there would be some refining by these mobile solar cell creating rovers, though.

Also this is using lunar materials, not Martian.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/04/2020 03:56 am
The US is 9.8 million km square.  It has about 18% arable land, so about 1,76 millions of square km of food producing land.
This area receives about 1000 W/m2 from the sun. [...]

You can't calculate the energy required for food production using just area x flux. Open-air agriculture is stupidly inefficient at converting sunlight into food. We don't care too much, because the sunlight is free. To get a meaningful number, you have to look at situations where the growers do care. Indoor farming and related areas like hydro-MJ. (I can't find any kg/GJ numbers, but indoor farming supposedly gets 10-15 times the productivity per unit area. With some claiming 100-fold.)
Title: Re: Power options for a Mars settlement
Post by: spacenut on 03/04/2020 04:32 am
Many of the newer reactor designs do no need as much or any water for cooling.  If properly designed they can use all the heat for power production.  Thorium and pebble bed reactors would be great on Mars.  I do not see what so many have against nuclear power.  The sun doesn't shine at night, and with dust storms, low power production can put a strain on a colony for survival.  Nuclear can run 24/7.  Nukes can also help warm Mars which is what people want for terra forming.  Thin film solar rolls could be blown to bits if high winds happen on Mars.  Surface scratches from dust storms will degrade solar faster than on earth which has rain water. 

Lots of things to consider.  Like I said, the only two real choices on Mars are solar and nuclear.  One showed how much power it took to make what the average person needed for steel.  What about aluminum, copper, brass, tin, etc.  What about recharging the electric earth moving equipment, cranes, forklifts, trains or rovers.  It would be nice to charge them at night instead of only the daytime.  Most outside work would be done in the daytime when the sun shines.  This equipment will have to be charged at night.  The weight for battery banks large enough to supply nighttime power alone would probably weigh more than a nuke power plant.  All would have to be brought from earth unless rare earth minerals are found on Mars to make them on Mars. 

Nuclear power plants could be buried for safety.  What if a Starship crashed on a solar power field, knocking out a lot of power for the colony.  It could be a game changer.  Also Mars seems to get a lot of asteroid or meteor hits where the earths atmosphere burns them up.  A meteor shower could also knock out a solar field.  Mars is closer to the asteroid belt too.  Our moon helps pull in a lot of meteors that might have hit the earth.  Mars has no large moon. 

There are a lot of reasons for nuclear back up power.  Nuclear power plants are shut down for maintenance in my state during the spring or fall when power use is down.  Coal, hydro, and natural gas take up the slack when nukes are down and vice versa coal and natural gas are down for maintenance when nukes are running.  Sometimes we have droughts and hydro is down.  When dust storms happen and a meteor shower happens, what will be the backup? 

I still think there should be more than one source of power.  Mars is and will be remote from earth, and having redundancy is a must for everything done on Mars.   

Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 03/04/2020 05:23 am
The US is 9.8 million km square.  It has about 18% arable land, so about 1,76 millions of square km of food producing land.

This area receives about 1000 W/m2 from the sun.  So the solar input for food production in the US is about 1 760 000 GW.
The electrical production of the US is about 1000 GW of power.  So more than 1000 times less than what is required for food.

This is enough to feed 350 million people.  And comes out to about 0,005 GW per person.  So if agriculture was no more efficient on Mars than on the Earth a 1 million people colony would require 5000 GW of power to grow food.  And food production would cover about 5000 m2 per person, or half an hectare.

Food requires a lot more energy than we usually think it does.  Everything else is marginal.

5000 GW of power to feed 1 million? That's off by at least a factor of 10. For a start the sun doesn't shine at night.
 
But still. At those scales, orbital mirrors and hectares of transparent greenhouses start to seem like options.

We keep thinking of the colony in terms of thousands, but its goal is millions. That changes things.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 03/04/2020 11:32 am
Many of the newer reactor designs do no need as much or any water for cooling.  If properly designed they can use all the heat for power production.  Thorium and pebble bed reactors would be great on Mars.  I do not see what so many have against nuclear power.  The sun doesn't shine at night, and with dust storms, low power production can put a strain on a colony for survival.  Nuclear can run 24/7.  Nukes can also help warm Mars which is what people want for terra forming.  Thin film solar rolls could be blown to bits if high winds happen on Mars.  Surface scratches from dust storms will degrade solar faster than on earth which has rain water. 

Lots of things to consider.  Like I said, the only two real choices on Mars are solar and nuclear.  One showed how much power it took to make what the average person needed for steel.  What about aluminum, copper, brass, tin, etc.  What about recharging the electric earth moving equipment, cranes, forklifts, trains or rovers.  It would be nice to charge them at night instead of only the daytime.  Most outside work would be done in the daytime when the sun shines.  This equipment will have to be charged at night.  The weight for battery banks large enough to supply nighttime power alone would probably weigh more than a nuke power plant.  All would have to be brought from earth unless rare earth minerals are found on Mars to make them on Mars. 

Nuclear power plants could be buried for safety.  What if a Starship crashed on a solar power field, knocking out a lot of power for the colony.  It could be a game changer.  Also Mars seems to get a lot of asteroid or meteor hits where the earths atmosphere burns them up.  A meteor shower could also knock out a solar field.  Mars is closer to the asteroid belt too.  Our moon helps pull in a lot of meteors that might have hit the earth.  Mars has no large moon. 

There are a lot of reasons for nuclear back up power.  Nuclear power plants are shut down for maintenance in my state during the spring or fall when power use is down.  Coal, hydro, and natural gas take up the slack when nukes are down and vice versa coal and natural gas are down for maintenance when nukes are running.  Sometimes we have droughts and hydro is down.  When dust storms happen and a meteor shower happens, what will be the backup? 

I still think there should be more than one source of power.  Mars is and will be remote from earth, and having redundancy is a must for everything done on Mars.   
I do not think that there are many that are against using nuclear power on Mars - what people are arguing against is saying that there must be nuclear power. An operational full scale Mars certified reactor would be welcomed with open arms but getting one ready in time would likely require a development program and budget that would dwarf anything done by SpaceX. What people are saying is that while nuclear might be great someday PV solar is good enough today.

Being able to shield the reactor does not make the power supply more secure as it would still require a large field of radiators on the surface. Solar will inherently be far more redundant with regard to accidents and failures.
Title: Re: Power options for a Mars settlement
Post by: wes_wilson on 03/04/2020 11:58 am
Many of the newer reactor designs do no need as much or any water for cooling.  If properly designed they can use all the heat for power production.  Thorium and pebble bed reactors would be great on Mars.  I do not see what so many have against nuclear power.  The sun doesn't shine at night, and with dust storms, low power production can put a strain on a colony for survival.  Nuclear can run 24/7.  Nukes can also help warm Mars which is what people want for terra forming.  Thin film solar rolls could be blown to bits if high winds happen on Mars.  Surface scratches from dust storms will degrade solar faster than on earth which has rain water. 

Lots of things to consider.  Like I said, the only two real choices on Mars are solar and nuclear.  One showed how much power it took to make what the average person needed for steel.  What about aluminum, copper, brass, tin, etc.  What about recharging the electric earth moving equipment, cranes, forklifts, trains or rovers.  It would be nice to charge them at night instead of only the daytime.  Most outside work would be done in the daytime when the sun shines.  This equipment will have to be charged at night.  The weight for battery banks large enough to supply nighttime power alone would probably weigh more than a nuke power plant.  All would have to be brought from earth unless rare earth minerals are found on Mars to make them on Mars. 

Nuclear power plants could be buried for safety.  What if a Starship crashed on a solar power field, knocking out a lot of power for the colony.  It could be a game changer.  Also Mars seems to get a lot of asteroid or meteor hits where the earths atmosphere burns them up.  A meteor shower could also knock out a solar field.  Mars is closer to the asteroid belt too.  Our moon helps pull in a lot of meteors that might have hit the earth.  Mars has no large moon. 

There are a lot of reasons for nuclear back up power.  Nuclear power plants are shut down for maintenance in my state during the spring or fall when power use is down.  Coal, hydro, and natural gas take up the slack when nukes are down and vice versa coal and natural gas are down for maintenance when nukes are running.  Sometimes we have droughts and hydro is down.  When dust storms happen and a meteor shower happens, what will be the backup? 

I still think there should be more than one source of power.  Mars is and will be remote from earth, and having redundancy is a must for everything done on Mars.   
I do not think that there are many that are against using nuclear power on Mars - what people are arguing against is saying that there must be nuclear power. An operational full scale Mars certified reactor would be welcomed with open arms but getting one ready in time would likely require a development program and budget that would dwarf anything done by SpaceX. What people are saying is that while nuclear might be great someday PV solar is good enough today.

Being able to shield the reactor does not make the power supply more secure as it would still require a large field of radiators on the surface. Solar will inherently be far more redundant with regard to accidents and failures.

That's really my view. 

Do I want nuclear on Mars?  100%!
Do I want to wait to visit Mars for nuclear?  0%

I think it was suggested some tens of pages back; but this topic probably has a natural split at some size of colony.  Power options for a Mars settlement of under 1K people vs. power options for a Mars settlement of 1M people.



Title: Re: Power options for a Mars settlement
Post by: Lar on 03/04/2020 01:37 pm

That's really my view. 

Do I want nuclear on Mars?  100%!
Do I want to wait to visit Mars for nuclear?  0%


Exactly so. Solar+batteries (+ maybe a methalox genset) is enough to get quite a ways. If and when nuclear is ready, add it.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/05/2020 02:29 am
Thorium and pebble bed reactors would be great on Mars.

Thorium is just a breeder for uranium. It doesn't mean "better nuclear power", it just means "cheaper fuel if uranium becomes expensive" which it hasn't.

Pebble-bed reactors have turned out to be a huge disappointment, low energy density, poor operating temperatures, high wear and failure rates. The only benefit has been the development of micro-kernels to use in "prismatic" fuel-rods.

I do not see what so many have against nuclear power.

It's not saying "No nukes on Mars!", it's objecting to people saying "No Mars without nukes!"

and with dust storms, low power production can put a strain on a colony for survival.

As I've repeatedly said in earlier posts (with numbers!), dust storms aren't death-to-PV. They are just an inconvenience.

Thin film solar rolls could be blown to bits if high winds happen on Mars.

Because of the thinness of Mars' atmosphere, they produce vastly less force. The highest recorded windspeed on Mars (about 110km/h, 70MPH), has the same force as a 15km/h (10MPH) wind on Earth. Double the highest ever recorded wind-speed on Mars, it's still only equivalent to a 30km/h (20MPH) wind on Earth.

As for accidents: Solar will tend to be spread out, so a single accident can't take out the whole system. Indeed, that's an advantage over nukes. Solar and batteries can be decentralised and self-redundant. Likewise for meteors: the ISS solar arrays are riddled with holes from orbital debris, but they still work.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/05/2020 02:43 am
The weight for battery banks large enough to supply nighttime power alone would probably weigh more than a nuke power plant.

Even with a nuke, you still need enough backup power to cover the colony when the reactor is taken off-line for maintenance/refuelling/faults/etc. (Similarly to cope with rapid changes in demand.) So it's not nukes vs batteries. It's nukes and enough batteries for several days backup vs solar and enough batteries. Hence we aren't comparing the mass of the nuke against PV+batteries, we're comparing the nuke against the PV arrays alone. The batteries are required either way.

You can also import PV and batteries scaled to cargo-size or colony needs without losing efficiency. Big or small, the efficiency is the same. Nuclear power doesn't scale down well due to thermodynamic issues. So if you scale it down to fit the ship, or because you don't have the resources to build and maintain a large reactor, you lose efficiency. Ten 10MW reactors masses much more than a single 100MW reactor. You can't gradually "ramp up" with nuclear as the colony grows without ending up with a bunch of low-efficiency reactors. (Although at least then you do have redundancy between reactors.)

Being able to distribute your power system also helps with adapting to the needs of the colony. You can easily move solar arrays (and battery packs) out to a mine-site for a couple of years. If a critical resource turns out to be a couple-of-recharges travel away from the main colony, you can set up way-stations with their own PV and batteries, plus a small habitat at the work-site along with more PV+batteries to supply power there. With nuclear, you'd either have to run a power-line hundreds of kilometres, or use a small (low efficiency) reactor at each site.

Nuclear power isn't magic. It isn't free unlimited power, it has its own issues. Just because you need a lot of power, doesn't give nuclear power any special advantage over PV for supplying that power.



Re: Charging vehicles.

You aren't limited to a single place to charge them. Because of the distributed nature of the solar arrays, more often than not you will be able to plug in the vehicles at your work-site during the day.
Title: Re: Power options for a Mars settlement
Post by: DAZ on 03/05/2020 03:04 am
The tyranny of the question to engineers, energy per capita, energy poverty, scale factors, and limiting growth.

If you ask the wrong question of engineers, you will get the wrong answer.  This wrong answer can trap you into an unsustainable solution.  Using real numbers for how much energy is used per capita on earth may be a better starting point for how much energy will be needed on Mars.  The question becomes, is Mars more like China, the United States, Canada, or is it more like Iceland.  These are real numbers for real societies on earth.  They have real working industries and real environmental temperature swings.  I suspect on Mars, power requirements would be more than Iceland.  Not only do you have the colder temperatures in the additional power burden of creating propellant for the return trip but the additional power burden of all the mining and industry that needs to be bootstrapped.
https://en.wikipedia.org/wiki/List_of_countries_by_electricity_consumption

Energy poverty will be a real issue on Mars.  It will limit not only your standard of living but your rate of growth.  The faster you can have an excess of power and the more far-reaching areas on Mars that this power can be used will be the primary limit of the rate of growth.  Having multiple smaller nuclear reactors that can be placed in multiple locations (and possibly relocated as needed) for mining, propellant manufacturing, and living quarters/food production may be one of the engineering technology keystones.  Power production will be the Keystone technology that drives all the other technologies.  When you add in power distribution to multiple distant locations and the relocation costs for solar, it would not appear to scale near as well as the new fourth-generation nuclear reactors.  These newer reactor designs are much smaller and more efficient than the older designs.  Just there higher operating temperatures could make them much more efficient for cracking water into hydrogen and oxygen and reduce the energy needed for propellant manufacturing.  They are not your grandfather’s nuclear reactor.
https://en.wikipedia.org/wiki/Energy_poverty

Using real numbers with real goals should reduce some of the fudge factors used in the calculations for how much power will be needed on Mars.
https://en.wikipedia.org/wiki/Fudge_factor
Title: Re: Power options for a Mars settlement
Post by: spacenut on 03/05/2020 03:08 am
Most of the exploring will be done in the daytime, and may go as far as at least half the battery charge will get them.  This exploring will be looking for geologic formations for mineral deposits.  You can't explore if you have to charge during the day, unless you have something like the 45 minute charge from a Tesla charging station.  Maybe remote solar array charging stations can be strung in rings around the initial colony to expand out from the colony until minerals are found.  Then, maybe an electric rail system can bring back the ore for processing.

Someone said the power produced on Mars via solar panels would only be about 40% of what earth based solar could produce.  That means probably an acre per average American home's power use, not counting greenhouses, fuel production, etc.  I think the solar panels should be mounted high to avoid being covered by dust.  Rolled across the ground initially, but high as soon as they can be brought from earth.  Landing rockets are going to stir up a lot of dust until a landing pad or pads can be built. 
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/05/2020 03:30 am
[...]

You are doing the same thing as spacenut. Listing a bunch of reasons Mars will have high energy demand, and then declaring nuclear power the automagical winner. You keep skipping the part where you actually show that nuclear has a better cost/benefit on Mars than PV.

When you add in power distribution to multiple distant locations and the relocation costs for solar

Why do you "add in" the "relocation cost" for solar, but not for nuclear?

Stop treating nuclear as if it's somehow free.

solar [...] would not appear to scale near as well as the new fourth-generation nuclear reactors. These newer reactor designs are much smaller and more efficient than the older designs.  Just there higher operating temperatures could make them much more efficient for cracking water into hydrogen and oxygen and reduce the energy needed for propellant manufacturing.  They are not your grandfather’s nuclear reactor.

You made the claim, but you forgot to actually show how this is the case...

Using real numbers with real goals
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/05/2020 04:16 am
You can't explore if you have to charge during the day, unless you have something like the 45 minute charge from a Tesla charging station.

So now that you can see it's not an issue, why are you still treating it like it's an issue?

Maybe remote solar array charging stations can be strung in rings around the initial colony to expand out from the colony until minerals are found.

And how would you replicate that if you were using nuclear power? Unless you put a small, inefficient reactor at each site?

(In theory, you could have an even less efficient trailer-mounted reactor being towed behind the exploration rover. Not a good solution, but it is very SF-cool.)

Realistically, exploration is generally a trivial part of the energy use in mining. You main power uses are going to be a cluster of known sites. The main settlement, mostly agriculture. The rocket operations area. Industrial areas. Mine sites.

That means probably an acre per average American home's power use [etc]

Why are you so fixated on the area? We aren't cutting down forests or paving over farmland to do this. Who cares how big it is?

The only issues that matter are cost/mass/labour/reliability.

I think the solar panels should be mounted high to avoid being covered by dust.

All they need is to be tilted slightly towards the equator, with one side held up by a wire on pegs. That will reduce dust build-up, optimise power production, while still being light and easy to deploy. You don't need to mount them any higher.
Title: Re: Power options for a Mars settlement
Post by: colbourne on 03/05/2020 10:28 am
By the time we get to Mars there is a good chance that they will be getting good results with the hydrogen-boron fusion reactor.
I don't know whether Elon wants to diversify his interests any more, but I would think this is something he ought to look into. It would be much lighter than normal fusion or fission reactors as little shielding is required, and it outputs electricity directly without the need for turbines and generators.

https://newatlas.com/energy/hb11-hydrogen-boron-fusion-clean-energy/?utm_source=New+Atlas+Subscribers&utm_campaign=2d9041b886-EMAIL_CAMPAIGN_2020_02_23_11_52&utm_medium=email&utm_term=0_65b67362bd-2d9041b886-90223594&fbclid=IwAR1S6ZumiLctC0AliYvbiy72DxQbpARNX-vl6SOE2d1dKLAoJ3BvnJIinSU
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 03/05/2020 11:07 am
One I think nuclear power is a must to get started ASAP is because massive amounts of power are needed to mine and smelt metals.  Metal mining and smelting is the foundation of modern society.  Right behind agriculture.  Iron, copper, lead, zinc, tin, bauxite, nickel, chromium are all needed for anything modern to be made, including microchips.

Second, if there is no oil or coal on Mars, carbon based products, plastics and such will have to be made via power starting with the sabatier process for making methane.  From methane using abundant power you can chain the methane molecules to make other hydrocarbons.  These can also be made from sawdust if trees are grown for fruit and nuts, and later for wood products such as simple toilet paper. 

Then you have the chemical industry that has to get started.  Everything from drugs, cleaners, ammonia and nitrates agriculture etc.

Earth's power production started with hydroelectric generation as well as steam generation with old fashioned steam engines.  No coal or plentiful hydrocarbons eliminates the steam generation process.  No rivers eliminates the hydroelectric production.  That only leaves solar and nuclear.  Even sabatier methane has to have power so that is eliminated except for emergencies.  Start with solar then ASAP bring in nuclear.

Mars will never get independent of earth without massive amounts of power that solar/batteries alone cannot give.

Are there proven uranium deposits on Mars sufficient to supply a nuclear industry with enough ore?

Given (to start with at least) Terran laws will apply on Mars, where will Mars import its uranium from? Will it accept nuclear weapons inspectors from the UN to prove it's not building nuclear Interplanetary Missiles? Or do we assume the Mars nationstate will be a simply colony of the United States?

Does nuclear power really give a Martian nationstate independence, or does it complicate matters?
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 03/05/2020 11:17 am
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy - it seems to be almost forgotten in the whole epic argument of nuclear vs solar.

If they finally get the damn mole from Mars InSight into the ground we should find out a lot more about what's under the surface of Mars, including things like temperature gradients, but we can fairly safely assume geothermal will be usable on Mars as it is on Earth, given gigantic balls of rock compressed under their own gravity should be toasty on the inside.

Another poster just up the thread mentioned how they see a society on Mars being comparable to Iceland. I find this quite interesting because Iceland, being where they are geographically, also rely on a lot of geothermal energy: 25% of their electricity generation is from geothermal; 5.245 GWh in 2013. [1].

It's great because you can generate both heat (from ground source heat pumps) and electricity and it isn't affected by those pesky dust storms.

Instead of solar + batteries + nuclear, would solar + batteries + geothermal be enough to scale a Martian society to a population in the millions? How sure are we that geothermal is viable on Mars?

[1] Geothermal power facilities currently generate 25% of the country's total electricity production
Title: Re: Power options for a Mars settlement
Post by: eriblo on 03/05/2020 11:24 am
By the time we get to Mars there is a good chance that they will be getting good results with the hydrogen-boron fusion reactor.
I don't know whether Elon wants to diversify his interests any more, but I would think this is something he ought to look into. It would be much lighter than normal fusion or fission reactors as little shielding is required, and it outputs electricity directly without the need for turbines and generators.

https://newatlas.com/energy/hb11-hydrogen-boron-fusion-clean-energy/?utm_source=New+Atlas+Subscribers&utm_campaign=2d9041b886-EMAIL_CAMPAIGN_2020_02_23_11_52&utm_medium=email&utm_term=0_65b67362bd-2d9041b886-90223594&fbclid=IwAR1S6ZumiLctC0AliYvbiy72DxQbpARNX-vl6SOE2d1dKLAoJ3BvnJIinSU
We already have statements from Elon to the effect that power production on mars is low priority due to currently available solutions (solar) being good enough. There are other things that are higher on the priority list that are currently receiving limited attention due to lack of resources, like life support.

BTW, I find it very comic-villainesque to look at potential clean fusion reactor and think "Elon should invest, perfect for Mars base" while not considering the US$ 6 trillion global energy sector ;)
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/05/2020 12:26 pm
Even with a nuke, you still need enough backup power to cover the colony when the reactor is taken off-line for maintenance/refuelling/faults/etc.

When nuclear power on Mars becomes a realistic option, they'll probably have multiple reactors with some redundancy.
Conceptually, this is like having engine-out capability on a rocket. A rocket with just 1 larger engine is generally less reliable.

Also, as many have stated, in order to cover emergencies you only need a small fraction of the peak power output.

As I've said before, I think solar and nuclear complement one another, both on Earth and on Mars.
Nuclear supplies the baseline power while solar provides the extra power needed during the day.
Yes, you'll also need some batteries, but much less than you would with a solar-only system.

However, as wes_wilson stated eloquently above, no one wants to wait until nuclear power on Mars becomes a realistic option,
so the initial Mars settlement will use solar power only.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/05/2020 01:04 pm
Are there proven uranium deposits on Mars sufficient to supply a nuclear industry with enough ore?
Probably not.

Given (to start with at least) Terran laws will apply on Mars, where will Mars import its uranium from?
3rd and 4th gen nuclear reactors run on thorium or depleted uranium.
Only the older 2nd gen reactors require enriched uranium.
By the time they start building reactors on Mars to grow the colony, I doubt they would use the older 2nd gen type.

Does nuclear power really give a Martian nationstate independence, or does it complicate matters?
The mass of the thorium or depleted uranium is trivial, and it can be stored for later use up to 100 years or more.
So once they have a sufficient amount on Mars, they would be set for a long time.
By the time that runs out, we may be using fusion power, which uses tiny amounts of hydrogen.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/05/2020 04:16 pm
Not thinking of fiber either. You're overcomplexifying, The idea Spudis et al referred to was akin to sintering, Rather than forming wafers, the surface is glassified, then a second pass etches and dopes as needed. Right there on graded ground.

That definitely won't work.

This is an old paper and it's entirely possible that the authors are confused. But they seemed to think it would work.

https://www.newscientist.com/article/dn6892-lunar-colony-to-run-on-moon-dust-and-robots/

<snip>

I missed that they are suggesting there would be some refining by these mobile solar cell creating rovers, though.

Also this is using lunar materials, not Martian.

The experiment (https://www.sciencedirect.com/science/article/abs/pii/S0094576504003686) made substrate from lunar JSC-1 simulant. 

Note:  The active-layer thin film wasn't made from JSC-1, because it couldn't be:  they used cadmium and tellurium, not present in JSC-1 (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=2ahUKEwiew8qr6IPoAhWTHc0KHXPZCdoQFjABegQICxAF&url=https%3A%2F%2Fwww.lpi.usra.edu%2Flunar%2Fstrategies%2Fjsc_lunar_simulant.pdf&usg=AOvVaw2ZtSMG0yHsZCbcNpOkZLGB).
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/05/2020 05:51 pm
[...]
Tau is reported during storms because transmission translates most directly into PV power.
Incorrect. Even your own claimed figures show a reduction to 20%, not a reduction to <2% as would be expected by Tau=4, or <1% as would be expected by Tau=5.
So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%.
[...]
Transmission is the #1 factor, which is why it's reported, and why you didn't show otherwise.

I already did, you even quoted it above. Using your own supplied (if uncited) figures combined with the figures from the paper you did cite, show that total insolation is highly predictive of PV power levels, while direct beam insolation (what you call "transmission") is not. Since that's what I've been saying all along, you proved my point.

No, the 2007 power crisis matches my statement (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512).  Neither you nor Twark_Main have given reasoning consistent with crisis facts.  By your statements only, the crisis remains a mystery, the drop from 700 Wh to < 130 Wh daily output explained nowhere in your posts. 

Again, while the decadal dust storms [...]
But no, they're not decadal
Since 1873 there have been 12 global dust storms, treating 1977 as two separate storms. (McKim (2008) and adding 2018.)
No, your statement was just incorrect.  It's not true that "decadal dust storms can last for months," and "the worst storm conditions [last] an odd day or two."  Any global dust storm can last for months, and these storms occur about every 5.5 years.  And of course the worst conditions don't last "an odd day or two".
[...]
Also, you didn't actually give a reference.

Well, one of us didn't.

Global storm frequency (~5.5 years) is common knowledge, Paul451.  You ignored the planetary scientist quoted (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2051211#msg2051211).  And you still haven't given the actual reference supposedly backing your "decadal" narrative, with its "odd day or two" of worst conditions. 

If the topic is interesting, Kass et al. 2014 gives some example data to begin tallies (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2053311#msg2053311) of month+ storms.

Image:  "Figure 1.  Daytime zonal mean temperatures versus season from TES at 50 Pa, Ls 180° to 360°, for MY 24. The red contour at 200 K and orange one at 197 K are to define the storms, other contours help define the overall storm and background behavior."  Kass et al. 2014.

Refs.

Kass, D.M., Kleinböhl, A., McCleese, D.J., Schofield, J.T. and Smith, M.D., 2014, January. Observations of large dust storms during the Martian dusty season. In Proceedings of the 5th International Conference on the Mars Atmosphere. Oxford.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/05/2020 07:24 pm
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy - it seems to be almost forgotten in the whole epic argument of nuclear vs solar.

If they finally get the damn mole from Mars InSight into the ground we should find out a lot more about what's under the surface of Mars, including things like temperature gradients, but we can fairly safely assume geothermal will be usable on Mars as it is on Earth, given gigantic balls of rock compressed under their own gravity should be toasty on the inside.

Another poster just up the thread mentioned how they see a society on Mars being comparable to Iceland. I find this quite interesting because Iceland, being where they are geographically, also rely on a lot of geothermal energy: 25% of their electricity generation is from geothermal; 5.245 GWh in 2013. [1].

It's great because you can generate both heat (from ground source heat pumps) and electricity and it isn't affected by those pesky dust storms.

Instead of solar + batteries + nuclear, would solar + batteries + geothermal be enough to scale a Martian society to a population in the millions? How sure are we that geothermal is viable on Mars?

[1] Geothermal power facilities currently generate 25% of the country's total electricity production

Unlike Earth, Mars has little or no magnetic field.  On Earth, the magnetic field is created by a hot liquid metal core
So the absence of a magnetic field on Mars may well indicate that the core of Mars has cooled significantly.
This wouldn't be surprising, since Mars is much smaller than Earth.  In this case, Geothermal power may not be viable.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/05/2020 08:31 pm
the absence of a magnetic field on Mars may well indicate that the core of Mars has cooled significantly.

The absence of THEMIS surface hotspots would also seem consistent with a cool core.  Geothermal power doesn't appear to be in the cards today, barring some truly surprising Insight results.

Very large impactors can produce sufficient heating, but again, there's no observed hotspot, so no such event is likely recent.

Data point:  Our team's hydrocode modeling of MATT's ~ 9 km impact crater (http://www.lakematthew.com/notes/omaha-crater/) showed heating insufficient for geothermal power.
Title: Re: Power options for a Mars settlement
Post by: colbourne on 03/05/2020 09:15 pm
By the time we get to Mars there is a good chance that they will be getting good results with the hydrogen-boron fusion reactor.
I don't know whether Elon wants to diversify his interests any more, but I would think this is something he ought to look into. It would be much lighter than normal fusion or fission reactors as little shielding is required, and it outputs electricity directly without the need for turbines and generators.

https://newatlas.com/energy/hb11-hydrogen-boron-fusion-clean-energy/?utm_source=New+Atlas+Subscribers&utm_campaign=2d9041b886-EMAIL_CAMPAIGN_2020_02_23_11_52&utm_medium=email&utm_term=0_65b67362bd-2d9041b886-90223594&fbclid=IwAR1S6ZumiLctC0AliYvbiy72DxQbpARNX-vl6SOE2d1dKLAoJ3BvnJIinSU
We already have statements from Elon to the effect that power production on mars is low priority due to currently available solutions (solar) being good enough. There are other things that are higher on the priority list that are currently receiving limited attention due to lack of resources, like life support.

BTW, I find it very comic-villainesque to look at potential clean fusion reactor and think "Elon should invest, perfect for Mars base" while not considering the US$ 6 trillion global energy sector ;)
That's how Elon works. I think his top priority is Mars, where he needed electric cars,solar power and boring equipment to build living space. He did not want all the hassle with government requirements on radio active materials with nuclear fission power, but if he can solve the worlds clean energy shortage at the same time as offering backup power for solar panels in case of dust storms, I think he should be interested.
The work on a hydrogen-boron fusion reactor is already underway, but if SpaceX can speed up its progress, I think everyone would be happy.
Title: Re: Power options for a Mars settlement
Post by: r8ix on 03/05/2020 09:26 pm
That's how Elon works. I think his top priority is Mars, where he needed electric cars,solar power and boring equipment to build living space.

But why the flamethrowers?
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/05/2020 10:06 pm
That's how Elon works. I think his top priority is Mars, where he needed electric cars,solar power and boring equipment to build living space.
But why the flamethrowers?

Merchandising!

https://www.youtube.com/watch?v=0DLZGOZWDHs
Title: Re: Power options for a Mars settlement
Post by: DAZ on 03/06/2020 12:58 am
[...]

You are doing the same thing as spacenut. Listing a bunch of reasons Mars will have high energy demand, and then declaring nuclear power the automagical winner. You keep skipping the part where you actually show that nuclear has a better cost/benefit on Mars than PV.

When you add in power distribution to multiple distant locations and the relocation costs for solar

Why do you "add in" the "relocation cost" for solar, but not for nuclear?

Stop treating nuclear as if it's somehow free.

solar [...] would not appear to scale near as well as the new fourth-generation nuclear reactors. These newer reactor designs are much smaller and more efficient than the older designs.  Just there higher operating temperatures could make them much more efficient for cracking water into hydrogen and oxygen and reduce the energy needed for propellant manufacturing.  They are not your grandfather’s nuclear reactor.

You made the claim, but you forgot to actually show how this is the case...

Using real numbers with real goals

Much of this thread has been a moot discussion regarding what is the minimum power requirements and how to minimally satisfy these requirements.  This, I believe, is the wrong question.  The question of what is the energy starvation level has some relevance. I just don’t think it should be the primary question.  I’m not trying to demonstrate that more energy will be needed on Mars than what are these minimum requirements.  I am trying to say that designing everything for the minimums can trap you at the minimum.  I believe the question should be how to get as much power to Mars as possible in the shortest time period.

I am not against solar.  For the 1st few landing cycles on Mars, solar most likely will be the system used.  Nuclear power systems most likely will not be available immediately.  Looking only at the minimalistic energy approach and only using solar will most likely result in slow growth.  This time-consuming and costly growth, in my opinion, is the primary risk to project failure.  Quite probably, having an overabundance of power on Mars, if it were to occur, would only be in the short term.  As fast as you can get power to Mars will dictate how faster growth is.  The power requirements of various societies on earth that I provided in the link were to demonstrate that real thriving communities need much more energy than the minimums.  This is what I meant by using real numbers.  Specifying how many ships per landing cycle and how many additional people in planning for future energy growth is what I meant by real goals.

Nuclear power doesn’t scale down as well as solar.  To have a minimum operating efficiency, you will need a minimum amount of mass.  Solar, on the other hand, does scale down very efficiently.  You can scale solar down to only watts of power if that’s what you need.  That is not very realistic for nuclear.  Nuclear appears to scale up much better than solar.  Neither solar nor nuclear is free on Mars, but the driving cost will be mass and cube.

As you scale up a solar-based system, you’ll need to add both the power distribution and the energy storage systems.  These solar-based systems will quickly become miles crossed and tens of miles from where the energy is needed.  To accomplish this, you’ll need to add in the mass and cube of the voltage step-up/step-down systems and the distribution cable/insulation.  Much of the discussion has only been in this thread the mass and cube of just the solar-based system, not the energy distribution part of the system.  You can offset some of the mass of the cable by stepping up the voltage even higher.  But as you do so, you’ll need to add more insulation.  At some voltage level, you will need to elevate your cable on towers as the mass and cube of the insulation will exceed the mass and cube of towers.  A nuclear-based system could be built much closer to where the energy is needed.  Additionally, as the energy needs go up, and the solar production goes up, the mass and cube of the energy storage system will go up.  Nuclear-based systems don’t need an energy storage system.  This is why I’m referring to solar-based systems don’t scale up as well as a nuclear-based systems.

Power will needed in large quantities in at least three distinct types of locations.  A mining location, a living/housing location, and a propellant manufacturing location.  The living/housing location and propellant manufacturing location will most likely be miles apart.  The mining location will most likely be tens of miles away.  A nuclear power generator could be located at each of these locations independently.  If it is decided to either expand or move one of these locations, quite likely for the mining as you mine out the resources in the area, you will need to move your power.  Picking up and moving a solar production facility would be exceptionally difficult and expensive.  Moving all of your power distribution would also be complicated and costly.  Shutting down the nuclear power plant and moving it to its new location would be much simpler and cheaper.  This is what I was referring to as the relocation cost for solar and why I did not add it to nuclear.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/06/2020 05:57 am
Much of this thread has been a moot discussion regarding what is the minimum power requirements and how to minimally satisfy these requirements.  This, I believe, is the wrong question.  The question of what is the energy starvation level has some relevance. I just don’t think it should be the primary question.  I’m not trying to demonstrate that more energy will be needed on Mars than what are these minimum requirements.  I am trying to say that designing everything for the minimums can trap you at the minimum.  I believe the question should be how to get as much power to Mars as possible in the shortest time period.
I am not against solar.  For the 1st few landing cycles on Mars, solar most likely will be the system used.  Nuclear power systems most likely will not be available immediately.  Looking only at the minimalistic energy approach and only using solar will most likely result in slow growth. This time-consuming and costly growth, in my opinion, is the primary risk to project failure.  Quite probably, having an overabundance of power on Mars, if it were to occur, would only be in the short term.  As fast as you can get power to Mars will dictate how faster growth is.  The power requirements of various societies on earth that I provided in the link were to demonstrate that real thriving communities need much more energy than the minimums.  This is what I meant by using real numbers.  Specifying how many ships per landing cycle and how many additional people in planning for future energy growth is what I meant by real goals.

(Quoted in full because I wanted to show the non-sequitur.)

You simply assume that solar is only good for "minimal" power, and assume that nuclear just "will" provide ample power. That assumption underlies everything written above. And because of that assumption, you think the that to justify nuclear you have to keep arguing that "Mars needs lots of power", which is why you (and Spacenut) keep repeating the reasons a Mars settlement needs a lot of power. Why you think not having nuclear means "being trapped at minimum requirements".

Your argument is:

1: A Mars settlement needs "X" capability.
2: "X" requires a lot of power.
3:  ???
4: Only nuclear power allows a Mars settlement.

You haven't actually shown that nuclear power is the best way to achieve any given level of power requirements beyond the "first few landing cycles", you just assume it.

Look at the one attempt you did make to claim that solar can't scale up, that solar power will require "tens of miles" of "distribution". Which is apparently so massive and complex that it completely exceeds the mass and complexity of a nuclear power station of similar power. That's it. That's all you've come up with so far to justify your assumption.

(And it's patently wrong. Power cabling over a few miles, or tens of miles, will need to be routine on Mars, since you need to separate things like launch facilities and propellant production/storage from each other and from habitats. Likewise, higher voltages will be required for the many industrial requirements you yourself have listed.)

Power will needed in large quantities in at least three distinct types of locations.  A mining location, a living/housing location, and a propellant manufacturing location.  The living/housing location and propellant manufacturing location will most likely be miles apart.  The mining location will most likely be tens of miles away.  A nuclear power generator could be located at each of these locations independently.

[Quibble: Housing will be a trivial part of the power demand. The three monsters are 1: Agriculture; 2: Propellant; 3: Industry. Living areas are a rounding off error.]

You can't localise a nuclear plant for each activity. You have to string them together by power lines or else when one goes down for maintenance or a simple-but-time-consuming fault, you lose that entire activity. Zero redundancy unless you string "tens of miles" of power cabling capable of handling the full loads of multiple reactors.

(Aside: I consider a mine that is "tens of miles" away from the settlement to be a local mine, running off the local power grid. IMO, only once you get into the hundreds of miles do you need to consider the cost of local power vs stringing long stretches of power lines.)

Picking up and moving a solar production facility would be exceptionally difficult and expensive.
Shutting down the nuclear power plant and moving it to its new location would be much simpler and cheaper.

Que? That does not make any sense at all.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/06/2020 05:57 am
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy
[...] we can fairly safely assume geothermal will be usable on Mars as it is on Earth

Geothermal on Earth requires areas that are geologically active. (Such as Iceland, New Zealand, etc.) There doesn't seem to be such areas on Mars. The big volcanoes aren't currently active. There's no indication of useful, reachable heat.

Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/06/2020 06:11 am
[...]
Tau is reported during storms because transmission translates most directly into PV power.
Incorrect. Even your own claimed figures show a reduction to 20%, not a reduction to <2% as would be expected by Tau=4, or <1% as would be expected by Tau=5.
So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%.
[...]
Transmission is the #1 factor, which is why it's reported, and why you didn't show otherwise.
I already did, you even quoted it above. Using your own supplied (if uncited) figures combined with the figures from the paper you did cite, show that total insolation is highly predictive of PV power levels, while direct beam insolation (what you call "transmission") is not. Since that's what I've been saying all along, you proved my point.
No, the 2007 power crisis matches my statement (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512).  Neither you nor Twark_Main have given reasoning consistent with crisis facts.  By your statements only, the crisis remains a mystery, the drop from 700 Wh to < 130 Wh daily output explained nowhere in your posts.

"So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%."

Again, while the decadal dust storms [...]
But no, they're not decadal
Since 1873 there have been 12 global dust storms, treating 1977 as two separate storms. (McKim (2008) and adding 2018.)
No, your statement was just incorrect.  It's not true that "decadal dust storms can last for months," and "the worst storm conditions [last] an odd day or two."  Any global dust storm can last for months, and these storms occur about every 5.5 years.  And of course the worst conditions don't last "an odd day or two".
[...]Also, you didn't actually give a reference.
Well, one of us didn't.
Global storm frequency (~5.5 years) is common knowledge, Paul451.

"Since 1873 there have been 12 global dust storms, treating 1977 as two separate storms. (McKim (2008) and adding 2018.)"
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 03/06/2020 06:52 am
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy
[...] we can fairly safely assume geothermal will be usable on Mars as it is on Earth

Geothermal on Earth requires areas that are geologically active. (Such as Iceland, New Zealand, etc.) There doesn't seem to be such areas on Mars. The big volcanoes aren't currently active. There's no indication of useful, reachable heat.

That's a shame.

I suppose we could still use ground source heat pumps for space heating as they don't need a big temperature gradient, but it sounds like geothermal electricity generation is out.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 03/06/2020 10:52 am
Two other points that need to be made about nuclear power on Mars:
1- The development costs of the reactors, in particular of larger models, will not be borne by NASA or some other agency but by the colony.  And these costs are likely to be large.  In fact, I expect they will be impossible to recoup without a large number of reactors.

2-  Nuclear power is baseload power.  It is not very good at a varying load.  And a Martian settlement will have a significant variable load because it's logical to follow the 24 hour cycle of the sun, and the main power use, food production, is inherently variable because that's how plants have evolved.
Title: Re: Power options for a Mars settlement
Post by: Eka on 03/06/2020 11:10 am
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy
[...] we can fairly safely assume geothermal will be usable on Mars as it is on Earth

Geothermal on Earth requires areas that are geologically active. (Such as Iceland, New Zealand, etc.) There doesn't seem to be such areas on Mars. The big volcanoes aren't currently active. There's no indication of useful, reachable heat.

That's a shame.

I suppose we could still use ground source heat pumps for space heating as they don't need a big temperature gradient, but it sounds like geothermal electricity generation is out.
Too cold of ground near the surface. 6 foot down in the ground here on earth averages about at the average yearly temperature for that spot. I'd expect similar on Mars.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/06/2020 12:19 pm
Two other points that need to be made about nuclear power on Mars:
1- The development costs of the reactors, in particular of larger models, will not be borne by NASA or some other agency but by the colony.  And these costs are likely to be large.  In fact, I expect they will be impossible to recoup without a large number of reactors.

2-  Nuclear power is baseload power.  It is not very good at a varying load.  And a Martian settlement will have a significant variable load because it's logical to follow the 24 hour cycle of the sun, and the main power use, food production, is inherently variable because that's how plants have evolved.

Yes, both points are correct, but they don't tell the whole story, for example:

1- By the time a colony needs multiple large reactors, they may be in a situation to build those reactors on Mars.
    When I say "build, they could assemble the reactors using parts imported from Earth, or eventually make parts there.

2- I think solar and nuclear compliment each other beautifully.  People are naturally more active during the day.
    I suspect mining operations will be semi-autonomous, requiring human supervision.
    Other power hungry applications will also most likely be more active during the day.
    So nuclear supplies the baseload power, while solar supplies the extra power demand during the day.
    Yes, a combination of  solar and nuclear power still requires some batteries, but way less than with a solar-only system.
    However, it's important to note that nuclear power output can be varied. It can't vary quickly, but it can vary.
    Since the 1990's, France's power grid has been 70-80% nuclear. That wouldn't be possible without varying output.
    The U.S. is only 20% nuclear, so there's no reason to vary. Those plants tend to run at full output.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 03/06/2020 10:28 pm
City map for 1 000 000.

Each small circle is 800m across and holds 6000 people.  That is a basic neighborhood.
Each group of 12 neighborhoods makes up a district of 72 000 people.  The 13 districts hold 1 000 000 people.

Each of the blue solar fields produces a peak power of about 1 GW.  The overall solar power is 14-15 GW.

The overall city and solar field arrangement is 36 km in diameter.  There are two large starports, with three landing pads each and a parking area for up to 1000 starships.

The basic city plan comes from the website Carfree.com.

Each 1 GW field is composed of 1000 x 1 MW sub-fields, each with a single inverter and a 25 kV transformer.  https://en.wikipedia.org/wiki/Photovoltaic_power_station




Title: Re: Power options for a Mars settlement
Post by: Paul451 on 03/06/2020 10:34 pm
Yes, a combination of  solar and nuclear power still requires some batteries, but way less than with a solar-only system.

I don't see that a combo would require less. It would be fully used less often, and thus might extend the cycle-life of the battery farms, but you can't have less than the required emergency energy storage. You can't plan on "normal".

Since the 1990's, France's power grid has been 70-80% nuclear. That wouldn't be possible without varying output.

The European power grid is interconnected. They buy and sell power between countries to meet variable demand. And, generally, the bigger the market, the smoother and more predictable the demand curve.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 03/07/2020 12:37 am
By the time we get to Mars there is a good chance that they will be getting good results with the hydrogen-boron fusion reactor.
I don't know whether Elon wants to diversify his interests any more, but I would think this is something he ought to look into. It would be much lighter than normal fusion or fission reactors as little shielding is required, and it outputs electricity directly without the need for turbines and generators.

https://newatlas.com/energy/hb11-hydrogen-boron-fusion-clean-energy/?utm_source=New+Atlas+Subscribers&utm_campaign=2d9041b886-EMAIL_CAMPAIGN_2020_02_23_11_52&utm_medium=email&utm_term=0_65b67362bd-2d9041b886-90223594&fbclid=IwAR1S6ZumiLctC0AliYvbiy72DxQbpARNX-vl6SOE2d1dKLAoJ3BvnJIinSU (https://newatlas.com/energy/hb11-hydrogen-boron-fusion-clean-energy/?utm_source=New+Atlas+Subscribers&utm_campaign=2d9041b886-EMAIL_CAMPAIGN_2020_02_23_11_52&utm_medium=email&utm_term=0_65b67362bd-2d9041b886-90223594&fbclid=IwAR1S6ZumiLctC0AliYvbiy72DxQbpARNX-vl6SOE2d1dKLAoJ3BvnJIinSU)

“Practical fusion power generation will happen within 20 years.” This has been said for over 50 years. It may actually happen in the near future but every time I hear somebody touting fusion my minds eye see a snake oil salesman in a plaid suit.

Nothing personal. I bet you don’t even own a plaid suit.  :D   Just a knee jerk reaction.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 03/07/2020 12:56 am
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy - it seems to be almost forgotten in the whole epic argument of nuclear vs solar.

If they finally get the damn mole from Mars InSight into the ground we should find out a lot more about what's under the surface of Mars, including things like temperature gradients, but we can fairly safely assume geothermal will be usable on Mars as it is on Earth, given gigantic balls of rock compressed under their own gravity should be toasty on the inside.

Another poster just up the thread mentioned how they see a society on Mars being comparable to Iceland. I find this quite interesting because Iceland, being where they are geographically, also rely on a lot of geothermal energy: 25% of their electricity generation is from geothermal; 5.245 GWh in 2013. [1].

It's great because you can generate both heat (from ground source heat pumps) and electricity and it isn't affected by those pesky dust storms.

Instead of solar + batteries + nuclear, would solar + batteries + geothermal be enough to scale a Martian society to a population in the millions? How sure are we that geothermal is viable on Mars?

[1] Geothermal power facilities currently generate 25% of the country's total electricity production

The chances of usable geothermal on mars are, IMO, slim.

Mars is a smaller planet so the internal heating should be expected to be proportionally less.

Being smaller, the surface area/volume ratio would leave one to expect that that what internal heat there is would radiate out faster, leaving a cooler core.

Lastly, the early big smack that resulted in the moon still reverberates in plate tectonics. This is the mechanism that keeps squishing up the earths crust, bringing that hot stuff up to convenient depths. I’ve not heard of any evidence for plate tectonics on Mars.

It would be great if I’m wrong. 

Phil
Title: Re: Power options for a Mars settlement
Post by: Ghoti on 03/07/2020 01:18 am
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy - it seems to be almost forgotten in the whole epic argument of nuclear vs solar.

If they finally get the damn mole from Mars InSight into the ground we should find out a lot more about what's under the surface of Mars, including things like temperature gradients, but we can fairly safely assume geothermal will be usable on Mars as it is on Earth, given gigantic balls of rock compressed under their own gravity should be toasty on the inside.

Another poster just up the thread mentioned how they see a society on Mars being comparable to Iceland. I find this quite interesting because Iceland, being where they are geographically, also rely on a lot of geothermal energy: 25% of their electricity generation is from geothermal; 5.245 GWh in 2013. [1].

It's great because you can generate both heat (from ground source heat pumps) and electricity and it isn't affected by those pesky dust storms.

Instead of solar + batteries + nuclear, would solar + batteries + geothermal be enough to scale a Martian society to a population in the millions? How sure are we that geothermal is viable on Mars?

[1] Geothermal power facilities currently generate 25% of the country's total electricity production

The chances of usable geothermal on mars are, IMO, slim.

Mars is a smaller planet so the internal heating should be expected to be proportionally less.

Being smaller, the surface area/volume ratio would leave one to expect that that what internal heat there is would radiate out faster, leaving a cooler core.

Lastly, the early big smack that resulted in the moon still reverberates in plate tectonics. This is the mechanism that keeps squishing up the earths crust, bringing that hot stuff up to convenient depths. I’ve not heard of any evidence for plate tectonics on Mars.

It would be great if I’m wrong. 

Phil
There are several ways to generate power by utilizing temperature difference. In fact most rover and exploration satellites that use "nuclear power" actually use Seebek effect thermal electric generators. Ocean Thermal Energy Conversion (OTEC) systems use a temperature difference (of at least 77° Fahrenheit) to power a turbine to produce electricity.

So you only need the subsurface to be warm relative to the surface to use it to generate electricity. Seems like this should be possible but without knowing the temperature at depth we can only guess. Insight has failed so far to get a temperature probe past the surface of Mars.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 03/07/2020 02:56 am
Food production may be variable on earth, but with greenhouse grown food, this will be almost constant.  Once on crop of something is grown, another will take it's place almost immediately.   Power use by habitats will be more heat needed at night and less in the day, thus more power will be needed in the habitats at night.  Work areas will need more power during the day. 

There will need to be calculated what the constant minimum power requirements will be, then what the maximum power requirements will be. 

For a larger colony, nuclear power can provide the minimum requirements, then solar when the demand kicks in.  Mining and metals production will probably happen during the day, thus more power requirements during the day, unless it can be a 24 hour operation. 

If solar alone is to be used, it must grow faster than the colony can grow.  Then there are the dust storms to take into consideration.  This is a serious survival situation.  There has to be some form of backup as battery alone can't go for very long.  Therefore a growing colony will need nuclear power especially during the planet wide dust storms. 
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/07/2020 11:27 am
“Practical fusion power generation will happen within 20 years.” This has been said for over 50 years. It may actually happen in the near future but every time I hear somebody touting fusion my minds eye see a snake oil salesman in a plaid suit.

What's wrong with plaid? ;)

But seriously, yes, we shouldn't count on fusion power anytime soon.  Near term, nuclear power will be fission.

On the other hand, assuming fusion becomes viable sometime within the next 100 years, then fission reactors don't need to store more than 100 years worth of fuel.  From a mass perspective, that amount of fuel is tiny.

In other words, the promise of fusion may alleviate the need to mine thorium or uranium on Mars.

If you consider fission is a stop-gap until fusion is ready, nuclear power as a whole becomes sustainable.
Title: Re: Power options for a Mars settlement
Post by: spacenut on 03/07/2020 01:23 pm
If/When Musk gets to Mars and starts a colony.  NASA and the US government will want to get involved very quickly.  Once that happens you can bet they will bring a nuclear power plant or two to get up and running.  Then if Russia or China get involved, they too may bring a nuke or two power plants, not totally relying on solar, especially if dust storms my be involved. 

Believe me, power consumption is know by the power companies, they know when the highs and lows are and adjust their power output accordingly.  It will be a known on Mars also.  They will know the equipment usage by every single module on Mars.  So they will know if/when they need the alternate power source of a nuke. 
Title: Re: Power options for a Mars settlement
Post by: Pete on 03/07/2020 02:32 pm
I've read this entire thread on and off over the last year or so but haven't seen much discussion of geothermal energy
[...] we can fairly safely assume geothermal will be usable on Mars as it is on Earth

Geothermal on Earth requires areas that are geologically active. (Such as Iceland, New Zealand, etc.) There doesn't seem to be such areas on Mars. The big volcanoes aren't currently active. There's no indication of useful, reachable heat.

That's a shame.

I suppose we could still use ground source heat pumps for space heating as they don't need a big temperature gradient, but it sounds like geothermal electricity generation is out.

Yeah.
Geothermal needs TWO things, at least in any form that we are familiar with here on Earth
1) significant heat, not to deep. On earth, this is any region above a mantle plume.
2) the presence of groundwater at/just above the hotspot. We don't actually tap geothermal energy, but the energy in the steam that forms when the groundwater is heated.

Unfortunately for Mars, the core/mantle boundary is *WAY* deeper, and the resultant slower geological process makes the temperature gradient very much slower than on Earth.
There definitely was, and may still be, an accessible plume under Olympus Mons.
But the chance of there *also* being groundwater there, and it being deep enough to be heated?... Nope.
The surface scans would definitely have seen any H2O plumes associated with a surface hydrothermal location or otherwise active volcanic activity.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/07/2020 02:48 pm
The (Un)mysterious 2007 Power Crisis

the 2007 power crisis matches my statement (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512).  Neither you nor Twark_Main have given reasoning consistent with crisis facts.  By your statements only, the crisis remains a mystery, the drop from 700 Wh to < 130 Wh daily output explained nowhere in your posts.

"So total insolation says 30%. Direct insolation says <2%. Your own numbers say 20%."


Your only (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2052512#msg2052512) actual reasoning was:

Quote from: Paul451
when Tau reached around 5 at both sites (much less than 1% direct insolation), the total insolation went from the seasonal range of 120-170 Wm-2 down to 50 Wm-2. So a drop of just 2/3rds.

And of course the 2007 Opportunity power crisis occurred under slightly better light transmission, still resulting in a much greater drop in output than your reasoning asserts (your < 2/3 drop).

In fact, looking closely at the storm data [Edmondson et al. 2007 (https://trs.jpl.nasa.gov/bitstream/handle/2014/40575/07-3234.pdf?sequence=1&isAllowed=y)], you see that the storm's initial panel cleaning raised daily output to ~ 760 Wh, just before the crash to 128 Wh -- an 83% drop.  The crisis remains a mystery by your statement only (unless Twark_Main chooses to echo your statement again).

Refs.

Edmondson, K.M., Fetzer, C., Karam, N.H., Stella, P., Mardesich, N. and Mueller, R., 2007. Multijunction solar cells optimized for the Mars surface solar spectrum. (https://trs.jpl.nasa.gov/bitstream/handle/2014/40575/07-3234.pdf?sequence=1&isAllowed=y)
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/07/2020 04:43 pm
For reference:

Rucker, M.A., 2016. Surface Power for Mars (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160014032.pdf).

Some headings:

Quote
- Integrated surface power strategy for Mars
- Solar vs. fission surface power for Mars
- ISRU demonstrator
- Crewed mission
Title: Re: Power options for a Mars settlement
Post by: spacenut on 03/10/2020 01:24 pm
Here is something that may be transported to Mars:

https://www.defensenews.com/smr/nuclear-arsenal/2020/03/09/pentagon-to-award-mobile-nuclear-reactor-contracts-this-week/

It is a small 1.5 MW nuclear generator that can fit in a truck size cargo container and used to power military bases. 

Some of these can go to Mars along with solar panels for a good integrated power system so that a Mars colony can grow quickly. 
Title: Re: Power options for a Mars settlement
Post by: redskyforge on 03/11/2020 02:25 pm
I still think hydro power has some potential in the long run. Imagine giant insulated water tanks made from cheap Martian iron somewhere above Hellas Planitia. That's 9000m of altitude, even at reduced gravitational force it's a lot of potential energy. I ran some numbers on the train this morning and you could get quite some gigawatt hours of stored energy if you could build enough towers and keep the water from freezing too quickly.

The downside is pumped hydro systems like the one I used as a base (Ben Cruachan power station in Scotland) don't have a river behind their reservoir, so they don't actually have a net electrical generation -- they use as much energy to pump the water back up to the reservoir as they generate. So it really has to be seen as another way of storing energy, not baseload power generation like Three Gorges or the Hoover Dam.
Title: Re: Power options for a Mars settlement
Post by: Dave G on 03/11/2020 05:42 pm
I still think hydro power has some potential in the long run...
The downside is pumped hydro systems ... don't actually have a net electrical generation...
So it really has to be seen as another way of storing energy...

Right. For generating power on Mars, the most promising sources seem to be Solar and Nuclear. 

For storing energy on Mars, possible solutions include:
 a) Batteries
 b) ISRU produced methane (primarily as an emergency backup)
 c) Gravity based solutions, which would include hydro.

For energy storage, I believe efficiency and reliability will be key differentiators.

If you're moving water uphill with some type of electrically powered pump, and then using the downhill water flow to power an electrical generator, that will certainly have some efficiency losses. The pump and generator are also moving parts that are somewhat prone to failure.

To be clear, batteries aren't perfect either.  If a Li/Ion cell gets too cold, it's energy storage decreases dramatically. So battery packs will probably require some amount of energy to keep them warm, which decreases overall efficiency. 

Also, if the battery level gets too high or too low, battery life suffers. Li/Ion cells typically only last 500 full charge discharge cycles.  To increase longevity, many battery packs don't allow the charge to get too low or high.  This often means that the usable storage is only about 2/3 of it's rated value.

And even though battery cells have no moving parts, they do sometimes short, causing them to burn.
To prevent these flames form spreading to adjacent cells, battery packs often have some type of liquid cooling.

So in the end, no energy storage solution is perfect, but I suspect some are better than others.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 03/11/2020 09:30 pm
I still think hydro power has some potential in the long run...
The downside is pumped hydro systems ... don't actually have a net electrical generation...
So it really has to be seen as another way of storing energy...

Right. For generating power on Mars, the most promising sources seem to be Solar and Nuclear. 

For storing energy on Mars, possible solutions include:
 a) Batteries
 b) ISRU produced methane (primarily as an emergency backup)
 c) Gravity based solutions, which would include hydro.

For energy storage, I believe efficiency and reliability will be key differentiators.

If you're moving water uphill with some type of electrically powered pump, and then using the downhill water flow to power an electrical generator, that will certainly have some efficiency losses. The pump and generator are also moving parts that are somewhat prone to failure.

To be clear, batteries aren't perfect either.  If a Li/Ion cell gets too cold, it's energy storage decreases dramatically. So battery packs will probably require some amount of energy to keep them warm, which decreases overall efficiency. 

Also, if the battery level gets too high or too low, battery life suffers. Li/Ion cells typically only last 500 full charge discharge cycles.  To increase longevity, many battery packs don't allow the charge to get too low or high.  This often means that the usable storage is only about 2/3 of it's rated value.

And even though battery cells have no moving parts, they do sometimes short, causing them to burn.
To prevent these flames form spreading to adjacent cells, battery packs often have some type of liquid cooling.

So in the end, no energy storage solution is perfect, but I suspect some are better than others.

For energy storage could they use some variation on the Highview power liquid air "battery" using solid carbon dioxide instead?
https://www.youtube.com/watch?v=kDvlh_aG7iA
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 03/11/2020 11:11 pm
Liquid air energy storage usually is paired with some sort of high heat thermal energy storage. So you are looking on the hot end at stuff ranging from graphite blocks, to hollow resistor bricks or gravel in tanks, going up to liquid silicon (using TPV for energy recovery). So, inflatable bags of gravel maybe? Or I suppose if you can eat the losses, put heat into the ground directly via fracking a well to make an engineered geothermal reservoir.
Title: Re: Power options for a Mars settlement
Post by: MickQ on 03/29/2020 12:50 am
Don't know if this has been looked at before but what about Stirling generators with the cold end buried 2 metres and the hot end under a sun tracking fresnel lens ?  Multiple units sharing the one lens maybe.

Would it give a higher output than solar for the same land area used ?
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 03/29/2020 04:06 am
>
https://www.nextbigfuture.com/2018/01/kilopower-megapower-reactors-would-revolutionize-energy-safety-and-space-and-military-applications.html

PS: Find attached a slide with the LANL 2 MWe reactor proposal that weighs in around 35mT.  Needless to say that this 2.0 MWe concept reactor is not anywhere close to a space-qualified, off-the-shelf system like the Kilo-Power units are, but it first requires a viable market for same to be identified.

Best,

https://www.lanl.gov/discover/publications/1663/2019-february/megapower.php

LANL article (PDF)

LANL PDF... (https://www.lanl.gov/discover/publications/1663/2019-february/_assets/docs/1663-33-Megapower.pdf)

Quote
The unit is designed to be modular  and produce about 10 megawatts of
electricity. That’s on the order of one  hundredth of the maximum power output
of a large nuclear power plant—plenty  for a small town or remote research
facility, such as a cluster of mountaintop  observatories. A modest city like Santa Fe, New Mexico, with a residential population of 150,000, would probably require fve to  ten units.
>
The Los Alamos team is currently  maturing designs, testing materials, and exploring manufacturing options,  with component and systems testing not far behind.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 03/29/2020 03:18 pm
Westinghouse web page on the eVinci reactor mentioned above.  Slightly less power but still substantial.

https://www.westinghousenuclear.com/new-plants/evinci-micro-reactor


https://www.westinghousenuclear.com/Portals/0/new%20plants/evincitm/eVinci%20Micro%20Reactor%20NPJ%20M-A%202019.pdf?ver=2019-04-30-211410-367

Build & demo by 2023

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 03/30/2020 05:43 am
Westinghouse web page on the eVinci reactor mentioned above.  Slightly less power but still substantial.

https://www.westinghousenuclear.com/new-plants/evinci-micro-reactor


https://www.westinghousenuclear.com/Portals/0/new%20plants/evincitm/eVinci%20Micro%20Reactor%20NPJ%20M-A%202019.pdf?ver=2019-04-30-211410-367

Build & demo by 2023
You are aware this is  basically the big brother of Kilopower that Westinghouse have licensed from Los Alamos right?

I guess Toshibas 4S design must have taught them something about the market for these units.

Of course A solid core small reactor with heat pipe energy extraction could have been built anytime from the early 80's (or possibly earlier) had anyone been interested.  :(

Megapower is obviously much better sized to run the ISRU task. Keep in mind to run an ISRU plant for one  SS to refuel between launch windows back to earth is about 1MW continuously.

So to refuel the SS fleet will take a fleet of these to match.

The upside is with Martian temperatures there is so such thing as "waste" heat. 
Title: Re: Power options for a Mars settlement
Post by: hoardsbane on 03/30/2020 08:26 am
Don't know if this has been looked at before but what about Stirling generators with the cold end buried 2 metres and the hot end under a sun tracking fresnel lens ?  Multiple units sharing the one lens maybe.

Would it give a higher output than solar for the same land area used ?

Or even using the solar panels as the hot end ... i.e. get photo voltaic and thermal energy ...

... then comes down to whether the Stirling engines/generators pay their way on a mass basis.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 03/30/2020 03:04 pm
Westinghouse web page on the eVinci reactor mentioned above.  Slightly less power but still substantial.

https://www.westinghousenuclear.com/new-plants/evinci-micro-reactor


https://www.westinghousenuclear.com/Portals/0/new%20plants/evincitm/eVinci%20Micro%20Reactor%20NPJ%20M-A%202019.pdf?ver=2019-04-30-211410-367

Build & demo by 2023
You are aware this is  basically the big brother of Kilopower that Westinghouse have licensed from Los Alamos right?

I guess Toshibas 4S design must have taught them something about the market for these units.

Of course A solid core small reactor with heat pipe energy extraction could have been built anytime from the early 80's (or possibly earlier) had anyone been interested.  :(

Megapower is obviously much better sized to run the ISRU task. Keep in mind to run an ISRU plant for one  SS to refuel between launch windows back to earth is about 1MW continuously.

So to refuel the SS fleet will take a fleet of these to match.

The upside is with Martian temperatures there is so such thing as "waste" heat.

That is what the sources I cited say, so yes.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 03/30/2020 04:18 pm
Seems unlikely that Sterling engines will "pay their way," since their power-to-weight tends to be low. Perhaps counterintuitivly, this is precisely because they are so efficient: there's not much entropy gain to drive the system forwards. In the limit, a Sterling engine that achieves 100% of the theoretical Carnot efficiency would decay to zero specific power (ie it would stop), because the thermodynamic cycle becomes completely adiabatic, meaning there's nothing to make the heat engine prefer to run forwards instead of in reverse.

Concentrating solar is problematic because it depends on beam insolation. Here we return to LMT's earlier mistake: he said that PV more closely followed transmitted/beam insolation, not total horizotal flux (to quote LMT: "Tau... translates most directly into PV power"). But Paul451 is at least correct on that point: PV indeed more closely follows total horizontal flux (Paul451's number of 67% overestimates power output during the observed 83% drop by a factor of 2), not the transmitted flux (using LMT's theory the number would be 1 - 1/e5, ie a 99.3% drop, which underestimates the power output by a factor of 25). So if LMT thinks Paul451 is "mystified" by the 2007 dust storm, LMT himself must be utterly and completely baffled. Echoing statement secured. :)

But transmitted flux is pertinent to concentrating solar, including both the smelting ore and solar thermal power. Electric induction heating is looking better and better. Far from "complicating your supply chain further," electric smelting is far simpler as it avoids the need for high-precision Sun tracking (heavy and high maintenance), and it's more reliable given Mars's dusty atmosphere.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 03/30/2020 05:02 pm
...

BTW, I find it very comic-villainesque to look at potential clean fusion reactor and think "Elon should invest, perfect for Mars base" while not considering the US$ 6 trillion global energy sector ;)
That's how Elon works. I think his top priority is Mars, where he needed electric cars,solar power

I've heard his claim more times than I can count, and it's always struck me as wishful thinking. To believe that, you have to consistently ignore the reason Elon has given every time he's been asked this question for over a decade now: "to accelerate the transition to sustainable transport/energy in order to mitigate the impact of climate change."

Will electic cars help on Mars? Hell yes. Are they the primary reason he's working on Tesla? Is everything he does nothing but a long game for Mars colonization? Hell no, unless Elon has been outright lying literally for years about his motivations. That's getting into conspiracy theory territory.
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 03/30/2020 05:15 pm
...

BTW, I find it very comic-villainesque to look at potential clean fusion reactor and think "Elon should invest, perfect for Mars base" while not considering the US$ 6 trillion global energy sector ;)
That's how Elon works. I think his top priority is Mars, where he needed electric cars,solar power

I've heard his claim more times than I can count, and it's always struck me as wishful thinking. To believe that, you have to consistently ignore the reason Elon has given every time he's been asked this question for over a decade now: "to accelerate the transition to sustainable transport/energy in order to mitigate the impact of climate change."

Will electic cars help on Mars? Hell yes. Are they the primary reason he's working on Tesla? Is everything he does nothing but a long game for Mars colonization? Hell no, unless Elon has been outright lying literally for years about his motivations. That's getting into conspiracy theory territory.
Mars colonization and support for the terrestrial transition to clean energy are both in themselves subordinate goals.  The Primary Main Objective is to Destroy the Evil Power safeguard the future of human civilization.  Tesla is about mitigating an existential threat to civilization on Earth.  Mars colonization is to provide humanity a backup site should something bad happen here, but Earth will always be the home world, at least for the foreseeable future. 
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 03/30/2020 05:47 pm
...

BTW, I find it very comic-villainesque to look at potential clean fusion reactor and think "Elon should invest, perfect for Mars base" while not considering the US$ 6 trillion global energy sector ;)
That's how Elon works. I think his top priority is Mars, where he needed electric cars,solar power

I've heard his claim more times than I can count, and it's always struck me as wishful thinking. To believe that, you have to consistently ignore the reason Elon has given every time he's been asked this question for over a decade now: "to accelerate the transition to sustainable transport/energy in order to mitigate the impact of climate change."

Will electic cars help on Mars? Hell yes. Are they the primary reason he's working on Tesla? Is everything he does nothing but a long game for Mars colonization? Hell no, unless Elon has been outright lying literally for years about his motivations. That's getting into conspiracy theory territory.
Mars colonization and support for the terrestrial transition to clean energy are both in themselves subordinate goals.  The Primary Main Objective is to Destroy the Evil Power safeguard the future of human civilization.  Tesla is about mitigating an existential threat to civilization on Earth.  Mars colonization is to provide humanity a backup site should something bad happen here, but Earth will always be the home world, at least for the foreseeable future.

Indeed, well put. Colbourne was instead suggesting that all his companies were subordinate to the goal of colonizing Mars.
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 03/31/2020 12:03 am
There's some parallel work on getting CO2 power cycle systems (turbines, HX, etc) matured with kilopower, which is nice due to high reject temperatures, and for mars, it's easy to supplement the system. Very compact power cycle, provided your heat source is also fairly hot.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 03/31/2020 01:15 am
Westinghouse web page on the eVinci reactor mentioned above.  Slightly less power but still substantial.

https://www.westinghousenuclear.com/new-plants/evinci-micro-reactor (https://www.westinghousenuclear.com/new-plants/evinci-micro-reactor)


https://www.westinghousenuclear.com/Portals/0/new%20plants/evincitm/eVinci%20Micro%20Reactor%20NPJ%20M-A%202019.pdf?ver=2019-04-30-211410-367 (https://www.westinghousenuclear.com/Portals/0/new%20plants/evincitm/eVinci%20Micro%20Reactor%20NPJ%20M-A%202019.pdf?ver=2019-04-30-211410-367)

Build & demo by 2023
You are aware this is  basically the big brother of Kilopower that Westinghouse have licensed from Los Alamos right?

I guess Toshibas 4S design must have taught them something about the market for these units.

Of course A solid core small reactor with heat pipe energy extraction could have been built anytime from the early 80's (or possibly earlier) had anyone been interested.  :(

Megapower is obviously much better sized to run the ISRU task. Keep in mind to run an ISRU plant for one  SS to refuel between launch windows back to earth is about 1MW continuously.

So to refuel the SS fleet will take a fleet of these to match.

The upside is with Martian temperatures there is so such thing as "waste" heat.

I thought the megawatt per ship was based on solar and resulted from actually needing a farm to average ~.5MW over two years. If I’ve got it wrong stop reading. What follows is drivel.

The interval between arrival and departure is more like 18 months. One Megapower should be able to refuel ~1.5 ships doing a turnaround - before optimizing to incorporate residual heat into the process.

I’d WAG that an optimized system could refuel two ships during the turnaround and make one more ships worth while waiting for the next cycle.

This opens up possibilities. AIUI there are slow returns that need less fuel and can leave at odd times. Plus all the other uses for methane that don’t seem practical if solar is used to make it.

Storing LCH4 for any length of time either costs energy or it evaporates. At some point it makes sense to use it.

Phil
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 03/31/2020 01:36 am
Westinghouse web page on the eVinci reactor mentioned above.  Slightly less power but still substantial.

https://www.westinghousenuclear.com/new-plants/evinci-micro-reactor (https://www.westinghousenuclear.com/new-plants/evinci-micro-reactor)


https://www.westinghousenuclear.com/Portals/0/new%20plants/evincitm/eVinci%20Micro%20Reactor%20NPJ%20M-A%202019.pdf?ver=2019-04-30-211410-367 (https://www.westinghousenuclear.com/Portals/0/new%20plants/evincitm/eVinci%20Micro%20Reactor%20NPJ%20M-A%202019.pdf?ver=2019-04-30-211410-367)

Build & demo by 2023
You are aware this is  basically the big brother of Kilopower that Westinghouse have licensed from Los Alamos right?

I guess Toshibas 4S design must have taught them something about the market for these units.

Of course A solid core small reactor with heat pipe energy extraction could have been built anytime from the early 80's (or possibly earlier) had anyone been interested.  :(

Megapower is obviously much better sized to run the ISRU task. Keep in mind to run an ISRU plant for one  SS to refuel between launch windows back to earth is about 1MW continuously.

So to refuel the SS fleet will take a fleet of these to match.

The upside is with Martian temperatures there is so such thing as "waste" heat.


There are no final specs on Megapower. The target is 40 tons (probably US), and fit into a standard shipping container. What I haven’t seen is a target price. Is that out there anywhere?


Phil



Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 03/31/2020 12:08 pm
Plus all the other uses for methane that don’t seem practical if solar is used to make it.

And what, precisely, would those be?

Methane is methane. Electicity is electricity. They're both fungible. Any application that "seems" possible with nuclear is also possible with solar, and any differential exists solely in the mind of the "seemer."
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/02/2020 05:24 pm
Plus all the other uses for methane that don’t seem practical if solar is used to make it.

And what, precisely, would those be?

Methane is methane. Electicity is electricity. They're both fungible. Any application that "seems" possible with nuclear is also possible with solar, and any differential exists solely in the mind of the "seemer."

I was getting at the point that using solar to make methane to power something is less efficient in some ways than direct solar power and batteries. Conversion losses, system efficiency etc. Note: efficiency comes in many forms. I’m only addressing one kind of efficiency.

If the methane is surplus from some process (nuke powered props production in this case), use for something like an APU or ground transport makes sense. It makes less sense to oversized a solar farm and props production, especially in the early days, for contingency use.

Also, unspoken, ISTM that if possible, the props plant and nuke power supply should be a nearly turnkey solution built into one ship. If this is possible, tying props production into the base grid can wait until higher priority work allows. This in turn allows props production to be some distance from the base and also reduces the solar farm size needed for immediate use.

Phil
Title: Re: Power options for a Mars settlement
Post by: spacenut on 04/02/2020 06:14 pm
Excess methane can have more hydrocarbon chains added to make other hydrocarbons and eventually plastics for use on Mars.  Thus building a chemical industry on Mars.
Title: Re: Power options for a Mars settlement
Post by: Eka on 04/02/2020 08:17 pm
I've heard his claim more times than I can count, and it's always struck me as wishful thinking. To believe that, you have to consistently ignore the reason Elon has given every time he's been asked this question for over a decade now: "to accelerate the transition to sustainable transport/energy in order to mitigate the impact of climate change."

Will electric cars help on Mars? Hell yes. Are they the primary reason he's working on Tesla? Is everything he does nothing but a long game for Mars colonization? Hell no, unless Elon has been outright lying literally for years about his motivations. That's getting into conspiracy theory territory.
The one time I talked with EM, we talked some about wanting to make electric vehicles. I don't remember who brought it up, but global warming was part of the reason why we were both interested in EVs. That was as he was looking for rocket scientists for SpaceX, back in the early 2000s.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/03/2020 03:14 pm

If the methane is surplus from some process (nuke powered props production in this case), use for something like an APU or ground transport makes sense. It makes less sense to oversized a solar farm and props production, especially in the early days, for contingency use.

But why?? You're begging the question here, by nakedly asserting "it makes less sense." No real reasoning for why nuke > solar is contained therein.

I can equally say "if the methane is surplus from some process (solar powered prop production in this case), use for something like an APU or ground transport makes sense." See? The sentence works just as well.


Also, unspoken, ISTM that if possible, the props plant and nuke power supply should be a nearly turnkey solution built into one ship. If this is possible, tying props production into the base grid can wait until higher priority work allows. This in turn allows props production to be some distance from the base and also reduces the solar farm size needed for immediate use.

The nuke plant will need a large radiator area, so building a "turnkey" system into the ship is problematic. Either the power output will be very limited (and even then, you'd need to extensively modify Starship's fuselage to double as the radiator), or it won't be simply "turnkey."

Also, by putting the reactor and the prop production on a single ship you're reducing the scale, which is likely to reduce the mass efficiency of both systems.
Title: Re: Power options for a Mars settlement
Post by: philw1776 on 04/03/2020 03:48 pm
Always been interested in nukes as a steady state source for Mars colonies.  However, solar is likely the best approach overall despite its lack of constant sourcing, nights, seasons (latitude) & sandstorms.  An overbuilt solar field is more anti-fragile, compared to nuke(s).  Several unrelated failure modes could take out a nuke, but a solar field attended by humans should be either repairable or at least would not as likely fail to zero output with repairs a long time coming.
Title: Re: Power options for a Mars settlement
Post by: hoardsbane on 04/03/2020 03:49 pm

If the methane is surplus from some process (nuke powered props production in this case), use for something like an APU or ground transport makes sense. It makes less sense to oversized a solar farm and props production, especially in the early days, for contingency use.

But why?? You're begging the question here, by nakedly asserting "it makes less sense." No real reasoning for why nuke > solar is contained therein.

I can equally say "if the methane is surplus from some process (solar powered prop production in this case), use for something like an APU or ground transport makes sense." See? The sentence works just as well.


Also, unspoken, ISTM that if possible, the props plant and nuke power supply should be a nearly turnkey solution built into one ship. If this is possible, tying props production into the base grid can wait until higher priority work allows. This in turn allows props production to be some distance from the base and also reduces the solar farm size needed for immediate use.

The nuke plant will need a large radiator area, so building a "turnkey" system into the ship is problematic. Either the power output will be very limited (and even then, you'd need to extensively modify Starship's fuselage to double as the radiator), or it won't be simply "turnkey."

Also, by putting the reactor and the prop production on a single ship you're reducing the scale, which is likely to reduce the mass efficiency of both systems.

Rejecting heat may not be a major issue given for any of this to work we are going to be processing a large amount of ice as water ...
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/03/2020 03:58 pm

Rejecting heat may not be a major issue given for any of this to work we are going to be processing a large amount of ice as water ...

Unless you want to shut down power production when the mine goes down, you'll need a contingency heatsink.
Title: Re: Power options for a Mars settlement
Post by: randomly on 04/03/2020 06:20 pm
Don't forget Mars does have an atmosphere. If you had 4 chimney stacks 9 meters in diameter (a golden number) with 20 meter/sec flow rate you could dissipate 10 MW of heat with an exhaust temperature of something around 80 C.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/03/2020 08:20 pm
Don't forget Mars does have an atmosphere. If you had 4 chimney stacks 9 meters in diameter (a golden number) with 20 meter/sec flow rate you could dissipate 10 MW of heat with an exhaust temperature of something around 80 C.

All a chimney does is convert temperature difference into fluid flow, via the stack effect (https://en.wikipedia.org/wiki/Stack_effect#Induced_flow); you still need a heat exchanger to actually transfer heat to the atmospheric gases. For an inlet temperature of -60 °C, to reach 20 m/s you'd need a stack 275 meters high! And that doesn't even account for the much larger pressure drop through your heat exchanger.

Also, there's a problem with your math. I calculate that you'd need a >500 K temperature difference to achieve those numbers, which is clearly impossible (your inlet temperature would be below absolute zero). Assuming instead a 140 K temperature rise, you'd need at least 15 heat exchangers with that size and flow rate, not four.

Mars atmospheric density = 0.02 kg/m3 https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

Mars atmospheric specific heat = 191.8 J/kg/K http://www.aerospaceweb.org/question/atmosphere/q0249.shtml
Title: Re: Power options for a Mars settlement
Post by: randomly on 04/03/2020 09:48 pm
Yes I'm aware of the stack effect. I was just trying to get a sense of scale of flow rate needed to dissipate 10MW, thus the rough estimate of 4 chimneys. You may need more/bigger chimneys due to lower flow rates from the flow restrictions of the internal heat exchangers, you may need to assist the convection flow with fans. However it is certainly within practical limits, especially compared to pure radiative cooling.

However I think my math isn't as far off as you think.
You're 191.8 J/kg/K is the specific gas constant, not the specific heat constant.
Specific Heat Constant of CO2 is around 800J/kg/K in that temperature range.
https://www.engineeringtoolbox.com/carbon-dioxide-d_974.html

There is certainly substantial potential for using convective cooling on Mars, despite the low atmospheric pressure.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/04/2020 01:31 am
Ahh, thanks for the correction. That's why I always show my assumptions.

I presume an actual drafted chimney won't be used given the mass penalty. Forced air only is my bet.

What did you assume for the inlet/ambient air temperature? Edit: looks like around -40 °C.
Title: Re: Power options for a Mars settlement
Post by: randomly on 04/04/2020 06:52 am
I just used rough numbers to get a sense of scale within a factor of 2 or so. I think it was -60C , but you can push the numbers around to refine it. A forced air augmented chimney radiator for cooling certainly seems plausible. With the low gravity and low wind forces it may be possible to design a relatively low mass system. At any rate it will be much more compact than a purely radiative cooling system.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/04/2020 10:58 am
I just used rough numbers to get a sense of scale within a factor of 2 or so. I think it was -60C , but you can push the numbers around to refine it. A forced air augmented chimney radiator for cooling certainly seems plausible. With the low gravity and low wind forces it may be possible to design a relatively low mass system. At any rate it will be much more compact than a purely radiative cooling system.

Weird, because working backwards from your numbers I get -40 °C. What did you assume for the atmospheric density and specific heat?

Sorry, but I just can't see a "low mass" 1000 foot high chimney. And if you already have the fans anyway, why waste mass on a chimney?

The problem is the low exhaust temperature. Fossil fuel plants use chimneys because they have higher temperature exhausts, and mass is less costly on Earth, and the air is 50x denser, and because it's good to loft pollution high in the air so it dissipates before reaching people at ground level. None of that applies on Mars. Also if it's only a rarely-used contingency system then the power use is less of an inefficiency.
Title: Re: Power options for a Mars settlement
Post by: KSHavre on 04/04/2020 03:04 pm
I just used rough numbers to get a sense of scale within a factor of 2 or so. I think it was -60C , but you can push the numbers around to refine it. A forced air augmented chimney radiator for cooling certainly seems plausible. With the low gravity and low wind forces it may be possible to design a relatively low mass system. At any rate it will be much more compact than a purely radiative cooling system.

Weird, because working backwards from your numbers I get -40 °C. What did you assume for the atmospheric density and specific heat?

Sorry, but I just can't see a "low mass" 1000 foot high chimney. And if you already have the fans anyway, why waste mass on a chimney?

The problem is the low exhaust temperature. Fossil fuel plants use chimneys because they have higher temperature exhausts, and mass is less costly on Earth, and the air is 50x denser, and because it's good to loft pollution high in the air so it dissipates before reaching people at ground level. None of that applies on Mars. Also if it's only a rarely-used contingency system then the power use is less of an inefficiency.

What if the chimney was just a horizontal tube inside a hill, with the fans blowing at the outer end blowing into the tube, that housed a heat exchanger? Any tubes further inside the hill would get pressurized, and be warm...
Title: Re: Power options for a Mars settlement
Post by: randomly on 04/04/2020 03:55 pm
Weird, because working backwards from your numbers I get -40 °C. What did you assume for the atmospheric density and specific heat?

Sorry, but I just can't see a "low mass" 1000 foot high chimney. And if you already have the fans anyway, why waste mass on a chimney?

The problem is the low exhaust temperature. Fossil fuel plants use chimneys because they have higher temperature exhausts, and mass is less costly on Earth, and the air is 50x denser, and because it's good to loft pollution high in the air so it dissipates before reaching people at ground level. None of that applies on Mars. Also if it's only a rarely-used contingency system then the power use is less of an inefficiency.

Obviously a 1000 foot chimney isn't practical, and I wasn't implying that it had to run completely on the chimney effect. It's essentially a dry cooling tower design, forced air augmented but taking advantage of chimney effect to increase efficiency. Given the mass/materials/design constraints it may only be 20-100 meters tall, and 9-30 meters in diameter as a crude guess. I'm not up to optimizing a design, but clearly it's a practical approach.
It's not so much the low exhaust temperature, but the differential temperature of the output vs the ambient temperature that drives the stack effect and you have a low ambient temperature to work with. You can also increase the exhaust temperature to reduce the size of the heat exchangers and chimneys at the cost of some thermal efficiency in your power plant, and this would be an important design tradeoff to control size, mass, and cost in an overall design.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/04/2020 09:04 pm
Just use very high rpm fans and a dry cooler.

To compensate for the low density you need high velocity.  This can be achieved with very fast fans.
Fans are more of less volumetric, so the change in velocity is close to the change in volume and eventually mass flow.
The Mars helicopter works at 1900 to 2800 rpm.
I guess you would require more fan energy since in e=1/2mv2 the mass goes down linearly but the velocity is to the square...
while e=m*cp*dt for the heat transfer    where m=Q*v.  So that part is linear.


Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/04/2020 10:20 pm

If the methane is surplus from some process (nuke powered props production in this case), use for something like an APU or ground transport makes sense. It makes less sense to oversized a solar farm and props production, especially in the early days, for contingency use.

But why?? You're begging the question here, by nakedly asserting "it makes less sense." No real reasoning for why nuke > solar is contained therein.

I can equally say "if the methane is surplus from some process (solar powered prop production in this case), use for something like an APU or ground transport makes sense." See? The sentence works just as well.


Also, unspoken, ISTM that if possible, the props plant and nuke power supply should be a nearly turnkey solution built into one ship. If this is possible, tying props production into the base grid can wait until higher priority work allows. This in turn allows props production to be some distance from the base and also reduces the solar farm size needed for immediate use.

The nuke plant will need a large radiator area, so building a "turnkey" system into the ship is problematic. Either the power output will be very limited (and even then, you'd need to extensively modify Starship's fuselage to double as the radiator), or it won't be simply "turnkey."

Also, by putting the reactor and the prop production on a single ship you're reducing the scale, which is likely to reduce the mass efficiency of both systems.

As I said earlier, efficiency takes many forms. For the earliest synods operational efficiency will be important. ISTM a near turnkey (please don’t quibble the term) nuke powered ISRU would allow easier setup and operation. There’s a lot of work to be done. The easier it is, the more can be done.

Also note: Each StarShip comes with exactly one Starships worth of tankage. I will admit to this being naked unsupported assertion. To my knowledge nobody has ever measured the tankage of a StarShip after landing on Mars.

The Sabatier process itself is exothermic but a lot of ice needs to be melted and if electrolysis is used it is more efficient at high temperature. If there is still heat left to be gotten rid of there are tertiary methods for generating more power.

There may be some level of waste heat after all this requiring a radiator but I would expect it to be very modest. On the other hand there may not be enough heat without further supplementation. I blatantly have no numbers either way. Feel free to choose which one you prefer and lambast me for not adequately supporting the other.

You nakedly assert “Also, by putting the reactor and the prop production on a single ship you're reducing the scale, which is likely to reduce the mass efficiency of both systems.”  You offer no real reasoning as to why. Even if true (unknown) you offer no reasoning for favoring mass efficiency over operational efficiency.

I hope this will be the last confrontational post I ever have to make on NSF.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/04/2020 10:23 pm
Always been interested in nukes as a steady state source for Mars colonies.  However, solar is likely the best approach overall despite its lack of constant sourcing, nights, seasons (latitude) & sandstorms.  An overbuilt solar field is more anti-fragile, compared to nuke(s).  Several unrelated failure modes could take out a nuke, but a solar field attended by humans should be either repairable or at least would not as likely fail to zero output with repairs a long time coming.

They both have strengths and weaknesses. ISTM they can be complementary. Belt and suspenders.

Phil
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/05/2020 09:26 pm
I just used rough numbers to get a sense of scale within a factor of 2 or so. I think it was -60C , but you can push the numbers around to refine it. A forced air augmented chimney radiator for cooling certainly seems plausible. With the low gravity and low wind forces it may be possible to design a relatively low mass system. At any rate it will be much more compact than a purely radiative cooling system.

Weird, because working backwards from your numbers I get -40 °C. What did you assume for the atmospheric density and specific heat?

Sorry, but I just can't see a "low mass" 1000 foot high chimney. And if you already have the fans anyway, why waste mass on a chimney?

The problem is the low exhaust temperature. Fossil fuel plants use chimneys because they have higher temperature exhausts, and mass is less costly on Earth, and the air is 50x denser, and because it's good to loft pollution high in the air so it dissipates before reaching people at ground level. None of that applies on Mars. Also if it's only a rarely-used contingency system then the power use is less of an inefficiency.

What if the chimney was just a horizontal tube inside a hill, with the fans blowing at the outer end blowing into the tube, that housed a heat exchanger? Any tubes further inside the hill would get pressurized, and be warm...

"Chimneys" must be vertical (or at least, have a height change) to work, because they rely on the fact that hot air rises. What you describe is called an earth tube (mars tube?).
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/05/2020 09:34 pm
Just use very high rpm fans and a dry cooler.

To compensate for the low density you need high velocity.  This can be achieved with very fast fans.
Fans are more of less volumetric, so the change in velocity is close to the change in volume and eventually mass flow.
The Mars helicopter works at 1900 to 2800 rpm.
I guess you would require more fan energy since in e=1/2mv2 the mass goes down linearly but the velocity is to the square...
while e=m*cp*dt for the heat transfer    where m=Q*v.  So that part is linear.

"More fans" = make the heat exchanger bigger.

You have fortuitously stumbled on a phenomenon called "propulsive efficiency." A large fan moving a larger mass of air more slowly is more efficient (in a propeller or a heat exchanger) than a small fan moving fast. https://en.wikipedia.org/wiki/Propulsive_efficiency
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/05/2020 09:56 pm

If the methane is surplus from some process (nuke powered props production in this case), use for something like an APU or ground transport makes sense. It makes less sense to oversized a solar farm and props production, especially in the early days, for contingency use.

But why?? You're begging the question here, by nakedly asserting "it makes less sense." No real reasoning for why nuke > solar is contained therein.

I can equally say "if the methane is surplus from some process (solar powered prop production in this case), use for something like an APU or ground transport makes sense." See? The sentence works just as well.


Also, unspoken, ISTM that if possible, the props plant and nuke power supply should be a nearly turnkey solution built into one ship. If this is possible, tying props production into the base grid can wait until higher priority work allows. This in turn allows props production to be some distance from the base and also reduces the solar farm size needed for immediate use.

The nuke plant will need a large radiator area, so building a "turnkey" system into the ship is problematic. Either the power output will be very limited (and even then, you'd need to extensively modify Starship's fuselage to double as the radiator), or it won't be simply "turnkey."

Also, by putting the reactor and the prop production on a single ship you're reducing the scale, which is likely to reduce the mass efficiency of both systems.

As I said earlier, efficiency takes many forms. For the earliest synods operational efficiency will be important. ISTM a near turnkey (please don’t quibble the term) nuke powered ISRU would allow easier setup and operation. There’s a lot of work to be done. The easier it is, the more can be done.

Given the schedule lead times required for new nuclear power designs, and Elon's aggressive timeline, I think I can safely say that there is zero chance that the "earliest synods" will have nuclear power.

Also note: Each StarShip comes with exactly one Starships worth of tankage. I will admit to this being naked unsupported assertion. To my knowledge nobody has ever measured the tankage of a StarShip after landing on Mars.

Very amusing, but to be fair the part I pointed out was a naked assertion. Don't shoot the messenger.

The other option (besides abandoning Starships) is to build in-situ tanks. Bored tunnels lined with insulation comes to mind.

The Sabatier process itself is exothermic but a lot of ice needs to be melted and if electrolysis is used it is more efficient at high temperature. If there is still heat left to be gotten rid of there are tertiary methods for generating more power.

Those "tertiary methods" can also break down, of course. And for such systems your mass efficiency gets lower and lower, just like chaining heat engines together.

There may be some level of waste heat after all this requiring a radiator but I would expect it to be very modest. On the other hand there may not be enough heat without further supplementation. I blatantly have no numbers either way. Feel free to choose which one you prefer and lambast me for not adequately supporting the other.

This new self-[lam]basting technology is really a time-saver. ;)

You nakedly assert “Also, by putting the reactor and the prop production on a single ship you're reducing the scale, which is likely to reduce the mass efficiency of both systems.”  You offer no real reasoning as to why.

Didn't we just spend a bunch of pages discussing how Kilopower/Megapower gets better mass efficiency as it scales up?

Even if true (unknown) you offer no reasoning for favoring mass efficiency over operational efficiency.

What operational efficiency? If you're setting up a large air radiator, running a cable over to the Sabatier Starship is peanuts.


I hope this will be the last confrontational post I ever have to make on NSF.

Let me be the first to welcome you to the forum! :)

The choice of how confrontational to make your posts is entirely your own.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/07/2020 12:46 am
Just use very high rpm fans and a dry cooler.

To compensate for the low density you need high velocity.  This can be achieved with very fast fans.
Fans are more of less volumetric, so the change in velocity is close to the change in volume and eventually mass flow.
The Mars helicopter works at 1900 to 2800 rpm.
I guess you would require more fan energy since in e=1/2mv2 the mass goes down linearly but the velocity is to the square...
while e=m*cp*dt for the heat transfer    where m=Q*v.  So that part is linear.

"More fans" = make the heat exchanger bigger.

You have fortuitously stumbled on a phenomenon called "propulsive efficiency." A large fan moving a larger mass of air more slowly is more efficient (in a propeller or a heat exchanger) than a small fan moving fast. https://en.wikipedia.org/wiki/Propulsive_efficiency
Well lucky me, i'll be stumbling over the fan laws next! 

I updated my spreadsheet on the subject, that I use for cooling habitats, and it's clear the units will be getting larger and heavier on Mars.  The increased convective heat transfer and the increased temperature difference, however, between Mars and Earth might reduce the effect a bit.  I admit I haven't yet tried to work out the increase convective heat transfer from the increased velocity.  The relationships exist though, guess I may try.

Using air for cooling has always been a last resort, really.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/07/2020 09:39 pm
The (Un)mysterious 2007 Power Crisis

we return to LMT's earlier mistake: he said that PV more closely followed transmitted/beam insolation, not total horizotal flux (to quote LMT: "Tau... translates most directly into PV power"). But Paul451 is at least correct on that point: PV indeed more closely follows total horizontal flux (Paul451's number of 67% overestimates power output during the observed 83% drop by a factor of 2), not the transmitted flux (using LMT's theory the number would be 1 - 1/e5, ie a 99.3% drop, which underestimates the power output by a factor of 25). So if LMT thinks Paul451 is "mystified" by the 2007 dust storm, LMT himself must be utterly and completely baffled. Echoing statement secured. :)

No, your combined reasoning doesn't explain the 2007 Opportunity power crisis.  It can't reproduce crisis PV output drop, which remains mysterious only by your text.

Tau jumped roughly from 2.9 (sol 1220) to 4.7 (sol 1235), cutting transmission by 84%.  Hence the 83% drop in daily PV output, and the crisis. 
Title: Re: Power options for a Mars settlement
Post by: MickQ on 04/07/2020 10:03 pm
I thought we were past this.

Can you guys PLEASE take your disagreements to PM and stop clogging up the forum.

Edit/Lar: If you think there are issues, use the "report to mod" button. Self moderation is appreciated but usually report to mod works better.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/07/2020 10:23 pm
Optimal Longitude for PV Power

Is there an optimal longitude for Mars PV power? 

Optimal latitude is obvious: the lower the better.  SpaceX is evaluating sites to ~ 41 N, and ice is abundant at sites down to ~ 30 N (Brough et al. 2019). 

Comparing e.g. 41 N sites with the Phlegra Montes glacier, at 33 N:

- The solar beam flux at 33 N is ~ 8% greater.

- Also, and notably, the storm data (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635) of Kass et al. 2014 indicates ~ 37% fewer storm days at 33 N. 

As for longitude:

Wang and Richardson 2015 tracks large martian storms.  We can look to Fig. 8 (c), and consider storm dust by longitude, keeping in mind the latitude and elevation requirements of a SpaceX base.

Is there an optimal longitude?

Image:  Wang and Richardson 2015, Fig. 8 (c).  "The maximum MGS TES dust optical depth for each 4x5° grid box during Ls ~220–230° in Mars year 24."

Refs.

Brough, S., Hubbard, B. and Hubbard, A., 2019. Area and volume of mid-latitude glacier-like forms on Mars. (https://eprints.ncl.ac.uk/file_store/production/252087/F0614DA4-8EA8-4032-9966-791BE66F7151.pdf) Earth and Planetary Science Letters, 507, pp.10-20.

Kass, D.M., Kleinböhl, A., McCleese, D.J., Schofield, J.T. and Smith, M.D., 2014, January. Observations of large dust storms during the Martian dusty season (http://www-mars.lmd.jussieu.fr/oxford2014/abstracts/kass_dust_oxford2014.pdf). In Proceedings of the 5th International Conference on the Mars Atmosphere. Oxford.

Wang, H. and Richardson, M.I., 2015. The origin, evolution, and trajectory of large dust storms on Mars during Mars years 24–30 (1999–2011). (https://www.cfa.harvard.edu/~hwang/publication/Wang15_dustseq.pdf) Icarus, 251, pp.112-127.
Title: Re: Power options for a Mars settlement
Post by: Shrike DeCil on 04/08/2020 06:38 am
I'd like to mention an idea that doesn't appear to be elsewhere here (Sorry if my searching simply didn't locate it.)
Not as a 'first power' sort of idea, but "Ok, we're always going to be short of power, invest the power we've GOT in making more power!"

It was discarded decades ago for normal space use, because if you have to lift it to LEO already anyway, well, photovoltaics are simply better. (And industrial scale chemical engineering isn't tangent to space missions really.)

But.
If you've got anything, and pretty much anything will do, as a handy source of bulk material, heat pump based solar has VERY low "From Earth Materials" costs. The second aspect that gets this discarded is that wide use requires some how to "dump heat" - it is basically minimally useful on Earth because water vapor is an excellent greenhouse gas. Simple rooftop-solar hot water was only very briefly really competitive. Because the normal chemical engineering ways of cooling things (natural convection, forced convection) avoid  any idea of "radiate directly to space" entirely as silly.
But, the -dryness- of the air is a sizable factor of why Antarctica is so much colder.

I'm not thinking fancy "Solar Power Towers", or even "mirrored surfaces" and the like - I'm talking brute-force "in the sunshine" and "in the shade" parallel pipes. The temperature difference between the two is much higher than on Earth - because low air pressure makes convection vastly less useful, and the low IR absorption means a simple trench -radiates- the heat far more effectively than anything similar here.

Think along the lines of the boring machine digging a surface trench, with all the excavated rubble (that isn't mined for some reason) "just" dumped in mound on the 'mostly sun facing' side of the trench. Run simple made-on-Mars pipes one in a 'never sees the sun' fashion, and the other right out in the 'always sees the sun when up' fashion. The only piece that takes "advanced manufacturing" to make is the actual turbine/pump. And vaguely competent cast/printed/machined/whatever turbines shouldn't be a problem - leaving only the electronic brains to come from Earth.

So:
-a ton of alternators/diodes/chips/etc,
-Ability to dig at scale.
-Process to make pipes. (From compressed rock with glassized layer through processed iron/al/whatever.) Or a 'boring machine like' process to simply dig adequate tunnels that can be called 'pipes'.
- Fluid. (Water, CH4, LOX ...)

Leads to: Provides heat, cooling, and electricity. Note also that the more of your "We need that!" fluids are moving around in circles in pipes ... the less fancy TANKS are needed if that's a problem.

This avoids the normal problems of "exposed electronics", and, while freezing could be a problem, it doesn't have to be a -fatally degrading- problem.
If you want to think of this sort of sideways, this is a type of "geothermal", but you just aren't digging -down-.
As a bonus point, the entire "canals of Mars" business should be geographic features that are "pre dug".
Title: Re: Power options for a Mars settlement
Post by: GregTheGrumpy on 04/08/2020 07:00 am
I'd like to mention an idea that doesn't appear to be elsewhere here <snip>

Welcome to the Forums, Nice first post!
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 04/08/2020 05:10 pm
The temperature difference between the two is much higher than on Earth - because low air pressure makes convection vastly less useful

While this is true, it's worth remembering that "less" doesn't mean "I can ignore this".

I can't find the original source I had for this, but the rough rule of thumb on Mars for sites around datum altitude is that the rate of convective heating/cooling equals the rate of radiative heating/cooling when the airspeed is about 5m/s. Which also happens to be the average wind-speed on Mars.

That means that if there's wind, there won't be as much temperature difference between the hot-side and cold-side of your trench. Which means your heat-pump will be less efficient than you imagine.

Similarly, the "sky temperature" affects radiation efficiency and dust in the air will create a more uniform sky than you imagine, which leads to a more uniform ground temperature. So the higher the dust levels, the more similar will be the temperature of the heat-sink above both the hot and the cold-sides. (Ie, more uniform during high dust levels, less uniform during low dust levels.)

That means that your heat-engine is at greatest efficiency during the times of year when the sky is clear, and there is little wind and no dust storms. It will be worse during storm season, when the sky is full of dust and the winds are higher.

In other words, it will have the same issues as PV-solar, timed exactly when PV production is reduced. And I suspect it will be even more rapidly affected than PV, because of the whole Boltzmann (https://en.wikipedia.org/wiki/Stefan–Boltzmann_law) fourth-power thing with radiators.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/08/2020 06:00 pm
One thing I've been wondering about is the potential high temperatures in summer.  If we design for -40C, that will be fine on average, but is summer, it seems the martian atmosphere can get quite a bit hotter, 20C and such.  So we might have trouble with air cooling, at least in summer days near the equator.
Cooling at night is probably not a problem, if it really always goes down to -70C. 

There might be another alternative there for the heat pump idea, if it can operate somehow over the entire day.
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 04/08/2020 06:40 pm
One thing I've been wondering about is the potential high temperatures in summer.  If we design for -40C, that will be fine on average, but is summer, it seems the martian atmosphere can get quite a bit hotter, 20C and such.  So we might have trouble with air cooling, at least in summer days near the equator.
Cooling at night is probably not a problem, if it really always goes down to -70C. 

There might be another alternative there for the heat pump idea, if it can operate somehow over the entire day.
A reversible heat pump and a large thermal mass, e.g., a big pile of rocks, colony/outpost water reservoir, or for bonus points some sort of phase change material (i.e., water reservoir with ice cubes) could likely shift quite a bit of that mid-day cooling need into the evening.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/08/2020 08:27 pm
Optimal Longitude for PV Power

Is there an optimal longitude for Mars PV power? 

Optimal latitude is obvious: the lower the better.  SpaceX is evaluating sites to ~ 41 N, and ice is abundant at sites down to ~ 30 N (Brough et al. 2019). 

I don't know that that's so obvious. The large eccentricity of Mars's orbit means that the highest minimum solar power latitude is found at ~33° N, not at the equator. No surprise that's where SpaceX chose their landing sites (among other reasons).
Title: Re: Power options for a Mars settlement
Post by: Shrike DeCil on 04/08/2020 09:11 pm
The temperature difference between the two is much higher than on Earth - because low air pressure makes convection vastly less useful
That means that if there's wind, there won't be as much temperature difference between the hot-side and cold-side of your trench. Which means your heat-pump will be less efficient than you imagine.
I'm thinking "Berm-and-trench". The 'heating pipe' in the 'crook' of the sun-facing side of the berm. The cooling pipe in the depth of the trench.  This seems pedantic and weird, but it's how airflow will actually flow in this situation. The air from the "hot side" will ... rise. Or go along with the wind and rise. A trench naturally inhibits airflow to the bottom as opposed to 'across the top'. (Not -prevents-, not saying that!) If the trenches need to be 'long pits' or 'just pits' to inhibit the cross flow fine.
Or: a ... deeper trench.

In other words, it will have the same issues as PV-solar, timed exactly when PV production is reduced.
Sure. Except it doesn't have to be lifted from Earth.
It's a berm. And a ditch. And pipe. Pump/turbine (makable). And no more electronics than any powerplant will need really.

And I suspect it will be even more rapidly affected than PV, because of the whole Boltzmann (https://en.wikipedia.org/wiki/Stefan–Boltzmann_law) fourth-power thing with radiators.
The nearly 100C temperature swings between 'daytime high' and 'nighttime low' at the equator are essentially a direct measure "How much heat is being dumped to space".  Doing the exact calculations gets difficult, because there's a low enough pressure and specific enough chemistries that 'blackbody' isn't adequate. But 100C swings are a firm clue. It's all about the heat flux.

Thinking some more, here's another odd "Not shipped from Earth" powerplant.

Hole. Lid. Turbine-to-atmosphere. Frost forms in the hole every night. Close lid for the day. Boggle. As a bonus, trap the boiling/subliming water so you have more tomorrow.

If the daily fluctuations aren't useful, well, the polar seasonal fluctuations involve enormous phase changes. Phase changes are power that didn't need to be lifted. (And thanks Greg!)
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/08/2020 10:07 pm
Optimal Longitude for PV Power

Is there an optimal longitude for Mars PV power? 

Optimal latitude is obvious: the lower the better.  SpaceX is evaluating sites to ~ 41 N, and ice is abundant at sites down to ~ 30 N (Brough et al. 2019). 

I don't know that that's so obvious. The large eccentricity of Mars's orbit means that the highest minimum solar power latitude is found at ~33° N, not at the equator. No surprise that's where SpaceX chose their landig sites (among other reasons).

- SpaceX hasn't chosen a latitude.
- Min latitude is dictated by ice.
- Summer max PV is not relevant.  If it were, SpaceX would be scouting the southern hemisphere.

Winter min PV and total annual PV are relevant.  Obviously, both are greater at the equator, as seen in a flux plot.  Only lack of ice precludes.

Optimal longitude is less obvious, but Wang and Richardson give suggestive data.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 04/09/2020 07:26 pm
That means that if there's wind, there won't be as much temperature difference between the hot-side and cold-side of your trench.
The nearly 100C temperature swings between 'daytime high' and 'nighttime low' at the equator are essentially a direct measure "How much heat is being dumped to space".

My point was that this maximum diurnal variation is a bad proxy on Mars because a) the daytime sky isn't a good sink, b) air-movement makes the pipes more uniform in temperature, c) the fourth-power issue for radiators¹.

When the air is dusty, the daytime sky scatters sunlight. So the cold-pipe isn't really shadowed, therefore doesn't get anywhere near as cold as it would if you had the same set-up on the Moon. (Where, IMO, it would work brilliantly. And be easier to set up the further you are away from the equator; maybe just a reflective film between hot and cold side? And unlike Mars, you can use solar concentrators, so can drastically increase the hot-side temp for just the "cost" of more reflective thin-film and ISRU wire'n'pegs to hold it up.)

Aside: as an example of this effect, the diurnal variation (https://www-k12.atmos.washington.edu/k12/mars/graphics/VL1_sols_305-335.gif) during high-dust parts of the year is less than half as much as during clear weather.

¹ (In case I wasn't clear before. The amount of energy a radiator of fixed area can dump or absorb (cold/hot side respectively) varies with the fourth power of the temperature. This means that small reduction in the difference between the "sky temperature" on the hot vs cold side results in a large drop in the efficiency of the two radiators, which results in a disproportionate drop in the efficiency of the heat engine. Fourth power is brutal. A 25% reduction in temp give you a 2/3rds loss of efficiency. A 50% reduction gives a 90+% loss...)

Or: a ... deeper trench.

And then the walls of the trench are the primary heat-sink for the cold-side. At which point you might as well just build an earth-tube heat exchanger. Or, as others have suggested, pump absorbed solar-heat into ice that you are mining for ISRU fuel production.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/09/2020 07:42 pm
Optimal Longitude for PV Power

Is there an optimal longitude for Mars PV power? 

Optimal latitude is obvious: the lower the better.  SpaceX is evaluating sites to ~ 41 N, and ice is abundant at sites down to ~ 30 N (Brough et al. 2019). 

I don't know that that's so obvious. The large eccentricity of Mars's orbit means that the highest minimum solar power latitude is found at ~33° N, not at the equator. No surprise that's where SpaceX chose their landig sites (among other reasons).

- SpaceX hasn't chosen a latitude.
- Min latitude is dictated by ice.
- Summer max PV is not relevant.  If it were, SpaceX would be scouting the southern hemisphere.

Winter min PV and total annual PV are relevant.
  Obviously, both are greater at the equator, as seen in a flux plot.  Only lack of ice precludes.

Optimal longitude is less obvious, but Wang and Richardson give suggestive data.

In case you didn't notice, we agree. As I said, "highest minimum [ie winter] solar power."

I understand that SpaceXhas not picked a latitude. As i said, landing "sites." The proposed landing sites are between 35.5 and 40° N. They are clustered in latitude far more than in longitude.

And yes, ice is one of the "other reasons." :)

Thanks for the plot. I misremembered: 33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy between the two. https://arxiv.org/pdf/0903.2688
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/09/2020 08:55 pm
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/10/2020 05:55 pm
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.

Do you have a citation for that (not the "storms trap heat" part, but the part about this being the primary cause of the discrepancy)? I (naively) assumed that it was just plain old thermal lag. It makes a big difference operationally from a planning and forecasting perspective.

Since temperature affects both PV efficiency and nuclear heatsink efficiency and habitat heating requirements, the subject of seasonal temperature variation is hardly off topic.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/10/2020 06:10 pm
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.

Do you have a citation for that (not the "storms trap heat" part, but the part about this being the primary cause of the discrepancy)? I (naively) assumed that it was just plain old thermal lag. It makes a big difference operationally from a planning and forecasting perspective.

Since temperature affects both PV efficiency and nuclear heatsink efficiency and habitat heating requirements, the subject of seasonal temperature variation is hardly off topic.

Weather is not a discrepancy.

Speaking of weather:

- Has anyone spotted an optimal longitude, for a storm break (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066666#msg2066666)?

- Can anyone estimate the storm break's impact on PV power at storm peak?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/11/2020 07:13 pm
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.

Do you have a citation for that (not the "storms trap heat" part, but the part about this being the primary cause of the discrepancy)? I (naively) assumed that it was just plain old thermal lag. It makes a big difference operationally from a planning and forecasting perspective.

Since temperature affects both PV efficiency and nuclear heatsink efficiency and habitat heating requirements, the subject of seasonal temperature variation is hardly off topic.

Weather is not a discrepancy.

No no, you misunderstand. I refer to the aforementioned discrepancy between the highest minimum winter surface horizontal flux latitude (~equatorial) and the highest minimum winter temperature latitude (~33° N).

You claim this discrepancy is due to dust storms, yet I've seen no evidence. Do you have a source, or is this just an assumption?
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/12/2020 05:40 am
Optimal Longitude for PV Power (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066666#msg2066666)

Is there an optimal longitude for Mars PV power? 

--

I'd say optimal northern-hemisphere longitude is shown at 160-165 E, most especially in the low-latitude range of 30-34 N.  There the mountains give a storm break:  a region consistently off the main storm routes (Wang and Richardson 2015, Fig. 6).  Fig. 8c indicates that in that region, at storm peak, a PV panel receives roughly twice the transmitted sunlight of the worst storm longitudes.

Doubled light transmission,
and doubled PV power,
could be important during winter storms.


Other qualifying aspects that downselect optimal longitude:

- There are sites within the storm break region below -2000 m elevation, to meet SpaceX requirement for Starship aerodynamic landing.

- Among those sites, there is at least one possessing a key NASA site factor:  "50 sq km of flat and stable terrain with sparse rock distribution".

- Also, that same site presents a field of useful ice that’s likely a full kilometer thick at center.

Who sees it?

Who believes it?

Refs.

Wang, H. and Richardson, M.I., 2015. The origin, evolution, and trajectory of large dust storms on Mars during Mars years 24–30 (1999–2011). (https://www.cfa.harvard.edu/~hwang/publication/Wang15_dustseq.pdf) Icarus, 251, pp.112-127.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/12/2020 02:28 pm
Who sees it?

Sorry, but it's nearly impossible to me to identify the lon/lat you've described in the attached diagram, since the authors (strangely) failed to include any axis labels or graticule lines on the map. Could you maybe annotate the diagram to point out the region you're describing?

Also, any luck digging up a source? As it stands I'm filing the dust storm explanation in the "wild conjecture" pile, but I'd love to be proven wrong.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/12/2020 02:53 pm
I'm filing the dust storm explanation in the "wild conjecture" pile

Data. (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/12/2020 03:57 pm
I'm filing the dust storm explanation in the "wild conjecture" pile

Data. (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635)

Sadly those data are quite unrelated to my original question.

As a reminder, the question was:
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.

Do you have a citation for that (not the "storms trap heat" part, but the part about this being the primary cause of the discrepancy)? I (naively) assumed that it was just plain old thermal lag. It makes a big difference operationally from a planning and forecasting perspective.

Since temperature affects both PV efficiency and nuclear heatsink efficiency and habitat heating requirements, the subject of seasonal temperature variation is hardly off topic.

Since it seems I'm barking up the wrong tree here, I'll just have to do my own research. Thanks anyway.

Edit: well that was quick! https://arxiv.org/pdf/0903.2688.pdf

Turns out the computer model that reproduces the observed seasonal/latitudinal temperature variation is a simple one that doesn't include dust storms at all, so that explanation is out. It does however include sublimation/deposition of water ice, which would of course be a significant driver of temperature lag. Just like we see on Earth, water and its phase changes have a profound effect on temperature variation!
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/12/2020 05:18 pm
I'm filing the dust storm explanation in the "wild conjecture" pile

Data. (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635)

Sadly those data are quite unrelated to my original question.

As a reminder, the question was:
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.

Do you have a citation for that (not the "storms trap heat" part, but the part about this being the primary cause of the discrepancy)? I (naively) assumed that it was just plain old thermal lag. It makes a big difference operationally from a planning and forecasting perspective.

Since temperature affects both PV efficiency and nuclear heatsink efficiency and habitat heating requirements, the subject of seasonal temperature variation is hardly off topic.

Since it seems I'm barking up the wrong tree here, I'll just have to do my own research. Thanks anyway.

Edit: well that was quick! https://arxiv.org/pdf/0903.2688.pdf

Turns out the computer model that reproduces the observed seasonal/latitudinal temperature variation is a simple one that doesn't include dust storms at all, so that explanation is out. It does however include sublimation/deposition of water ice, which would of course be a significant driver of temperature lag. Just like we see on Earth, water and its phase changes have a profound effect on temperature variation!

No, you linked that before (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2067449#msg2067449), not seeing that sim of mid-latitude heating events requires GCM (https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999JE001024), with storms.  The simpler MAIC-2 model doesn't attempt.

Fig. 4b vs. 4a.

Actual storm heating data (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635) of Kass et al. matches 4b / GCM, of course.

OT.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/12/2020 06:40 pm
I'm filing the dust storm explanation in the "wild conjecture" pile

Data. (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635)

Sadly those data are quite unrelated to my original question.

As a reminder, the question was:
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.

Do you have a citation for that (not the "storms trap heat" part, but the part about this being the primary cause of the discrepancy)? I (naively) assumed that it was just plain old thermal lag. It makes a big difference operationally from a planning and forecasting perspective.

Since temperature affects both PV efficiency and nuclear heatsink efficiency and habitat heating requirements, the subject of seasonal temperature variation is hardly off topic.

Since it seems I'm barking up the wrong tree here, I'll just have to do my own research. Thanks anyway.

Edit: well that was quick! https://arxiv.org/pdf/0903.2688.pdf

Turns out the computer model that reproduces the observed seasonal/latitudinal temperature variation is a simple one that doesn't include dust storms at all, so that explanation is out. It does however include sublimation/deposition of water ice, which would of course be a significant driver of temperature lag. Just like we see on Earth, water and its phase changes have a profound effect on temperature variation!

No, you linked that before (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2067449#msg2067449), not seeing that sim of mid-latitude heating events requires GCM (https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999JE001024), with storms.  The simpler MAIC-2 model doesn't attempt.

Fig. 4b vs. 4a.

Actual storm heating data (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635) of Kass et al. matches 4b / GCM, of course.

OT.

Since the non-GCM model with no dust storms (Figure 4a) also shows the maximum winter temperature at ~33 °N, the effect can't be primarily due to dust storms. Q.E.D. It's primarily temperature lag mediated by water changing phase.

And again, I've already explained why it's on-topic. Mystery solved, no need to waste your time further. However I don't have access to good image editing tools, so annotating that unlabeled map would still be helpful, if you're up to it.  ;D
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/12/2020 10:16 pm
I'm filing the dust storm explanation in the "wild conjecture" pile

Data. (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635)

Sadly those data are quite unrelated to my original question.

As a reminder, the question was:
33° N is the latitude with the highest minimum winter temperature, not flux. Not sure why there's such a discrepancy...

Because storms trap heat.  OT.

Do you have a citation for that (not the "storms trap heat" part, but the part about this being the primary cause of the discrepancy)? I (naively) assumed that it was just plain old thermal lag. It makes a big difference operationally from a planning and forecasting perspective.

Since temperature affects both PV efficiency and nuclear heatsink efficiency and habitat heating requirements, the subject of seasonal temperature variation is hardly off topic.

Since it seems I'm barking up the wrong tree here, I'll just have to do my own research. Thanks anyway.

Edit: well that was quick! https://arxiv.org/pdf/0903.2688.pdf

Turns out the computer model that reproduces the observed seasonal/latitudinal temperature variation is a simple one that doesn't include dust storms at all, so that explanation is out. It does however include sublimation/deposition of water ice, which would of course be a significant driver of temperature lag. Just like we see on Earth, water and its phase changes have a profound effect on temperature variation!

No, you linked that before (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2067449#msg2067449), not seeing that sim of mid-latitude heating events requires GCM (https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999JE001024), with storms.  The simpler MAIC-2 model doesn't attempt.

Fig. 4b vs. 4a.

Actual storm heating data (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635) of Kass et al. matches 4b / GCM, of course.

OT.

Since the non-GCM model with no dust storms (Figure 4a) also shows the maximum winter temperature at ~33 °N, the effect can't be primarily due to dust storms. Q.E.D.

No, you're drawing out an untrue story.  Your Fig. 4a (https://arxiv.org/pdf/0903.2688) gives max northern winter temp as equatorial, plainly and as expected.  You couldn't show otherwise.  That's all.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/13/2020 08:14 pm
...

Since the non-GCM model with no dust storms (Figure 4a) also shows the maximum winter temperature at ~33 °N, the effect can't be primarily due to dust storms. Q.E.D.

No, you're drawing out an untrue story.  Your Fig. 4a (https://arxiv.org/pdf/0903.2688) gives max northern winter temp as equatorial, plainly and as expected.  You couldn't show otherwise.  That's all.

I can't see how you drew that conclusion. In Figure 4a, the 200 K isotherm dips down to ~25° N and up to ~10° S. In Figure 4b the corresponding values are... ~25° N and ~10° S. Ie the north/south distribution of winter coldest temperatures is the same (to within the limitations of the map), as would be expected if the primary mechanism were temperature lag not dust storms. Neither is "equatorial;" they both show a bias toward the northern hemisphere.

Use a ruler on the screen, if that helps. The northern bias is plain as day.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/15/2020 03:58 pm
...

Since the non-GCM model with no dust storms (Figure 4a) also shows the maximum winter temperature at ~33 °N, the effect can't be primarily due to dust storms. Q.E.D.

No, you're drawing out an untrue story.  Your Fig. 4a (https://arxiv.org/pdf/0903.2688) gives max northern winter temp as equatorial, plainly and as expected.  You couldn't show otherwise.  That's all.

I can't see how you drew that conclusion. In Figure 4a, the 200 K isotherm dips down to ~25° N and up to ~10° S. In Figure 4b the corresponding values are... ~25° N and ~10° S. Ie the north/south distribution of winter coldest temperatures is the same (to within the limitations of the map), as would be expected if the primary mechanism were temperature lag not dust storms. Neither is "equatorial;" they both show a bias toward the northern hemisphere.

Use a ruler on the screen, if that helps. The northern bias is plain as day.

Nothing backs your repeated, untrue, "33 N" claim, now wisely omitted.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/15/2020 08:09 pm
...

Since the non-GCM model with no dust storms (Figure 4a) also shows the maximum winter temperature at ~33 °N, the effect can't be primarily due to dust storms. Q.E.D.

No, you're drawing out an untrue story.  Your Fig. 4a (https://arxiv.org/pdf/0903.2688) gives max northern winter temp as equatorial, plainly and as expected.  You couldn't show otherwise.  That's all.

I can't see how you drew that conclusion. In Figure 4a, the 200 K isotherm dips down to ~25° N and up to ~10° S. In Figure 4b the corresponding values are... ~25° N and ~10° S. Ie the north/south distribution of winter coldest temperatures is the same (to within the limitations of the map), as would be expected if the primary mechanism were temperature lag not dust storms. Neither is "equatorial;" they both show a bias toward the northern hemisphere.

Use a ruler on the screen, if that helps. The northern bias is plain as day.

Nothing backs your repeated, untrue, "33 N" claim, now wisely omitted.

Agreed. I can't find the original graph from which I got that number, so it must have been erroneous.

Any progress on annotating that map? Sorry, but I can't really "eyeball" where 160-165° E by 30-34° N is on a map without axes.

If you wanted to be super duper awesome, while you're at it you could label the proposed SpaceX landing sites and the Medusae Fossae Formation.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/22/2020 04:41 pm
...

Since the non-GCM model with no dust storms (Figure 4a) also shows the maximum winter temperature at ~33 °N, the effect can't be primarily due to dust storms. Q.E.D.

No, you're drawing out an untrue story.  Your Fig. 4a (https://arxiv.org/pdf/0903.2688) gives max northern winter temp as equatorial, plainly and as expected.  You couldn't show otherwise.  That's all.

I can't see how you drew that conclusion. In Figure 4a, the 200 K isotherm dips down to ~25° N and up to ~10° S. In Figure 4b the corresponding values are... ~25° N and ~10° S. Ie the north/south distribution of winter coldest temperatures is the same (to within the limitations of the map), as would be expected if the primary mechanism were temperature lag not dust storms. Neither is "equatorial;" they both show a bias toward the northern hemisphere.

Use a ruler on the screen, if that helps. The northern bias is plain as day.

Nothing backs your repeated, untrue, "33 N" claim, now wisely omitted.

Agreed. I can't find the original graph from which I got that number, so it must have been erroneous.

Odd OT posts, Twark_Main.  You ignored your own reference figure, repeatedly, even after I highlighted it.  The figure simply contradicted you; anyone could see that.

Also, there's no "original graph" supporting your abandoned claim, because it's plainly untrue. 

--

Re longitudinal PV optimum (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2068187#msg2068187), see attached.
Title: Re: Power options for a Mars settlement
Post by: wes_wilson on 04/22/2020 05:27 pm
So 1693 posts later, does the below basically summarize the thread?

Power Generation
Solar - Initial missions, early phases, foreseeable future
Nuclear - Growth phases, future, or when government gets involved
ICEs - If needed to run off meth/oxy reserves in emergencies

Power Storage
Batteries
Methane/Oxygen
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/22/2020 11:12 pm
So 1693 posts later, does the below basically summarize the thread?

Power Generation
Solar - Initial missions, early phases, foreseeable future
Nuclear - Growth phases, future, or when government gets involved
ICEs - If needed to run off meth/oxy reserves in emergencies

Power Storage
Batteries
Methane/Oxygen


I’d say that sums it up.
Title: Re: Power options for a Mars settlement
Post by: hoardsbane on 04/23/2020 05:56 am
So 1693 posts later, does the below basically summarize the thread?

Power Generation
Solar - Initial missions, early phases, foreseeable future
Nuclear - Growth phases, future, or when government gets involved
ICEs - If needed to run off meth/oxy reserves in emergencies

Power Storage
Batteries
Methane/Oxygen


I’d say that sums it up.

Agree with the above.  It is very good idea to summarize and focus the discussion!

However, for completeness ...

Have we considered fuel cells as an alternative to ICEs - either direct methane fuel cells https://www.news.gatech.edu/2018/10/29/finally-robust-fuel-cell-runs-methane-practical-temperatures (https://www.news.gatech.edu/2018/10/29/finally-robust-fuel-cell-runs-methane-practical-temperatures) or using stored hydrogen (byproduct of electrolysis)

Under nuclear there are both traditional uranium/plutonium reactors, and potentially thorium based liquid fuel reactors https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor (https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor).  Each has different features and problems.

If there is a significant thermal gradient (shadow vs sunlit surface, surface vs sub-terrain) there is a possibility to extract energy, using a condensing gas or potentially using a Stirling engine (efficient, but maybe not mass efficient) https://en.wikipedia.org/wiki/Stirling_engine (https://en.wikipedia.org/wiki/Stirling_engine).

Finally, there is potential to store energy using an insulated molten salt reservoir, and potentially even generating this hot salt from solar thermal energy using a mirror field https://en.wikipedia.org/wiki/Solar_thermal_energy (https://en.wikipedia.org/wiki/Solar_thermal_energy).

I think it is important to either explicitly exclude these options, or include them.  There may be synergies between them and other energy storage or generation options, or with between them and other required colony processes (mining, food production, fuel production and heating).

I also think that for such a unique situation we shouldn't limit our discussion to the usual (earth based) suspects.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/23/2020 07:57 am
So 1693 posts later, does the below basically summarize the thread?

Power Generation
Solar - Initial missions, early phases, foreseeable future
Nuclear - Growth phases, future, or when government gets involved
ICEs - If needed to run off meth/oxy reserves in emergencies

Power Storage
Batteries
Methane/Oxygen

You'd want to be mindful of triboelectricity, especially martian atmospheric triboelectricity (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048909#msg2048909).  It's easily harvested, and it should peak during the storm conditions that cut PV (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1865539#msg1865539) for weeks or months.

--

And did the reasoning for optimal PV longitude (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2068187#msg2068187) make sense?
Title: Re: Power options for a Mars settlement
Post by: gin455res on 04/23/2020 01:59 pm
This article, https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/ (https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/) in 'The Engineer' claims that Heliogen has used AI to increase the temperature of solar thermal from about 600C to 1000C.  Heliogen is hoping to reach 1500C.


It's not clear to me how the system works from the article. I think it may be computer vision and AI somehow leading to more accurate tracking of the sun for each mirror based on real time observation of the mirrrors, but how exactly?


It is also not clear to me if a) the same temperatures can be reached at Mars - can the disc of the sun be focused more tightly as it subtends a smaller solid angle in the sky, yet it is further away (I think I may have read these two factors cancel out?); b) such high temperatures could be more useful than photovoltaic - enabling direct smelting, glassmaking, ceramics, power, and easier molten salt night-time/duststorm storage options?; and c) this system might be able to simplify the manufacture of the glass needed to make more mirrors, requiring fewer processes in order for the power-source to self-replicate, compared to photovotaics? (or partially self-replicate - how much silver would one need to import? and could aluminium be substituted as a reflective coating, and would Aluminium offer any advantages, or not?).
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/23/2020 04:03 pm
This article, https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/ (https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/) in 'The Engineer' claims that Heliogen has used AI to increase the temperature of solar thermal from about 600C to 1000C.  Heliogen is hoping to reach 1500C.


It's not clear to me how the system works from the article. I think it may be computer vision and AI somehow leading to more accurate tracking of the sun for each mirror based on real time observation of the mirrrors, but how exactly?


It is also not clear to me if a) the same temperatures can be reached at Mars - can the disc of the sun be focused more tightly as it subtends a smaller solid angle in the sky, yet it is further away (I think I may have read these two factors cancel out?); b) such high temperatures could be more useful than photovoltaic - enabling direct smelting, glassmaking, ceramics, power, and easier molten salt night-time/duststorm storage options?; and c) this system might be able to simplify the manufacture of the glass needed to make more mirrors, requiring fewer processes in order for the power-source to self-replicate, compared to photovotaics? (or partially self-replicate - how much silver would one need to import? and could aluminium be substituted as a reflective coating, and would Aluminium offer any advantages, or not?).

Aluminum reflects with a blue bias, silver a  red bias.  That’s from a visual check of telescope mirrors using both coatings. I’m not sure what’s happening in the IR.

Both coatings are soft and delicate. Dust abrasion, even with anemic Martian winds, would ruin them. Two possible solutions. 1) put the coating on the back surface and maybe sandwich a second glass onto the back. 2) sputter a coating of quartz or other material onto the reflective coating.

A back surface coating will diminish any attempt at fine focus as both the coating and the first surface will be reflecting parallel but offset. The thinner the glass, the less the offset. Probably not a problem.

A quartz coating is often used on smaller telescope mirrors as it protects from abrasion and oxidation. Oxidation should not be a problem on Mars. The coating is very thin and would not introduce a noticeable second reflection problem.

Silver is deposited by a chemical process. I’ve read descriptions but the details escape me. I do remember that it didn’t strike me as a particularly benign set of chemicals.

Aluminum is done with vapor deposition. A good roughing pump will take you down to 10e-3 torr, and a molecular pump is then needed to take it down to 10e-5 or better. From there the aluminum is vaporized in a tungsten ‘boat’ with some DC running through it and everything gets shiny.

Which will do the job better?  DIIK.

Phil

Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 04/23/2020 04:29 pm
This article, https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/ (https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/) in 'The Engineer' claims that Heliogen has used AI to increase the temperature of solar thermal from about 600C to 1000C.  Heliogen is hoping to reach 1500C.


It's not clear to me how the system works from the article. I think it may be computer vision and AI somehow leading to more accurate tracking of the sun for each mirror based on real time observation of the mirrrors, but how exactly?


It is also not clear to me if a) the same temperatures can be reached at Mars - can the disc of the sun be focused more tightly as it subtends a smaller solid angle in the sky, yet it is further away (I think I may have read these two factors cancel out?); b) such high temperatures could be more useful than photovoltaic - enabling direct smelting, glassmaking, ceramics, power, and easier molten salt night-time/duststorm storage options?; and c) this system might be able to simplify the manufacture of the glass needed to make more mirrors, requiring fewer processes in order for the power-source to self-replicate, compared to photovotaics? (or partially self-replicate - how much silver would one need to import? and could aluminium be substituted as a reflective coating, and would Aluminium offer any advantages, or not?).

I remember reading about this elsewhere.
As I remember the idea was to use cameras near the focal point of all of the mirrors. Any mirror which was aiming incorrectly would be identified and corrected. Before the responsibility for aiming accuracy was with the individual mirrors.
Basically as you look down from the tower the mirrors shouldn't be aiming at the camera they should be aiming at the focal point. You will see that as a mirror which is brighter than it should be. If you have cameras on four sides you can see the off aimed mirrors.
Title: Re: Power options for a Mars settlement
Post by: gin455res on 04/23/2020 07:31 pm
This article, https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/ (https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/) in 'The Engineer' claims that Heliogen has used AI to increase the temperature of solar thermal from about 600C to 1000C.  Heliogen is hoping to reach 1500C.


It's not clear to me how the system works from the article. I think it may be computer vision and AI somehow leading to more accurate tracking of the sun for each mirror based on real time observation of the mirrrors, but how exactly?


It is also not clear to me if a) the same temperatures can be reached at Mars - can the disc of the sun be focused more tightly as it subtends a smaller solid angle in the sky, yet it is further away (I think I may have read these two factors cancel out?); b) such high temperatures could be more useful than photovoltaic - enabling direct smelting, glassmaking, ceramics, power, and easier molten salt night-time/duststorm storage options?; and c) this system might be able to simplify the manufacture of the glass needed to make more mirrors, requiring fewer processes in order for the power-source to self-replicate, compared to photovotaics? (or partially self-replicate - how much silver would one need to import? and could aluminium be substituted as a reflective coating, and would Aluminium offer any advantages, or not?).

I remember reading about this elsewhere.
As I remember the idea was to use cameras near the focal point of all of the mirrors. Any mirror which was aiming incorrectly would be identified and corrected. Before the responsibility for aiming accuracy was with the individual mirrors.
Basically as you look down from the tower the mirrors shouldn't be aiming at the camera they should be aiming at the focal point. You will see that as a mirror which is brighter than it should be. If you have cameras on four sides you can see the off aimed mirrors.

This is sort of what I imagined but couldn't find any other articles online that went into the details. I thought the target area was smaller than the individual mirrors, which suggests curved mirrors (this might be simpler if the collecting area was on a long rectangle that sits length-wise on a path of constant radius from the tower, rather than a more circular area as shown in the pictures in the article - as this might allow you to get away with a single average radius of curvature for the mirrors. And perhaps this was why it claimed to work at smaller-scales than current systems, ie it isn't approximating a curve with thousands of flat plates)?
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/14/2020 11:07 pm
Mars Surface Solar Arrays: Part 2 (Power Performance) (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170006908.pdf)

Title: Re: Power options for a Mars settlement
Post by: geza on 05/17/2020 12:35 pm
Have we discussed somewhere, how the solar cells will be kept dust-free?
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 05/17/2020 12:48 pm
Have we discussed somewhere, how the solar cells will be kept dust-free?

In a german novel written in 1897 the Martians had their solar energy farms in the highlands to gather more sunlight. Should reduce the dust problems not completely but a lot.
Title: Re: Power options for a Mars settlement
Post by: Ionmars on 05/17/2020 09:42 pm
Have we discussed somewhere, how the solar cells will be kept dust-free?
I think it is earlier in this thread.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/21/2020 08:53 pm
[snip]

Agreed. I can't find the original graph from which I got that number, so it must have been erroneous.

Odd OT posts, Twark_Main. You ignored your own reference figure, repeatedly, even after I highlighted it.  The figure simply contradicted you; anyone could see that.

Also, there's no "original graph" supporting your abandoned claim, because it's plainly untrue. 

I'm struggling to find a point here (beyond a sore winner). Is there anything left to discuss? :-\

Yes it's true, I misremembered a graph I saw years ago. The horror.

--

Re longitudinal PV optimum (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2068187#msg2068187), see attached.

Finally, the annotated map! No sign of the SpaceX landing sites, but it's a start.

Just off the top of my eyeballs, it seems way too close to some seriously dusty areas. One change in the wind patterns and you're buried. Not good Elroy, not good.

Finding the "optimal" place on Mars seems a lot like finding (and having everyone agree on) the "optimal" place on Earth. It's an interesting academic challenge, but I'm not sure how applicable it is to power generation in practice. Ultimately you need a system with multiple technologies that can be "mixed and matched" to deploy anywhere.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/22/2020 01:17 am
This article, https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/ (https://www.theengineer.co.uk/heliogen-the-bill-gates-backed-startup-hoping-to-use-mirrors-to-power-heavy-industry/) in 'The Engineer' claims that Heliogen has used AI to increase the temperature of solar thermal from about 600C to 1000C.  Heliogen is hoping to reach 1500C.


It's not clear to me how the system works from the article. I think it may be computer vision and AI somehow leading to more accurate tracking of the sun for each mirror based on real time observation of the mirrrors, but how exactly?


It is also not clear to me if a) the same temperatures can be reached at Mars - can the disc of the sun be focused more tightly as it subtends a smaller solid angle in the sky, yet it is further away (I think I may have read these two factors cancel out?)

Almost. There is a related principle called conservation of entendue. https://en.wikipedia.org/wiki/Etendue This principle implies that it's impossible to concentrate sunlight and heat a target hotter than the optical temperature of the Sun. But we're nowhere near that limit.

Hard to say if these factors cancel out, but my intuition says no. The halving of intensity means you need twice as many mirrors (a big extra cost), but the Sun's smaller angular size means those panels can (in theory) focus light onto a spot that's half as big. But in practice we use flat mirrors instead of parabolic for ease of manufacturing, so the sharpest achievable focusing spot is no smaller than the mirror size (and the receiver is sized accordingly).

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/22/2020 02:03 am
[snip]

I thought the target area was smaller than the individual mirrors, which suggests curved mirrors (this might be simpler if the collecting area was on a long rectangle that sits length-wise on a path of constant radius from the tower, rather than a more circular area as shown in the pictures in the article - as this might allow you to get away with a single average radius of curvature for the mirrors. And perhaps this was why it claimed to work at smaller-scales than current systems, ie it isn't approximating a curve with thousands of flat plates)?

Can anyone find a source on whether Heliogen uses flat mirrors or parabolic?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/22/2020 02:08 am
Have we discussed somewhere, how the solar cells will be kept dust-free?

One possibility is a self-cleaning electrostatic grid. Very low power.

https://www.sciencedaily.com/releases/2010/08/100822150641.htm

We're still waiting for Back To The Future's "dust repellant paper" though...

Title: Re: Power options for a Mars settlement
Post by: spacexfanatic on 05/26/2020 09:22 am
I was thinking about coupling Starship Raptor engines turbopumps with alternator, this could produce a huge amount of power, including heating from gas exhausts, the SS LOX and CH4 tanks would be used as storage for ISRU production.

Gas turbines are around 33% energy efficienct, but the exhaust heat could be coupled to a steam turbine engine for more effeciency.

I think the system would produce enough energy for an entire outpost base. 
Title: Re: Power options for a Mars settlement
Post by: RonM on 05/26/2020 02:19 pm
I was thinking about coupling Starship Raptor engines turbopumps with alternator, this could produce a huge amount of power, including heating from gas exhausts, the SS LOX and CH4 tanks would be used as storage for ISRU production.

Gas turbines are around 33% energy efficienct, but the exhaust heat could be coupled to a steam turbine engine for more effeciency.

I think the system would produce enough energy for an entire outpost base.

Burning LOX and CH4 to produce more of the same is a losing proposition. Efficiency would have to be over 100% and that's not possible.
Title: Re: Power options for a Mars settlement
Post by: CraigLieb on 05/26/2020 02:50 pm
I was thinking about coupling Starship Raptor engines turbopumps with alternator, this could produce a huge amount of power, including heating from gas exhausts, the SS LOX and CH4 tanks would be used as storage for ISRU production.

Gas turbines are around 33% energy efficienct, but the exhaust heat could be coupled to a steam turbine engine for more effeciency.

I think the system would produce enough energy for an entire outpost base.

Burning LOX and CH4 to produce more of the same is a losing proposition. Efficiency would have to be over 100% and that's not possible.

They could use solar to hydrolyze water to generate hydrogen to burn to produce heat which could be run through a steam engine to run a generator motor to create electricity.... oh.  Wait... 
Title: Re: Power options for a Mars settlement
Post by: spacexfanatic on 05/26/2020 02:57 pm
The problem is how are we gonna  put all the solar panels needed to produce that amount of energy when even in Earth conditions those panels are rated to 20% effeciency, one hectar is only one MW of energy for only the daylight duration.

I think ferrying LOX and CH4 from earth is more energy savvy than sending solar pannels with low energy yield and with low life expectancy.
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 05/26/2020 03:22 pm
The problem is how are we gonna  put all the solar panels needed to produce that amount of energy when even in Earth conditions those panels are rated to 20% effeciency, one hectar is only one MW of energy for only the daylight duration.

I think ferrying LOX and CH4 from earth is more energy savvy than sending solar pannels with low energy yield and with low life expectancy.
So ISRU fuel production is hopeless, and we should haul all fuel from Earth??  We're not going to get very far at that rate ....

ISRU metalox production is fundamental to the whole architecture ... if we cant do that, were not going anywhere anytime soon, and when we do it'll never be more than flags-and-footprints.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/26/2020 03:29 pm
The problem is how are we gonna  put all the solar panels needed to produce that amount of energy when even in Earth conditions those panels are rated to 20% effeciency, one hectar is only one MW of energy for only the daylight duration.

I think ferrying LOX and CH4 from earth is more energy savvy than sending solar panels with low energy yield and with low life expectancy.
Over time, the solar panels will produce much more energy than LOX and CH4 from Earth.  Life expectancy of solar panels is not low.  It's at least a decade, as seen from the existing vehicles on Mars.  If Starship can bring 100 tonnes from Earth, that the limit of the LOX CH4 power.  100 tonnes of combustion.  Solar panels can produce over 1000 tonnes of propellant over two years, for a fraction of the 100 tonnes mass.  Or else the whole in situ idea is absurd ;-)

Another problem is that even a single Starship engine is incredibly over powered for the needs of a Mars Base.  It's Gigawatts of power per engine, after all.  The base will at most require MWatts, and perhaps even KW to operate.  So many thousands of times too powerful.
Finally, rocket engines are designed for a relatively short life.  100 launches of Starship works out to about 15 min x 100 = 25 hours of operation.
Title: Re: Power options for a Mars settlement
Post by: tbellman on 05/26/2020 04:09 pm
I was thinking about coupling Starship Raptor engines turbopumps with alternator, this could produce a huge amount of power, including heating from gas exhausts, the SS LOX and CH4 tanks would be used as storage for ISRU production.

Gas turbines are around 33% energy efficienct, but the exhaust heat could be coupled to a steam turbine engine for more effeciency.

I think the system would produce enough energy for an entire outpost base.

Hooking in to the Raptor turbopumps to attach a generator will not be easy:

* Just attaching something to the turbopump shafts will require serious surgery on the engine.
* The pumps spin at much higher RPMs than you want for a generator, so a gearbox would be needed.  A pretty beefy one at that.
* The turbopumps need to run with very unbalanced CH4/O2 mixes in order to not overheat and be damaged.  Just a few percent of the consumed methane and oxygen would actually be burnt and be used to produce electricity.
* The remaining, unburnt, methane and oxygen will be several hundred °C warm, and be pumped into the main combustion chamber and mixed, and then out through the nozzle.  That exhaust is going to be a major explosion hazard...

If you are going to generate electricity from burning methane and oxygen, a small dedicated gas turbine, or some other kind of combustion engine, is the way to go.


The problem is how are we gonna  put all the solar panels needed to produce that amount of energy when even in Earth conditions those panels are rated to 20% effeciency, one hectar is only one MW of energy for only the daylight duration.

I think ferrying LOX and CH4 from earth is more energy savvy than sending solar pannels with low energy yield and with low life expectancy.

Just returning a single Starship back to Earth, requires at least 600 tonnes of propellant, maybe 800 tonnes.  Assuming a single Starship can transport 150 tonnes of propellant to Mars as cargo, that's 4-5 extra ships.  Ships that will need to be left on Mars.

Robert Zubrin estimated that would require 30,100 m² of solar panels, massing 120 tonnes.  That's just a single Starship load of solar panels.  (I think Zubrin is a bit pessimistic about how heavy panels are, but I'm OK with using his estimates as a first approximation.)  And those panels can be used for 5-10 missions (10-20 years) before they need to be replaced, while your 4-5 tanker ships would be single-use.

There would also be need of equipment for mining ice from the Martian surface, melting it, electrolysing into oxygen and hydrogen, and running the Sabatier reaction.  One more Starship load.  But that is also going to be reusable for 10-20 years.
Title: Re: Power options for a Mars settlement
Post by: sleepy-martian on 05/26/2020 04:40 pm
For solar panel deployment I just started thinking about the principle Domino Trains work at, which could be adapted to autonomously just drop solar panels right next to each other.

But turns out there are actually solar panels on a roll, which can literally be rolled out like a carpet, making autonomous solar deployment very easy.

I think it will  be a goal to have some sort of power generation going already before first humans arrive. That way no matter what should go wrong during the mission, power is guaranteed, and with that tools, communication and mobility.

Also its the first step of any ISRU program, and saying "we've got x MW of power ready for you to plug in next synod" should spur a lot of innovation in that field
Title: Re: Power options for a Mars settlement
Post by: tbellman on 05/26/2020 04:58 pm
But turns out there are actually solar panels on a roll, which can literally be rolled out like a carpet, making autonomous solar deployment very easy.

Elon has mentioned using a technique similar to a party horn (https://en.wikipedia.org/wiki/Party_horn) for unrolling them.  Have tubes along the edges of the panel roll, pump in "air" into them, and the roll will unroll.  Just need to make sure it is not too similar to a party horn, so it doesn't roll together again when you stop the pump.  8)
Title: Re: Power options for a Mars settlement
Post by: sleepy-martian on 05/26/2020 06:43 pm
But turns out there are actually solar panels on a roll, which can literally be rolled out like a carpet, making autonomous solar deployment very easy.

Elon has mentioned using a technique similar to a party horn (https://en.wikipedia.org/wiki/Party_horn) for unrolling them.  Have tubes along the edges of the panel roll, pump in "air" into them, and the roll will unroll.  Just need to make sure it is not too similar to a party horn, so it doesn't roll together again when you stop the pump.  8)

You could either just use a seal to contain pressure (how much bar would be required per meter of solar panel?) or maybe mechanically bend up the edges, sort of how a measuring tape works.

Or just blast some epoxy like material into the tube instead of air which hardens out.
So many options...
Title: Re: Power options for a Mars settlement
Post by: _MECO on 05/27/2020 01:14 am
Have we discussed somewhere, how the solar cells will be kept dust-free?

Periodic EVA where you have a dude with a big broom?
Title: Re: Power options for a Mars settlement
Post by: spacexfanatic on 05/27/2020 03:01 pm
I was thinking about coupling Starship Raptor engines turbopumps with alternator, this could produce a huge amount of power, including heating from gas exhausts, the SS LOX and CH4 tanks would be used as storage for ISRU production.

Gas turbines are around 33% energy efficienct, but the exhaust heat could be coupled to a steam turbine engine for more effeciency.

I think the system would produce enough energy for an entire outpost base.

Hooking in to the Raptor turbopumps to attach a generator will not be easy:

* Just attaching something to the turbopump shafts will require serious surgery on the engine.
* The pumps spin at much higher RPMs than you want for a generator, so a gearbox would be needed.  A pretty beefy one at that.
* The turbopumps need to run with very unbalanced CH4/O2 mixes in order to not overheat and be damaged.  Just a few percent of the consumed methane and oxygen would actually be burnt and be used to produce electricity.
* The remaining, unburnt, methane and oxygen will be several hundred °C warm, and be pumped into the main combustion chamber and mixed, and then out through the nozzle.  That exhaust is going to be a major explosion hazard...

If you are going to generate electricity from burning methane and oxygen, a small dedicated gas turbine, or some other kind of combustion engine, is the way to go.


The problem is how are we gonna  put all the solar panels needed to produce that amount of energy when even in Earth conditions those panels are rated to 20% effeciency, one hectar is only one MW of energy for only the daylight duration.

I think ferrying LOX and CH4 from earth is more energy savvy than sending solar pannels with low energy yield and with low life expectancy.

Just returning a single Starship back to Earth, requires at least 600 tonnes of propellant, maybe 800 tonnes.  Assuming a single Starship can transport 150 tonnes of propellant to Mars as cargo, that's 4-5 extra ships.  Ships that will need to be left on Mars.

Robert Zubrin estimated that would require 30,100 m² of solar panels, massing 120 tonnes.  That's just a single Starship load of solar panels.  (I think Zubrin is a bit pessimistic about how heavy panels are, but I'm OK with using his estimates as a first approximation.)  And those panels can be used for 5-10 missions (10-20 years) before they need to be replaced, while your 4-5 tanker ships would be single-use.

There would also be need of equipment for mining ice from the Martian surface, melting it, electrolysing into oxygen and hydrogen, and running the Sabatier reaction.  One more Starship load.  But that is also going to be reusable for 10-20 years.

I was suggesting the use of raptor engines turbopumps as turbine gas like generator of course with due design modifications in terms of efficiency and reliability while keeping in mind weight and volume saving.it could be useful for power generation during transit, and IMHO it would be necessery for first outpost power generation, and heating habitat as a backup.

I made some quick google search (could be refined) for Mars yearly (365 days) averege solar irradiation which is in best conditions around 1000 KWh per square meter this could make a yield of around 250 KWh with available PV technology per sq2. with a life expectancy of 10 years knowing that yield decrease each year this mean that a square meter of PV can produce 2500 KWh.

1.30 kWh of energy consumption is required for 1 kg of methane production so each PV sq2 will produce 193 kgs/year  (lifespan 1930 kgs) for a weight of between 2 kgs and 4 kgs of PV panels per square meter.

3.42 kWh of energy for 1 Kgs of  O2 which mean 73 Kgs year or 730 Kgs for overall life expectancy for a square meter PV.

Title: Re: Power options for a Mars settlement
Post by: LMT on 05/27/2020 04:18 pm
The turbopumps need to run with very unbalanced CH4/O2 mixes in order to not overheat and be damaged.

Well, the rich ratios feed the Raptor's main combustion chamber.  That's the certain reason.

As for heating, what do you think would constitute and cause damaging preburner overheating here?  Looking at the LOX-rich preburner: 

- Ratio:  The preburner uses a special alloy to manage O2-rich ratio.  Conversely, any gas turbine manages a stoichiometric ratio, without overheating.  Therefore, no ratio in that range should give overheating.

- Feed rate:  The LCH4 feed rate must be limited, to limit combustion energy release, but that's a given.
Title: Re: Power options for a Mars settlement
Post by: ZChris13 on 05/27/2020 11:56 pm
There are better and cheaper options for an APU than cannibalizing and converting a Raptor turbopump
Title: Re: Power options for a Mars settlement
Post by: TommiR on 05/28/2020 06:07 am
I made some quick google search (could be refined) for Mars yearly (365 days) averege solar irradiation which is in best conditions around 1000 KWh per square meter this could make a yield of around 250 KWh with available PV technology per sq2. with a life expectancy of 10 years knowing that yield decrease each year this mean that a square meter of PV can produce 2500 KWh.

1.30 kWh of energy consumption is required for 1 kg of methane production so each PV sq2 will produce 193 kgs/year  (lifespan 1930 kgs) for a weight of between 2 kgs and 4 kgs of PV panels per square meter.

3.42 kWh of energy for 1 Kgs of  O2 which mean 73 Kgs year or 730 Kgs for overall life expectancy for a square meter PV.

Sorry about nitpicking...

You first make really rough estimates on energy but then use higher accuracy in the rest of calculations - you have to use the lowest accuracy presented. Your accuracy should be one number...

Should you consider Martian year (687 earth days) as seasons wary based on those. Because of that energy /day would be better number (ca. 4kWh/m^2/day - some NASA publication. That also compares well to Martian 0,58kW/m^2 solar constant - calculated from Earths 1,36 kW/m^2)

Still sorry about nitpicking... but could not resist
Title: Re: Power options for a Mars settlement
Post by: spacexfanatic on 05/28/2020 08:08 am
I made some quick google search (could be refined) for Mars yearly (365 days) averege solar irradiation which is in best conditions around 1000 KWh per square meter this could make a yield of around 250 KWh with available PV technology per sq2. with a life expectancy of 10 years knowing that yield decrease each year this mean that a square meter of PV can produce 2500 KWh.

1.30 kWh of energy consumption is required for 1 kg of methane production so each PV sq2 will produce 193 kgs/year  (lifespan 1930 kgs) for a weight of between 2 kgs and 4 kgs of PV panels per square meter.

3.42 kWh of energy for 1 Kgs of  O2 which mean 73 Kgs year or 730 Kgs for overall life expectancy for a square meter PV.

Sorry about nitpicking...

You first make really rough estimates on energy but then use higher accuracy in the rest of calculations - you have to use the lowest accuracy presented. Your accuracy should be one number...

Should you consider Martian year (687 earth days) as seasons wary based on those. Because of that energy /day would be better number (ca. 4kWh/m^2/day - some NASA publication. That also compares well to Martian 0,58kW/m^2 solar constant - calculated from Earths 1,36 kW/m^2)

Still sorry about nitpicking... but could not resist

You're welcome, we're here to learn and share ideas.

I made those estimates about solar potential and yield considering irradiations disparities between Mars latitudes and considering PV technologies efficiency ranges, and how this yield changes over the years.
Title: Re: Power options for a Mars settlement
Post by: tbellman on 05/28/2020 08:19 pm
The turbopumps need to run with very unbalanced CH4/O2 mixes in order to not overheat and be damaged.

Well, the rich ratios feed the Raptor's main combustion chamber.  That's the certain reason.

One of the big attractions with the staged combustions cycles over the gas generator cycle, is that you can burn very lean, or very rich, mixtures in the preburner, keeping down the temperatues, without wasting the excess oxidizer or fuel.  But gas generators typically also run quite far from stoichiometric to keep the temperatures down.

For example, the F-1 engine in Saturn V, used a LOX:RP-1 mixture of 0.416:1 in the gas generator, burning at 800°C, and thus didn't need active cooling.  In the main combustion chamber, the mixture was 2.27:1, burning at 3300°C, and active cooling was needed in order to not destroy the engine.


Quote from: LMT
As for heating, what do you think would constitute and cause damaging preburner overheating here?  Looking at the LOX-rich preburner: 

- Ratio:  The preburner uses a special alloy to manage O2-rich ratio.  Conversely, any gas turbine manages a stoichiometric ratio, without overheating.  Therefore, no ratio in that range should give overheating.

Do you have any real-world examples of gas turbines running on something even close to a stoichiometric mixture of methane and pure oxygen, without active cooling?

The vast majority of gas turbines use air, not oxygen.  A stoichiometric mixture of air and methane is only 28% CH4+O2, the rest nitrogen and a little bit of argon.  That nitrogen acts as a "ballast", absorbing lots of the heat energy released by the combustion.  Stoichiometric CH4+air burns at ca 1950°C (constant pressure conditions, and room-temperature CH4 and air).  Stoichiometric CH4+O2 burns significantly hotter.  I'm finding conflicting information about exactly how hot, though, but between 2800°C and 3300°C.

Still, even stoichiometric CH4+air burns way too hot for most materials to withstand.  Even those that don't melt right out, lose a lot of strength, and easily deforms under the stresses in a gas turbine.

A simple solution is to lower the combustion temperature further, by diluting with more air, i.e. burn a fuel-lean mixture.  That is very cheap here on Earth, were air is "everywhere" and costs next to nothing, but it lowers efficiency.  (And while having an excess of hot oxygen around is bad for your metals, the nitrogen diluting the mix makes it not quite as bad as in a rocket engine.)

To allow high combustion temperatures, efficient gas turbines use active cooling, especially of the turbine blades, but also of the the combustion chamber walls.  That cooling is a big driver of complexity, cost and mass, for gas turbines.

As you know, livingjw estimated temperatures of less than 600°C in the Raptor preburners.  That is low enough that you don't need active cooling.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 05/28/2020 08:34 pm
^^^

RPA Lite says for a raptor the temp is 3762K in the combustion chamber
O/F = 3.6
Pc = 30MPa
ER = 34.2

So very hot.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/28/2020 10:36 pm
The vast majority of gas turbines use air, not oxygen.  A stoichiometric mixture of air and methane is only 28% CH4+O2, the rest nitrogen and a little bit of argon.  That nitrogen acts as a "ballast", absorbing lots of the heat energy released by the combustion.  Stoichiometric CH4+air burns at ca 1950°C (constant pressure conditions, and room-temperature CH4 and air).  Stoichiometric CH4+O2 burns significantly hotter.  I'm finding conflicting information about exactly how hot, though, but between 2800°C and 3300°C.

Still, even stoichiometric CH4+air burns way too hot for most materials to withstand...

...livingjw estimated temperatures of less than 600°C in the Raptor preburners.  That is low enough that you don't need active cooling.

Yes, gas turbines use air, and some use coolant, but blades aren't limited to 600 C.  Blades can run above 1300 C.

Image:  Naik 2017, Fig. 4.

If comparable preburner blades exceeded 1300 C in this application, you'd cool with excess LOX.  We could try to estimate any cooling requirement from heat transfer, applying various transfer factors as in Naik 2017.  It's not a simple function of flame temperature.  Most importantly, heat load, rather than flame temperature, sets coolant need.  Reduced LCH4 flow cuts heat load; hence the previous assumption of an LCH4 feed rate limit (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2087378#msg2087378) in an uncooled stoichiometric app.

Refs.

Naik, S., 2017. Basic Aspects of Gas Turbine Heat Transfer. (https://www.intechopen.com/books/heat-exchangers-design-experiment-and-simulation/basic-aspects-of-gas-turbine-heat-transfer)  Heat Exchangers - Design, Experiment and Simulation, pp.111-142.
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 05/29/2020 12:06 am
If comparable preburner blades exceeded 1300 C in this application, you'd cool with excess LOX.
If the concern is slagging down a too-hot gas turbine by running it on pure methane and oxygen, it seems like it would be simpler and overall more efficient to just dilute fuel and/or oxidizer with readily available CO2 (basically the same role N2 plays on earth).
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/29/2020 12:56 am
If comparable preburner blades exceeded 1300 C in this application, you'd cool with excess LOX.

If the concern is slagging down a too-hot gas turbine by running it on pure methane and oxygen, it seems like it would be simpler and overall more efficient to just dilute fuel and/or oxidizer with readily available CO2 (basically the same role N2 plays on earth).

There's no requirement to run at max heat load.  Limiting LCH4 feed rate cuts heat load and lowers preburner surface temperatures, under any ratio, stoichiometric or other. 
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 05/29/2020 07:57 am
If comparable preburner blades exceeded 1300 C in this application, you'd cool with excess LOX.

If the concern is slagging down a too-hot gas turbine by running it on pure methane and oxygen, it seems like it would be simpler and overall more efficient to just dilute fuel and/or oxidizer with readily available CO2 (basically the same role N2 plays on earth).

There's no requirement to run at max heat load.  Limiting LCH4 feed rate cuts heat load and lowers preburner surface temperatures, under any ratio, stoichiometric or other.
Can't they just add a diluent like CO2 to keep the temperature down?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/29/2020 01:40 pm
I made some quick google search (could be refined) for Mars yearly (365 days) averege solar irradiation which is in best conditions around 1000 KWh per square meter this could make a yield of around 250 KWh with available PV technology per sq2. with a life expectancy of 10 years knowing that yield decrease each year this mean that a square meter of PV can produce 2500 KWh.

1.30 kWh of energy consumption is required for 1 kg of methane production so each PV sq2 will produce 193 kgs/year  (lifespan 1930 kgs) for a weight of between 2 kgs and 4 kgs of PV panels per square meter.

3.42 kWh of energy for 1 Kgs of  O2 which mean 73 Kgs year or 730 Kgs for overall life expectancy for a square meter PV.

Sorry about nitpicking...

You first make really rough estimates on energy but then use higher accuracy in the rest of calculations - you have to use the lowest accuracy presented. Your accuracy should be one number...

Should you consider Martian year (687 earth days) as seasons wary based on those. Because of that energy /day would be better number (ca. 4kWh/m^2/day - some NASA publication. That also compares well to Martian 0,58kW/m^2 solar constant - calculated from Earths 1,36 kW/m^2)

Still sorry about nitpicking... but could not resist

You're welcome, we're here to learn and share ideas.

I made those estimates about solar potential and yield considering irradiations disparities between Mars latitudes and considering PV technologies efficiency ranges, and how this yield changes over the years.
So bringing 1 kg of solar panels allows for the production of about 250 kg of methane and about 1000 kg of oxygen, in the worst conditions.  So it's over 1000 times more efficient to carry solar panels than to carry fuel and oxygen, more or less?  And more if the panels actually last a few decades due to proper maintenance.

There is an interesting point raised about combustion of methane and oxygen without buffering nitrogen.  Using CO2 as a nitrogen replacement would also mean that we need to compress it to about 1 atmosphere, so quite a large compression ratio and a large, and presumably heavy, compressor.  The nitrogen acts as a kind of heat exchanger, diluting the energy so the turbines can survive the heat.  This also lowers the maximum system temperature lowering the efficiency of the Carnot cycle.  Something of a moot point if the required turbines cannot exist.  Then we would have an open cycle engine, with the turbine driving a compressor and a generator.  Waste heat would leave with the exhaust gas stream.  Lots of CO2, but also lots of water exhausted
Does a closed loop cycle make sense?  We would need to add a heat exchanger or two, to remove excess heat, but the dilution gas would be the combustion gasses.  We might want to condense out the water and use that for the settlement? Extra CO2 would be vented continuously?  Perhaps not a large savings, as far as the water goes.  Excess heat would heat the settlement, and that part of the system will probably be required anyway.
The point here is for the use of methane as a storage medium for solar energy, for storms and suchlike.  If we do store methane (and oxygen, that is a more of less 'free by product of methane production) what is the best way to extract its energy?
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/29/2020 01:50 pm
If comparable preburner blades exceeded 1300 C in this application, you'd cool with excess LOX.

If the concern is slagging down a too-hot gas turbine by running it on pure methane and oxygen, it seems like it would be simpler and overall more efficient to just dilute fuel and/or oxidizer with readily available CO2 (basically the same role N2 plays on earth).

There's no requirement to run at max heat load.  Limiting LCH4 feed rate cuts heat load and lowers preburner surface temperatures, under any ratio, stoichiometric or other.
Can't they just add a diluent like CO2 to keep the temperature down?

The application has no requirement for excessive heat load, so there's no need for coolant.  Just limit LCH4 flow to limit heat load.

If a heat transfer analysis (https://www.intechopen.com/books/heat-exchangers-design-experiment-and-simulation/basic-aspects-of-gas-turbine-heat-transfer) turned up a persistent hot spot, then the simple, very effective coolant would be excess LOX; but that's not needed unless analysis finds a need.  Stoichiometry / flame temperature discussion doesn't give the analysis.
Title: Re: Power options for a Mars settlement
Post by: Lotick on 05/29/2020 02:58 pm
I made some quick google search (could be refined) for Mars yearly (365 days) averege solar irradiation which is in best conditions around 1000 KWh per square meter this could make a yield of around 250 KWh with available PV technology per sq2. with a life expectancy of 10 years knowing that yield decrease each year this mean that a square meter of PV can produce 2500 KWh.

1.30 kWh of energy consumption is required for 1 kg of methane production so each PV sq2 will produce 193 kgs/year  (lifespan 1930 kgs) for a weight of between 2 kgs and 4 kgs of PV panels per square meter.

3.42 kWh of energy for 1 Kgs of  O2 which mean 73 Kgs year or 730 Kgs for overall life expectancy for a square meter PV.

Sorry about nitpicking...

You first make really rough estimates on energy but then use higher accuracy in the rest of calculations - you have to use the lowest accuracy presented. Your accuracy should be one number...

Should you consider Martian year (687 earth days) as seasons wary based on those. Because of that energy /day would be better number (ca. 4kWh/m^2/day - some NASA publication. That also compares well to Martian 0,58kW/m^2 solar constant - calculated from Earths 1,36 kW/m^2)

Still sorry about nitpicking... but could not resist

You're welcome, we're here to learn and share ideas.

I made those estimates about solar potential and yield considering irradiations disparities between Mars latitudes and considering PV technologies efficiency ranges, and how this yield changes over the years.
So bringing 1 kg of solar panels allows for the production of about 250 kg of methane and about 1000 kg of oxygen, in the worst conditions.  So it's over 1000 times more efficient to carry solar panels than to carry fuel and oxygen, more or less?  And more if the panels actually last a few decades due to proper maintenance.

The efficiency of the panels can be increased with additional mirrors that will increase light intensity on the panel and its power output.

1000 square meters of 100mkm mirror film would weight about 70 kg, Frame made from carbon fiber pipe weight ~100 grams for one square meter frame.  So total ~ 200 kg for 1000 square meters of mirrors.

Also, the mirrors can be focused on sterling engine installation or just on heat exchangers.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/31/2020 08:41 pm
[snip]

The efficiency of the panels can be increased with additional mirrors that will increase light intensity on the panel and its power output.

1000 square meters of 100mkm mirror film would weight about 70 kg, Frame made from carbon fiber pipe weight ~100 grams for one square meter frame.  So total ~ 200 kg for 1000 square meters of mirrors.

Also, the mirrors can be focused on sterling engine installation or just on heat exchangers.

True, but there's a downside. Highly concentrated solar is less reliable on Mars because it relies on beam irradiance (ie only the sunlight coming directly from the Sun), so the power output falls off rapidly when the sky gets dusty. Regular non-concentrating solar panels can use the diffuse light (ie the light scattered by the atmosphere), so they produce more power at higher tau values.

Note I said that this applies to highly concentrated systems (eg parabolic trough, parabolic dish, or tracking mirror arrays). Low concentration systems are another matter: you can easily use non-tracking angled "tent" mirrors to achieve concentration factors of 2-3x, while remaining relatively unaffected by atmospheric dust diffusion.

This applies whether you're doing PV, sterling engines, or solar thermal.

Title: Re: Power options for a Mars settlement
Post by: spacexfanatic on 06/01/2020 11:08 am
I made some quick google search (could be refined) for Mars yearly (365 days) averege solar irradiation which is in best conditions around 1000 KWh per square meter this could make a yield of around 250 KWh with available PV technology per sq2. with a life expectancy of 10 years knowing that yield decrease each year this mean that a square meter of PV can produce 2500 KWh.

1.30 kWh of energy consumption is required for 1 kg of methane production so each PV sq2 will produce 193 kgs/year  (lifespan 1930 kgs) for a weight of between 2 kgs and 4 kgs of PV panels per square meter.

3.42 kWh of energy for 1 Kgs of  O2 which mean 73 Kgs year or 730 Kgs for overall life expectancy for a square meter PV.

Sorry about nitpicking...

You first make really rough estimates on energy but then use higher accuracy in the rest of calculations - you have to use the lowest accuracy presented. Your accuracy should be one number...

Should you consider Martian year (687 earth days) as seasons wary based on those. Because of that energy /day would be better number (ca. 4kWh/m^2/day - some NASA publication. That also compares well to Martian 0,58kW/m^2 solar constant - calculated from Earths 1,36 kW/m^2)

Still sorry about nitpicking... but could not resist

You're welcome, we're here to learn and share ideas.

I made those estimates about solar potential and yield considering irradiations disparities between Mars latitudes and considering PV technologies efficiency ranges, and how this yield changes over the years.
So bringing 1 kg of solar panels allows for the production of about 250 kg of methane and about 1000 kg of oxygen, in the worst conditions.  So it's over 1000 times more efficient to carry solar panels than to carry fuel and oxygen, more or less?  And more if the panels actually last a few decades due to proper maintenance.

There is an interesting point raised about combustion of methane and oxygen without buffering nitrogen.  Using CO2 as a nitrogen replacement would also mean that we need to compress it to about 1 atmosphere, so quite a large compression ratio and a large, and presumably heavy, compressor.  The nitrogen acts as a kind of heat exchanger, diluting the energy so the turbines can survive the heat.  This also lowers the maximum system temperature lowering the efficiency of the Carnot cycle.  Something of a moot point if the required turbines cannot exist.  Then we would have an open cycle engine, with the turbine driving a compressor and a generator.  Waste heat would leave with the exhaust gas stream.  Lots of CO2, but also lots of water exhausted
Does a closed loop cycle make sense?  We would need to add a heat exchanger or two, to remove excess heat, but the dilution gas would be the combustion gasses.  We might want to condense out the water and use that for the settlement? Extra CO2 would be vented continuously?  Perhaps not a large savings, as far as the water goes.  Excess heat would heat the settlement, and that part of the system will probably be required anyway.
The point here is for the use of methane as a storage medium for solar energy, for storms and suchlike.  If we do store methane (and oxygen, that is a more of less 'free by product of methane production) what is the best way to extract its energy?

To continue with the idea of methane, what about use of the gas turbine in a greenhouse? plants will provide oxygen and the turbine will generate CO2 and heat.

Lets do the math:

1 cubic meter of air weight 1.3 Kgs

GE MS9001 gas turbine with 256 MW of power capacity have an inlet of 587 Kgs/s or 451 cubic meter/second let scale down the power generation for 1 MW which require 1.7 cubic meter/second or 2.21 Kgs of air per second which mean 70 millions Kgs per year or 70.000 tons of air.

Knowing that 1 Kgs of air is 230 grams of oxygen, our 1 MW gas turbine will need 16.100 tons of oxygen.

I was thinking about using high biomass yielding Hydroponic farming wich could produce 1 tons of biomass day for each 20 square meter daily,  meaning 1 tons of oxygen day. this mean 365 tons year.  an area of 1000 meter would be enough to feed oxygen of 1 MW gas turbine, while producing food and biomass that could be recycled.

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/02/2020 03:57 am
To continue with the idea of methane, what about use of the gas turbine in a greenhouse? plants will provide oxygen and the turbine will generate CO2 and heat.

The plants don't help energetically speaking, because you still need the same amount of electrolysis to produce hydrogen for the methane. You might as well simply use the oxygen generated in that electrolysis step.

Title: Re: Power options for a Mars settlement
Post by: spacexfanatic on 06/02/2020 11:31 am
To continue with the idea of methane, what about use of the gas turbine in a greenhouse? plants will provide oxygen and the turbine will generate CO2 and heat.

The plants don't help energetically speaking, because you still need the same amount of electrolysis to produce hydrogen for the methane. You might as well simply use the oxygen generated in that electrolysis step.

This extra Oxygen could be saved and used for others puposes, like refueling SS.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/02/2020 09:06 pm
To continue with the idea of methane, what about use of the gas turbine in a greenhouse? plants will provide oxygen and the turbine will generate CO2 and heat.

The plants don't help energetically speaking, because you still need the same amount of electrolysis to produce hydrogen for the methane. You might as well simply use the oxygen generated in that electrolysis step.

This extra Oxygen could be saved and used for others puposes, like refueling SS.

But Starship also needs methane. Extra oxidizer from photosynthesis doesn't help if you don't have extra methane to go with it.

But here's the kicker: the electrolysis + sabatier process to make methane already makes more oxygen than Starship needs. It produces oxygen and methane at a ratio of 4:1, but Raptor only needs (based on various sources) a mix ratio of between 3.54:1 and 3.8:1. So every time you refill a 1100 tonne Starship for Earth return, you're left with between 46 and 111 tonnes of excess oxygen.

For any combustion use (refueling Starship, APUs, heaters, etc), the critical limiting resource is the methane, not the oxygen. That's why plants don't help.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/06/2020 03:29 pm
A simple solution is to lower the combustion temperature further, by diluting with more air, i.e. burn a fuel-lean mixture.  That is very cheap here on Earth, were air is "everywhere" and costs next to nothing, but it lowers efficiency.  (And while having an excess of hot oxygen around is bad for your metals, the nitrogen diluting the mix makes it not quite as bad as in a rocket engine.)

To allow high combustion temperatures, efficient gas turbines use active cooling, especially of the turbine blades, but also of the the combustion chamber walls.  That cooling is a big driver of complexity, cost and mass, for gas turbines.

As you know, livingjw estimated temperatures of less than 600°C in the Raptor preburners.  That is low enough that you don't need active cooling.
Excellent points.

It's true that for some years now aircraft gas turbines have run blades close to or at the blade alloy melting points.

The engine on the SR71 may have been one of the last to not use active cooling to do this, making it more robust to the very hot incoming air it was dealing with.

But yes running at very high pressures can mean you run at astonishingly low temperatures, which helps a lot.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/06/2020 03:52 pm
A few points for anyone considering a nuclear option.

There has been much talk about using helium to direct drive a gas turbine.

AFAIK the biggest ever helium gas turbine (5MW) was constructed in (west) Germany in1968 for their pebble bed programme. The closest to this was a south Korean sub scale test unit of 2MW in about 2008.

So anyone thinking about a helium turbine of large scale is in for a long development process.
[EDIT Or talk to Reaction Engines Ltd. They are the only people who are committed to designing large GHe turbines right now, but don't bother if you can't put several $m on the table]

CO2 seems a bit closer as there is actual industrial interest in doing this for carbon capture and combustion (turns out under the right condition you can burn CO2. Who knew?). Again this is not an OTS product you can buy. That also is years away.

Lastly enrichment.
Officially Low Enriched Uranium is anything that's under 20% U235. It's only above this that much more serious security restrictions kick in as it's viewed as viable bomb making material.

However digging into the IAEA documents indicates that most enrichment plants that will supply commercially are not rated to 20%. The maximum they can do is 5%.  Above this they need to be re-certified, probably after a complete re-design.  :(

The issue is criticality. At 5% you can process on quite a large scale and not worry (too much) about accidentally creating a critical mass and triggering a nuclear pulse, or outright explosion. This is not an academic exercise. The 40's,50's and 60's had a string of criticality accidents in the US industry which created the Hanford Criticality H&S training course. Several people died as a result. As the manual said "All were preventable."  :(

At the full 20% individual tanks must be much smaller. So you either reduce capacity (because in fact most of your customers don't want 20% enrichment) or you need to have multiple sets of process hardware, each able to run up to 20% without going critical.

Obviously plants that make uranium for weapons have no problem with the full spec 20% stuff, but I don't think they sell commercially.  So anyone thinking "All it takes is one of those sealed-for-life reactor designs I've been reading about" is going to be quite disappointed.
[EDIT One last point about nukes. All reactors breed. The only exceptions would be designs with 100% U235. Anything else will have materials that can breed. Like the 96.5-98% of U238 in LWR fuel. That's why all the stored nuclear fuel rods the US has in cooling ponds (70 million Kg as of 2013) has at least 1% Pu in them, regardless of wheather or not any Plutonium was in the original fuel load. Bred (and partly burnt) in situ. ]
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/06/2020 08:31 pm
Dragging the conversation here.

The question is whether "self sufficiency" means that the colony doesn't deplete planetary resources.

MT drew an equivalence to a space station, where the equivalency exists by definition since there are no such resources...  And further claimed that if you're depleting planetary resources, then it's just a matter of time until you run out and so you're not really self-sufficient.

I'm saying that this is exactly the difference between space stations and planets.  Of course you may eventually mine out the planet, but that's thousands of years away if not more.  You'll probably run out of room to put waste product before you run out of raw resources...  And besides as long as the colony is growing (which again, is hundreds of years at least) then even a fully-recycling colony still has to mine the planet and deplete resources... 

OTOH, I like the definition of self-sufficiency as simply not needed EXTERNAL resources.  That is, you make everything in-situ, including the equipment used to do the resource extraction, and the equipment used to produce power...

And so by far the most important surface capability is not making food, or even fuel (since those can be imported from Earth initially) but making power equipment (since you can't practically import energy). Once you can make solar cells locally, everything else will fall into place.

And before you are able to make solar cells, you can import from Earth just the thin-film active junction layer (at incredible power densities) and make on Mars the substrate sheeting and framing system, which take up like 99% of the mass...

I would say for this reason, a plant that can make outdoor-stable structural plastics from Methane is the #1 goal.  Import laminating equipment, and bring in thin PV film...  There are systems that reach 1 kWatt/kg..  So a single 100 ton payload is 100 MWatt... Pretty much removing the power bottleneck from the equation.

A follow-up computation is how much energy is required to create this substrate, but if that energy cost is higher than a year's worth of production, then solar power is out the window as a power source...  Even 1 year is a lot in this context...




[snip]

If you're mining Iron and Silicon from the planet, you're still self sufficient.
If you're importing them from Earth because you haven't yet developed mining capabilities, you're not.
A self sufficient civilization makes its own mining equipment, but it makes it out of steel made out of iron extracted from the ground.

Your equivalence between a planet and a space station is theoretical. In practical terms, the big obstacle to Mars self sufficiency is having a fully boot-strapped industrial food chain that's based exclusively on local resources.  There's no requirement for not using local resources...

Even if you fully recycle, you still need to extract the resources at least once..  and since Mars will continue to grow from zero to full over a very long period of time, then even if you rwcycle everything, you'll still be mining and exteacting resources like mad..  and still be self-sufficient, since you sure won't be able to import that amount of good from Earth.

You may be self-sufficient, but that has yet to be shown. My main point is that "not importing anything from Earth" doesn't automatically get you there.

Anyway, this dead horse has been beaten enough. The main take-away imo is that choosing "self-sustainance" as the end-point for "settlement" is problematic, since it's such a vague milestone.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/07/2020 12:00 am
Thanks for setting us up in the new thread.

Dragging the conversation here.

The question is whether "self sufficiency" means that the colony doesn't deplete planetary resources.

MT drew an equivalence to a space station, where the equivalency exists by definition since there are no such resources...  And further claimed that if you're depleting planetary resources, then it's just a matter of time until you run out and so you're not really self-sufficient.

I'm saying that this is exactly the difference between space stations and planets.  Of course you may eventually mine out the planet, but that's thousands of years away if not more.

At an exponential growth rate, you'd be surprised how fast it can happen. Most of those "X years remaining" calculations assume constant use, not 3% growth (or whatever).



You'll probably run out of room to put waste product before you run out of raw resources...

Six of one, half dozen of the other. Naturally the weakest link is what breaks first.


And besides as long as the colony is growing (which again, is hundreds of years at least) then even a fully-recycling colony still has to mine the planet and deplete resources...

The catch is, how exactly does the colony go about deciding to stop growing, once the resources are depleted? :-\

Our handling of this issue so far hasn't been great. Our modern economic system demands continuous growth, with painful social consequences if it doesn't happen.

OTOH, I like the definition of self-sufficiency as simply not needed EXTERNAL resources.  That is, you make everything in-situ, including the equipment used to do the resource extraction, and the equipment used to produce power...

Problem is, the definition is incomplete. You can certainly satisfy the "not need external resources" condition, and still fail to be self-sufficient for other reasons.

If Mars is socially unsustainable (highly social inequality) and blows itself up in a civil war, it's not "needing external resources" that made the colony unsustainable. In highly stratified societies it's typically not the quantity of resources that's inadequate, it's the unequal distribution of those resources (so "just add external resources" doesn't help).

And so by far the most important surface capability is not making food, or even fuel (since those can be imported from Earth initially) but making power equipment (since you can't practically import energy). Once you can make solar cells locally, everything else will fall into place.

How can you be sure? We haven't been able to solve these problems terrestrially, and AFAIK being on Mars only makes the problems harder.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/07/2020 12:11 am
Thanks for setting us up in the new thread.

Dragging the conversation here.

The question is whether "self sufficiency" means that the colony doesn't deplete planetary resources.

MT drew an equivalence to a space station, where the equivalency exists by definition since there are no such resources...  And further claimed that if you're depleting planetary resources, then it's just a matter of time until you run out and so you're not really self-sufficient.

I'm saying that this is exactly the difference between space stations and planets.  Of course you may eventually mine out the planet, but that's thousands of years away if not more.

At an exponential growth rate, you'd be surprised how fast it can happen. Most of those "X years remaining" calculations assume constant use, not 3% growth (or whatever).



You'll probably run out of room to put waste product before you run out of raw resources...

Six of one, half dozen of the other. Naturally the weakest link is what breaks first.


And besides as long as the colony is growing (which again, is hundreds of years at least) then even a fully-recycling colony still has to mine the planet and deplete resources...

The catch is, how exactly does the colony go about deciding to stop growing, once the resources are depleted? :-\

Our handling of this issue so far hasn't been great. Our modern economic system demands continuous growth, with painful social consequences if it doesn't happen.

OTOH, I like the definition of self-sufficiency as simply not needed EXTERNAL resources.  That is, you make everything in-situ, including the equipment used to do the resource extraction, and the equipment used to produce power...

Problem is, the definition is incomplete. You can certainly satisfy the "not need external resources" condition, and still fail to be self-sufficient for other reasons.

If Mars is socially unsustainable (highly social inequality) and blows itself up in a civil war, it's not "needing external resources" that made the colony unsustainable. In highly stratified societies it's typically not the quantity of resources that's inadequate, it's the unequal distribution of those resources (so "just add external resources" doesn't help).

And so by far the most important surface capability is not making food, or even fuel (since those can be imported from Earth initially) but making power equipment (since you can't practically import energy). Once you can make solar cells locally, everything else will fall into place.

How can you be sure? We haven't been able to solve these problems terrestrially, and AFAIK being on Mars only makes the problem harder.
You can keep your definition of course, since it's just a definition..

All I'm saying is that the goal of the colony, the thing that makes it independent and able to grow, is the ability to not use imported resources.

You will often hear talk of "self sufficiency" of the colony. Usually, if you examine the context, you'll see that the meaning is as I interpret it..

I'm also saying that the condition of "complete recycling", while it can be stated, is not something the colony needs to achieve..  Mars will not run out of Iron or Silicon...   And if a certain resource is scarce, then of course an attempt will be made to recycle it as much as practical...

As for exponential growth, this only occurs during initial phases. It very quickly gets choked by logistical issues such as transport.. 

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/07/2020 05:55 am
I'm also saying that the condition of "complete recycling", while it can be stated, is not something the colony needs to achieve..  Mars will not run out of Iron or Silicon...   And if a certain resource is scarce, then of course an attempt will be made to recycle it as much as practical...
You're right about the energy issue.  Mars is very energy poor compared to earth. For just pure heat IE to melt stuff concentrated solar is the simplest option, despite the portion of time it will be out of action due to atmospheric haze.
Quote from: meekGee
As for exponential growth, this only occurs during initial phases. It very quickly gets choked by logistical issues such as transport..
No. In economics one definition of recession is 3 quarters with zero or -ve growth (IE contraction) of the economy.

And that growth (or contraction) is not measured against some abstract baseline. It is measured against the last quarters figures. IE it is always exponential over time, but it is a very gradual curve by human standards (at 2% growth it takes 24 years for an economy to double for example).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/07/2020 06:08 am
I'm also saying that the condition of "complete recycling", while it can be stated, is not something the colony needs to achieve..  Mars will not run out of Iron or Silicon...   And if a certain resource is scarce, then of course an attempt will be made to recycle it as much as practical...
You're right about the energy issue.  Mars is very energy poor compared to earth. For just pure heat IE to melt stuff concentrated solar is the simplest option, despite the portion of time it will be out of action due to atmospheric haze.
Quote from: meekGee
As for exponential growth, this only occurs during initial phases. It very quickly gets choked by logistical issues such as transport..
No. In economics one definition of recession is 3 quarters with zero or -ve growth (IE contraction) of the economy.

And that growth (or contraction) is not measured against some abstract baseline. It is measured against the last quarters figures. IE it is always exponential over time, but it is a very gradual curve by human standards (at 2% growth it takes 24 years for an economy to double for example).

And in those 24 years you also have recessions...   
and if the power of the exponent is not constant over time, than while the growth is "exponential", it is also arbitrarily slow, as you indicate..

Context matters, not only semantics.

MT's claim was that because of exponential growth, very quickly the planet's resources will be depleted... 

On Earth, use of resources is only growing meaningfully in developing regions...  Once a region develops, the exponents drops and use of resources trends towards constant (never mind fossil fuels, that's a whole different thing)  Germany and Japan are not using more and more steel in any meaningful way, not when compared say with China.   

Same thing will happen on Mars. The use of resources by the colony will initially explode exponentially, until growth rates slow as the planet develops.  When at steady state, there will be a more or less constant rate of mining, which will take thousands of years to affect the planet's supply of metals or other chemicals.

What WILL happen, however, is that recycling will start early since often it's just plain easier to recover material that's already separated out - it's not like on Earth where so many resources are abundant and recycling had to be shoved into existing industrial processes.  Expect Martians to be very cognizant on what they do with their plastic containers.  I'd say you'll see a lot more reuse than just recycle.  When every ounce of material has been paid for by PV kWatt-hrs...
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/07/2020 06:16 am
And before you are able to make solar cells, you can import from Earth just the thin-film active junction layer (at incredible power densities) and make on Mars the substrate sheeting and framing system, which take up like 99% of the mass...
Just a reminder that Solar City's experience was entirely with rigid single and poly crystal silicon. No thin films.
Quote from: meekGee
I would say for this reason, a plant that can make outdoor-stable structural plastics from Methane is the #1 goal.  Import laminating equipment, and bring in thin PV film...  There are systems that reach 1 kWatt/kg..  So a single 100 ton payload is 100 MWatt... Pretty much removing the power bottleneck from the equation.
For metal smelting 100MW is actually pretty small.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/07/2020 06:23 am
And before you are able to make solar cells, you can import from Earth just the thin-film active junction layer (at incredible power densities) and make on Mars the substrate sheeting and framing system, which take up like 99% of the mass...
Just a reminder that Solar City's experience was entirely with rigid single and poly crystal silicon. No thin films.
Quote from: meekGee
I would say for this reason, a plant that can make outdoor-stable structural plastics from Methane is the #1 goal.  Import laminating equipment, and bring in thin PV film...  There are systems that reach 1 kWatt/kg..  So a single 100 ton payload is 100 MWatt... Pretty much removing the power bottleneck from the equation.
For metal smelting 100MW is actually pretty small.
Indeed, such films are not Solar City's business.

If you had to ship this same amount of PV but with fully encapsulated and outdoor ready panels, it would be 100x the mass.

And yes, you'll need (as you point out) many such payloads, but at the amount of power per payload, power won't dominate all your transport capability ..

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/07/2020 04:54 pm
You can keep your definition of course, since it's just a definition..

How magnanimous. I shall return your magnanimity by informing you that it helps to use definitions that are logically correct, because otherwise your thinking becomes distorted. :)

All I'm saying is that the goal of the colony, the thing that makes it independent and able to grow, is the ability to not use imported resources.

And all I'm saying is, those aren't the same thing, because one is not logically equal to the other.

X = a colony is independent

Y = a colony is able to not use imported resources

X -> Y is always a true statement. If a colony is independent, it must be able to not use imported resources.

Y -> X is not always a true statement. Even if a colony is able to not use imported resources, it isn't necessarily independent.

Am I communicating this clearly?

You will often hear talk of "self sufficiency" of the colony. Usually, if you examine the context, you'll see that the meaning is as I interpret it..

You really have to squint and turn your head to turn everything into a supply issue. It's a very mercantile mindset, really.

I know this will sound crazy, but perhaps the solution isn't always "more." But if all you have is a hammer...

I'm also saying that the condition of "complete recycling", while it can be stated, is not something the colony needs to achieve..  Mars will not run out of Iron or Silicon...

If it's finite, and we demand exponential economic growth, creating an exponentially-growing flow of materials to some unspecified un-recycled material "sink" (which remains mysterious to me), how exactly could it be avoided?

And if a certain resource is scarce, then of course an attempt will be made to recycle it as much as practical...

That makes good fluffy positive-sounding language for a press release, but you have all your work ahead of you to demonstrate that "as much as practical" makes it possible to actually achieve material sustainability.
Title: Re: Power options for a Mars settlement
Post by: dondar on 06/07/2020 05:17 pm
I'm also saying that the condition of "complete recycling", while it can be stated, is not something the colony needs to achieve..  Mars will not run out of Iron or Silicon...   And if a certain resource is scarce, then of course an attempt will be made to recycle it as much as practical...
You're right about the energy issue.  Mars is very energy poor compared to earth. For just pure heat IE to melt stuff concentrated solar is the simplest option, despite the portion of time it will be out of action due to atmospheric haze.
Quote from: meekGee
As for exponential growth, this only occurs during initial phases. It very quickly gets choked by logistical issues such as transport..
No. In economics one definition of recession is 3 quarters with zero or -ve growth (IE contraction) of the economy.

And that growth (or contraction) is not measured against some abstract baseline. It is measured against the last quarters figures. IE it is always exponential over time, but it is a very gradual curve by human standards (at 2% growth it takes 24 years for an economy to double for example).
so your economy has "doubled" in last 24 years. Is it? rhetorical question. It's not that dif
Actually free to point any developed economy which "doubled" in 20 years.
The Netherlands consumes everything (water included) less than 20 years ago. Germany is in x%s as well. Among European countries only Spain had significant consumption growth.
This 3% economy 'growth" requirement lies in the properties of our economy organized around Credit. If your economy doesn't grow financially existing debts and the necessity to cover down-payments strains it ultimately suffocating everything. The requirement of 3 % specifically comes from 65-80% GDP Debt ratio. (depending on how you count it).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/07/2020 05:39 pm
You can keep your definition of course, since it's just a definition..

How magnanimous. I shall return your magnanimity by informing you that it helps to use definitions that are logically correct, because otherwise your thinking becomes distorted. :)

All I'm saying is that the goal of the colony, the thing that makes it independent and able to grow, is the ability to not use imported resources.

And all I'm saying is, those aren't the same thing, because one is not logically equal to the other.

X = a colony is independent

Y = a colony is able to not use imported resources

X -> Y is always a true statement. If a colony is independent, it must be able to not use imported resources.

Y -> X is not always a true statement. Even if a colony is able to not use imported resources, it isn't necessarily independent.

Am I communicating this clearly?

You will often hear talk of "self sufficiency" of the colony. Usually, if you examine the context, you'll see that the meaning is as I interpret it..

You really have to squint and turn your head to turn everything into a supply issue. It's a very mercantile mindset, really.

I know this will sound crazy, but perhaps the solution isn't always "more." But if all you have is a hammer...

I'm also saying that the condition of "complete recycling", while it can be stated, is not something the colony needs to achieve..  Mars will not run out of Iron or Silicon...

If it's finite, and we demand exponential economic growth, creating an exponentially-growing flow of materials to some unspecified un-recycled material "sink" (which remains mysterious to me), how exactly could it be avoided?

And if a certain resource is scarce, then of course an attempt will be made to recycle it as much as practical...

That makes good fluffy positive-sounding language for a press release, but you have all your work ahead of you to demonstrate that "as much as practical" makes it possible to actually achieve material sustainability.

Yup and I'm saying that indeed Y is necessary for independence, but that Z ("Colony doesn't use planetary resources") is neither desired, practical, or will happen.

The main reason is that the colony has to grow from somewhere. As long as it is growing, it needs to either mine the planet, or import. Importing planetary-scale amounts of material is impractical, and so of course it will mine and use planetary resources.

You may be thinking about some future state where the colony occupies the entirety of Mars and is no longer capable of growing (like a hypothetical Earth, but with all developing regions have become developed) but such a state is hundreds if not thousands of years away and so is happening at a very different technological state, complete with solar-system wide resource exploitation, so doesn't fall under any practical current-day consideration.

If that's your claim though, then fine - I do not presume to predict what will happen on such a long time-arc.  I'm talking about what we see in the near future - a growing self-sufficient (in my sense of the word) colony - that's hard enough if a goal.

The rest of the adjectives in your post, I think I'll just not respond to.

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/07/2020 05:57 pm
I'm also saying that the condition of "complete recycling", while it can be stated, is not something the colony needs to achieve..  Mars will not run out of Iron or Silicon...   And if a certain resource is scarce, then of course an attempt will be made to recycle it as much as practical...
You're right about the energy issue.  Mars is very energy poor compared to earth. For just pure heat IE to melt stuff concentrated solar is the simplest option, despite the portion of time it will be out of action due to atmospheric haze.
Quote from: meekGee
As for exponential growth, this only occurs during initial phases. It very quickly gets choked by logistical issues such as transport..
No. In economics one definition of recession is 3 quarters with zero or -ve growth (IE contraction) of the economy.

And that growth (or contraction) is not measured against some abstract baseline. It is measured against the last quarters figures. IE it is always exponential over time, but it is a very gradual curve by human standards (at 2% growth it takes 24 years for an economy to double for example).

And in those 24 years you also have recessions...

And yet the average growth rate remains positive and non-zero.

This is the same reason people (wrongly) cite when they argue against index funds.


and if the power of the exponent is not constant over time, than while the growth is "exponential", it is also arbitrarily slow, as you indicate..

With exponentials, it doesn't really matter. Even an arbitrarily-slow growth rate will still exceed any polynomial function with time (and a surprisingly short amount of time at that).

MT's claim was that because of exponential growth, very quickly the planet's resources will be depleted... 

On Earth, use of resources is only growing meaningfully in developing regions...  Once a region develops, the exponents drops and use of resources trends towards constant (never mind fossil fuels, that's a whole different thing)  Germany and Japan are not using more and more steel in any meaningful way, not when compared say with China.

European steel is rather a special macroeconomic case, don't you think? https://www.bloomberg.com/news/articles/2019-05-29/europe-s-steel-sector-is-suffering-here-are-charts-showing-why

If 99 families in town have 1-2 kids, and the Robinson family and descendants have 9 kids each, what will happen to the population dynamics of the town? I mean, 99% of the families aren't growing, right? :)

The other problem is that Germany/Japan aren't independent economic entities. They rely on cheap labor from and raw materials dug up inside other countries.  If the high-energy German lifestyle can only achieve sufficient quality-of-life to depress birth/growth rates because it's being subsidized by cheaper labor/material from low-energy societies (with the low-energy situation causing both cheap labor/material prices and higher birth/growth rates), then neither system is truly steady-state or sustainable.

It isn't the case that there's a sustainable Germany, and then over here by its lonesome is an unsustainable China, meaning that one out of two of these societies are sustainable. If the "sustainable" Germany couldn't exist without the unsustainable China, then we've actually observed zero sustainable societies.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/07/2020 06:14 pm
[snip]

Yup and I'm saying that indeed Y is necessary for independence, but that Z ("Colony doesn't use planetary resources") is neither desired, practical, or will happen.

The main reason is that the colony has to grow from somewhere. As long as it is growing, it needs to either mine the planet, or import. Importing planetary-scale amounts of material is impractical, and so of course it will mine and use planetary resources.

And I agree.

The Big Hard problem is, after it's established, how do you sustain that society without continuous extraction of non-renewable planetary resources (aka a "once-through" society, which is by definition unsustainable)? So far we haven't even solved this problem on Earth yet.

Heck, we haven't even solved the (far simpler) task of just regulating our own growth rate.

You may be thinking about some future state where the colony occupies the entirety of Mars and is no longer capable of growing (like a hypothetical Earth, but with all developing regions have become developed)

Note that the developed regions of Earth are only possible because they continuously extract resources from the developing regions.

such a state is hundreds if not thousands of years away and so is happening at a very different technological state, complete with solar-system wide resource exploitation

edit: Whether this is possible has yet to be shown.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/07/2020 06:37 pm
[snip]

Yup and I'm saying that indeed Y is necessary for independence, but that Z ("Colony doesn't use planetary resources") is neither desired, practical, or will happen.

The main reason is that the colony has to grow from somewhere. As long as it is growing, it needs to either mine the planet, or import. Importing planetary-scale amounts of material is impractical, and so of course it will mine and use planetary resources.

And I agree.

The Big Hard problem is, after it's established, how do you sustain that society without continuous extraction of planetary resources (aka a "once-through" society, which is by definition unsustainable)? So far we haven't even solved this problem on Earth yet.

Heck, we haven't even solved the (far simpler) task of just regulating our own growth rate.

You may be thinking about some future state where the colony occupies the entirety of Mars and is no longer capable of growing (like a hypothetical Earth, but with all developing regions have become developed)

I should point out that such a hypothetical Earth is logistically impossible, because the developed regions of Earth are only possible because they're extracting resources from the developing regions.

such a state is hundreds if not thousands of years away and so is happening at a very different technological state, complete with solar-system wide resource exploitation, so doesn't fall under any practical current-day consideration.

I suppose that's one way to extrapolate into the future. Blind confidence in technology and invoking some Solar system-wide version of manifest destiny? That may be enough for the Believers, but otherwise it's not very persuasive.

If this is truly the best we can offer, let's all agree to dispense with the "backup of Earth" rhetoric.

We haven't solved it since it's not a problem we have to solve, and won't be for Mars either.

I'm going to bow out here since it's getting circular and focused on tangential semantic arguments...

I'm leaving with this:

Planets are inherently different from space stations in exactly that aspect - that there are resources to exploit.  Stating that a planet is just a big space station is a semantic exercise that misses the point.

Recycling will happen just because on Mars it'll usually be a better way to get resources, since they are already partially separated out, but that's the only reason to do it...  There is no reason, and it is also impossible while growing, to get to a point where you don't use planetary resources at all, for several reasons mentioned upthread.

That was the original debate.  I really hate following up on those other splinter arguments on whether economies are semantically "exponential" etc.

Peace.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 06/07/2020 06:41 pm
The catch is, how exactly does the colony go about deciding to stop growing, once the resources are depleted? :-\

It's a myth that economic growth requires greater use of resources. It's the easy way, of course, but not necessary. Greater efficiency in the use of resources also leads to economic growth.

There's no society, or even life itself, that is not utilising a depleting resource. Indeed, it's impossible to do so. Even the Sun's energy production does so and will fail eventually. But the timescale over which such depletion may occur is relevant. We have no idea what will happen this century, let alone longer timescales.
Title: Re: Power options for a Mars settlement
Post by: steveleach on 06/07/2020 06:56 pm
Are these economics discussions directly relevant to power options for a Mars settlement?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/07/2020 07:06 pm
Meet the new planet. Just as unsustainable as the old planet. :(

splinter arguments on whether economies are semantically "exponential" etc.

You bring this up as if it was unrelated, so I feel the need to clarify: it's an important point because it's related to the actual behavior of the mathematical function. An exponential will always exceed any polynomial function.

Cheers.


The catch is, how exactly does the colony go about deciding to stop growing, once the resources are depleted? :-\

It's a myth that economic growth requires greater use of resources.

This is an idea called "decoupling," Sadly, it seems to be decoupling that's the myth (created to preserve our growth-centric values).

https://theconversation.com/the-decoupling-delusion-rethinking-growth-and-sustainability-71996

https://eeb.org/decoupling-debunked1/
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/07/2020 07:13 pm
Are these economics discussions directly relevant to power options for a Mars settlement?

meekGee moved the discussion here, but I'm happy to continue in a different thread.

Title: Re: Power options for a Mars settlement
Post by: Genial Precis on 06/07/2020 07:14 pm
A few points for anyone considering a nuclear option.
AFAIK, if you want to make a really long-lived (100 yr) reactor without HEU, you're much better off with one of the liquid fuel molten salt concepts. The solid fuel elements are inherently short-lived, and large high-pressure vessels around the reactor are a nuisance that's only tolerated on Earth. At one end of the spectrum of doing things to the fuel salt, there's Elysium's fast reactor concept which really is just sealed, and then in the middle you have designs which call for collecting the volatile portion of the fission products with a bubbling process, preventing it from poisoning itself over a long cycle of operation.

Elysium and Thorcon seem to have the reactor concepts with highest TRL (Thorcon is imminently attempting to build a pilot plant in Indonesia) but there's lots of room to improve on the state of the art, which would be useful for cheap, clean energy production on Earth as well.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/07/2020 08:57 pm
Are these economics discussions directly relevant to power options for a Mars settlement?

meekGee moved the discussion here, but I'm happy to continue in a different thread.

I'd say let's move to another thread but this has progressed far beyond anything we started discussing I wouldn't know where to move to...  Apologies for polluting the thread.  It was originally about ISRU and Power for ISRU.
Title: Re: Power options for a Mars settlement
Post by: FinalFrontier on 06/07/2020 09:22 pm
Back on topic.
My two cents is: reactors. Small fission reactors possibly transitioning to terrestrial LFTR plants later on. Mars has a decent amount of thorium.

Some form of nuclear will probably be what ends up happening, combined with solar and battery storage obviously. Don't really see a better or more efficient way.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/08/2020 12:21 am
Back on topic.
My two cents is: reactors. Small fission reactors possibly transitioning to terrestrial LFTR plants later on. Mars has a decent amount of thorium.

Some form of nuclear will probably be what ends up happening, combined with solar and battery storage obviously. Don't really see a better or more efficient way.
We've touched on this a few times here, but thorium and uranium need to be in adequate concentrations to be usable.  If the processing gets too expensive, it no longer makes sense to extract thorium on Mars.  Supplying thorium or uranium from Earth would make sense, though.  Once refined, the energy density is very high. 
Adding orbital mirrors might be a cheap way to improve solar efficiency, http://www.niac.usra.edu/files/students/final_report/Woida_Rigel.pdf.  The reports is for terraforming, but it seems like a cheap way to increase the solar constant for solar array areas.
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 06/08/2020 01:12 am
Back on topic.
My two cents is: reactors. Small fission reactors possibly transitioning to terrestrial LFTR plants later on. Mars has a decent amount of thorium.

Some form of nuclear will probably be what ends up happening, combined with solar and battery storage obviously. Don't really see a better or more efficient way.
We've touched on this a few times here, but thorium and uranium need to be in adequate concentrations to be usable.  If the processing gets too expensive, it no longer makes sense to extract thorium on Mars.  Supplying thorium or uranium from Earth would make sense, though.  Once refined, the energy density is very high. 
Adding orbital mirrors might be a cheap way to improve solar efficiency, http://www.niac.usra.edu/files/students/final_report/Woida_Rigel.pdf.  The reports is for terraforming, but it seems like a cheap way to increase the solar constant for solar array areas.
Of course, if you're shipping nuclear fuel to Mars, you'll want the fuel density to be as high as possible, which for uranium would essentially mean weapons grade.  The regulatory burden of getting your hands on several tons on 90%+ U235 may be insurmountable.  This is where thorium reactors could really shine,  a couple tons of 20%ish U235 for startup, and then you can ship all the high-grade Th232 you want with no worry about weapons proliferation risk or the associated regulatory hurdles.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/08/2020 04:12 am
There are two numbers that matter...  The power/mass density of the components you ship from earth, and the energy cost of the components you want to make on Mars.

The preference will always be to build the power generation equipment locally to A) save on transport costs and B) enable up-scaling, but if the energy cost of the equipment is worth more than a year's production from same equipment, it starts getting iffy, since you have to pay the energy cost up-front.

That's why I'm advocating for a two-part PV system.

Ship semiconductor film (10-25um thick) from Earth initially, since the power/mass density can beat anything else including nuclear (counting the entire nuclear plant, not just the fuel)  > 1kWatt/kg is achievable.  This part is energy-intensive, and requires a lot of industrial infrastructure.

The film needs to be laminated onto a plastic substrate for deployment.  The plastic weighs 100x as much, and the fabrication equipment (From CH4/O2 to various plastics) is simpler. Energy wise, everything down from the base molecules should be almost free, so at first approximation counting the Carbons will give an idea whether this works.

if it doesn't, and we need to ship entire outdoor-ready panels from earth, it's going to be a lot more difficult

The equivalent idea in nuclear is to build the nuclear plant locally, but ship the fuel from Earth.  That requires a lot more local fabrication capability than manufacturing plastic sheets.

By instinct I'm much more of a fan of nuclear power, but for locally-produced or almost-locally-produced power, solar wins, at least initially.

--

BTW - orbital mirrors don't work, optically.  The natural divergence of sunlight (due to the size of the sun) means that there's a pretty wide divergence angle (about 5 mRad full angle on Mars) no matter how much you try to focus the light...    You have to be at local synchronous orbit, 17,000 km away, so the spot size you're creating is at least some 85 km across...
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 06/08/2020 06:03 am
AFAIK, if you want to make a really long-lived (100 yr) reactor without HEU, you're much better off with one of the liquid fuel molten salt concepts. The solid fuel elements are inherently short-lived, and large high-pressure vessels around the reactor are a nuisance that's only tolerated on Earth.
One of the baselines for Gen IV reactors is a 60 year life span. The old standard was about 25 and  IIRC life extension programmes  have bought this to at least the 40 year mark in some cases.

This PoV has so many hidden assumptions in it it's difficult to know where to begin. You might like to start by considering the TRL level (https://www.nasa.gov/sites/default/files/trl.png)  of MSR technology. MSR are about TR 4 but the large scale demonstration was more that 50 years ago. Digging in the ORNL and ANL archives indicates the Hastalloy-N alloy had issues that only showed up in long term tests. It was not the panacea they hoped for.  :( .
BTW that diagram is very misleading. The costs involved in transitioning a technology up the TRL scale are highly non linear.  IMHO worst of all is that AFAIK the advocates have shown no work on heat exchanger technology needed to collect the heat and have hand waved away the corrosiveness of molten salts with basically "If you control the pH everything is fine."  No HX, no effective heat source.

Any system that depends on enriched fuel will always be problematical because you either have to buy the enriched fuel from earth (so you need a source of revenue) or you make it on mars. Enrichment technology is the key proliferation issue wrt to countries acquiring nuclear weapons mfg capability.  Look at the US and Israels response to Iran acquiring it.

What if Mars decided to nuke Earth? What if the martian economy got so bad they decided to raise a bit of cash and sell a bomb to someone?  I know such ideas are paranoid fantasies which sensible people should consider ridiculous and absurd, but then I'm not the one who wants to acquire such technology.  :(

For a growing martian economy if you're going to incorporate nuclear you need to accept re-processing of fuel.  This doesn't need a breeder reactor to burn minor actinides (all reactors breed) but it will need hot cells to handle them.  Doing so radicallyreduces the volume of actual long lived waste, mostly to Sr and Cs.

You're right about pressure vessels but wrong that there are no actual designs that have been built that don't need them and for which actual operations experience exists. They just don't exist in America.
Quote from: Genial Precis
At one end of the spectrum of doing things to the fuel salt, there's Elysium's fast reactor concept which really is just sealed, and then in the middle you have designs which call for collecting the volatile portion of the fission products with a bubbling process, preventing it from poisoning itself over a long cycle of operation.

Elysium and Thorcon seem to have the reactor concepts with highest TRL (Thorcon is imminently attempting to build a pilot plant in Indonesia) but there's lots of room to improve on the state of the art, which would be useful for cheap, clean energy production on Earth as well.
There is indeed

But mars is probably the last place to run an R&D programme to develop those improvements. The complete  lack of a supply chain (for anything) being quite a serious handicap. :(
Title: Re: Power options for a Mars settlement
Post by: Rei on 06/08/2020 09:20 am
BTW - orbital mirrors don't work, optically.  The natural divergence of sunlight (due to the size of the sun) means that there's a pretty wide divergence angle (about 5 mRad full angle on Mars) no matter how much you try to focus the light...    You have to be at local synchronous orbit, 17,000 km away, so the spot size you're creating is at least some 85 km across...

I agree with most of your post, but I want to correct this part - there also exist designs for LEO orbital mirror constellations, and everything else in-between. This would apply even better to Mars, since one can orbit at a little over half the altitude, for a given amount of drag.  An orbital mirror is a very high-drag structure, so you'd probably want it around 300km altitude (equivalent to nearly 600km on Earth), yielding a perfectly manageable spot size only about 1 1/2km across on the short axis (though elongated along the orbital axis by varying degrees).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/08/2020 01:53 pm
BTW - orbital mirrors don't work, optically.  The natural divergence of sunlight (due to the size of the sun) means that there's a pretty wide divergence angle (about 5 mRad full angle on Mars) no matter how much you try to focus the light...    You have to be at local synchronous orbit, 17,000 km away, so the spot size you're creating is at least some 85 km across...

I agree with most of your post, but I want to correct this part - there also exist designs for LEO orbital mirror constellations, and everything else in-between. This would apply even better to Mars, since one can orbit at a little over half the altitude, for a given amount of drag.  An orbital mirror is a very high-drag structure, so you'd probably want it around 300km altitude (equivalent to nearly 600km on Earth), yielding a perfectly manageable spot size only about 1 1/2km across on the short axis (though elongated along the orbital axis by varying degrees).
It be nice, but I don't think it'll work..

At 300 km your mirror is only in view of the PV field for a few minutes and has to slew awfully fast.. 

So you need a mega-constellation of fast-slewing km-sized mirrors that has a utilization factor of a tiny fraction (unless you also have a planet wide constellation of PV fields)

.. and this is assuming we can build perfect amd rigid km sized mirrors...

Since PV is so cheap, and since I'm proposing making the bulk of the mass on the planet, I can't see such a system being remotely competitive.

I know all forms of SSP are more competitive  on Mars than they are on Earth, but they're still impractical.  Maybe when it comes to Asteroid mining they'll get their (wait for it) day in the sun.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/08/2020 03:18 pm
BTW - orbital mirrors don't work, optically.  The natural divergence of sunlight (due to the size of the sun) means that there's a pretty wide divergence angle (about 5 mRad full angle on Mars) no matter how much you try to focus the light...    You have to be at local synchronous orbit, 17,000 km away, so the spot size you're creating is at least some 85 km across...

I agree with most of your post, but I want to correct this part - there also exist designs for LEO orbital mirror constellations, and everything else in-between. This would apply even better to Mars, since one can orbit at a little over half the altitude, for a given amount of drag.  An orbital mirror is a very high-drag structure, so you'd probably want it around 300km altitude (equivalent to nearly 600km on Earth), yielding a perfectly manageable spot size only about 1 1/2km across on the short axis (though elongated along the orbital axis by varying degrees).
It be nice, but I don't think it'll work..

At 300 km your mirror is only in view of the PV field for a few minutes and has to slew awfully fast.. 

So you need a mega-constellation of fast-slewing km-sized mirrors that has a utilization factor of a tiny fraction (unless you also have a planet wide constellation of PV fields)

.. and this is assuming we can build perfect amd rigid km sized mirrors...

Since PV is so cheap, and since I'm proposing making the bulk of the mass on the planet, I can't see such a system being remotely competitive.

I know all forms of SSP are more competitive  on Mars than they are on Earth, but they're still impractical.  Maybe when it comes to Asteroid mining they'll get their (wait for it) day in the sun.
Have you read the paper? It’s indeed a huge array of smaller mirrors.  The mirror to ground ratio is a bit more than  6 to 1 to increase the illumination to 1000 w/m2.  Inflatable Mylar ballons.  I do worry about drag, but the paper is by a student in the optics department at a US university so that part should be good.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 06/08/2020 07:36 pm
So, basically a Znamya program that actually works.

https://en.m.wikipedia.org/wiki/Znamya_(satellite)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/09/2020 12:42 am
So, basically a Znamya program that actually works.

https://en.m.wikipedia.org/wiki/Znamya_(satellite)
Seems the first one worked, at least.  Hope the tests go better for this, whenever that happens!
Title: Re: Power options for a Mars settlement
Post by: RobLynn on 06/09/2020 01:14 am
Pretty big development in thermophotovotaics in last year means that you can now get to about 30% efficiency at 1200°Chttps://www.pnas.org/content/116/31/15356 (https://www.pnas.org/content/116/31/15356), and that is expected to rise to 50% in future.  That pretty much matches the efficiencies of heat engines but with something that doesn't require a working fluid, only a coolant for the thermophotovoltaics (eg readily available CO2) and large radiator surfaces, and maybe some refractory radiation shielding for the thermophotovoltaics.   Thermophotovoltaics will be super light and low maintenance compared to finicky heat engines.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 06/09/2020 04:52 am
BTW - orbital mirrors don't work, optically.  The natural divergence of sunlight (due to the size of the sun) means that there's a pretty wide divergence angle (about 5 mRad full angle on Mars) no matter how much you try to focus the light...    You have to be at local synchronous orbit, 17,000 km away, so the spot size you're creating is at least some 85 km across...

I agree with most of your post, but I want to correct this part - there also exist designs for LEO orbital mirror constellations, and everything else in-between. This would apply even better to Mars, since one can orbit at a little over half the altitude, for a given amount of drag.  An orbital mirror is a very high-drag structure, so you'd probably want it around 300km altitude (equivalent to nearly 600km on Earth), yielding a perfectly manageable spot size only about 1 1/2km across on the short axis (though elongated along the orbital axis by varying degrees).
It be nice, but I don't think it'll work..

At 300 km your mirror is only in view of the PV field for a few minutes and has to slew awfully fast.. 

So you need a mega-constellation of fast-slewing km-sized mirrors that has a utilization factor of a tiny fraction (unless you also have a planet wide constellation of PV fields)

.. and this is assuming we can build perfect amd rigid km sized mirrors...

Since PV is so cheap, and since I'm proposing making the bulk of the mass on the planet, I can't see such a system being remotely competitive.

I know all forms of SSP are more competitive  on Mars than they are on Earth, but they're still impractical.  Maybe when it comes to Asteroid mining they'll get their (wait for it) day in the sun.
Have you read the paper? It’s indeed a huge array of smaller mirrors.  The mirror to ground ratio is a bit more than  6 to 1 to increase the illumination to 1000 w/m2.  Inflatable Mylar ballons.  I do worry about drag, but the paper is by a student in the optics department at a US university so that part should be good.
I've spent several years doing CPV including an ultra lightweight inflatable one..  Also spent a bit of time thinking about various forms of SBSP.

My conclusion was that there are so many practical problems inherent to the designs that they are non-starters in Earth, better but still not even close on Mars, but maybe can make sense in the asteroid belt.

Which is along way of admitting that I haven't read that paper.... :)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/09/2020 03:38 pm
BTW - orbital mirrors don't work, optically.  The natural divergence of sunlight (due to the size of the sun) means that there's a pretty wide divergence angle (about 5 mRad full angle on Mars) no matter how much you try to focus the light...    You have to be at local synchronous orbit, 17,000 km away, so the spot size you're creating is at least some 85 km across...

I agree with most of your post, but I want to correct this part - there also exist designs for LEO orbital mirror constellations, and everything else in-between. This would apply even better to Mars, since one can orbit at a little over half the altitude, for a given amount of drag.  An orbital mirror is a very high-drag structure, so you'd probably want it around 300km altitude (equivalent to nearly 600km on Earth), yielding a perfectly manageable spot size only about 1 1/2km across on the short axis (though elongated along the orbital axis by varying degrees).
It be nice, but I don't think it'll work..

At 300 km your mirror is only in view of the PV field for a few minutes and has to slew awfully fast.. 

So you need a mega-constellation of fast-slewing km-sized mirrors that has a utilization factor of a tiny fraction (unless you also have a planet wide constellation of PV fields)

.. and this is assuming we can build perfect amd rigid km sized mirrors...

Since PV is so cheap, and since I'm proposing making the bulk of the mass on the planet, I can't see such a system being remotely competitive.

I know all forms of SSP are more competitive  on Mars than they are on Earth, but they're still impractical.  Maybe when it comes to Asteroid mining they'll get their (wait for it) day in the sun.
Have you read the paper? It’s indeed a huge array of smaller mirrors.  The mirror to ground ratio is a bit more than  6 to 1 to increase the illumination to 1000 w/m2.  Inflatable Mylar ballons.  I do worry about drag, but the paper is by a student in the optics department at a US university so that part should be good.
I've spent several years doing CPV including an ultra lightweight inflatable one..  Also spent a bit of time thinking about various forms of SBSP.

My conclusion was that there are so many practical problems inherent to the designs that they are non-starters in Earth, better but still not even close on Mars, but maybe can make sense in the asteroid belt.

Which is along way of admitting that I haven't read that paper.... :)
Well it perfectly ok to be skeptical about 150m diameter disk shaped balloons self inflating in Mars orbit at low overall cost.  As long as it’s theoretically possible I’m ok with the idea at this point 😀
Title: Re: Power options for a Mars settlement
Post by: gin455res on 06/10/2020 03:31 pm
Pretty big development in thermophotovotaics in last year means that you can now get to about 30% efficiency at 1200°Chttps://www.pnas.org/content/116/31/15356 (https://www.pnas.org/content/116/31/15356), and that is expected to rise to 50% in future.  That pretty much matches the efficiencies of heat engines but with something that doesn't require a working fluid, only a coolant for the thermophotovoltaics (eg readily available CO2) and large radiator surfaces, and maybe some refractory radiation shielding for the thermophotovoltaics.   Thermophotovoltaics will be super light and low maintenance compared to finicky heat engines.

This might make for a nice tech to create a mini dyson-sphere around a brown dwarf.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 06/11/2020 11:58 am
...
Well it perfectly ok to be skeptical about 150m diameter disk shaped balloons self inflating in Mars orbit at low overall cost.  As long as it’s theoretically possible I’m ok with the idea at this point 😀

Or just use balloons in the actual Mars atmosphere.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 06/11/2020 01:57 pm
...
Well it perfectly ok to be skeptical about 150m diameter disk shaped balloons self inflating in Mars orbit at low overall cost.  As long as it’s theoretically possible I’m ok with the idea at this point 😀

Or just use balloons in the actual Mars atmosphere.
Won't they need to be tougher and heavier?  And require light (expensive) gases that leak, while in space any old gas will do?  And in orbit they can be spread out in sequence while in the atmosphere they would be rather crowded.  Ground based reflectors have many problems well described in this thread.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 06/11/2020 03:55 pm
...
Well it perfectly ok to be skeptical about 150m diameter disk shaped balloons self inflating in Mars orbit at low overall cost.  As long as it’s theoretically possible I’m ok with the idea at this point 😀

Or just use balloons in the actual Mars atmosphere.
Won't they need to be tougher and heavier?  And require light (expensive) gases that leak, while in space any old gas will do?  And in orbit they can be spread out in sequence while in the atmosphere they would be rather crowded.  Ground based reflectors have many problems well described in this thread.

I guess so, but nitrogen is a lifting gas on Mars. So is oxgen. It doesn't preclude you from also making orbital ones...
Title: Re: Power options for a Mars settlement
Post by: LMT on 06/17/2020 02:14 am
Experimental Results Consistent With Martian Atmospheric Triboelectricity

Mars-chamber experiment of Wang et al. 2020 gives results consistent with predictions of martian atmospheric electrification.

Results support the analysis of Baumgaertner 2016, giving further reason to think martian atmospheric triboelectricity can be harvested readily at MW scale during the worst martian storms.

Image:  Wang et al. 2020, Table S2.  Experimental results were obtained under electron flux in predicted martian atmospheric range.

Refs.

Baumgaertner, A. (2016). Power to Mars. (http://www.academia.edu/download/57265698/Power-to-Mars.v08_updateJuly2018.pdf)

Wang, A., Yan, Y., Jolliff, B.L., McLennan, S.M., Wang, K., Shi, E. and Farrell, W.M., Chlorine Release from Common Chlorides by Martian Dust Activity. (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006283) Journal of Geophysical Research: Planets, p.e2019JE006283.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/17/2020 02:25 am
Experimental Results Consistent With Martian Atmospheric Triboelectricity

Mars-chamber experiment of Wang et al. 2020 gives results consistent with predictions of martian atmospheric electrification.

Results support the analysis of Baumgaertner 2016, giving further reason to think martian atmospheric triboelectricity can be harvested readily at MW scale during the worst martian storms.

Image:  Wang et al. 2020, Table S2.  Experimental results were obtained under electron flux in predicted martian atmospheric range.

Refs.

Baumgaertner, A. (2016). Power to Mars. (http://www.academia.edu/download/57265698/Power-to-Mars.v08_updateJuly2018.pdf)

Wang, A., Yan, Y., Jolliff, B.L., McLennan, S.M., Wang, K., Shi, E. and Farrell, W.M., Chlorine Release from Common Chlorides by Martian Dust Activity. (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006283) Journal of Geophysical Research: Planets, p.e2019JE006283.

Can anyone besides LMT clear up whether "consistent with triboelectricity" in the paper post title means "results are positive evidence of Mars triboelectricity," or "results are not inconsistent with Mars having triboelectricity?"
Title: Re: Power options for a Mars settlement
Post by: Pete on 06/17/2020 12:47 pm
Can anyone besides LMT clear up whether "consistent with triboelectricity" in the paper title means "results are positive evidence of Mars triboelectricity," or "results are not inconsistent with Mars having triboelectricity?"

Any such statement in a scientific paper means the latter form.
i.e. when seeing a statement of "measured data is consistent with X ",
it means that X is not disqualified as a factor, the measured data falls within predicted value ranges assuming X, and indeed X might be the current favorite fit for the situation. But there is *absolutely zero* proof that X is the fit. Merely a significant body of data that never eliminates the possibility of X.
Title: Re: Power options for a Mars settlement
Post by: LMT on 06/19/2020 02:25 am
Can anyone besides LMT clear up whether "consistent with triboelectricity" in the paper title means "results are positive evidence of Mars triboelectricity," or "results are not inconsistent with Mars having triboelectricity?"

Any such statement in a scientific paper means the latter form.
i.e. when seeing a statement of "measured data is consistent with X ",
it means that X is not disqualified as a factor, the measured data falls within predicted value ranges assuming X, and indeed X might be the current favorite fit for the situation. But there is *absolutely zero* proof that X is the fit. Merely a significant body of data that never eliminates the possibility of X.

The paper (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006283) doesn't use those words; you both just assumed.

Posters might comment on the paper itself.

Storm power is a challenging topic; options are limited.  There's value in exploration of potential improvements to the initial storm-power proposals of Baumgaertner 2016 (https://www.academia.edu/download/57265698/Power-to-Mars.v08_updateJuly2018.pdf).

Quote from: Wang et al. 2020
Plain Language Summary

Chlorine has a broad distribution on the surface of Mars. Compared to Martian meteorites, high concentrations of Cl was found in all Martian surface materials analyzed during landed missions on Mars. A “Cl cycle” has been driven by volcanic activity and aqueous chemistry throughout Martian history. A Cl cycle still exists on present‐day Mars, and in this work, we seek to determine a mechanism that may drive the exchange of chlorine between the surface and the atmosphere. We present two sets of experimentally observed evidences for the instantaneous chlorine release from common chlorides during the process of electrostatic discharge (ESD), that suggest the electrochemistry induced by Martian dust activity may be an important process to drive the Cl cycle between the surface and atmosphere on present‐day Mars. The highly reactive species, such as the Cl at excited state, oxychlorates, and gaseous free radicals, generated by ESD process on Mars are of great importance. The influences of electrochemistry induced by Martian dust events on the habitability and on the search for the trace of life at the surface and in shallow subsurface will need further investigation.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/19/2020 09:34 pm
Can anyone besides LMT clear up whether "consistent with triboelectricity" in the paper title means "results are positive evidence of Mars triboelectricity," or "results are not inconsistent with Mars having triboelectricity?"

Any such statement in a scientific paper means the latter form.
i.e. when seeing a statement of "measured data is consistent with X ",
it means that X is not disqualified as a factor, the measured data falls within predicted value ranges assuming X, and indeed X might be the current favorite fit for the situation. But there is *absolutely zero* proof that X is the fit. Merely a significant body of data that never eliminates the possibility of X.

The paper (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006283) doesn't use those words; you both just assumed.

I didn't assume anything. I asked a question.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 06/20/2020 03:59 pm
[snip]

You did, but the phrase "consistent with triboelectricity" was not in either paper's title. I think this is where the confusion arose.

Ahh, thanks for pointing that out. Edited.
Title: Re: Power options for a Mars settlement
Post by: LMT on 06/21/2020 03:28 am
Ahh, thanks for pointing that out. Edited.

np.  MW harvest of atmospheric current in storms becomes even more attractive when the entire harvesting system is integral to a solar panel farm.  In a conceptual PV farm canopy deployment (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304), the pylons, tension wires and DC grid devices can all be repurposed for atmospheric harvest.  A step-down DC/DC converter would be needed to match grid storm output to facility voltage, but that's a small farm addition.

Also, Baumgaertner 2016 (https://www.academia.edu/download/57265698/Power-to-Mars.v08_updateJuly2018.pdf) noted that 10 m altitude maximizes voltage and power harvest in storms (Fig. 1, below).  Coincidentally, 10 m happens to be a good altitude for PV farm deployment.
Title: Re: Power options for a Mars settlement
Post by: Pete on 06/25/2020 11:19 pm
Can anyone besides LMT clear up whether "consistent with triboelectricity" in the paper title means "results are positive evidence of Mars triboelectricity," or "results are not inconsistent with Mars having triboelectricity?"

Any such statement in a scientific paper means the latter form.
i.e. when seeing a statement of "measured data is consistent with X ",
it means that X is not disqualified as a factor, the measured data falls within predicted value ranges assuming X, and indeed X might be the current favorite fit for the situation. But there is *absolutely zero* proof that X is the fit. Merely a significant body of data that never eliminates the possibility of X.

The paper (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006283) doesn't use those words; you both just assumed.

I didn't assume anything, I answered the posters question AS ASKED.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/11/2020 08:34 pm
Reposting an excellent reply I received from Vanspace via PM (the original thread was off-topic), with permission. I can barely read that tiny quoted text, so I broke our back-and-forth into three separate posts. Here's what Vanspace wrote:



I think you deserve an answer to your question of why I it think its harder but when I got it written out I realized that only you would care and it would almost certainly derail the thread. The main take away is that an inflated tube of plastic film is really bad at transmitting force lengthwise. Usually thin film bags of air are used to absorb force like in your Amazon package.

The multiple tube idea has merit but attempting to control the roll around say a rock, by using variable pressure from the far end of the stretchy tube to differentially leverage the coil movement for steering seems hard. I am not saying it isn't possible but I suspect landing a booster may be an easier control system to create.

Strongly disagree. It's not much harder than "if it goes right, steer left. If it goes left, steer right." Much simpler than the G-FOLD landing algorithm.

I disagree about "huge" drawbacks, but I do agree that the party favor deployment is unnecessary once you have human teleoperators who can reliably unroll it with a robotic roll handler.

That last line really hits the nail. Your system requires teleoperation of a complex novel feedback control system yet to be developed.

You misunderstand me. I'm talking about teleoperating robotic handling vehicles, not simple inflation-deployed rolls.

And again, the entire point of the inflation deployment mechanism is to avoid exactly that type of complexity.


And how could you possibly think that this is an easier control problem than steering an unrolling coil?  ???

The simplicity of just blowing up tubes differentially dies in the details. The design is to use real time differences in pressure between the tubes to apply differing forces on each side. Simple, uses the gas laws of pressure volume and temperature to control it.  The devil comes in realizing that it is nearly impossible to model pressure volume and temperature within the rapidly changing system accurately enough to give any fine control. All of the pressure changes you apply to the tube will mostly just deform the tube not impart control on the coil.

The system mechanically is just driving two wedges between the ground and the coil to move the coil forward with control coming from the force applied to each wedge. That the wedges are actually air pressure in an unrolling tube and not metal doesn't change the mechanical analysis. Thus mechanically, control of the system is directly tied to control over the differential force exerted on the wedges. If that force was being applied by metal rods the control system would be very simple. However, the force is being applied using a thin walled tube of flexible plastic of changing length using air pressure to both maintain rigidity of the tube and apply force to the wedges. It resembles trying to roll an oil barrel using pool noodles for applying force.

Assumptions: Lets say a 100kg coil that is 100 meters long. Assume some sort of polyethylene film backing with PV on the upper side. There are two tubes on the underside, one situated near each edge. Assume real-time position and multi-axis motion data of the unrolling coil, from sensors in the coil.  We can ignore the control hardware and just assume unlimited ability to change pressure in each tube any amount in zero time. The pressure change control system is located on the starting edge of the coil. 

Starting off with the coil just positioned and no motion. Pressure is added evenly to the tubes to get the coil moving.
So now the coil is moving away. To maintain any control of the coil at all, the system must inflate the increasing tube volume at exactly the same rate it is coming off the coil in order to maintain a steady pressure in the increasing volume. Too slow and the tube away from the wedge is being inflated, imparting no control force on the wedge. If the wedge was a real piece of metal it would be like the wedge not actually touching the coil so it can't impart force. Adding gas faster than the actual rate of increasing volume can only be done by expanding the wedge and thus imparting control force increasing the velocity of the coil. To maintain the ability to control the system the gas added must exactly match the increasing volume. Actually controlling the system can only be done by exceeding that rate. Simply multiplying the velocity of unrolling by the cross section of the tube is not accurate enough to calculate volume changes. The tube is a flexible film so it stretches meaning the actual volume of the tube outside the wedge is not a constant. This variability in volume in the tube due to stretching will be larger than the volume of the wedge fairly early in the roll out. Additionally, any bends in the path the coil follows necessarily bends the tubes and thus also changes the volume. A smaller volume issue is thermal changes to the system. At 0.02bar and -40C, small temperature changes can also have outsized effects on volume. How to measure all of these changes over a rapidly changing geometry fast enough to prevent them from overwhelming control signals does not seem a trivial task.

The rate of gas added to the system is the sum of the increased nominal volume from unrolled tube, the smaller variable amount for changes in nominal volume due to stretching/bending, some for temperature changes and finally the smallest amount being the control signal pressure for that tube that is supposed to steer the whole thing. Once the variable volume changes exceed the volume of the wedge, the relationship of gas being added compared to the amount of force applied at the wedge becomes non-linear, the signal getting lost in the noise.

All of the above is the just the problems maintaining correct pressure to have any control authority in a single tube. The design calls to consistently exploit small differences between two tubes.

For all of the above reasons I doubt fine control can ever be achieved. I think with a lot of testing a good model of all the volume fluctuations could be produced that might achieve it but there are so many variables it is not a sure thing.

I do see potential for better aim by using pulsed waves of pressure. Essentially a high pressure is maintained throughout the roll out, accepting that it will continuously increase velocity. That part is just the standard uncontrolled party favor blowout deployment. The change is that synchronized waves of pressure are blasted down both tubes over and above the blowout pressure. The concept is that the tube that is longer and thus further ahead also has more volume and thus the force transmitted by the pulse is slightly smaller than in the other tube. The differences would tend to passively center the roll rather than actively steer. However, since this only works when there is already continuous pressure being applied in the wedge i suspect the effect will be drowned out by other forces present. Like driving the oil barrel by hammering on the ends of two pool noodles I am not sure the effect would be significant.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/11/2020 08:35 pm
My reply to Vanspace:



It sounds like you're envisioning the tube building up some speed during deployment, but I was imagining inflating it very slowly and deliberately. This solves a lot of the wonky control problems. You'd have closed-loop control of the tube's internal pressure, so temperature and stretching are automatically accounted for.

I do disagree with the "roll an oil barrel with a pool noodle" analogy, because that suggests the tube is trying to push the coil "forward," but really the tube would only be pushing "up." The picture isn't someone behind the wedge pushing it forward, but instead the wedge itself expanding underneath (like inflating a rolled-up air mattress).
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/11/2020 08:37 pm
Vanspace's reply:



I think your method for controlling roll out is just with in the edge of physically possible and will be happy to discuss it. However, I will stand by the pool noodle analogy. Yes, movement is from the wedge is expanding but only if expanding under the roll is easier than expanding anywhere else along the entire length of the tube. Which is only true if the tube itself can't expand or bend anywhere else. Its thin film so there is not a lot of pressure it can take without rupture and I don't know of any film polymer that does not have elastic expansion in at least one direction particularly when under tension such as air pressure. So when the coil is half unrolled, to get any movement, the easiest path for the gas to expand must be in the wedge. Its just really hard to see a 50 meter tube having no elastic expansion anywhere else unless the pressure is already at the breaking point for the material. The other way to fail is for the tube to bend, which turns the force applied into sideways motion of the tube rather then force on the wedge. Preventing this is really hard to achieve as it gets longer. At 50 meters, even using a steel rod to push a wedge has issues with the rod bending, a pillow of air is that much worse.

Air filled tubes of thin film are usually called pillows. They are famous for NOT accurately transmitting force to the other side. To use two to precisely transmit differential force to a heavy object on the other side sounds like the crazy near impossible challenges really good engineering profs come up with. Perfect for this site. If you want to carry the wild eyed idealist side I am happy to provide the cynical doubter part of the discussion :)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/11/2020 08:54 pm
Ok, everyone's caught up. 8) Back to your regularly scheduled posts...

I think your method for controlling roll out is just with in the edge of physically possible and will be happy to discuss it. However, I will stand by the pool noodle analogy. Yes, movement is from the wedge is expanding but only if expanding under the roll is easier than expanding anywhere else along the entire length of the tube. Which is only true if the tube itself can't expand or bend anywhere else. Its thin film so there is not a lot of pressure it can take without rupture and I don't know of any film polymer that does not have elastic expansion in at least one direction particularly when under tension such as air pressure. So when the coil is half unrolled, to get any movement, the easiest path for the gas to expand must be in the wedge. Its just really hard to see a 50 meter tube having no elastic expansion anywhere else unless the pressure is already at the breaking point for the material.

There's some internal pressure needed to "lift" the wedge. As long as the thin film tube can hold that pressure, it doesn't really matter how long it is. Elastic expansion is ok, it just means the pump moves slightly more gas volume to achieve the same internal pressure.

The other way to fail is for the tube to bend, which turns the force applied into sideways motion of the tube rather then force on the wedge. Preventing this is really hard to achieve as it gets longer. At 50 meters, even using a steel rod to push a wedge has issues with the rod bending, a pillow of air is that much worse.

Again, the mode of operation is not to "drive" the wedge sideways, using the tube as a compressive load-bearing member. It's to "lift" the coil, rolling it along the ground like an unrolling air mattress, using the tube mostly as a pneumatic line, except the working end, which is acting like a pneumatic piston between the ground beneath and the coil above (or more accurately, beneath-and-slightly-behind and above-and-slightly-ahead-of).

Air filled tubes of thin film are usually called pillows. They are famous for NOT accurately transmitting force to the other side. To use two to precisely transmit differential force to a heavy object on the other side sounds like [a] crazy near impossible [challenge].

See above.

Perfect for this site. If you want to carry the wild eyed idealist side I am happy to provide the cynical doubter part of the discussion :)

Indeed. Both are fun positions to play.  :)
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 07/11/2020 11:24 pm
Ok, everyone's caught up. 8) Back to your regularly scheduled posts...

I think your method for controlling roll out is just with in the edge of physically possible and will be happy to discuss it. However, I will stand by the pool noodle analogy. Yes, movement is from the wedge is expanding but only if expanding under the roll is easier than expanding anywhere else along the entire length of the tube. Which is only true if the tube itself can't expand or bend anywhere else. Its thin film so there is not a lot of pressure it can take without rupture and I don't know of any film polymer that does not have elastic expansion in at least one direction particularly when under tension such as air pressure. So when the coil is half unrolled, to get any movement, the easiest path for the gas to expand must be in the wedge. Its just really hard to see a 50 meter tube having no elastic expansion anywhere else unless the pressure is already at the breaking point for the material.

There's some internal pressure needed to "lift" the wedge. As long as the thin film tube can hold that pressure, it doesn't really matter how long it is. Elastic expansion is ok, it just means the pump moves slightly more gas volume to achieve the same internal pressure.

The other way to fail is for the tube to bend, which turns the force applied into sideways motion of the tube rather then force on the wedge. Preventing this is really hard to achieve as it gets longer. At 50 meters, even using a steel rod to push a wedge has issues with the rod bending, a pillow of air is that much worse.

Again, the mode of operation is not to "drive" the wedge sideways, using the tube as a compressive load-bearing member. It's to "lift" the coil, rolling it along the ground like an unrolling air mattress, using the tube mostly as a pneumatic line, except the working end, which is acting like a pneumatic piston between the ground beneath and the coil above (or more accurately, beneath-and-slightly-behind and above-and-slightly-ahead-of).


Here is were the breakdown happens: If the tube delivers all of the pressure to the wedge then the pneumatic piston will move the coil. You are assuming that all the pressure in the tube can only be relieved by expanding the wedge, my position is that except in very narrow conditions the tube will dissipate that pressure by expansion along its length far more readily than in the wedge. A pneumatic tube has thick walls that prevent the tube from stretching so that all of the pressure is applied at the other end. Because of that wall strength, the volume of a pneumatic tube never changes. You are assuming the tube functions mostly as a pneumatic line, mine is that mostly it can't because of its structural properties.

This tube is thin film polymer, once elasticity is all taken up there is a long phase where increasing pressure physically deforms the material causing it to stretch even more. Generally speaking, once the tube is filled, any increase in pressure is taken up by either elastic or permanent stretching of the film. There is no point where the physical geometry can stay constant with changing pressure. Adding "slightly more gas" is just going to stretch the tube walls. By adding wall thickness you can reduce this but that adds mass quickly and pretty soon your deployment mechanism is far out massing the PV it is supposed to deploy.

The second problem is bending. A pneumatic tube can bend without much problem because the thick walls prevent the bends from significantly changing the volume of the pipe. The tube we have here is thin polymer. Any bend will concentrate forces causing localized deformation of the walls as pressure goes up. Volume can't remain constant once bending occurs.

The reason why I say this looks to be just at the edge of whats possible is that there may be some combination of low pressure and tube wall thickness/rigidity that will just barely be enough to move a heavy coil without deforming the tube. Essentially a combo that allows the tube to act as a pneumatic tube but still weak enough to be crushed flat while rolled up all without being more than a small percentage of the PV mass being deployed. If that combo can be found then it can treated as a pneumatic tube and the only remaining problems lay in how to compare two tubes in real-time with sufficient precision to accurately apply different forces on each tube. That is merely a hard problem.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/12/2020 12:06 am
I suppose this is my fault, and I shouldn't have mentioned pneumatic tubing (I was just trying to be clear!). Because somehow you've gotten the idea that if it functions as pneumatic tubing, it must meet the all the same engineering requirements as real honest-to-goodness pneumatic tubing.

Ok, everyone's caught up. 8) Back to your regularly scheduled posts...

I think your method for controlling roll out is just with in the edge of physically possible and will be happy to discuss it. However, I will stand by the pool noodle analogy. Yes, movement is from the wedge is expanding but only if expanding under the roll is easier than expanding anywhere else along the entire length of the tube. Which is only true if the tube itself can't expand or bend anywhere else. Its thin film so there is not a lot of pressure it can take without rupture and I don't know of any film polymer that does not have elastic expansion in at least one direction particularly when under tension such as air pressure. So when the coil is half unrolled, to get any movement, the easiest path for the gas to expand must be in the wedge. Its just really hard to see a 50 meter tube having no elastic expansion anywhere else unless the pressure is already at the breaking point for the material.

There's some internal pressure needed to "lift" the wedge. As long as the thin film tube can hold that pressure, it doesn't really matter how long it is. Elastic expansion is ok, it just means the pump moves slightly more gas volume to achieve the same internal pressure.

The other way to fail is for the tube to bend, which turns the force applied into sideways motion of the tube rather then force on the wedge. Preventing this is really hard to achieve as it gets longer. At 50 meters, even using a steel rod to push a wedge has issues with the rod bending, a pillow of air is that much worse.

Again, the mode of operation is not to "drive" the wedge sideways, using the tube as a compressive load-bearing member. It's to "lift" the coil, rolling it along the ground like an unrolling air mattress, using the tube mostly as a pneumatic line, except the working end, which is acting like a pneumatic piston between the ground beneath and the coil above (or more accurately, beneath-and-slightly-behind and above-and-slightly-ahead-of).


Here is were the breakdown happens: If the tube delivers all of the pressure to the wedge

It's a pressure vessel, and the fluid velocities here are relatively inconsequential. So the pressure is delivered equally over the entire surface, including the wedge.

then the pneumatic piston will move the coil. You are assuming that all the pressure in the tube can only be relieved by expanding the wedge, my position is that except in very narrow conditions the tube will dissipate that pressure by expansion along its length far more readily than in the wedge. A pneumatic tube has thick walls that prevent the tube from stretching so that all of the pressure is applied at the other end. Because of that wall strength, the volume of a pneumatic tube never changes. You are assuming the tube functions mostly as a pneumatic line, mine is that mostly it can't because of its structural properties.

So? The tubing will stretch some (as a function of internal pressure), but that's OK. It doesn't stretch forever. There is some internal pressure sufficient to push the coil, and you simply designed the tubing to withstand that much internal pressure.

It doesn't matter whether the coil is the "first thing" to move. As long as the coil moves without the tubing bursting, it will still deploy.

This tube is thin film polymer, once elasticity is all taken up there is a long phase where increasing pressure physically deforms the material causing it to stretch even more. Generally speaking, once the tube is filled, any increase in pressure is taken up by either elastic or permanent stretching of the film. There is no point where the physical geometry can stay constant with changing pressure. Adding "slightly more gas" is just going to stretch the tube walls. By adding wall thickness you can reduce this but that adds mass quickly and pretty soon your deployment mechanism is far out massing the PV it is supposed to deploy.

Again, you design the tubing so the pressure required to deploy the coil is less than that required to cause permanent stretching or other damage to the tubing.

The second problem is bending. A pneumatic tube can bend without much problem because the thick walls prevent the bends from significantly changing the volume of the pipe. The tube we have here is thin polymer. Any bend will concentrate forces causing localized deformation of the walls as pressure goes up. Volume can't remain constant once bending occurs.

It's not necessary that volume in the "line" remains constant. The system just pumps in more gas until it reaches the deployment pressure. No sweat.

The reason why I say this looks to be just at the edge of whats possible is that there may be some combination of low pressure and tube wall thickness/rigidity that will just barely be enough to move a heavy coil without deforming the tube. Essentially a combo that allows the tube to act as a pneumatic tube but still weak enough to be crushed flat while rolled up all without being more than a small percentage of the PV mass being deployed. If that combo can be found then it can treated as a pneumatic tube and the only remaining problems lay in how to compare two tubes in real-time with sufficient precision to accurately apply different forces on each tube. That is merely a hard problem.

Deforming the tubing is OK, so this nearly-impossible problem doesn't actually need to be solved.

As for the hard problem, since again the fluid velocities are low the pressure in the tubes will be uniform. So you can compare the applied force between tubes with simple pressure sensors.
Title: Re: Power options for a Mars settlement
Post by: Star-Dust on 07/12/2020 08:55 am
Considering the temperetures ranges in Mars (+ =day - night) I was thinking about using elastic potential energy, using water freezing dilatation or any other material, that will push springs and vice versa.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 07/13/2020 08:21 pm
Considering the temperetures ranges in Mars (+ =day - night) I was thinking about using elastic potential energy, using water freezing dilatation or any other material, that will push springs and vice versa.

I'm having a hard time seeing how that would work. Water expands 10% as it freezes, so you'd need a lot of freeze-thaw cycles to deploy a long coil.

Essentially this would be a heat engine driven (indirectly) by solar power. But PV is a much more efficient way to turn solar power into motion.
Title: Re: Power options for a Mars settlement
Post by: su27k on 09/24/2020 04:59 am
This news seems relevant, it looks like SpaceX is indeed looking into nuclear options: Former SpaceX Engineers Tout New Microreactor (https://www.powermag.com/former-spacex-engineers-tout-new-microreactor/)

Quote
Bernauer is a former SpaceX engineer who while there worked on developing energy sources for an eventual Mars colony. Bernauer said he thinks microreactors hold the most promise to supply power for settlements on Mars, and during his research he saw an immediate opportunity to utilize the technology on Earth, which led him to found Radiant along with two other SpaceX colleagues.

Radiant's thread at Advanced Concept section: Radiant Nuclear (https://forum.nasaspaceflight.com/index.php?topic=51988.0)
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 09/24/2020 05:17 am
This news seems relevant, it looks like SpaceX is indeed looking into nuclear options: Former SpaceX Engineers Tout New Microreactor (https://www.powermag.com/former-spacex-engineers-tout-new-microreactor/)

Quote
Bernauer is a former SpaceX engineer who while there worked on developing energy sources for an eventual Mars colony. Bernauer said he thinks microreactors hold the most promise to supply power for settlements on Mars, and during his research he saw an immediate opportunity to utilize the technology on Earth, which led him to found Radiant along with two other SpaceX colleagues.

Radiant's thread at Advanced Concept section: Radiant Nuclear (https://forum.nasaspaceflight.com/index.php?topic=51988.0)
We already knew that.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 09/24/2020 03:20 pm
This news seems relevant, it looks like SpaceX is indeed looking into nuclear options: Former SpaceX Engineers Tout New Microreactor (https://www.powermag.com/former-spacex-engineers-tout-new-microreactor/)

Quote
Bernauer is a former SpaceX engineer who while there worked on developing energy sources for an eventual Mars colony. Bernauer said he thinks microreactors hold the most promise to supply power for settlements on Mars, and during his research he saw an immediate opportunity to utilize the technology on Earth, which led him to found Radiant along with two other SpaceX colleagues.

Radiant's thread at Advanced Concept section: Radiant Nuclear (https://forum.nasaspaceflight.com/index.php?topic=51988.0)
We already knew that.
I didn't.. or else I forgot....
Came here to post the same link.

Super interesting, but only by way of implication.
Title: Re: Power options for a Mars settlement
Post by: kkattula on 10/06/2020 06:24 am
Assuming the high (5 x Earth) deuterium abundance found by Curiosity (also similar results from remote atmospheric sensing) applies globally on Mars, I wonder if a Heavy Water reactor like the CANDU or ACR would be practical long term on Mars?

 - They can use natural uranium, thorium or LEU including 0.9% Recovered Uranium from conventional reactors.

 - There's no large pressure vessel, instead multiple small high pressure tubes that would be easier to ship from Earth, pre fueled.

 - Much less proliferation issue with no enrichment.

Obviously it would need the infrastructure to produce the heavy water, but it should be a lot more efficient than on Earth due to the high abundance, and heavy water is the most expensive component of those type of reactors.


Note: I doubt water for human consumption or agriculture would need to have excess heavy water removed as the natural concentration is still very low, but it wouldn't hurt if the heavy water was needed for other purposes anyway.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 10/07/2020 10:50 am
Assuming the high (5 x Earth) deuterium abundance found by Curiosity (also similar results from remote atmospheric sensing) applies globally on Mars, I wonder if a Heavy Water reactor like the CANDU or ACR would be practical long term on Mars?

 - They can use natural uranium, thorium or LEU including 0.9% Recovered Uranium from conventional reactors.

 - There's no large pressure vessel, instead multiple small high pressure tubes that would be easier to ship from Earth, pre fueled.

 - Much less proliferation issue with no enrichment.

Obviously it would need the infrastructure to produce the heavy water, but it should be a lot more efficient than on Earth due to the high abundance, and heavy water is the most expensive component of those type of reactors.


Note: I doubt water for human consumption or agriculture would need to have excess heavy water removed as the natural concentration is still very low, but it wouldn't hurt if the heavy water was needed for other purposes anyway.

It might be a possibility in the distant future. But there are at least two big issues. Firstly regulatory issues on Earth with launching large quantities of radioactive material into space which would probably cause significant delay.

Secondly and more importantly, the huge amount of power required to concentrate heavy water, heavy water is expensive because of the power needed to refine it. Power is likely to be very short supply on Mars for decades so a hugely energy intensive  deuterium plant would not be helpful. Even though it might enable a lot of power eventually there would be a very big energy mountain to climb to get there.
Title: Re: Power options for a Mars settlement
Post by: Pete on 10/07/2020 11:10 am

Secondly and more importantly, the huge amount of power required to concentrate heavy water, heavy water is expensive because of the power needed to refine it. ...

Could you elucidate of this matter please. What do you call "huge", for both the power requirements and price?

Even in small lots, one can buy high-purity D2O for about $500/kg

And that cost comes from tacking enough "9"s to the purity figure, not the basic extraction.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 10/07/2020 12:14 pm

Secondly and more importantly, the huge amount of power required to concentrate heavy water, heavy water is expensive because of the power needed to refine it. ...

Could you elucidate of this matter please. What do you call "huge", for both the power requirements and price?

Even in small lots, one can buy high-purity D2O for about $500/kg

And that cost comes from tacking enough "9"s to the purity figure, not the basic extraction.
There are a number of processes for making heavy water, they are not complex, but they are energy intensive. The majority of the cost comes from processing the huge volume of water needed because the heavy water concentration is so low and the processes are not that efficient. Increasing the concentration would help but I doubt it would help that much.

I don’t have a specific value for the energy cost, but IMO it will be 90% of the cost of the process as the water input is free and the process is simple. Even at $10/kg that’s a lot of electricity. Interesting to note in the example below that the process was considered at the Aswan dam – presumably because of the availability of a lot of relatively cheap electricity and also in combination with an ammonia plant where a hydrogen gas source would be available.

https://cns-snc.ca/media/Bulletin/A_Miller_Heavy_Water.pdf
https://www.iaea.org/sites/default/files/publications/magazines/bulletin/bull1-1/01102001314.pdf
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 10/07/2020 12:44 pm

Secondly and more importantly, the huge amount of power required to concentrate heavy water, heavy water is expensive because of the power needed to refine it. ...

Could you elucidate of this matter please. What do you call "huge", for both the power requirements and price?

Even in small lots, one can buy high-purity D2O for about $500/kg

And that cost comes from tacking enough "9"s to the purity figure, not the basic extraction.
A CANDU reactor needs about 250 tonnes of DO to work.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 10/07/2020 05:02 pm

Secondly and more importantly, the huge amount of power required to concentrate heavy water, heavy water is expensive because of the power needed to refine it. ...

Could you elucidate of this matter please. What do you call "huge", for both the power requirements and price?

Even in small lots, one can buy high-purity D2O for about $500/kg

And that cost comes from tacking enough "9"s to the purity figure, not the basic extraction.
A CANDU reactor needs about 250 tonnes of DO to work.

Isn't the usual process to make D2O to run a electrolyzer (sp?) and accumulate the D2O as the O2 and H2 get evolved?

They will be running a d lot of electrolysis to get the H2 and O2.
Might be a by product.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 10/07/2020 10:24 pm

Secondly and more importantly, the huge amount of power required to concentrate heavy water, heavy water is expensive because of the power needed to refine it. ...

Could you elucidate of this matter please. What do you call "huge", for both the power requirements and price?

Even in small lots, one can buy high-purity D2O for about $500/kg

And that cost comes from tacking enough "9"s to the purity figure, not the basic extraction.
A CANDU reactor needs about 250 tonnes of DO to work.

Isn't the usual process to make D2O to run a electrolyzer (sp?) and accumulate the D2O as the O2 and H2 get evolved?

They will be running a d lot of electrolysis to get the H2 and O2.
Might be a by product.
There are a multitude of processes for separating D2O (see my reference up thread), electrolysis has been used and may well still be used in some cases, but I believe the hydrogen sulphide process is preferred these days. What they decide to do on Mars will undoubtedly be best for the very specific conditions on Mars. But it will probably involve a lot of kit, a lot of energy and won't be happening anytime soon.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/09/2020 08:56 pm
Schottky-junction transition metal dichalcogenide photovoltaics

A record-setting 2019 perovskite solar cell achieved specific power of 29.4 kW/kg (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1954068#msg1954068).

Went et al. 2019 (https://advances.sciencemag.org/content/5/12/eaax6061) describes a new manufacturing procedure for Schottky-junction transition metal dichalcogenide photovoltaics, with stated potential to achieve specific power > 50 kW/kg.  Even under Mars lighting, panels composed of such cells would have potential to give multi-GW max power from a single Starship payload.

Quote from: Went et al. 2019
We highlight areas for improvement by simulating the behavior of optimized devices based on this architecture and show 8.9% simulated efficiency and 58-kW/kg simulated specific power in a device with transparent top contacts, optimized thickness, and ideal metal work functions for carrier extraction.

Given the proof-of-concept performance and the clear pathways for improvement presented here for devices less than 150 nm thick, ultrathin vertical Schottky-junction TMD solar cells with transferred contacts are promising candidates for high specific power photovoltaic applications.

Quote from: Went et al. 2019
Fig. 2 Metal transfer process.

Briefly, a self-assembled monolayer (SAM) is applied to a clean SiO2/Si substrate (I).

Au is deposited in an electron beam evaporator (II).

Disk contacts are defined using photolithography (III), and the surrounding Au is etched away (IV).

To peel the contacts, a polydimethylsiloxane (PDMS)/polypropylene carbonate (PPC) stamp is laminated to the contacts, heated above the glass transition temperature of PPC, and then cooled and removed quickly (V).

To print the contacts, the PDMS/PPC stamp is aligned and laminated onto the device and then peeled away slowly above the glass transition temperature of PPC, leaving the contacts behind (VI).

Related work in Svatek et al. 2020 (https://arxiv.org/pdf/2009.13911).

Refs.

Svatek, S.A., Bueno-Blanco, C., Lin, D.Y., Kerfoot, J., Macías, C., Zehender, M.H., Tobías, I., García-Linares, P., Taniguchi, T., Watanabe, K. and Beton, P., 2020. High open-circuit voltage in transition metal dichalcogenide solar cells. (https://arxiv.org/pdf/2009.13911) Nano Energy, p.105427.

Went, C.M., Wong, J., Jahelka, P.R., Kelzenberg, M., Biswas, S., Hunt, M.S., Carbone, A. and Atwater, H.A., 2019. A new metal transfer process for van der Waals contacts to vertical Schottky-junction transition metal dichalcogenide photovoltaics. (https://advances.sciencemag.org/content/5/12/eaax6061) Science advances, 5(12), p.eaax6061.
Title: Re: Power options for a Mars settlement
Post by: ThereIWas3 on 10/09/2020 10:47 pm
Something to consider about exotic material semiconductors shipped from Earth for these new solar panels is, how sensitive are they to damage from cosmic radiation enroute?  It would be a pain to lose an entire shipment due to a solar storm.  Crew can hide in a storm shelter, but not the cargo.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/10/2020 04:09 am
Something to consider about exotic material semiconductors shipped from Earth for these new solar panels is, how sensitive are they to damage from cosmic radiation enroute?

E.g., this Schottky junction (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2141005#msg2141005) is just Au, Ag, and WS2, all used in spacecraft. 

Ag can tarnish in martian (trace) O2 and H2S, but here it's covered by WS2 and Au; not exposed to the elements.  Likewise, Ag in the previously noted (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1954068#msg1954068) solar cells.

WS2 is an inert spacecraft lubricant.

"Exotic"?
Title: Re: Power options for a Mars settlement
Post by: Lar on 10/13/2020 11:20 pm
Something to consider about exotic material semiconductors shipped from Earth for these new solar panels is, how sensitive are they to damage from cosmic radiation enroute?

E.g., this Schottky junction (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2141005#msg2141005) is just Au, Ag, and WS2, all used in spacecraft. 

Ag can tarnish in martian (trace) O2 and H2S, but here it's covered by WS2 and Au; not exposed to the elements.  Likewise, Ag in the previously noted (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1954068#msg1954068) solar cells.

WS2 is an inert spacecraft lubricant.

"Exotic"?

Please expand WS2.

Aren't there also complex hydrocarbons involved?
Quote
To peel the contacts, a polydimethylsiloxane (PDMS)/polypropylene carbonate (PPC) stamp is laminated to the contacts.
 

Or is that discarded or reused and not present on the final product?
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/14/2020 11:13 am
Something to consider about exotic material semiconductors shipped from Earth for these new solar panels is, how sensitive are they to damage from cosmic radiation enroute?

E.g., this Schottky junction (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2141005#msg2141005) is just Au, Ag, and WS2, all used in spacecraft. 

Ag can tarnish in martian (trace) O2 and H2S, but here it's covered by WS2 and Au; not exposed to the elements.  Likewise, Ag in the previously noted (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1954068#msg1954068) solar cells.

WS2 is an inert spacecraft lubricant.

"Exotic"?

Please expand WS2.

Aren't there also complex hydrocarbons involved?
Quote
To peel the contacts, a polydimethylsiloxane (PDMS)/polypropylene carbonate (PPC) stamp is laminated to the contacts.
 

Or is that discarded or reused and not present on the final product?

WS2 is tungsten disulfide.

"the PDMS/PPC stamp is... laminated onto the device and then peeled away..., leaving the contacts behind..."
Title: Re: Power options for a Mars settlement
Post by: DigitalMan on 10/19/2020 09:42 pm
The articles about 'hot carrier' solar cells potentially being able to reach 66% efficiency are interesting both here on Earth and Mars. If they could be inexpensive to manufacture it could be hard to beat the cost.
Title: Re: Power options for a Mars settlement
Post by: Pete on 10/21/2020 11:21 am
If they could be inexpensive to manufacture it could be hard to beat the cost.

This is about as fluffy of a statement as could possibly be made.
You might as well state "if it can be made lighter it would weigh less",
or "if it could be made of common materials, then sourcing materials to make it would be easy".

Absolute non-statement statements!
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 10/22/2020 08:26 pm

Ag can tarnish in martian (trace) O2 and H2S, but here it's covered by WS2 and Au; not exposed to the elements.  Likewise, Ag in the previously noted (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1954068#msg1954068) solar cells.

WS2 is an inert spacecraft lubricant.

"Exotic"?
Molybdenum Disulphide ("Moly") is indeed a common solid lubricant, frequently in vacuum applications. It has a layered structure quite like graphite.
Tungsten Silicide I've heard of being used for semiconductor conductor layers on chips.

I'm not sure I've ever heard of tungsten disulphide being used for anything.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 10/23/2020 06:45 am
Just a reminder. Last time I looked Musk's solar company (has it been folded into Tesla or sold off?) had no experience of thin film PV.

It was all (IIRC) single crystal silicon.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 10/23/2020 06:49 am
Something to consider about exotic material semiconductors shipped from Earth for these new solar panels is, how sensitive are they to damage from cosmic radiation enroute?  It would be a pain to lose an entire shipment due to a solar storm.  Crew can hide in a storm shelter, but not the cargo.
Excellent question.

The consequences of discovering your PV array efficiency had sunk through the floor because the cells had been cooked on the trip would be serious.  :(

How many of these advanced cell technologies been radiation tested? On orbit tested?

OTOH there is decades of data on what on orbit exposure does to a number of cell materials over long periods, along with various protective options and (in some case) possible (but untried) repair options.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/23/2020 10:26 am
Just a reminder. Last time I looked Musk's solar company (has it been folded into Tesla or sold off?) had no experience of thin film PV.

It was all (IIRC) single crystal silicon.
It's been folded into Tesla and the solar roof.  I would expect them to build on the SpaceX experience of the Dragon capsules and the satellite constellation for solar cells in Space.  The Tesla work work is much more about integration into tiles and buildings.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/23/2020 12:54 pm

WS2 is an inert spacecraft lubricant.


I'm not sure I've ever heard of tungsten disulphide being used for anything.  :(

::)... (https://spinoff.nasa.gov/Spinoff2015/ip_7.html)
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 10/23/2020 02:04 pm
Just a reminder. Last time I looked Musk's solar company (has it been folded into Tesla or sold off?) had no experience of thin film PV.

It was all (IIRC) single crystal silicon.
In all of his companies he seems to go to first principles, and make advances and new products.

Although (this tweet about) the Tesla Solar Roof does not prove they have done anything with thin film, it is here to point out that it has not been "sold off", and remains a key plank of Tesla's vision..... ?
https://twitter.com/Tesla/status/1317251873687113730?s=20
Title: Re: Power options for a Mars settlement
Post by: yg1968 on 10/15/2021 01:49 pm
Interesting that SpaceX has/had employees looking at portable nuclear reactors:

https://twitter.com/IntEngineering/status/1448999386646786048

Ex-SpaceX Engineers Are Building a Cheap, Portable Nuclear Reactor
Technology designed for future Mars colonies is 'making nuclear power portable' on Earth.

https://interestingengineering.com/ex-spacex-engineers-are-building-a-cheap-portable-nuclear-reactor?utm_source=Twitter&utm_medium=Article&utm_campaign=organic&utm_content=Oct15

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 10/17/2021 03:52 am
Unsullied link: https://interestingengineering.com/ex-spacex-engineers-are-building-a-cheap-portable-nuclear-reactor

Interesting that SpaceX has/had employees looking at portable nuclear reactors:

Just so we're clear, these should be read as "employees SpaceX had" (ie ex-SpaceXers) are looking at building portable nuclear reactors.

There's still zero evidence that SpaceX is/was looking at building portable nuclear reactors.
Title: Re: Power options for a Mars settlement
Post by: su27k on 10/17/2021 05:08 am
Unsullied link: https://interestingengineering.com/ex-spacex-engineers-are-building-a-cheap-portable-nuclear-reactor

Interesting that SpaceX has/had employees looking at portable nuclear reactors:

Just so we're clear, these should be read as "employees SpaceX had" (ie ex-SpaceXers) are looking at building portable nuclear reactors.

There's still zero evidence that SpaceX is/was looking at building portable nuclear reactors.

The article said the engineer considered nuclear reactors as power source for Mars colony when he was working at SpaceX: "Radiant founder and CEO Doug Bernauer is a former SpaceX engineer who worked on developing energy sources for a future Mars colony during his time at the private space enterprise. During his research into microreactors for Mars, he saw an opportunity for developing a flexible, affordable power source here on Earth"

So SpaceX looked at nuclear reactors, yes. SpaceX building nuclear reactors, probably not.
Title: Re: Power options for a Mars settlement
Post by: Oersted on 10/17/2021 02:18 pm
Just a reminder. Last time I looked Musk's solar company (has it been folded into Tesla or sold off?) had no experience of thin film PV.

It was all (IIRC) single crystal silicon.

What does Tesla Solar put into their roof tiles? - Isn't it thin film PV?
Title: Re: Power options for a Mars settlement
Post by: oiorionsbelt on 10/17/2021 03:19 pm
 
Quote
Gwynne Shotwell said in 2017 that SpaceX are having difficulties with the US government in obtaining nuclear material for research for SpaceX's nuclear program.

https://sites.google.com/site/exosnews/spacex/spacex-nuclear
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 10/17/2021 03:30 pm

Ag can tarnish in martian (trace) O2 and H2S, but here it's covered by WS2 and Au; not exposed to the elements.  Likewise, Ag in the previously noted (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1954068#msg1954068) solar cells.

WS2 is an inert spacecraft lubricant.

"Exotic"?
Molybdenum Disulphide ("Moly") is indeed a common solid lubricant, frequently in vacuum applications. It has a layered structure quite like graphite.
Tungsten Silicide I've heard of being used for semiconductor conductor layers on chips.

I'm not sure I've ever heard of tungsten disulphide being used for anything.  :(
It's available from Amazon - its used as a high temperature lubricant.
https://www.amazon.com/MICROLUBROL-TUNGSTEN-DISULFIDE-Sulfide-Powder/dp/B00WP4306U (https://www.amazon.com/MICROLUBROL-TUNGSTEN-DISULFIDE-Sulfide-Powder/dp/B00WP4306U)
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 10/17/2021 03:47 pm
Just a reminder. Last time I looked Musk's solar company (has it been folded into Tesla or sold off?) had no experience of thin film PV.

It was all (IIRC) single crystal silicon.

What does Tesla Solar put into their roof tiles? - Isn't it thin film PV?

I have tesla solar on my roof. (not roof tiles)

33 panels of rec peak energy z-link series
rec-260pe z-link
260W

Single crystal silicon.
They are 5 years old now.
Title: Re: Power options for a Mars settlement
Post by: butters on 10/17/2021 05:09 pm
Quote
Gwynne Shotwell said in 2017 that SpaceX are having difficulties with the US government in obtaining nuclear material for research for SpaceX's nuclear program.

https://sites.google.com/site/exosnews/spacex/spacex-nuclear
That's not at all surprising. If they were pursuing a helium-cooled pebble bed reactor, the majority of the technical challenge is nailing the design and fabrication of the fuel particles. Under the Obama-era regulatory reforms that loosened up restrictions on the development of prototype-scale nuclear reactors, private prototype reactors must use ceramic oxide LEU fuel assemblies fabricated by an approved supplier.

Private companies really can't develop a pebble bed or traveling wave or dissolved-fuel molten salt reactor in the United States. The magic of Kilopower is that it's a NASA project, and as a government agency, they can develop a sodium-cooled reactor with a high-enriched metallic uranium core. NASA can get their hands on that stuff, and with it they can develop a reactor that runs for 20+ years on a single fuel load.

There are all sorts of interesting pebble bed reactor concepts around, from golf balls down to sand and with various unique twists, but the history of these reactors shows that most of the safety and operating characteristics are baked into the fuel, and it's prohibitively onerous to iterate on the fuel design -- if it's possible to get any fuel pebbles fabricated at all. It's a history littered with failed projects that never had a second chance to develop an improved fuel spec.

Nobody is going to be developing nuclear reactors for space applications that run on industry-standard fuel assemblies. There's not going to be NuScale reactors on Mars, and that's about as innovative as it gets under current regulations. Only NASA or DoD have the authority necessary to develop reactors that are appropriate for off-world missions.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 10/17/2021 09:51 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 10/20/2021 08:16 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/20/2021 08:35 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.
Agreed, although turning off fuel and food production for the duration of a storm would reduce demand to a small fraction of the peak load.  An extra Martian winter in a way.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 10/21/2021 04:38 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.
Agreed, although turning off fuel and food production for the duration of a storm would reduce demand to a small fraction of the peak load.  An extra Martian winter in a way.
As long as there's a reasonable overproduction margin, fuel production can be curtailed with the caveat that some processes don't like a restart cycle. Same for food production with the caveat that in the medium to long term plants need some light with its daily cycle.


Another savings would be curtailing outdoor activity. Construction and travel would be traded off for inside maintenance and poker. Little used spaces can be closed off to minimize air circulation and thermal control.


What I actually had in mind in the post was truck air conditioning units designed to work on battery power. A gent I spoke with that worked at and probably owned one of the pioneering efforts emphasized how much work he put into the AC efficiency. Variable blower speed and possibly (it was ~10 years ago) variable compressor speed. Motor types chosen for power efficiency. There are lots of trades available in all systems and the choices always depend on the optimization looked for. How much mass is worth what power savings is one example.
Title: Re: Power options for a Mars settlement
Post by: Mark K on 10/21/2021 08:25 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.

I would think some big methane/oxygen fuel cells would be appropriate once things get going. You will be making tons of the stuff anyway. This would be in place of batteries and for times like dust storms.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 10/22/2021 05:06 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.

I would think some big methane/oxygen fuel cells would be appropriate once things get going. You will be making tons of the stuff anyway. This would be in place of batteries and for times like dust storms.

How hard is to build methane/oxygen fuel cells on Mars? 
For a long time batteries from Earth will be most mass efficient backup power solution.  Shipping fuel cells from Earth won't be worth it.  If they can be built locally when they add dissimilar redundancy to the backup power system. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/22/2021 05:50 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.

I would think some big methane/oxygen fuel cells would be appropriate once things get going. You will be making tons of the stuff anyway. This would be in place of batteries and for times like dust storms.

How hard is to build methane/oxygen fuel cells on Mars? 
For a long time batteries from Earth will be most mass efficient backup power solution.  Shipping fuel cells from Earth won't be worth it.  If they can be built locally when they add dissimilar redundancy to the backup power system.
The fuel cell is not the energy storage though, it's the energy conversion system.  Batteries would be many orders of magnitude heavier than a fuel cell, or a dedicated small gas turbine or a heavily modified gas genset at settlement scale.
Batteries are more suited for night time short term storage where they are much more efficient that fuel cells or combustion systems.
It'll be really hard to build either fuel cells, gensets or turbines on Mars for quite some time.  Easier to bring these from Earth.  Fuel tanks will be pretty easy though, likely the first tanks we probably be repurposed Starships.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 10/22/2021 07:40 pm
I would think some big methane/oxygen fuel cells would be appropriate once things get going. You will be making tons of the stuff anyway. This would be in place of batteries and for times like dust storms.

How hard is to build methane/oxygen fuel cells on Mars? 
For a long time batteries from Earth will be most mass efficient backup power solution.  Shipping fuel cells from Earth won't be worth it.  If they can be built locally when they add dissimilar redundancy to the backup power system. 

It doesn't matter if batteries are more efficient as a backup power solution than methane/oxygen fuel cells. The latter are a backup power solution and you'd feel pretty stupid if something happened to your batteries etc and you had all that methane and oxygen standing there with no means to utilise it. Belt and braces (UK)/suspenders (US). (You could use an ICE generator rather than fuel cells, but the principle is the same.)
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 10/23/2021 05:52 am
Even the best closed life support systems produce excess carbon which needs to be returned to the system. You can burn this excess biomass to keep warm or turn a generator.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 10/23/2021 06:31 pm
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 10/27/2021 08:54 pm
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?

In my opinion the answer is yes for emergency power.  Then again based on the data we have a bad Martian dust storm "only" reduces solar power by 99% so shutting down propellant production could be sufficient.  The question becomes how much power do the early settlers need to survive a dust storm?

When it comes to base load, I'm not sure how applicable the concept is to an early Martian settlement.  The propellant plant is going to dominate power requirements and electrolysis can be done when the sun is shining.  Hydrogen can be stored for overnight conversion in metal hydrides.  The Sabatier reaction is exothermic with an output temperature of ~350 C so we can utilize this heat source instead of stored/generated electricity at night.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 10/27/2021 09:55 pm
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?

In my opinion the answer is yes for emergency power.  Then again based on the data we have a bad Martian dust storm "only" reduces solar power by 99% so shutting down propellant production could be sufficient.  The question becomes how much power do the early settlers need to survive a dust storm?

When it comes to base load, I'm not sure how applicable the concept is to an early Martian settlement.  The propellant plant is going to dominate power requirements and electrolysis can be done when the sun is shining.  Hydrogen can be stored for overnight conversion in metal hydrides.  The Sabatier reaction is exothermic with an output temperature of ~350 C so we can utilize this heat source instead of stored/generated electricity at night.

Seems right. At the darkest conditions ever reported (10.8 tau recorded by Opportunity right before the rover failed) the solar panels were still producing 22 Wh/sol, or about 2.5% of their maximum power (900 Wh/sol).

Note that while the solar power output was at 2.5%, the tau value indicates that the transmitted light was only e-10.8 = 0.002% (a factor of >1000x different). This is because the tau value only measures transmitted light and completely ignores scattered light.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 10/27/2021 10:25 pm
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?

In my opinion the answer is yes for emergency power.  Then again based on the data we have a bad Martian dust storm "only" reduces solar power by 99% so shutting down propellant production could be sufficient.  The question becomes how much power do the early settlers need to survive a dust storm?

When it comes to base load, I'm not sure how applicable the concept is to an early Martian settlement.  The propellant plant is going to dominate power requirements and electrolysis can be done when the sun is shining.  Hydrogen can be stored for overnight conversion in metal hydrides.  The Sabatier reaction is exothermic with an output temperature of ~350 C so we can utilize this heat source instead of stored/generated electricity at night.
I assume that base load is that necessary to keep minimum necessary systems running. Things like light, heat, communications, air circulation, electronics cooling, CO2 scrubbing and food prep. Maybe a few other things like agricultural tests that would loose a lot if they had to start over. Does ISS consumption teach us anything about how much this might be or are the conditions so different that a comparison is useless?


Is an electrical budget of 1kW/day/person anywhere near the mark? If so, a 10kW kilopower would support a crew of 10 indefinitely, but with no reserves.


A quick check of the Oracle shows nothing new on Kilopower since the March 2018 KRUSTY tests. Anybody have a pointer to anything newer?
Title: Re: Power options for a Mars settlement
Post by: MickQ on 10/27/2021 11:14 pm
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?

In my opinion the answer is yes for emergency power.  Then again based on the data we have a bad Martian dust storm "only" reduces solar power by 99% so shutting down propellant production could be sufficient.  The question becomes how much power do the early settlers need to survive a dust storm?

When it comes to base load, I'm not sure how applicable the concept is to an early Martian settlement.  The propellant plant is going to dominate power requirements and electrolysis can be done when the sun is shining.  Hydrogen can be stored for overnight conversion in metal hydrides.  The Sabatier reaction is exothermic with an output temperature of ~350 C so we can utilize this heat source instead of stored/generated electricity at night.

BUT,  if prop production is shut down during a month, or two or three, long dust storm then you don't have that heat from the Sabatier reaction, right ?    Or am I missing something ??
Title: Re: Power options for a Mars settlement
Post by: Nevyn72 on 10/28/2021 12:00 am
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?

In my opinion the answer is yes for emergency power.  Then again based on the data we have a bad Martian dust storm "only" reduces solar power by 99% so shutting down propellant production could be sufficient.  The question becomes how much power do the early settlers need to survive a dust storm?

When it comes to base load, I'm not sure how applicable the concept is to an early Martian settlement.  The propellant plant is going to dominate power requirements and electrolysis can be done when the sun is shining.  Hydrogen can be stored for overnight conversion in metal hydrides.  The Sabatier reaction is exothermic with an output temperature of ~350 C so we can utilize this heat source instead of stored/generated electricity at night.

BUT,  if prop production is shut down during a month, or two or three, long dust storm then you don't have that heat from the Sabatier reaction, right ?    Or am I missing something ??

You also have all the Methane and Oxygen you have been producing for return flight.

Some of this could be 'appropriated' during emergencies to produce power.
Whatever method you use, (ICE, turbine, or fuel cell), waste heat would be generated that could be used.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 10/28/2021 01:01 am
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?

In my opinion the answer is yes for emergency power.  Then again based on the data we have a bad Martian dust storm "only" reduces solar power by 99% so shutting down propellant production could be sufficient.  The question becomes how much power do the early settlers need to survive a dust storm?

SNIP
I assume that base load is that necessary to keep minimum necessary systems running. Things like light, heat, communications, air circulation, electronics cooling, CO2 scrubbing and food prep. Maybe a few other things like agricultural tests that would loose a lot if they had to start over. Does ISS consumption teach us anything about how much this might be or are the conditions so different that a comparison is useless?


Is an electrical budget of 1kW/day/person anywhere near the mark? If so, a 10kW kilopower would support a crew of 10 indefinitely, but with no reserves.

I don't know.  I am a voracious reader of topics devoted to Martian colonization and I don't recall coming across an in-depth analysis of minimum power requirements for surviving a dust storm.

What I do know is that solar power production won't drop to zero.  The solar farm for propellant production should provide at least a few tens of kWh/sol even during the worst recorded storm.  Depending on how much power is actually needed this could be enough so that reserves like stored energy in batteries and methalox don't need to be used.  In this case kilopower would be dissimilar redundancy.

Not that dissimilar redundancy is a bad thing, especially when trying to establish a foothold on a hostile alien world.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 10/28/2021 01:27 am
BUT,  if prop production is shut down during a month, or two or three, long dust storm then you don't have that heat from the Sabatier reaction, right ?    Or am I missing something ??

What you are missing is that I prefer to use the heat for propellant plant processes that consume energy overnight.  If propellant production is shut down these processes won't be consuming energy.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 10/28/2021 01:30 am
One piece of information I believe is useful for the current line of discussion is the discovery that Martian temperatures increase during dust storms.  This means lower than normal power requirements are needed for heating.

Quote
The impact of Mars's 2018 Global Dust Storm (GDS) on surface and near-surface air temperatures was investigated using an assimilation of Mars Climate Sounder observations. Rather than simply resulting in cooling everywhere from solar absorption (average surface radiative flux fell 26 W/m2), the globally averaged result was a 0.9-K surface warming. These diurnally averaged surface temperature changes had a novel, highly nonuniform spatial structure, with up to 16-K cooling/19-K warming. Net warming occurred in low thermal inertia regions, where rapid nighttime radiative cooling was compensated by increased longwave emission and scattering. This caused strong nightside warming, outweighing dayside cooling. The reduced surface-air temperature gradient closely coupled surface and air temperatures, even causing local dayside air warming. Results show good agreement with Mars Climate Sounder surface temperature retrievals. Comparisons with the 2001 GDS and free-running simulations show that GDS spatial structure is crucial in determining global surface temperature effects.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL083936
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 10/28/2021 02:13 am
Power requirements during a dust storm can be quite low, because you can use stored consumables instead of power-hungry closed loop life support.

No need to generate breathing oxygen, since you can just draw oxygen directly from tanks.

No need to generate potable water or food. Both can be stockpiled in ample amount.

No need to desorb CO2 either (ala the ISS CDRA). Simple one-use LiOH canisters would only mass 7 kg per person per month.* These canisters could be regenerated and re-stockpiled after the dust storm by heating them and exposing them to vacuum.




* this should be treated as a conservative estimate, since my baseline is ancient: the Apollo CM canisters weighed 13 oz and supplied 3 people for 12 hours
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 10/28/2021 02:32 am
One thing that probably would make sense to run "closed loop" would be humidity removal.

Of course this would extend the potable water supply and avoid venting precious water. But more than that, it acts as a 200+% efficient space heater by recovering the latent heat of water vapor. My 200% figure comes from this blog post on the subject (https://coldhousejournal.wordpress.com/2010/01/27/efficiency-bathroom-humidity/), so those efficiency measurements were taken on a unit manufactured 10+ years ago; no doubt efficiencies have improved since then.

Quote
The dehumidifier (running) uses about 400 watts to power its fan and compressor.  All of that winds up as heat...  Moreover, it claims to condense 1.6 liters of water for each 1 kWh of electricity it uses– which about agrees with what I’ve observed.  Now, each liter of steam condensed back to liquid releases a further 3,600 BTU of heat, which equals roughly 1 kWh also.  So, for each kWh of electricity used to run the dehumidifier, we get back 2 kWh of heat..  It is, effectively, like a 200% efficient space heater.  Plus, we get a quart of distilled water every day
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 10/28/2021 04:50 am
There is enough energy in the martian wind to keep dust suspended for months. Is it possible to design a practical wind turbine to use that energy? The wind turbines would probably not be useful much of the time, but they might be useful precisely when the solar panels are least useful.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 10/28/2021 05:16 am
There is enough energy in the martian wind to keep dust suspended for months. Is it possible to design a practical wind turbine to use that energy? The wind turbines would probably not be useful much of the time, but they might be useful precisely when the solar panels are least useful.

Some previous work that seems to validate this idea:

https://www.nasa.gov/centers/ames/news/releases/2001/01_72AR.html

Quote
"Wind power and solar power may complement each other on Mars. When you have a large dust storm blocking the sunlight on Mars, a wind turbine can still generate electricity," said scientist David Bubenheim of NASA’s Ames Research Center in California’s Silicon Valley.

"Only during dust storms on Mars is there enough wind energy to operate a wind turbine," said Michael Flynn, another NASA Ames scientist. On Earth about 10 meters (33 feet) per second wind speed is needed to make electricity with wind turbines; on Mars about 30 meters (98 feet) is needed because of the extremely thin air, according to Bubenheim.

"What we are proposing is a hybrid wind-solar system," Flynn said. "This system would use solar cells to generate electricity during sunny periods, and a wind turbine to make electricity during dust storms."

"We’ve looked at wind profiles based on atmospheric computer models of Mars," Bubenheim said. A scheme of complementary wind and solar power appears to be an option, he added.

https://spinoff.nasa.gov/Spinoff2013/ee_5.html

Quote
“It all started with ecological life support systems for exploration,” says David Bubenheim, a senior research scientist at NASA’s Ames Research Center. Sometimes referred to as regenerative life support systems, the concept includes an enclosed self-sufficient habitat that can independently support life for years on end. Such a system aims not only to produce its own food and water but to purify air and convert waste into useful byproducts.

In the early 1990s, NASA was planning for an extended stay on Mars, and Bubenheim and his Ames colleagues were concentrating efforts on creating a complete ecological system to sustain human crewmembers during their time on the Red Planet.

“The main barrier to developing such a system,” he says, “is energy.” Mars has no power plants, and a regenerative system requires equipment that runs on electricity to do everything from regulating humidity in the atmosphere to monitoring the quality of recycled water.

The Ames group started looking at maximizing energy use efficiency and alternative methods to make power on a planet that is millions of miles away from Earth. They turned to a hybrid concept combining two renewable sources: wind and solar power technologies. Large surface temperature swings on Mars produce windy conditions; extreme examples are the frequent dust storms that can block nearly all sunlight. “When there’s a dust storm and the wind is blowing, the wind system could be the dominant power source. When the wind is not blowing and the sun is shining on the surface, photovoltaics could be the dominant source,” says Bubenheim.

Still trying to find more about this early 90s effory Bubenheim references...

Here's the tech now (spec sheet attached): https://www.nps100.com/wp/nps100c/

Title: Re: Power options for a Mars settlement
Post by: Paul451 on 10/28/2021 06:14 am
Some previous work that seems to validate this idea:

Well, for particularly small values of "validate".

Quote
"Only during dust storms on Mars is there enough wind energy to operate a wind turbine," said Michael Flynn, another NASA Ames scientist. On Earth about 10 meters (33 feet) per second wind speed is needed to make electricity with wind turbines; on Mars about 30 meters (98 feet) is needed because of the extremely thin air, according to Bubenheim.

The highest recorded wind speed on Mars was just under 32 m/s.

Even during dust storms, it rarely gets near (let alone over) 30 m/s. It's not just that the atmosphere is thinner, wind speeds also tend to be low on Mars, compared to Earth. (Which makes sense. Less pressure exists to have a pressure difference.) Wind turbines don't make a lot of sense on Mars.

(Maybe kite-turbines, if there's more wind at height?)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 10/28/2021 09:33 am
they might be useful precisely when the solar panels are least useful.
Some previous work that seems to validate this idea:

Well, for particularly small values of "validate".

Quote
"Only during dust storms on Mars is there enough wind energy to operate a wind turbine," said Michael Flynn, another NASA Ames scientist.

On the contrary, that juxtaposition perfectly illustrates my point. Thanks. :)

Quote
On Earth about 10 meters (33 feet) per second wind speed is needed to make electricity with wind turbines; on Mars about 30 meters (98 feet) is needed because of the extremely thin air, according to Bubenheim.

The highest recorded wind speed on Mars was just under 32 m/s.

That's why I attached the brochure. The cut-in speed of the NASA-derived technology wind turbines is only 2.5 meters per second (vs the 10 m/s quoted), and it's designed for wind speeds "lower than 6.0 m/s." Naturally the brochure written for commercial operators, so this is listed as the "average annual" wind speed, but if the turbine were being used on Mars in a contingency power role this would correspond to the "dust storm" wind speed.

It's also important to ask, what altitude above the ground was that 32 m/s measured at? If it was from Viking then the wind speed sensor was located approximately 1.5 meters off the ground, vs. 30-40 meters off the ground for a wind turbine.

Wind turbines would also preferentially be built on naturally occurring ridge-lines, to benefit from local topology funneling and accelerating the wind speed. This is similar to how wind power is used in Antarctica (https://www.power-technology.com/projects/rossislandwindfarm/).

All-in-all, I'm seeing a pretty large value of "validate."  :D  This is especially true considering how much electricity demand can be reduced during the dust storm (per the discussion above).
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 10/28/2021 10:30 am
Some previous work that seems to validate this idea:

Well, for particularly small values of "validate".

Quote
"Only during dust storms on Mars is there enough wind energy to operate a wind turbine," said Michael Flynn, another NASA Ames scientist. On Earth about 10 meters (33 feet) per second wind speed is needed to make electricity with wind turbines; on Mars about 30 meters (98 feet) is needed because of the extremely thin air, according to Bubenheim.

The highest recorded wind speed on Mars was just under 32 m/s.

Even during dust storms, it rarely gets near (let alone over) 30 m/s. It's not just that the atmosphere is thinner, wind speeds also tend to be low on Mars, compared to Earth. (Which makes sense. Less pressure exists to have a pressure difference.) Wind turbines don't make a lot of sense on Mars.

(Maybe kite-turbines, if there's more wind at height?)

That speed was from a ground station. Winds are indeed much faster higher up from the surface, up to 100m/s (based on dust devil track speeds). There are also fairly steady and directional crater winds which can provide a lower level of daily power production.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/28/2021 02:30 pm
I don't think wind power would be a good emergency backup plan.

First, the wind might not be available, there is no certainty that the wind will be there during a storm. So reliability is not there.

Second, wind power generation on Mars should be about three times heavier than the equivalent solar power.  So it will be cheaper to install extra solar power from Earth and use it to run extra Sabatier and electrolytic generators.  You can then store the excess methane and oxygen to run in a generator and use the waste heat from the generator to heat the settlement.  And have 100% reliability.

As far as I know there are no existing generators that run directly off methane and oxygen (without the 80% nitrogen). So that might be a business opportunity :-)

Title: Re: Power options for a Mars settlement
Post by: aero on 10/28/2021 09:05 pm
There are methane fuel cell. Don't recall much about them, it was 20 years ago. Do recall that a waste product was powdered carbon.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 10/28/2021 10:00 pm
I don't think wind power would be a good emergency backup plan.

First, the wind might not be available, there is no certainty that the wind will be there during a storm. So reliability is not there.

Second, wind power generation on Mars should be about three times heavier than the equivalent solar power.  So it will be cheaper to install extra solar power from Earth and use it to run extra Sabatier and electrolytic generators.  You can then store the excess methane and oxygen to run in a generator and use the waste heat from the generator to heat the settlement.  And have 100% reliability.

As far as I know there are no existing generators that run directly off methane and oxygen (without the 80% nitrogen). So that might be a business opportunity :-)
I doubt any have been built but if a turbopump (not FFSC type) can run  on CH4+O2, it looks doable. Worst case, CO2 might be a workable stand in. Water injection might even have some advantages and can be condensed out for reuse.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 10/29/2021 01:40 am
There are methane fuel cell. Don't recall much about them, it was 20 years ago. Do recall that a waste product was powdered carbon.

Poisoning of the catalyst would likely not be an issue with synthetic methane and elevated operating temperature might be in the plus column on Mars  ;)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/29/2021 12:24 pm
There are methane fuel cell. Don't recall much about them, it was 20 years ago. Do recall that a waste product was powdered carbon.

Poisoning of the catalyst would likely not be an issue with synthetic methane and elevated operating temperature might be in the plus column on Mars  ;)
Guess it will be a competition between fuel cells and gas turbines.  The hydrogen(?) and methane productions already depend on catalysts, so I expect contamination will be an issue throughout the production chain. Wonder what will be the contamination level of the source water?  Membrane separation right from the start?  Going to need a lot of water, or perhaps distillation would work, and at -5°C might not need all that much energy, direct from ice to steam and condensed? 

Recuperating the hot steam from the exhaust might be useful, if the heat exchanger isn't too large, recuperating the hot CO2 might be counterproductive, as there already is plenty of cold CO2 about?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/29/2021 12:42 pm
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 10/30/2021 08:56 am
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.
The Sabatier reaction is exothermic.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 10/30/2021 10:46 am
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.
The Sabatier reaction is exothermic.
Which is why energy is lost...
Title: Re: Power options for a Mars settlement
Post by: Welsh Dragon on 10/30/2021 11:16 am
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.
The Sabatier reaction is exothermic.
Which is why energy is lost...
No. You're thinking endothermic. Exothermic reactions produce energy.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 10/30/2021 11:47 am
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.
The Sabatier reaction is exothermic.
Which is why energy is lost...
No. You're thinking endothermic. Exothermic reactions produce energy.
You start with hydrogen and carbon dioxide and get methane, water and energy. Therefore the methane contains less stored energy than the original hydrogen even if all the conversions are 100% efficient.

Numbers: 1 kg of H2 @ 142  MJ => 2 kg CH4 @ 111 MJ, i.e. a loss of 22%.
Title: Re: Power options for a Mars settlement
Post by: Welsh Dragon on 10/30/2021 01:46 pm
You need to do some reading on exo vs endothermic reactions. You say it yourself. It releases energy.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/30/2021 02:06 pm
You need to do some reading on exo vs endothermic reactions. You say it yourself. It releases energy.

Eribo is correct overall, and you specifically.  The Sabatier on its own gives out energy (is exothermic) but as it is fed by the electrolysis, that requires a huge energy input, the pair of reactions loses energy overall.  As hydrogen and oxygen are not available on their own on Mars, the complete reaction is the reaction pair, electrolysis+ Sabatier, that loses thermal energy.  The overall system is the system of interest, from the point of view of power generation of the Martian settlement.

In other words 1 J of solar or nuclear energy transformed into methane gives 0,78 J available in the methane and oxygen and 0,22 J as heat, in a perfect reaction.  The actual energy available will be lower due to inefficiencies.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 10/30/2021 02:41 pm
You need to do some reading on exo vs endothermic reactions. You say it yourself. It releases energy.
An exothermic reaction gives out thermal energy, which means the byproducts now have less energy (because the heat is not part of them)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 10/30/2021 03:05 pm
And so going back to the initial question is the gain from easier storage on Mars worth the loss of potential energy, in the case of the hydrogen-oxygen par vs methane to oxygen pair, when used for emergency power generation requiring long term storage?
The choice has been made for propulsion in SpaceX' case,  but what about energy storage?

Lots of interesting information here:
https://www.frontiersin.org/articles/10.3389/fmech.2020.00021/full#T1
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 10/30/2021 04:42 pm
You need to do some reading on exo vs endothermic reactions. You say it yourself. It releases energy.

Eribo is correct overall, and you specifically.  The Sabatier on its own gives out energy (is exothermic) but as it is fed by the electrolysis, that requires a huge energy input, the pair of reactions loses energy overall.  As hydrogen and oxygen are not available on their own on Mars, the complete reaction is the reaction pair, electrolysis+ Sabatier, that loses thermal energy.  The overall system is the system of interest, from the point of view of power generation of the Martian settlement.

In other words 1 J of solar or nuclear energy transformed into methane gives 0,78 J available in the methane and oxygen and 0,22 J as heat, in a perfect reaction.  The actual energy available will be lower due to inefficiencies.
Yes, but the system as a whole must be oriented toward production and long-term storage of methane and oxygen for use as propellant, so it will already be optimized for that. My guess is that using this resource as needed for second-level electrical backup will be cheaper than adding a system that must store a large amount of hydrogen. At scale, hydrogen storage is a lot harder than methane storage. Spend the capital on expanding your solar, battery, and methane/oxygen storage. That gives you more methane/oxygen production in the first place and less need to use it to produce electricity (fewer hours/year of empty battery) I don't know what the electrcity==>gasses==>electricity  round-trip efficiency will be, but it will be good enough.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 10/30/2021 07:21 pm
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.

Hydrogen compressors aren't cheap, require electricity, and are mechanical components that will break down sooner or later.  Then there is where hydrogen will be stored to consider.  If you want to store hydrogen I suggest considering these (https://www.hydrogencomponents.com/hydride.html).  Discharge is endothermic so they don't pair well with fuel cells but at one point Rouch Racing was developing a hydrogen fueled ICE for ULA's ACES.  The same engine should work for a generator.
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 11/01/2021 03:06 am
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.

Hydrogen compressors aren't cheap, require electricity, and are mechanical components that will break down sooner or later.  Then there is where hydrogen will be stored to consider.  If you want to store hydrogen I suggest considering these (https://www.hydrogencomponents.com/hydride.html).  Discharge is endothermic so they don't pair well with fuel cells but at one point Rouch Racing was developing a hydrogen fueled ICE for ULA's ACES.  The same engine should work for a generator.

Ah yes, the inline 4 cylinder Ford engine derivative intended for ACES. The original engineers would probably be very surprised by that evolution.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/01/2021 03:37 am
Yeah, that works good for seasonal/rare storage for like sand storms and the like. And you'll likely have plenty of hydrogen and methane and oxygen stored as a byproduct of rocket propellant production anyway. BUT for daily cycling it's WAY too round-trip inefficient, IMHO.

The only exception I see is if you're able to use geologic storage or ISRU steel tanks storage for the hydrogen and oxygen, in which case you get a big mass advantage in which case it might be worth it.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/01/2021 08:26 am
Yeah, that works good for seasonal/rare storage for like sand storms and the like. And you'll likely have plenty of hydrogen and methane and oxygen stored as a byproduct of rocket propellant production anyway. BUT for daily cycling it's WAY too round-trip inefficient, IMHO.

The only exception I see is if you're able to use geologic storage or ISRU steel tanks storage for the hydrogen and oxygen, in which case you get a big mass advantage in which case it might be worth it.

Given that the problem that lead me to discover metal hydride hydrogen storage was figuring out how to deal with partially cloudy terrestrial conditions forgive me for responding with a Dr Evil-style maniacal laugh.

The reason to use metal hydride hydrogen storage is that as long at there is a heat source available to power discharge, something that is already available when paired with a Sabatier reactor or the RR ICE I mentioned, is that the metal hydride storage can be engineered to provide a pressure regulated hydrogen output that can be fueled nearly directly off of an electrolysis stack with no need for a hydrogen compressor or other fiddly components.

With the chemical energy storage technology already in hand long term storage is a matter of how much energy needs to be stored.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/01/2021 03:41 pm
Might it make sense to use compressed hydrogen instead of methane for the energy storage part?  Is the energy required to compress hydrogen + the hydrogen losses + the larger tanks > larger than the energy lost in producing methane through Sabatier?  Sabatier uses compressed hydrogen anyway in its process.

Would simplify the fuel cells at least, no need to invent methane ones.
This mentions that the catalysts don't last long and it seems like it has nothing to do with methane purity.
https://chem.stark.kent.edu/chemistry/node/2883 (https://chem.stark.kent.edu/chemistry/node/2883)


H2 has a lot of upsides but it leaks so easily it's hard to think of it as a long term backup for anything. If the fuel cells are strictly for backup who cares if the catalyst poisons after 2-3 years of use. That might be 20-30 years elapsed.


ISTM that the only reason to focus on fuel cells is diversity. It'd be a real bummer to depend on batteries only to learn of a design or manufacturing flaw in most of the batteries available on mars - and they're old enough that they're about to become stand ins for Elon's flame thrower. Personally, I like ICE.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/01/2021 04:05 pm
You need to do some reading on exo vs endothermic reactions. You say it yourself. It releases energy.

Eribo is correct overall, and you specifically.  The Sabatier on its own gives out energy (is exothermic) but as it is fed by the electrolysis, that requires a huge energy input, the pair of reactions loses energy overall.  As hydrogen and oxygen are not available on their own on Mars, the complete reaction is the reaction pair, electrolysis+ Sabatier, that loses thermal energy.  The overall system is the system of interest, from the point of view of power generation of the Martian settlement.

In other words 1 J of solar or nuclear energy transformed into methane gives 0,78 J available in the methane and oxygen and 0,22 J as heat, in a perfect reaction.  The actual energy available will be lower due to inefficiencies.
On Mars, waste is no acceptable. You're point is accurate by itself but the entire process needs taken into account. The hotter the feed, the less power required for electrolysis. Heat can be used in the water mining process.


We often counter the 'spend the money to solve earths problems' argument by claiming the spinoffs make life better. Screw the velcro. Living on Mars demands efficiencies that are directly applicable to earth. We need to optimize systems, not the parts. And strengthen our argument in the process.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/01/2021 05:23 pm
You need to do some reading on exo vs endothermic reactions. You say it yourself. It releases energy.

Eribo is correct overall, and you specifically.  The Sabatier on its own gives out energy (is exothermic) but as it is fed by the electrolysis, that requires a huge energy input, the pair of reactions loses energy overall.  As hydrogen and oxygen are not available on their own on Mars, the complete reaction is the reaction pair, electrolysis+ Sabatier, that loses thermal energy.  The overall system is the system of interest, from the point of view of power generation of the Martian settlement.

In other words 1 J of solar or nuclear energy transformed into methane gives 0,78 J available in the methane and oxygen and 0,22 J as heat, in a perfect reaction.  The actual energy available will be lower due to inefficiencies.
On Mars, waste is no acceptable. You're point is accurate by itself but the entire process needs taken into account. The hotter the feed, the less power required for electrolysis. Heat can be used in the water mining process.


We often counter the 'spend the money to solve earths problems' argument by claiming the spinoffs make life better. Screw the velcro. Living on Mars demands efficiencies that are directly applicable to earth. We need to optimize systems, not the parts. And strengthen our argument in the process.
The heat from the Sabatier is already used on Earth to preheat the hydrogen to improve the electrolysis.  This is needed as much as on Mars because on Earth the natural gas already available for cheap.  so different reason same result, an optimized electrolysis process.  Mars can also use lower temperature heat to melt feed water, and that is not useful on Earth.

But there are economical limits to heat recovery even on Mars.  For example, the habitats should be well insulated to reduce heat loss, but the more they are insulated the less they can use waste heat, as the heat generated inside the habitats starts to need to be evacuated as well.  There is just so much water that needs melting; eventually there will be heat rejection to the Martian environment.

Another example, it will probably be more cost effective to use atmospheric CO2 to feed the fuel process line than to use CO2 generated in combustion engines or turbines. So that CO2 may end up vented.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/01/2021 05:40 pm
Yeah, that works good for seasonal/rare storage for like sand storms and the like. And you'll likely have plenty of hydrogen and methane and oxygen stored as a byproduct of rocket propellant production anyway. BUT for daily cycling it's WAY too round-trip inefficient, IMHO.

The only exception I see is if you're able to use geologic storage or ISRU steel tanks storage for the hydrogen and oxygen, in which case you get a big mass advantage in which case it might be worth it.

Given that the problem that lead me to discover metal hydride hydrogen storage was figuring out how to deal with partially cloudy terrestrial conditions forgive me for responding with a Dr Evil-style maniacal laugh.

The reason to use metal hydride hydrogen storage is that as long at there is a heat source available to power discharge, something that is already available when paired with a Sabatier reactor or the RR ICE I mentioned, is that the metal hydride storage can be engineered to provide a pressure regulated hydrogen output that can be fueled nearly directly off of an electrolysis stack with no need for a hydrogen compressor or other fiddly components.

With the chemical energy storage technology already in hand long term storage is a matter of how much energy needs to be stored.
A couple quick numbers from [size=78%]https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides (https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides)[/size]


A cylinder that holds 822l of hydrogen measures 117mm x 206mm and weighs 5.5kg. It doesn't mention how much of the weight is tank and how much is metal hydride. There is mention that tank pressure is only a few bar at room temp and stainless can be used for the tanks. Feed rate is temperature dependent as is recharge rate.


The size is right but I'm not sure how the mass (plus fuel cell) racks up against a battery or an ICE system for various capacities. The BL-740 unit spec'd above was spec'd with an iron and titanium bed. ISTM Mars is iron rich but titanium poor.


It would be great if the stuff can be made on mars and if impurities only affect output quantity, not quality. There should be a lot of SS available for stainless from no return ships and those ships can be spec'd with some structural members made of titanium for salvage. Hmm, that makes dry mass tricky to calculate.


Mr. Peterson, you have me half convinced.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/01/2021 05:51 pm
Extremely unlikely to be competitive on Mars if it isn’t on Earth.


Metal hydrides are a quite expensive method of storing hydrogen, and you need high purity metals to make them. The safety advantages just don’t matter much on Mars (since the atmosphere doesn’t have enough oxygen to support combustion anyway), and the mass penalty is big.


You still have the low round trip efficiency problem of hydrogen. And you STILL have to store oxygen.


It’s clever, I admit. I’ve thought about it for use for camping fuel. BUT not any better than conventional storage for Mars.



Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/01/2021 06:30 pm
You need to do some reading on exo vs endothermic reactions. You say it yourself. It releases energy.

Eribo is correct overall, and you specifically.  The Sabatier on its own gives out energy (is exothermic) but as it is fed by the electrolysis, that requires a huge energy input, the pair of reactions loses energy overall.  As hydrogen and oxygen are not available on their own on Mars, the complete reaction is the reaction pair, electrolysis+ Sabatier, that loses thermal energy.  The overall system is the system of interest, from the point of view of power generation of the Martian settlement.

In other words 1 J of solar or nuclear energy transformed into methane gives 0,78 J available in the methane and oxygen and 0,22 J as heat, in a perfect reaction.  The actual energy available will be lower due to inefficiencies.
On Mars, waste is no acceptable. You're point is accurate by itself but the entire process needs taken into account. The hotter the feed, the less power required for electrolysis. Heat can be used in the water mining process.


We often counter the 'spend the money to solve earths problems' argument by claiming the spinoffs make life better. Screw the velcro. Living on Mars demands efficiencies that are directly applicable to earth. We need to optimize systems, not the parts. And strengthen our argument in the process.
The heat from the Sabatier is already used on Earth to preheat the hydrogen to improve the electrolysis.  This is needed as much as on Mars because on Earth the natural gas already available for cheap.  so different reason same result, an optimized electrolysis process.  Mars can also use lower temperature heat to melt feed water, and that is not useful on Earth.

But there are economical limits to heat recovery even on Mars.  For example, the habitats should be well insulated to reduce heat loss, but the more they are insulated the less they can use waste heat, as the heat generated inside the habitats starts to need to be evacuated as well.  There is just so much water that needs melting; eventually there will be heat rejection to the Martian environment.

Another example, it will probably be more cost effective to use atmospheric CO2 to feed the fuel process line than to use CO2 generated in combustion engines or turbines. So that CO2 may end up vented.
I'm just having a crabby day.


Dumping CO2 on Mars is like dumping gaseous N2 on earth. Virtually no impact and it takes few resources to gather more if you want it later. Dumping heat on mars? And some people talk like that's a bad thing.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/01/2021 11:13 pm
A couple quick numbers from [size=78%]https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides (https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides)[/size]


A cylinder that holds 822l of hydrogen measures 117mm x 206mm and weighs 5.5kg. It doesn't mention how much of the weight is tank and how much is metal hydride. There is mention that tank pressure is only a few bar at room temp and stainless can be used for the tanks. Feed rate is temperature dependent as is recharge rate.

For Martian applications we'd want to design larger containers fit for our needs.  Pressure can be upped to at least tens of bar by using better tanks.  For a rough idea of the ratio of tank to metal hydride mass you can compare the different size containers Fuel Cell Store sells.  If you want exact figures you can give Hydrogen Components Inc a call. 

Quote
The size is right but I'm not sure how the mass (plus fuel cell) racks up against a battery or an ICE system for various capacities. The BL-740 unit spec'd above was spec'd with an iron and titanium bed. ISTM Mars is iron rich but titanium poor.

A Tesla P100D battery stores 100 kWh and has a mass of 625 kg.  If we're storing energy so we can run a Sabatier reactor overnight 100 kWh will produce ~2 kg of hydrogen, or ~22,400 liters.  Using the 822 l 5.5 kg containers you mentioned above 150 kg is needed to store 2 kg of hydrogen.  In reality we would want to design larger containers sized for our needs to avoid dealing with a plumbing nightmare. Tank mass scales less quickly than volume so the 150 kg figure is high.

The reason I chose to do the above calculation is because Sabatier reactors are more efficient and catalysts degrade far more slowly if the are run continuously.  Therefore it makes sense to design storage into a Martian propellant plant so that it can run overnight.  Since metal hydrides are far more mass efficient than batteries it is my opinion is makes sense to use metal hydrides instead of batteries.  Assuming a production rate of 1200 tonnes of propellant per synod and no throttling the propellant plant will need ~1 million liters of hydrogen storage(~7 tonnes if we are using the 822 l 5.5 kg containers).  These propellant plant containers can be used to store hydrogen for use in fuel cells or an ICE during a dust storm if desired.  In summation what we actually care about is mass of our fuel cells or ICE.

An ICE pairs better with metal hydride hydrogen storage because heat generated by the ICE can be used to discharge the hydrogen storage.  If we use a fuel cell we need to use some of the electricity to generate the heat needed for discharge.

Quote
It would be great if the stuff can be made on mars and if impurities only affect output quantity, not quality. There should be a lot of SS available for stainless from no return ships and those ships can be spec'd with some structural members made of titanium for salvage. Hmm, that makes dry mass tricky to calculate.

A wide variety of metals can be used.  One option that can be made on Mars using existing well-understood technology is nickel purified via the Mond process.  Nickel is also an acceptable Sabatier reactor catalyst.   

Quote
Mr. Peterson, you have me half convinced.

With any luck you'll be fully convinced after reading this.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/01/2021 11:35 pm
I'm not sure metal hydrides make sense for hydrogen storage, but the real issue is electrolysis because I agree you might as well run the Sabatier reactor 24/7 and I don't think hydrogen storage (whichever method you use) is a major problem if you're already needing to use hydrogen. If electrolysis cells are heavy and expensive (they kind of are), then it may make sense to do electrolysis 24/7 as well (or nearly so), in which case you'd still want batteries.

Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/02/2021 04:31 am
I'm not sure metal hydrides make sense for hydrogen storage, but the real issue is electrolysis because I agree you might as well run the Sabatier reactor 24/7 and I don't think hydrogen storage (whichever method you use) is a major problem if you're already needing to use hydrogen. If electrolysis cells are heavy and expensive (they kind of are), then it may make sense to do electrolysis 24/7 as well (or nearly so), in which case you'd still want batteries.

One problem with running electrolysis 24:37 per sol is the extra battery mass.  Continuing with the figures from my previous post, 7 tonnes * 625/150 = 29 tonnes, a difference of 22 tonnes.  This doesn't account for the power required to liquefy oxygen, something we don't need to store power for if we only run electrolysis during the day.

The bigger problem is that it seems you are under the impression that metal hydrides are only for storage.  Metal hydrides also provide pressure regulation and discharge can be powered by heat generated by the Sabatier reactor.  A hydrogen compressor and associated other bits are a different way to provide pressure regulation but those components aren't massless and the compressor is going to require even more stored electrical power.  I wish I could give you a mass estimate for this alternative but it has been years since I last tried to find a hydrogen compressor I can afford and I've since forgotten most of the details.  I can say you aren't going to find a free lunch here.
Title: Re: Power options for a Mars settlement
Post by: jdon759 on 11/02/2021 04:46 am
Forgive me if I've missed something earlier in the thread, but why so much discussion about how to make solar power work during dust storms and the night when you could use nuclear power?  Nuclear is (arguably) a better option on Earth; it will be 4x better again at Mars' distance, right?  Given there is currently a lot of research into space-rated nuclear power; to me, it looks as though only the most optimistic timelines for getting to Mars would need a temporary solar power plant before suitable nuclear options become available.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/02/2021 07:58 am
Forgive me if I've missed something earlier in the thread, but why so much discussion about how to make solar power work during dust storms and the night when you could use nuclear power?  Nuclear is (arguably) a better option on Earth; it will be 4x better again at Mars' distance, right?  Given there is currently a lot of research into space-rated nuclear power; to me, it looks as though only the most optimistic timelines for getting to Mars would need a temporary solar power plant before suitable nuclear options become available.
Yes nuclear is in some ways very compelling, but it suffers from a number of its own serious issues such as readiness to fly and political issues with flying it. As well as issues around some of the fuels that might be used and their availability. But I see no reason why we shouldn't revisit the option (I'm sure it was covered upthread as solar has been). It would be useful to have an overview of what was actually available and how practical it would be on Mars and when it might be ready.

Solar is less efficient on Mars due to the increased distance from the Sun, but not quite as much as might be predicted due to the virtual lack of clouds on Mars.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/02/2021 12:48 pm
I'm not sure metal hydrides make sense for hydrogen storage, but the real issue is electrolysis because I agree you might as well run the Sabatier reactor 24/7 and I don't think hydrogen storage (whichever method you use) is a major problem if you're already needing to use hydrogen. If electrolysis cells are heavy and expensive (they kind of are), then it may make sense to do electrolysis 24/7 as well (or nearly so), in which case you'd still want batteries.
For continuous operations of the Sabatier you can either do twice as much electrolysis during the day and store the hydrogen for use during the night or do electrolysis continuously using batteries for the night and have less hydrogen storage required, but more batteries.
If you do not do electrolysis during the night then you cannot use the Sabatier heat to preheat the hydrogen, and during the day there will be less heat available so the electrolysis might be less efficient.  And during the night you might have to dump the heat rather than re-use it.
I did some work earlier in this thread or on a similar one and came up with the joined illustration:
Although I am no longer as certain of my numbers (wisdom and humility seems to come with time!) perhaps it can help with the discussion.  there is a similar diagram using metal hydrides rather than tanks, at the time I was unable to choose, and it seems to still be the case.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/02/2021 12:53 pm
Forgive me if I've missed something earlier in the thread, but why so much discussion about how to make solar power work during dust storms and the night when you could use nuclear power?  Nuclear is (arguably) a better option on Earth; it will be 4x better again at Mars' distance, right?  Given there is currently a lot of research into space-rated nuclear power; to me, it looks as though only the most optimistic timelines for getting to Mars would need a temporary solar power plant before suitable nuclear options become available.
I expect nuclear on Mars will follow nuclear on Earth.  If it regains momentum on Earth it will be used on Mars; if not then there will be too small a market to develop it.  Nuclear in a sense is a solved problem on Mars.  If it works and can be made available then there are few energy limitations.  Solar is more fussy to run, so it requires more detailed analysis of the power options and the demand variations. 
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/02/2021 01:59 pm
The infrastructure "critical mass", if you will, for nuclear power to produce the radiation tolerant materials for reactor construction, mine, refine and then eventually reprocess the fuel etc will be waaaaay beyond the industrial base on Mars for a long time. That leaves importing form Earth, which might be OK for start up and emergency power in the nearish term but does not strike me as viable long term. I believe there is known to be Thorium on Mars so maybe, long term,  something like a molten salt core Thorium breeder with online reprocessing (which avoids shutdown to refuel) might be in the cards for Mars domestic build. However, while it has been discussed as a safer design which minimizes actinite waste literally since the dawn of nuclear power nothing above research scale has ever been built and operated. Keep an eye on India and China for Thorium research.

In the mean time I expect solar will be king of power production on Mars for initial construction and domestic production.

Edit - In particular low cost thin film perovskite cells, not silicon, given the rate of research progress on them over the past few years
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/02/2021 02:16 pm
The graphic with the metallic storage.  don't remember why it passed from 150 kg to 20 kg of hydrogen.  For the same mass the halides would be heavier.  Would need to check again the outlet pressure and temp of the hydrogen, and the operational pressure of the Sabatier.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/02/2021 02:22 pm
Thorium abundance seems about six times lower than on Earth.  However, this does not means that there were no concentration mechanisms that existed in the past to create useful deposits, either of Thorium or Uranium.  Will need to wait for exploration for answers.  As the concentrations mechanisms for these metals are very similar to those for other more common metals, if there are no deposits of Thorium or Uranium, a Martian settlement may have difficulty finding ores.
We really need a Martian geologist on site!
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/02/2021 02:31 pm
Perovskite cells will require nitrogen and lead, or tin, perhaps germanium.  May be difficult to source locally, but if we only ship these minerals from Earth and all substrate and structure comes from Mars local production may start fairly soon.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/02/2021 02:41 pm
Perovskite cells will require nitrogen and lead, or tin, perhaps germanium.  May be difficult to source locally, but if we only ship these minerals from Earth and all substrate and structure comes from Mars local production may start fairly soon.

Nitrogen should be a minor product from Martian air processing. Lots of research on alternatives to Lead for toxicity reasons on Earth. Like the Thorium/Uranium question it probably depends on what the geologists find in usable quantities on Mars.

Edit - The question becomes, what is the best cell possible with the materials available on Mars, for use on Mars, not the most efficient possible on Earth. Since the atmosphere, temperature operating range, illumination and radiation environments are different any way the "best" solution is probably different too.
Title: Re: Power options for a Mars settlement
Post by: butters on 11/02/2021 03:20 pm
Forgive me if I've missed something earlier in the thread, but why so much discussion about how to make solar power work during dust storms and the night when you could use nuclear power?  Nuclear is (arguably) a better option on Earth; it will be 4x better again at Mars' distance, right?  Given there is currently a lot of research into space-rated nuclear power; to me, it looks as though only the most optimistic timelines for getting to Mars would need a temporary solar power plant before suitable nuclear options become available.
I expect nuclear on Mars will follow nuclear on Earth.  If it regains momentum on Earth it will be used on Mars; if not then there will be too small a market to develop it.  Nuclear in a sense is a solved problem on Mars.  If it works and can be made available then there are few energy limitations.  Solar is more fussy to run, so it requires more detailed analysis of the power options and the demand variations.
I disagree, because the design considerations for off-world reactors are very different, and the regulatory environment is very different from the commercial power reactor industry if it's a NASA program like Kilopower. A resurgence in light water reactor deployments on Earth does nothing for Mars. The mass of those reactor vessels with 8-inch thick steel, the enormous quantity of water, the periodic downtime, the refueling robotics and spent fuel pools... This may be how we do nuclear power on Earth, but it's not appropriate for Mars. If anything, the direction of Gen III+ reactor development is toward greater dependence on Earth gravity for passive convective cooling in contingencies.

Off-world reactors are going to evolve under their own design constraints, and I believe it's more likely that the development of off-world reactors might influence the future of nuclear power on Earth more than the other way around. The commercial power reactor industry was steered along a dead-end path trying to mitigate the problems of adapting Alvin's Weinberg's naval LWR concept from HEU to LEU due to proliferation concerns. NASA programs for off-world reactors may be the best way to achieve NRC approval for anything other than LEU LWRs, driving the legitimacy and technology readiness levels of different approaches that may be more adaptable to terrestrial applications than contemporary reactors are to Mars applications.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/02/2021 03:38 pm
Since it took me a second to parse  ::)

LWR = Light Water Reactor (vs heavy/deuterium)
HEU = Highly Enriched Uranium (235 vs 238)
Proliferation = Plutonium Waste (Potential bombs for undesirable owners)
Title: Re: Power options for a Mars settlement
Post by: magicsound on 11/02/2021 03:48 pm
Just a reminder, there's a relevant active research and development program at NASA that might have been previously mentioned here:
"NASA’s fission surface power project expands on the efforts of the agency’s Kilopower project, which ended in 2018. Currently, NASA is working with the Department of Energy (DOE) and industry to design a 10-kilowatt fission power system for the Moon. A future lunar demonstration will pave the way for sustainable operations and even base camps on the Moon and Mars."

https://www.nasa.gov/mission_pages/tdm/fission-surface-power/index.html

Small scale fusion-based power is also being explored, with some recent reports of progress:

https://www1.grc.nasa.gov/space/science/lattice-confinement-fusion/
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/02/2021 04:18 pm
Forgive me if I've missed something earlier in the thread, but why so much discussion about how to make solar power work during dust storms and the night when you could use nuclear power?  Nuclear is (arguably) a better option on Earth; it will be 4x better again at Mars' distance, right?  Given there is currently a lot of research into space-rated nuclear power; to me, it looks as though only the most optimistic timelines for getting to Mars would need a temporary solar power plant before suitable nuclear options become available.
I expect nuclear on Mars will follow nuclear on Earth.  If it regains momentum on Earth it will be used on Mars; if not then there will be too small a market to develop it.  Nuclear in a sense is a solved problem on Mars.  If it works and can be made available then there are few energy limitations.  Solar is more fussy to run, so it requires more detailed analysis of the power options and the demand variations.
I disagree, because the design considerations for off-world reactors are very different, and the regulatory environment is very different from the commercial power reactor industry if it's a NASA program like Kilopower. A resurgence in light water reactor deployments on Earth does nothing for Mars. The mass of those reactor vessels with 8-inch thick steel, the enormous quantity of water, the periodic downtime, the refueling robotics and spent fuel pools... This may be how we do nuclear power on Earth, but it's not appropriate for Mars. If anything, the direction of Gen III+ reactor development is toward greater dependence on Earth gravity for passive convective cooling in contingencies.

Off-world reactors are going to evolve under their own design constraints, and I believe it's more likely that the development of off-world reactors might influence the future of nuclear power on Earth more than the other way around. The commercial power reactor industry was steered along a dead-end path trying to mitigate the problems of adapting Alvin's Weinberg's naval LWR concept from HEU to LEU due to proliferation concerns. NASA programs for off-world reactors may be the best way to achieve NRC approval for anything other than LEU LWRs, driving the legitimacy and technology readiness levels of different approaches that may be more adaptable to terrestrial applications than contemporary reactors are to Mars applications.
The potential market for nuclear reactors and solar panels on Earth is 15 to 20 000 GW.  At a minimum 9 000 GW of generation is required to replace fossil fuels.  The market on Mars may eventually be 1 GW, in quite a few years.
There is no demand for nuclear reactors on Mars.  I think the only realistic Mars settlement path goes through SpaceX and they seem to have decided to go for Solar.  I believe that to get a demand for nuclear on Mars one would need to prove that solar cannot do the job.  And that doesn't seem to be the case, as far as I know.  I think everyone agrees that nuclear fission would be simpler.  Nuclear fusion would be perfect.  But if solar can do the job, why not solar?
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/02/2021 06:17 pm
The graphic with the metallic storage.  don't remember why it passed from 150 kg to 20 kg of hydrogen.  For the same mass the halides would be heavier.  Would need to check again the outlet pressure and temp of the hydrogen, and the operational pressure of the Sabatier.

If you remember why the stored hydrogen mass dropped let me know.  I can't see a good reason for the difference.

What I do see is that Myhytec metal hydride containers are heavy.  150 kg of storage using the MHT-Magnum metal hydride option (https://www.mahytec.com/en/products/solid-hydrogen-storage/) would have a mass of 17 tonnes.  This is 62% greater than HCI's BL-740 (https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides/bl-740-metal-hydride) per gram of hydrogen stored.  All else being equal the larger container will be require less mass per kg of hydrogen stored so something obviously isn't equal.  Mahytec does include an integrated heat exchanger which explains part of the difference. I'm not sure if HCI's hydrostatic test pressure is proprietary or not so I'm not going to post this value but I don't see a significant explanation for the difference here.  Mahytec uses aluminum while HCI uses steel.  Perhaps there is a heavy liner that accounts for Mahytec's higher mass.  Otherwise I am at a loss to explain the difference.

As for a compressor and tanks, 150 kg of hydrogen storage using the 60 bar tanks (https://www.mahytec.com/en/compressed-hydrogen-storage/) would have a tank mass of 7.7 tonnes.  As far as I can tell this does not include an integrated heat exchanger so it isn't an apples to apples comparison with the 17 tonnes for metal hydrides from above.  Also not included are the hydrogen compressors and the additional electrical power they require.  If I recall correctly the Areva H2Gen E120 you used as a reference has it's own integral hydrogen compressor with a rated maximum output of 35 bar.  I can see you had a secondary compressor which I'm guessing was used to boost pressure from 35 bar to 60 bar.  Knowing the mass and power budgets of both Areva's compressor and the secondary compressor you used as a reference is also needed to come up with an apples to apples mass budget comparison.  Due to gaseous hydrogen's low density we also need to pay close attention to volume limitations.

Returning to the point I was trying to make last night, I still don't see an argument for running electrolysis off of battery power overnight.  I see you have a figure of 12,600 kWh for electrolysis of 210 kg of hydrogen, or 60 kWh/kg.  This translates into a battery energy storage of 9 MWh to match 150 kg of hydrogen storage.  Using the P100D figure of 625 kg per 100 kWh this translates into a battery mass of 56 tonnes.
Title: Re: Power options for a Mars settlement
Post by: butters on 11/02/2021 06:27 pm
Since it took me a second to parse  ::)

LWR = Light Water Reactor (vs heavy/deuterium)
HEU = Highly Enriched Uranium (235 vs 238)
Proliferation = Plutonium Waste (Potential bombs for undesirable owners)
Sorry. In this context, the proliferation concern is the high-enriched uranium going into the reactor as the initial fuel load. There's not much plutonium produced in HEU-fueled reactors. Plutonium is a product of irradiating the >95% U238 in low-enriched uranium fuel. There's a proliferation vector regardless of whether we have a low-enriched uranium fuel cycle or a high-enriched uranium fuel cycle, but a consensus formed that the proliferation risk of fueling a civilization with essentially weapons-grade uranium is greater than the proliferation risk of extracting weapons-grade plutonium from the irradiated waste of LEU reactors.

The bummer is that, proliferation risks aside, HEU is a vastly better reactor fuel. The reactor can run for 20-30 years, maybe more, on a single fuel load. The reactor vessel can be permanently sealed after fueling, never needing to be opened to remove and replace fuel rods, and buried underground at the end of its life, with very little fissile material remaining in the waste. Long-lived HEU cores typically have much lower power to mass ratios than short-lived LEU cores, so in terrestrial light water reactors, the decay heat after shutdown is low enough that exposure to ambient air is sufficient cooling to prevent melting even in the event of a complete loss of water in the primary loop. Naval light water reactors are extraordinarily safe and simple to operate, and that's because they run on HEU.

Kilopower is important because it's a rare opportunity to actually develop an HEU reactor for non-military applications. Because it's managed by NASA, the authorities trust that the sensitive material will be adequately secured throughout the supply chain. So NASA can have a reactor that runs for decades without refueling. NASA can use metallic fuel instead of ceramic oxide fuel, which means they can use liquid sodium coolant instead of water, which means the reactor vessel doesn't have to be 8 inches thick and the reaction can run on fast neutrons, eliminating the moderator.

None of this currently possible in the private sector in the United States. The innovation has to come from somewhere inside the government that is authorized to use non-standard nuclear fuel specifications. We do not trust some startup backed by Bill Gates to develop a type of reactor that requires a small amount of medium-enriched uranium as part of its initial fuel configuration. NASA could develop a traveling wave reactor. But not Bill Gates. It's not a problem that can be solved with money. It's a policy issue and a trust issue.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/02/2021 06:42 pm
The potential market for nuclear reactors and solar panels on Earth is 15 to 20 000 GW.  At a minimum 9 000 GW of generation is required to replace fossil fuels.  The market on Mars may eventually be 1 GW, in quite a few years.
There is no demand for nuclear reactors on Mars.  I think the only realistic Mars settlement path goes through SpaceX and they seem to have decided to go for Solar.  I believe that to get a demand for nuclear on Mars one would need to prove that solar cannot do the job.  And that doesn't seem to be the case, as far as I know.  I think everyone agrees that nuclear fission would be simpler.  Nuclear fusion would be perfect.  But if solar can do the job, why not solar?

The drive to consider nuclear can be summed up by the phrase "When the sun don't shine", with dissimilar redundancy and high energy density thrown in for bonus points. Solar will almost certainly be the primary generation source though.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/02/2021 07:12 pm
Forgive me if I've missed something earlier in the thread, but why so much discussion about how to make solar power work during dust storms and the night when you could use nuclear power?  Nuclear is (arguably) a better option on Earth; it will be 4x better again at Mars' distance, right?  Given there is currently a lot of research into space-rated nuclear power; to me, it looks as though only the most optimistic timelines for getting to Mars would need a temporary solar power plant before suitable nuclear options become available.
Right now, solar is actually cheaper than nuclear on the Earth. And for the same mass, even with batteries, solar is usually lighter weight plus lasts longer than nuclear.

And the correct figure is 2.3x, not 4x, when comparing Earth to Mars insolation.  Nuclear power plants on Earth dump heat into bodies of liquid water on Earth. MAYBE some dump heat into the air, but it’s rarer. Large liquid bodies of water are a little rarer on Mars (keep in mind this has to run reliably), and the air is far thinner. So typical designs use heavy radiators.

There ARE some ideas for improving the specific power of nuclear on Mars by dumping heat into the atmosphere, but it requires super aggressive forced cooling, almost like a jet engine. Much more complicated.

So no, I wouldn’t say nuclear is much better than solar on Mars, particularly when we’re talking about making propellant, which is easy to pause for a week or two once every year if there’s a particularly bad sandstorm.

(Nuclear is still good and I support it, but from a pure technical point its benefits over solar for space applications is often exaggerated…)
Title: Re: Power options for a Mars settlement
Post by: Genial Precis on 11/02/2021 11:02 pm
Nuclear power on Mars hopefully has the advantage that, in lieu of a water table and in the presence of a fair amount of radiation all the time, the usual freakouts about meltdowns can be put in perspective. The safety theater can go away. Also, no NEPA reviews on Mars, hopefully.

Nuclear power on Mars has the disadvantage common to all heat engines that there are not bodies of water or dense atmosphere to sink heat into, which does a lot to reduce the power density per land area advantage. You could use district heating as a heat sink but that entangles it with the design of everything else. It may still be advantageous, but it's more complicated. So is doing anything on Mars... I dunno.

I agree to the notion that a Mars venture probably cannot sustain its own civilian nuclear power industry. It's too expensive to be the only customer of a whole industry for something like nuclear power.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/02/2021 11:15 pm
Forgive me if I've missed something earlier in the thread, but why so much discussion about how to make solar power work during dust storms and the night when you could use nuclear power?  Nuclear is (arguably) a better option on Earth; it will be 4x better again at Mars' distance, right?  Given there is currently a lot of research into space-rated nuclear power; to me, it looks as though only the most optimistic timelines for getting to Mars would need a temporary solar power plant before suitable nuclear options become available.
I expect nuclear on Mars will follow nuclear on Earth.  If it regains momentum on Earth it will be used on Mars; if not then there will be too small a market to develop it.  Nuclear in a sense is a solved problem on Mars.  If it works and can be made available then there are few energy limitations.  Solar is more fussy to run, so it requires more detailed analysis of the power options and the demand variations.
I disagree, because the design considerations for off-world reactors are very different, and the regulatory environment is very different from the commercial power reactor industry if it's a NASA program like Kilopower. A resurgence in light water reactor deployments on Earth does nothing for Mars. The mass of those reactor vessels with 8-inch thick steel, the enormous quantity of water, the periodic downtime, the refueling robotics and spent fuel pools... This may be how we do nuclear power on Earth, but it's not appropriate for Mars. If anything, the direction of Gen III+ reactor development is toward greater dependence on Earth gravity for passive convective cooling in contingencies.

Off-world reactors are going to evolve under their own design constraints, and I believe it's more likely that the development of off-world reactors might influence the future of nuclear power on Earth more than the other way around. The commercial power reactor industry was steered along a dead-end path trying to mitigate the problems of adapting Alvin's Weinberg's naval LWR concept from HEU to LEU due to proliferation concerns. NASA programs for off-world reactors may be the best way to achieve NRC approval for anything other than LEU LWRs, driving the legitimacy and technology readiness levels of different approaches that may be more adaptable to terrestrial applications than contemporary reactors are to Mars applications.
The potential market for nuclear reactors and solar panels on Earth is 15 to 20 000 GW.  At a minimum 9 000 GW of generation is required to replace fossil fuels.  The market on Mars may eventually be 1 GW, in quite a few years.
There is no demand for nuclear reactors on Mars.  I think the only realistic Mars settlement path goes through SpaceX and they seem to have decided to go for Solar.  I believe that to get a demand for nuclear on Mars one would need to prove that solar cannot do the job.  And that doesn't seem to be the case, as far as I know.  I think everyone agrees that nuclear fission would be simpler.  Nuclear fusion would be perfect.  But if solar can do the job, why not solar?
Oh, I bet if DOE offered up a working space rated kilopower SX would take it in a heart beat. The thing about solar/battery is SX has a good supplier and they know the technology. Solar has a track record on Mars so it's arguably the path of least resistance.


There's a lot to be said for diversification. If NASA hadn't done it for crew capsules, the US would still be buying rides from Russia. Thinking about it, Musk's whole reason for going to Mars could be considered diversification.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/02/2021 11:23 pm
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/02/2021 11:29 pm
Nuclear power on Mars hopefully has the advantage that, in lieu of a water table and in the presence of a fair amount of radiation all the time, the usual freakouts about meltdowns can be put in perspective. The safety theater can go away. Also, no NEPA reviews on Mars, hopefully....
I fear that the Outer Space Treaty's prohibition on "harmful contamination" may apply, here. Arguably, nuclear accidents fit that phrasing better than the remote chance that some astronaut bacteria might grow on Mars.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/02/2021 11:31 pm
The graphic with the metallic storage.  don't remember why it passed from 150 kg to 20 kg of hydrogen.  For the same mass the halides would be heavier.  Would need to check again the outlet pressure and temp of the hydrogen, and the operational pressure of the Sabatier.

If you remember why the stored hydrogen mass dropped let me know.  I can't see a good reason for the difference.

What I do see is that Myhytec metal hydride containers are heavy.  150 kg of storage using the MHT-Magnum metal hydride option (https://www.mahytec.com/en/products/solid-hydrogen-storage/) would have a mass of 17 tonnes.  This is 62% greater than HCI's BL-740 (https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides/bl-740-metal-hydride) per gram of hydrogen stored.  All else being equal the larger container will be require less mass per kg of hydrogen stored so something obviously isn't equal.  Mahytec does include an integrated heat exchanger which explains part of the difference. I'm not sure if HCI's hydrostatic test pressure is proprietary or not so I'm not going to post this value but I don't see a significant explanation for the difference here.  Mahytec uses aluminum while HCI uses steel.  Perhaps there is a heavy liner that accounts for Mahytec's higher mass.  Otherwise I am at a loss to explain the difference.

As for a compressor and tanks, 150 kg of hydrogen storage using the 60 bar tanks (https://www.mahytec.com/en/compressed-hydrogen-storage/) would have a tank mass of 7.7 tonnes.  As far as I can tell this does not include an integrated heat exchanger so it isn't an apples to apples comparison with the 17 tonnes for metal hydrides from above.  Also not included are the hydrogen compressors and the additional electrical power they require.  If I recall correctly the Areva H2Gen E120 you used as a reference has it's own integral hydrogen compressor with a rated maximum output of 35 bar.  I can see you had a secondary compressor which I'm guessing was used to boost pressure from 35 bar to 60 bar.  Knowing the mass and power budgets of both Areva's compressor and the secondary compressor you used as a reference is also needed to come up with an apples to apples mass budget comparison.  Due to gaseous hydrogen's low density we also need to pay close attention to volume limitations.

Returning to the point I was trying to make last night, I still don't see an argument for running electrolysis off of battery power overnight.  I see you have a figure of 12,600 kWh for electrolysis of 210 kg of hydrogen, or 60 kWh/kg.  This translates into a battery energy storage of 9 MWh to match 150 kg of hydrogen storage.  Using the P100D figure of 625 kg per 100 kWh this translates into a battery mass of 56 tonnes.
What sort of mileage would you get using a 9m dia stainless tank designed for 6 bar? The mass should work out as a freebie.  :D
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/02/2021 11:32 pm
Not sure. You'd have to run the hydrogen embrittlement calculation.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/02/2021 11:47 pm
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
Absolutely. A power backup system is intended to get you by until the power comes back on.


So, the question still hangs. What's a reasonable per capita power budget to maintain an early mars base at survival levels? Figure 12-20 crew. I expect there are economies of scale with growth.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/03/2021 12:04 am
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
Absolutely. A power backup system is intended to get you by until the power comes back on.


So, the question still hangs. What's a reasonable per capita power budget to maintain an early mars base at survival levels? Figure 12-20 crew. I expect there are economies of scale with growth.

It really depends. You could in principle operate with no electric power at all. Manually operated valves for the oxygen supply and regenerative CO2 scrubbers operated by manual valves as well. Extremely well-insulated interior (easy to vacuum insulate stuff) kept warm by metabolic heat and thermal mass.

But if you have 500kilowatts average power (about 3MW peak power) during clear skies to make propellant, you'd STILL have tens of kilowatts average power in a dust storm, plus lots of storage as well (depending on if you designed your electrolysis to operate near 24/7 or just during the day). That is enough for contingency base power.

Not saying it's a bad idea to have a backup generator (with waste heat for heating the hab) that can run on some of the ISRU methane and oxygen propellant, though.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/03/2021 12:42 am
What sort of mileage would you get using a 9m dia stainless tank designed for 6 bar? The mass should work out as a freebie.  :D

Robotbeat raises a valid point about hydrogen embrittlement.  Another concern that pops into my head quickly is that valves rated for hydrogen are required.  Handwaving away these concerns a 800 m3 main LOX tank should hold ~430 kg of gaseous hydrogen and a 600 m3 main LCH4 tank should hold ~320 kg.  The header tanks are also an option but these are going only hold on the order of 10 kg each.

I wouldn't call this a freebie.  A Martian propellant plant is going to need somewhere to store LOX and LCH4.  Nitrogen and argon storage is also highly desirable.  If we repurpose one Starship for LOX and LCH4 storage and another for gaseous nitrogen and argon storage we'd need a third so that there is a large enough tank available for gaseous hydrogen.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/03/2021 01:03 am
It might be possible to repurpose the header tanks and maybe COPVs separate from the main tanks if the "storage ships" are decomissioned for flight to allow for storage minor gas components.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/03/2021 01:21 am
It might be possible to repurpose the header tanks and maybe COPVs separate from the main tanks if the "storage ships" are decomissioned for flight to allow for storage minor gas components.

Agreed.  While the header tanks are about an order of magnitude too small for gaseous hydrogen storage there are multiple trace elements in the Martian atmosphere it could be worth collecting.  My opinion is the most immediately valuable is carbon monoxide.  Also available are nitrogen oxide, neon, HDO(Hydrogen-Deuterium-Oxygen), krypton, and xenon.

https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

Title: Re: Power options for a Mars settlement
Post by: Vultur on 11/03/2021 05:22 am
I think that SpaceX will avoid long-term hydrogen storage due to its handling issues etc.

Having some kind of combustion generator to turn already-produced CH4/O2 back to electricity does make sense.

However, if you have enough solar capacity to do life support in a worst-case dust storm it is IMO not at all plausible that something will kill your solar capacity, so dissimilar redundancy may not be important. A solar farm to fuel a bunch of Starships will be large - what is going to destroy it that doesn't also destroy the settlement completely (e.g. large asteroid impact)?

If NASA offers SpaceX a Kilopower reactor without a lot of extra paperwork that might impact schedule they would probably take it. But I don't think it would really be all that valuable except as an experiment. Solar and batteries are being improved with lots of investment now; nuclear is a relatively static technology. Solar+batteries will look a lot better 10-20 years from now than it does now; even working fusion might have trouble winning that trade.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 01:21 pm
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
Absolutely. A power backup system is intended to get you by until the power comes back on.


So, the question still hangs. What's a reasonable per capita power budget to maintain an early mars base at survival levels? Figure 12-20 crew. I expect there are economies of scale with growth.

It really depends. You could in principle operate with no electric power at all. Manually operated valves for the oxygen supply and regenerative CO2 scrubbers operated by manual valves as well. Extremely well-insulated interior (easy to vacuum insulate stuff) kept warm by metabolic heat and thermal mass.

But if you have 500kilowatts average power (about 3MW peak power) during clear skies to make propellant, you'd STILL have tens of kilowatts average power in a dust storm, plus lots of storage as well (depending on if you designed your electrolysis to operate near 24/7 or just during the day). That is enough for contingency base power.

Not saying it's a bad idea to have a backup generator (with waste heat for heating the hab) that can run on some of the ISRU methane and oxygen propellant, though.
What might be a good reference for the solar power available during a dust storm?  The direct vs diffuse issue is a really interesting point and I would love to document is on Marspedia.  As storms are very variable, I wonder what might be the maximum planed length for a period of low solar availability?

BTW the entire settlement will need to be designed for significant solar variability and therefore be significantly overbuilt and probably have large amounts of time when there is much more solar power than needed.  In such a situation, the possibility of interrupting the Sabatier and electrolysis might be a good asset. A thermal battery used for a quick startup might be a good option?
 
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/03/2021 01:51 pm
Carbon monoxide "industrial plant gas" is a low energy fuel that is sometimes an industrial by product that, while not cost effective to pipe elsewhere, is useful when burned in the plant where it was produced and can be used as chemical feed stock. Producing CO and O2 might be a useful sink for excess energy when hydrogen is not available for making methane, ammonia etc. The Boiling point of CO is between N2 and O2 so the capability to liquify it should be a available. Might make a suitable propellant for short haul "taxi" vehicles too, which could reduce demand or at least diversion of hydrogen from higher priority uses. The chemical plant that will be a Mars city will need more than just power and have "interesting" logistics.  :o
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 11/03/2021 02:05 pm
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
Absolutely. A power backup system is intended to get you by until the power comes back on.


So, the question still hangs. What's a reasonable per capita power budget to maintain an early mars base at survival levels? Figure 12-20 crew. I expect there are economies of scale with growth.

It really depends. You could in principle operate with no electric power at all. Manually operated valves for the oxygen supply and regenerative CO2 scrubbers operated by manual valves as well. Extremely well-insulated interior (easy to vacuum insulate stuff) kept warm by metabolic heat and thermal mass.

But if you have 500kilowatts average power (about 3MW peak power) during clear skies to make propellant, you'd STILL have tens of kilowatts average power in a dust storm, plus lots of storage as well (depending on if you designed your electrolysis to operate near 24/7 or just during the day). That is enough for contingency base power.

Not saying it's a bad idea to have a backup generator (with waste heat for heating the hab) that can run on some of the ISRU methane and oxygen propellant, though.
What might be a good reference for the solar power available during a dust storm?  The direct vs diffuse issue is a really interesting point and I would love to document is on Marspedia.  As storms are very variable, I wonder what might be the maximum planed length for a period of low solar availability?

BTW the entire settlement will need to be designed for significant solar variability and therefore be significantly overbuilt and probably have large amounts of time when there is much more solar power than needed.  In such a situation, the possibility of interrupting the Sabatier and electrolysis might be a good asset. A thermal battery used for a quick startup might be a good option?

One of the rovers died from lack of power during a dust storm. I would think that is a real world example of the power available. I saw a rover referenced upthread someplace. Opportunity?

Quote
Seems right. At the darkest conditions ever reported (10.8 tau recorded by Opportunity right before the rover failed) the solar panels were still producing 22 Wh/sol, or about 2.5% of their maximum power (900 Wh/sol).

Note that while the solar power output was at 2.5%, the tau value indicates that the transmitted light was only e-10.8 = 0.002% (a factor of >1000x different). This is because the tau value only measures transmitted light and completely ignores scattered light.
« Last Edit: 2021-10-27, 17:59:15 by Twark_Main »
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 03:07 pm
Here is a map of tau values for various large storms.  What I wonder is, can we find a relationship between the Tau value and the actual solar power available?  How do we go from a tau of 10.8  to 2.5% availability as mentioned in Twark_Main's post?

And what might be the reduction in solar power for a tau of 3 of 4, for example?

Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 11/03/2021 04:04 pm
Carbon monoxide "industrial plant gas" is a low energy fuel that is sometimes an industrial by product that, while not cost effective to pipe elsewhere, is useful when burned in the plant where it was produced and can be used as chemical feed stock. Producing CO and O2 might be a useful sink for excess energy when hydrogen is not available for making methane, ammonia etc. The Boiling point of CO is between N2 and O2 so the capability to liquify it should be a available. Might make a suitable propellant for short haul "taxi" vehicles too, which could reduce demand or at least diversion of hydrogen from higher priority uses. The chemical plant that will be a Mars city will need more than just power and have "interesting" logistics.  :o
During the "gaslight era", prior to the extensive production of natural gas, essentially all gas was "coal gas", which was a mixture of hydrogen and carbon monoxide. The local gasworks remained in use well into the 1950's in many places. So yes, you can use the CO. However, it's dangerous because CO poisoning is a whole lot more deadly than risk of NG explosion. This is why suicide by sticking your head in the oven no longer works.
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 11/03/2021 04:17 pm
Part of the worst case scenarios. 
What if they lose each power type  batteries, solar cells, fuel cells, nuclear, anything they depend on. 
They will create plans for short term, long term and never restore. 
Chances of this kind failure is higher early on when things are new, less redundancy and resilience. 
Title: Re: Power options for a Mars settlement
Post by: ThomasGadd on 11/03/2021 04:27 pm
I think that SpaceX will avoid long-term hydrogen storage due to its handling issues etc.

Having some kind of combustion generator to turn already-produced CH4/O2 back to electricity does make sense.

However, if you have enough solar capacity to do life support in a worst-case dust storm it is IMO not at all plausible that something will kill your solar capacity, so dissimilar redundancy may not be important. A solar farm to fuel a bunch of Starships will be large - what is going to destroy it that doesn't also destroy the settlement completely (e.g. large asteroid impact)?

If NASA offers SpaceX a Kilopower reactor without a lot of extra paperwork that might impact schedule they would probably take it. But I don't think it would really be all that valuable except as an experiment. Solar and batteries are being improved with lots of investment now; nuclear is a relatively static technology. Solar+batteries will look a lot better 10-20 years from now than it does now; even working fusion might have trouble winning that trade.

The Kilopower will be HALEU powered which will help on the regulatory side. 

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 04:55 pm
If there really is 2% of solar power available in the worst possible storm case, that is not an accident but an expected minimum, it might make sense to provide the required extra solar power so that the remaining power is sufficient.  The sun is really reliable.

Then as a second stage of protection, methane storage is clearly safer than hydrogen storage, so that might be the best choice.  The methane and oxygen should be the largest source of energy available for a long time on Mars.  Oxygen is also useful for the habitat atmosphere safety, so a dual purpose. 

In contrast to Earth were the oxygen is readily available, it has to be stored or generated on Mars.  Generated is really energy intensive so stored seems like the best idea.  Removing excess CO2 is possible and not too energy intensive using regenerative media, so that is perhaps part of the minimum calculated load.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 11/03/2021 04:57 pm
Here is a map of tau values for various large storms.  What I wonder is, can we find a relationship between the Tau value and the actual solar power available?  How do we go from a tau of 10.8  to 2.5% availability as mentioned in Twark_Main's post?

And what might be the reduction in solar power for a tau of 3 of 4, for example?
A look at the Opportunity Rover updates at https://mars.nasa.gov/mer/mission/rover-status/opportunity/recent/ provides:

2018 dust storm:
Sol       Wh     tau        dust factor
5093   664   0.562   0.769
5100    652   0.640   0.772
5105    468   1.0
5106    345   2.1
5107    133    >3.0
5111      22      10.8

During the 2007 dust storm it went from ~800 Wh to 280 Wh at a tau of 4.12, with an estimate that 5.0 would result in 150 Wh.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/03/2021 05:44 pm
Carbon monoxide "industrial plant gas" is a low energy fuel that is sometimes an industrial by product that, while not cost effective to pipe elsewhere, is useful when burned in the plant where it was produced and can be used as chemical feed stock. Producing CO and O2 might be a useful sink for excess energy when hydrogen is not available for making methane, ammonia etc. The Boiling point of CO is between N2 and O2 so the capability to liquify it should be a available. Might make a suitable propellant for short haul "taxi" vehicles too, which could reduce demand or at least diversion of hydrogen from higher priority uses. The chemical plant that will be a Mars city will need more than just power and have "interesting" logistics.  :o
During the "gaslight era", prior to the extensive production of natural gas, essentially all gas was "coal gas", which was a mixture of hydrogen and carbon monoxide. The local gasworks remained in use well into the 1950's in many places. So yes, you can use the CO. However, it's dangerous because CO poisoning is a whole lot more deadly than risk of NG explosion. This is why suicide by sticking your head in the oven no longer works.

Sure CO is toxic, but no more than a lot of other industrial feed stock chemicals that will be needed. Colorless and odorless is a bit of a problem but detectors are cheap and effective and I doubt anybody plans to pipe it to space heaters in the habitat  ::)

The question was raised about what to do with excess power when the air is clear for an array sized to provide life support in the worst case dust storm. Storing some of it as chemical energy in multi use feed stocks seems worth looking at. There are probably a number of basic carbon, nitrogen, oxygen etc compounds with potential. CO / O2 was just what came to mind first.
Title: Re: Power options for a Mars settlement
Post by: yakman2020 on 11/03/2021 05:58 pm
So, there were some papers a few years back (2018 I think) noting some geologically (areologically?) significant areas of melt apparently cause by natural nuclear reactions between thorium and probably natural uranium.

Apparently Mars is filthy rich in thorium.

A gas-moderated pebble bed nuclear reactor using local thorium would only require a bit of engineering and a minimum mass (maybe a few kg) of u-232 or other neutron source. In fact, the neutron source could be non-nuclear, such as a stripped ion beam. It doesn't have to be power self-sufficient. Just enough the start the thorium cycle. Once the cycle is started you can turn it off, since the cycle is self sustaining. Further, DoD is funding development of just such a reactor for field base use, so the tech is pretty well understood.

Why would that not be a good idea compared to using rocket fuel?

update: Apparently not such a new idea
https://www.popsci.com/technology/article/2010-08/thorium-reactors-could-wean-world-oil-just-five-years/
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/03/2021 06:09 pm
Given all of the need for power storage, cryogenic gas refrigeration and the need for radiators I wonder if some form of physical solid/liquid/gas phase transition system might be of use to store power using atmospheric CO2? Similar to that being used here:
https://highviewpower.com/technology/ (https://highviewpower.com/technology/)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 06:12 pm
So, there were some papers a few years back (2018 I think) noting some geologically (areologically?) significant areas of melt apparently cause by natural nuclear reactions between thorium and probably natural uranium.

Apparenlty Mars is filthy rich in thorium.

A gas-moderated pebble bed nuclear reactor using local thorium would only require a bit of engineering and a minimum mass (maybe a few kg) of u-232 or other neutron source. In fact, the neutron source could be non-nuclear, such as a stripped ion beam. It doesn't have to be power self-sufficient. Just enough the start the thorium cycle. Once the cycle is started you can turn it off, since the cycle is self sustaining. Further, DoD is funding development of just such a reactor for field base use, so the tech is pretty well understood.

Why would that not be a good idea compared to using rocket fuel?
Do you have a reference for the Thorium values?  Because the data I have is not as positive.
Here is a map of Thorium average concentration as measured form orbit (isotopic radiation measurement)
The average value is lower than 1 ppm, with one northern area near to 1.
On Earth the average value of soil is 6 ppm of thorium and 8 ppm in the crust. https://en.wikipedia.org/wiki/Thorium#Occurrence

That is not conclusive, of course, but not very encouraging.
Thorium is a great idea, however thorium reactor are not an existing product.  Ideas are wonderful and fun, but actual products are useful and you can plan on them.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 06:29 pm
Given all of the need for power storage, cryogenic gas refrigeration and the need for radiators I wonder if some form of physical solid/liquid/gas phase transition system might be of use to store power using atmospheric CO2? Similar to that being used here:
https://highviewpower.com/technology/ (https://highviewpower.com/technology/)
I like the idea.  I wonder id using stored heat might be a way to improve the performance of Sabatier and electrolysis systems that undergo nightly interruptions by making the startup faster and easier.  There was a time when this was seriously looked at for cars, that have (had?) a hard time starting in northern latitudes.
Title: Re: Power options for a Mars settlement
Post by: Barley on 11/03/2021 06:39 pm
The question was raised about what to do with excess power when the air is clear for an array sized to provide life support in the worst case dust storm. Storing some of it as chemical energy in multi use feed stocks seems worth looking at. There are probably a number of basic carbon, nitrogen, oxygen etc compounds with potential. CO / O2 was just what came to mind first.
Where to use intermittent excess power would depend on the mass, efficiency and tolerance to intermittent use of the plant required to generate and store the chemicals.  Is there any reason to believe that intermittently producing CO would be easier than intermittently producing H2 or CH4?
Title: Re: Power options for a Mars settlement
Post by: yakman2020 on 11/03/2021 06:41 pm
So, there were some papers a few years back (2018 I think) noting some geologically (areologically?) significant areas of melt apparently cause by natural nuclear reactions between thorium and probably natural uranium.

Apparenlty Mars is filthy rich in thorium.

A gas-moderated pebble bed nuclear reactor using local thorium would only require a bit of engineering and a minimum mass (maybe a few kg) of u-232 or other neutron source. In fact, the neutron source could be non-nuclear, such as a stripped ion beam. It doesn't have to be power self-sufficient. Just enough the start the thorium cycle. Once the cycle is started you can turn it off, since the cycle is self sustaining. Further, DoD is funding development of just such a reactor for field base use, so the tech is pretty well understood.

Why would that not be a good idea compared to using rocket fuel?
Do you have a reference for the Thorium values?  Because the data I have is not as positive.
Here is a map of Thorium average concentration as measured form orbit (isotopic radiation measurement)
The average value is lower than 1 ppm, with one northern area near to 1.
On Earth the average value of soil is 6 ppm of thorium and 8 ppm in the crust. https://en.wikipedia.org/wiki/Thorium#Occurrence

That is not conclusive, of course, but not very encouraging.
Thorium is a great idea, however thorium reactor are not an existing product.  Ideas are wonderful and fun, but actual products are useful and you can plan on them.

On the map you provided ar numberous areas rich in thorium, well into the red (>1.0ppm).  Here's a reference for mars being thorium rich enough in places to actually react naturally.https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1097.pdf

Regarding the question of whether thorium reactors are new technology,  https://en.wikipedia.org/wiki/Pebble-bed_reactor gives some indication as to thorium cycle's fairly long history.

Of course development work would be required, but I don't think there is any approach to this which would not require extensive development work.   The question is which would require less work, could leverage the most existing technology, and would have the greatest growth potential.

I would argue that a hole in the ground with a container of pebbles (for sure and over simplification but not by that much) which can easily produce 600 MW in all weather would seem interesting. Using a particle beam would skirt the regulatory issues.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/03/2021 06:58 pm
So, there were some papers a few years back (2018 I think) noting some geologically (areologically?) significant areas of melt apparently cause by natural nuclear reactions between thorium and probably natural uranium.

Apparenlty Mars is filthy rich in thorium.

A gas-moderated pebble bed nuclear reactor using local thorium would only require a bit of engineering and a minimum mass (maybe a few kg) of u-232 or other neutron source. In fact, the neutron source could be non-nuclear, such as a stripped ion beam. It doesn't have to be power self-sufficient. Just enough the start the thorium cycle. Once the cycle is started you can turn it off, since the cycle is self sustaining. Further, DoD is funding development of just such a reactor for field base use, so the tech is pretty well understood.

Why would that not be a good idea compared to using rocket fuel?
Do you have a reference for the Thorium values?  Because the data I have is not as positive.
Here is a map of Thorium average concentration as measured form orbit (isotopic radiation measurement)
The average value is lower than 1 ppm, with one northern area near to 1.
On Earth the average value of soil is 6 ppm of thorium and 8 ppm in the crust. https://en.wikipedia.org/wiki/Thorium#Occurrence

That is not conclusive, of course, but not very encouraging.
Thorium is a great idea, however thorium reactor are not an existing product.  Ideas are wonderful and fun, but actual products are useful and you can plan on them.

On the map you provided ar numberous areas rich in thorium, well into the red (>1.0ppm).  Here's a reference for mars being thorium rich enough in places to actually react naturally.https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1097.pdf

Regarding the question of whether thorium reactors are new technology,  https://en.wikipedia.org/wiki/Pebble-bed_reactor gives some indication as to thorium cycle's fairly long history.

Of course development work would be required, but I don't think there is any approach to this which would not require extensive development work.   The question is which would require less work, could leverage the most existing technology, and would have the greatest growth potential.

I would argue that a hole in the ground with a container of pebbles (for sure and over simplification but not by that much) which can easily produce 600 MW in all weather would seem interesting. Using a particle beam would skirt the regulatory issues.

We were discussing reactor types not very far up thread, including Thorium. Unfortunately there is nothing, except possibly for Kilopower, which could be shipped to Mars for a number of synods, piles of money and hand waving not withstanding. Personally I think if Martian colonists build reactors in the fairly far future Thorium would be a likely fuel, for some of the reasons you raise. But not now as lamontagne pointed out, they do no exist as real hardware.

Molten salt storage like used on some big solar concentrator plants to run steam turbines might work for storage over night with some of the advantages of a reactor.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 07:26 pm
So, there were some papers a few years back (2018 I think) noting some geologically (areologically?) significant areas of melt apparently cause by natural nuclear reactions between thorium and probably natural uranium.

Apparenlty Mars is filthy rich in thorium.

A gas-moderated pebble bed nuclear reactor using local thorium would only require a bit of engineering and a minimum mass (maybe a few kg) of u-232 or other neutron source. In fact, the neutron source could be non-nuclear, such as a stripped ion beam. It doesn't have to be power self-sufficient. Just enough the start the thorium cycle. Once the cycle is started you can turn it off, since the cycle is self sustaining. Further, DoD is funding development of just such a reactor for field base use, so the tech is pretty well understood.

Why would that not be a good idea compared to using rocket fuel?
Do you have a reference for the Thorium values?  Because the data I have is not as positive.
Here is a map of Thorium average concentration as measured form orbit (isotopic radiation measurement)
The average value is lower than 1 ppm, with one northern area near to 1.
On Earth the average value of soil is 6 ppm of thorium and 8 ppm in the crust. https://en.wikipedia.org/wiki/Thorium#Occurrence

That is not conclusive, of course, but not very encouraging.
Thorium is a great idea, however thorium reactor are not an existing product.  Ideas are wonderful and fun, but actual products are useful and you can plan on them.

On the map you provided ar numberous areas rich in thorium, well into the red (>1.0ppm).  Here's a reference for mars being thorium rich enough in places to actually react naturally.https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1097.pdf

Regarding the question of whether thorium reactors are new technology,  https://en.wikipedia.org/wiki/Pebble-bed_reactor gives some indication as to thorium cycle's fairly long history.

Of course development work would be required, but I don't think there is any approach to this which would not require extensive development work.   The question is which would require less work, could leverage the most existing technology, and would have the greatest growth potential.

I would argue that a hole in the ground with a container of pebbles (for sure and over simplification but not by that much) which can easily produce 600 MW in all weather would seem interesting. Using a particle beam would skirt the regulatory issues.
Hum, have you read this interesting paper by the same author?
Evidence of massive thermonuclear explo- sions on Mars in the past, The Cydonian
Hypothesis, and Fermis Paradox: new data
It is very, very strange....
https://www.tsijournals.com/articles/evidence-of-massive-thermonuclear-explosions-on-mars-in-the-past-the-cydonian-hypothesis-and-fermis-paradox-new-data.pdf

I don't necessarily object to aliens deploying nuclear weapons to bombard Mars at a very large scale, as proposed by Brandenburg, but I have to wonder where the author finds his superabundance data when the data shows what seems to be to be a lack of Thorium.  But as I am not a geologist, I may be interpreting these things incorrectly.  However, I think including images of the face on Mars as documentary proof in his scientific paper is perhaps not a good idea.

Perhaps you have another source on the Thorium abundance question?





Title: Re: Power options for a Mars settlement
Post by: yakman2020 on 11/03/2021 07:43 pm
https://www.extremetech.com/extreme/328619-project-pele-why-the-dod-is-betting-on-tiny-nuclear-reactors-to-solve-its-power-woes

It appears the reactor designs themselves would be feasibly ported.  I don't understand "hand waving" in this case.

A PELE reactor could be transported or constructed using the DoD design.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 07:47 pm
Oh boy, who is J.E Brandenberg?

Google scholar yields some seemingly normal articles, and then some very strange stuff.

This commentary found in my Google search makes me wonder just how serious/professional he is.  The articles seem logical at first glance, but strange tangents creep in...

https://core.ac.uk/download/pdf/42773562.pdf
 
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/03/2021 07:51 pm
Given all of the need for power storage, cryogenic gas refrigeration and the need for radiators I wonder if some form of physical solid/liquid/gas phase transition system might be of use to store power using atmospheric CO2? Similar to that being used here:
https://highviewpower.com/technology/ (https://highviewpower.com/technology/)
I like the idea.  I wonder id using stored heat might be a way to improve the performance of Sabatier and electrolysis systems that undergo nightly interruptions by making the startup faster and easier.  There was a time when this was seriously looked at for cars, that have (had?) a hard time starting in northern latitudes.

The Sabatier reactor runs at ~350 C.  What type of heat storage will be able to ensure the reactor is up to temperature every morning?

How is it charged?

What does this system mass?
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/03/2021 07:51 pm
https://www.extremetech.com/extreme/328619-project-pele-why-the-dod-is-betting-on-tiny-nuclear-reactors-to-solve-its-power-woes

It appears the reactor designs themselves would be feasibly ported.  I don't understand "hand waving" in this case.

A PELE reactor could be transported or constructed using the DoD design.

Hand waving in this case means assuming or acting like something will definitely work as hypothesized on paper before the inevitable reality based details that have a way of popping up have been dealt with. Plenty of perfectly valid ideas proven in the lab die at the bench or pilot plant scale for practical reasons that were not fully anticipated before hand. Which boils down to too expensive in many cases.
Title: Re: Power options for a Mars settlement
Post by: yakman2020 on 11/03/2021 07:53 pm
https://mars.nasa.gov/odyssey/gallery/latestimages/PIA04257.html

It does appear there are thorium rich areas on mars, regardless of the relative abundance vis earth. In the case of earth, thorium is so abundant a lot of processes produce it as a waste. 

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 07:59 pm
https://mars.nasa.gov/odyssey/gallery/latestimages/PIA04257.html

It does appear there are thorium rich areas on mars, regardless of the relative abundance vis earth. In the case of earth, thorium is so abundant a lot of processes produce it as a waste.
And that is the exact point.  An abundance of 1 ppm will need so much refining and concentration that it is not viable as an energy source.  One million tonnes of rock need to be treated to produce one tonne of nuclear fuel.  That's a huge energetic requirement.  Very high grade uranium ore is 200 000 ppm.  very low grade is 100 ppm.  Treating 100 times more material will probably take more energy than the mine produces.  Relative abundance is the most important thing.  It's the difference between dirt and a mine.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/03/2021 08:03 pm
Given all of the need for power storage, cryogenic gas refrigeration and the need for radiators I wonder if some form of physical solid/liquid/gas phase transition system might be of use to store power using atmospheric CO2? Similar to that being used here:
https://highviewpower.com/technology/ (https://highviewpower.com/technology/)
I like the idea.  I wonder id using stored heat might be a way to improve the performance of Sabatier and electrolysis systems that undergo nightly interruptions by making the startup faster and easier.  There was a time when this was seriously looked at for cars, that have (had?) a hard time starting in northern latitudes.

The Sabatier reactor runs at ~350 C.  What type of heat storage will be able to ensure the reactor is up to temperature every morning?

How is it charged?

What does this system mass?
None, i guess molten aluminum might do the trick.  Would have to be electrically.
Would have to mass way too much. 
Thermal storage ideas almost never work, do they?  It was just an idle notion, now thoroughly shot down :-)
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/03/2021 08:17 pm
https://www.seia.org/initiatives/concentrating-solar-power

Here is a link about solar concentrator plants currently producing power in the US. The technology works but mass to Mars would be horrible unless the thermal storage could be sourced locally.

Hmmm. I wonder what the direct thermal electric efficiency would be with the temperature gradient available on Mars at night :)
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/03/2021 08:19 pm
Carbon monoxide "industrial plant gas" is a low energy fuel that is sometimes an industrial by product that, while not cost effective to pipe elsewhere, is useful when burned in the plant where it was produced and can be used as chemical feed stock. Producing CO and O2 might be a useful sink for excess energy when hydrogen is not available for making methane, ammonia etc. The Boiling point of CO is between N2 and O2 so the capability to liquify it should be a available. Might make a suitable propellant for short haul "taxi" vehicles too, which could reduce demand or at least diversion of hydrogen from higher priority uses. The chemical plant that will be a Mars city will need more than just power and have "interesting" logistics.  :o
During the "gaslight era", prior to the extensive production of natural gas, essentially all gas was "coal gas", which was a mixture of hydrogen and carbon monoxide. The local gasworks remained in use well into the 1950's in many places. So yes, you can use the CO. However, it's dangerous because CO poisoning is a whole lot more deadly than risk of NG explosion. This is why suicide by sticking your head in the oven no longer works.
CO isn’t any worse than ammonia, by the way.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/03/2021 08:39 pm
Given all of the need for power storage, cryogenic gas refrigeration and the need for radiators I wonder if some form of physical solid/liquid/gas phase transition system might be of use to store power using atmospheric CO2? Similar to that being used here:
https://highviewpower.com/technology/ (https://highviewpower.com/technology/)
I like the idea.  I wonder id using stored heat might be a way to improve the performance of Sabatier and electrolysis systems that undergo nightly interruptions by making the startup faster and easier.  There was a time when this was seriously looked at for cars, that have (had?) a hard time starting in northern latitudes.

The Sabatier reactor runs at ~350 C.  What type of heat storage will be able to ensure the reactor is up to temperature every morning?

How is it charged?

What does this system mass?
None, i guess molten aluminum might do the trick.  Would have to be electrically.
Would have to mass way too much. 
Thermal storage ideas almost never work, do they?  It was just an idle notion, now thoroughly shot down :-)
No doubt a lot of thermal storage ideas don't work but these appear to. Highview, is currently constructing a 50MW liquid-air, energy-storage (LAES) facility at Carrington Village, Greater Manchester, in the UK.
https://www.smart-energy.com/industry-sectors/storage/uk-cryogenic-energy-storage-plant-shifts-closer-to-commercial-operation/ (https://www.smart-energy.com/industry-sectors/storage/uk-cryogenic-energy-storage-plant-shifts-closer-to-commercial-operation/)
They have already built some pilot plants https://highviewpower.com/plants/ (https://highviewpower.com/plants/)
I don't know if this approach would be viable on Mars but with only 1% atmospheric pressure it should be a lot easier to provide vacuum insulated pressure vessels.

Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 11/03/2021 08:40 pm
https://mars.nasa.gov/odyssey/gallery/latestimages/PIA04257.html

It does appear there are thorium rich areas on mars, regardless of the relative abundance vis earth. In the case of earth, thorium is so abundant a lot of processes produce it as a waste.
And that is the exact point.  An abundance of 1 ppm will need so much refining and concentration that it is not viable as an energy source.  One million tonnes of rock need to be treated to produce one tonne of nuclear fuel.  That's a huge energetic requirement.  Very high grade uranium ore is 200 000 ppm.  very low grade is 100 ppm.  Treating 100 times more material will probably take more energy than the mine produces.  Relative abundance is the most important thing.  It's the difference between dirt and a mine.
While you raise a valid point in principle, I would caution you about evaluating ore grades from orbital maps.  Those maps may be useful in identifying areas that are prospective for further exploration, but as a tool for identifying actual ore bodies they'll be basically useless.  I would think that an ore body would have to be almost unimaginably massive in order to show up at actual grade on orbital maps such as this.
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 11/03/2021 08:49 pm
Carbon monoxide "industrial plant gas" is a low energy fuel that is sometimes an industrial by product that, while not cost effective to pipe elsewhere, is useful when burned in the plant where it was produced and can be used as chemical feed stock. Producing CO and O2 might be a useful sink for excess energy when hydrogen is not available for making methane, ammonia etc. The Boiling point of CO is between N2 and O2 so the capability to liquify it should be a available. Might make a suitable propellant for short haul "taxi" vehicles too, which could reduce demand or at least diversion of hydrogen from higher priority uses. The chemical plant that will be a Mars city will need more than just power and have "interesting" logistics.  :o
During the "gaslight era", prior to the extensive production of natural gas, essentially all gas was "coal gas", which was a mixture of hydrogen and carbon monoxide. The local gasworks remained in use well into the 1950's in many places. So yes, you can use the CO. However, it's dangerous because CO poisoning is a whole lot more deadly than risk of NG explosion. This is why suicide by sticking your head in the oven no longer works.
CO isn’t any worse than ammonia, by the way.
CO is worse because it is indetectable without instruments.  That's why we have CO alarms in our houses bu not NH3 alarms. But back on topic: any energy storage system is "dangerous" by definition and must therefore be properly engineered for safety. This requirement will affect the costs of different systems differently, and for Mars, the big consideration will be the further tradeoff between local manufacturing versus importation from Earth. An inefficient system produced locally may have a higher absolute output than an efficient imported system.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/03/2021 08:52 pm
https://mars.nasa.gov/odyssey/gallery/latestimages/PIA04257.html

It does appear there are thorium rich areas on mars, regardless of the relative abundance vis earth. In the case of earth, thorium is so abundant a lot of processes produce it as a waste.
And that is the exact point.  An abundance of 1 ppm will need so much refining and concentration that it is not viable as an energy source.  One million tonnes of rock need to be treated to produce one tonne of nuclear fuel.  That's a huge energetic requirement.  Very high grade uranium ore is 200 000 ppm.  very low grade is 100 ppm.  Treating 100 times more material will probably take more energy than the mine produces.  Relative abundance is the most important thing.  It's the difference between dirt and a mine.
While you raise a valid point in principle, I would caution you about evaluating ore grades from orbital maps.  Those maps may be useful in identifying areas that are prospective for further exploration, but as a tool for identifying actual ore bodies they'll be basically useless.  I would think that an ore body would have to be almost unimaginably massive in order to show up at actual grade on orbital maps such as this.
I would have thought that it will always be far easier and cheaper to transport Thorium from Earth rather than build infrastructure for Thorium production on Mars. May be in the very distant future when they are trying to ensure Mars could survive without Earth someone will try to develop a local source, but on the list of things that would be really beneficial to produce locally it must be way down.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/03/2021 09:22 pm
https://mars.nasa.gov/odyssey/gallery/latestimages/PIA04257.html

It does appear there are thorium rich areas on mars, regardless of the relative abundance vis earth. In the case of earth, thorium is so abundant a lot of processes produce it as a waste.
And that is the exact point.  An abundance of 1 ppm will need so much refining and concentration that it is not viable as an energy source.  One million tonnes of rock need to be treated to produce one tonne of nuclear fuel.  That's a huge energetic requirement.  Very high grade uranium ore is 200 000 ppm.  very low grade is 100 ppm.  Treating 100 times more material will probably take more energy than the mine produces.  Relative abundance is the most important thing.  It's the difference between dirt and a mine.
While you raise a valid point in principle, I would caution you about evaluating ore grades from orbital maps.  Those maps may be useful in identifying areas that are prospective for further exploration, but as a tool for identifying actual ore bodies they'll be basically useless.  I would think that an ore body would have to be almost unimaginably massive in order to show up at actual grade on orbital maps such as this.
I would have thought that it will always be far easier and cheaper to transport Thorium from Earth rather than build infrastructure for Thorium production on Mars. May be in the very distant future when they are trying to ensure Mars could survive without Earth someone will try to develop a local source, but on the list of things that would be really beneficial to produce locally it must be way down.

From a practical point of view, Thorium is probable the only possible fuel that could be launched to Mars by the ton on a long term basis since it has only one natural isotope is non fissile and only slightly radioactive. Trying to launch that much Plutonium or enriched Uranium would be a world wide political food fight. Of course until someone builds a working Thorium reactor it is a moot point.
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 11/03/2021 09:36 pm
Given all of the need for power storage, cryogenic gas refrigeration and the need for radiators I wonder if some form of physical solid/liquid/gas phase transition system might be of use to store power using atmospheric CO2? Similar to that being used here:
https://highviewpower.com/technology/ (https://highviewpower.com/technology/)
I like the idea.  I wonder id using stored heat might be a way to improve the performance of Sabatier and electrolysis systems that undergo nightly interruptions by making the startup faster and easier.  There was a time when this was seriously looked at for cars, that have (had?) a hard time starting in northern latitudes.

The Sabatier reactor runs at ~350 C.  What type of heat storage will be able to ensure the reactor is up to temperature every morning?

How is it charged?

What does this system mass?
None, i guess molten aluminum might do the trick.  Would have to be electrically.
Would have to mass way too much. 
Thermal storage ideas almost never work, do they?  It was just an idle notion, now thoroughly shot down :-)
No doubt a lot of thermal storage ideas don't work but these appear to. Highview, is currently constructing a 50MW liquid-air, energy-storage (LAES) facility at Carrington Village, Greater Manchester, in the UK.
https://www.smart-energy.com/industry-sectors/storage/uk-cryogenic-energy-storage-plant-shifts-closer-to-commercial-operation/ (https://www.smart-energy.com/industry-sectors/storage/uk-cryogenic-energy-storage-plant-shifts-closer-to-commercial-operation/)
They have already built some pilot plants https://highviewpower.com/plants/ (https://highviewpower.com/plants/)
I don't know if this approach would be viable on Mars but with only 1% atmospheric pressure it should be a lot easier to provide vacuum insulated pressure vessels.

A potentially useful aspect of liquid air based energy storage is that they typically have an associated thermal energy store to recover heat of compression, which may be useful for industrial heat applications. But with CO2, you run the risk of it going solid at some mars ambient temps when at high pressure, as the liquid phase part of the phase transition chart is rather slim in area. LOx on it's own would work though, but then what do you do with the gaseous oxygen when you generate power via the expansion turbine? You either have to capture in big tanks (where would those come from?) or vent to atmosphere which is wasteful.

Seems like filling empty starship tanks with gravel and pressurized CO2, and using that as a thermal store would be a quick and dirty method. Exhaust from the expansion turbine would be dry ice snow.


Wait, bad idea incoming.

If LOx densification is available, can that be used directly via some sort of liquid pressure power generator? Think a reciprocating piston with a cylinder head heater, heating the LOx just enough to undo the densification (increasing LOx liquid pressure) but still remain liquid LOx.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 11/03/2021 09:54 pm
SpaceX's timeline is theoretically I think something like first Cargo Starship 2024 / humans 2026. Realistically maybe cargo 2026 / humans 2029, or 2031 if the first cargo landing fails. So that means they will need to start planning their ISRU fairly soon. Thorium reactors etc. won't be available in time. And solar is advancing fast on Earth, and given the connection to Tesla solar and battery expertise is readily available.

It's not that nuclear solutions wouldn't work, but they are likely to be "bypassed" - solar will be large enough scale to make them irrelevant before they are ready to use on any significant scale*.

*Kilopower is nowhere near large enough for fueling Starships... life support backup power, maybe, but if a fleet-of-Starships-fuel-ISRU scaled solar array produces more power than the Kilopower during a bad dust storm, what's the point?

There's also a possible "PR" side of this, Elon Musk wants solar+batteries to win out on Earth (eg Tesla Energy, Solar City). Proving a city on Mars can work that way may have value to him.

https://www.seia.org/initiatives/concentrating-solar-power

Here is a link about solar concentrator plants currently producing power in the US.

I think (from previous discussions here) concentrators are much more dependent on direct sunlight (vs diffused light) than regular solar panels, thus dust storms hit them way harder than regular panels.

All but one of the plants listed are in the desert Southwest (CA/NV/AZ) with very clear skies.

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/03/2021 11:11 pm
Carbon monoxide "industrial plant gas" is a low energy fuel that is sometimes an industrial by product that, while not cost effective to pipe elsewhere, is useful when burned in the plant where it was produced and can be used as chemical feed stock. Producing CO and O2 might be a useful sink for excess energy when hydrogen is not available for making methane, ammonia etc. The Boiling point of CO is between N2 and O2 so the capability to liquify it should be a available. Might make a suitable propellant for short haul "taxi" vehicles too, which could reduce demand or at least diversion of hydrogen from higher priority uses. The chemical plant that will be a Mars city will need more than just power and have "interesting" logistics.  :o
During the "gaslight era", prior to the extensive production of natural gas, essentially all gas was "coal gas", which was a mixture of hydrogen and carbon monoxide. The local gasworks remained in use well into the 1950's in many places. So yes, you can use the CO. However, it's dangerous because CO poisoning is a whole lot more deadly than risk of NG explosion. This is why suicide by sticking your head in the oven no longer works.
CO isn’t any worse than ammonia, by the way.
CO is worse because it is indetectable without instruments.  That's why we have CO alarms in our houses bu not NH3 alarms. But back on topic: any energy storage system is "dangerous" by definition and must therefore be properly engineered for safety. This requirement will affect the costs of different systems differently, and for Mars, the big consideration will be the further tradeoff between local manufacturing versus importation from Earth. An inefficient system produced locally may have a higher absolute output than an efficient imported system.
Not a problem on Mars as any CO tanks would be outside in the near-vacuum where you can't breathe anyway.
Title: Re: Power options for a Mars settlement
Post by: Nevyn72 on 11/03/2021 11:12 pm
One of the biggest problems with the reduction of available solar energy during dust storms is the dust storm.

Not only is the available energy reduced to ~2% as mentioned earlier, the ability to collect that reduced energy is hindered by dust settling on the solar collectors.

The solar array may be able to support minimal power requirements with a ~2% solar availability but if you then cover those panels with dust they will not be able to harvest even a fraction of the reduced available energy.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/03/2021 11:23 pm
One of the biggest problems with the reduction of available solar energy during dust storms is the dust storm.

Not only is the available energy reduced to ~2% as mentioned earlier, the ability to collect that reduced energy is hindered by dust settling on the solar collectors.

The solar array may be able to support minimal power requirements with a ~2% solar availability but if you then cover those panels with dust they will not be able to harvest even a fraction of the reduced available energy.
The 2.5% INCLUDES the reduction from dust sitting on the solar arrays, actually. It's measured output from Mars Exploration Rover Opportunity's solar panels, which were basically worst-case as they were horizontal and had no way to remove dust.

Likely the solar output would be much higher if you had tracking ability to turn the solar arrays so the dust falls off or at least doesn't accumulate. You could also go out there and clean them off.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/04/2021 12:46 pm
How about the question of energy distribution?

For example, how far might we put a solar farm that got better operations due to location from a settlement that wanted to be near a favorable ice pocket?  An initial exploration base would try to combine everything on one spot, but larger settlement might spread out?  Or is the cost of distribution infrastructure so high, or the actual differences in solar output , or the cost of solar infrastructure, so low that it is not worth it?

The same applies to nuclear reactors, although these have the added twist that the waste heat might be lost in a remote location, but useful for a nearby settlement.  Or a nearby fuel production plant.

What might be the interest for a secondary power distribution system, for example oxygen and methane trucks, compared to a primary electrical distribution system?  Or might we always be better off with a highly distributed production infrastructure that allows for the local production of oxygen and methane, where the excess production is brought back to a central launch site?



Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/04/2021 03:30 pm
Here in western PA mine subsidence is a fact of life.  Arctic regions have to consider permafrost subsidence.  Because of these considerations I am of the opinion that we want to put the spaceport, solar farm, and propellant plant some distance away from the ice mine.  Another consideration I believe is worth mentioning is debris from RUDs.  We wouldn't want an exploding Starship or propellant plant to take out our solar farm so I am of the opinion that the solar farm should be some distance from the spaceport and propellant plant.  Therefore my current opinion is that we're going to want three sites.  Electrical transmission lines will be needed to connect the sites.
Title: Re: Power options for a Mars settlement
Post by: butters on 11/04/2021 04:05 pm
How about the question of energy distribution?

For example, how far might we put a solar farm that got better operations due to location from a settlement that wanted to be near a favorable ice pocket?  An initial exploration base would try to combine everything on one spot, but larger settlement might spread out?  Or is the cost of distribution infrastructure so high, or the actual differences in solar output , or the cost of solar infrastructure, so low that it is not worth it?

The same applies to nuclear reactors, although these have the added twist that the waste heat might be lost in a remote location, but useful for a nearby settlement.  Or a nearby fuel production plant.

What might be the interest for a secondary power distribution system, for example oxygen and methane trucks, compared to a primary electrical distribution system?  Or might we always be better off with a highly distributed production infrastructure that allows for the local production of oxygen and methane, where the excess production is brought back to a central launch site?
Almost regardless of other power infrastructure design choices, there's going to be at least one large-scale battery installation as part of the system. We can assume that the batteries will be palletized and that there must be a method to move the battery pallets over the surface to facilitate deployment, either by tractor vehicles or by self-propelled pallets.

If there's a need to distribute energy over longer distances than would be practical with high-voltage cable, then I think the simplest and most efficient thing to do would be to drive the batteries around. Battery-powered rovers can perform the same function when moving crew and/or cargo in addition to energy. The company that is most likely to be at the center of all this would surely prefer to use big batteries on wheels over combustion engines or fuel cells which consume the products of a relatively-inefficient IRSU process.

As for waste heat, let's assume that most/all base elements have a fluid cooling loop and a radiator. The first thing to add would be a heat recovery generator. Run the hot coolant through the hot side of a Stirling engine upstream of the primary radiator, and the cold side of the Stirling engine would have its own radiator or buried ground loop to exploit the natural abundance of cold on Mars.

The next thing would be to take the residual heat from the outlet of the Stirling engine and use it to heat regolith for water distillation. And of course they could bypass coolant around the Stirling engine to the regolith sublimator if battery state of charge is high. It may not make sense for each base element to have all of this heat recovery hardware. It may make more sense to have an external cooling loop so that multiple base elements can share a heat recovery unit. Maybe the Stirling generators are distributed but the regolith sublimators are centralized.

Plenty of implementation options here, especially with the addition of Kilopower reactors with high heat output. But the overall strategy is basically: Use waste heat to generate electricity if possible, otherwise reject to cold regolith and collect water/CO2 if possible, and the radiator is the heat rejection method of last resort to protect equipment under all scenarios.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/04/2021 06:27 pm
The idea of MW-level power transmission using batteries on wheels strikes me as something that isn't going to be anywhere near as good as installing power lines.  Engineer is done with numbers though so I'm willing to be convinced otherwise.  Off of the top of my head I can think of several critical questions that need to be answered.

- Off-road transfer is going to take longer and require more power.  What is required to build a durable smooth road that can handle high speed traffic on Mars?

- How fast can the rover go?

- What is the energy density of the rovers in kWh/kg?

- How long do the rovers take to charge and discharge?

- What are the road and rover's maintenance requirements in terms of both labor and spare parts?

- What percentage of the rover's charge is consumed by the rover?

- What is required to install power lines on Mars?

- What is the mass per km of the power lines?

- What is the efficiency of the power lines?

- What are the maintenance requirements of the power lines?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/04/2021 06:29 pm
Power lines is easily the better option.

I mean… there are high voltage power lines on Earth going literally thousands of kilometers (over 3000km), the same as the radius of Mars. That’s equivalent to roughly going from the equator of Mars to 60 degrees latitude.

That’s longer than just about any practical off-road rover, particularly if hauling batteries.

Power lines are more efficient and are automated.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 11/04/2021 06:49 pm
Exception being when the begin and end of the power line is constantly in motion. Like drilling a tunnel.
So it depends on how long both ends of the power line will there before they move. Months, Years?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/04/2021 07:10 pm
A lot of large mining equipment on Earth uses a flexible, movable electrical cable. The largest machines on Earth, the giant Bucketwheel Excavators, are electrically driven in this manner.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/04/2021 07:12 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.
Title: Re: Power options for a Mars settlement
Post by: Kenm on 11/04/2021 10:05 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.
Title: Re: Power options for a Mars settlement
Post by: yakman2020 on 11/04/2021 10:42 pm
I wonder if this would be a reasonable use case for microwave transmission, either ground or from orbit.

There was serious consideration of such things from Earth but a number of factors came into play that aren't necessarily present on Mars. This would even be reasonable if the power was ground based.

Of course wires properly designed might allow vehicle recharging power to be made available along the route, even where people aren't.
Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/04/2021 11:24 pm
At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

I vaguely remember reading about an unexpected high voltage arcing problem on Mars many moons ago.  My memory suggests the problem was with Curiosity's laser but numerous searches over the last few years have come up empty.  Perhaps Paschen's law in action was what I am recalling.

Then again perhaps not.  Either way I'm pretty sure avoiding arcing problems is an actual issue that will require insulation mass that we don't need to use for transmission lines here on Earth.  Thank you for raising science that supports why I chose to ask how much mass per km Martian power lines will require instead of extrapolating based on terrestrial power lines.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/05/2021 12:23 am
What sort of mileage would you get using a 9m dia stainless tank designed for 6 bar? The mass should work out as a freebie.  :D

Robotbeat raises a valid point about hydrogen embrittlement.  Another concern that pops into my head quickly is that valves rated for hydrogen are required.  Handwaving away these concerns a 800 m3 main LOX tank should hold ~430 kg of gaseous hydrogen and a 600 m3 main LCH4 tank should hold ~320 kg.  The header tanks are also an option but these are going only hold on the order of 10 kg each.

I wouldn't call this a freebie.  A Martian propellant plant is going to need somewhere to store LOX and LCH4.  Nitrogen and argon storage is also highly desirable.  If we repurpose one Starship for LOX and LCH4 storage and another for gaseous nitrogen and argon storage we'd need a third so that there is a large enough tank available for gaseous hydrogen.
Yup, H2 is rough on steel. Didn't think of that.


We don't have any real sense of the economics of returning SS for reuse. Except for crew return, the first synod will probably be no deposit, no return. The interplanetary tech will still be changing fast enough, and the value of tankage and materials will be high enough, to not bother. Later on they might load up some engines for return.


Robotbeats zero power sounds nasty. Technically doable, but there would be murder and mayhem. I lost power for a couple of hours a few months ago. Didn't want to open the fridge or use the phone, 'cause I didn't know how long it would last. It was daylight so I could read a physical book. At least every five minutes I had to quash an impulse to do XYZ, because of no power. Modern humans are not built to run without power. Sad, but true.

Title: Re: Power options for a Mars settlement
Post by: Joseph Peterson on 11/05/2021 01:20 am
Yup, H2 is rough on steel. Didn't think of that.

It depends of the type of steel.  316L has worked well enough in my small prototypes.  These have been very small scale with limited run times though.  I think a nickel plating should mitigate hydrogen embrittlement sufficiently for industrial scale production but until I have a good way to extract CO2 from Earth's atmosphere it isn't worth risking the limited capital I have access to to find out for sure.

Quote
We don't have any real sense of the economics of returning SS for reuse. Except for crew return, the first synod will probably be no deposit, no return. The interplanetary tech will still be changing fast enough, and the value of tankage and materials will be high enough, to not bother. Later on they might load up some engines for return.

Agreed.  Tanks of the scale needed to store a Starship's worth of propellant are hard to ship off world.  Repurposing Starships on Mars as tanks makes a lot of sense.

Quote
Robotbeats zero power sounds nasty. Technically doable, but there would be murder and mayhem. I lost power for a couple of hours a few months ago. Didn't want to open the fridge or use the phone, 'cause I didn't know how long it would last. It was daylight so I could read a physical book. At least every five minutes I had to quash an impulse to do XYZ, because of no power. Modern humans are not built to run without power. Sad, but true.

I agree about zero power.  Back in 2017 I dealt with a microburst that ripped the roof off of an ice cream factory and onto the only remaining transmission line(thank you deregulation) into my neighborhood.  Obviously I survived but that incident convinced me it was worth purchasing a gasoline powered generator that can run my fridge with a couple hundred watts to spare.

Luckily for future Martian settlers there are no existing ice cream plants with roofs that can be ripped off.  Even still having a backup generator that can run on stored methalox is something I fully believe is worth shipping on the first crewed mission.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/05/2021 05:41 am
Luckily for future Martian settlers there are no existing ice cream plants

 >:(
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/05/2021 06:18 am
What might be a good reference for the solar power available during a dust storm?  The direct vs diffuse issue is a really interesting point and I would love to document is on Marspedia.

Replied to Lamontagne via DM yesterday about dust vs solar production. Was in a hurry and didn't want to read through the replies in detail.

For anyone interested, here's a couple of nice papers of atmospheric opacity across many Mars years, and the corresponding amount of sunlight reaching the ground.

The first paper is just about the Viking missions, it's useful because it very nicely splits direct vs indirect (scattered) sunlight levels for different levels of atmospheric opacity. It also explains a lot of terminology and methodology in a way that's good for lay-readers. (And lots of the all important graphs.)

J Appelbaum and DJ Flood, Solar Radiation on Mars, NASA Technical Memorandum 102299, Lewis Research Center. (1989)
http://large.stanford.edu/courses/2017/ph240/black1/docs/nasa-tm-102299.pdf (http://large.stanford.edu/courses/2017/ph240/black1/docs/nasa-tm-102299.pdf)

This is a newer summary-of-the-science paper that covers all the landers and rovers up to the publication date.

Martínez, G.M., Newman, C.N., De Vicente-Retortillo, A. et al. The Modern Near-Surface Martian Climate: A Review of In-situ Meteorological Data from Viking to Curiosity. Space Sci Rev 212, 295–338 (2017)
https://link.springer.com/article/10.1007/s11214-017-0360-x (https://link.springer.com/article/10.1007/s11214-017-0360-x)

Both papers are fully available without a paywall.

[If you haven't encountered it before, "Solar Longitude" (Ls) is a way of measuring the time of year. It isn't related to the geographic longitude.]

BTW the entire settlement will need to be designed for significant solar variability and therefore be significantly overbuilt and probably have large amounts of time when there is much more solar power than needed.

I've mentioned before that Mars years are roughly divided in two parts, half a year (nearly 12 months) of higher optical clarity and higher overall insolation, and the other half (nearly 12 months) of higher tau, lower insolation and also greater variability.

So if using solar PV, there might be a fuel-production "season" that takes advantage of the clearer skies (tau<1), rather than trying (at least early on) to produce enough power during tau>2.

The amount of power required for propellant production seems to greatly eclipse that required for everything else. Cutting it for half the (Mars) year lets you run agricultural grow-chambers year around, only needing to cut back food production power-use for a month of so during large storms once every three years, and for several months during global monster storms about once-per-decade; in order to free up enough power to run life-support/comms/etc. That drastically reduces the danger of settlement loss, even if you are solely reliant on solar power.

Still need to deal with the diurnal variation, but IMO you want enough energy storage to deal with at least a couple of days of power-out no matter what the source of energy, solar, wind, nuclear, in case of a failure of a higher level system (like burning out a major interconnector between the power generator and the base.) However, I think that emergency "at least a couple of days" can include having all large battery-powered vehicles plugged in and returning power to the settlement. (Judging by electric cars vs power-wall for homes, vehicles use significantly more power than people. Obviously power use is higher in an artificial habitat than in a family home, but vehicles are going to be more industrial too. I don't think the battery packs in mining/excavation/transport vehicles will be insignificant.)

[Lamontagne replied noting that "a couple of days" under normal loads might be stretched to tens of days or more in emergencies.]
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/05/2021 04:07 pm
I think that SpaceX will avoid long-term hydrogen storage due to its handling issues etc.

Having some kind of combustion generator to turn already-produced CH4/O2 back to electricity does make sense.

However, if you have enough solar capacity to do life support in a worst-case dust storm it is IMO not at all plausible that something will kill your solar capacity, so dissimilar redundancy may not be important. A solar farm to fuel a bunch of Starships will be large - what is going to destroy it that doesn't also destroy the settlement completely (e.g. large asteroid impact)?

If NASA offers SpaceX a Kilopower reactor without a lot of extra paperwork that might impact schedule they would probably take it. But I don't think it would really be all that valuable except as an experiment. Solar and batteries are being improved with lots of investment now; nuclear is a relatively static technology. Solar+batteries will look a lot better 10-20 years from now than it does now; even working fusion might have trouble winning that trade.
I admire your optimism on the reliability of solar/battery on Mars but wouldn't want to bet my life on it. It not a question of something going south, it's when two or more things go south.


Dust storms are predictable in a general way but some are worse than others. This even has a cyclical recurrence but our data is too thin to claim a firm handle on how bad it can get. A dense, long lasting dust storm could be the first bad thing to happen.


For the second, I think an asteroid is a bit over dramatic. I know enough about solar/battery on an industrial scale to have a good idea of how much I don't know, so any specific I might come up with can probably be shot down. One that does comes to mind is fines penetrating the control boxes and creating an unexpected progressive corrosion - in the middle of a bad dust storm.


It's the things that aren't thought of that get you. Just look at the history of automotive recalls and WW2 torpedoes that didn't work in the Pacific because they were tested in the Atlantic. The list is long.


A kilopower would be very nice to have for a last ditch survival effort but still a big unknown, for both dependability and availability. One big ICE generator, or better yet, several small ones, would be great. In the end no approach is without risk. It's a question of reducing the risk as much as possible.
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 11/05/2021 04:18 pm
What about space-based solar power (SBSP) for Mars? It's energetically cheaper to launch at mars than at Earth if manufactured on the planet, and launch costs in general must be far lower than today to allow for a Mars settlement at all. If the system is manufactured on Earth, it must enter Mars orbit anyway. If the system is manufactured with ISRU, the economics are different. A technical question: how is the beamed (microwave?) power affected by a dust storm?
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/05/2021 04:41 pm
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
Absolutely. A power backup system is intended to get you by until the power comes back on.


So, the question still hangs. What's a reasonable per capita power budget to maintain an early mars base at survival levels? Figure 12-20 crew. I expect there are economies of scale with growth.

It really depends. You could in principle operate with no electric power at all. Manually operated valves for the oxygen supply and regenerative CO2 scrubbers operated by manual valves as well. Extremely well-insulated interior (easy to vacuum insulate stuff) kept warm by metabolic heat and thermal mass.

But if you have 500kilowatts average power (about 3MW peak power) during clear skies to make propellant, you'd STILL have tens of kilowatts average power in a dust storm, plus lots of storage as well (depending on if you designed your electrolysis to operate near 24/7 or just during the day). That is enough for contingency base power.

Not saying it's a bad idea to have a backup generator (with waste heat for heating the hab) that can run on some of the ISRU methane and oxygen propellant, though.
What might be a good reference for the solar power available during a dust storm?  The direct vs diffuse issue is a really interesting point and I would love to document is on Marspedia.  As storms are very variable, I wonder what might be the maximum planed length for a period of low solar availability?

BTW the entire settlement will need to be designed for significant solar variability and therefore be significantly overbuilt and probably have large amounts of time when there is much more solar power than needed.  In such a situation, the possibility of interrupting the Sabatier and electrolysis might be a good asset. A thermal battery used for a quick startup might be a good option?
Here's a NASA article on dust storms. More qualitative than quantitave. [size=78%]https://www.nasa.gov/feature/goddard/the-fact-and-fiction-of-martian-dust-storms (https://www.nasa.gov/feature/goddard/the-fact-and-fiction-of-martian-dust-storms)[/size]


You're dead on about having to overbuild but  shutting down propellant production rubs the wrong way. It looks as if power will be the big bottleneck on everything, so why not take a bonus when available?


It's argued that batteries are more economical but that ignores the fact that they have to be shipped from earth. Every ship that does not return to earth is essentially freebie power storage.


What to use the methalox for? Well, the logical starting point is backup power generators. Another is to make up production shortfalls or storage failures that might later happen. Methalox in times of no need is better than need in times of no methalox.*


*adapted from Freewheelin Franklin.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/05/2021 05:39 pm
...
The amount of power required for propellant production seems to greatly eclipse that required for everything else. Cutting it for half the (Mars) year lets you run agricultural grow-chambers year around, only needing to cut back food production power-use for a month of so during large storms once every three years, and for several months during global monster storms about once-per-decade; in order to free up enough power to run life-support/comms/etc. That drastically reduces the danger of settlement loss, even if you are solely reliant on solar power.
...

True at least in the short term, but if a self sustaining base is going to be developed some sort of integrated biosphere will probably be required.

It would need to produce food and oxygen, recover water and remove and recycle human waste and carbon dioxide. For even a small crew the amount of power required will be substantial, but worse from a power perspective such a system will have a limited capacity for dealing with power outages.

If the light or heat have been off or too low for too long the  the system will start to die and will eventually be destroyed. Propellant production can be stopped and an overage built in, but the same is not so true of a biological life support system.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/05/2021 06:22 pm
...
The amount of power required for propellant production seems to greatly eclipse that required for everything else. Cutting it for half the (Mars) year lets you run agricultural grow-chambers year around, only needing to cut back food production power-use for a month of so during large storms once every three years, and for several months during global monster storms about once-per-decade; in order to free up enough power to run life-support/comms/etc. That drastically reduces the danger of settlement loss, even if you are solely reliant on solar power.
...

True at least in the short term, but if a self sustaining base is going to be developed some sort of integrated biosphere will probably be required.

It would need to produce food and oxygen, recover water and remove and recycle human waste and carbon dioxide. For even a small crew the amount of power required will be substantial, but worse from a power perspective such a system will have a limited capacity for dealing with power outages.

If the light or heat have been off or too low for too long the  the system will start to die and will eventually be destroyed. Propellant production can be stopped and an overage built in, but the same is not so true of a biological life support system.
You could probably send them food, and a well designed settlement might want to store over a year of food as a backup plan. 
I Wonder what is the time of travel for a worst case scenario, with a Starship loaded up for fastest possible travel time?  That might define your minimum amount of food reserve?  And also perhaps define how much you can par down the food production power.

At about 1 tonne of food per year per person, 100 tonnes, or 1 Starship of ration packs, could feed 50 for 2 years.  Might make sense to include one of these in the first few Starships to Mars.  Simpler than a robust self sustaining ecosystem.

One of the interesting points of solar might be that is should be a very robust and distributed architecture, while a large central nuclear plant would be in a way less robust.  Perhaps a multitude of small reactor would also provide redundancy.
Title: Re: Power options for a Mars settlement
Post by: guckyfan on 11/05/2021 06:28 pm
A settlement can be prepared. Food stocks are an ancient method to deal with bad times. Same with oxygen. Survival level power should not be too much, with MW of solar panels deployed, even when production drops to 5%.

I am thinking of one situation. What happens when the first crew arrives during a dust storm? They will have food and oxygen for several months, but what about power, if nothing or very little is deployed?
Title: Re: Power options for a Mars settlement
Post by: Alberto-Girardi on 11/05/2021 06:47 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.

Interesting! I thought that the lower athmospheric pressure would mean that arcs are more difficult, and such the distance beetween cables lower. (I have no experience on the field, so mine was just a guess that I had assume right). Thanks for bringing this point up.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 11/05/2021 06:56 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.

Interesting! I thought that the lower athmospheric pressure would mean that arcs are more difficult, and such the distance beetween cables lower. (I have no experience on the field, so mine was just a guess that I had assume right). Thanks for bringing this point up.

The old 4 foot fluorescent tubes use reduced pressure and mercury to make the arc easier to get going.
Something to do with mean free path of an electron increases with reduced pressure allowing it to achieve a higher velocity and then ionize the gas.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 11/05/2021 07:16 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.

Interesting! I thought that the lower athmospheric pressure would mean that arcs are more difficult, and such the distance beetween cables lower. (I have no experience on the field, so mine was just a guess that I had assume right). Thanks for bringing this point up.

The old 4 foot fluorescent tubes use reduced pressure and mercury to make the arc easier to get going.
Something to do with mean free path of an electron increases with reduced pressure allowing it to achieve a higher velocity and then ionize the gas.
Interesting - easier to initiate the spark, but then at some point the lower density means it's harder to maintain it.

Sounds like Mars may have a worst case situation in that respect.

However, with much less wind force and with 0.4x gravity, one can build taller towers, and have larger spans between them.   Separation between wires can be addressed vertically since there's no highway traffic underneath.
Title: Re: Power options for a Mars settlement
Post by: Alberto-Girardi on 11/05/2021 07:20 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.

Interesting! I thought that the lower athmospheric pressure would mean that arcs are more difficult, and such the distance beetween cables lower. (I have no experience on the field, so mine was just a guess that I had assume right). Thanks for bringing this point up.

The old 4 foot fluorescent tubes use reduced pressure and mercury to make the arc easier to get going.
Something to do with mean free path of an electron increases with reduced pressure allowing it to achieve a higher velocity and then ionize the gas.


Yup. The behavior of arcs versus pressur is way more complicated tha I thought. My stupidly wrong assumption was based only on two data points: that in vacuum there are no arcs and that in  standard conditions there are.

Coming back on topic I don't think that for the early stage of the colony high voltage transmission won't be used, because IMO having the solar farm (which I'm pretty sure will provide most of the energy for the base) close to the base will allow for faster maintenance and simpler upgrade. On the other side if water mining requires to be further away from the base, for whatever reason (one possible is that  the mining method of choice might  cause terrain instabilities), such transmission lines might be needed.
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 11/05/2021 07:24 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.

Interesting! I thought that the lower athmospheric pressure would mean that arcs are more difficult, and such the distance beetween cables lower. (I have no experience on the field, so mine was just a guess that I had assume right). Thanks for bringing this point up.

The old 4 foot fluorescent tubes use reduced pressure and mercury to make the arc easier to get going.
Something to do with mean free path of an electron increases with reduced pressure allowing it to achieve a higher velocity and then ionize the gas.
Interesting - easier to initiate the spark, but then at some point the lower density means it's harder to maintain it.

Sounds like Mars may have a worst case situation in that respect.

[...snip...]
Yes - hard vacuum is a pretty good insulator, but low pressure gas is terrible.  Low pressure -> longer mean free path for ions/electrons before they can collide and neutralize each other -> more time for these charged particles to accelerate in the electric field and gain sufficient energy to cause further ionization.  In high pressure gas, the mean free path is too short for this to occur.  This is why quite a bit of high voltage gear gets internally insulated with a very difficult to ionize gas at high pressure.  SF6 is the usual suspect here.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 11/05/2021 07:38 pm
So anybody done the calc?
MV/m for martian air?
Title: Re: Power options for a Mars settlement
Post by: meekGee on 11/05/2021 08:04 pm
Was just searching for it...

Haven't read it yet :)
Title: Re: Power options for a Mars settlement
Post by: cdebuhr on 11/05/2021 08:06 pm
Was just searching for it...

Haven't read it yet :)
Nice find, although from the abstract, I'm not sure how Mars-relevant it will be.  The range of pressures investigated go from 0.1 MPa to 15 MPa (1-150 bar).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 11/05/2021 08:12 pm
Was just searching for it...

Haven't read it yet :)
Nice find, although from the abstract, I'm not sure how Mars-relevant it will be.  The range of pressures investigated go from 0.1 MPa to 15 MPa (1-150 bar).
Yeah, disappointment.  But google has more.

Interestingly, can't see the reverse trend discussed above, they must come into play only below the lowest pressures used.

I found another paper, but needed to request access from the author, let's see how charitable he is.  (Abderrahmane Beroual, Ecole Centrale de Lyon - Ampere Lab)

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/05/2021 08:31 pm
A settlement can be prepared. Food stocks are an ancient method to deal with bad times. Same with oxygen. Survival level power should not be too much, with MW of solar panels deployed, even when production drops to 5%.

I am thinking of one situation. What happens when the first crew arrives during a dust storm? They will have food and oxygen for several months, but what about power, if nothing or very little is deployed?
I don't think 5% is enough to feed people.  5% is less than a Canadian winter, and you don't grow food in the snow!
5% is probably enough to survive without too much difficulty and maintain life support, but probably not enough for even the lightest possible production of goods.

A lot depends on the mission plan.
If the plan is send robots, build up an inventory of propellant and send people when the time is right, then they just land in the dust storm.   There will already be plenty of solar rolled out, and plenty of fuel stored.  If absolutely needed, they can burn the stored fuel in a genset, and then make more when the sun shines.

If the plan is a foolhardy fly in and dive down with crew at the first try, then they just need the 2% available in even the worst storm to maintain the life support in a landed starship.  Setting up all the solar panels will move from "build up when needed" to "deploy all at once or we die". 
They could also run whatever leftover propellant they have through a fuel cell.  If (big if!) the power demand for a Starship life support is 22 kW, then one tonne of propellant is good for 90 hours of operation, or about 4 days.  If they can transfer left over propellant from some cargo ships, they might be able to have more time to deploy the solar cells.  As it is warmer during a storm, heat management might be an issue.  Alternatively, they might carry a pair of Kilopower units and set those up as fast as possible.

If the transfer orbit is aerobrake, get a stable orbit and land at your leisure then I guess they just stay in orbit for a few weeks.
 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/05/2021 08:38 pm
So anybody done the calc?
MV/m for martian air?
Why not just use insulated cable? The insulation is not the heaviest part anyway.  It would be more bulky, probably look more like telephone lines than power lines.  But you would not need to hang the line on insulators.

You likely cannot have ground return either, so the whole three wire distribution system might not be doable at all.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/05/2021 08:46 pm
...
The amount of power required for propellant production seems to greatly eclipse that required for everything else. Cutting it for half the (Mars) year lets you run agricultural grow-chambers year around, only needing to cut back food production power-use for a month of so during large storms once every three years, and for several months during global monster storms about once-per-decade; in order to free up enough power to run life-support/comms/etc. That drastically reduces the danger of settlement loss, even if you are solely reliant on solar power.
...

True at least in the short term, but if a self sustaining base is going to be developed some sort of integrated biosphere will probably be required.

It would need to produce food and oxygen, recover water and remove and recycle human waste and carbon dioxide. For even a small crew the amount of power required will be substantial, but worse from a power perspective such a system will have a limited capacity for dealing with power outages.

If the light or heat have been off or too low for too long the  the system will start to die and will eventually be destroyed. Propellant production can be stopped and an overage built in, but the same is not so true of a biological life support system.
You could probably send them food, and a well designed settlement might want to store over a year of food as a backup plan. 
I Wonder what is the time of travel for a worst case scenario, with a Starship loaded up for fastest possible travel time?  That might define your minimum amount of food reserve?  And also perhaps define how much you can par down the food production power.

At about 1 tonne of food per year per person, 100 tonnes, or 1 Starship of ration packs, could feed 50 for 2 years.  Might make sense to include one of these in the first few Starships to Mars.  Simpler than a robust self sustaining ecosystem.

One of the interesting points of solar might be that is should be a very robust and distributed architecture, while a large central nuclear plant would be in a way less robust.  Perhaps a multitude of small reactor would also provide redundancy.
With a properly functioning biological system it should be possible to grow an excess and freeze it and/or as you say additional food could be brought in. But the difficulty is keeping the system alive and in balance. It may be that such as system is not really practical until a time when large quantities of power are reliably available. In the meantime some sort of more conventional system might be used with more discrete parts that would be more switch off able. So live off of frozen or dried food during the sand storm and "replant" the farm when the lights come back on.
Title: Re: Power options for a Mars settlement
Post by: Nevyn72 on 11/05/2021 10:03 pm
So anybody done the calc?
MV/m for martian air?
Why not just use insulated cable? The insulation is not the heaviest part anyway.  It would be more bulky, probably look more like telephone lines than power lines.  But you would not need to hang the line on insulators.

You likely cannot have ground return either, so the whole three wire distribution system might not be doable at all.

It becomes a bit of a spectrum of options, I'd be interested in how the trades offset for the best result.

At one end you have tall towers with a large separation between uninsulated conductors, at the other extreme you have insulated conductors lying on the ground (or even buried) with no towers and minimal separation.

I suspect what portions can be manufactured with ISRU would be a big consideration...
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/06/2021 03:40 am
The idea of MW-level power transmission using batteries on wheels strikes me as something that isn't going to be anywhere near as good as installing power lines.  Engineer is done with numbers though so I'm willing to be convinced otherwise.  Off of the top of my head I can think of several critical questions that need to be answered.

- Off-road transfer is going to take longer and require more power.  What is required to build a durable smooth road that can handle high speed traffic on Mars?

- How fast can the rover go?

- What is the energy density of the rovers in kWh/kg?

- How long do the rovers take to charge and discharge?

- What are the road and rover's maintenance requirements in terms of both labor and spare parts?

- What percentage of the rover's charge is consumed by the rover?

- What is required to install power lines on Mars?

- What is the mass per km of the power lines?

- What is the efficiency of the power lines?

- What are the maintenance requirements of the power lines?
If motive power is needed in a high density area wire is the way to go. Things like construction and utility vehicles, cargo or people movers and the like. On board batteries and either charging stations or battery swap.


When off the beaten path the rules change. Survey & exploration travel and point to point over a distance. Any route with high enough traffic becomes a candidate for transmission lines. Until the lines happen there are options for power.


Straight solar/battery is proven but sloooowww. Even with high efficiency PV cells vehicles don't have enough surface area
To generate all that much power and free standing arrays aren't practical while moving. Or travel one day and recharge for three.


Alternatively, hitch a propellant trailer and go. With some cunning engineering a battery electric can have a mount point for an ICE/gen set. Use the exhaust heat to run Stirling/gens to keep the batteries topped off for nightly hotel loads. Condense water out of the exhaust. Need to go really far? Hitch on a bigger props trailer.


Or, set up a big R&D program to figure out a really slick power system that costs more and is less reliable.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/06/2021 10:20 am
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law (https://en.wikipedia.org/wiki/Paschen%27s_law)).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.

Interesting! I thought that the lower athmospheric pressure would mean that arcs are more difficult, and such the distance beetween cables lower. (I have no experience on the field, so mine was just a guess that I had assume right). Thanks for bringing this point up.

The old 4 foot fluorescent tubes use reduced pressure and mercury to make the arc easier to get going.
Something to do with mean free path of an electron increases with reduced pressure allowing it to achieve a higher velocity and then ionize the gas.


Yup. The behavior of arcs versus pressur is way more complicated tha I thought. My stupidly wrong assumption was based only on two data points: that in vacuum there are no arcs and that in  standard conditions there are.

Coming back on topic I don't think that for the early stage of the colony high voltage transmission won't be used, because IMO having the solar farm (which I'm pretty sure will provide most of the energy for the base) close to the base will allow for faster maintenance and simpler upgrade. On the other side if water mining requires to be further away from the base, for whatever reason (one possible is that  the mining method of choice might  cause terrain instabilities), such transmission lines might be needed.
Yes, distribution will evolve with the base/settlement. First synod might have free standing charging points with PV, one for each piece of mobile equipment, to support battery swap out. This gets them to work immediately with much welcome redundancy.


The PV on the ship may add in its bit to keep the itself alive with some help from more freestanding panels nearby. More panels for habitat, then the biggie for propellant production. If production and mining are not co-located, yet another PV farm.


Interconnect is good to have but not vital at first. The first crew is going to be elbows and sphincters just getting the minimum buildout up and running. Second mission can start adding some well prioritized refinement.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/06/2021 11:44 am
A settlement can be prepared. Food stocks are an ancient method to deal with bad times. Same with oxygen. Survival level power should not be too much, with MW of solar panels deployed, even when production drops to 5%.

I am thinking of one situation. What happens when the first crew arrives during a dust storm? They will have food and oxygen for several months, but what about power, if nothing or very little is deployed?
I don't think 5% is enough to feed people.  5% is less than a Canadian winter, and you don't grow food in the snow!
5% is probably enough to survive without too much difficulty and maintain life support, but probably not enough for even the lightest possible production of goods.

A lot depends on the mission plan.
If the plan is send robots, build up an inventory of propellant and send people when the time is right, then they just land in the dust storm.   There will already be plenty of solar rolled out, and plenty of fuel stored.  If absolutely needed, they can burn the stored fuel in a genset, and then make more when the sun shines.

If the plan is a foolhardy fly in and dive down with crew at the first try, then they just need the 2% available in even the worst storm to maintain the life support in a landed starship.  Setting up all the solar panels will move from "build up when needed" to "deploy all at once or we die". 
They could also run whatever leftover propellant they have through a fuel cell.  If (big if!) the power demand for a Starship life support is 22 kW, then one tonne of propellant is good for 90 hours of operation, or about 4 days.  If they can transfer left over propellant from some cargo ships, they might be able to have more time to deploy the solar cells.  As it is warmer during a storm, heat management might be an issue.  Alternatively, they might carry a pair of Kilopower units and set those up as fast as possible.

If the transfer orbit is aerobrake, get a stable orbit and land at your leisure then I guess they just stay in orbit for a few weeks.
All indications are that they plan for a straight in - no aerobraking to orbit. I don't know if it's possible (or not) to hit TMI for a straight in, then change your mind.  Of course SX has been known to change their mind so orbit might be the final plan. Landing in a dust storm would really suck.


IMO, strictly opinion, expecting robots to fully deploy equipment for and to produce ISRU props on the first try is wishful thinking. It would make the JWST deploy look simple. Each time it doesn't work the program is set back two years.


Better to bite he bullet and accept the high (really high) cost of imported fuel to return one crewed ship and be done with it. With the first crew setting up ISRU it should only happen once. Is this another example of famous last words?


Veering off topic, this sets some limits on the size of the first mission. On the high end it needs to fit into one return ship. On the low end it needs to be large enough to build out, start and troubleshoot the ISRU and get the ship ready to return. Everything else, habitat, exploration, food production, research and landing field, are secondary. Whatever labor is available between the undefined limits can work on the secondary tasks.


In a veer off from the veering off topic, there may be a hidden advantage is sending ships with return fuel. A logical ops plan would be slow transfer to martian orbit with ships acting as aggregators as is done earthside. As many ships as necessary land with fuel for the return ship to make orbit and top off. This leaves a lot of ships in orbit.


Make use of them. At minimum, earmark them for future orbital ops. More ambitiously, leave a enough fuel on a few to raise orbit and spread out enough to act as non line of sight coms relay (built in starlink), an earth relay, ground and weather observation, and rudimentary GPS. It would be mass wasteful compared to inserting stand alone sats, but so much simpler. A true quick and dirty until something better is available.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/06/2021 11:58 am
What would be the effect of a dust storm on pylons and cables? Obviously it will be easy to arrange that they don't blow down, but what about increased electrical conductivity, discharge or high electric fields etc?
https://link.springer.com/article/10.1007%2Fs11214-016-0241-8 (https://link.springer.com/article/10.1007%2Fs11214-016-0241-8)

Looks like we might get some more information fairly soon:
https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/ExoMars (https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/ExoMars)
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/06/2021 12:33 pm
Electrical transmission efficiency at around 50,000 Volts and higher is more mass and energy efficient than land transport using batteries. Keeping energy efficient constant, more mass efficient by a factor of 10.

At typical 69kV, let alone 325kV or higher, and the efficiency is even greater.

At Mars atmospheric pressure you need much larger gaps between the wires to avoid electrical breakdown or you have to use insulated wires.
As a first guess for a given voltage the minimum insulating gap between conductors times the atmospheric pressure will be a constant (see Paschen's law https://en.wikipedia.org/wiki/Paschen%27s_law).
 If you need 1 meter between the wires and the tower on Earth you will need 1 meter * 101kpa/0.6 kpa =167 meters on Mars! So it looks like we need to use insulated wire for high voltage transmission.

Although not something for an early settlement once there are long distance electrical transmission lines we can consider
running a line around Mars so there is always access to solar power and a line could be sent up Olympus where I think the sun shines even during the dust storms.
No, you don’t; you just need solid insulation like used for underwater or underground cables.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/06/2021 12:33 pm
What would be the effect of a dust storm on pylons and cables? Obviously it will be easy to arrange that they don't blow down, but what about increased electrical conductivity, discharge or high electric fields etc?
https://link.springer.com/article/10.1007%2Fs11214-016-0241-8 (https://link.springer.com/article/10.1007%2Fs11214-016-0241-8)

Looks like we might get some more information fairly soon:
https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/ExoMars (https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/ExoMars)
Lay the cables on the ground. Best part is no part.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/06/2021 01:31 pm
So anybody done the calc?
MV/m for martian air?
Why not just use insulated cable? The insulation is not the heaviest part anyway.  It would be more bulky, probably look more like telephone lines than power lines.  But you would not need to hang the line on insulators.

You likely cannot have ground return either, so the whole three wire distribution system might not be doable at all.
DC is now being used on the grid. [size=78%]https://en.m.wikipedia.org/wiki/High-voltage_direct_current (https://en.m.wikipedia.org/wiki/High-voltage_direct_current)[/size]


On Mars, all solar power, the bulk of production, will be DC as will be the battery storage. Go with DC transmission and use one hot and one ground. The voltages may be a bit radical. Keep them well separated, and insulated.

Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/06/2021 02:45 pm
So anybody done the calc?
MV/m for martian air?
Why not just use insulated cable? The insulation is not the heaviest part anyway.  It would be more bulky, probably look more like telephone lines than power lines.  But you would not need to hang the line on insulators.

You likely cannot have ground return either, so the whole three wire distribution system might not be doable at all.
DC is now being used on the grid. [size=78%]https://en.m.wikipedia.org/wiki/High-voltage_direct_current (https://en.m.wikipedia.org/wiki/High-voltage_direct_current)[/size]


On Mars, all solar power, the bulk of production, will be DC as will be the battery storage. Go with DC transmission and use one hot and one ground. The voltages may be a bit radical. Keep them well separated, and insulated.

May be a bit radical? Understatement deluxe! I am not sure the DC/DC conversion will be any cheaper than DC/AC either. The unsynchronized grid aspect may not apply so long distance transmission probably depends on what the Mars power grid looks like all the way down to small appliances and whether they go with AC or DC in the habitats and facilities.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/06/2021 04:36 pm
So anybody done the calc?
MV/m for martian air?
Why not just use insulated cable? The insulation is not the heaviest part anyway.  It would be more bulky, probably look more like telephone lines than power lines.  But you would not need to hang the line on insulators.

You likely cannot have ground return either, so the whole three wire distribution system might not be doable at all.
DC is now being used on the grid. [size=78%]https://en.m.wikipedia.org/wiki/High-voltage_direct_current (https://en.m.wikipedia.org/wiki/High-voltage_direct_current)[/size]


On Mars, all solar power, the bulk of production, will be DC as will be the battery storage. Go with DC transmission and use one hot and one ground. The voltages may be a bit radical. Keep them well separated, and insulated.

May be a bit radical? Understatement deluxe! I am not sure the DC/DC conversion will be any cheaper than DC/AC either. The unsynchronized grid aspect may not apply so long distance transmission probably depends on what the Mars power grid looks like all the way down to small appliances and whether they go with AC or DC in the habitats and facilities.
There is a potential for MVDC grids, and major manufacturers have white papers out on the subject.  It seems the power losses are lower overall.  So if you are starting from 0, using DC generation and DC loads, it might make sense to go DC all the way.  There are still many definitions for MVDC though, so it's not there yet.
One of the main reasons for AC, squirrel cage inductions motors, are often fed using variable frequency drives that kind of make the AC moot.
I would expect Starship to have a DC infrastructure, and that may color all that comes after?  Starship may use datacenter or solar station derived architectures, and those can by DC up to a few hundred volts.

Title: Re: Power options for a Mars settlement
Post by: LMT on 11/07/2021 06:50 pm
Go with DC transmission and use one hot and one ground.

May be a bit radical? Understatement deluxe! I am not sure the DC/DC conversion will be any cheaper than DC/AC either. The unsynchronized grid aspect may not apply so long distance transmission probably depends on what the Mars power grid looks like all the way down to small appliances and whether they go with AC or DC in the habitats and facilities.

There is a potential for MVDC grids, and major manufacturers have white papers out on the subject.  It seems the power losses are lower overall...

SWER could work, yes.

1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025020#msg2025020) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025411#msg2025411) 3 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025429#msg2025429)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/07/2021 07:16 pm
SWER.  Single Wire Earth Return. A type of AC or DC distribution.

Might be something of a pain creating the required deep electrodes but yes, seems quite doable.  If shorting to ground is too easy on Mars then insulation is required.  It might be logical to have two wire system with insulators and a grounding shield. That should be fairly tough and just laid onto the ground in many cases
I expect that in absolute terms there is far more insulated wiring than un insulated wiring in the overall electrical system of  modern society, so the insulation of power lines may be fairly trivial on the larger scale of things.




Title: Re: Power options for a Mars settlement
Post by: spacenut on 11/07/2021 07:30 pm
Solar panels can be installed at or near each colony or outpost.  No real need for long distance transmission of power on Mars as other than dust storms there are no cloudy days to keep from producing power.  Also, solar panels can eventually be mounted higher to avoid as much dust as possible and able to tilt to drop dust off when needed.  They could even offer some radiation protection if built over each habitat or greenhouse.  Greenhouse will probably be underground or have no glass and will use LED grow lights for 24/7 production of food. 

Storage of solar electricity will have to be worked out, and eventually probably some small scale nuclear power will be needed. 
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/07/2021 08:10 pm
...solar panels can eventually be mounted higher to avoid as much dust as possible

Dust can rise to 80 km (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1865573#msg1865573), unfortunately.

But you'd raise panels above ~ 1 m, to clear saltating sand.

Storage of solar electricity will have to be worked out, and eventually probably some small scale nuclear power will be needed.

Why not ISRU batteries (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) instead of nuclear:  saltwater batteries (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048640#msg2048640), iron flow batteries (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2306664#msg2306664), or other?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/07/2021 08:18 pm
Sure, dust CAN got that high, but largely doesn’t have a huge effect that high. During major dust storms, Olympus Mons tends to stay largely dust free even if the rest of the planet is covered in a global storm.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/08/2021 12:58 am
...Olympus Mons tends to stay largely dust free even if the rest of the planet is covered in a global storm.

No, that's not true.

Image:  "This animation (https://photojournal.jpl.nasa.gov/catalog/PIA22737) shows the evolution of the 2018 Mars global dust storm...  A tau of three indicates that only about 5 percent of the sunlight entering the atmosphere directly reaches the surface."  NASA/JPL-Caltech.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/08/2021 01:18 am
...Olympus Mons tends to stay largely dust free even if the rest of the planet is covered in a global storm.

No, that's not true.

Image:  "This animation (https://photojournal.jpl.nasa.gov/catalog/PIA22737) shows the evolution of the 2018 Mars global dust storm...  A tau of three indicates that only about 5 percent of the sunlight entering the atmosphere directly reaches the surface."  NASA/JPL-Caltech.
I think there's a mistake in that model. Optical images of global dust storms on Mars show Olympus Mons peaking out. That animation showed no apparent effect of olympus mons.

See, from the same dust storm: https://www.orlandosentinel.com/space/os-mars-dust-storm-olympus-mons-20180705-story.html
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/08/2021 01:52 am
...Olympus Mons tends to stay largely dust free even if the rest of the planet is covered in a global storm.

No, that's not true.

Image:  "This animation (https://photojournal.jpl.nasa.gov/catalog/PIA22737) shows the evolution of the 2018 Mars global dust storm...  A tau of three indicates that only about 5 percent of the sunlight entering the atmosphere directly reaches the surface."  NASA/JPL-Caltech.
I think there's a mistake in that model. Optical images of global dust storms on Mars show Olympus Mons peaking out. That animation showed no apparent effect of olympus mons.

See, from the same dust storm: https://www.orlandosentinel.com/space/os-mars-dust-storm-olympus-mons-20180705-story.html

It's not a model.  Read the NASA caption, and look at the dates.  What do you see when you do that?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/08/2021 02:33 am
...Olympus Mons tends to stay largely dust free even if the rest of the planet is covered in a global storm.

No, that's not true.

Image:  "This animation (https://photojournal.jpl.nasa.gov/catalog/PIA22737) shows the evolution of the 2018 Mars global dust storm...  A tau of three indicates that only about 5 percent of the sunlight entering the atmosphere directly reaches the surface."  NASA/JPL-Caltech.
I think there's a mistake in that model. Optical images of global dust storms on Mars show Olympus Mons peaking out. That animation showed no apparent effect of olympus mons.

See, from the same dust storm: https://www.orlandosentinel.com/space/os-mars-dust-storm-olympus-mons-20180705-story.html

It's not a model.  Read the NASA caption, and look at the dates.  What do you see when you do that?
Whatever. It's also not raw data, either, it's processed. Using a MODEL. Anyway, I could be wrong. But you can definitely see Olympus Mons in pictures when the rest of Mars looks like a dust orb.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/08/2021 03:21 am
It's not a model.  Read the NASA caption, and look at the dates.  What do you see when you do that?

Whatever. It's also not raw data, either, it's processed. Using a MODEL. Anyway, I could be wrong. But you can definitely see Olympus Mons in pictures when the rest of Mars looks like a dust orb.

"Whatever"?  Is that how you want people to respond to info you present?

Posters can understand the difference between a model and a calibrated measurement.

Likewise, the difference in observed storm conditions (https://photojournal.jpl.nasa.gov/archive/PIA22737.mp4) between July 1 and July 13, 2018, on Olympus Mons.
Title: Re: Power options for a Mars settlement
Post by: Voidfloater on 11/08/2021 05:44 am
It's not a model.  Read the NASA caption, and look at the dates.  What do you see when you do that?

Whatever. It's also not raw data, either, it's processed. Using a MODEL. Anyway, I could be wrong. But you can definitely see Olympus Mons in pictures when the rest of Mars looks like a dust orb.

"Whatever"?  Is that how you want people to respond to info you present?

Posters can understand the difference between a model and a calibrated measurement.

Likewise, the difference in observed storm conditions (https://photojournal.jpl.nasa.gov/archive/PIA22737.mp4) between July 1 and July 13, 2018, on Olympus Mons.

Interestingly, on July 8 2018 the Mars Reconnaissance Orbiter captured several images of Olympus Mons's surface, unobscured by dust. Moreover, the article describing the images mentions the height of the volcano as the reason why the surface is visible. [1] Meanwhile, the modeled data suggests that Olympus Mons is covered with dust to an optical depth of 3 tau.


[1]: https://www.uahirise.org/ESP_056010_1985 (https://www.uahirise.org/ESP_056010_1985)


Title: Re: Power options for a Mars settlement
Post by: LMT on 11/08/2021 12:54 pm
Interestingly, on July 8 2018 the Mars Reconnaissance Orbiter captured several images of Olympus Mons's surface, unobscured by dust. Moreover, the article describing the images mentions the height of the volcano as the reason why the surface is visible. [1] Meanwhile, the modeled data suggests that Olympus Mons is covered with dust to an optical depth of 3 tau.


[1]: https://www.uahirise.org/ESP_056010_1985 (https://www.uahirise.org/ESP_056010_1985)

The animation shows daily tau change; your photo was snapped between the worst days.

Think about your caption, re a 1971 storm: "As the storm ended and the dust began to settle out of the atmosphere, the tops of the giant volcanoes were the first portions of the surface to be seen."  An 80 km dust storm does cover a 22 km mountain.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/08/2021 12:59 pm
A tau of three indicates that only about 5 percent of the sunlight entering the atmosphere directly reaches the surface."

Solar PV doesn't require direct insolation, scattered light is fine and at Tau=3 will be around 30% of full sunlight.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/08/2021 02:00 pm
A tau of three indicates that only about 5 percent of the sunlight entering the atmosphere directly reaches the surface."

Solar PV doesn't require direct insolation, scattered light is fine and at Tau=3 will be around 30% of full sunlight.

What's Olympus tau in the image (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2307787#msg2307787), and transmission?

You misread storm PV hazards previously (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054635#msg2054635), so you might check assumptions.
Title: Re: Power options for a Mars settlement
Post by: Voidfloater on 11/08/2021 06:40 pm
Interestingly, on July 8 2018 the Mars Reconnaissance Orbiter captured several images of Olympus Mons's surface, unobscured by dust. Moreover, the article describing the images mentions the height of the volcano as the reason why the surface is visible. [1] Meanwhile, the modeled data suggests that Olympus Mons is covered with dust to an optical depth of 3 tau.


[1]: https://www.uahirise.org/ESP_056010_1985 (https://www.uahirise.org/ESP_056010_1985)

The animation shows daily tau change; your photo was snapped between the worst days.


I think you may be mistaken.  From the animation's source, it shows optical depth tau, which is a measure of how much light is blocked by atmospheric dust.  Tau is not a rate of change.  [1] This is stated in the first paragraph of the animation's caption. 


snip

Think about your caption, re a 1971 storm: "As the storm ended and the dust began to settle out of the atmosphere, the tops of the giant volcanoes were the first portions of the surface to be seen."  An 80 km dust storm does cover a 22 km mountain.


The article's first sentence mentions that the image in question was taken by HiRISE, a camera on the Mars Reconnaissance Orbiter.  This orbiter only arrived around Mars in 2006, therefore, the image cannot have been taken in 2001 as you imply.  [2]

Moreover, below the article the date the image was taken is given.  There are three columns which contain information about the image located just below the author's signature.  In the top left of the first column, the date the image was acquired is clearly stated: 08 July 2018 [2]

Thus, the reference to 1971 was a historical allusion which has little bearing on the image mentioned in the article. ​



The image of Olympus mons was clearly taken during the 2018 dust storm by the Mars Reconnaissance Orbiter.  The animation provided by the photojournal was an animated approximation of the 2018 dust storm.  On July 8 2018, an unobscured image of Olympus Mons was taken while the model's apparent tau over Olympus mons equaled 3.  Therefore, the model is inaccurate at very high elevations and Olympus Mons's summit is not covered by dust during dust storms. 

[1] https://photojournal.jpl.nasa.gov/catalog/PIA22737

[2] https://www.uahirise.org/ESP_056010_1985
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/08/2021 07:10 pm
Think about your caption, re a 1971 storm: "As the storm ended and the dust began to settle out of the atmosphere, the tops of the giant volcanoes were the first portions of the surface to be seen."  An 80 km dust storm does cover a 22 km mountain.

...the reference to 1971 was a historical allusion which has little bearing on the image mentioned in the article. ​

The meaning of your referenced caption is clear and still applicable.  It's hard to appreciate the scale of a storm that easily covers a 22 km mountain.  ISRU battery farms (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) and other TJ-scale energy storage systems could be very important, and such systems deserve creative thought.
Title: Re: Power options for a Mars settlement
Post by: Steve D on 11/08/2021 08:53 pm
Solar panels can be installed at or near each colony or outpost.  No real need for long distance transmission of power on Mars as other than dust storms there are no cloudy days to keep from producing power.  Also, solar panels can eventually be mounted higher to avoid as much dust as possible and able to tilt to drop dust off when needed.  They could even offer some radiation protection if built over each habitat or greenhouse.  Greenhouse will probably be underground or have no glass and will use LED grow lights for 24/7 production of food. 

Storage of solar electricity will have to be worked out, and eventually probably some small scale nuclear power will be needed.

They just have to be far enough away from the landing pads not to get shredded every time a Starship lands
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/08/2021 10:49 pm
SWER.  Single Wire Earth Return. A type of AC or DC distribution.

Might be something of a pain creating the required deep electrodes but yes, seems quite doable.  If shorting to ground is too easy on Mars then insulation is required.  It might be logical to have two wire system with insulators and a grounding shield. That should be fairly tough and just laid onto the ground in many cases
I expect that in absolute terms there is far more insulated wiring than un insulated wiring in the overall electrical system of  modern society, so the insulation of power lines may be fairly trivial on the larger scale of things.
The question that kicked this line off addressed the feasibility of earth return (mars return?) on Mars. It's pretty dry. is it known if it'll work?
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/08/2021 11:02 pm
So anybody done the calc?
MV/m for martian air?
Why not just use insulated cable? The insulation is not the heaviest part anyway.  It would be more bulky, probably look more like telephone lines than power lines.  But you would not need to hang the line on insulators.

You likely cannot have ground return either, so the whole three wire distribution system might not be doable at all.
DC is now being used on the grid. [size=78%]https://en.m.wikipedia.org/wiki/High-voltage_direct_current (https://en.m.wikipedia.org/wiki/High-voltage_direct_current)[/size]


On Mars, all solar power, the bulk of production, will be DC as will be the battery storage. Go with DC transmission and use one hot and one ground. The voltages may be a bit radical. Keep them well separated, and insulated.

May be a bit radical? Understatement deluxe! I am not sure the DC/DC conversion will be any cheaper than DC/AC either. The unsynchronized grid aspect may not apply so long distance transmission probably depends on what the Mars power grid looks like all the way down to small appliances and whether they go with AC or DC in the habitats and facilities.
There is a potential for MVDC grids, and major manufacturers have white papers out on the subject.  It seems the power losses are lower overall.  So if you are starting from 0, using DC generation and DC loads, it might make sense to go DC all the way.  There are still many definitions for MVDC though, so it's not there yet.
One of the main reasons for AC, squirrel cage inductions motors, are often fed using variable frequency drives that kind of make the AC moot.
I would expect Starship to have a DC infrastructure, and that may color all that comes after?  Starship may use datacenter or solar station derived architectures, and those can by DC up to a few hundred volts.
The western half of the ISS has 120v DC service. Weird, but true.
Title: Re: Power options for a Mars settlement
Post by: MickQ on 11/09/2021 08:57 am
Regarding storage of solar power, would it be feasible to use excess daytime PV to winch a weight uphill and then let said weight descend, under gravity, at night while turning the winch motor in reverse as a generator ??
Title: Re: Power options for a Mars settlement
Post by: strandolsen on 11/09/2021 09:20 am
Regarding storage of solar power, would it be feasible to use excess daytime PV to winch a weight uphill and then let said weight descend, under gravity, at night while turning the winch motor in reverse as a generator ??
Of course, using gravitational potential energy is a feasible way of storing energy.
See for instance Energy Vault, they have a demonstration unit in Switzerland (https://www.energyvault.com/ev1).
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/09/2021 11:53 am
Regarding storage of solar power, would it be feasible to use excess daytime PV to winch a weight uphill and then let said weight descend, under gravity, at night while turning the winch motor in reverse as a generator ??

It's possible, obviously, but the energy density is garbage.

Ep=mgh. In joules, kg, m/s, metres, respectively. So 1 tonne of mass on Mars gives you a mere 3.8kJ per metre of height, minus friction loss. Roughly 1 amp-hour per tonne/metre. 20% of my mid-range cellphone's battery. It's hard to get the kind of storage you'd need to make it worth building.

Outside of a few small-scale very low power niche applications, gravity storage only makes sense when you are using water and have existing very large containers (lakes/reservoirs) at the top and bottom. Even better if your "hoist" power is free (hydroelectric dams.) Schemes to hoist solid masses get thrown around occasionally, but these ultimately seem to be short-lived naive wishful thinking, or persist as investor scams.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 11/09/2021 02:57 pm
Regarding storage of solar power, would it be feasible to use excess daytime PV to winch a weight uphill and then let said weight descend, under gravity, at night while turning the winch motor in reverse as a generator ??
It works, but the lower gravity sucks.

I once calculated how much you could get by setting up the colony at the base if a mountain, and just continuously bringing dirt down.  (Mountains are big).

It's not insignificant, but it's still a lot of hassle compared to solar or nuclear.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/09/2021 03:21 pm
Regarding storage of solar power, would it be feasible to use excess daytime PV to winch a weight uphill and then let said weight descend, under gravity, at night while turning the winch motor in reverse as a generator ??
It works, but the lower gravity sucks.

I once calculated how much you could get by setting up the colony at the base if a mountain, and just continuously bringing dirt down.  (Mountains are big).

It's not insignificant, but it's still a lot of hassle compared to solar or nuclear.
Energy storage is likely to be batteries for short term (each night) because this is needed everyday and needs to be very efficient.  Production of food and fuel  should probably be seasonal, to take solar availability into account, and keep equipment in continuous production, or seasonally shut off, so we would have only one or two start ups per year, rather than every day.
Locally produced batteries would be fantastic, but likely not possible short term.
This might reduce the need for long term energy storage to emergency uses, and therefore probably oxygen and methane.
Fuel production may also be reduced significantly if we only return 1 out of every 5 or 10 starships.  Cargo starships might be systematically reused as habitats, in particular for the early years.
Has anybody checked how many engines you can stuff in a cargo starship, and is there any actual economical advantage in recuperating the engines, or might they just be stored locally for eventual recycling?



Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/09/2021 03:45 pm
Anything with moving parts is subject to wearing out eventually. Batteries suffer from analogous problems with finite charge cycles. So, local production of replacement machinery/parts, batteries/chemicals will be needed long term on Mars.

Some machines are less prone to wear than others, free piston Stirling comes to mind and some batteries last longer than others, Nickle Hydrogen (not NiMH) was used in satellites for that reason. The trade offs for use on Mars will probably be biased toward long life and reliability relative to Earth.

Of course without more info on what resources will be practically available on Mars it is hard to do more than speculate. Back to geology, prospecting, feed stocks and chemical plants I guess  ;)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/09/2021 03:59 pm
I revisited my design for the Mars Society 1000 people settlement contest from 2019 (didn't win  ;))

The numbers are for energy production, for the return of all the starships in the first case (40 ships), and return on only passenger Starships in the second case (7 ships).
Food production really takes the upper hand in the second case.

Mining goes down because we don't need as much ice.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/09/2021 04:42 pm
Anything with moving parts is subject to wearing out eventually. Batteries suffer from analogous problems with finite charge cycles. So, local production of replacement machinery/parts, batteries/chemicals will be needed long term on Mars.

Some machines are less prone to wear than others, free piston Stirling comes to mind and some batteries last longer than others, Nickle Hydrogen (not NiMH) was used in satellites for that reason. The trade offs for use on Mars will probably be biased toward long life and reliability relative to Earth.

Of course without more info on what resources will be practically available on Mars it is hard to do more than speculate. Back to geology, prospecting, feed stocks and chemical plants I guess  ;)

Nickel hydrogen batteries do require pressure vessels, so you'd want to consider the ISRU manufacturing challenge and/or cargo mass.  But ISRU raw materials would be there.

Saltwater batteries (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048640#msg2048640) and iron flow batteries (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2306664#msg2306664) don't require pressure vessels, so that's an advantage.  Long life is important, yes, but ease of electrolyte manufacture and replacement is probably more important in Martian context, where process simplification is usually desirable.  Saltwater batteries might win out at present, in that respect.

Image:  Sterz et al. 1997 Fig. 4.  "Cutaway view of Single Pressure [NiH2] Vessel Battery."

Refs.

Sterz S, Parmley B, Caldwell D, Bennett J. Nickel-hydrogen (NiH2) Single Pressure Vessel (SPV) battery development update. (https://core.ac.uk/download/pdf/42768877.pdf#page=741) In IECEC-97 Proceedings of the Thirty-Second Intersociety Energy Conversion Engineering Conference (Cat. No. 97CH6203) 1997 Jul 27 (Vol. 1, pp. 140-143). IEEE.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/09/2021 05:06 pm
I had not really thought about flow batteries, they might be a good fit for Mars depending on the characteristics of the liquids/gasses involved. I know there are some huge Vanadium flow batteries used as multiday backup power for things like semiconductor plants where loss of power is *very* expensive. Not a Chemical Enginger but as I recall the advantage of Vanadium was bouncing between two valance states makes cross contamination of reagents much less of an issue on regeneration. What might be doable with Mars abundant materials? Worth some thought since the backup duration primarily scales by the size of the storage tanks. I will look into Iron flow batteries, thanks!

Edit - it looks like Iron flow batteries can use the same trick as Vanadium to negate cross contamination problems. A quick Google searches turned up ESS Corp which makes them and claims no degradation after 20000 cycles. Pick your size block of salt when dealing with vendor literature claims of course.  ::)
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/09/2021 05:17 pm
Anything with moving parts is subject to wearing out eventually. Batteries suffer from analogous problems with finite charge cycles. So, local production of replacement machinery/parts, batteries/chemicals will be needed long term on Mars.

Some machines are less prone to wear than others, free piston Stirling comes to mind and some batteries last longer than others, Nickle Hydrogen (not NiMH) was used in satellites for that reason. The trade offs for use on Mars will probably be biased toward long life and reliability relative to Earth.

Of course without more info on what resources will be practically available on Mars it is hard to do more than speculate. Back to geology, prospecting, feed stocks and chemical plants I guess  ;)
Modern lithium chemistry batteries are just as good as NiMH btw. Can operate for 10,000 cycles if you want.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/09/2021 06:19 pm
Anything with moving parts is subject to wearing out eventually. Batteries suffer from analogous problems with finite charge cycles. So, local production of replacement machinery/parts, batteries/chemicals will be needed long term on Mars.

Some machines are less prone to wear than others, free piston Stirling comes to mind and some batteries last longer than others, Nickle Hydrogen (not NiMH) was used in satellites for that reason. The trade offs for use on Mars will probably be biased toward long life and reliability relative to Earth.

Of course without more info on what resources will be practically available on Mars it is hard to do more than speculate. Back to geology, prospecting, feed stocks and chemical plants I guess  ;)
Modern lithium chemistry batteries are just as good as NiMH btw. Can operate for 10,000 cycles if you want.

Yes, I love Lithium Iron Phosphate and kin for the high C rate alone. Batteries you can probably weld with and not catch fire/explode.

For static backup applications though, weight and energy density are not as important as they are for mobile and vehicular use so I expect other traits such as cost, simplicity and scalability to predominate. If they want to be able to run the whole Mars complex on stored power for days or weeks in a pinch, that's a lot of storage.
Title: Re: Power options for a Mars settlement
Post by: tenkendojo on 11/09/2021 06:44 pm
I think one potentially promising yet overlooked power and grid energy storage option for Mars settlements would be the solar thermal potion.

Power generation would be done with a solar power tower and a field of non-rigid whirling-membrane heliostats, and grid energy storage would be handled by molten salt. The overall setup would not be too different from the NREL design shown below, although with a few key modifications (e.g. mirror and tower design) to adapt to Martian conditions:


There are many unique advantages to this approach. First, its energy storage medium, salt (typically a mixture of saltpeter, sodium nitrate, and potassium nitrate), not only has excellent heat capacity but is quite abundant on Mars. See this 2019 paper, discussing how Mars Science Laboratory found nitrate deposits at Gale Crater on Mars at levels of 70 to 1100 ppm. These levels are close to nitrate levels measured in the sediments of the Atacama Desert on Earth, which is known for its rich nitrate deposits: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958444/ (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958444/) Mining nitrates on Mars would be necessary for agricultural purposes anyway, so they could serve as a simple and highly scalable thermal energy storage option on Mars without issues from battery charge cycles and rare-earth metals.

Secondly, as solar thermal power only requires very simple reflective surfaces, we could construct large fields of heliostats with extremely lightweight and easily packed materials. I'm thinking along the lines of ~0.01mm thick aluminized polyethylene terephthalate plastic membrane stretched over a lightweight frame to form a parabolic mirror, similar to the NASA solar-energy concentrator design shown here:
https://ntrs.nasa.gov/citations/19680012789 (https://ntrs.nasa.gov/citations/19680012789)
[Edit: I forgot to mention, the mounting frames of reflective membrane heliostats would articulate to track the sun. The flexible thin membrane surface would allow for a simple dust mitigation strategy: as Martian atmospheric dust particles are extremely fine, we could install specialized vibrators as a part of the sun-tracking articulation mechanism undeath the flexible reflective membranes, and they would periodically vibrate and dust off the thin membrane. Periodically we could deploy Ingenuity like drones for more extensive deep cleaning. Also keep in mind that unlike photovoltaic cells, aluminized polyethylene membranes can be cheaply and easily replaced.]

Finally, the solar power tower designs currently in-use on Earth are heavy bulky, like the one we often see in the Mojave Desert: (https://upload.wikimedia.org/wikipedia/commons/b/b6/Solar_two.jpg). For Mars, the power tower would have to be made much lighter, more compact and readily deployable. Note that molten salt tanks for power storage are on the ground, the tower merely reheats the salt. I think cable-stayed tower designs similar to this concept from the 2016 AIP Conference would be ideal for Mars settlements, see image at the bottom:

[/b] (source of the diagram: https://www.nrel.gov/docs/fy13osti/57625.pdf (https://www.nrel.gov/docs/fy13osti/57625.pdf))
(source of the lightweight solar power tower design diagram: https://aip.scitation.org/doi/pdf/10.1063/1.4949172#:~:text=All%20solar%20tower%20structures%20have,requirements%20of%20the%20tower%20structure (https://aip.scitation.org/doi/pdf/10.1063/1.4949172#:~:text=All%20solar%20tower%20structures%20have,requirements%20of%20the%20tower%20structure).)
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/09/2021 06:58 pm
It has been discussed. The problem seems to be that scattered light (from dust) still works for solar panels with reduced efficiency, but it totally wrecks the efficiency of parabolic reflectors expecting light to come directly from the sun. Existing plants on Earth are located in places with mostly clear skys. Think about a month long Mars dust storm. Yikes!
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/09/2021 07:21 pm
I think one potentially promising yet overlooked power and grid energy storage option for Mars settlements would be the solar thermal potion.

Power generation would be done with a solar power tower and a field of non-rigid whirling-membrane heliostats, and grid energy storage would be handled by molten salt. The overall setup would not be too different from the NREL design shown below, although with a few key modifications (e.g. mirror and tower design) to adapt to Martian conditions:


There are many unique advantages to this approach. First, its energy storage medium, salt (typically a mixture of saltpeter, sodium nitrate, and potassium nitrate), not only has excellent heat capacity but is quite abundant on Mars. See this 2019 paper, discussing how Mars Science Laboratory found nitrate deposits at Gale Crater on Mars at levels of 70 to 1100 ppm. These levels are close to nitrate levels measured in the sediments of the Atacama Desert on Earth, which is known for its rich nitrate deposits: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958444/ (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958444/) Mining nitrates on Mars would be necessary for agricultural purposes anyway, so they could serve as a simple and highly scalable thermal energy storage option on Mars without issues from battery charge cycles and rare-earth metals.

Secondly, as solar thermal power only requires very simple reflective surfaces, we could construct large fields of heliostats with extremely lightweight and easily packed materials. I'm thinking along the lines of ~0.01mm thick aluminized polyethylene terephthalate plastic membrane stretched over a lightweight frame to form a parabolic mirror, similar to the NASA solar-energy concentrator design shown here: https://ntrs.nasa.gov/citations/19680012789 (https://ntrs.nasa.gov/citations/19680012789)

Finally, the solar power tower designs currently in-use on Earth are heavy bulky, like the one we often see in the Mojave Desert: (https://upload.wikimedia.org/wikipedia/commons/b/b6/Solar_two.jpg). For Mars, the power tower would have to be made much lighter, more compact and readily deployable. Note that molten salt tanks for power storage are on the ground, the tower merely reheats the salt. I think cable-stayed tower designs similar to this concept from the 2016 AIP Conference would be ideal for Mars settlements, see image at the bottom:

 (source of the diagram: https://www.nrel.gov/docs/fy13osti/57625.pdf (https://www.nrel.gov/docs/fy13osti/57625.pdf))
(source of the lightweight solar power tower design diagram: https://aip.scitation.org/doi/pdf/10.1063/1.4949172#:~:text=All%20solar%20tower%20structures%20have,requirements%20of%20the%20tower%20structure (https://aip.scitation.org/doi/pdf/10.1063/1.4949172#:~:text=All%20solar%20tower%20structures%20have,requirements%20of%20the%20tower%20structure).)

There might be a simplification by using flat reflectors instead of parabolic. The reflectors at the thermal plant in the Mohave look flat but it's hard to tell for sure from the highway. Given a target size and the distance to a mirror, a flat mirror size that will not slop power off target can be calculated.


JohnSmithxxx (I forget the number attached to his handle) brought up the idea of salt storage a long time ago in this thread. He said something about salt in beer cans of all things, buried in a pit, and claimed it had been done. I consider him a high quality info source.


I question aluminum beer cans but following the idea, steam from the tower flows into the salt bunker, then to the turbines. After dark, the tower is cut out of the loop to avoid unnecessary cooling of the working fluid. This avoids the problems associated with molten salt. It might cut energy density but that sounds like a good trade for an early infrastructure.
Title: Re: Power options for a Mars settlement
Post by: tenkendojo on 11/09/2021 07:33 pm
It has been discussed. The problem seems to be that scattered light (from dust) still works for solar panels with reduced efficiency, but it totally wrecks the efficiency of parabolic reflectors expecting light to come directly from the sun. Existing plants on Earth are located in places with mostly clear skys. Think about a month long Mars dust storm. Yikes!

Good point.  I forgot to mention in my op, that I'm thinking that the mounting frames of the membrane heliostats would articulate to track the sun, and the flexible and thin membrane surface would allow for a simple dust mitigation strategy: As Martian atmospheric dust particles are extremely fine, we could install specialized vibrators as a part of the sun-tracking articulation mechanism undeath the reflective membranes, and they would periodically vibrate to keep the membranes relatively clean (would be fun to try to build a prototype of this contraption and see how well it works). From time to time we could deploy Ingenuity-like drones for more extensive deep cleaning too, so I don't see that as a deal-breaking issue. Also keep in mind that unlike photovoltaic cells, aluminized polyethylene membranes can be cheaply and easily replaced or patched.
Title: Re: Power options for a Mars settlement
Post by: yakman2020 on 11/09/2021 07:42 pm
In principle a good idea, but the attempts to do those on earth have had trouble with availability, esp due to unexpected corrosion problems in the heat transfer loop.

It turns out high temperature salts and plumbing to not mix very well.   Not a squelch, but it would be a very good idea to see why these have had trouble and address the issues. Much more is at stake in this case.

https://www.greentechmedia.com/articles/read/americas-concentrated-solar-power-companies-have-all-but-disappeared
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/09/2021 09:48 pm
I had not really thought about flow batteries, they might be a good fit for Mars depending on the characteristics of the liquids/gasses involved. I know there are some huge Vanadium flow batteries used as multiday backup power for things like semiconductor plants where loss of power is *very* expensive. Not a Chemical Enginger but as I recall the advantage of Vanadium was bouncing between two valance states makes cross contamination of reagents much less of an issue on regeneration. What might be doable with Mars abundant materials? Worth some thought since the backup duration primarily scales by the size of the storage tanks. I will look into Iron flow batteries, thanks!

Edit - it looks like Iron flow batteries can use the same trick as Vanadium to negate cross contamination problems. A quick Google searches turned up ESS Corp which makes them and claims no degradation after 20000 cycles. Pick your size block of salt when dealing with vendor literature claims of course.  ::)

Yes, iron flow batteries could be a fit.  The iron chloride chemistry would likely require a smelter and a salt harvester system.

Vanadium flow batteries are also conceivable.  Vanadium would be concentrated in meteoric chromite deposits, e.g., in sand dunes.  A refinery (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2026311#msg2026311) would be required there.

Alternately, salt water batteries could be used:  typically that electrolyte would require only a salt harvester system, so production is simpler.  I liked the achievable low cargo mass (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) of salt water batteries, but with a bit of industry and field prep, that mass might be lowered further.  Rationale:  Much of that notional cargo is Airloy battery casing, to manage Martian outdoor conditions.  But you might prepare a protected, unpressurized facility beforehand, to house batteries constructed from less durable material.  Conceivably, the facility might feature insulated, heated ETFE canopy layers, framed over some hard, perhaps sintered, surface.  In that case, [pun] batteries could use some ISRU plastic, manufactured directly from CO2 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2301269#msg2301269).

Result:  Illustrative battery cargo for 1.4 GWh could be reduced from prior conceivable ~ 1300 tons down to some few hundreds of tons. 
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/09/2021 10:07 pm
What’s the round trip efficiency, though? I heard iron flow is pretty bad. Not much better than just round trip hydrogen fuel cell.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/10/2021 09:09 am
It has been discussed. The problem seems to be that scattered light (from dust) still works for solar panels with reduced efficiency, but it totally wrecks the efficiency of parabolic reflectors expecting light to come directly from the sun.
I forgot to mention in my op, that I'm thinking that the mounting frames of the membrane heliostats would articulate to track the sun, and the flexible and thin membrane surface would allow for a simple dust mitigation strategy: As Martian atmospheric dust particles are extremely fine, we could install specialized vibrators as a part of the sun-tracking articulation mechanism undeath the reflective membranes, and they would periodically vibrate to keep the membranes relatively clean

You missed Okie_Steve's point. The issue isn't the dust settling on the mirrors, it's the dust up in the atmosphere scattering sunlight, preventing it from being reflected onto a collector. Scattered light can still be used by solar PV (and by plant leaves), but can't be concentrated by mirrors.

Note that this is in addition to the total reduction in sunlight reaching the ground. This is just the scattering of the light that does reach the ground.

In practice, even during the clear season, with low opacity, you still lose around 40-50% of direct insolation (ie, solar PV will have twice as much light available as solar-thermal.) During the higher opacity season, you typically lose over 80% of direct insolation. Even short of an actual dust storm, direct insolation can easily drop to 1% of the total sunlight reaching the ground (ie, solar PV will have 100 times as much light available as solar-thermal.)

A few pages back, I linked to a couple of papers covering this. But I'll attach a simple chart with a summary of some actual figures from Viking 1. Note that when dust reduces the total light reaching the ground by a third of the maximum (308 W/m2 to 95 W/m2) but the amount of direct insolation dropped to, effectively, nothing. Solar-thermal (or any solar concentrator) is disproportionately affected by atmospheric dust.



OTV Booster,
This also affects flat mirrors. Only a narrow part of the sky can be "seen" by the tower's collector in each mirror. During clear conditions, you can line up the mirror so the sun is in that narrow sliver of sky, repeated in each mirror. But during dusty conditions, even that brightest part of the sky still doesn't contain a high percentage of sunlight.

(If that explanation doesn't make sense, let me know and I'll try to sketch something more visual.)
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 11/10/2021 11:30 am
On a clear day on Earth, the blue sky delivers maybe 10% of the light and the sun delivers the other 90%. On Mars, it's more like 50/50 as you can see in the figures. A Martian child would struggle to set fire to things with a magnifying glass.

Basically, you could look at the sun on Mars and you'd be less likely to scorch your retina because it appears less bright. It'd be like looking at the sun through a haze or ground fog depending on the opacity. The rest of the sky would appear very bright. Simple forward scattering of the beam of light arriving from the sun, with some being blocked. Though I think the brightness of the sky would differ quite a bit depending on the direction you look, more so than Earth because of the dominance of Mie scattering over Rayleigh (I can never remember which is which).

Though to humans there might not be so much of a difference because our eyes have a very high dynamic range.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/10/2021 01:33 pm
Even short of an actual dust storm, direct insolation can easily drop to 1% of the total sunlight reaching the ground (ie, solar PV will have 100 times as much light available as solar-thermal.)...

No, 1% ratio at the Viking 1 site occurred in a typical late winter storm.  Note the solar longitude (https://www.planetary.org/articles/mars-calendar).

And Martian diffuse light gives very little PV power, as we saw with Opportunity.  When transmission dropped 84%, PV power dropped 83%.  1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2055617#msg2055617) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644)

We should note relevant power data and calculations in thread.

Image (https://www.lpi.usra.edu/publications/slidesets/redplanet2/slide_29.html):  "Dust Storm at Viking 1 Landing Site (22°N,48°W)."  NASA.  Image processing by Mary A. Dale-Bannister.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/10/2021 02:30 pm
Even short of an actual dust storm, direct insolation can easily drop to 1% of the total sunlight reaching the ground (ie, solar PV will have 100 times as much light available as solar-thermal.)...

No, 1% ratio at the Viking 1 site occurred in a typical late winter storm.  Note the solar longitude (https://www.planetary.org/articles/mars-calendar).

And Martian diffuse light gives very little PV power, as we saw with Opportunity.  When transmission dropped 84%, PV power dropped 83%.  1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2055617#msg2055617) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644)

We should note relevant power data and calculations in thread.

Image (https://www.lpi.usra.edu/publications/slidesets/redplanet2/slide_29.html):  "Dust Storm at Viking 1 Landing Site (22°N,48°W)."  NASA.  Image processing by Mary A. Dale-Bannister.
What would be good is if we could agree in this thread on a nice and simple statement, something like : based on the available data, the solar power available during the worst case solar storm to solar cells, including the effect of likely dust accumulation, is xx% of the design power.  This period of low power is likely to last yy hours. 
This is demonstrated by zz references.
An added caveat describing likely dust accumulation and the effect of dust removal would be nice.  after all, this is for a settlement, so there are people to interact with the panels.

Then latitude effects can be added in, depending on base location, and we can design around that?
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/10/2021 03:48 pm
1% ratio at the Viking 1 site occurred in a typical late winter storm.  Note the solar longitude (https://www.planetary.org/articles/mars-calendar).

And Martian diffuse light gives very little PV power, as we saw with Opportunity.  When transmission dropped 84%, PV power dropped 83%.  1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2055617#msg2055617) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644)

We should note relevant power data and calculations in thread.

What would be good is if we could agree in this thread on a nice and simple statement, something like : based on the available data, the solar power available during the worst case solar storm to solar cells, including the effect of likely dust accumulation, is xx% of the design power.  This period of low power is likely to last yy hours. 
This is demonstrated by zz references.
An added caveat describing likely dust accumulation and the effect of dust removal would be nice.  after all, this is for a settlement, so there are people to interact with the panels.

Then latitude effects can be added in, depending on base location, and we can design around that?

Start with Applebaum et al. 1993, noted previously in this thread (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048857#msg2048857).  That's data for transmission and diffusion by latitude, longitude, and season.

As for dust, you can ballpark its effect from Edmondson et al. 2007, as in the post above (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2308837#msg2308837).  There, even at tau 4.7 (0.9% transmission), PV power tracks transmission closely.  This occurs as "dust removal is observed at the beginning of the major Martian dust storm."  That's the (relatively) clean-panel case.  Later, as dust accumulated, dust "never reduced the array performance by more than 40%."  Fig. 2.

--

Don't overlook storm power harvest.  A collector (https://forum.nasaspaceflight.com/index.php?topic=46533.msg2201831#msg2201831) would be a useful addition to a PV panel, giving extra kW when most needed.  Baumgaertner 2016, Melnik and Parrot 1998.

--

Refs.

Appelbatim, I. and Landis, G.A., 1993. Solar Radiation on Mars: Stationary Photovoltaic Array. (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010257.pdf)

Baumgaertner, A. (2016). Power to Mars. (https://www.academia.edu/21777942/Power_to_Mars)

Edmondson, K.M., Fetzer, C., Karam, N.H., Stella, P., Mardesich, N. and Mueller, R., 2007. Multijunction solar cells optimized for the Mars surface solar spectrum. (https://trs.jpl.nasa.gov/bitstream/handle/2014/40575/07-3234.pdf?sequence=1&isAllowed=y)

Melnik O, Parrot M. Electrostatic discharge in Martian dust storms. (https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98JA01954) Journal of Geophysical Research: Space Physics. 1998 Dec 1;103(A12):29107-17.
Title: Re: Power options for a Mars settlement
Post by: tenkendojo on 11/10/2021 04:10 pm
It has been discussed. The problem seems to be that scattered light (from dust) still works for solar panels with reduced efficiency, but it totally wrecks the efficiency of parabolic reflectors expecting light to come directly from the sun.
I forgot to mention in my op, that I'm thinking that the mounting frames of the membrane heliostats would articulate to track the sun, and the flexible and thin membrane surface would allow for a simple dust mitigation strategy: As Martian atmospheric dust particles are extremely fine, we could install specialized vibrators as a part of the sun-tracking articulation mechanism undeath the reflective membranes, and they would periodically vibrate to keep the membranes relatively clean

You missed Okie_Steve's point. The issue isn't the dust settling on the mirrors, it's the dust-up in the atmosphere scattering sunlight, preventing it from being reflected onto a collector. Scattered light can still be used by solar PV (and by plant leaves), but can't be concentrated by mirrors.

Thank you for the clarification.

Data from Viking 1 seem to suggest significant seasonal variance in terms of insolation on Mars surface (see attached chart from the 1989 NASA study below), and I suspect the condition also varies depending on the site's location. See the 2nd set of charts below from a 1991 study comparing the percentage of diffuse insolation on a horizontal surface on Mars between Viking 1 and Viking 2 landing sites.

I will have to look more into solar radiation data on Mars across different geographical regions and seasons to get a better sense of optimal setup and efficiency of solar thermal power on Mars, I know the efficiency will be much lower than Earth of course, but at least this 2001 paper from the AIP Conference indicates that with sufficient concentrator area, solar thermal can be still viable on Mars even under adverse atmospheric conditions, see Table 6 and 7 below): https://doi.org/10.1063/1.1357910

The bottom line though: it doesn't necessarily have to be solar thermal per se, but I do believe in the long run, thermal energy generation and storage are far more viable for sustaining Mars settlements rather than relying on PV.  It all boils down to this very basic economic question: What's the absolute minimum energy required to sustain a person's life on Mars? Considering the increased needs for heating, radiation shielding, maintaining a pressurized environment, ISRU, and so on, the per-capita minimum energy requirement on Mars would be much higher than that of Earth. Turbine generators run as efficiently on Mars as they do on Earth, but PV's do not. Admittedly solar thermal power also relies on the handicapped sunlight for its heat source, but at least it could be easily scaled up on Mars, much of it using locally available materials. The heat byproduct of thermal power itself too is invaluable for Mars settlement, proving a convenient heating source for habitats and agriculture. Molten salt energy storage too can be scaled up on Mars w/o excessively relying on regular and prohibitively expensive Earth shipments.

[Source of the Fig.16 Viking 1 insolation charts: https://ntrs.nasa.gov/api/citations/19890018252/downloads/19890018252.pdf]

[Source of Fig.9 charts: Applebaum et.al., "Solar radiation on Mars—Update 1991" https://www.sciencedirect.com/science/article/pii/0038092X9390006A]

[Source for Tables 6 & 7: Abbott, "Multiuse solar thermal power" https://aip.scitation.org/doi/pdf/10.1063/1.1357910]
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/10/2021 04:46 pm
[...]

In your last table you attached, you correlate the horizontal-plate total insolation with the amount available to concentrated solar-thermal. But you seem to miss the point of the Viking charts you attached, that total insolation is not available to concentrators, only the direct beam insolation. You have to reduce the 162 W/m2 by about 90%, and the 88 W/m2 by over 99%.

The reflector area requirements for thermal power during dusty conditions don't increase by a mere three-fold, as in that chart, they increase by more than two orders of magnitude.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/10/2021 05:20 pm
What would be good is if we could agree in this thread on a nice and simple statement, something like : based on the available data, the solar power available during the worst case solar storm to solar cells, including the effect of likely dust accumulation, is xx% of the design power.  This period of low power is likely to last yy hours. This is demonstrated by zz references.

The two papers I linked to earlier gives you the figures you need. It's just (just!) a matter of converting them to the form you want.

It gives you time-of-year vs Tau vs total insolation. The Viking paper even gives you top-of-the-atmosphere W/m2, giving you a theoretical Tau=0 figure to contrast with the surface figures. That lets you separate the effects of time-of-year (angle of sun + distance of orbit) from opacity (dust levels.) I think that's the missing link you are asking for.

And the charts (see below) in the introduction of LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

So for PV, you can ignore the ratio of direct/indirect insolation and just focus on total insolation. (Obviously that doesn't apply to concentrators.)

A quiet weekend and a bit of spreadsheeting, and you should be able to convert any given Tau to PV W/m2 output. Then you can work out your peak and worst-case scenarios.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/10/2021 09:23 pm
And the charts (see below) in the introduction of LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

So for PV, you can ignore the ratio of direct/indirect insolation and just focus on total insolation.

That's another story without calculation; it can't explain the 2007 Opportunity power crisis (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2055617#msg2055617), as Paul451 knows.  That's a red flag.

It's easy to see that power tracked transmission, not direct+indirect insolation.  Transmission drop (increasing tau)  (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644)matched Fig. 1 current closely, especially at the start of the storm, when panels were relatively clean.  That explains the crisis, quantitatively.

Quote from: Edmondson et al. 2007
Fig. 1 depicts the overall power performance...  [T]he rapid decrease in array performance [is] due to the atmospheric opacity increase from high dust content (increased tau).

Refs.

Edmondson, K.M., Fetzer, C., Karam, N.H., Stella, P., Mardesich, N. and Mueller, R., 2007. Multijunction solar cells optimized for the Mars surface solar spectrum. (https://trs.jpl.nasa.gov/bitstream/handle/2014/40575/07-3234.pdf?sequence=1&isAllowed=y)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/11/2021 04:28 am
So for PV, you can ignore the ratio of direct/indirect insolation and just focus on total insolation. (Obviously that doesn't apply to concentrators.)

This.

This becomes super duper obvious when you look at the data from right before Opportunity died. The tau was ~10.8. If solar power output scaled with direct insolation, we would expect a power output of 0.02 watt-hours per sol. What we actually observed was 22 watt-hours per sol, which is "off" over three orders of magnitude.

Akin's fifth law: Three points determine a curve. (https://spacecraft.ssl.umd.edu/akins_laws.html)
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/11/2021 05:40 am
So for PV, you can ignore the ratio of direct/indirect insolation and just focus on total insolation. (Obviously that doesn't apply to concentrators.)

This.

This becomes super duper obvious when you look at the data from right before Opportunity died. The tau was ~10.8. If solar power output scaled with direct insolation, we would expect a power output of 0.02 watt-hours per sol. What we actually observed was 22 watt-hours per sol, which is "off" over three orders of magnitude.

No, the rover reported (https://mrii.org/from-data-to-storytelling-that-resonates/) that its battery held just 22 Watt-hours of energy when tau hit 10.8.  The tiny transmitted flux couldn't recharge the battery, so the rover failed.  That's consistent with above.

You and Paul451 have posted some odd and false power stories, while ignoring relevant facts and calcs.  You should revisit the 2007 Opportunity power crisis, together, and try to understand it quantitatively -- even noting and applying the actual text of the reference literature, this time.  You'll need to correct your posts after.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/11/2021 06:18 am
Just realized I forgot my source: https://an.rsl.wustl.edu/merb/merxBrowser/an3.aspx?it=D1&ii=22771

Quote
Opportunity is currently in the midst of a severe dust storm though all subsystems are still operating as expected in RAM mode as of the Sol 5111 UHF pass. Solar array energy is approximately 22 W-hrs, with a measured tau of 10.8. This Tau measurement is the highest ever recorded from a ground station on the planet Mars. Dust factor was previously estimated at 3.27 as of Sol 5108.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/11/2021 06:23 am
Why Mars Rovers Don't Rely Upon Diffuse Light

Quote from: Landis et al. 2004
Figures 5 shows the quantum efficiency of the top GaInP solar cell used in the MER solar arrays, showing that it is primarily responding to the visible and blue spectral range, with a long-wavelength cut-off of about 650 nm [i.e, orange to red].  ...the GaInP cell response is in the spectral region most affected by atmospheric dust.

Refs.

Landis, G., Kerslake, T., Scheiman, D. and Jenkins, P., 2004, November. Mars solar power. (http://cmapspublic3.ihmc.us/rid=1P89FWDQW-1D6FSXV-17DG/Mars%20Solar%20Power%202004.pdf) In 2nd International Energy Conversion Engineering Conference (p. 5555).
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/11/2021 06:44 am
Just realized I forgot my source: https://an.rsl.wustl.edu/merb/merxBrowser/an3.aspx?it=D1&ii=22771

Quote
Opportunity is currently in the midst of a severe dust storm though all subsystems are still operating as expected in RAM mode as of the Sol 5111 UHF pass. Solar array energy is approximately 22 W-hrs, with a measured tau of 10.8. This Tau measurement is the highest ever recorded from a ground station on the planet Mars. Dust factor was previously estimated at 3.27 as of Sol 5108.

The rover wasn't reporting daily energy predictions, and it couldn't report "energy" in the solar array, obviously, only power output, according to current.  But power and current were inferred from tau, so a power or current measurement would have been redundant.  The rover did need to report energy stored in the battery, and that's what it reported.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/11/2021 06:54 am
The rover wasn't reporting daily energy predictions, and it couldn't report "energy" in the solar array, obviously, only power output, according to current.  But power and current were inferred from tau, so a power or current measurement would have been redundant.  The rover did need to report energy stored in the battery, and that's what it reported.

Third-party source for this extremely bizarre interpretation of the (quite unambiguous) phrase "solar array energy?"

It's not that I don't believe you, but.....   actually I take that back, it's absolutely that I don't believe you. And I especially don't believe your word over the (again, quite unambiguous) wording in the Opportunity Analyst's Notebook.


EDIT and no, the tweet about Oppy's "final message" doesn't cut it. See Scott Manley's explanation below:

https://www.youtube.com/watch?v=TS7S8T8vExM#t=296
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/11/2021 07:39 am
This is an interesting and relevant graph, courtesy of Solar Radiation on Mars — Update 1991 (https://ntrs.nasa.gov/api/citations/19910005804/downloads/19910005804.pdf).

The graph shows the horizontal irradiance as a fraction of the top-of-atmosphere horizontal irradiance. On this graph, 0.9 (not 1.0) is the numerical value if the Mars atmosphere were hypothetically completely transparent, because reasons.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/11/2021 01:16 pm
The rover wasn't reporting daily energy predictions, and it couldn't report "energy" in the solar array, obviously, only power output, according to current.  But power and current were inferred from tau, so a power or current measurement would have been redundant.  The rover did need to report energy stored in the battery, and that's what it reported.

Third-party source for this extremely bizarre interpretation of the (quite unambiguous) phrase "solar array energy?"

It's not that I don't believe you, but.....   actually I take that back, it's absolutely that I don't believe you. And I especially don't believe your word over the (again, quite unambiguous) wording in the Opportunity Analyst's Notebook.


EDIT and no, the tweet about Oppy's "final message" doesn't cut it. See Scott Manley's explanation below:

The rover didn't make daily energy predictions.  How could it?  Do you imagine it ran through Martian diurnal, seasonal, lat/lon solar and atmospheric lookup tables, while sitting in the dark?

No, the energy stored -- a number the failing rover could report -- indicated recent array performance.

To know power output directly, you read current, which was of course reported throughout the 2007 power crisis.  The tau relation is clear there.  Why did you and Paul451 ignore it?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/11/2021 01:51 pm
The rover wasn't reporting daily energy predictions, and it couldn't report "energy" in the solar array, obviously, only power output, according to current.  But power and current were inferred from tau, so a power or current measurement would have been redundant.  The rover did need to report energy stored in the battery, and that's what it reported.

Third-party source for this extremely bizarre interpretation of the (quite unambiguous) phrase "solar array energy?"

It's not that I don't believe you, but.....   actually I take that back, it's absolutely that I don't believe you. And I especially don't believe your word over the (again, quite unambiguous) wording in the Opportunity Analyst's Notebook.


EDIT and no, the tweet about Oppy's "final message" doesn't cut it. See Scott Manley's explanation below:

The rover didn't make daily energy predictions.  How could it?  Do you imagine it ran through Martian diurnal, seasonal, lat/lon solar and atmospheric lookup tables, while sitting in the dark?

No, the energy stored -- a number the failing rover could report -- indicated recent array performance.

To know power output directly, you read current, which was of course reported throughout the 2007 power crisis.  The tau relation is clear there.  Why did you and Paul451 ignore it?
What you are saying is just wrong, but you constantly repeat it. The figure of Watt-hours is integrated received power that day, NOT battery state of charge. Quit accusing others of ignoring something which is really just you misinterpreting something clear as day.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/11/2021 02:26 pm
Out of curiosity, does anyone know what was the total storage capacity of the rover batteries in KWh when new and estimated as aged at EOL?

For a known battery chemistry, state of charge can be estimated from the "S"- shaped voltage curve. Differences in voltage over time can be used to infer the amount of energy stored  or added or removed if you allow for round trip efficiency, thermal losses and self discharge. The flat-ish region in the center of the curve can be problematic to estimate with some chemistries because there is very little slope/voltage change to measure. It is desirable in that it makes things nice and stable for the load over the usable range though. However at the two end points the voltage moves quickly and significantly up on overcharge and down on complete discharge making measurements easier.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/11/2021 02:37 pm
The rover didn't make daily energy predictions.  How could it?  Do you imagine it ran through Martian diurnal, seasonal, lat/lon solar and atmospheric lookup tables, while sitting in the dark?

No, the energy stored -- a number the failing rover could report -- indicated recent array performance.

To know power output directly, you read current, which was of course reported throughout the 2007 power crisis.  The tau relation is clear there.  Why did you and Paul451 ignore it?

What you are saying is just wrong, but you constantly repeat it. The figure of Watt-hours is integrated received power that day, NOT battery state of charge. Quit accusing others of ignoring something which is really just you misinterpreting something clear as day.

And of course a failing rover wouldn't waste power continually integrating some tidy numerical energy tally.

For the failing rover, battery charge approximated recent power integration, minus requirements; hence the qualification of "approximately" in the mission text.  NASA needed to know the charge and latest tau, which is why the rover reported those two numbers.

The importance of battery state is obvious.  Why do you think tau was important?  Why did the battery die shortly after tau 10.8?
Title: Re: Power options for a Mars settlement
Post by: eriblo on 11/11/2021 02:49 pm
A quick search gives that they had two batteries with 8 prismatic lithium-ion cells at roughly 10 Ah each. So the maximum capacity would be less than 4 V * 10 Ah * 16 = 640 Wh. According to https://www.space.com/opportunity-mars-rover-long-life.html Opportunity still had about 85% capacity at the end (after 5000 cycles).

Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/11/2021 03:24 pm
I found this blurb on the NASA Mars Exploration Rover page, clearly talking about power production per day/sol. Much of which would be used to operate and drive the rover. They really did not talk much about power storage or the batteries beyond mentioning that they existed.

... Their solar arrays were able to produce about 900 watt-hours of energy per martian day, or sol. Well into the extended mission, efforts to drive Spirit and Opportunity strategically through and toward solar-rich areas is providing up to 410 watt-hours per martian sol.

Title: Re: Power options for a Mars settlement
Post by: ccdengr on 11/11/2021 04:11 pm
NASA needed to know the charge and latest tau, which is why the rover reported those two numbers.
Tau is measured using camera images of the sun and is a science activity.  Towards the end of the Opportunity mission, I'm not sure how well tau was being measured and may have only been grossly estimated from array current measurements.

I'd start with https://www.sciencedirect.com/science/article/pii/S0032063321001768 for a discussion of this.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/11/2021 05:23 pm
NASA needed to know the charge and latest tau, which is why the rover reported those two numbers.

Tau is measured using camera images of the sun and is a science activity.  Towards the end of the Opportunity mission, I'm not sure how well tau was being measured and may have only been grossly estimated from array current measurements.

I'd start with https://www.sciencedirect.com/science/article/pii/S0032063321001768 for a discussion of this.

Well, your reference doesn't imply that change, and the mission team wouldn't want to abandon accuracy for such an important measurement.  (Its importance (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309025#msg2309025) is understood?)  Even at the end, energy was stated as "approximate", but tau was not (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309183#msg2309183).

Power levels were dangerously low previously, in 2007 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2055617#msg2055617), and Lemmon et al. 2015 reported no exception to the camera's tau measurement method during that crisis.

Refs.

Lemmon, M.T., Wolff, M.J., Bell III, J.F., Smith, M.D., Cantor, B.A. and Smith, P.H., 2015. Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. (https://arxiv.org/pdf/1403.4234) Icarus, 251, pp.96-111.
Title: Re: Power options for a Mars settlement
Post by: ccdengr on 11/11/2021 05:36 pm
Even at the end, energy was stated as "approximate", but tau was not.
From https://www.planetary.org/articles/08-mer-update-nasa-focuses-on-recovering-opportunity
Quote
As long as Opportunity is hibernating, there will be no data forthcoming from the surface at Endeavour for Lemmon to use to determine Taus... Even so, the MER team obviously needed a regular read on the dust opacity at Endeavour to move forward and had turned to Cantor. His orbital-model estimates of Tau, derived with Mike Wolff’s Martian-tuned atmosphere model, actually were the only other ‘game in town.’
So at the end the rover itself was not measuring tau.  When you are running really low on power, the last thing you want to do is turn on a science instrument for a nonessential measurement.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/11/2021 06:20 pm
Even at the end, energy was stated as "approximate", but tau was not.
From https://www.planetary.org/articles/08-mer-update-nasa-focuses-on-recovering-opportunity
Quote
As long as Opportunity is hibernating, there will be no data forthcoming from the surface at Endeavour for Lemmon to use to determine Taus... Even so, the MER team obviously needed a regular read on the dust opacity at Endeavour to move forward and had turned to Cantor. His orbital-model estimates of Tau, derived with Mike Wolff’s Martian-tuned atmosphere model, actually were the only other ‘game in town.’

So at the end the rover itself was not measuring tau.  When you are running really low on power, the last thing you want to do is turn on a science instrument for a nonessential measurement.

Your "end" speculation was about the last reports from Opportunity.  Naturally, any subsequent values came not from the rover, but from elsewhere.  Atmospheric modeling is unrelated to your previous post.  You got confused there, ccdengr.

Quote
Team members have not heard from Opportunity since June 10th, when they received a message that the dust in the sky overhead, a Tau as the team calls it, was 10.8, the highest the MER mission or any Mars mission has measured...

A Tau of 10.8 turned day to night at Endeavour and forced the rover to shut down into a survival mode of sleep...

With Opportunity still hunkered down in silence, the only viable estimation of dust in the skies over Endeavour would have to come from orbit...

As long as Opportunity is hibernating, there will be no data forthcoming from the surface...
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/11/2021 06:45 pm
It has been discussed. The problem seems to be that scattered light (from dust) still works for solar panels with reduced efficiency, but it totally wrecks the efficiency of parabolic reflectors expecting light to come directly from the sun.
I forgot to mention in my op, that I'm thinking that the mounting frames of the membrane heliostats would articulate to track the sun, and the flexible and thin membrane surface would allow for a simple dust mitigation strategy: As Martian atmospheric dust particles are extremely fine, we could install specialized vibrators as a part of the sun-tracking articulation mechanism undeath the reflective membranes, and they would periodically vibrate to keep the membranes relatively clean

You missed Okie_Steve's point. The issue isn't the dust settling on the mirrors, it's the dust up in the atmosphere scattering sunlight, preventing it from being reflected onto a collector. Scattered light can still be used by solar PV (and by plant leaves), but can't be concentrated by mirrors.

Note that this is in addition to the total reduction in sunlight reaching the ground. This is just the scattering of the light that does reach the ground.

In practice, even during the clear season, with low opacity, you still lose around 40-50% of direct insolation (ie, solar PV will have twice as much light available as solar-thermal.) During the higher opacity season, you typically lose over 80% of direct insolation. Even short of an actual dust storm, direct insolation can easily drop to 1% of the total sunlight reaching the ground (ie, solar PV will have 100 times as much light available as solar-thermal.)

A few pages back, I linked to a couple of papers covering this. But I'll attach a simple chart with a summary of some actual figures from Viking 1. Note that when dust reduces the total light reaching the ground by a third of the maximum (308 W/m2 to 95 W/m2) but the amount of direct insolation dropped to, effectively, nothing. Solar-thermal (or any solar concentrator) is disproportionately affected by atmospheric dust.



OTV Booster,
This also affects flat mirrors. Only a narrow part of the sky can be "seen" by the tower's collector in each mirror. During clear conditions, you can line up the mirror so the sun is in that narrow sliver of sky, repeated in each mirror. But during dusty conditions, even that brightest part of the sky still doesn't contain a high percentage of sunlight.

(If that explanation doesn't make sense, let me know and I'll try to sketch something more visual.)
Thanks, I get it. I was thinking simple & inefficient vs complex & efficient. Moot point. I didn't remember the falloff of thermal with dust that a following post jogged. Why does Momma Nature have to make it so hard?
Title: Re: Power options for a Mars settlement
Post by: etudiant on 11/11/2021 07:05 pm
Have to believe that nuclear is the least difficult solution, if only because a package can be sent that works from the get go.
Wind or solar are for once the place is up and running, when local construction is possible.

In that context, using 2024 as a cutoff date seems wrong to me, by 2024 we may be setting up depots for a moon landing, but Mars is still far off. A compact reactor by 2030 does not seem an unrealistic goal for the Mars project.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/11/2021 09:33 pm
Have to believe that nuclear is the least difficult solution, if only because a package can be sent that works from the get go.
Wind or solar are for once the place is up and running, when local construction is possible.

In that context, using 2024 as a cutoff date seems wrong to me, by 2024 we may be setting up depots for a moon landing, but Mars is still far off. A compact reactor by 2030 does not seem an unrealistic goal for the Mars project.
It's not the least difficult because it doesn't exist yet :-)  Getting it to exist may be quite difficult .
Solar exists and works.  It just needs careful planning.  And in case of failure can be replaced temporarily by a generator burning oxygen and methane.  Now to be honest that doesn't exist yet either, but my guess, for what it's worth, is that it will be simpler to develop than a nuclear reactor. 

One of the difficulties of the last few pages of this thread seem to be getting the participants here to agree that solar should work even in extreme storms. It seems to be a human problem, and that wont get solved by nuclear power!
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/11/2021 10:34 pm
The rover didn't make daily energy predictions.  How could it?  Do you imagine it ran through Martian diurnal, seasonal, lat/lon solar and atmospheric lookup tables, while sitting in the dark?

No, the energy stored -- a number the failing rover could report -- indicated recent array performance.

To know power output directly, you read current, which was of course reported throughout the 2007 power crisis.  The tau relation is clear there.  Why did you and Paul451 ignore it?

What you are saying is just wrong, but you constantly repeat it. The figure of Watt-hours is integrated received power that day, NOT battery state of charge. Quit accusing others of ignoring something which is really just you misinterpreting something clear as day.

And of course a failing rover wouldn't waste power continually integrating some tidy numerical energy tally.

For the failing rover, battery charge approximated recent power integration, minus requirements; hence the qualification of "approximately" in the mission text.

Wrong again. The difference in battery state-of-charge (plus known electrical consumption) equals the solar array energy, not the total battery state-of-charge. If the Opportunity mission analysts had meant the battery state-of-charge, they would have used the phrase "battery energy" or "stored energy," not "solar array energy." To suggest otherwise is lunacy.

As for the 2007 power crisis, there's nothing to explain. All you've done is cherry-pick two tau values on the direct sunlight curve that (when connected with a straight line) coincidentally have the same slope as the corresponding two points on the total power curve (when connected with a straight line). It's critically important to realize that this is not the same as proving that the two curves are the same.

As Akin reminds us, "three points determines a line." Once we add a third data point (such as tau = 10.8 and P = 22 Wh/sol), your argument completely collapses.

There are a bunch of additional problems with your argument. You ignore huge changes in dust losses over that time period, which is shown in the very next figure in the linked paper. You're also trying to claim to be able to read data-points on Figure 1, but the graph is clearly way too scrunched up between Sol 1220 and Sol 1235 to disentangle exact x-values to within an accuracy of <5 sols. I don't believe that you can discern that type of accuracy from that graph unless I see some better evidence, eg pixel counting. Worst of all, you never actually estimate power using the total horizontal insolation, so your claim that direct insolation is a better proxy than total insolation is totally unsupported since you have no "control group" here.

Anyone got the actual spreadsheet showing the time series of Opportunity's power production? I can't find it online.  :(  Those data would immediately settle this whole tired debate once-and-for-all.
Title: Re: Power options for a Mars settlement
Post by: etudiant on 11/11/2021 11:50 pm
Have to believe that nuclear is the least difficult solution, if only because a package can be sent that works from the get go.
Wind or solar are for once the place is up and running, when local construction is possible.

In that context, using 2024 as a cutoff date seems wrong to me, by 2024 we may be setting up depots for a moon landing, but Mars is still far off. A compact reactor by 2030 does not seem an unrealistic goal for the Mars project.
It's not the least difficult because it doesn't exist yet :-)  Getting it to exist may be quite difficult .
Solar exists and works.  It just needs careful planning.  And in case of failure can be replaced temporarily by a generator burning oxygen and methane.  Now to be honest that doesn't exist yet either, but my guess, for what it's worth, is that it will be simpler to develop than a nuclear reactor. 

One of the difficulties of the last few pages of this thread seem to be getting the participants here to agree that solar should work even in extreme storms. It seems to be a human problem, and that wont get solved by nuclear power!

I disagree that the reactor does not exist as yet, seems to me that modest size submarine reactors are pretty routine.
Weight is the main issue, mostly due to passive shielding that can be eliminated just by siting the reactor remotely.

Solar takes acres of cells to get reasonable power, so mandates a construction project right after getting there. Imho, that is a serious negative.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/11/2021 11:54 pm
modest size submarine reactors are pretty routine.

Good luck sourcing the HEU.

Solar takes acres of cells to get reasonable power

Ditto for nuke's radiator panels.

Small acreage = small power. Large acreage = large power. This is true for both systems.
Title: Re: Power options for a Mars settlement
Post by: Coastal Ron on 11/12/2021 12:14 am
Have to believe that nuclear is the least difficult solution, if only because a package can be sent that works from the get go.
Wind or solar are for once the place is up and running, when local construction is possible.

In that context, using 2024 as a cutoff date seems wrong to me, by 2024 we may be setting up depots for a moon landing, but Mars is still far off. A compact reactor by 2030 does not seem an unrealistic goal for the Mars project.
It's not the least difficult because it doesn't exist yet :-)  Getting it to exist may be quite difficult .
Solar exists and works.  It just needs careful planning.  And in case of failure can be replaced temporarily by a generator burning oxygen and methane.  Now to be honest that doesn't exist yet either, but my guess, for what it's worth, is that it will be simpler to develop than a nuclear reactor. 

One of the difficulties of the last few pages of this thread seem to be getting the participants here to agree that solar should work even in extreme storms. It seems to be a human problem, and that wont get solved by nuclear power!

I disagree that the reactor does not exist as yet, seems to me that modest size submarine reactors are pretty routine.
Weight is the main issue, mostly due to passive shielding that can be eliminated just by siting the reactor remotely.

Um, you do realize that nuclear reactors on submarines rely on a LOT of seawater to cool them? Where are you going to get that volume of water on Mars?

Quote
Solar takes acres of cells to get reasonable power, so mandates a construction project right after getting there. Imho, that is a serious negative.

The entire colonization effort is a construction project, from Day One. The thing about solar panels is that they do NOT cause potential problems like releasing radiation when they fail, and other than keeping dust off of them they require no maintenance.

And sure, solar panels on Mars won't have the same collection ability as here on Earth, but the power they provide, day to day, may make a difference to an initial colony.
Title: Re: Power options for a Mars settlement
Post by: ccdengr on 11/12/2021 12:20 am
Anyone got the actual spreadsheet showing the time series of Opportunity's power production?
As of 2014, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6350794/
Quote
The solar array data is not generally available, although a normalized dataset for year 1 was published in image form... Solar array performance information from Mars missions should be made available in a public archive since it provides important information on the Mars environment.

If it's been released since, I haven't seen it.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/12/2021 12:50 am
Have to believe that nuclear is the least difficult solution, if only because a package can be sent that works from the get go.
Wind or solar are for once the place is up and running, when local construction is possible.


This isn’t true. Nuclear typically needs to be buried due to radiation. Surface side has a radiator that needs deploying, like solar panels.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/12/2021 01:21 am
Have to believe that nuclear is the least difficult solution, if only because a package can be sent that works from the get go.
Wind or solar are for once the place is up and running, when local construction is possible.


This isn’t true. Nuclear typically needs to be buried due to radiation. Surface side has a radiator that needs deploying, like solar panels.
And there's no reactor available that is specifically designed for use on Mars (rather than in a salt water ocean) and problems with getting hold of HIU and political problems with launching anything to do with a nuclear reactor on a rocket (regardless of the arguments). But apart from all that it would be much better than solar.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/12/2021 04:05 am
As Akin reminds us, "three points determines a line." Once we add a third data point (such as tau = 10.8 and P = 22 Wh/sol), your argument completely collapses...

There's no record of energy from tau 10.8 onward, because the rover failed there.  It wasn't much, obviously.

Anyone got the actual spreadsheet showing the time series of Opportunity's power production? I can't find it online.  :( 

Opportunity reported current (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2055617#msg2055617). 

--

The reason rovers couldn't pull much power from diffuse storm light was known and documented 17 years ago (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).  Why all the "drama" around a question already answered, as noted in thread?  A useful and undramatic discussion might explore potential methods to boost solar cell storm performance. 
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/12/2021 05:39 am
One of the difficulties of the last few pages of this thread seem to be getting the participants here to agree that solar should work even in extreme storms.

Do you understand why it works so poorly in storms today (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185)?  And do you have ideas for improvement?

Solar... can be replaced temporarily by a generator burning oxygen and methane.

Why saddle a settlement with such terribly inefficient energy conversion?  ISRU salt water battery farms could plausibly give efficient power at any required settlement scale, and with extremely low cargo mass (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2308622#msg2308622).  Bulk methalox and turbine system cargo mass, and the associated end-to-end efficiency, have little room for improvement, whereas salt water batteries might leverage additional ISRU and industry in ways yet to be determined, for even greater metrics.  That's worth some thought, if you're looking for efficient solutions to settlement power problems that can't be solved by PV alone.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/12/2021 01:13 pm
One of the difficulties of the last few pages of this thread seem to be getting the participants here to agree that solar should work even in extreme storms.

Do you understand why it works so poorly in storms today (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185)?  And do you have ideas for improvement?

Solar... can be replaced temporarily by a generator burning oxygen and methane.

Why saddle a settlement with such terribly inefficient energy conversion?  ISRU salt water battery farms could plausibly give efficient power at any required settlement scale, and with extremely low cargo mass (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2308622#msg2308622).  Bulk methalox and turbine system cargo mass, and the associated end-to-end efficiency, have little room for improvement, whereas salt water batteries might leverage additional ISRU and industry in ways yet to be determined, for even greater metrics.  That's worth some thought, if you're looking for efficient solutions to settlement power problems that can't be solved by PV alone.
Both of your links are to your own previous posts.
Title: Re: Power options for a Mars settlement
Post by: Genial Precis on 11/12/2021 01:16 pm
I think there's an implicit, perhaps unrecognized assumption in the preceeding comparisons of solar and nuclear power, that the site selection would be the same. Which might be true, or might not.

At an equatorial site one could expect solar PV to provide an average power density of 30-40 W/m^2 during summer and whatever it is during winter, and less during dust storms. A nuclear power plant exhausting heat at 320 K could reliably radiate 300 W/m^2 during summer and 500 W/m^2 during winter, which is a factor of 10 less, so the power density per land footprint advantage would exist, but the preceding still implies substantial radiators.

Using gas cooling, per NIST fluid properties one could expect to dump maybe 50 kJ per kg of CO2 (enthalpy change from 260 K to 320 K) and the average density would be .012 kg/m^3. One could dump 600 J/m^3 into the atmosphere. With a flow rate of 30 m/s, one could achieve 20 kW per m^2 of intake area. Given the sort of heat exchanger required to work with such low density fluid, that doesn't necessarily trade well.

So nuclear power can't be expected perform super well for delivering large amounts of power at an equatorial site that is well-suited to solar PV. However, at an equatorial site water and CO2 are relatively scarce. At a polar site there are solid water and CO2 lying on the ground, which is a significant advantage.

Exhausting heat at 320 K, one could use radiators at 500 W/m^2 all the time, or dump 1200 J/m^3 into the atmosphere, 40 kW/m^2 of intake area with the aforementioned 30 m/s intake speed. Or one could boil water for 2500 kJ/kg. Assuming one can extract water from a depth of up to 100 m and allowing for 20 years of power production yields an average power of 400 W/m^2.

I think the above implies that one could use semi-open system radiators. Imagine rising water vapor lifting a thin radiator film, like a hot air balloon. The vapor condenses and snows back down, to be fed back into the boiler. That sort of system could have good mass trades, maybe.

The above should be taken as thinking out loud. I think I conclude that the critical advantage of a nuclear power system on Mars, if an advantage existed, would be to enable a polar site. Because rather than use lots of large compressors to gather up CO2 and other devices to gather water, both could be excavated from surface mines.
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 11/12/2021 01:27 pm
Mars should use space-based solar power: collectors in and Ares-synchronous orbit delivering microwave power to the ground. The economics of this are much better at Mars than for Earth. It should cost less to deliver panels from Earth to Mars orbit than it does to deliver them to the ground, the panels are in sunlight almost 100% of the time, and there are no dust storms. The ground-based rectenna is lower mass delivered to the surface than panels would be, or alternatively it's a lot easier to manufacture a rectanna locally than is it to manufacture solar panels.  Mass tradeoff is favorable: you need fewer panels because they are lit almost all the time, and this should offset the mass needed for the microwave transmitter in space and the rectanna on the ground.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/12/2021 01:50 pm
I think there's an implicit, perhaps unrecognized assumption in the preceeding comparisons of solar and nuclear power, that the site selection would be the same. Which might be true, or might not.

At an equatorial site one could expect solar PV to provide an average power density of 30-40 W/m^2 during summer and whatever it is during winter, and less during dust storms. A nuclear power plant exhausting heat at 320 K could reliably radiate 300 W/m^2 during summer and 500 W/m^2 during winter, which is a factor of 10 less, so the power density per land footprint advantage would exist, but the preceding still implies substantial radiators.

Using gas cooling, per NIST fluid properties one could expect to dump maybe 50 kJ per kg of CO2 (enthalpy change from 260 K to 320 K) and the average density would be .012 kg/m^3. One could dump 600 J/m^3 into the atmosphere. With a flow rate of 30 m/s, one could achieve 20 kW per m^2 of intake area. Given the sort of heat exchanger required to work with such low density fluid, that doesn't necessarily trade well.

So nuclear power can't be expected perform super well for delivering large amounts of power at an equatorial site that is well-suited to solar PV. However, at an equatorial site water and CO2 are relatively scarce. At a polar site there are solid water and CO2 lying on the ground, which is a significant advantage.

Exhausting heat at 320 K, one could use radiators at 500 W/m^2 all the time, or dump 1200 J/m^3 into the atmosphere, 40 kW/m^2 of intake area with the aforementioned 30 m/s intake speed. Or one could boil water for 2500 kJ/kg. Assuming one can extract water from a depth of up to 100 m and allowing for 20 years of power production yields an average power of 400 W/m^2.

I think the above implies that one could use semi-open system radiators. Imagine rising water vapor lifting a thin radiator film, like a hot air balloon. The vapor condenses and snows back down, to be fed back into the boiler. That sort of system could have good mass trades, maybe.

The above should be taken as thinking out loud. I think I conclude that the critical advantage of a nuclear power system on Mars, if an advantage existed, would be to enable a polar site. Because rather than use lots of large compressors to gather up CO2 and other devices to gather water, both could be excavated from surface mines.
It's an interesting point. When the time comes for the polar exploration of Mars, nuclear will be the prime candidate because above certain latitudes solar will be entirely impractical due to increasingly long periods of winter darkness and the low inclination of the Sun when it does appear.

But I don't think human Martian polar exploration is likely to happen any time soon. I don't believe any high or low latitude sites have ever been suggested as a potential human landing site presumably due to the more difficult terrain and conditions.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/12/2021 01:55 pm
Mars should use space-based solar power: collectors in and Ares-synchronous orbit delivering microwave power to the ground. The economics of this are much better at Mars than for Earth. It should cost less to deliver panels from Earth to Mars orbit than it does to deliver them to the ground, the panels are in sunlight almost 100% of the time, and there are no dust storms. The ground-based rectenna is lower mass delivered to the surface than panels would be, or alternatively it's a lot easier to manufacture a rectanna locally than is it to manufacture solar panels.  Mass tradeoff is favorable: you need fewer panels because they are lit almost all the time, and this should offset the mass needed for the microwave transmitter in space and the rectanna on the ground.
Perhaps, but I suspect the devil is in the details. How much power might be lost between the power sat and the battery on the ground under ideal conditions? And how much might be lost during a dust storm? How transparent are dust storms to microwaves? Has anyone done the calculations?
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/12/2021 02:10 pm
One of the difficulties of the last few pages of this thread seem to be getting the participants here to agree that solar should work even in extreme storms.

Do you understand why it works so poorly in storms today (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185)?  And do you have ideas for improvement?

Solar... can be replaced temporarily by a generator burning oxygen and methane.

Why saddle a settlement with such terribly inefficient energy conversion?  ISRU salt water battery farms could plausibly give efficient power at any required settlement scale, and with extremely low cargo mass (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2308622#msg2308622).  Bulk methalox and turbine system cargo mass, and the associated end-to-end efficiency, have little room for improvement, whereas salt water batteries might leverage additional ISRU and industry in ways yet to be determined, for even greater metrics.  That's worth some thought, if you're looking for efficient solutions to settlement power problems that can't be solved by PV alone.

Both of your links are to your own previous posts.

Because the info is there, only.  You're incurious.

Your settlement LAES CRYOBattery notion (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2306366#msg2306366) also has terrible numbers for cargo mass and end-to-end efficiency.  There's no case for it, when you're aware of the salt water battery farm option.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/12/2021 02:17 pm
Mars should use space-based solar power: collectors in and Ares-synchronous orbit delivering microwave power to the ground. The economics of this are much better at Mars than for Earth. It should cost less to deliver panels from Earth to Mars orbit than it does to deliver them to the ground, the panels are in sunlight almost 100% of the time, and there are no dust storms. The ground-based rectenna is lower mass delivered to the surface than panels would be, or alternatively it's a lot easier to manufacture a rectanna locally than is it to manufacture solar panels.  Mass tradeoff is favorable: you need fewer panels because they are lit almost all the time, and this should offset the mass needed for the microwave transmitter in space and the rectanna on the ground.

Perhaps, but I suspect the devil is in the details. How much power might be lost between the power sat and the battery on the ground under ideal conditions? And how much might be lost during a dust storm? How transparent are dust storms to microwaves? Has anyone done the calculations?

I showed you -- you, personally -- two years ago, in this thread.  What's the issue there?

1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1951903#msg1951903) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508)
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/12/2021 02:51 pm
...the critical advantage of a nuclear power system on Mars, if an advantage existed, would be to enable a polar site.

Not really.  Far easier to deploy a thin SWER UHVDC line from a PV farm at lower latitude:  e.g., add a poleward extension to the illustrative Apollinaris / Phlegra Montes line (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437).

Quote
...a primitive graded roadway... could serve also as path for UHVDC cable, which connects Phlegra Montes to the grid at Apollinaris farm.  This cable could be transported to Phlegra Montes as Starship cargo, part of the facility's power distribution payload.  The cable is simply deployed from truck at roadside.

--

Quote from: Elon Musk (https://twitter.com/PPathole/status/1459021773073051653)
We've got a giant thermonuclear reactor in the sky called the sun. It's great. Shows up every day, very reliable.

So, if you can generate energy from solar panels, store it with batteries, you can have energy 24 hours a day. 

And then you can send it to the poles... with high-voltage lines...

--

Trivia:  I set the longitude of the first illustrative grid PV farm deployment to that of Apollinaris Mons, 174° E.

Reason:  This siting was near-optimal for connecting the big Phlegra Montes glacier to the notional planetary grid.  But more importantly, it placed the grid's tenth PV farm deployment at Bradbury crater.

Hence, the "Bradbury farm".

Quote from: Ray Bradbury
"Whenever a light blinked out, life threw another switch; rooms were illumined afresh." (https://www.theatlantic.com/technology/archive/2012/06/on-bradbury-whenever-a-light-blinked-out-life-threw-another-switch-rooms-were-illumined-afresh/258217/)

Image:  Bradbury crater, perspective view.  Erkeling et al. 2016. 

Refs.

Erkeling, G., Ivanov, M.A., Tirsch, D., Reiss, D., Bishop, J.L., Tornabene, L.L., Hiesinger, H. and Jaumann, R., 2016. Bradbury Crater, Mars: Morphology, Morphometry, Mineralogy, and Chronostratigraphy. (https://www.hou.usra.edu/meetings/lpsc2016/pdf/1451.pdf)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/12/2021 03:12 pm
Mars should use space-based solar power: collectors in and Ares-synchronous orbit delivering microwave power to the ground. The economics of this are much better at Mars than for Earth. It should cost less to deliver panels from Earth to Mars orbit than it does to deliver them to the ground, the panels are in sunlight almost 100% of the time, and there are no dust storms. The ground-based rectenna is lower mass delivered to the surface than panels would be, or alternatively it's a lot easier to manufacture a rectanna locally than is it to manufacture solar panels.  Mass tradeoff is favorable: you need fewer panels because they are lit almost all the time, and this should offset the mass needed for the microwave transmitter in space and the rectanna on the ground.
Here is an excerpt from a study and the study itself, as referred by LMT.

The conclusion seems to be 6.2 MW in orbit provides 100 kW on the ground, or a surprisingly low 1,6% efficiency.
would be interesting to test ground solar efficiency with the same parameters.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/12/2021 03:32 pm
Mars should use space-based solar power: collectors in and Ares-synchronous orbit delivering microwave power to the ground. The economics of this are much better at Mars than for Earth. It should cost less to deliver panels from Earth to Mars orbit than it does to deliver them to the ground, the panels are in sunlight almost 100% of the time, and there are no dust storms. The ground-based rectenna is lower mass delivered to the surface than panels would be, or alternatively it's a lot easier to manufacture a rectanna locally than is it to manufacture solar panels.  Mass tradeoff is favorable: you need fewer panels because they are lit almost all the time, and this should offset the mass needed for the microwave transmitter in space and the rectanna on the ground.

Perhaps, but I suspect the devil is in the details. How much power might be lost between the power sat and the battery on the ground under ideal conditions? And how much might be lost during a dust storm? How transparent are dust storms to microwaves? Has anyone done the calculations?

I showed you -- you, personally -- two years ago, in this thread.  What's the issue there?

1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1951903#msg1951903) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1868508#msg1868508)
So you did! Tanks for the link I had forgotten about that. Seems that the devil is very much in that detail.
Title: Re: Power options for a Mars settlement
Post by: Greg Hullender on 11/12/2021 04:06 pm
It had not occurred to me before that the area needed to radiate away the waste heat from a nuclear reactor could be even 10% of the area needed for solar panels. (Now I wish I hadn't dropped that thermodynamics class at Caltech 40 years ago.) If you don't  mind, I'd like to ask a few questions.
At an equatorial site one could expect solar PV to provide an average power density of 30-40 W/m^2 during summer and whatever it is during winter, and less during dust storms. A nuclear power plant exhausting heat at 320 K could reliably radiate 300 W/m^2 during summer and 500 W/m^2 during winter, which is a factor of 10 less, so the power density per land footprint advantage would exist, but the preceding still implies substantial radiators.

Using gas cooling, per NIST fluid properties one could expect to dump maybe 50 kJ per kg of CO2 (enthalpy change from 260 K to 320 K) and the average density would be .012 kg/m^3. One could dump 600 J/m^3 into the atmosphere. With a flow rate of 30 m/s, one could achieve 20 kW per m^2 of intake area. Given the sort of heat exchanger required to work with such low density fluid, that doesn't necessarily trade well.
Given the big difference in temperature between day and night, shouldn't the radiators work much better at night?

You don't include (that I can tell) anything for conduction through the soil. I know the bare regolith is a pretty good insulator, but I also know that <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JE003938"that changes dramatically with the addition of small amounts of water/ice and even concrete.[/url] Or would conduction only help for a while, up until the ground under the reactor warmed up?

What's the absolute best you could do? I'm visualizing tube-shaped radiators open at the bottom that suck in air from below via natural convection and (maybe) transfer heat down via a concrete base. For (say) a 1 MW reactor, how big would the radiator farm actually have to be?

Exhausting heat at 320 K, one could use radiators at 500 W/m^2 all the time, or dump 1200 J/m^3 into the atmosphere, 40 kW/m^2 of intake area with the aforementioned 30 m/s intake speed. Or one could boil water for 2500 kJ/kg. Assuming one can extract water from a depth of up to 100 m and allowing for 20 years of power production yields an average power of 400 W/m^2.
I found this a little confusing. If you have ready access to ice and/or CO2 ice, shouldn't that give you effectively limitless ability to dispose of waste heat with a fairly small footprint?
Title: Re: Power options for a Mars settlement
Post by: Genial Precis on 11/12/2021 05:09 pm
Given the big difference in temperature between day and night, shouldn't the radiators work much better at night?
In equatorial martian summer, average high (https://en.wikipedia.org/wiki/Climate_of_Mars) is 274 K, average low is 205 K. Winter is 250 K and 186 K respectively. Radiating from 320 K into those temperatures can dissipate 275, 495, 375 or 525 W/m^2 respectively. Radiating from 370 K into those temperatures could dissipate 740, 960, 840 or 1000 W/m^2 respectively, improving power density at the cost of some efficiency.

In reality the thermal radiation environment would be a mix of high altitude air and space, which is somewhat colder than just the air, so performance would be improved by some moderate factor compared to the above.
Quote
You don't include (that I can tell) anything for conduction through the soil. I know the bare regolith is a pretty good insulator, but I also know that <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JE003938"that changes dramatically with the addition of small amounts of water/ice and even concrete.[/url] Or would conduction only help for a while, up until the ground under the reactor warmed up?
Yes, the regolith has not much heat capacity and abysmal thermal conductivity. If you bury something you want to maintain at a certain temperature in 5-10 m of regolith you can ignore seasonal temperature swings, to give you some idea.

So efficient heat transfer to the ground requires fine tendrils going everywhere, and the only place for the ground to dump heat is ~10 m down and once that warms up the rest has to go up, making it a radiator with extra steps. If it's worth doing at all I don't know a good design.

Quote
What's the absolute best you could do? I'm visualizing tube-shaped radiators open at the bottom that suck in air from below via natural convection and (maybe) transfer heat down via a concrete base. For (say) a 1 MW reactor, how big would the radiator farm actually have to be?
The quoted figures for radiators are for dissipating heat only by thermally emitting infrared light, as warm objects do. For the highest power density case above exhausting heat at 370 K, a 1 MWe reactor with an efficiency of 35% would need to dissipate 1.85 MW of heat and require roughly 2000 m^2 of radiators.

However, in reality the atmosphere can sink some heat. Using the 370 K exhaust temperature and the 240 K daily average temperature during equatorial summer, the enthalpy of CO2 (https://webbook.nist.gov/cgi/fluid.cgi?P=.0006&TLow=217&THigh=400&TInc=.5&Applet=on&Digits=5&ID=C124389&Action=Load&Type=IsoBar&TUnit=K&PUnit=MPa&DUnit=kg%2Fm3&HUnit=kJ%2Fkg&WUnit=m%2Fs&VisUnit=Pa*s&STUnit=N%2Fm&RefState=DEF) at 6 kPa goes from 460 kJ/kg at 240 K to 570 kJ/kg at 370 K, a rise of 110 kJ/kg so if I can heat 17 kg/s of CO2 from 240 K to 370 K that is enough to dump the heat. The density of CO2 gas at 240 K is .013 kg/m^3, so I need to feed 1300 m^3/s of atmosphere through the heat exchanger.

For that purpose I can use a chimney or a fan. The fan would probably be much lighter, unless the chimney could be supported by the buoyancy of the exhaust gases like a hot air balloon. I choose a speed of 30 m/s in order to achieve high power density without loosing too much power to the motor driving the fan. The intake area would be 43 m^2, eg a 5.8 m diameter circle.
Quote
I found this a little confusing. If you have ready access to ice and/or CO2 ice, shouldn't that give you effectively limitless ability to dispose of waste heat with a fairly small footprint?
Vaporizing water absorbs more enthalpy per mass than vaporizing CO2, roughly 2.5e6 J/kg. The heat of melting and of temperature changes are small by comparison. The above 1 MWe nuclear power plant could dissipate the heat at, say, 280 K and still boil the water due to low ambient pressure, so let's say its efficiency is 42% somewhat arbitrarily. It would need to dissipate 1.4 MW of heat by boiling 0.55 kg/s of water.

It's not so much. However, if it runs for 20 years it will need 340 kton of water. If you're sitting on an ice sheet, maybe you can get it from almost right next door. If you excavate the ice from a depth of up to 100 m, then you need 3400 m^2 of quarry footprint, which is similar to the footprint of the radiators. Of course if it only has to run for 3 months while you set up other infrastructure, such as radiators, then digging up ice sounds more attractive because you only need 4300 tons of it.

Also, if you exhaust your 280 K boiling water into a balloon of 56 m diameter, that balloon will have 10,000 m^2 of surface area from which to radiate heat and recondense the water. If the balloon were buoyant, then it could have an absolutely tiny mass compared to other radiators with so much surface area. You could pack spares, since the mass would be much lower than other components. If something happens to the balloon, you just exhaust to atmosphere until you can replace it, consuming a bit of water. It seems like it might perhaps be an effective radiator design, in spite of the comedy.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/12/2021 05:51 pm
I found this a little confusing. If you have ready access to ice and/or CO2 ice, shouldn't that give you effectively limitless ability to dispose of waste heat with a fairly small footprint?
[...]
Also, if you exhaust your 280 K boiling water into a balloon of 56 m diameter, that balloon will have 10,000 m^2 of surface area from which to radiate heat and recondense the water.

If you are using thermal energy to melt into an icesheet/glacier, then you are better off exhausting the steam into the pool of water (for example, in a Rodwell-type extraction pit.) Vastly higher rate of heat transfer than gas/gas (via your balloon). And the heat goes where you want to use it, not into the atmosphere.

So instead, use the membrane/balloon skin to cover the pit. At roughly Mars pressure, the vapour pressure (once other gases are forced out) is enough to prevent an unpressurised pool from vacuum-boiling.

Additionally, at just 26m below the surface of the pool, the pressure from the weight of the water equals 1atm. So if you site your habitat in such a pool, you can simplify construction compared to being up on the surface. (As well as having open moon-pools. Just be careful with your dive-weights, you don't want to float to the surface. You can also use the pool as a "waterlock" in place of an airlock to access the surface for EVAs (as discussed in other threads.))

Similarly, water is an excellent radiation shield. Not just against space radiation, but with just a few tens of metres separation from habitats and other equipment, you can house the reactor module directly in the pool.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/12/2021 05:57 pm
There are some limitations to the distance a power line could be run to supply a base.

For example, for a hypothetical MVDC line, providing 6 MW on average to a 100 person early settlement, with a line voltage of 25 kV, the amperage would be 6 000 000W / 25 000V = 240Amps.  This would require 4/0 wire, that might mass about 0,3 kg/m. So for an entire Starship of wire, 100 tonnes, we get 300 km of wire.

The same 100 tonnes as local solar panels at 3 kg/m2 would means 30 000m2 of panels, or about 750 kW of average local power. (3 MW peak, 0.75 MW average)

It would seem to be simpler to just add extra local panels?  Is 300 km far enough to create significant differences in power availability?
The power line would also spend much of it's time idle or at reduced capacity. So that also seems not cost effective.
The same at 250 000 V, so as HVDC, might stretch to 1000 km, bit still that doesn't seem like very far.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/12/2021 07:04 pm
There are some limitations to the distance a power line could be run to supply a base.

For example, for a hypothetical MVDC line, providing 6 MW on average to a 100 person early settlement, with a line voltage of 25 kV, the amperage would be 6 000 000W / 25 000V = 240Amps.  This would require 4/0 wire, that might mass about 0,3 kg/m. So for an entire Starship of wire, 100 tonnes, we get 300 km of wire.

The same 100 tonnes as local solar panels at 3 kg/m2 would means 30 000m2 of panels, or about 750 kW of average local power. (3 MW peak, 0.75 MW average)

It would seem to be simpler to just add extra local panels?  Is 300 km far enough to create significant differences in power availability?
The power line would also spend much of it's time idle or at reduced capacity. So that also seems not cost effective.
The same at 250 000 V, so as HVDC, might stretch to 1000 km, bit still that doesn't seem like very far.

But how could you overlook UHVDC, which is designed for long-haul power?

Using SWER UHVDC with low-temperature Mars min resistance, you'd get much greater coverage, as with the single-payload segments connecting notional grid farms, above (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309792#msg2309792).

You might calculate the number of those 150 t cable payloads needed to connect Phlegra Montes to a facility at 85 N.

And remember, polar sites get no appreciable solar insolation in winter.  Even a gigantic polar PV farm wouldn't help much then.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/12/2021 07:50 pm
There are some limitations to the distance a power line could be run to supply a base.

For example, for a hypothetical MVDC line, providing 6 MW on average to a 100 person early settlement, with a line voltage of 25 kV, the amperage would be 6 000 000W / 25 000V = 240Amps.  This would require 4/0 wire, that might mass about 0,3 kg/m. So for an entire Starship of wire, 100 tonnes, we get 300 km of wire.

The same 100 tonnes as local solar panels at 3 kg/m2 would means 30 000m2 of panels, or about 750 kW of average local power. (3 MW peak, 0.75 MW average)

It would seem to be simpler to just add extra local panels?  Is 300 km far enough to create significant differences in power availability?
The power line would also spend much of it's time idle or at reduced capacity. So that also seems not cost effective.
The same at 250 000 V, so as HVDC, might stretch to 1000 km, bit still that doesn't seem like very far.

But how could you overlook UHVDC, which is designed for long-haul power?

Using SWER UHVDC with low-temperature Mars min resistance, you'd get much greater coverage, as with the single-payload segments connecting notional grid farms, above (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309792#msg2309792).

You might calculate the number of those 150 t cable payloads needed to connect Phlegra Montes to a facility at 85 N.

And remember, polar sites get no appreciable solar insolation in winter.  Even a gigantic polar PV farm wouldn't help much then.
I totally agree that power lines will eventually be needed, just perhaps not soon in the development.  The carbon based wires are also a fun element that might save on mass.  It's just that local solar is way simpler, and there is every expectation of water fairly down towards the equator, so no absolute requirement to go north or south fast.  I don't know the characteristics of ultra high DC, but I doubt it's something that you want to start your settlement with?  there will already be so much to develop.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/12/2021 08:09 pm
I don't know the characteristics of ultra high DC, but I doubt it's something that you want to start your settlement with?

Why would you imagine HVDC to be much easier?  Any polar facility must be powered; this is at least an efficient way.

And you can't rely on PV farms located anywhere near the poles, as you saw from the insolation plot (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39785.0;attach=2068770;sess=44864).

How many UHVDC cable payloads did you calculate, to reach 85 N?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/12/2021 11:11 pm
I don't know the characteristics of ultra high DC, but I doubt it's something that you want to start your settlement with?

Why would you imagine HVDC to be much easier?  Any polar facility must be powered; this is at least an efficient way.

And you can't rely on PV farms located anywhere near the poles, as you saw from the insolation plot (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39785.0;attach=2068770;sess=44864).

How many UHVDC cable payloads did you calculate, to reach 85 N?
It would take about 5000 km to go from the equator to 85deg North.
Ultra High Voltage DC, above 800 kV. So a single cable would be more than enough.

I live a few km away from the lab where Hydro Quebec developed the 750 kV AC lines that we use in the province.  It's a huge facility and it took a long time to work out the kinks.  The person behind the project won a number of prestigious awards.  The system moves GWatts of power, day in day out.  Everything about the system is large.  I have no doubt UHVDC is similar, and the projects mentioned in Wikipedia are gigantic.
So scaling this down to a few measly kW on Mars doesn't seem to me to be a likely project.  Perhaps when the population moves up into the tens of millions.
It's a lot more likely, in my opinion, that northern facilities will be like northern facilities in Canada.  Highly automated fly in fly out operations, using a minimum amount of power.  High resistive loses in conventional power lines will be repaid by higher costs, or they will truck in methane and oxygen and burn that, whatever is cheapest.
There is some wind power at Raglan mine in Northern Quebec, perhaps there are northern winds on Mars.  Or else it's one of those applications where nuclear really makes sense, eventually.  But I wouldn't bet on it.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/14/2021 03:46 pm
I don't know the characteristics of ultra high DC, but I doubt it's something that you want to start your settlement with?

Why would you imagine HVDC to be much easier?  Any polar facility must be powered; this is at least an efficient way.

And you can't rely on PV farms located anywhere near the poles, as you saw from the insolation plot (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39785.0;attach=2068770;sess=44864).

How many UHVDC cable payloads did you calculate, to reach 85 N?
It would take about 5000 km to go from the equator to 85deg North.
Ultra High Voltage DC, above 800 kV. So a single cable would be more than enough.

I live a few km away from the lab where Hydro Quebec developed the 750 kV AC lines that we use in the province.  It's a huge facility and it took a long time to work out the kinks.  The person behind the project won a number of prestigious awards.  The system moves GWatts of power, day in day out.  Everything about the system is large.  I have no doubt UHVDC is similar, and the projects mentioned in Wikipedia are gigantic.
So scaling this down to a few measly kW on Mars doesn't seem to me to be a likely project.  Perhaps when the population moves up into the tens of millions.
It's a lot more likely, in my opinion, that northern facilities will be like northern facilities in Canada.  Highly automated fly in fly out operations, using a minimum amount of power.  High resistive loses in conventional power lines will be repaid by higher costs, or they will truck in methane and oxygen and burn that, whatever is cheapest.
There is some wind power at Raglan mine in Northern Quebec, perhaps there are northern winds on Mars.  Or else it's one of those applications where nuclear really makes sense, eventually.  But I wouldn't bet on it.

It runs from 33 N.  10 MW, plausibly 2 cable payloads.  Hydro-Quebec is 37 GW overall, scaled up at least 3700x.  The "truck" you prefer for regular and very inefficient methalox power could instead deploy cable at graded roadside, only once.  Wind is unreliable at 85 N, as elsewhere. 

Image:  Mars GCM screen:  characteristic modeled low winter winds at 85 N.  Note scale.  NASA / GISS.

Oddly, you ignored the worked example (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437), and talked over it.  But anyway, Elon does anticipate polar power supply from lower latitudes (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309792#msg2309792):

Quote from: Elon Musk
And then you can send it to the poles... with high-voltage lines...


Edit/Lar: Struck out snark. Struck out self references. Stop referencing yourself. Stop giving nonstandard quotes... why did you not just give a link to the tweet? The tweet gets embedded.

Edit/LMT:  It wasn't snark; he ignored the sourced material, posting odd and false text.  And Elon's tweet is embedded right above, already; I just extracted his most relevant sentence there.  Posters don't have to repeat every little thing.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/15/2021 07:06 pm
Given the big difference in temperature between day and night, shouldn't the radiators work much better at night?
In equatorial martian summer, average high (https://en.wikipedia.org/wiki/Climate_of_Mars) is 274 K, average low is 205 K. Winter is 250 K and 186 K respectively. Radiating from 320 K into those temperatures can dissipate 275, 495, 375 or 525 W/m^2 respectively. Radiating from 370 K into those temperatures could dissipate 740, 960, 840 or 1000 W/m^2 respectively, improving power density at the cost of some efficiency.

In reality the thermal radiation environment would be a mix of high altitude air and space, which is somewhat colder than just the air, so performance would be improved by some moderate factor compared to the above.
Quote
You don't include (that I can tell) anything for conduction through the soil. I know the bare regolith is a pretty good insulator, but I also know that <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JE003938 (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JE003938)"that changes dramatically with the addition of small amounts of water/ice and even concrete. Or would conduction only help for a while, up until the ground under the reactor warmed up?
Yes, the regolith has not much heat capacity and abysmal thermal conductivity. If you bury something you want to maintain at a certain temperature in 5-10 m of regolith you can ignore seasonal temperature swings, to give you some idea.

So efficient heat transfer to the ground requires fine tendrils going everywhere, and the only place for the ground to dump heat is ~10 m down and once that warms up the rest has to go up, making it a radiator with extra steps. If it's worth doing at all I don't know a good design.

Quote
What's the absolute best you could do? I'm visualizing tube-shaped radiators open at the bottom that suck in air from below via natural convection and (maybe) transfer heat down via a concrete base. For (say) a 1 MW reactor, how big would the radiator farm actually have to be?
The quoted figures for radiators are for dissipating heat only by thermally emitting infrared light, as warm objects do. For the highest power density case above exhausting heat at 370 K, a 1 MWe reactor with an efficiency of 35% would need to dissipate 1.85 MW of heat and require roughly 2000 m^2 of radiators.

However, in reality the atmosphere can sink some heat. Using the 370 K exhaust temperature and the 240 K daily average temperature during equatorial summer, the enthalpy of CO2 (https://webbook.nist.gov/cgi/fluid.cgi?P=.0006&TLow=217&THigh=400&TInc=.5&Applet=on&Digits=5&ID=C124389&Action=Load&Type=IsoBar&TUnit=K&PUnit=MPa&DUnit=kg%2Fm3&HUnit=kJ%2Fkg&WUnit=m%2Fs&VisUnit=Pa*s&STUnit=N%2Fm&RefState=DEF) at 6 kPa goes from 460 kJ/kg at 240 K to 570 kJ/kg at 370 K, a rise of 110 kJ/kg so if I can heat 17 kg/s of CO2 from 240 K to 370 K that is enough to dump the heat. The density of CO2 gas at 240 K is .013 kg/m^3, so I need to feed 1300 m^3/s of atmosphere through the heat exchanger.

For that purpose I can use a chimney or a fan. The fan would probably be much lighter, unless the chimney could be supported by the buoyancy of the exhaust gases like a hot air balloon. I choose a speed of 30 m/s in order to achieve high power density without loosing too much power to the motor driving the fan. The intake area would be 43 m^2, eg a 5.8 m diameter circle.
Quote
I found this a little confusing. If you have ready access to ice and/or CO2 ice, shouldn't that give you effectively limitless ability to dispose of waste heat with a fairly small footprint?
Vaporizing water absorbs more enthalpy per mass than vaporizing CO2, roughly 2.5e6 J/kg. The heat of melting and of temperature changes are small by comparison. The above 1 MWe nuclear power plant could dissipate the heat at, say, 280 K and still boil the water due to low ambient pressure, so let's say its efficiency is 42% somewhat arbitrarily. It would need to dissipate 1.4 MW of heat by boiling 0.55 kg/s of water.

It's not so much. However, if it runs for 20 years it will need 340 kton of water. If you're sitting on an ice sheet, maybe you can get it from almost right next door. If you excavate the ice from a depth of up to 100 m, then you need 3400 m^2 of quarry footprint, which is similar to the footprint of the radiators. Of course if it only has to run for 3 months while you set up other infrastructure, such as radiators, then digging up ice sounds more attractive because you only need 4300 tons of it.

Also, if you exhaust your 280 K boiling water into a balloon of 56 m diameter, that balloon will have 10,000 m^2 of surface area from which to radiate heat and recondense the water. If the balloon were buoyant, then it could have an absolutely tiny mass compared to other radiators with so much surface area. You could pack spares, since the mass would be much lower than other components. If something happens to the balloon, you just exhaust to atmosphere until you can replace it, consuming a bit of water. It seems like it might perhaps be an effective radiator design, in spite of the comedy.
The argument against wind power is that the surface winds are too low and would need either a very tall tower or a balloon. Hmmm.


A new form of cogeneration? Mars is so power poor ya gotta take what you can get. Actually this emphasizes an important point. There is probably no one solution.


Diversification can only be a good thing until real people (not us armchair guys) get their hands dirty over time. Then they'll have ground truth knowledge of what works best under different circumstances. Theory is great but experience is better.


An minor nit Ive thrown out on occasion. Needs for expedition 1-3 are entirely different than later. 1-3 are strictly about survival and initial build out. The next several (or many) synods are about more than survival but not yet about thriving. That's when the technology shakeout will happen. Once they know what works and what doesn't, the stage will be set for Mars to thrive. This applies to everything, not just power.


A lot of the disagreement here is because of us thinking about but not acknowledging different phases of future history. Is there any way to fix this?
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/15/2021 08:13 pm
LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Moreover, Paul451 was confused in imagining that Opportunity's reported "total solar energy" could have been direct+indirect insolation.  The rover had no device capable of taking such a combined measurement.  Optical depth was measured directly from Pancam solar images and reported as tau; it corresponded closely with power.  Total insolation could only be modeled, as in Lemmon et al. 2015, Fig. 12b:  "modeled... direct plus diffuse surface insolation (middle, blue)".  Note that the total modeled insolation drop is not nearly severe enough to explain the 2007 Opportunity power crisis; only tau explains, quantitatively.

Refs.

Lemmon, M.T., Wolff, M.J., Bell III, J.F., Smith, M.D., Cantor, B.A. and Smith, P.H., 2015. Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. (https://arxiv.org/pdf/1403.4234) Icarus, 251, pp.96-111.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/15/2021 08:16 pm
LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Moreover, Paul451 was confused in imagining that Curiosity's reported "total solar energy" could have been direct+indirect insolation.  The rover had no device capable of taking such a combined measurement.  Optical depth was measured directly from Pancam solar images and reported as tau; it corresponded closely with power.  Total insolation could only be modeled, as in Lemmon et al. 2015, Fig. 12b:  "modeled... direct plus diffuse surface insolation (middle, blue)".  Note that the total modeled insolation drop is not nearly severe enough to explain the 2007 Opportunity power crisis; only tau explains (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), quantitatively.

Refs.

Lemmon, M.T., Wolff, M.J., Bell III, J.F., Smith, M.D., Cantor, B.A. and Smith, P.H., 2015. Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. (https://arxiv.org/pdf/1403.4234) Icarus, 251, pp.96-111.
AGAIN, you reference your self, however in the graph you referenced, ONLY THE TOP SUBCELL is listed, this is the subcell least sensitive to red light of all the three sub cells of a triple junction solar cell.

Again, quit making false claims super confidently and referencing yourself. And yet you have the gall to accuse Paul of making a mistake.
Title: Re: Power options for a Mars settlement
Post by: DistantTemple on 11/15/2021 09:07 pm
OK change the subject.
As we all know Kayla Barron is on the ISS. And we should all know, since its been repeated frequently that she is an expert on nucler energy
Quote from: NASA***
Her graduate research focused on modeling the fuel cycle for a next-generation, thorium-fueled nuclear reactor concept. Following graduate school, Barron attended the U.S. Navy’s nuclear power and submarine officer training

She is young, just starting her spaceflight career on the ISS and seems to be a perfect candidate for Lunar missions, preparing her for early trips to Mars, whilst still in the prime of her career. She has officer/management/leadership experience. The successful submarine tours bode well for successful spaceflight and long confined surface habitat operations.

This looks like NASA lining up its ducks for future nuclear power capability on the Moon and Mars. Or maybe they just got lucky.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/15/2021 10:20 pm
LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Moreover, Paul451 was confused in imagining that Opportunity's reported "total solar energy" could have been direct+indirect insolation.  The rover had no device capable of taking such a combined measurement.  Optical depth was measured directly from Pancam solar images and reported as tau; it corresponded closely with power.  Total insolation could only be modeled, as in Lemmon et al. 2015, Fig. 12b:  "modeled... direct plus diffuse surface insolation (middle, blue)".  Note that the total modeled insolation drop is not nearly severe enough to explain the 2007 Opportunity power crisis; only tau explains (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), quantitatively.

Refs.

Lemmon, M.T., Wolff, M.J., Bell III, J.F., Smith, M.D., Cantor, B.A. and Smith, P.H., 2015. Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. (https://arxiv.org/pdf/1403.4234) Icarus, 251, pp.96-111.

AGAIN, you reference your self, however in the graph you referenced, ONLY THE TOP SUBCELL is listed, this is the subcell least sensitive to red light of all the three sub cells of a triple junction solar cell.

Again, quit making false claims super confidently and referencing yourself. And yet you have the gall to accuse Paul of making a mistake.

We might complain when someone posts a falsehood while simply ignoring references.  The "gall"?

Short-circuit current (https://www.pveducation.org/pvcdrom/solar-cell-operation/short-circuit-current), hence power, is limited by the top sub-cell; referencing Landis et al. 2004 (http://cmapspublic3.ihmc.us/rid=1P89FWDQW-1D6FSXV-17DG/Mars%20Solar%20Power%202004.pdf) once again:

Quote from: Landis et al. 2004
For the triple-junction solar cells used on the MER solar arrays, the short-circuit current is limited by the top sub-cell of the three-cell stack.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/15/2021 10:52 pm
LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Moreover, Paul451 was confused in imagining that Curiosity's reported "total solar energy" could have been direct+indirect insolation.  The rover had no device capable of taking such a combined measurement.  Optical depth was measured directly from Pancam solar images and reported as tau; it corresponded closely with power.  Total insolation could only be modeled, as in Lemmon et al. 2015, Fig. 12b:  "modeled... direct plus diffuse surface insolation (middle, blue)".  Note that the total modeled insolation drop is not nearly severe enough to explain the 2007 Opportunity power crisis; only tau explains (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), quantitatively.

Refs.

Lemmon, M.T., Wolff, M.J., Bell III, J.F., Smith, M.D., Cantor, B.A. and Smith, P.H., 2015. Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. (https://arxiv.org/pdf/1403.4234) Icarus, 251, pp.96-111.

AGAIN, you reference your self, however in the graph you referenced, ONLY THE TOP SUBCELL is listed, this is the subcell least sensitive to red light of all the three sub cells of a triple junction solar cell.

Again, quit making false claims super confidently and referencing yourself. And yet you have the gall to accuse Paul of making a mistake.

We might complain when someone posts a falsehood while simply ignoring references.  The "gall"?

Short-circuit current (https://www.pveducation.org/pvcdrom/solar-cell-operation/short-circuit-current), hence power, is limited by the top sub-cell; referencing Landis et al. 2004 (http://cmapspublic3.ihmc.us/rid=1P89FWDQW-1D6FSXV-17DG/Mars%20Solar%20Power%202004.pdf) once again:

Quote from: Landis et al. 2004
For the triple-junction solar cells used on the MER solar arrays, the short-circuit current is limited by the top sub-cell of the three-cell stack.
But you won’t operate in short-current mode. Maximum power output does not occur in short circuit mode!

Anyway, if you think it applies to total power (not just short circuit current), all it means is that the 2% MEASURED solar power output from Opportunity is worst case and an architecture optimized for dust storms would perform even better.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/15/2021 11:09 pm
Short-circuit current (https://www.pveducation.org/pvcdrom/solar-cell-operation/short-circuit-current), hence power, is limited by the top sub-cell; referencing Landis et al. 2004 (http://cmapspublic3.ihmc.us/rid=1P89FWDQW-1D6FSXV-17DG/Mars%20Solar%20Power%202004.pdf) once again:

Quote from: Landis et al. 2004
For the triple-junction solar cells used on the MER solar arrays, the short-circuit current is limited by the top sub-cell of the three-cell stack.

But you won’t operate in short-current mode. Maximum power output does not occur in short circuit mode!

As the ASU professors noted in the link above:

Quote
The short-circuit current is due to the generation and collection of light-generated carriers. For an ideal solar cell at most moderate resistive loss mechanisms, the short-circuit current and the light-generated current are identical. Therefore, the short-circuit current is the largest current which may be drawn from the solar cell.

Do you see Paul451's mistake (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2310818#msg2310818), btw?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/16/2021 12:30 am
Short-circuit current (https://www.pveducation.org/pvcdrom/solar-cell-operation/short-circuit-current), hence power, is limited by the top sub-cell; referencing Landis et al. 2004 (http://cmapspublic3.ihmc.us/rid=1P89FWDQW-1D6FSXV-17DG/Mars%20Solar%20Power%202004.pdf) once again:

Quote from: Landis et al. 2004
For the triple-junction solar cells used on the MER solar arrays, the short-circuit current is limited by the top sub-cell of the three-cell stack.

But you won’t operate in short-current mode. Maximum power output does not occur in short circuit mode!

As the ASU professors noted in the link above:

Quote
The short-circuit current is due to the generation and collection of light-generated carriers. For an ideal solar cell at most moderate resistive loss mechanisms, the short-circuit current and the light-generated current are identical. Therefore, the short-circuit current is the largest current which may be drawn from the solar cell.

Do you see Paul451's mistake (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2310818#msg2310818), btw?
But again, we don’t HAVE an ideal cell, so we’re not operating in the short circuit limit. And Of course, even so, the consequence of that is that the power measured by opportunity on its solar arrays, about 2%, is therefore a worst case. An optimized system would perform even better, which is what Dr. Landis (old mentor of mine) was proposing.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/16/2021 12:32 am
LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Moreover, Paul451 was confused in imagining that Curiosity's reported "total solar energy" could have been direct+indirect insolation.  The rover had no device capable of taking such a combined measurement.  Optical depth was measured directly from Pancam solar images and reported as tau; it corresponded closely with power.  Total insolation could only be modeled, as in Lemmon et al. 2015, Fig. 12b:  "modeled... direct plus diffuse surface insolation (middle, blue)".  Note that the total modeled insolation drop is not nearly severe enough to explain the 2007 Opportunity power crisis; only tau explains, quantitatively.

Refs.

Lemmon, M.T., Wolff, M.J., Bell III, J.F., Smith, M.D., Cantor, B.A. and Smith, P.H., 2015. Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. (https://arxiv.org/pdf/1403.4234) Icarus, 251, pp.96-111.
Wrong. The instrument Opportunity has for making that measurement is its solar arrays.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/16/2021 02:48 am
LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Moreover, Paul451 was confused in imagining that Curiosity's reported "total solar energy" could have been direct+indirect insolation.  The rover had no device capable of taking such a combined measurement.  Optical depth was measured directly from Pancam solar images and reported as tau; it corresponded closely with power.  Total insolation could only be modeled, as in Lemmon et al. 2015, Fig. 12b:  "modeled... direct plus diffuse surface insolation (middle, blue)".  Note that the total modeled insolation drop is not nearly severe enough to explain the 2007 Opportunity power crisis; only tau explains, quantitatively.

Refs.

Lemmon, M.T., Wolff, M.J., Bell III, J.F., Smith, M.D., Cantor, B.A. and Smith, P.H., 2015. Dust aerosol, clouds, and the atmospheric optical depth record over 5 Mars years of the Mars Exploration Rover mission. (https://arxiv.org/pdf/1403.4234) Icarus, 251, pp.96-111.

Wrong. The instrument Opportunity has for making that measurement is its solar arrays.

No, the rover didn't report a guesstimate of light intensity from current; that would be redundant, since it was reporting actual current anyway, right? 

Tau was an actual Pancam measurement of transmitted light intensity.  The rover had no device to measure the intensity of indirect, diffuse light.  Why else would Lemmon et al. have to model it?
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/16/2021 03:26 am
To separate out dust on panels vs indirect+direct light.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/16/2021 03:41 am
An optimized system would perform even better, which is what Dr. Landis (old mentor of mine) was proposing.

That's a backhanded way of saying Opportunity's solar cells were not optimized for redshifted storm light, and couldn't make much use of it.

If you understand optimization, you should post such info.  E.g., the newer InGaP/InGaAs/Ge solar cells used on Insight have better response to storm orange/red.  We can compare the representative response of an InGaP/InGaAs/Ge top sub-cell to Opportunity's GaInP/GaAs/Ge top sub-cell (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Image:  InGaP/InGaAs/Ge multi-junction solar cell response.  Electricity conversion in color.  Fraunhofer Institute for Solar Energy Systems.

These solar cells are no panacea, of course.  Insight's power output is still closely tied to tau, and Insight's "tau survival limit" was set at 4.56 in Lisano 2018 -- a value slightly lower than 5, which Opportunity survived in 2007.

Refs.

Lisano, M., 2018. InSight: 2018 Dust Storm Discussion. (https://trs.jpl.nasa.gov/bitstream/handle/2014/50257/CL%2318-3717.pdf?sequence=1)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/16/2021 07:33 am
LMT's Zombie "Tau Theory"

LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Nope. Paul451 is right and you're wrong. Repeating your own debunked claims and linking to your own debunked posts is not an argument.

You continue to completely ignore the devastating quantitative failure of your own theory. Your Tau Theory predicts only 1/1000th as much power as Opportunity produced during tau = 10.8.

This isn't a rounding error. This isn't a typo. This is a world-shattering counterexample that completely explodes your Theory. The numerical predictions are simply spectacularly, breathtakingly, absurdly wrong.

The panels are slightly less efficient at using red light, yes. But you're only looking at one side of the coin. If you look at the spectral curves of direct vs. indirect light on Mars, it's only about a factor of 2 difference at low Sun angles. But the diffuse light can be 100x greater (or more), so the spectral factor difference is completely swamped by the difference in the absolute quantity of diffuse vs. transmitted light available.

https://ntrs.nasa.gov/api/citations/20110000777/downloads/20110000777.pdf (https://ntrs.nasa.gov/api/citations/20110000777/downloads/20110000777.pdf)

Also, your claim that solar panels on Mars don't use indirect sunlight is explicitly contradicted by Scott Manley at 5:42.

https://www.youtube.com/watch?v=TS7S8T8vExM#t=296

Are you calling Scott Manley a liar?  :-\ :-\ :-\ :-\ :-\

Your Tau Theory is dead. You've tried resurrecting its corpse in (per your own copious links) three different threads now. Let it go, LMT.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/16/2021 01:04 pm
LMT's Zombie "Tau Theory"

LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Nope. Paul451 is right and you're wrong. Repeating your own debunked claims and linking to your own debunked posts is not an argument.

You continue to completely ignore the devastating quantitative failure of your own theory. Your Tau Theory predicts only 1/1000th as much power as Opportunity produced during tau = 10.8.

This isn't a rounding error. This isn't a typo. This is a world-shattering counterexample that completely explodes your Theory. The numerical predictions are simply spectacularly, breathtakingly, absurdly wrong.

Again, there's no actual record of energy from tau 10.8 onward, but we know it wasn't much, because the rover failed there.  Your odd text ignores that fact.  Also, your Landis et al. 2006 reference reiterates several uncontroversial points I made above; all consistent, mostly ignored by you. 

Posters might have noticed in Landis et al. 2006, that the rover did not measure indirect lighting.  Instead, the science team derived it initially from photos of the calibration target.  This method was used for 10 days only, "before significant amounts of dust had settled."  That's another way of noticing that the rover's years of "total solar energy" measurements were just tau values.

Refs.

Landis, G.A. and Hyatt, D., 2006, May. The solar spectrum on the martian surface and its effect on photovoltaic performance. (https://ntrs.nasa.gov/api/citations/20110000777/downloads/20110000777.pdf) In 2006 IEEE 4th World Conference on Photovoltaic Energy Conference (Vol. 2, pp. 1979-1982). IEEE.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/16/2021 01:28 pm
Public service announcement: Trolls thrive on attention, they cannot be argued into submission.
Title: Re: Power options for a Mars settlement
Post by: Greg Hullender on 11/16/2021 01:38 pm
Public service announcement: Trolls thrive on attention, they cannot be argued into submission.
Ah, but who is the troll? The one who writes polite explanations, illustrated with references to peer-reviewed papers? Or the ones who write angry, insulting posts with no evidence other than videos?
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/16/2021 01:42 pm
Public service announcement: Trolls thrive on attention, they cannot be argued into submission.
Ah, but who is the troll? The one who writes polite explanations, illustrated with references to peer-reviewed papers? Or the ones who write angry, insulting posts with no evidence other than videos?

[/10-foot-pole]
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/16/2021 05:47 pm
Public service announcement: Trolls thrive on attention, they cannot be argued into submission.
Ah, but who is the troll? The one who writes polite explanations, illustrated with references to peer-reviewed papers? Or the ones who write angry, insulting posts with no evidence other than videos?
At this point it doesn't matter. If one is a troll the other is feeding the troll. Not the first time I've seen this same train wreck with the same trains.


From The Who's "Tommy":
Gonna take ya,
Gonna break ya,
Gonna forget ya, better still.


Tau is disturbing my Wa.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/16/2021 06:40 pm
Public service announcement: Trolls thrive on attention, they cannot be argued into submission.
Ah, but who is the troll? The one who writes polite explanations, illustrated with references to peer-reviewed papers? Or the ones who write angry, insulting posts with no evidence other than videos?
LMT keeps asserting things that aren’t in the things he references. That he has more time to write longer responses and well-formatted references doesn’t mean he’s not a troll.

More to the point, it’s pretty obvious that indirect light is not always directly proportional to reciprocal tau, which is a measure of direct light. He keeps asserting again and again that it is.

On Earth, with a cloud in the way of the Sun, Tau would be incredibly high such that direct light is essentially zero, but indirect light is pretty clearly not zero. QED, they aren’t the same. Now let’s move on!
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/16/2021 06:56 pm
Public service announcement: Trolls thrive on attention, they cannot be argued into submission.

Ah, but who is the troll? The one who writes polite explanations, illustrated with references to peer-reviewed papers? Or the ones who write angry, insulting posts with no evidence other than videos?

Rhetorical questions are dicey on the internet.   ;)

Of interest:  a dive into any PV R&D targeting great specific power in a Martian storm; i.e., low-mass panels enabling unrestricted rover operations even at tau = 5, for example.  It's an open question.

--

One conceivable approach:  quantum dots can be tuned to longer wavelengths, and can be combined in a tandem solar cell with perovskite, as at QD Solar (https://qdsolarinc.com/technology/). 

Image (https://qdsolarinc.com/technology/):  Tandem solar cell spectral capture.  QD Solar.

Quantum dots and perovskite also provide record-setting specific power for solar cells, "soap bubble" thin (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1934701#msg1934701).  Conceivably, very thin tandem QD/perovskite solar panels might be manufactured into an inflatable sphere, which is released as a tethered balloon, for storm PV.  When storm tau rises, a hydrogen canister could inflate the large balloon for release above the rover, where it maximizes conversion of diffuse storm visible light and IR.  Alternately, mass might be reduced by using tuned QD solar cells alone.

Is that an appropriate way to achieve great specific power (W/g) in a Martian storm; i.e., leveraging a solar cell's extremely low mass to compensate for its uncertain power output?  Mass of gas and mechanisms must be included, of course.

And of course, a conducting tether could itself collect power in the storm (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2301573#msg2301573), and that power should be compared against storm PV output.

Image (https://www.popsci.com/mit-researchers-demonstrate-thinnest-solar-cells-yet/):  example thin solar cell.  MIT.


https://www.youtube.com/watch?v=XChMR-WnmUc
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/16/2021 07:35 pm
Public service announcement: Trolls thrive on attention, they cannot be argued into submission.

Ah, but who is the troll? The one who writes polite explanations, illustrated with references to peer-reviewed papers? Or the ones who write angry, insulting posts with no evidence other than videos?

Rhetorical questions are dicey on the internet.   ;)

Of interest:  a dive into any PV R&D targeting great specific power in a Martian storm; i.e., low-mass panels enabling unrestricted rover operations even at tau = 5, for example.  It's an open question.
What’s not an open question is that reciprocal Tau is not always and everywhere proportional to total power production. The ratio of indirect to total insolation is not a constant in a dust storm. It’s physically obvious AND is empirically backed.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/18/2021 08:40 pm
LMT's Zombie "Tau Theory"

LMT's Edmondson/etal reference for Opportunity/Spirit PV output shows that PV output correlates nicely with total insolation (ironically, given LMT thinks he's contradicting me. Would help if he reads his own references.)

Paul451's mistake was addressed in a previous post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2066644#msg2066644), which noted again the correlation of power to light transmission (tau), not to total direct+indirect insolation.  This known correlation makes sense, because Opportunity couldn't draw much power from orange/red diffuse storm light (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185).

Nope. Paul451 is right and you're wrong. Repeating your own debunked claims and linking to your own debunked posts is not an argument.

You continue to completely ignore the devastating quantitative failure of your own theory. Your Tau Theory predicts only 1/1000th as much power as Opportunity produced during tau = 10.8.

This isn't a rounding error. This isn't a typo. This is a world-shattering counterexample that completely explodes your Theory. The numerical predictions are simply spectacularly, breathtakingly, absurdly wrong.

Again, there's no actual record of energy from tau 10.8 onward, but we know it wasn't much, because the rover failed there.  Your odd text ignores that fact.

Tau 10.8 was the measurement for one day, and one day only.

We know the actual record of solar energy from that same day. It was 22 Wh.

There's no sampling mismatch here. The tau value and the solar power value were measured on the exact same day.

  Also, your Landis et al. 2006 reference reiterates several uncontroversial points I made above; all consistent, mostly ignored by you.

Any uncontroversial points are (as the adjective would suggest) not worth discussing.


Posters might have noticed in Landis et al. 2006, that the rover did not measure indirect lighting.  Instead, the science team derived it initially from photos of the calibration target.  This method was used for 10 days only, "before significant amounts of dust had settled."  That's another way of noticing that the rover's years of "total solar energy" measurements were just tau values.

No, it isn't.  You're just stating your desired conclusion without any actual evidence (and in fact, in contradiction of actual evidence).

Saying "well what the scientists who wrote that paper really meant to say was...." doesn't cut the mustard here.

The solar production was 1000x off from your Tau Theory. It's dead, Jim.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/18/2021 09:12 pm
Posters might have noticed in Landis et al. 2006, that the rover did not measure indirect lighting.  Instead, the science team derived it initially from photos of the calibration target.  This method was used for 10 days only, "before significant amounts of dust had settled."  That's another way of noticing that the rover's years of "total solar energy" measurements were just tau values.

No, it isn't.  You're just stating your desired conclusion without any actual evidence (and in fact, in contradiction of actual evidence).

The paper really highlights the difficulty of determining indirect lighting from rover devices.  To think:  just 10 days of dust accumulation terminated the team's analysis.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/18/2021 09:17 pm
Anyway, getting back on-topic, Tau Theory's demise is great for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

"Good news, everyone!" :D
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/18/2021 09:18 pm
I don't know the characteristics of ultra high DC, but I doubt it's something that you want to start your settlement with?

Why would you imagine HVDC to be much easier?  Any polar facility must be powered; this is at least an efficient way.

And you can't rely on PV farms located anywhere near the poles, as you saw from the insolation plot (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=39785.0;attach=2068770;sess=44864).

How many UHVDC cable payloads did you calculate, to reach 85 N?
It would take about 5000 km to go from the equator to 85deg North.
Ultra High Voltage DC, above 800 kV. So a single cable would be more than enough.

I live a few km away from the lab where Hydro Quebec developed the 750 kV AC lines that we use in the province.  It's a huge facility and it took a long time to work out the kinks.  The person behind the project won a number of prestigious awards.  The system moves GWatts of power, day in day out.  Everything about the system is large.  I have no doubt UHVDC is similar, and the projects mentioned in Wikipedia are gigantic.
So scaling this down to a few measly kW on Mars doesn't seem to me to be a likely project.  Perhaps when the population moves up into the tens of millions.
It's a lot more likely, in my opinion, that northern facilities will be like northern facilities in Canada.  Highly automated fly in fly out operations, using a minimum amount of power.  High resistive loses in conventional power lines will be repaid by higher costs, or they will truck in methane and oxygen and burn that, whatever is cheapest.
There is some wind power at Raglan mine in Northern Quebec, perhaps there are northern winds on Mars.  Or else it's one of those applications where nuclear really makes sense, eventually.  But I wouldn't bet on it.

It runs from 33 N.  10 MW, plausibly 2 cable payloads.  Hydro-Quebec is 37 GW overall, scaled up at least 3700x.  The "truck" you prefer for regular and very inefficient methalox power could instead deploy cable at graded roadside, only once.  Wind is unreliable at 85 N, as elsewhere. 

Image:  Mars GCM screen:  characteristic modeled low winter winds at 85 N.  Note scale.  NASA / GISS.

Oddly, you ignored the worked example (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1950437#msg1950437), and talked over it.  But anyway, Elon does anticipate polar power supply from lower latitudes (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309792#msg2309792):

Quote from: Elon Musk
And then you can send it to the poles... with high-voltage lines...


Edit/Lar: Struck out snark. Struck out self references. Stop referencing yourself. Stop giving nonstandard quotes... why did you not just give a link to the tweet? The tweet gets embedded.

Edit/LMT:  It wasn't snark; he ignored the sourced material, posting odd and false text.  And Elon's tweet is embedded right above, already; I just extracted his most relevant sentence there.  Posters don't have to repeat every little thing.
Simple, no ill will here, I don't have the time to work up every reference path and hadn't noticed the link.  I took the post at face value.  I just have a few minutes a day to participate here, so I can't be expected to find every back reference. 
What is false in the text I posted?
What is odd?
The example referenced is an interesting though experiment, but does not seem to have any numbers attached.
There is no demonstration of low power UHVDC as a functional system on Mars.  I have seen and worked on some of the parts of the HVDC line from Labrador to Newfoundland.  It is not a simple system.  the Quebec HVDC ground return line to the US depends on an electrode system imbedded deep into the Earth and substantial infrastructure.
I think this is again a case of not properly identifying when in the development of a settlement we are for the discussion.

I actually said that a power line to the north was possible, just that it might have high losses at lower voltages. At least medium power HVDC is an existing system developed by real companies.  Is there such a thing as UHVDC for a few MW?   It there is so much the better, I have no special love for methalox generators.

There is a cost benefit analysis that is required for every project.  There are at least 20 villages in Quebec and many mining operations that are powered by diesel generators because it is not cost effective to build power lines.  Hydro Quebec, as a state monopoly has the legal obligation to supply electrical power to everyone.  It doesn't have the obligation to use power lines for this. The villages are supplied by ships and have large diesel tanks that stock the fuel for up to a year.  There are no roads to these villages.   
The northern mining site on Mars needs to be more completely described.  If there are trucks or trains of ice coming down, they don't have to go up empty.  They might go up loaded with fuel.

If we need storage to survive dust storms and winter, it can be logical to move the storage medium about, rather than the power itself.  This might be cost effective for a long time during the Mars settlement development.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/18/2021 09:21 pm
Posters might have noticed in Landis et al. 2006, that the rover did not measure indirect lighting.  Instead, the science team derived it initially from photos of the calibration target.  This method was used for 10 days only, "before significant amounts of dust had settled."  That's another way of noticing that the rover's years of "total solar energy" measurements were just tau values.

No, it isn't.  You're just stating your desired conclusion without any actual evidence (and in fact, in contradiction of actual evidence).

The paper really highlights the difficulty of determining indirect lighting from rover devices.  To think:  just 10 days of dust accumulation terminated the team's analysis.

None of that in any way supports your (now thoroughly debunked) Tau Theory.

Let's try to stay on-topic.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/18/2021 09:28 pm
Anyway, getting back on-topic, Tau Theory's demise is great news for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

"Good news, everyone!" :D
So, should I just refer to the rover values as a minimum solar power value, and build up from there?

-Ensure that life support for a settlement is covered by this minimum, provided locally.
-Arrange food production in short easily interruptible cycles. 
-Ensure food production is higher than needed by a wide margin, and use extra production as a material resource for petrochemical industries or for soil amendment, past a certain minimum storage value.
-Produce a small amount of extra fuel for safety's sake for critical infrastructure in case of accident or unknown unknowns.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/18/2021 09:38 pm
Anyway, getting back on-topic, Tau Theory's demise is great news for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

"Good news, everyone!" :D
So, should I just refer to the rover values as a minimum solar power value, and build up from there?


I think that's a sensible baseline.


One thing that didn't come up yet was that they observed a substantial increase in dust loading right before Opportunity died. Real Mars solar arrays (which are big) will likely use electrostatic sweeping (https://www.sciencedirect.com/science/article/abs/pii/S0094576511001883) to actively remove dust buildup. Cheaper and vastly fewer moving parts than using robots or EVA-suited astronauts.

Title: Re: Power options for a Mars settlement
Post by: Asteroza on 11/18/2021 10:05 pm
Anyway, getting back on-topic, Tau Theory's demise is great news for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

"Good news, everyone!" :D
So, should I just refer to the rover values as a minimum solar power value, and build up from there?


I think that's a sensible baseline.


One thing that didn't come up yet was that they observed a substantial increase in dust loading right before Opportunity died. Real Mars solar arrays (which are big) will likely use electrostatic sweeping (https://www.sciencedirect.com/science/article/abs/pii/S0094576511001883) to actively remove dust buildup. Cheaper and vastly fewer moving parts than using robots or EVA-suited astronauts.

I dunno, kicking a Spot Mini with an arm out the airlock to go jiggle solar array posts when you already have one might be easier. There have been examples of a monorail robot arm running around a solar array farm adjusting motorless PV panel angle all day that ends up being cheaper than putting an active heliostat setup on each panel. Though the thought of a Spot ramming it's rear end on a post like a dog marking a tree will amuse a few people...
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/19/2021 12:40 am
...Tau Theory's demise is great for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

Panels barely provided "life support" to Opportunity at tau = 4.7 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309025#msg2309025), the day the camera was turned off.  Those panels had been cleaned recently, if you can believe that.

Insight's newer and larger PV array has a "tau survival limit" of 4.56 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2310960#msg2310960), similar to Opportunity's, apparently.  In extremity, even with all margin removed and Insight's power draw strictly minimized, a "2001 TES Storm, at tau of 8 or higher for weeks, [is] not survivable (https://trs.jpl.nasa.gov/bitstream/handle/2014/50257/CL%2318-3717.pdf?sequence=1)".

Neumayer-Station III (https://forum.nasaspaceflight.com/index.php?topic=55111.msg2305018#msg2305018) power requirement gives a starting point for settlement minimum power scaling.  The PV literature tells a consistent story; we'd want to scale accordingly (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).

Image:  Neumayer-Station III.  Matthias Maasch.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/19/2021 02:16 am
Anyway, getting back on-topic, Tau Theory's demise is great news for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

"Good news, everyone!" :D
So, should I just refer to the rover values as a minimum solar power value, and build up from there?

-Ensure that life support for a settlement is covered by this minimum, provided locally.
-Arrange food production in short easily interruptible cycles. 
-Ensure food production is higher than needed by a wide margin, and use extra production as a material resource for petrochemical industries or for soil amendment, past a certain minimum storage value.
-Produce a small amount of extra fuel for safety's sake for critical infrastructure in case of accident or unknown unknowns.
Margins can only be a good thing. Growing a little extra food is wise. Making more methalox than the expenditure budget calls for is wise. Doing both is really wise.


Don't want to go hog wild. It's generally suggested that having immediately available savings equal to 6 months income will provide a cushion for almost anything fate can throw at you. The principal holds on Mars. Extra Methalox can plug many holes and can even become food with a time lag in the conversion. Extra food will cover the lag.


Excrement occurs. On Mars you plan for it or you die.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/19/2021 02:31 am
...Tau Theory's demise is great for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

Panels barely provided "life support" to Opportunity at tau = 4.7 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309025#msg2309025), the day the camera was turned off.  Those panels had been cleaned recently, if you can believe that.

Insight's newer and larger PV array has a "tau survival limit" of 4.56 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2310960#msg2310960), similar to Opportunity's, apparently.  In extremity, even with all margin removed and Insight's power draw strictly minimized, a "2001 TES Storm, at tau of 8 or higher for weeks, [is] not survivable (https://trs.jpl.nasa.gov/bitstream/handle/2014/50257/CL%2318-3717.pdf?sequence=1)".

Neumayer-Station III (https://forum.nasaspaceflight.com/index.php?topic=55111.msg2305018#msg2305018) power requirement gives a starting point for settlement minimum power scaling.  The PV literature tells a consistent story; we'd want to scale accordingly (https://forum.nasaspaceflight.com/index.php?topic=45597.msg1822304#msg1822304).

Image:  Neumayer-Station III.  Matthias Maasch.
Although it's old numbers, the solar arrays illustrated for the early ITS design could conceivably produce 22 kW of power once at Mars.  So that might be the baseline for the life support system, including atmospheric regeneration of CO2 through Sabatier for a crew of 20.
I agree that insulation will be very important.  I think that the low convection of the Martian atmosphere will certainly help, and that Multi layer vacuum insulation should provide very low losses.
So starting from 20 kW, we might want to add another 20 kW for experiments and thing to do on Mars' surface, for a baseline of 40 kW, or 2 kW per person as a minimum survival rate.  Seems in line with the Antarctic base.
If the 900 W arrays of opportunity went down to 22W, there is a factor of 40.  So there should be at least 800 kW installed.
If we factor in a 25% availability factor because we are now on a surface, 3,2 MW would be required for a base that can provide minimum survival power in a very bad storm.  I think this is fairly close to the numbers others have proposed for the minimum installation required to produce return propellant for a Starship over two years.  Today's SpaceX white paper strongly suggests that most starships will not return from Mars but rather serve as habitat elements, so that will allow the settlement to use more power for food production and less for propellant production.
That would put a settlement at about 150 kW per colonist of installed power.  More or less 30-40%.

So a basic genset providing 40 kW of power, and 60 kW of heat, is a very simple machine.  Of course the Cat unit shown here would need to be extensively modified to burn methalox, but it seems like a very doable project.



Title: Re: Power options for a Mars settlement
Post by: Barley on 11/19/2021 03:03 am

So, should I just refer to the rover values as a minimum solar power value, and build up from there?

The measured values are are an upper limit on the worst case, the worst case will be worse.

You can't know if solar power went lower after the rover stopped communicating.

It also seems unlikely the 14 missions on Mars have sample the worst the planet has to offer.

I would not rely on any solar power during the storm, but be prepared to survive on stored power alone.  I would tolerate survivable (possibly irreparable) damage to the base in the event of no solar power and hope that what ever trickle of solar power was available could prevent it.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/19/2021 03:19 am

So, should I just refer to the rover values as a minimum solar power value, and build up from there?

The measured values are are an upper limit on the worst case, the worst case will be worse.

You can't know if solar power went lower after the rover stopped communicating.

It also seems unlikely the 14 missions on Mars have sample the worst the planet has to offer.

I would not rely on any solar power during the storm, but be prepared to survive on stored power alone.  I would tolerate survivable (possibly irreparable) damage to the base in the event of no solar power and hope that what ever trickle of solar power was available could prevent it.
I think you can rely on solar power, however you must plan for the absence of solar power at any time, not just for the worst storm but just accidents.  And as you are entirely dependent on a continuous power supply I suggest a tier 4 class power system would be required.  This is simpler than it sound as that really means two independent gensets and redundancy in the internal power distribution and cooling systems.

13 l per hour of diesel is about 20l of CH4 or 9 kg.  So one week is 1.5 tonnes of methane.  This is 0,5% of the fuel required for a Starship.  So a 10% allocation of propellant would be enough to assure survival for 20 weeks.  Seems more than enough, since it is not really required but merely a backup in case storms are even worse than expected.

 




Title: Re: Power options for a Mars settlement
Post by: LMT on 11/19/2021 03:33 am
I would not rely on any solar power during the storm, but be prepared to survive on stored power alone.  I would tolerate survivable (possibly irreparable) damage to the base in the event of no solar power and hope that what ever trickle of solar power was available could prevent it.

Such a "storm survival scenario", with its dramatic trickle, etc., isn't realistic in a sensible settlement design.

ISRU battery farms could power a settlement at any scale, through winter nights, and through any plausible storm duration.  It just takes a bit of planning and industry.  That's a relevant thread focus.

Disasters can occur, of course, and you prepare options; but you don't design a power system to cause disasters. 

Think big.

--

Optimizing ISRU battery farms:  1 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2308622#msg2308622)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/19/2021 03:52 am
I would not rely on any solar power during the storm, but be prepared to survive on stored power alone.  I would tolerate survivable (possibly irreparable) damage to the base in the event of no solar power and hope that what ever trickle of solar power was available could prevent it.

Such a "storm survival scenario", with its dramatic trickle, etc., isn't realistic in a sensible settlement design.

ISRU battery farms could power a settlement at any scale, through winter nights, and through any plausible storm duration.  It just takes a bit of planning and industry.  That's a relevant thread focus.

Disasters can occur, of course, and you prepare options; but you don't design a power system to cause disasters. 

Think big.

--

Optimizing ISRU battery farms:  1 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 2 (https://forum.nasaspaceflight.com/index.php?
topic=39785.msg2308622#msg2308622)

I can see the point of batteries for night time operations, seems like a given for any solar based design. 

For a 150 kW per colonist base and 20 colonists, that's 150 x 20 = 3000 kW x 10 h = 30 000 kWh hour of battery to get through the night safely while maintaining operations, or about 200+ or so tonnes of 100 kWh battery packs.

if we are running the minimum 40 kW survival demand from the batteries, we get 30 000 /40 = 750 hours or about 30 days.
It's probably enough, so yes, batteries would  seem to provide backup for a reasonable storm.  In situ batteries would be even better and an eventual requirement for a settlement.

However I would still have some gensets as long term backup, as the energy is stored in the fuel is available and the mass of the genset pair is about 2 tonnes, so a tiny  amount of mass for the safety it gives.  But it seems like the backup of a backup.
Title: Re: Power options for a Mars settlement
Post by: Thrustpuzzle on 11/19/2021 11:25 am
Some comparisons of solid state commercial energy storage/conversion systems that could be adapted to Mars. (ie you could have these as ready to launch payloads in a year with low R+D risk)

A commercial 300kW CH4/O2 fuel cell (https://www.bloomenergy.com/wp-content/uploads/es5-300kw-datasheet-2019.pdf) runs at about 50% energy conversion efficiency. The example generator is about 16 tons in mass and as a fuel cell is solid state other than the pumps needed to pressurize the supply. It generates (useful!) waste heat and pure CO2 exhaust. Its capacity is determined by  CH4/O2 storage, not by the machine itself. It's robust, designed for 24/7 operation over years. There are smaller 75, 100, and 200 kW versions.
 
That generator is for an Earth atmosphere commercial natural gas power generator, not a Martian version. A Martian variant would be simpler (feedstocks would be pure CH4 and pure O2, so no need for the fuel cell to filter out contaminants from natural gas, or deal with a N2/O2 wet air mix) but also more complex in that it would need to deal with Martian temperatures. And it would need to survive packing, transport, and unpacking. The 16 tons weight is not mass-optimized, so one could imagine it could be drastically lightened with some effort.

A Tesla Powerwall 2  (https://en.wikipedia.org/wiki/Tesla_Powerwall)electric storage battery provides about 6kW peak delivery, energy capacity of about 10 kWh, with a mass of about 100kg.  50 of them would provide a similar 300 kW peak and mass roughly 5 tons.  Its energy capacity per kg is likely the key metric.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/19/2021 01:58 pm
Some comparisons of solid state commercial energy storage/conversion systems that could be adapted to Mars. (ie you could have these as ready to launch payloads in a year with low R+D risk)

A commercial 300kW CH4/O2 fuel cell (https://www.bloomenergy.com/wp-content/uploads/es5-300kw-datasheet-2019.pdf) runs at about 50% energy conversion efficiency. The example generator is about 16 tons in mass and as a fuel cell is solid state other than the pumps needed to pressurize the supply. It generates (useful!) waste heat and pure CO2 exhaust. Its capacity is determined by  CH4/O2 storage, not by the machine itself. It's robust, designed for 24/7 operation over years. There are smaller 75, 100, and 200 kW versions.
 
That generator is for an Earth atmosphere commercial natural gas power generator, not a Martian version. A Martian variant would be simpler (feedstocks would be pure CH4 and pure O2, so no need for the fuel cell to filter out contaminants from natural gas, or deal with a N2/O2 wet air mix) but also more complex in that it would need to deal with Martian temperatures. And it would need to survive packing, transport, and unpacking. The 16 tons weight is not mass-optimized, so one could imagine it could be drastically lightened with some effort.

A Tesla Powerwall 2  (https://en.wikipedia.org/wiki/Tesla_Powerwall)electric storage battery provides about 6kW peak delivery, energy capacity of about 10 kWh, with a mass of about 100kg.  50 of them would provide a similar 300 kW peak and mass roughly 5 tons.  Its energy capacity per kg is likely the key metric.
It depends how we run the settlement, but as a night storage system the fuel cell is terribly inefficient.  As a replacement for the genset it seems much more interesting, and perhaps closer to reality than a methalox genset.  At 300 kW though it's for a much larger settlement than 20 people.  It the base case I propose is correct, this would be used for a 160 people settlement as a backup plan to the 2250 tonnes of batteries required for night time operation.  That 2250 tonnes number is not optimized in any way, and shows there is a very clear gain for developing in situ flow batteries quickly.
150 people on Mars, with a ratio of 10 cargos to 1 passenger with Starships holding 20 people is 8 crewed starships, or 80 uncrewed starships, so 8000 tonnes of material of various nature!
I believe the Tesla Powerwall is not mass optimised, and that the kWh per kg ratio of vehicles power packs are better.

Title: Re: Power options for a Mars settlement
Post by: Barley on 11/19/2021 03:15 pm

It depends how we run the settlement, but as a night storage system the fuel cell is terribly inefficient.
... 2250 tonnes of batteries required for night time operation.  That 2250 tonnes number is not optimized in any way.
Energy efficiency, i.e. useful energy out / energy in, is not the critical metric.  Efficient use of mass to Mars and effort of the crew is far more important.

If you're replacing 2250 tonne of battery with 16 tonne of fuel cell you could add 2230 tonne of solar panels to compensate for the low efficiency and still come out ahead.  If you cut the weight of the battery by 90% it still needs to be compared to 200 tonne of solar panels. 

I don't have good figures on the mass of solar panels for mars but I'd guess 10W peak per kg.  That would mean you need better than a 95% reduction in battery mass for batteries to be competitive.

A more refined comparison would also throw in the mass of the increased size of the methalox plant and the effort required to set up the extra panels or for any proposed ISRU.

Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/19/2021 03:35 pm
Round trip energy efficiency generally means waste heat somewhere, which on Mars may not be "wasted", depending on equipment placement.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/19/2021 04:36 pm
Round trip energy efficiency generally means waste heat somewhere, which on Mars may not be "wasted", depending on equipment placement.

Well, in a storage scenario, ideally, you'd want a battery farm.  That enables on-demand delivery of both electrical energy and also heat energy, independently from the same hardware, with negligible losses.

An ISRU battery can have better than 90% round-trip efficiency (https://www.modernoutpost.com/wp-content/uploads/2017/01/Aquion_Energy_M110-LS83_M110-L083_Product_Specification_Sheet.pdf), so very little energy is lost in conversion.  An illustrative 1.4 GWh salt water battery farm could hit that efficiency target, while conceivably requiring only a few hundred tons of cargo; therefore, arguably, mass and efficiency metrics can be best-in-class.  1 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2308622#msg2308622)  No Tesla battery farm (high mass) or methalox generator plant (low efficiency) would be competitive.

The required salt harvest is simple, relative to, say, an FeCl2 flow battery refinery.  Even so, the farm's salt harvest, electrolyte processing, case production, and facility concepts could all be improved.

Speaking of waste heat:

Conceivably, a farm might be integrated directly into hab structures, to minimize the farm's extra structural mass and devices, and to repurpose hab waste heat for battery temperature maintenance.  What might be a good way to do that, as a modification to some common hab design?

Image (https://www.semipermanent.com/stories/xavier-de-kestelier):  Hassell / EOC hab concept.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/19/2021 04:43 pm
Speaking of waste heat:

Conceivably, a farm might be integrated directly into hab structures, to minimize the farm's extra structural mass and devices, and to repurpose hab waste heat for battery temperature maintenance.  What might be a good way to do that, as a modification to some common hab

Yup, though the heat transfer may be bidirectional.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/19/2021 07:56 pm

It depends how we run the settlement, but as a night storage system the fuel cell is terribly inefficient.
... 2250 tonnes of batteries required for night time operation.  That 2250 tonnes number is not optimized in any way.
Energy efficiency, i.e. useful energy out / energy in, is not the critical metric.  Efficient use of mass to Mars and effort of the crew is far more important.

If you're replacing 2250 tonne of battery with 16 tonne of fuel cell you could add 2230 tonne of solar panels to compensate for the low efficiency and still come out ahead.  If you cut the weight of the battery by 90% it still needs to be compared to 200 tonne of solar panels. 

I don't have good figures on the mass of solar panels for mars but I'd guess 10W peak per kg.  That would mean you need better than a 95% reduction in battery mass for batteries to be competitive.

A more refined comparison would also throw in the mass of the increased size of the methalox plant and the effort required to set up the extra panels or for any proposed ISRU.
Thanks, very insightful.  Clearly I was oversimplifying and hadn't thought it through :-[
So there has to be an analysis done on the daily power use and in particular power usage at night.  To reduce the battery or the fuel cell needed.  It doesn't make sense to make methane to burn to make more methane during the night, so fuel processing should be out, I believe.  In general we should also be able to time food production so that most production happens during the day, although there may be some storage used to get a full day's growth.  The problem of stop and start for the Sabatier process had been raised ang guess might play a role as well in the analysis.

Title: Re: Power options for a Mars settlement
Post by: Paul451 on 11/19/2021 10:10 pm
It doesn't make sense to make methane to burn to make more methane during the night, so fuel processing should be out, I believe.
[...] The problem of stop and start for the Sabatier process had been raised ang guess might play a role as well in the analysis.

Electrolysis of water into hydrogen (and LOx) and liquification of gases both seem to require the largest amount of power, so would be confined to the middle of the day (and maybe only during the half year (which is roughly an Earth-year long) with clear skies.) I think they can be shut off reasonably easily, on a day/night cycle.

The methane production doesn't require a high energy input (the reaction itself is a net energy (at least heat) producer), so there's no reason to shut it down at night, and it benefits from 24+hr operation. (But perhaps shut it down seasonally; for eg, ~16 months on, 6 months off. Which allows for maintenance/upgrades/expansion.)

So using that type of production cycle, you need enough liquefied hydrogen storage for 24+hrs of methane production, enough power to produce and liquefy that much hydrogen in half a day (or less). And enough storage for non-liquefied methane produced during the night and early morning, before you've enough power to run the compressors/heat-pumps/etc during the day. (In addition to the expected storage for the full synod's production of liquid methane and oxygen, plus a reserve.)

The only power you need at night is for things like gas pumps, ops/control, and lights/etc. Which should be a small percentage.

In general we should also be able to time food production so that most production happens during the day, although there may be some storage used to get a full day's growth.

Generally, during growth phase, you run ~18hrs out of 24, but you can optimise the LED spectrum around red/blue. During flowering/fruiting, you drop to 12hrs, and broaden the spectrum. Intensity is as high as you can get away with based on the crop. Seedlings/clonings use barely anything.

You definitely want power storage, but it doesn't have to be a full doubling (or more) of daytime use. You'd also want to have crop rotation cycled to keep power use roughly even, so there's always a roughly equal number of crops in growth and flowering stages, at any given time. Seasonally, during "winter" you could drop production back, focus on crops that tolerate less light or growth intensity, perhaps with longer growth cycles. Use "summer" for high growth, high intensity crops, such as grasses (wheat/etc.) Stopping propellant production during "winter" frees up a ton of power for agriculture.

I believe you can force ("turn") most annual crops to switch from growth to flower/fruit stage simply by changing the light cycle. So if a major storm is building, you can turn all the near-mature crops early, harvest as much as possible at the same time that you are also reducing power demand (18hrs to 12hrs), freeing up enough power to let you continue the growth phase of the less mature crops, until you turn those. Gives you a systematic, step-wise draw-down of power consumption as conditions worsen. By the end, during the worst phase, you only need enough power to sustain clones without storable seeds, which is a trivial power draw, and perennials like trees (which tolerate less intensity of light, and can often be wintered/made-dormant during the peak of the storm.)

[Aside: One of the many fake dramas in the NatGeo show Mars that helped ruin the show, the genius biologist who couldn't keep a single tray of his special clone seedlings warm enough during their power crisis. Blah! Stupid. (And pressure doors that open outwards. And people who hide mission-threatening issues from each other. These people deserved to fail.)]
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/20/2021 06:43 am
...if a major storm is building, you can turn all the near-mature crops early, harvest as much as possible at the same time that you are also reducing power demand (18hrs to 12hrs), freeing up enough power to let you continue the growth phase of the less mature crops, until you turn those. Gives you a systematic, step-wise draw-down of power consumption as conditions worsen. By the end, during the worst phase, you only need enough power to sustain clones without storable seeds, which is a trivial power draw, and perennials like trees (which tolerate less intensity of light, and can often be wintered/made-dormant during the peak of the storm.)

[Aside: One of the many fake dramas in the NatGeo show Mars that helped ruin the show, the genius biologist who couldn't keep a single tray of his special clone seedlings warm enough during their power crisis. Blah! Stupid.

Like Joseph Peterson (https://forum.nasaspaceflight.com/index.php?topic=55111.msg2308515#msg2308515), you're reading from an outdated dramatic script yourself there.

No settlement would store so little energy intentionally.  That's disaster by design (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2312201#msg2312201).  Give thought to ISRU energy storage optimization; that's a fertile, brightly-lit field for discussion.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/20/2021 05:37 pm
The long lunar night presents hard power challenges, with some relevance to this thread.  A recent analysis of lunar power system options is given in Kaczmarzyk and Musiał 2021.

Quote
Abstract: Due to the extreme cost of cargo transportation from Earth to the lunar surface, future lunar
base subsystems are required to be rigorously optimized in terms of mass reduction. The purpose of
this paper was to identify and evaluate the influence of key parameters of proposed lunar base power
systems, as well as of the lunar environment on the total power system mass. Nine different power
systems were studied as combinations of two power sources and three energy storage technologies.
Power system architecture, total power demand of the base, its power management strategy, solar
array structure type, Selenographic latitude and solar illumination conditions were nominated as
the primary parameters for this study. Total power system mass calculations were performed for
more than 200 combinations of these parameters, including three separate case studies. The total
mass calculated for each combination included a power source, an energy storage unit, temperature
control and the balance of system. For the wide range of studied parameters, hybrid power systems
that combine solar and nuclear power were found to be the most advantageous solutions in terms of
mass reduction.

Notes:

- A regenerative fuel cell was considered, but disfavored with higher storage requirement.  Lunar ISRU battery electrolyte wasn't considered:  Li-ion batteries would be delivered from Earth, if batteries were to be used.   Are there any plausible lunar electrolyte sources which might be applied with modest industry by the 2030s?

- The illustrative Li-ion energy storage system (ESS) was placed outside the hab:  "...it was necessary to move it outside the base and to equip it with individual, passive TCS consisting of multi-layer insulation (MLI), a radiator, cold plates and heat pipes...  Due to this modification, the ESS located outside the actively temperature controlled interior no longer contributed to the base internal heat gain."  Notably, a potential advantage of an ISRU battery system in a Martian ESS / farm is found in the low power density, which allows a discharging battery to absorb / buffer far more waste heat in the greater electrolyte mass.  If a battery farm were integrated, say, in a sub-floor compartment of each Martian hab, that slow heating might be leveraged as an efficient way to help warm the hab from below, via some "radiant floor" design.  An example Aquion salt water battery (https://www.modernoutpost.com/wp-content/uploads/2017/01/Aquion_Energy_M110-LS83_M110-L083_Product_Specification_Sheet.pdf) is rated for operation to 40 C, coincidentally the temperature of a commercial radiant floor system.  When batteries are disconnected, some fraction of heat from the PV-powered hab could circulate through the same heat-exchange piping, to warm batteries as needed until evening.

Image (https://www.achrnews.com/articles/141245-hydronics-offer-unique-options-for-residential-heating):  Fast Trak radiant floor.

Refs.

Kaczmarzyk, M. and Musiał, M., 2021. Parametric Study of a Lunar Base Power System. (https://www.mdpi.com/1996-1073/14/4/1141/pdf) Energies, 14(4), p.1141.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 11/22/2021 03:00 am
No settlement would store so little energy intentionally. 

Doing agriculture in a way that requires very little stored energy doesn't mean that the settlement can't also have a lot of stored energy. There are plenty of other things one would want stored energy for.

Storing energy is a good idea, but so is minimizing the amount of stored energy you will need to survive.

(In practice, I'd think you'd want enough stored food that one "growing season" would not be survival-critical.)
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/22/2021 11:21 am
No settlement would store so little energy intentionally. 

Doing agriculture in a way that requires very little stored energy doesn't mean that the settlement can't also have a lot of stored energy. There are plenty of other things one would want stored energy for.

Storing energy is a good idea, but so is minimizing the amount of stored energy you will need to survive.

(In practice, I'd think you'd want enough stored food that one "growing season" would not be survival-critical.)

At a settlement, self-sufficient agriculture without long-term energy storage correlates with lengthy fallow seasons, and greenhouse scale potentially 10x hab scale.  That's a hard trade.

But minimizing energy requirement for settlement survival, as a lifestyle, isn't necessary.  Modern ultra-lightweight PV films and ISRU methods for energy storage can fix that problem.  Such systems deserve more creative thought in thread.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/22/2021 12:16 pm
Anyway, getting back on-topic, Tau Theory's demise is great news for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

"Good news, everyone!" :D
So, should I just refer to the rover values as a minimum solar power value, and build up from there?


I think that's a sensible baseline.


One thing that didn't come up yet was that they observed a substantial increase in dust loading right before Opportunity died. Real Mars solar arrays (which are big) will likely use electrostatic sweeping (https://www.sciencedirect.com/science/article/abs/pii/S0094576511001883) to actively remove dust buildup. Cheaper and vastly fewer moving parts than using robots or EVA-suited astronauts.

I dunno, kicking a Spot Mini with an arm out the airlock to go jiggle solar array posts when you already have one might be easier. There have been examples of a monorail robot arm running around a solar array farm adjusting motorless PV panel angle all day that ends up being cheaper than putting an active heliostat setup on each panel. Though the thought of a Spot ramming it's rear end on a post like a dog marking a tree will amuse a few people...

Spot has moving parts that wear out, unlike electrostatic cleaning.

Also you have to consider scaling. Spot may be fine for 1 acre, but what about a field of 1,000 acres?

Dunno if "jiggling the post" will even physically work. On Mars the dust electrostatically clings to the panel, so you probably either A) need to wait for a convenient dust devil, or B) need to fight fire electrostatic with electrostatic.

Also "jiggling the post" will cause additional wear on the solar panels, especially if they are using an ultra-light flexible design.

Save Spot et al for the real maintenance work, IMO.
Title: Re: Power options for a Mars settlement
Post by: Ionmars on 11/22/2021 03:47 pm

.... On Mars the dust electrostatically clings to the panel, so you probably either A) need to wait for a convenient dust devil, or B) need to fight fire electrostatic with electrostatic...."

Do we have a practical way to generate a static electric charge (+/-) across the surface of a solar panel?
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/22/2021 05:48 pm

.... On Mars the dust electrostatically clings to the panel, so you probably either A) need to wait for a convenient dust devil, or B) need to fight fire electrostatic with electrostatic...."

Do we have a practical way to generate a static electric charge (+/-) across the surface of a solar panel?
This became a focus of research because of dust cling during Apollo. In at least one case a helmet faceplate became virtually unusable. This article touches on mitigation via special coatings and applied voltage.


https://ui.adsabs.harvard.edu/abs/2010cosp...38.3645K/abstract (https://ui.adsabs.harvard.edu/abs/2010cosp...38.3645K/abstract)


I've seen papers (not immediately at hand) discussing voltages without special coatings. ISTM that PV might be a special case where it gets very tricky, but I speak from a deep well of ignorance.[size=78%] [/size]
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/22/2021 06:02 pm

.... On Mars the dust electrostatically clings to the panel, so you probably either A) need to wait for a convenient dust devil, or B) need to fight fire electrostatic with electrostatic...."

Do we have a practical way to generate a static electric charge (+/-) across the surface of a solar panel?
This became a focus of research because of dust cling during Apollo. In at least one case a helmet faceplate became virtually unusable. This article touches on mitigation via special coatings and applied voltage.


https://ui.adsabs.harvard.edu/abs/2010cosp...38.3645K/abstract (https://ui.adsabs.harvard.edu/abs/2010cosp...38.3645K/abstract)


I've seen papers (not immediately at hand) discussing voltages without special coatings. ISTM that PV might be a special case where it gets very tricky, but I speak from a deep well of ignorance.[size=78%] [/size]
A paper on a transparent film method that seems effective for solar panels.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/22/2021 06:24 pm
Do we have a practical way to generate a static electric charge (+/-) across the surface of a solar panel?

See the optimized 3D electrodynamic dust shield (EDS) of Buhler et al. 2020, with its exterior electrodes and ground.  The paper also notes ongoing integration of a 2D EDS into solar cells at Glenn Research Center. 

Also, see the 2D EDS solar panel proposal of Azure et al. 2018.  It draws 10 W/m2.

Panels angled to 10+ m get faster winds and potentially greater vibration for dust removal.  But if EDS were needed, the suggested exterior graphite storm-power collectors (https://forum.nasaspaceflight.com/index.php?topic=46533.msg1866798#msg1866798) might serve.  Conductors could be divided into two sets of ultra-lightweight circuits, one for power collection, the other for 3D EDS electrodes and ground. 

Refs.

Azure, T., Goebel, N., Huyler, C., King, L., Ostepchuk, B., Bradke, M.B.S. and Fitzhugh, U.S., Norwich Inflatable Mars Solar Array (NIMSA): An Innovative and Autonomously-Deployed Inflatable Mars Surface Solar Array. (http://bigidea.nianet.org/wp-content/uploads/2015/09/2018-BIG-Idea-Final-Paper_Norwich.pdf)

Buhler, C.R., Johansen, M., Dupuis, M., Hogue, M., Phillips, J., Malissa, J., Wang, J. and Calle, C.I., 2020. Current State of the Electrodynamic Dust Shield for Mitigation. (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwi26o7Uz6z0AhUiAZ0JHe64ALAQFnoECAUQAQ&url=https%3A%2F%2Fwww.hou.usra.edu%2Fmeetings%2Flunardust2020%2Fpdf%2F5027.pdf&usg=AOvVaw2Sd3Iz_5gGWStUsTG5zTRu) The Impact of Lunar Dust on Human Exploration, 2141, p.5027.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 11/22/2021 07:52 pm
At a settlement, self-sufficient agriculture without long-term energy storage correlates with lengthy fallow seasons,

I don't see why that's necessarily a bad thing; you would want a couple years' worth of food storage anyway.

Quote
and greenhouse scale potentially 10x hab scale.

Only if one assumes greenhouses are the primary calorie source; that's not required and maybe not even likely. There are probably more efficient means using microbes in bioreactors as the primary calorie source, ultimately processed into foods, with greenhouses for fresh fruits, vegetables, etc. (things eaten "as fresh") but not staples like wheat/corn/rice.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/22/2021 08:06 pm
and greenhouse scale potentially 10x hab scale.

Only if one assumes greenhouses are the primary calorie source; that's not required and maybe not even likely. There are probably more efficient means using microbes in bioreactors as the primary calorie source, ultimately processed into foods, with greenhouses for fresh fruits, vegetables, etc. (things eaten "as fresh") but not staples like wheat/corn/rice.

Related thoughts (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2313113#msg2313113) in the ag thread.  :-)
Title: Re: Power options for a Mars settlement
Post by: Vultur on 11/22/2021 08:17 pm
Related thoughts (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2313113#msg2313113) in the ag thread.  :-)

There is definitely cross-over between threads, but power requirements for ag are at least relevant to this thread.

That still is talking about using wheat. I think wheat, corn, etc. are really bad ideas for Mars. If the primary carbohydrate source is a plant at all, it'd probably be potatoes, but I think it might not be a plant.

I actually doubt ag will drive power requirements. Primary calorie source might be microbes working off simple organics derived from CH4 from the ISRU propellant plant; most of the energy input would be in the ISRU propellant plant rather than the ag itself.

Gardens will be important - certainly for dietary variety and fresh food, and working with a garden will probably have psychological benefits on Mars. But these will be for quality of life not for survival calories, and will probably be relatively small relative to the whole settlement and not dominate energy use. (They might be in Elon Musk's suggested surface "park" geodesic domes, like community gardens in a dense Earth city.)
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/22/2021 08:26 pm
Related thoughts (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2313113#msg2313113) in the ag thread.  :-)

I think wheat, corn, etc. are really bad ideas for Mars. If the primary carbohydrate source is a plant at all, it'd probably be potatoes, but I think it might not be a plant.

Oh, wheat is just the most productive crop by far, thanks to its unmatched ability to utilize high-intensity light.  No other crop or bioreactor comes close, to my knowledge.  Wheat's light intensity increases power draw significantly, but the calories could justify it.

Compare plot yields in the example (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2303421#msg2303421).
Title: Re: Power options for a Mars settlement
Post by: Vultur on 11/22/2021 08:59 pm
Oh, wheat is just the most productive crop by far, thanks to its unmatched ability to utilize high-intensity light.  No other crop or bioreactor comes close, to my knowledge.

That is extremely surprising if true, since wheat is pretty inefficient on Earth - rice, potatoes, etc. are much more efficient.

But what measure are we looking at? Calories per acre per year (the Earth numbers I've seen)? Calories per megajoule of light energy? Which measure is important varies depending on if you are using natural sunlight for much of the agriculture.

EDIT: also, only a small fraction of the photosynthesis energy of wheat (or any grain) can actually be used, since humans can't digest cellulose. Potatoes have a much higher percentage of total mass edible. And some microbes far higher still.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/22/2021 09:21 pm
Oh, wheat is just the most productive crop by far, thanks to its unmatched ability to utilize high-intensity light.  No other crop or bioreactor comes close, to my knowledge.

That is extremely surprising if true, since wheat is pretty inefficient on Earth - rice, potatoes, etc. are much more efficient.

But what measure are we looking at? Calories per acre per year (the Earth numbers I've seen)? Calories per megajoule of light energy? Which measure is important varies depending on if you are using natural sunlight for much of the agriculture.

Calories per m2 is one important metric, when acreage is at such a premium.

You'd rely on LED there; natural light would only supplement.  This assumes truly abundant power -- which should be assumed, and utilized, in contemporary settlement concepts, yes?

"extremely surprising if true" --  Bugbee and Salisbury 1988. (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2158746#msg2158746)   ;)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/22/2021 09:57 pm
But what measure are we looking at? Calories per acre per year (the Earth numbers I've seen)? Calories per megajoule of light energy? Which measure is important varies depending on if you are using natural sunlight for much of the agriculture.

The meaningful metric is calories per year per landed kilogram equivalent system mass. Equivalent system mass methods (https://www.sae.org/publications/technical-papers/content/2000-01-2395/) count and appropriately balance the mass of the needed power systems (solar panels, batteries, wires and interconnects), pressurized volume (pressure hull, thermal insulation, ancillary systems), thermal systems (radiators, chillers, dehumidifiers) mass input streams (water, CO2, fertilizers, minerals, compost), and — critically — labor inputs (crop tending / harvesting, machine repair, maintenance inspections, etc).

If you can actually arrive at a non-awful approximation of the equivalent system cost and optimize that instead then all the better, but usually that Jello is even harder to nail to the tree. ;)


If you're using an analysis that tries to optimize only a single variable (like energy efficiency, or pressurized volume) then your colonists are going to have a Bad Time.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 11/22/2021 10:16 pm
Calories per m2 is one important metric, when acreage is at such a premium.

Hmm... if true, I do find it rather hard to imagine that bioreactors wouldn't win.

Quote
"extremely surprising if true" --  Bugbee and Salisbury 1988. (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2158746#msg2158746)   ;)

I don't think that study shows that wheat is better than microbes in bioreactors. It seems to be primarily comparing to conventional farm growth, and even the theoretical part beginning the paper is talking about leaves, showing they're not really thinking about anything other than vascular plants.

(And even if they did make that comparison, I am not sure I would trust a 33 year old source re: ruling out bioreactors.)

You'd rely on LED there; natural light would only supplement.

I'm not even 100% sure you'd use photosynthesis primarily at all. CH4 to food organic molecules via heterotrophic microbes should also be considered IMO (and maybe someday, direct CH4 to food chemicals without biotic intervention at all).

But some of this maybe should be continued on the "Scaling Agriculture on Mars" thread, b/c it occurs to me that one's assumptions about what part of the system is developed first may make a big difference here.

Quote
This assumes truly abundant power -- which should be assumed, and utilized, in contemporary settlement concepts, yes?

I agree thin film PV means abundant power, but that's no reason to be intentionally inefficient.

The meaningful metric is calories per year per landed kilogram equivalent system mass.

I am not so sure. It very well could be, but what one should be optimizing for depends on other features of the system.

If transport via Starship is sufficiently cheap, development cost may be more important than per-kg mass transport cost.

Robustness may matter more than cost, depending on the funding source/mechanism... or if you always have say 4-6 years worth of stored food on hand, robustness may be rather low priority.

Etc.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/22/2021 10:31 pm
The meaningful metric is calories per year per landed kilogram equivalent system mass.

I am not so sure. It very well could be, but what one should be optimizing for depends on other features of the system.

If transport via Starship is sufficiently cheap, development cost may be more important than per-kg mass transport cost.

As I said, if you can get a decent handle on the equivalent system cost then more power to you. However in my experience, purported cost estimates tend to come with even more hand-waving and sneaky hidden "free lunches" than mass estimates.


Robustness may matter more than cost, depending on the funding source/mechanism... or if you always have say 4-6 years worth of stored food on hand, robustness may be rather low priority.

Etc.

"Which one is cheaper" between those two alternate scenarios is exactly the type of problem that ESM methodology was created to solve.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 11/22/2021 10:41 pm
Oh, wheat is just the most productive crop by far, thanks to its unmatched ability to utilize high-intensity light.  No other crop or bioreactor comes close, to my knowledge.

That is extremely surprising if true, since wheat is pretty inefficient on Earth - rice, potatoes, etc. are much more efficient.

But what measure are we looking at? Calories per acre per year (the Earth numbers I've seen)? Calories per megajoule of light energy? Which measure is important varies depending on if you are using natural sunlight for much of the agriculture.

Calories per m2 is one important metric, when acreage is at such a premium.

You'd rely on LED there; natural light would only supplement.  This assumes truly abundant power -- which should be assumed, and utilized, in contemporary settlement concepts, yes?

"extremely surprising if true" --  Bugbee and Salisbury 1988. (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2158746#msg2158746)   ;)
The simulated results in your reference is roughly 31 g/m2/day and 0.18 g/mol PAR for wheat, while Wheeler et al. 2019 (https://www.frontiersin.org/article/10.3389/fpls.2019.01632/full) have potatoes at 38 g/m2/day and 0.71 g/mol PAR (dry mass, i.e. more or less the same caloric density).

The relevance to this thread is that, as estimated previously, 10 kW/person should be more than enough to cover food and life support.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/22/2021 11:01 pm
Robustness may matter more than cost, depending on the funding source/mechanism... or if you always have say 4-6 years worth of stored food on hand, robustness may be rather low priority.

Etc.

"Which one is cheaper" between those two alternate scenarios is exactly the type of problem that ESM methodology was created to solve.

I didn't elaborate here, but I probably should have. The design procedure seems fairly straightforward:

Develop scenarios. Calculate cost for each scenario using ESM or similar. Calculate risk for each scenario using model-based or simulation-based analysis. Scatter plot cost vs. risk. Choose the cheapest option that meets your risk target. Iterate.

This general design procedure applies to any power load (or indeed, any service / function) on Mars, not just ag.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/23/2021 12:01 am
The simulated results in your reference is roughly 31 g/m2/day and 0.18 g/mol PAR for wheat, while Wheeler et al. 2019 (https://www.frontiersin.org/article/10.3389/fpls.2019.01632/full) have potatoes at 38 g/m2/day and 0.71 g/mol PAR (dry mass, i.e. more or less the same caloric density).

That's a creative misreading of world-record results.

Actual yield of Bugbee and Salisbury is stated plainly in their abstract:  "60 g per square meter per day".  Fig. 5.  And wheat grain has ~ 5x the energy density of a potato.

So what's the demonstrated, world-record calorie yield, and how does it compare to potatoes?

More should go in the Scaling Agriculture (https://forum.nasaspaceflight.com/index.php?topic=35877.0) thread...
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/23/2021 12:06 am
Calories per m2 is one important metric, when acreage is at such a premium.

Hmm... if true, I do find it rather hard to imagine that bioreactors wouldn't win.

You've teed the ball, so swing at it.  Which bioreactors have yield competitive with high-intensity wheat, spaceflight poster "Vultur"?

(Maybe in the Scaling Agriculture (https://forum.nasaspaceflight.com/index.php?topic=35877.0) thread.)
Title: Re: Power options for a Mars settlement
Post by: Lar on 11/23/2021 02:38 am
wheat vs potatoes in the power options thread? Yeesh.
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 11/23/2021 02:49 am
wheat vs potatoes in the power options thread? Yeesh.
Only if you are planning on ethanol for energy storage.  ;)
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/23/2021 03:47 am
wheat vs potatoes in the power options thread? Yeesh.

Come for the potatoes, stay for the survival drama.

What are your favorite ISRU energy storage methods?  The thread could use new angles there.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/23/2021 08:58 am
wheat vs potatoes in the power options thread? Yeesh.
Only if you are planning on ethanol for energy storage.  ;)

I think this gets at a really good point.

If you burn the biomass for mechanical or thermal power, the only useful energy yielded is the chemical energy contained in the material. In all cases this will be significantly less than the energy inputs required to make it.

But if you instead "store energy" by stockpiling food (vs fuel), now the "energy value" of that should rightly be compared to the energy required to make that food.

A potato containing 200 kilocalories might require 1,000 kilocalories of electrical energy to grow. If you burn it as a biofuel you only get 200 kilocalories back (less actually). If you instead offset an additional potato that you would otherwise have to grow later, you just saved yourself 1,000 kilocalories of electrical energy.

Strangely, because of this energy multiplier effect, the less energy-efficient the food production system, the more it makes sense to store energy in the form of food.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/23/2021 09:46 am
The energy multiplier effect doesn't just apply to food

Storing liquid oxygen in big tanks which double as a contingency breathing supply? You're not just storing the chemical energy contained therein, you're storing all the energy that was required to run the entire processing chain to mine, purify, electrolyze, and liquefy those atoms.

You get the same benefit if you have a big pile of bauxite you're refining into aluminum. Or perhaps you're creating in-situ plastics. Potentially anything you're producing can be energy storage.

By "making hay when the Sun shines" (with appropriate buffers of material flows), you can time-shift large amounts of energy demand by large numbers of months. The trade-off is that you have to oversize your production facilities to compensate for the anticipated downtime. If this is a few months out of 780 days (dust storms), then the percentage hit isn't too bad. Of course this means that lower capital cost systems are more favorable for energy storage.

Naturally there's an upper limit. If the energy multiplier is very high (eg microchips), then the product will be imported from Earth instead.That's energy import, not energy storage.


The sooner we fully internalize that demand shifting + stockpiling is energy storage (and should be traded & compared on a level playing field), the better off our designs will be.


Edit: thanks for coming to my TED talk. :)
Title: Re: Power options for a Mars settlement
Post by: eriblo on 11/23/2021 01:09 pm
wheat vs potatoes in the power options thread? Yeesh.
Come for the potatoes, stay for the survival drama.

What are your favorite ISRU energy storage methods?  The thread could use new angles there.
I think it is going to be hard for anything to compete with what is already included in the architecture. As has been pointed out the #1 priority of the first crew(s) will be to set up and maintain a multi GWh ISRU power-to-gas energy storage system...

Sure, electricity-methane-electricity is not especially energy efficient: 30%-38% on Earth so lets say 20% on Mars with extra overhead. But it is extremely mass efficient! Some example numbers:

Filling 1 return Starship in 1 synode: ~1 MW (avg).
10 crew @ 10 kW/person: 100 kW (avg) "base power".
Super monster dust storm scenario: No power production at all for 10% of the total time.

Shutting down propellant production and supporting 100% of base power for duration of storm => ~1% extra energy (100 kW* 78 days = ~190 MWh) needs to be stored => 5% extra total propellant production.

Pessimistic mass estimate: 500 t for solar array + propellant plant (i.e 4-5 cargo ships). 25 t extra + 1 t generator => 7200 Wh/kg.
Not as pessimistic mass estimate: 200 t, 1.e. 10 t extra + 1 t generator => 17000 Wh/kg.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 11/23/2021 02:23 pm
Per the above I think that any large scale energy storage needs are covered by the existing large scale energy storage system ( ::)), at least for the initial stages. If the plan towards self sustaining settlements holds the ratio of power used for return propellant to that used locally might decrease - more people per Starship, longer average stay, more agriculture and local industry.

However, the fraction of power that can not be curtailed during a shortage is also likely to decrease (see Twark_Mains argument) which together with local (surface-surface and surface-orbit) propellant use and propellant export could easily tilt the scale the other way.

I would not be surprised the cost of any rival energy storage technology never goes below that of methane. It would require that its efficiency weighted cost is less than 3-5 X the cost of producing the stored energy in the first place and that it arrives before uninterrupted power sources like fission/fusion.
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 11/23/2021 08:33 pm
Macgyvering another power system into the mix: Solar heat based electricity generation.


We have all seen solar water heaters which work by concentrating sunlight onto a water pipe to heat it well above ambient. The heat achieved is (mostly) determined by dwell time in the pipe, a bigger collector makes it hotter. Less known is the revolution happening in Geothermal power due to Organic Rankin Cycle generators which can use heat as low as 50C to generate electricity. My proposal is for passive solar heat collectors being used to drive the ORC.

Cons:
1) Poor efficiency
2) Only works during sunlight hours
3) Local production of plastic feedstock (ethane or formate) from local methane needs to be in place
4) Importation of plastic extrusion machines and turbines in the early years.

Pros:
1) The vast majority of the system (except the turbines) can be made from methane.
2) Maintenance consists of occasionally brushing the dust off the collectors. Everything is closed loop, passive and very few moving parts.
3) Easy to scale, adding more collectors increases the heat to the ORC and thus electricity output.
4) A complete plastic extrusion system for rain gutters fits in a panel van, a solar collector is just a different die not a different machine. This should be fairly easy to import. 3D printing dies locally adds a lot of flexibility.
5) Secondary materials like pentane and butane for the ORC are easy to make from methane, Silicone oil for the heat transfer fluid in the collectors would not freeze or sublimate and doesn't need pressure. It does need silica, chlorine and water, all of which are known Mars ISRU available materials. The amounts needed are fairly small (bench scale not factory scale) and because they are in closed loops, only need replenishment for accidental leaks. Easy to import in the early stages and all should be early targets for local chemical production capacity development.
6) There are a bunch of companies making ORC turbines in sizes from 50kW to 25MW with some like Climeon focusing on small lightweight versions. Local production of turbines would be much later in the ramp but machining capabilities able to achieve precision manufacture are likely to be a priority.
7) Easy manufacturing conditions as dust, atmosphere and gravity are mostly not factors for extruding plastics. Can be done without shelter or environmental conditioning.
8) All of the technology is high TRL today.

A side benefit of having an ORC is the amount of radiators needed for thermal management drops dramatically if the waste heat is first run through the ORC. This technique is starting to gain traction here on Earth and should have a much better payoff on Mars where activities like methane synthesis have lots of waste heat that can't just be vented. Sending the first ORC as part of the fuel plant may make solar heat collection just a bolt-on to an existing system.

TL;DR A solar heat collector system for generating electricity can be made from mostly ISRU materials very early in the capability ramp. Efficiency sucks but creating local production capacity is far far simpler on Mars than PV, wind or nukes.

Thats my Macgyver, have fun shooting it down.
Title: Re: Power options for a Mars settlement
Post by: docmordrid on 11/23/2021 10:08 pm
Have these models taken into account the differing growth times of different crop varieties? Ex  potatoes; Yukon Gold maturing in 80-100 days vs. Russets taking up to 120 days? Their culinary flexibility (Yukon's excel, but are medium starch)?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/24/2021 02:46 am
Macgyvering another power system into the mix: Solar heat based electricity generation.

...

Thats my Macgyver, have fun shooting it down.

Cons:

5) Requires constant solar tracking, unlike PV panels. For large fields this multiplies out to many moving parts.
6) Doesn't work with diffuse (scattered) sunlight, unlike PV panels. On a dusty planet like Mars this is a big deal.
7) Requires a solar collector and a radiator, unlike PV panels.

To me, it just strikes me as a strictly worse implementation of PV.


Electrostatic grid cleaning can automatically remove dust from both systems. But it means now we're comparing a completely autonomous system with zero moving parts (PV) vs. a system with thousands to millions of moving mirrors.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/24/2021 02:52 am
But I thought diffuse light counts for NOTHING! You all have betrayed me. ;)
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 11/24/2021 06:34 am
Macgyvering another power system into the mix: Solar heat based electricity generation.

...

Thats my Macgyver, have fun shooting it down.

Cons:

5) Requires constant solar tracking, unlike PV panels. For large fields this multiplies out to many moving parts.
6) Doesn't work with diffuse (scattered) sunlight, unlike PV panels. On a dusty planet like Mars this is a big deal.
7) Requires a solar collector and a radiator, unlike PV panels.

To me, it just strikes me as a strictly worse implementation of PV.


Electrostatic grid cleaning can automatically remove dust from both systems. But it means now we're comparing a completely autonomous system with zero moving parts (PV) vs. a system with thousands to millions of moving mirrors.

You are clearly not on the same page as me.

This is the "homeless guy needs a shower" version of the solar heat collector. The clear PET bottles make the black central pipes visible.
(http://www.offgridquest.com/images/today/day42/DIY-solar-heater-3.jpg)
This is the modern extruded version
(https://ecavo.com/wp-content/uploads/2019/05/2-sunbank-40-gallon-solar-water-heater-298x300.jpg?ezimgfmt=ng:webp/ngcb1)

In both pictures, the hot water feeds to a holding tank. In my proposed Mars version, hot silicon oil is fed directly to the ORC and cooled oil sent back to be heated again. No tank. Both pics make it easy to see how adding additional elements will scale the system. For Mars, a manufacturing quality somewhere between the two pictures is probably achievable. Works in overcast or dusty conditions with less output just like PV.


7) needs a radiator is a fair point against the idea. The condenser for the ORC does need to remove heat from the butane working fluid to condense it for reuse. Two important points to note here is that 1) the amount of heat to be radiated is inverse of the efficiency of the ORC (ie a 60% efficient ORC needs to drop only 40% of the heat pulled from the collector). And 2) the optimum place to radiate that heat is underneath the collector.

Electrostatic dust removal is nice but if you already have a rover that can dig ice for methane, its a really simple brush attachment to knock dust off some plastic occasionally. This design does have one required moving part in the turbine rotor in the ORC. Pumps are design optional, the modern version pictured above uses passive thermosiphon techniques which should also work on Mars.

You are correct, It is strictly worse than PV, in every single way but one.

The only way it is better is that it can be made on Mars from Martian materials shortly after Methane production is achieved. It is going to be a very long time before there is a fab churning out PV cells on Mars. This is to fill the gap.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/24/2021 02:26 pm
Macgyvering another power system into the mix: Solar heat based electricity generation.

...

Thats my Macgyver, have fun shooting it down.

Cons:

5) Requires constant solar tracking, unlike PV panels. For large fields this multiplies out to many moving parts.
6) Doesn't work with diffuse (scattered) sunlight, unlike PV panels. On a dusty planet like Mars this is a big deal.
7) Requires a solar collector and a radiator, unlike PV panels.

To me, it just strikes me as a strictly worse implementation of PV.


Electrostatic grid cleaning can automatically remove dust from both systems. But it means now we're comparing a completely autonomous system with zero moving parts (PV) vs. a system with thousands to millions of moving mirrors.

You are clearly not on the same page as me.

This is the "homeless guy needs a shower" version of the solar heat collector. The clear PET bottles make the black central pipes visible.
(http://www.offgridquest.com/images/today/day42/DIY-solar-heater-3.jpg)
This is the modern extruded version
(https://ecavo.com/wp-content/uploads/2019/05/2-sunbank-40-gallon-solar-water-heater-298x300.jpg?ezimgfmt=ng:webp/ngcb1)

In both pictures, the hot water feeds to a holding tank. In my proposed Mars version, hot silicon oil is fed directly to the ORC and cooled oil sent back to be heated again. No tank. Both pics make it easy to see how adding additional elements will scale the system. For Mars, a manufacturing quality somewhere between the two pictures is probably achievable. Works in overcast or dusty conditions with less output just like PV.


7) needs a radiator is a fair point against the idea. The condenser for the ORC does need to remove heat from the butane working fluid to condense it for reuse. Two important points to note here is that 1) the amount of heat to be radiated is inverse of the efficiency of the ORC (ie a 60% efficient ORC needs to drop only 40% of the heat pulled from the collector). And 2) the optimum place to radiate that heat is underneath the collector.

Electrostatic dust removal is nice but if you already have a rover that can dig ice for methane, its a really simple brush attachment to knock dust off some plastic occasionally. This design does have one required moving part in the turbine rotor in the ORC. Pumps are design optional, the modern version pictured above uses passive thermosiphon techniques which should also work on Mars.

You are correct, It is strictly worse than PV, in every single way but one.

The only way it is better is that it can be made on Mars from Martian materials shortly after Methane production is achieved. It is going to be a very long time before there is a fab churning out PV cells on Mars. This is to fill the gap.
I wonder about the fab question. 
https://hollandsemiconductors.nl/2021/03/11/minimal-fab-minimal-fab-small-scale-microtechnology-and-semiconductor-fab-2/
Might be easier than expected to manufacture solar cells on Mars.  They would not be as large and efficient as the ones from Earth, but probably good enough?  Not certain about a small 1/2 inch silicon boule units for wafer production, but it should be feasible.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/24/2021 03:02 pm
Ribbons might be easier than wafers if solar is the only desired product for a while.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/24/2021 03:07 pm
Ribbons might be easier than wafers if solar is the only desired product for a while.
Yes, and perhaps perovskite cells if these are buildable on a hydrocarbon material infrastructure.


Title: Re: Power options for a Mars settlement
Post by: LMT on 11/24/2021 04:23 pm
Ribbons might be easier than wafers if solar is the only desired product for a while.
Yes, and perhaps perovskite cells if these are buildable on a hydrocarbon material infrastructure.

PEN (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1934701#msg1934701) is a sturdy substrate.  At micron thickness (https://forum.nasaspaceflight.com/index.php?topic=44411.msg1947916#msg1947916), there's no need for ISRU manufacture.

If you did want to manufacture PV panels, substrate wouldn't be the hardest challenge; it's the active layer (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054602#msg2054602).  What's a plausible ISRU process for an active layer?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/24/2021 04:33 pm
Ribbons might be easier than wafers if solar is the only desired product for a while.
Yes, and perhaps perovskite cells if these are buildable on a hydrocarbon material infrastructure.

PEN (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1934701#msg1934701) is a sturdy substrate.  At micron thickness (https://forum.nasaspaceflight.com/index.php?topic=44411.msg1947916#msg1947916), there's no need for ISRU manufacture.

If you did want to manufacture PV panels, substrate wouldn't be the hardest challenge; it's the active layer (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054602#msg2054602).  What's a plausible ISRU process for an active layer?
Don't know about perovskite.  As far as silicon goes I would expect they could make the silicon boules on Mars from local silica, but get the dopants from Earth, as the required quantities will be in the kg range for decades, if not centuries.
Rare Earths, at least on Earth, tend to come in grouped mines with many similar ores.  This is unknown on Mars, but either ancient hot smokers or asteroid impacts might serve as sources for these.
I think lead based perovskites are already being phased out, but I don't know what replaces them.

Title: Re: Power options for a Mars settlement
Post by: Vanspace on 11/24/2021 05:28 pm
I wonder about the fab question. 
https://hollandsemiconductors.nl/2021/03/11/minimal-fab-minimal-fab-small-scale-microtechnology-and-semiconductor-fab-2/
Might be easier than expected to manufacture solar cells on Mars.  They would not be as large and efficient as the ones from Earth, but probably good enough?  Not certain about a small 1/2 inch silicon boule units for wafer production, but it should be feasible.

Thats a very cool fab tech.

But it completely misses the point of why it will be a long time. What is the material supply chain? A factory without a supply chain is just a fancy paperweight. A fab sits on top of a massive pyramid of supply chain steps. You can import all of the raw materials but a factory that only uses imported materials loses compared with simply importing its finished product.

Indigenous materials in the first couple synods available to Macgyver are limited:

Methane
Water
CO2
O2
Rocks

Sure silicon wafers are made out of these materials but there is a staggering number of processes involved in turning rocks into silicon boules. Those all have to be in place before a you can supply a fab from local materials. Periskovite has a lot less supply chain steps but it is still a long ways from Rocks to Persikovite Ink and we don't even know if the raw materials occur on Mars.

Turning methane directly into plastic is how most North American plastic is made today. Creating a plastic supply on Mars from an existing ISRU methane supply only needs the converter. A power system made from Martian plastic is far easier to achieve than any Martian made PV.

Title: Re: Power options for a Mars settlement
Post by: LMT on 11/24/2021 06:46 pm
Creating a plastic supply on Mars from an existing ISRU methane supply only needs the converter. A power system made from Martian plastic is far easier to achieve than any Martian made PV.

You could manufacture plastics directly from CO2 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2301269#msg2301269), and skip the waste of intermediate CH4 manufacture.

To make PV from plastics, you'd need an all-weather plastic substrate.  Common ISRU plastics would degrade very quickly under cold, UV, etc. (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025192#msg2025192)  Alternately, PEN production isn't trivial (https://patents.google.com/patent/US6040417A/en). 

All-weather plastics would seem to present a hard ISRU challenge.  Indoor plastics are easier, but limited in scale due to limited space.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/24/2021 07:14 pm
I wonder about the fab question. 
https://hollandsemiconductors.nl/2021/03/11/minimal-fab-minimal-fab-small-scale-microtechnology-and-semiconductor-fab-2/
Might be easier than expected to manufacture solar cells on Mars.  They would not be as large and efficient as the ones from Earth, but probably good enough?  Not certain about a small 1/2 inch silicon boule units for wafer production, but it should be feasible.

Thats a very cool fab tech.

But it completely misses the point of why it will be a long time. What is the material supply chain? A factory without a supply chain is just a fancy paperweight. A fab sits on top of a massive pyramid of supply chain steps. You can import all of the raw materials but a factory that only uses imported materials loses compared with simply importing its finished product.

Indigenous materials in the first couple synods available to Macgyver are limited:

Methane
Water
CO2
O2
Rocks

Sure silicon wafers are made out of these materials but there is a staggering number of processes involved in turning rocks into silicon boules. Those all have to be in place before a you can supply a fab from local materials. Periskovite has a lot less supply chain steps but it is still a long ways from Rocks to Persikovite Ink and we don't even know if the raw materials occur on Mars.

Turning methane directly into plastic is how most North American plastic is made today. Creating a plastic supply on Mars from an existing ISRU methane supply only needs the converter. A power system made from Martian plastic is far easier to achieve than any Martian made PV.
The equipment is staggeringly complex but the production steps don't seem that hard.  The problem, I've found, is that Earth tech has gone way beyond production runs of a few tonnes and is integrated into a gigantic system that can concentrate the entire planetary production of this or that into a single emplacement that produces tonnes per second.
to create small runs would require the complete recreation of a small product line.  Probably more practical to import critical elements from Earth for most things.  As far as I could find out, the boule making process was a four step process requiring not too many chemical and a lot of energy.
Another problem is who will spend a few million dollars to develop a specialized process line that will be used in 1 or 2 examples on Mars.  The business model seems terrible.
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 11/24/2021 08:43 pm
Creating a plastic supply on Mars from an existing ISRU methane supply only needs the converter. A power system made from Martian plastic is far easier to achieve than any Martian made PV.

You could manufacture plastics directly from CO2 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2301269#msg2301269), and skip the waste of intermediate CH4 manufacture.

To make PV from plastics, you'd need an all-weather plastic substrate.  Common ISRU plastics would degrade very quickly under cold, UV, etc. (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2025192#msg2025192)  Alternately, PEN production isn't trivial (https://patents.google.com/patent/US6040417A/en). 

All-weather plastics would seem to present a hard ISRU challenge.  Indoor plastics are easier, but limited in scale due to limited space.
CO2 direct to plastic is also good, maybe easier, it is just carbon chains after all. I specified the methane path mostly from familiarity and to illustrate what stage of ISRU ramp this becomes available, i e feed-stock chemical production, rovers and some infrastructure.

All weather plastic is a hard challenge. The way its often handled here on Earth is to simply accept a certain amount of continuous degradation with a shortened life cycle. If you are importing from Earth you absolutely have to have maximum life cycle. If it is being made on Mars and most importantly is replaceable from Martian materials, accepting a much shorter life cycle becomes an option. Something that will last a thousand years is better than one that needs replacing in 20 years but it may not be a good use of resources. In an earthbound example, consider greenhouses. The all weather long life option is to cover the greenhouse in glass. The cheap option is to cover it in sheets of LDPE with the expectation that it will have to be replaced every year. Where I am, most greenhouses are covered in plastic.

All weather on Earth is not the same as all weather on Mars. Water, wind, bacteria, animals and plant problems are eliminated but, as you pointed out, low temperature and UV degradation are much harder. Not to minimize the issue but my understanding is that Earth solutions for these are mostly minute amounts of additives. A small amount of imported additives is probably a good early trade off.

It is also important to note that simply sitting untouched out in the open is a much easier life cycle than plastic that is part of moving equipment. In the case of the proposed solar collector, so long as the pipe maintains integrity, the rest of the unit can have significant structural problems and still work. The lack of perfect structure is quite visible in the Homeless Guy version above.

So lack of all weather plastic is a problem that limits life cycle but does have a lot of mitigation strategies. Particularly compared to the complex problems of PV supply chains.
Title: Re: Power options for a Mars settlement
Post by: Okie_Steve on 11/24/2021 09:52 pm
Ribbons might be easier than wafers if solar is the only desired product for a while.
Yes, and perhaps perovskite cells if these are buildable on a hydrocarbon material infrastructure.

PEN (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1934701#msg1934701) is a sturdy substrate.  At micron thickness (https://forum.nasaspaceflight.com/index.php?topic=44411.msg1947916#msg1947916), there's no need for ISRU manufacture.

If you did want to manufacture PV panels, substrate wouldn't be the hardest challenge; it's the active layer (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2054602#msg2054602).  What's a plausible ISRU process for an active layer?
Don't know about perovskite.  As far as silicon goes I would expect they could make the silicon boules on Mars from local silica, but get the dopants from Earth, as the required quantities will be in the kg range for decades, if not centuries.
Rare Earths, at least on Earth, tend to come in grouped mines with many similar ores.  This is unknown on Mars, but either ancient hot smokers or asteroid impacts might serve as sources for these.
I think lead based perovskites are already being phased out, but I don't know what replaces them.

Silicon PV is a fairly mature technology that even has space heritage, but perovskite is probably the better long term bet. Lots of work with tin to replace lead as I recall.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 11/25/2021 05:49 pm
It would be very beneficial to analyse exactly how to maximise the amount of local material that can be used. It's possible that solutions never be considered on Earth might well be good solutions on Mars. For example a locally produced backing material providing strength and 80% of the mass might be bonded to an imported film coating providing UV protection and 20% of the mass. There are probably a lot of coatings, films and additives that could be coupled in this way.
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 11/25/2021 07:06 pm
It would be very beneficial to analyse exactly how to maximise the amount of local material that can be used. It's possible that solutions never be considered on Earth might well be good solutions on Mars. For example a locally produced backing material providing strength and 80% of the mass might be bonded to an imported film coating providing UV protection and 20% of the mass. There are probably a lot of coatings, films and additives that could be coupled in this way.
You can extend this. Is there a low-tech system that can be made almost exclusively from local materials, possibly including the material of the ships? Even if it's horrifically inefficient by some measure, it may be more efficient in terms of power delivered for each kilogram transported from Earth. One candidate might be solar thermal, either concentrated using stainless steel mirrors, or panels using locally-produced glass. Glass is easy, good-quality plate glass is harder. Use concentrated solar directly to melt the sand to make the glass.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/25/2021 08:53 pm
It would be very beneficial to analyse exactly how to maximise the amount of local material that can be used. It's possible that solutions never be considered on Earth might well be good solutions on Mars. For example a locally produced backing material providing strength and 80% of the mass might be bonded to an imported film coating providing UV protection and 20% of the mass. There are probably a lot of coatings, films and additives that could be coupled in this way.
You can extend this. Is there a low-tech system that can be made almost exclusively from local materials, possibly including the material of the ships? Even if it's horrifically inefficient by some measure, it may be more efficient in terms of power delivered for each kilogram transported from Earth. One candidate might be solar thermal, either concentrated using stainless steel mirrors, or panels using locally-produced glass. Glass is easy, good-quality plate glass is harder. Use concentrated solar directly to melt the sand to make the glass.
Somewhere on the site there is a more or less 200 page thread about making glass.  It's more complicated than it looks :-)
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/25/2021 08:59 pm
There is a very interesting concept in the environmental evaluation field that is called embodied energy.
You can compare products using the energy required to produce them.

https://en.wikipedia.org/wiki/Embodied_energy

Gives you an idea what to use your power on.  There is a page on Marspedia where I try to apply this to Mars.
https://marspedia.org/Embodied_energy

Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/26/2021 03:42 pm
There is a very interesting concept in the environmental evaluation field that is called embodied energy.
You can compare products using the energy required to produce them.

https://en.wikipedia.org/wiki/Embodied_energy (https://en.wikipedia.org/wiki/Embodied_energy)

Gives you an idea what to use your power on.  There is a page on Marspedia where I try to apply this to Mars.
https://marspedia.org/Embodied_energy (https://marspedia.org/Embodied_energy)
I tried an inept variation on this back in the 70's. I was working in a plant where lots of cooling water was used in one building and lots of hot water in another. We built collection and storage in the first building and pumped it over when the water heater in the other building had demand.


Not being satisfied with the traditional cost/benefit analysis (I was just a grunt with a wrench) I started thinking about an apples to apples comparison. Producing a pump = some quantity of energy + materials + shipping (which has its own resource breakdown). Then there is the capital infrastructure to make the pump which also has a resource breakdown. Digging into the supporting infrastructure could have gone back to the first proto human that struck flint to make a scraper.


My conclusion was that it quickly devolved into apples, oranges, bananas and cumquats with no clear equivalencies. All of a sudden, money made sense. An abstraction that saves a lot of calculating. Given the approximations that would go into the detailed analysis it would be roughly as accurate with the same low level of precision.


Another conclusion was that the accounting of resources itself would impose a burden on resources. Yet another conclusion was that approximating the equivalences of apples and oranges is dependent on how apples and oranges were valued at that time


The water and natural gas not consumed through recycling vs that used in producing the new system calculates differently and unpredictably over time. Fifty years ago greenhouse gasses were not considered in power production but water consumption was.


If 'the market' accurately reflects environmental costs through all dimensions of environmental concern (greenhouse, mining damage, clean water, befouled air etc), embodied energy becomes a tool for regulatory bodies instead of the corporate bean counter. With embodied factors baked into the cost, money can be the abstraction the drives the decision.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 11/26/2021 04:25 pm
Yeah, making clear glass is extremely hard and requires a LOT of ingredients:
https://youtu.be/B7lgo1LbpCs
…and you end up with a very brittle material.

I think making clear plastic is probably easier.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 11/26/2021 05:12 pm


The water and natural gas not consumed through recycling vs that used in producing the new system calculates differently and unpredictably over time. Fifty years ago greenhouse gasses were not considered in power production but water consumption was.


If 'the market' accurately reflects environmental costs through all dimensions of environmental concern (greenhouse, mining damage, clean water, befouled air etc), embodied energy becomes a tool for regulatory bodies instead of the corporate bean counter. With embodied factors baked into the cost, money can be the abstraction the drives the decision.
The modern version of your idea might be pinch analysis.  https://en.wikipedia.org/wiki/Pinch_analysis

I was hoping that we might be able to use energy use as the metric, and do without monetary evaluation.  But I expect the required human work probably derails the simple use of energy.
Title: Re: Power options for a Mars settlement
Post by: LMT on 11/26/2021 05:52 pm
Tandem solar cells (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2311200#msg2311200) could draw appreciable power from Martian storm IR.  Whereas the GaInP top sub-cell (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309185#msg2309185) in a rover's triple-junction solar cell limits current (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2310864#msg2310864) at IR wavelengths, the top tandem solar cell does not.

Note previous ultra-lightweight IR solar cell (https://forum.nasaspaceflight.com/index.php?topic=45674.msg1821848#msg1821848) experiment:  QD tech now incorporated into QD Solar devices.

Images (https://qdsolarinc.com/technology/):  Tandem solar module.  QD Solar.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/26/2021 06:17 pm
7) needs a radiator is a fair point against the idea. The condenser for the ORC does need to remove heat from the butane working fluid to condense it for reuse. Two important points to note here is that 1) the amount of heat to be radiated is inverse of the efficiency of the ORC (ie a 60% efficient ORC needs to drop only 40% of the heat pulled from the collector). And 2) the optimum place to radiate that heat is underneath the collector.

You're not getting anywhere near 60% efficiency at those temperatures. All heat engines are limited by Carnot efficiency, and an unconcentrated collector on Mars doesn't get very hot.

Putting the radiators under the panels isn't a great idea either. They're seeing the hot backside of the collector panels (or if they're insulated, the insulation temperature which should be at radiative equilibrium with the radiator panels) and the ground (which will also absorb heat from the radiator panels). The radiator panels will lose some heat to air, but they will receive low wind-speed due to their low height and the wind shadow from the collector panels.

The smaller your radiator panels are, the higher the radiator panel temperature needs to be. This hurts the Carnot efficiency.

Electrostatic dust removal is nice but if you already have a rover that can dig ice for methane, its a really simple brush attachment to knock dust off some plastic occasionally.

Not so nice when you multiply it by a huge field of panels (made even huger by the Carnot hits above) . Also brush-based removal techniques can scratch the surface and reduce light transmission.

You are correct, It is strictly worse than PV, in every single way but one.

The only way it is better is that it can be made on Mars from Martian materials shortly after Methane production is achieved. It is going to be a very long time before there is a fab churning out PV cells on Mars. This is to fill the gap.

The gap will be filled by imported panels and cells from Earth.

No sense having a "bridge" solution that takes more maintenance & raw materials and has pitiful efficiency. We can easily get trapped in a situation where the field of panels becomes so huge and inefficient that >100% of the colony's manpower and resources are required to repair and maintain it.


But I could be wrong, of course. We'd have to run the numbers. What high and low temperatures are we assuming for this system?
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 11/27/2021 04:19 am
7) needs a radiator is a fair point against the idea. The condenser for the ORC does need to remove heat from the butane working fluid to condense it for reuse. Two important points to note here is that 1) the amount of heat to be radiated is inverse of the efficiency of the ORC (ie a 60% efficient ORC needs to drop only 40% of the heat pulled from the collector). And 2) the optimum place to radiate that heat is underneath the collector.

You're not getting anywhere near 60% efficiency at those temperatures. All heat engines are limited by Carnot efficiency, and an unconcentrated collector on Mars doesn't get very hot.

Putting the radiators under the panels isn't a great idea either. They're seeing the hot backside of the collector panels (or if they're insulated, the insulation temperature which should be at radiative equilibrium with the radiator panels) and the ground (which will also absorb heat from the radiator panels). The radiator panels will lose some heat to air, but they will receive low wind-speed due to their low height and the wind shadow from the collector panels.

The smaller your radiator panels are, the higher the radiator panel temperature needs to be. This hurts the Carnot efficiency.

Electrostatic dust removal is nice but if you already have a rover that can dig ice for methane, its a really simple brush attachment to knock dust off some plastic occasionally.

Not so nice when you multiply it by a huge field of panels (made even huger by the Carnot hits above) . Also brush-based removal techniques can scratch the surface and reduce light transmission.

You are correct, It is strictly worse than PV, in every single way but one.

The only way it is better is that it can be made on Mars from Martian materials shortly after Methane production is achieved. It is going to be a very long time before there is a fab churning out PV cells on Mars. This is to fill the gap.

The gap will be filled by imported panels and cells from Earth.

No sense having a "bridge" solution that takes more maintenance & raw materials and has pitiful efficiency. We can easily get trapped in a situation where the field of panels becomes so huge and inefficient that >100% of the colony's manpower and resources are required to repair and maintain it.


But I could be wrong, of course. We'd have to run the numbers. What high and low temperatures are we assuming for this system?

High and Low Temperatures are, of course, the crux of the matter.

Real numbers to engineer a system with are at the hand waving stage, by the time it becomes feasible, real Mars numbers will be available. That said, on Earth for geothermal electric production, ORCs are available as COTS equipment for any heat source over 50C. ORCs work by vaporizing a liquid (working fluid), running a turbine to generate electricity and then condensing the now cooled gas back to a liquid. The condensing part needs to happen at low pressures and temperatures achievable in the local environment. Fundamentally, the absolute temperature does not matter so long as the temperature difference conditions are met. Over all, the Organic Rankin Cycle depends on the evaporating fluid to convert enough energy into electricity for the condensing of that fluid to require less energy than the energy produced. This condensing is usually done though dispersion of residual heat. On Earth, water (steam boiler) is the working fluid for this cycle for inlet temperatures over 100C, modern geothermal uses pentane or butane for 50C or less because they can still be condensed by evaporation coolers on a hot summer day. On the horizon a number of companies claim to have ORCs that will run off as little as 10C difference between inlet and ambient condenser heat but none that are giving delivery dates. Mars generally has much lower temperatures than Earth which may require/allow using different working fluids.

All of that said, we know for sure that a 50C inlet temperature ORC is High TRL. Lets use 50C for inlet

Outlet temperature is way harder to quantify. How much heat can you drop, at what energy cost and is that enough to condense the working fluid? "Waste heat" is not as useful a concept in a colony industrial system, there is only heat that needs to not be where it is. What if you hooked the ORC condenser to the system that adds heat to evaporate ice ore, for example. Evaporation of ice for fuel ISRU will certainly cool the ORC and reduce heat needs for the ISRU process. Is it an increase in efficiency or a net reduction? Its really hard to tell. The objection you had to putting the radiators under the heat collectors is in this same class of interconnections problems. Yes, putting the radiator under the collector reduces the efficiency of radiator heat loss by increasing the temperature of the heat collector which increases the efficiency of the collector meaning more heat for the ORC which produces more energy for less input and thus less heat needing to be dissipated. Where that conga line ends is beyond me. Nothing is for free but sometimes something is for less.

Outlet ambient heat on Earth of 20C works and Mars can get as high as 20C so lets use that. It can't be worse

A word about efficiency, I was using those numbers as an example of the inverse relationship of heat dispersion to ORC efficiency. Using different numbers, the point was even a 1% efficiency in turning heat into electricity means that you have 1% less  heat to disperse making the radiators needed smaller. An ORC is pretty close to an ideal adiabatic Carnot cycle so while it won't reach Carnot perfection, a 50 to 60% efficiency is reasonable. Mars conditions with Mars appropriate working fluids make those truly hand waving numbers at this point so I will happily accept lower efficiency values.

Absolute heat achievable by solar heating on Mars is a hard question I can't answer.

On Earth, the maximum that can be achieved by solar heating is in the range of 35-50C because above this more heat will be radiated away into Earths atmosphere than gained by the heat collected in the pipes. Water is the medium on Earth dictating the thermal properties but because of freezing and low pressures, water can't be used on Mars. Mars has much lower solar heating in general but the atmosphere is a terrible heat conductor compared to Earths. This (ironically) is why 20C atmospheric temps can be occasionally achieved on Mars. The heat loss on Mars is way lower because of the near vacuum which should allow the amount of heat retained in the system to be much higher. But the amount of heat collected in the whole system is much lower than Earth because of distance from the sun. Basically, the maximum temperature is equal to the total isolation of the collector constrained by the heat loss into the atmosphere over time. Another consideration is the heat loss overnight. If the heat loss overnight is less than the heat collected during the day, simply waiting x number of days will increase the heat to the solar isolation minus losses allowing very high absolute working heat to be achieved. Can a 50C minimum working heat be achieved? Don't know for sure but my guess is yes, particularly with multi day dwell time. My thirty five year old physics degree and pain meds mean actually putting numbers to this is beyond me. Hopefully somebody here can.

TL;DR Inlet 50C, outlet 20C, Max working heat unknown and therefor system efficiency unknown. Does the energy independence afforded by poor quality, low efficiency, short life cycle  Martian made equipment exceed the constraints of importing PV generation equipment? That needs a lot of discussion.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 11/27/2021 06:59 am


The water and natural gas not consumed through recycling vs that used in producing the new system calculates differently and unpredictably over time. Fifty years ago greenhouse gasses were not considered in power production but water consumption was.


If 'the market' accurately reflects environmental costs through all dimensions of environmental concern (greenhouse, mining damage, clean water, befouled air etc), embodied energy becomes a tool for regulatory bodies instead of the corporate bean counter. With embodied factors baked into the cost, money can be the abstraction the drives the decision.
The modern version of your idea might be pinch analysis.  https://en.wikipedia.org/wiki/Pinch_analysis (https://en.wikipedia.org/wiki/Pinch_analysis)

I was hoping that we might be able to use energy use as the metric, and do without monetary evaluation.  But I expect the required human work probably derails the simple use of energy.
The system wasn't limited to saving energy. Water was saved too. There was a counterflow heat exchanger with incoming water on the cold side and nasty post process water on the hot side. City water got preheated before entering hot water tank which has steam coils. The plant engineer said that the 'pinch' was 5 deg F.


The heated cooling water from the south building was pumped over to the north building and onto the hot water tank. I worked on the south building end and don't remember if the feed went through the heat exchanger or direct to the tank.


I'd like to claim it as my idea but like I said, I was just a grunt with a wrench. The thoughts on cost/benefit were only personal musings.


One conclusion was that money is so useful in getting past the apple/orange conundrum that ditching it would be counter productive. Any relationship that might be found between the water and energy savings on one hand, and the energy and environmental impact (pump, plumbing, wiring, tankage, labor & a surprising amount of misc) on the other, changes over time. New environmental problems are found, old ones mitigated to some degree and priorities shift.


Let the apparatchiks figure the environmental impacts and the regulatory bodies impose a carbon tax, burning river tax, dirty air tax or whatever. From that, money becomes the tool of choice. For all it's bad rap it works very well.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 11/30/2021 09:44 am
An ORC is pretty close to an ideal adiabatic Carnot cycle so while it won't reach Carnot perfection, a 50 to 60% efficiency is reasonable.

...

TL;DR Inlet 50C, outlet 20C, Max working heat unknown and therefor system efficiency unknown.

If we (optimistically) assume 60% of Carnot efficiency (η = 1 - Tcold/Thot), then that would be 3.7% efficient.

Sure enough, this graph (https://www.researchgate.net/post/Efficiency_of_Organic_Rankine_Cycle) puts the "Approximate best ORC efficiency" for those temperatures at 2.0%.
Title: Re: Power options for a Mars settlement
Post by: rakaydos on 11/30/2021 11:32 am
Anyone advocating for Kilopower is, I think, missing a trick. Not that nuclear is a bad idea, but that there should be better options.

Small Modular Reactors (https://www.energy.gov/ne/advanced-small-modular-reactors-smrs) are the closest nuclear power is going to come to COTS nuclear power. Earthside economies of scale in a form factor too big for classical space operations, but that is well within Starship's capabilities.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/05/2021 12:47 am
ISRU solar cells from Red Gold

A hypothetical ISRU PV industry requires an ISRU active layer.  Doped iron pyrite (FeS2) presently has low performance, but also potential for easy and scalable manufacturing:

Quote from: Khandaker et al. 2020
...the direct band gap can be tuned in between 2.46 and 2.72 eV using co-doping Ni@Cu in FeS2. Importantly, the absorption increases as with Ni@Cu doping in the visible and near ultraviolet regions which is an important property for optoelectronics applications. Therefore, the thin films deposited by chemical spray pyrolysis technique exhibit good structure and excellent optical properties which would be cost effective for optoelectronics, basically solar cell device applications.

Their spray pyrolysis method gives doped pyrite thin films from:

- iron chloride (FeCl2)
- copper chloride (CuCl)
- nickel chloride (NiCl2)
- thiourea (CH4N2S)

All required elements are extracted in illustrative Red Gold processes, and one pyrolysis compound is already present: hydrometallurgy CuCl (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1856108#msg1856108)

Film is ~ 380 nm thick.  Conversion is ~ 3%.  Quantum efficiency is ~ 90%.  Photocurrent is > 40 mA/cm2.

re: active layer:  What alternate active layers might be engineered from Red Gold (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1858018#msg1858018) precursors?

re: substrate:  The FeS2 thin film grew at 350 C on glass substrate.  A flexible PEN substrate has a melting point < 275 C, and could not be used.  What ISRU substrates might serve?

Refs.

Khandaker, M.R., Kamruzzaman, M., Afrose, R., Rahman, M., Khan, M.K.R., Liton, M.N.H., Helal, M.A., Anam, T.K. and Rahman, M.M., 2020. Enhanced Optical Properties of FeS 2 Using Ni@ Cu Doping and Characterization of the Structural and Chemical Compositions for Solar Cell Applications. (https://www.researchgate.net/profile/Md-Kamruzzaman-20/publication/346056682_Enhanced_Optical_Properties_of_FeS2_Using_NiCu_Doping_and_Characterization_of_the_Structural_and_Chemical_Compositions_for_Solar_Cell_Applications/links/604600ad4585154e8c842b0c/Enhanced-Optical-Properties-of-FeS2-Using-NiCu-Doping-and-Characterization-of-the-Structural-and-Chemical-Compositions-for-Solar-Cell-Applications.pdf) Crystallography Reports, 65(6), pp.968-979.
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 12/06/2021 03:46 am
An ORC is pretty close to an ideal adiabatic Carnot cycle so while it won't reach Carnot perfection, a 50 to 60% efficiency is reasonable.

...

TL;DR Inlet 50C, outlet 20C, Max working heat unknown and therefor system efficiency unknown.

If we (optimistically) assume 60% of Carnot efficiency (η = 1 - Tcold/Thot), then that would be 3.7% efficient.

Sure enough, this graph (https://www.researchgate.net/post/Efficiency_of_Organic_Rankine_Cycle) puts the "Approximate best ORC efficiency" for those temperatures at 2.0%.

Thanks, that's exactly the data we needed. Your google-fu is exceptional.

From your source cite, I was able to find the discrepancy between us.
Quote
Prof Dickes "your efficiency will depend of the heat source temperature. The maximum cycle performance you get reach is determined by the carnot efficiency (1-Tc/Th). However, as already mentionned, many irreversabilities decrease this optimum and these losses depend of the technology used for each component. Experimentally (because there is always a difference with the theoritical expectations), low-temperature ORC are typically around 5 to10% for the net efficiency. Higher values (~20-25%, even up to 30%) can be reached at nominal point with high-temperature heat source (300-350°C at the expander supply)."

I was applying efficiency for large temperature deltas in the 300C range which is completely wrong in a low temperature Martian Solar Thermal context. My bad.

Reading from the chart, in this (low) temperature range there is a mostly linear relationship between efficiency and the temperature delta across the system. A 30C difference runs at 2% while a 100C difference gives about 10%.

Which gives us some positive tentative conclusions:

1) The solar thermal system is just barely feasible under the worst case conditions as specified. Horrible 2% efficiency but not actually zero.
2) Under more typical martian conditions (ambient temperature well below freezing instead of 20C) reaching 5-6% efficiency seems likely to be achievable most days.
3) Even if solar thermal collection is not feasible, integrating an ORC into the ISRU's higher temperature thermal management systems can have some major payoffs.

Under the worst case scenario of only 30C above ambient, my concept of a solar collector is technically feasible but by itself it is likely not worth the effort. Solar PV can convert ~10 to 25% of gathered light into electricity. If Solar Thermal can convert only 2% it would require 5 to 10 times larger a collector field than an equivalent PV farm. If dusting a collector is the same effort as dusting a PV panel, the maintenance for the larger thermal system would also be correspondingly higher. If a 5-6% efficiency is achievable, installation size and maintenance drop to a much more manageable 3x that of a PV farm. I think that an indigenous low tech power system system one third as efficient needing three times the size has a path to beating 100% imported PV cells. Not in all cases but some.

At what point does the importation of PV and its associated installation/maintenance equipment equal the costs ($/Watt or Watts/kg) to import the ORC plus plastics industrial base plus installation/maintenance equipment to make solar thermal? Once that point is reached, how long will it remain true before further industrial expansion makes locally sourced PV possible? The time between these events is when a solar thermal system can make sense.

How does that change if there is already an ORC integrated into the ISRU thermal management system?

Creating and condensing thousands of tons of methalox means managing a huge amount of heat. Most methods for making ISRU methane involve heat in the 300C to 500C range that is going to require cooling. Cutting the cooling job down by 30% while getting that back as electricity is such a huge efficiency multiplier that an ORC will likely be included anyway. Compressing propellant gases to liquid creates temperatures more than 100C above ambient where an ORC can turn 10-15% back into electricity.  For all of the medium to high heat sources, there is a scale of operations at which adding an ORC to the cooling system pays off double as both electricity and reduced radiators.

ISRU propellant manufacture also has a below ambient heat sink process. At some point, a mined mix of rock and ice will have to be turned into dry rock and separated water. The heat needed for the ice to water/vapor phase change can be supplied from the ORC outlet condenser, again increasing the efficiency of both processes.

TL;DR I think the efficiency gains made possible by plumbing an ORC into the ISRU thermal management system are big enough to justify its inclusion from the beginning. It looks like my original idea of using locally made solar thermal for electricity generation on Mars is going to have terrible efficiency (thanks again T_M!) but still has a chance to be better than the alternatives in some cases.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/06/2021 05:12 pm
One further hypothetical advantage of ISRU FeS2 PV is found in the potential for an extremely thin active layer, which would cut material mass and the scale of processing.  The active layer of Khandaker et al. 2020 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2317645#msg2317645) was ~ 380 nm, but Rahman and Edvinsson 2019 anticipates < 20 nm FeS2 active layers eventually, due to very high absorption coefficient.  In contrast, many other active layers, including those of silicon, are limited to micron thicknesses.  Andreani et al. 2019.

Quote from: Rahman and Edvinsson 2019
...absorption coefficient of FeS2 is almost two orders of magnitudes higher than that of Si.  Like Si, FeS2 solar cells also could have almost same theoretical energy conversion efficiency up to Shockley-Queisser limit. Additionally, the high absorption coefficient of FeS2 offers the opportunities to fabricate a very thin absorber layer of thickness < 20 nm, which so far does not seem possible with other thin-film solar cell materials. It infers a sharp reduction of the production cost (¢/W) of electricity due to reduction of material cost.

Image:  Andreani et al. 2019, Fig. 1.

Refs.

Andreani, L.C., Bozzola, A., Kowalczewski, P., Liscidini, M. and Redorici, L., 2019. Silicon solar cells: toward the efficiency limits. (https://www.tandfonline.com/doi/full/10.1080/23746149.2018.1548305) Advances in Physics: X, 4(1), p.1548305.

Rahman, M.Z. and Edvinsson, T., 2019. What Is Limiting Pyrite Solar Cell Performance? (https://www.sciencedirect.com/science/article/pii/S254243511930306X). Joule, 3(10), pp.2290-2293.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/06/2021 07:19 pm
Compressing propellant gases to liquid creates temperatures more than 100C above ambient where an ORC can turn 10-15% back into electricity.

You'll always be better off (thermodyamically speaking) to use an intercooler (or better yet, an isothermal compressor) to avoid the heating altogether.

No free lunch. You'll never get out as much energy exergy as you lost due to using adiabatic compression vs. isothermal compression.
Title: Re: Power options for a Mars settlement
Post by: Ludus on 12/06/2021 08:08 pm
Anyone advocating for Kilopower is, I think, missing a trick. Not that nuclear is a bad idea, but that there should be better options.

Small Modular Reactors (https://www.energy.gov/ne/advanced-small-modular-reactors-smrs) are the closest nuclear power is going to come to COTS nuclear power. Earthside economies of scale in a form factor too big for classical space operations, but that is well within Starship's capabilities.
https://www.lanl.gov/discover/publications/1663/2019-february/megapower.php (https://www.lanl.gov/discover/publications/1663/2019-february/megapower.php)
Lanl did create a follow-up SMR based on Kilopower but intended for terrestrial use in remote locations and DOD has kept funding that. This could be a 5MW SMR that would fit on Starship if lanl would update the design for this purpose. Kilopower was intended for a pre-Starship, a flag and a few few footprints vision for a Mars mission.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 12/06/2021 08:09 pm
Compressing propellant gases to liquid creates temperatures more than 100C above ambient where an ORC can turn 10-15% back into electricity.
You'll always be better off (thermodyamically speaking) to use an intercooler (or better yet, an isothermal compressor) to avoid the heating altogether.

No free lunch. You'll never get out as much energy exergy as you lost due to using adiabatic compression vs. isothermal compression.
Indeed. By far the most efficient use of high grade ISRU (i.e. Sabatier) waste heat would be to run the electrolysis at elevated temperature. Most of the heat will be transferred at the boiling point of water at the various pressures the systems operate at and once below that the main concern might very well be how to reject it efficiently.
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 12/06/2021 08:13 pm
One further hypothetical advantage of ISRU FeS2 PV is found in the potential for an extremely thin active layer, which ...snip

Interesting idea, but three questions

1) Making metal chlorides from randomly scooped regolith is presumably doable but where are you getting the sulphur? Does that need a mine-able deposit or is the small amount in random dirt sufficient for the process? Seems like the S is the largest ingredient.

2) Are you sure PET must be ruled out? It looks to me like they are depositing metal vapor that is 350C but it is in a vacuum and the substrate doesn't seem to be heated. Micron thick deposition of hot metal vapor onto a cool substrate might not transfer enough heat to melt the substrate. Especially if it is a quick process.

3) Is it gold colored like regular pyrite? Because I would hate to see everything covered with tacky looking fools gold.

Title: Re: Power options for a Mars settlement
Post by: LMT on 12/06/2021 10:25 pm
One further hypothetical advantage of ISRU FeS2 PV is found in the potential for an extremely thin active layer, which ...snip

Interesting idea, but three questions

1) Making metal chlorides from randomly scooped regolith is presumably doable but where are you getting the sulphur? Does that need a mine-able deposit or is the small amount in random dirt sufficient for the process? Seems like the S is the largest ingredient.

2) Are you sure PET must be ruled out? It looks to me like they are depositing metal vapor that is 350C but it is in a vacuum and the substrate doesn't seem to be heated. Micron thick deposition of hot metal vapor onto a cool substrate might not transfer enough heat to melt the substrate. Especially if it is a quick process.

3) Is it gold colored like regular pyrite? Because I would hate to see everything covered with tacky looking fools gold.

Which illustrative Red Gold step (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1856108#msg1856108) produces copious H2S gas, reliably?

And PET would melt in the given FeS2 deposition process.  What's the duration of 350 C heating (https://www.researchgate.net/publication/346056682_Enhanced_Optical_Properties_of_FeS2_Using_NiCu_Doping_and_Characterization_of_the_Structural_and_Chemical_Compositions_for_Solar_Cell_Applications)?
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 12/06/2021 11:57 pm
Compressing propellant gases to liquid creates temperatures more than 100C above ambient where an ORC can turn 10-15% back into electricity.
You'll always be better off (thermodyamically speaking) to use an intercooler (or better yet, an isothermal compressor) to avoid the heating altogether.

No free lunch. You'll never get out as much energy exergy as you lost due to using adiabatic compression vs. isothermal compression.
Indeed. By far the most efficient use of high grade ISRU (i.e. Sabatier) waste heat would be to run the electrolysis at elevated temperature. Most of the heat will be transferred at the boiling point of water at the various pressures the systems operate at and once below that the main concern might very well be how to reject it efficiently.

Yep no free lunch anywhere but sometimes the chef will let you lick the icing off the spoon.

Sure you still have to clean the spoon (reject heat) but licking the icing (generating electricity) actually makes that easier

That reject heat just below boiling sure sounds like a heat source more than 100C over Mars standard <0C ambient. Should be tasty.

That said, I think you guys are missing the forest for the trees. We all understand that any reuse of energy is a double buff to efficiency: reduces input needed and reduces the disposal problem. Doesn't really matter if the energy that is reused is heat, electricity, kinetic or pressure. It also doesn't matter if reusing that energy turns it into a different form of energy, the double buff to efficiency is in the reuse.

The cooling cycle moving heat directly from the Sabatier unit to the heat exchanger in the electrolysis unit is just one possible path. Take the same heat and cool it by expanding pentane to pressurize a generator turbine, then condense the pentane in a heat exchanger in the electrolysis unit. The amount of heat delivered to the electrolysis unit is reduced by the amount of electricity generated, the double buff to efficiency stays exactly the same. Except that electricity is much more versatile to reuse. If, as is probably the case in Mars ISRU, the amount of heat to be ejected from the Sabatier unit is far more than the electrolysis unit can actually absorb, then any electricity generated would have an additional additive effect on efficiency by reusing more energy than would otherwise be possible in the electrolysis unit alone.

Apply it to Twarks implied spherical cow. An ISRU so perfectly thermally balanced that electricity goes in and only propellant and 95C heat comes out to be dissipated into Mars (<0C). Pass that heat through an ORC and now you have ~10% as electricity and only 85C heat to dissipate. The reduction in radiator mass needed should by itself more than cover importing the ORC turbine mass.

Integrating electricity generation into waste heat management is pretty standard on Earth. For Mars expected conditions, a closed loop system is needed and ORCs seem perfect for the sources and sinks we expect there. They have never been used in space for turbine related reasons but on a planet that isn't a problem.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/07/2021 12:32 am

Apply it to Twarks implied spherical cow.

My what now?

I don't know how you could have gotten that from anything I said.

95C heat comes out to be dissipated into Mars (<0C).  Pass that heat through an ORC and now you have ~10% as electricity and only 85C heat to dissipate. The reduction in radiator mass needed should by itself more than cover importing the ORC turbine mass.

The radiator is much larger, because it's rejecting heat at <0C (not 85C) vs. 95C before. So while it's true that there's 10% less power to reject, due to the lower temperature the radiator surface is >70% less effective per square meter.


Fun fact: the closer a machine operates to the Carnot efficiency, the larger its heat transfer surface must be. It's impossible for a machine to reach the Carnot efficiency, since the heat transfer surface would need to be infinitely large.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 12/07/2021 01:30 am

That said, I think you guys are missing the forest for the trees. We all understand that any reuse of energy is a double buff to efficiency: reduces input needed and reduces the disposal problem. Doesn't really matter if the energy that is reused is heat, electricity, kinetic or pressure. It also doesn't matter if reusing that energy turns it into a different form of energy, the double buff to efficiency is in the reuse.

The cooling cycle moving heat directly from the Sabatier unit to the heat exchanger in the electrolysis unit is just one possible path. Take the same heat and cool it by expanding pentane to pressurize a generator turbine, then condense the pentane in a heat exchanger in the electrolysis unit. The amount of heat delivered to the electrolysis unit is reduced by the amount of electricity generated, the double buff to efficiency stays exactly the same. Except that electricity is much more versatile to reuse. If, as is probably the case in Mars ISRU, the amount of heat to be ejected from the Sabatier unit is far more than the electrolysis unit can actually absorb, then any electricity generated would have an additional additive effect on efficiency by reusing more energy than would otherwise be possible in the electrolysis unit alone.

Apply it to Twarks implied spherical cow. An ISRU so perfectly thermally balanced that electricity goes in and only propellant and 95C heat comes out to be dissipated into Mars (<0C). Pass that heat through an ORC and now you have ~10% as electricity and only 85C heat to dissipate. The reduction in radiator mass needed should by itself more than cover importing the ORC turbine mass.

Integrating electricity generation into waste heat management is pretty standard on Earth. For Mars expected conditions, a closed loop system is needed and ORCs seem perfect for the sources and sinks we expect there. They have never been used in space for turbine related reasons but on a planet that isn't a problem.
All the energy in the propellant production system comes from the electrolysis.  It is thermodynamically impossible to extract more energy from that system than what the electrolysis put in.

I'm almost certain that whatever the rankine system produces as far as electricity goes, the mass of equipment required will be higher than the mass of solar cells required to produce the same amount of energy.  There's probably a breakeven point for this on Mars, but I expect that it's almost always better to add more solar cells that to over optimise the system. 
In my opinion (no calculations here) the best use for the heat, once it has been used to turn water into steam, is to go further with it and phase change the ice that's the source for the water for the electrolysis.  It should be a nice and cheap heat exchanger, with just a pump.

On Earth, you can have a gas turbine feeding a steam turbine, but once the steam is condensed, there just isn't enough efficiency left to pay for an organic Rankine cycle post treatment.  As Twark_Main mentions, the heat exchangers just get larger and larger, for less and less gain.

Interestingly, the same is true for most nuclear electric spaceships.  As the cycle efficiency gets higher, the exit temperature gets lower, the radiators get larger and eventually more efficiency reduces the overall performance.

Title: Re: Power options for a Mars settlement
Post by: eriblo on 12/07/2021 04:56 pm

That said, I think you guys are missing the forest for the trees. We all understand that any reuse of energy is a double buff to efficiency: reduces input needed and reduces the disposal problem. Doesn't really matter if the energy that is reused is heat, electricity, kinetic or pressure. It also doesn't matter if reusing that energy turns it into a different form of energy, the double buff to efficiency is in the reuse.

The cooling cycle moving heat directly from the Sabatier unit to the heat exchanger in the electrolysis unit is just one possible path. Take the same heat and cool it by expanding pentane to pressurize a generator turbine, then condense the pentane in a heat exchanger in the electrolysis unit. The amount of heat delivered to the electrolysis unit is reduced by the amount of electricity generated, the double buff to efficiency stays exactly the same. Except that electricity is much more versatile to reuse. If, as is probably the case in Mars ISRU, the amount of heat to be ejected from the Sabatier unit is far more than the electrolysis unit can actually absorb, then any electricity generated would have an additional additive effect on efficiency by reusing more energy than would otherwise be possible in the electrolysis unit alone.

Apply it to Twarks implied spherical cow. An ISRU so perfectly thermally balanced that electricity goes in and only propellant and 95C heat comes out to be dissipated into Mars (<0C). Pass that heat through an ORC and now you have ~10% as electricity and only 85C heat to dissipate. The reduction in radiator mass needed should by itself more than cover importing the ORC turbine mass.

Integrating electricity generation into waste heat management is pretty standard on Earth. For Mars expected conditions, a closed loop system is needed and ORCs seem perfect for the sources and sinks we expect there. They have never been used in space for turbine related reasons but on a planet that isn't a problem.
All the energy in the propellant production system comes from the electrolysis.  It is thermodynamically impossible to extract more energy from that system than what the electrolysis put in.

I'm almost certain that whatever the rankine system produces as far as electricity goes, the mass of equipment required will be higher than the mass of solar cells required to produce the same amount of energy.  There's probably a breakeven point for this on Mars, but I expect that it's almost always better to add more solar cells that to over optimise the system. 
In my opinion (no calculations here) the best use for the heat, once it has been used to turn water into steam, is to go further with it and phase change the ice that's the source for the water for the electrolysis.  It should be a nice and cheap heat exchanger, with just a pump.

On Earth, you can have a gas turbine feeding a steam turbine, but once the steam is condensed, there just isn't enough efficiency left to pay for an organic Rankine cycle post treatment.  As Twark_Main mentions, the heat exchangers just get larger and larger, for less and less gain.

Interestingly, the same is true for most nuclear electric spaceships.  As the cycle efficiency gets higher, the exit temperature gets lower, the radiators get larger and eventually more efficiency reduces the overall performance.
Some example numbers:

Lets say you have a good electrolyzer at 85% efficiency electricity -> hydrogen. You then lose at least another 19% (down to 66.5%) as heat when converting to methane. Even if 19% * 0.4 = 7.6% could be recovered with a very good heat engine you would only get back to ~74%.

If you instead skip the heat engine and use the heat exchangers to input heat inte the water/steam going into a SOEC you replace electrical energy directly at well above Carnot efficiency (SOECs can run at an electrical efficiency 110%). See http://www.helmeth.eu/ for a small scale (~100kg/day) proof of concept system that ran at an electricity -> methane efficiency of 76% in 2017 with an estimated industrial efficiency of >80%.
 
Title: Re: Power options for a Mars settlement
Post by: Vanspace on 12/07/2021 07:41 pm

95C heat comes out to be dissipated into Mars (<0C).  Pass that heat through an ORC and now you have ~10% as electricity and only 85C heat to dissipate. The reduction in radiator mass needed should by itself more than cover importing the ORC turbine mass.

The radiator is much larger, because it's rejecting heat at <0C (not 85C) vs. 95C before. So while it's true that there's 10% less power to reject, due to the lower temperature the radiator surface is >70% less effective per square meter.


Fun fact: the closer a machine operates to the Carnot efficiency, the larger its heat transfer surface must be. It's impossible for a machine to reach the Carnot efficiency, since the heat transfer surface would need to be infinitely large.

So if we run the system at 10,000C the radiator must become the size of a postage stamp? Obviously not despite the superb efficiency that would have. No the primary factor controlling size of a radiator is the amount of heat to be disposed, the radiator efficiency is a modifier to that base value not the base value itself. Fun Fact: If a radiator is cooling water from 100C down to 50C that means that somewhere inside that radiator is water at 75C being cooled down. If you only add 75C water the same radiator is more than capable of cooling it down to 50C.

Imagine a perfect sphere containing the entire ISRU propellant system. We need no knowledge whatsoever about how any thing works inside the sphere. We feed electricity into the sphere and all of the energy comes back out as either chemical energy in the propellant or as waste heat in the form of hot water. A given amount of electricity will produce a given amount of propellant and require 100 litres of water at 50C which will be heated to 95C in the process. We can ignore every other detail about exactly how this happens inside the sphere because we are interested in what happens from the outside. Paint a cow face on the sphere to remind you not to look inside.

First, feed the cow some electricity. Out comes propellant and the hot water.

We need to cool that water from 95C back down to 50C and pump it back into the spherical cow. We can chose the optimum efficiency and size of radiator to match the environment of the spherical cow. Now everything is perfect, the happy cow will contentedly graze on electrons and poop propellant so long as the water goes back into the cow at 50C.

Next imagine the cow gurgles and now the water coming out is only 80C. Is the radiator still able to cool the water down to 50C? Yes of course. It is now become oversized and therefor the radiator is inefficient for the amount of heat it needs to radiate but it will still cool the water correctly. Can we reduce the size of the radiator? Yes, because the total amount of heat that needs to be radiated has now become lower.

Using a spherical cow enables us to ignore specific details of how something happens and focus on where its effects occur. In the spherical cow ISRU, for any given amount of propellant produced, all efficiency improvements inside the cow no matter how its achieved will show up as some combo of either less energy consumed or lower temperature of the waste heat.

If you improve the efficiency of the IRSU by for example, cooling the Sabatier via pre-heating the water to be electrolysed, efficiency improvement will show up outside the ISRU cow as less electricity needed and/or less waste heat. The same is true for any reuse of energy within the spherical cow, the effect of all efficiency improvements must show up outside the cow in these two factors. From the outside, if the heat is reused to melt ice, reduce friction, boil pentane or spin Newton in his grave, it does not matter. If the process reuses heat to save or generate electricity, the result still looks the same from the outside.

Lets go back to our original happy cow munching electricity and making propellant. What happens if we place an ORC between the cow and the radiator? Some fraction of the heat from the cow will be turned into electricity and the rest will come out of the ORC and into the radiator. Is the radiator still large enough? Sure, because any heat turned into electricity is heat that does not go into the radiator, reducing the job of the radiator. The cow and the radiator have not changed but the efficiency of the whole cow+radiator system has improved because the electricity fed to the cow to make the same amount of propellant can be reduced by the amount generated in the ORC.


Lamontange:

You are mixing to two different systems. The energy stored in the propellant is equal to the energy put in from the electrolysis. You can not get more energy out of the propellant by burning it than is stored in it. You will always need to use more energy above and beyond what ends up in the propellant to power the process that stores energy in the propellant. That extra energy to power the process comes out of the system as heat. Reducing the amount of heat coming out of the process improves the efficiency of the propellant making process, it does not change the energy stored in the propellant.

Quote
On Earth, you can have a gas turbine feeding a steam turbine, but once the steam is condensed, there just isn't enough efficiency left to pay for an organic Rankine cycle post treatment.  As Twark_Main mentions, the heat exchangers just get larger and larger, for less and less gain.

Correct but you have the ORC in the wrong place. The ORC turbine goes where the steam turbine is, they are the same thing: a turbine powered by gas vaporized from liquid by heat. An ORC is always closed loop while a steam generator can be closed but often is run open loop, dumping used hot water and adding fresh cold water. For any type of heat powered engine you can daisy chain them together until the remaining heat is no longer enough to power another engine. Daisy chaining generators this way improves the efficiency of the whole system because more heat gets turned into electricity and thus less waste heat needs to be radiated. This trick is the whole basis of combined cycle generation setups in fossil fuel and its called double flashing in geothermal power generation. In theory, you could do this to infinity but as you note the heat exchangers between each successive engines become larger and the payoff gets smaller. In practice, two or three is about the maximum you can chain together leaving the residual heat to be disposed of in either a radiator (closed loop) or heated water (district heating from power plants is done this way).

eriblo:

Lets say you have a good electrolyzer at 85% efficiency electricity -> hydrogen. You then lose at least another 19% (down to 66.5%) as heat when converting to methane. Even if 19% * 0.4 = 7.6% could be recovered with a very good heat engine you would only get back to ~74%.

If you instead skip the heat engine and use the heat exchangers to input heat inte the water/steam going into a SOEC you replace electrical energy directly at well above Carnot efficiency (SOECs can run at an electrical efficiency 110%). See http://www.helmeth.eu/ for a small scale (~100kg/day) proof of concept system that ran at an electricity -> methane efficiency of 76% in 2017 with an estimated industrial efficiency of >80%.
 

In the first part, you show that 7.6% from the heat engine directly raises the efficiency of the combined system by 7.6%. Exactly my point.

In second part you show that using an SOEC can add even more efficiency than 7.6% all by itself. If it was an either/or choice, it wins hands down. But its not one or the other you can do both.  As a combined system getting both SOEC ~10% boost and a heat engine ~7% boost the system efficiency is ~17% higher.


Title: Re: Power options for a Mars settlement
Post by: eriblo on 12/08/2021 01:09 am
[...]
Lets say you have a good electrolyzer at 85% efficiency electricity -> hydrogen. You then lose at least another 19% (down to 66.5%) as heat when converting to methane. Even if 19% * 0.4 = 7.6% could be recovered with a very good heat engine you would only get back to ~74%.

If you instead skip the heat engine and use the heat exchangers to input heat inte the water/steam going into a SOEC you replace electrical energy directly at well above Carnot efficiency (SOECs can run at an electrical efficiency 110%). See http://www.helmeth.eu/ for a small scale (~100kg/day) proof of concept system that ran at an electricity -> methane efficiency of 76% in 2017 with an estimated industrial efficiency of >80%.
 

In the first part, you show that 7.6% from the heat engine directly raises the efficiency of the combined system by 7.6%. Exactly my point.

In second part you show that using an SOEC can add even more efficiency than 7.6% all by itself. If it was an either/or choice, it wins hands down. But its not one or the other you can do both.  As a combined system getting both SOEC ~10% boost and a heat engine ~7% boost the system efficiency is ~17% higher.
Now you are trying to have your cake and eat it too (and I think your spherical cow is licking the glazing of the other kids cakes as well...)  :)

In the example I provided the Sabatier reactor was cooled with water at elevated pressure producing steam at ~250 °C. Lets assume spherical cow reactions and processes so that all the waste heat ends up turning cooling water to steam(1). For every 1 kg of methane produced (needing 0.5 kg of hydrogen) 0.5 kg * 142 MJ/kg - 1 kg * 55.5 MJ/kg = 15.3 MJ of heat is released resulting in 15.3 MJ / 1.72 MJ/kg = 8.9 kg of steam.

Lets compare three options for a methane production of 500 kg/sol, i.e. 250 kg/sol * 142 MJ/kg = 400 kW in a perfect electrolyzer to generate the hydrogen and the Sabatier reaction generating 15.3 MJ/kg * 500 kg/sol = 86 kW of waste heat:

Run the steam through an ideal radiator(2) condensing it to water at 250 °C (4.3 kW/m2):
   86 kW / 4.3 kW/m2 = 20 m2 of radiator surface needed.

Run an ideal heat engine(3) rejecting heat through an ideal radiator at 100 °C (1.1 kW/m2) or 0 °C (0.32 kW/m2):
   Carnot efficiency 250 °C -> 100 °C : 29%. 25 kW recovered, 61 kW /  1.1  kW/m2) =  55  m2 of radiator surface needed.
   Carnot efficiency 250 °C   ->   0 °C : 48%. 41 kW recovered, 45 kW / 0.32 kW/m2) = 140 m2 of radiator surface needed.

Feed the steam to the SOEC:
   0.5 kg of hydrogen needs 4.5 kg of 8.9 kg of steam, i.e. 51%. 44 kW recovered, 42 kW of 250 °C steam left. See numbers above and divide by 2.

Caveats: (1) Unless the pressure of the steam or hydrogen flows are boosted the steam generated by cooling the Sabatier reactor can not condense the water in the hydrogen or Sabatier exhaust streams (the latter being ~1/3 of the total waste heat). This, together with all other real life losses means that the high pressure/temperature steam will roughly match the SOEC needs and that the residual waste heat will be at a lower temperature.
Using perfect black body radiators with no temperature gradients (2) and 100% efficient heat engines (3) means that the numbers are above are at best vaguely useful for relative comparisons. I expect the actual recoverable power to be at best half of this and all radiators to be significantly larger. For the low temperature case the ambient temperature will lower the efficiency even further - remember that the need for waste heat rejection scales linearly with insolation!
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 12/08/2021 01:20 am
Imagine a perfect sphere ...

Let's not.

I think people have confused you by talking about radiator "efficiency". It's a useful proxy, but what it's hiding is radiator-power. Watts per square metre.

You have a process (Sabatier) that produces a certain amount of thermal energy per hour. The radiator system needs to get rid of that thermal energy at the same rate it is produced. Therefore you need a radiator that can emit a certain number of watts of heat.

Boltzmann equation is:
Power = (emissivity)x(Boltzman's constant)x(Thot4 - Tcold4)x(Area)

So using your figures: If you reduce the hot side from 368K to 353K with the cold-side at 323K, you reduce the power of the radiator per unit area (W/m2) by around a third.

In order to radiate the same total amount of heat energy per hour, you need to increase the radiator area by 60%. Otherwise your Sabatier system can only run at 2/3rds the original rate.

That's just for a 15 degree change in input temp.

Now Carnot's equation for that same 15 degree temperate "use", gives you Efficiency = (Thot - Tcold) / Thot

So for a 15 degree temperature difference, your maximum useful work is 4%. The actual thermal-energy to electrical-energy conversion will have its own inefficiency, usually fairly high, but I'm ignoring that. 96% of the "reduction" in temperature is converted straight back to low-grade heat, which you also need to radiate at the lower temperature efficiency. So 4% reduction in "waste heat", but 96% of the overall thermal power needs to be radiated from a system requiring 1.6 times the area. Throw in a realistic energy conversion efficiency of 25%, and you get 1% of the thermal output of the Sabatier as power, at a cost of 60% increase in radiator mass and complexity.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/08/2021 07:08 pm

95C heat comes out to be dissipated into Mars (<0C).  Pass that heat through an ORC and now you have ~10% as electricity and only 85C heat to dissipate. The reduction in radiator mass needed should by itself more than cover importing the ORC turbine mass.

The radiator is much larger, because it's rejecting heat at <0C (not 85C) vs. 95C before. So while it's true that there's 10% less power to reject, due to the lower temperature the radiator surface is >70% less effective per square meter.


Fun fact: the closer a machine operates to the Carnot efficiency, the larger its heat transfer surface must be. It's impossible for a machine to reach the Carnot efficiency, since the heat transfer surface would need to be infinitely large.

So if we run the system at 10,000C the radiator must become the size of a postage stamp?

The radiator can be small, yes. Obviously other aspects of the design become unworkable though (for instance, how do you keep your radiator solid instead of a gas?).

No the primary factor controlling size of a radiator is the amount of heat to be disposed, the radiator efficiency is a modifier to that base value not the base value itself.

I don't know what you mean by "primary factor" and "modifier" and "base value." These are not mathematical or thermodynamic terms I am familiar with.

I'll I'm doing is looking at the equations. The math I outlined doesn't lie, despite whatever story you might tell yourself about which variables are "primary" or not.

Like it or not, heat engines are limited by the Carnot efficiency equation, and radiators are limited by the Stefan-Boltzmann law.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/09/2021 01:19 am

95C heat comes out to be dissipated into Mars (<0C).  Pass that heat through an ORC and now you have ~10% as electricity and only 85C heat to dissipate. The reduction in radiator mass needed should by itself more than cover importing the ORC turbine mass.

The radiator is much larger, because it's rejecting heat at <0C (not 85C) vs. 95C before. So while it's true that there's 10% less power to reject, due to the lower temperature the radiator surface is >70% less effective per square meter.


Fun fact: the closer a machine operates to the Carnot efficiency, the larger its heat transfer surface must be. It's impossible for a machine to reach the Carnot efficiency, since the heat transfer surface would need to be infinitely large.

So if we run the system at 10,000C the radiator must become the size of a postage stamp? Obviously not despite the superb efficiency that would have. No the primary factor controlling size of a radiator is the amount of heat to be disposed, the radiator efficiency is a modifier to that base value not the base value itself. Fun Fact: If a radiator is cooling water from 100C down to 50C that means that somewhere inside that radiator is water at 75C being cooled down. If you only add 75C water the same radiator is more than capable of cooling it down to 50C.

Imagine a perfect sphere containing the entire ISRU propellant system. We need no knowledge whatsoever about how any thing works inside the sphere. We feed electricity into the sphere and all of the energy comes back out as either chemical energy in the propellant or as waste heat in the form of hot water. A given amount of electricity will produce a given amount of propellant and require 100 litres of water at 50C which will be heated to 95C in the process. We can ignore every other detail about exactly how this happens inside the sphere because we are interested in what happens from the outside. Paint a cow face on the sphere to remind you not to look inside.

First, feed the cow some electricity. Out comes propellant and the hot water.

We need to cool that water from 95C back down to 50C and pump it back into the spherical cow. We can chose the optimum efficiency and size of radiator to match the environment of the spherical cow. Now everything is perfect, the happy cow will contentedly graze on electrons and poop propellant so long as the water goes back into the cow at 50C.

Next imagine the cow gurgles and now the water coming out is only 80C. Is the radiator still able to cool the water down to 50C? Yes of course. It is now become oversized and therefor the radiator is inefficient for the amount of heat it needs to radiate but it will still cool the water correctly. Can we reduce the size of the radiator? Yes, because the total amount of heat that needs to be radiated has now become lower.

Using a spherical cow enables us to ignore specific details of how something happens and focus on where its effects occur. In the spherical cow ISRU, for any given amount of propellant produced, all efficiency improvements inside the cow no matter how its achieved will show up as some combo of either less energy consumed or lower temperature of the waste heat.

If you improve the efficiency of the IRSU by for example, cooling the Sabatier via pre-heating the water to be electrolysed, efficiency improvement will show up outside the ISRU cow as less electricity needed and/or less waste heat. The same is true for any reuse of energy within the spherical cow, the effect of all efficiency improvements must show up outside the cow in these two factors. From the outside, if the heat is reused to melt ice, reduce friction, boil pentane or spin Newton in his grave, it does not matter. If the process reuses heat to save or generate electricity, the result still looks the same from the outside.

Lets go back to our original happy cow munching electricity and making propellant. What happens if we place an ORC between the cow and the radiator? Some fraction of the heat from the cow will be turned into electricity and the rest will come out of the ORC and into the radiator. Is the radiator still large enough? Sure, because any heat turned into electricity is heat that does not go into the radiator, reducing the job of the radiator. The cow and the radiator have not changed but the efficiency of the whole cow+radiator system has improved because the electricity fed to the cow to make the same amount of propellant can be reduced by the amount generated in the ORC.


Lamontange:

You are mixing to two different systems. The energy stored in the propellant is equal to the energy put in from the electrolysis. You can not get more energy out of the propellant by burning it than is stored in it. You will always need to use more energy above and beyond what ends up in the propellant to power the process that stores energy in the propellant. That extra energy to power the process comes out of the system as heat. Reducing the amount of heat coming out of the process improves the efficiency of the propellant making process, it does not change the energy stored in the propellant.

Quote
On Earth, you can have a gas turbine feeding a steam turbine, but once the steam is condensed, there just isn't enough efficiency left to pay for an organic Rankine cycle post treatment.  As Twark_Main mentions, the heat exchangers just get larger and larger, for less and less gain.

Correct but you have the ORC in the wrong place. The ORC turbine goes where the steam turbine is, they are the same thing: a turbine powered by gas vaporized from liquid by heat. An ORC is always closed loop while a steam generator can be closed but often is run open loop, dumping used hot water and adding fresh cold water. For any type of heat powered engine you can daisy chain them together until the remaining heat is no longer enough to power another engine. Daisy chaining generators this way improves the efficiency of the whole system because more heat gets turned into electricity and thus less waste heat needs to be radiated. This trick is the whole basis of combined cycle generation setups in fossil fuel and its called double flashing in geothermal power generation. In theory, you could do this to infinity but as you note the heat exchangers between each successive engines become larger and the payoff gets smaller. In practice, two or three is about the maximum you can chain together leaving the residual heat to be disposed of in either a radiator (closed loop) or heated water (district heating from power plants is done this way).

eriblo:

Lets say you have a good electrolyzer at 85% efficiency electricity -> hydrogen. You then lose at least another 19% (down to 66.5%) as heat when converting to methane. Even if 19% * 0.4 = 7.6% could be recovered with a very good heat engine you would only get back to ~74%.

If you instead skip the heat engine and use the heat exchangers to input heat inte the water/steam going into a SOEC you replace electrical energy directly at well above Carnot efficiency (SOECs can run at an electrical efficiency 110%). See http://www.helmeth.eu/ (http://www.helmeth.eu/) for a small scale (~100kg/day) proof of concept system that ran at an electricity -> methane efficiency of 76% in 2017 with an estimated industrial efficiency of >80%.
 

In the first part, you show that 7.6% from the heat engine directly raises the efficiency of the combined system by 7.6%. Exactly my point.

In second part you show that using an SOEC can add even more efficiency than 7.6% all by itself. If it was an either/or choice, it wins hands down. But its not one or the other you can do both.  As a combined system getting both SOEC ~10% boost and a heat engine ~7% boost the system efficiency is ~17% higher.
That is the clearest spherical cow description I've ever seen.


A side question. Thermocouples are used for power production in Radioisotope Thermoelectric Generators (RTG). They're light and no moving parts. Would they produce enough power to be worthwhile for that last little bit where a turbine is impractical?
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 12/09/2021 03:07 am
A side question. Thermocouples are used for power production in Radioisotope Thermoelectric Generators (RTG). They're light and no moving parts. Would they produce enough power to be worthwhile for that last little bit where a turbine is impractical?

My gut feeling is not enough power produced by rad hard thermocouples (non-rad hard would presumably be better), considering the effort NASA expended on the advanced stirling generator for newer RTG designs.

But a lot of materials science improvements in thermoelectric materials have raised ZT to tantalizingly close to usable numbers, so stacked thermoelectric generators might be viable.

Also, in some low end situations, perhaps a thermoacoustic generator may be a usable alternative. The bidirectional turbine design studied by Aster Thermoacoustics may be an interesting alternative to conventional ORC, in ranges of 100KW+, but below that linear alternator generator thermoacoustic loops may win out.

http://www.aster-thermoacoustics.com/?p=1442 (http://www.aster-thermoacoustics.com/?p=1442)

http://www.aster-thermoacoustics.com/?p=1464 (http://www.aster-thermoacoustics.com/?p=1464)

https://aip.scitation.org/doi/10.1063/1.5114369 (https://aip.scitation.org/doi/10.1063/1.5114369)

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/09/2021 10:29 am


We need to cool that water from 95C back down to 50C and pump it back into the spherical cow. We can chose the optimum efficiency and size of radiator to match the environment of the spherical cow. Now everything is perfect, the happy cow will contentedly graze on electrons and poop propellant so long as the water goes back into the cow at 50C.

Next imagine the cow gurgles and now the water coming out is only 80C. Is the radiator still able to cool the water down to 50C? Yes of course. It is now become oversized and therefor the radiator is inefficient for the amount of heat it needs to radiate but it will still cool the water correctly. Can we reduce the size of the radiator? Yes, because the total amount of heat that needs to be radiated has now become lower.

You see the scaling problem here, don't you?

The thermal power output has been reduced by 1/3rd (45 K temperature differential vs. 30 K at the same flow rate), but your radiator area can't be reduced by that much (because, physics). You lost 33% of your power, but less than 33% of your radiator area. By reducing the temperature your radiator became larger (per kilowatt of power), not smaller.


The problem is slightly easier to think/reason about if you assume the delta-T drops by half, not 1/3rd. In the full power scenario, it is trivial to see that the "halfway mark" (where the fluid has cooled half-way between the inlet and outlet temperatures) must occur less than halfway through the radiator. This is true for both radiative transfer (which follow the Stefan-Boltzmann law, P ∝T4), or conductive/convective losses (which follow Newton's Law of Cooling, P ∝ T1). In fact, this will always be true whenever the cooling rate has a direct relationship (https://www.rcsdk12.org/cms/lib/NY01001156/Centricity/Domain/4574/Graphing%20Relationships.ppt) with the temperature difference between fluid and ambient.

So again, we lost half our power, but less than half our radiator area. This is *not* a win.



"In this house we obey the laws of thermodynamics!"
Title: Re: Power options for a Mars settlement
Post by: _MECO on 12/09/2021 02:52 pm
You know, I'm barging into this thread after probably a dozen or more pages of not being in on the conversation so apologies if this is irrelevant or OT. But stupid thought: We're all arguing about using radiators to reject waste heat because there's basically no air to convect waste heat into, right? Everyone's going and talking about fourth power radiation laws like the first Mars base is going to have gleaming orange Children of a Dead Earth-style panels all over the place. (I will maintain that a big field of lower temperature radiators will be simpler and easier to maintain in the long run than say a smaller patch of much angrier NaK panels by the way, but I digress.)

Let's suppose that the first Mars base was established at a cold trap, like Korolev Crater. Why can't a nuclear plant's waste heat be rejected to a convecting heat exchanger, rather than a radiating one? A number of coolant pipes could be submerged in a melt pool which has been formed by said heat exchanger. As the water takes heat out of the pipe and warms, it melts additional ice which can be pumped into the base for ISRU and living purposes. There's already going to be a huge demand for water because of ISRU propellant production. It might be a little complicated to set up but hey, it is a nuclear plant on Mars. The step one solar panels and step two Kilopower reactors have probably already been done by this point.

So nuclear at the present moment is completely unreasonable (if only for political reasons.) No one, and especially not the NRC or the NNSA, are going to be handing SpaceX giant piles of fissile material and telling them to have a nice day in the near future. I mean, they did already ask. But should a nuclear plant actually exist in a future more developed station, I don't see why that heat can't still be put to some use even if it's no longer economical or practical to continue to extract work from it.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 12/09/2021 04:49 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
Title: Re: Power options for a Mars settlement
Post by: _MECO on 12/09/2021 08:33 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
You don't need to reject the heat all the way to the surface through the ice, you pump it into your base as soon as it's melted and warm. That way you can use it for whatever warm or hot water gets used for, and if there's excess you can just spray it somewhere (like onto the top of the ice, which is I suppose what you're saying anyways.)
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/09/2021 11:58 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
If exposed, wouldn't there be additional cooling from sublimation?


Sublimation rubs the wrong way unless there is a LOT of water. Precious resource etc. Maybe it would be a first terraforming step. Now that would be a modeling job and a half.
Title: Re: Power options for a Mars settlement
Post by: LMT on 12/10/2021 03:09 am
Sondelski and Nellis 2019 applies ISRU CO2 to a simulated Martian reactor cooling system.

Quote from: Sondelski and Nellis 2019
Highlights:

•  Neutronic limitations result in reactor mass relatively independent of power level.

•  Radiator is largest component leading to desire for high heat rejection temperature.

•  Increasing turbine inlet temperature from 900 K to 1120 K decreases mass by 47%.

•  Optimal compressor suction state is closer to ideal gas than supercritical region.

•  Improvement of radiator mass to panel area ratio could decrease cycle mass by 50%.

Notes:

- Inconel improves on stainless steel re: radiator panel area, mass flow rate, working temperatures, and system mass.  Table 3.

- "...the compressor suction state point is quite far from the supercritical region for CO2 due to the need for a high radiator temperature. Therefore, the typical benefits of using a [supercritical CO2] system are not realized in this application, and a working fluid with a higher critical temperature may provide better cycle efficiency and therefore lower overall mass."

Refs.

Sondelski, B. and Nellis, G., 2019. Mass optimization of a supercritical CO2 Brayton cycle with a direct cooled nuclear reactor for space surface power. (https://www.sciencedirect.com/science/article/am/pii/S135943111932719X) Applied Thermal Engineering, 163, p.114299.
Title: Re: Power options for a Mars settlement
Post by: _MECO on 12/11/2021 10:12 am
Sondelski and Nellis 2019 applies ISRU CO2 to a simulated Martian reactor cooling system.

Quote from: Sondelski and Nellis 2019
Highlights:

•  Neutronic limitations result in reactor mass relatively independent of power level.

•  Radiator is largest component leading to desire for high heat rejection temperature.

•  Increasing turbine inlet temperature from 900 K to 1120 K decreases mass by 47%.

•  Optimal compressor suction state is closer to ideal gas than supercritical region.

•  Improvement of radiator mass to panel area ratio could decrease cycle mass by 50%.

Notes:

- Inconel improves on stainless steel re: radiator panel area, mass flow rate, working temperatures, and system mass.  Table 3.

- "...the compressor suction state point is quite far from the supercritical region for CO2 due to the need for a high radiator temperature. Therefore, the typical benefits of using a [supercritical CO2] system are not realized in this application, and a working fluid with a higher critical temperature may provide better cycle efficiency and therefore lower overall mass."

Refs.

Sondelski, B. and Nellis, G., 2019. Mass optimization of a supercritical CO2 Brayton cycle with a direct cooled nuclear reactor for space surface power. (https://www.sciencedirect.com/science/article/am/pii/S135943111932719X) Applied Thermal Engineering, 163, p.114299.
A supercritical Brayton plant? That's a new one. At what point does a Brayton cycle become a Rankine cycle here? I'd love to see a diagram of the saturation dome for CO2. And a T-S for that power plant concept.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/17/2021 01:07 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
If exposed, wouldn't there be additional cooling from sublimation?


Sublimation rubs the wrong way unless there is a LOT of water. Precious resource etc. Maybe it would be a first terraforming step. Now that would be a modeling job and a half.

I don't think it would work if the melt pool was exposed to ambient Mars pressures. The water would sublimate directly from a solid to a gas.

Has anyone ever made a pressurized Rodwell before? Seems potentially risky...
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/17/2021 06:53 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
If exposed, wouldn't there be additional cooling from sublimation?


Sublimation rubs the wrong way unless there is a LOT of water. Precious resource etc. Maybe it would be a first terraforming step. Now that would be a modeling job and a half.

I don't think it would work if the melt pool was exposed to ambient Mars pressures. The water would sublimate directly from a solid to a gas.

Has anyone ever made a pressurized Rodwell before? Seems potentially risky...
A rod well, IIU the way your using the term is a lift pump system. On oil rigs the target is usually pressurized and the hard part is making it stop spewing. Once they get it capped they literally go with the flow for delivery.


The pressure goes down during the extraction process and eventually they move to lift pumps, which would be the rod well I think you're speaking of. I see no reason a mars water well would be much different.
Title: Re: Power options for a Mars settlement
Post by: rsdavis9 on 12/17/2021 07:29 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
If exposed, wouldn't there be additional cooling from sublimation?


Sublimation rubs the wrong way unless there is a LOT of water. Precious resource etc. Maybe it would be a first terraforming step. Now that would be a modeling job and a half.

I don't think it would work if the melt pool was exposed to ambient Mars pressures. The water would sublimate directly from a solid to a gas.

Has anyone ever made a pressurized Rodwell before? Seems potentially risky...
A rod well, IIU the way your using the term is a lift pump system. On oil rigs the target is usually pressurized and the hard part is making it stop spewing. Once they get it capped they literally go with the flow for delivery.


The pressure goes down during the extraction process and eventually they move to lift pumps, which would be the rod well I think you're speaking of. I see no reason a mars water well would be much different.

No "rodwell" is a drilling method in solid glacier ice. Pump in hot water and get a hole and more water.
https://www.erdc.usace.army.mil/Media/Images/igphoto/2002471429/
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 12/18/2021 05:34 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
If exposed, wouldn't there be additional cooling from sublimation?


Sublimation rubs the wrong way unless there is a LOT of water. Precious resource etc. Maybe it would be a first terraforming step. Now that would be a modeling job and a half.

I don't think it would work if the melt pool was exposed to ambient Mars pressures. The water would sublimate directly from a solid to a gas.

Has anyone ever made a pressurized Rodwell before? Seems potentially risky...
A rod well, IIU the way your using the term is a lift pump system. On oil rigs the target is usually pressurized and the hard part is making it stop spewing. Once they get it capped they literally go with the flow for delivery.


The pressure goes down during the extraction process and eventually they move to lift pumps, which would be the rod well I think you're speaking of. I see no reason a mars water well would be much different.

No "rodwell" is a drilling method in solid glacier ice. Pump in hot water and get a hole and more water.
https://www.erdc.usace.army.mil/Media/Images/igphoto/2002471429/ (https://www.erdc.usace.army.mil/Media/Images/igphoto/2002471429/)
Got it thanks. ISTM the initial bore then the cavity creation would need to be vented. Once there's a cavity giving buffer space it could be sealed off and allowed to self pressurize. Gets rid of the pump and allows heat input to control delivery rate.


The pressurization would not have to be all that great. On Mars one bar pressure would give ~26m head.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 12/18/2021 06:03 pm
Sure, a giant meltpool inside a convenient glacier works as a cheap solution to waste heat. However, eventually the pool will have to reject heat to the surface at which point it is just a cheap ISRU radiator with a very large time lag...
Assuming a 33% nuclear reactor and an 80% efficiency of power to methane (ignoring all ISRU processing, cooling or other base needs) you get:

270 t * 55.5 GJ/t / 0.8 * 2 Jth/Je / 0.33 GJ/t = 114000 t of melted ice (a 60 m diameter sphere) per fully refueled Starship.

That is a bit more than the expected water needs ;)
If exposed, wouldn't there be additional cooling from sublimation?


Sublimation rubs the wrong way unless there is a LOT of water. Precious resource etc. Maybe it would be a first terraforming step. Now that would be a modeling job and a half.

I don't think it would work if the melt pool was exposed to ambient Mars pressures. The water would sublimate directly from a solid to a gas.

Has anyone ever made a pressurized Rodwell before? Seems potentially risky...
A rod well, IIU the way your using the term is a lift pump system. On oil rigs the target is usually pressurized and the hard part is making it stop spewing. Once they get it capped they literally go with the flow for delivery.


The pressure goes down during the extraction process and eventually they move to lift pumps, which would be the rod well I think you're speaking of. I see no reason a mars water well would be much different.

No "rodwell" is a drilling method in solid glacier ice. Pump in hot water and get a hole and more water.
https://www.erdc.usace.army.mil/Media/Images/igphoto/2002471429/ (https://www.erdc.usace.army.mil/Media/Images/igphoto/2002471429/)
Got it thanks. ISTM the initial bore then the cavity creation would need to be vented. Once there's a cavity giving buffer space it could be sealed off and allowed to self pressurize. Gets rid of the pump and allows heat input to control delivery rate.


The pressurization would not have to be all that great. On Mars one bar pressure would give ~26m head.

The point isn't the provide pressure head. The point is to keep the water liquid.

Rodriguez wells rely on the pool of liquid water to transfer heat from the heating element and melt the frozen walls. Can you even initially make a "cavity" without it?

Furthermore, 1 bar of pressure is pretty dangerous. There's gonna be a lot of stored explosive energy inside that well, just waiting for the right hairline fracture...

Rather than going to 1 bar (100 kPa), I expect the rodwell would be kept at 3-10 kPa. This results in a water boiling point of 20-50 °C.
Title: Re: Power options for a Mars settlement
Post by: wes_wilson on 08/01/2022 02:34 pm
US regulators are certifying the first small modular reactor design.
https://arstechnica.com/science/2022/07/us-regulators-will-certify-first-small-nuclear-reactor-design/

https://www.nuscalepower.com/technology/technology-overview
Slightly larger than Starships payload bay; each module is overweight too at just over 200 tons.  Would have to be broken down more for shipping. 

Refueling cycle is every 24 months which is a convenient number for Mars. 


Title: Re: Power options for a Mars settlement
Post by: BT52 on 08/01/2022 04:16 pm
Theoretically could Mars had own nuclear ore?
Title: Re: Power options for a Mars settlement
Post by: wannamoonbase on 08/01/2022 07:08 pm
US regulators are certifying the first small modular reactor design.
https://arstechnica.com/science/2022/07/us-regulators-will-certify-first-small-nuclear-reactor-design/

https://www.nuscalepower.com/technology/technology-overview
Slightly larger than Starships payload bay; each module is overweight too at just over 200 tons.  Would have to be broken down more for shipping. 

Refueling cycle is every 24 months which is a convenient number for Mars. 




I believe the size of the approved reactor is approximately 77 MW.  That is a great deal more than any early or mid size settlement would need. 

I think nuclear is the only good option for settlement baseload.  But they only need a small reactor to get going.  Perhaps 2 for redundancy.  So maybe something like two  5 or 10 MW reactors to get started. 

It also needs to be run a low enough level that it can support the smallest settlement.
Title: Re: Power options for a Mars settlement
Post by: alastairmayer on 08/01/2022 09:47 pm
Theoretically could Mars had own nuclear ore?

Possibly. On Earth, uranium (and thorium) ores tend to be hydrothermal deposits or other igneous/metamorphic rocks.  We know Mars has had both water and volcanic processes, so such deposits are likely  Whether uranium/thorium bearing ores actually exist in accessible locations is another question.
Title: Re: Power options for a Mars settlement
Post by: LMT on 10/12/2022 09:27 pm
"Here’s the TENG: a battery-free breakthrough" (https://www.australianmining.com.au/news/heres-the-teng-a-battery-free-breakthrough/)

Quote
"New Curtin University-led research has found a more effective way to improve the output of autonomous power sources, such as triboelectric nanogenerators (TENGs), commonly used to power vital mining equipment in remote or underground locations where power points and batteries are not practical.

The research found that using silicon on the surface of the autonomous power sources, without having to rely on plastic surfaces likes previous models, could dramatically increase both the voltage and duration of the output, enabling equipment to be kept charged for up to 10 times longer...

'When you are in a remote location, or perhaps underground and don’t have access to traditional power sources, we need to ensure there is another form of power that we can rely on...'"

Source:  "Sliding Schottky diode triboelectric nanogenerators with current output of 10^9 A/m2 by molecular engineering of Si(211) surfaces" (https://www.sciencedirect.com/science/article/abs/pii/S2211285522007364)

Quote
"...by achieving molecular control of oxide-free Si crystals and using conductive atomic force microscopy, we address key open questions and use this knowledge to demonstrate zero-applied-bias current densities as high as 10^9 A/m2."

Refs.

Lyu, X., Ferrie, S., Pivrikas, A., MacGregor, M. and Ciampi, S., 2022. Sliding Schottky diode triboelectric nanogenerators with current output of 109 A/m2 by molecular engineering of Si (211) surfaces. Nano Energy, 102, p.107658.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:26 am

Ag can tarnish in martian (trace) O2 and H2S, but here it's covered by WS2 and Au; not exposed to the elements.  Likewise, Ag in the previously noted (https://forum.nasaspaceflight.com/index.php?topic=39785.msg1954068#msg1954068) solar cells.

WS2 is an inert spacecraft lubricant.

"Exotic"?
Molybdenum Disulphide ("Moly") is indeed a common solid lubricant, frequently in vacuum applications. It has a layered structure quite like graphite.
Tungsten Silicide I've heard of being used for semiconductor conductor layers on chips.

I'm not sure I've ever heard of tungsten disulphide being used for anything.  :(
It's available from Amazon - its used as a high temperature lubricant.
https://www.amazon.com/MICROLUBROL-TUNGSTEN-DISULFIDE-Sulfide-Powder/dp/B00WP4306U (https://www.amazon.com/MICROLUBROL-TUNGSTEN-DISULFIDE-Sulfide-Powder/dp/B00WP4306U)
That's something I didn't know.  It's that common SoP/Actual SoA divide. MoS2 is widely known and in common use but WS2 is available as an option.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:30 am

I wonder about the fab question. 
https://hollandsemiconductors.nl/2021/03/11/minimal-fab-minimal-fab-small-scale-microtechnology-and-semiconductor-fab-2/
Might be easier than expected to manufacture solar cells on Mars.  They would not be as large and efficient as the ones from Earth, but probably good enough?  Not certain about a small 1/2 inch silicon boule units for wafer production, but it should be feasible.
Highly doubtful and certainly not anytime soon.

Heating and melting silicon takes a staggering amount of energy.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 06:52 pm

Private companies really can't develop a pebble bed or traveling wave or dissolved-fuel molten salt reactor in the United States. The magic of Kilopower is that it's a NASA project, and as a government agency, they can develop a sodium-cooled reactor with a high-enriched metallic uranium core. NASA can get their hands on that stuff, and with it they can develop a reactor that runs for 20+ years on a single fuel load.
The prototype version is HEU, but they are going to 19% HALEU for the final version, provided they can find a supplier for that given commercial fuel fabricators are only licensed up to 5% before criticality problems surface

And most people would not describe it as "sodium cooled." That implies a sodium cooling loop whereas in fact it uses a set of individual heat pipes to drive Stirling geneators. Sodium loops are a PITA but if a heat pipe (or SG) fails the system can self-adapt.

As for claims that the US will only allow reactors to use UO2 fuels  I doubt that. But if true so what?

Uranium oxide fuel melts at 2500c/4532F and Zirconium alloys around 1800c./3272F.

In fact  the biggest drawback to water cooled/moderated reactors from running at much more efficient temperatures is the water itself Even the SA508 standard steel for RPV's can operate continuously at 350c.

In the early 50's the use of water as a combined moderator/coolant for submarine power systems in the 60MW range might have been a stroke of genius.  Making Zirconium work as a cladding (commerical zirconium has quite a high thermal neutronn cross section due to the 2% Hafnium in it. It took a while for that to be realized) was AIUI drive by Admiral Rickover himself.

What these materials have is enormous pedigree. The challenge is to incorporate them into a new design (preferably one with natural uranium, as the 1st generation UK/French/Russian and CANDU designs used).

It would also be a good idea to produce steam at the standards of the 8000+ conventional fuel steam turbines, not the 389 LWR/HWRs to leverage the considerably better pricing for conventional steam turbines (about 10x cheaper has been claimed).

That said I don't think any power plant on mars will be producing "waste" heat for a looooong time. The settlers will find a use for every BTU of output somehow.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 06:56 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.
Indeed. Fusion changes everything everywhere.  But for now.....

I'd like to put in a word for geothermal. There's still heat in them-there rocks.  :) It's not running out and it's available 24/7. You'll need a low BP fluid to drive a turbine, but it is an option.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 06:59 pm
Agreed, although turning off fuel and food production for the duration of a storm would reduce demand to a small fraction of the peak load.  An extra Martian winter in a way.
And how long do storms on Mars last?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:07 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.

I would think some big methane/oxygen fuel cells would be appropriate once things get going. You will be making tons of the stuff anyway. This would be in place of batteries and for times like dust storms.
Depends what the efficiency is. You end up with CO2 and H2O and heat again. So will you get more electricity this way than just running an ICE or a turbine?

If not you've just put yet another complex, possibly impossible to maintain (with Martian resources) system into the settlements critical path.  :(

IOW if you can't make the parts on mars you have to buy, and ship them from Earth. That's fine if you don't buy the "lifeboat" concept and assume the earth supply chain will always be there.

Provided of course that the settlement has some way to generate those funds to buy and ship  that hardware.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/28/2023 07:10 pm
Agreed, although turning off fuel and food production for the duration of a storm would reduce demand to a small fraction of the peak load.  An extra Martian winter in a way.
And how long do storms on Mars last?
depends, but not much longer than a Canadian winter.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:14 pm
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?
Kilopower is a nice "bite-size" for ion thrusters on space probes, or orbital radar sensors.

You'll either need the bigger-than-baseline model IE 100kw or MW, ¬10Kw unit, or (what people forget about Kilopower)  you can cluster them.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/28/2023 07:15 pm
Seems like the power options for Mars boil down to shed loads of solar panels and batteries perhaps supplemented with some kilopower units for base load and emergency backup during sand storms.
That's how I see it until the mythical fusion power shows up. It seems reasonable expect to see some interesting technology to optimize systems for power efficiency but that can only go so far.

I would think some big methane/oxygen fuel cells would be appropriate once things get going. You will be making tons of the stuff anyway. This would be in place of batteries and for times like dust storms.
Depends what the efficiency is. You end up with CO2 and H2O and heat again. So will you get more electricity this way than just running an ICE or a turbine?

If not you've just put yet another complex, possibly impossible to maintain (with Martian resources) system into the settlements critical path.  :(

IOW if you can't make the parts on mars you have to buy, and ship them from Earth. That's fine if you don't buy the "lifeboat" concept and assume the earth supply chain will always be there.

Provided of course that the settlement has some way to generate those funds to buy and ship  that hardware.
The cost of transportation favors local production.  In all fields.  On Earth it’s Pennie’s per kg so production can be distributed but at 100+ dollars per kg to Mars you can produce fairly expensively and still be competitive.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/28/2023 07:18 pm
What about kilopower? Wouldn't this be a very good option as base load and emergency power for the first mission at least?
Kilopower is a nice "bite-size" for ion thrusters on space probes, or orbital radar sensors.

You'll either need the bigger-than-baseline model IE 100kw or MW, ¬10Kw unit, or (what people forget about Kilopower)  you can cluster them.
Wonder if it’s cheaper to cluster kilo power or to develop mega power?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:29 pm
I assume that base load is that necessary to keep minimum necessary systems running. Things like light, heat, communications, air circulation, electronics cooling, CO2 scrubbing and food prep. Maybe a few other things like agricultural tests that would loose a lot if they had to start over. Does ISS consumption teach us anything about how much this might be or are the conditions so different that a comparison is useless?
Quite a lot actually in terms of ECLSS. But at settlement scale "CO2 scrubbing" with canisters of lithium hydride is not going to cut it. You're a base, not a settlement  :(

Also mars has an unrecognised natural resource.

Gravity.

Which means you can get air circulation by thermal effects and separation without needing a centrifuge, among other useful effects
Quote from: OTV
Is an electrical budget of 1kW/day/person anywhere near the mark? If so, a 10kW kilopower would support a crew of 10 indefinitely, but with no reserves.
Well ISS is a 200Kw array supporting 7 crew (but a lot of experiements). So thats 28Kw/person. But the relevant metric is Kilowatt Hours. So you'd be talking about 24 KwH of capacity, assuming 24/7/365 production of 1Kw, which is feasible for Kilopower systems.

You might look at what the power line into a typical american home is.  You might be surprise at its capacity.


Quote from: OTV
A quick check of the Oracle shows nothing new on Kilopower since the March 2018 KRUSTY tests. Anybody have a pointer to anything newer?
BWX, IE what was Babcock Wilcox, who were one of the big 3 US LWR mfg, are working on it.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:35 pm
One piece of information I believe is useful for the current line of discussion is the discovery that Martian temperatures increase during dust storms.  This means lower than normal power requirements are needed for heating.

Quote
The impact of Mars's 2018 Global Dust Storm (GDS) on surface and near-surface air temperatures was investigated using an assimilation of Mars Climate Sounder observations. Rather than simply resulting in cooling everywhere from solar absorption (average surface radiative flux fell 26 W/m2), the globally averaged result was a 0.9-K surface warming. These diurnally averaged surface temperature changes had a novel, highly nonuniform spatial structure, with up to 16-K cooling/19-K warming. Net warming occurred in low thermal inertia regions, where rapid nighttime radiative cooling was compensated by increased longwave emission and scattering. This caused strong nightside warming, outweighing dayside cooling. The reduced surface-air temperature gradient closely coupled surface and air temperatures, even causing local dayside air warming. Results show good agreement with Mars Climate Sounder surface temperature retrievals. Comparisons with the 2001 GDS and free-running simulations show that GDS spatial structure is crucial in determining global surface temperature effects.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL083936
Which implies where you are has a big difference on how cold you get.

No indication what that does to insolation of PV arrarys however.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:39 pm
Power requirements during a dust storm can be quite low, because you can use stored consumables instead of power-hungry closed loop life support.

No need to generate breathing oxygen, since you can just draw oxygen directly from tanks.

No need to generate potable water or food. Both can be stockpiled in ample amount.

No need to desorb CO2 either (ala the ISS CDRA). Simple one-use LiOH canisters would only mass 7 kg per person per month.* These canisters could be regenerated and re-stockpiled after the dust storm by heating them and exposing them to vacuum.




* this should be treated as a conservative estimate, since my baseline is ancient: the Apollo CM canisters weighed 13 oz and supplied 3 people for 12 hours
Provided of course you have anaged to stockpile enough consumables to cope with the actual length of storm.

Otherwise everybody dies.  :(

NASA has done a lot of work on requirements to support a person in terms of ECLSS, a lot of devoted to trips to mars as it happens.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:47 pm
There is enough energy in the martian wind to keep dust suspended for months. Is it possible to design a practical wind turbine to use that energy? The wind turbines would probably not be useful much of the time, but they might be useful precisely when the solar panels are least useful.
IIRC JPL looked into this in the 70's. It is possible, the atmospheric density being 1/140 that of earth sea level the wind speed needs to be a lot higher. In crude terms we're looking at air molecules driving the blades by hitting them.

With 1/140 of the usual level of molecules they are going to have to be moving quite a bit faster to excert enough force. OTOH this is mars. Everything weighs 1/3, so the force you need to get an earth turbine moving is 3x lower on mars.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:53 pm
I doubt any have been built but if a turbopump (not FFSC type) can run  on CH4+O2, it looks doable. Worst case, CO2 might be a workable stand in. Water injection might even have some advantages and can be condensed out for reuse.
Anyone GG methalox rocket engine will be doing this. The fact that AFAIK no one makes a big song-and-dance about doing such a thing indicates it's not just within the SoA, it's well within the standard design skills you should expect of people with the relevant engineering degrees.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 07:57 pm

Eribo is correct overall, and you specifically.  The Sabatier on its own gives out energy (is exothermic) but as it is fed by the electrolysis, that requires a huge energy input, the pair of reactions loses energy overall.  As hydrogen and oxygen are not available on their own on Mars, the complete reaction is the reaction pair, electrolysis+ Sabatier, that loses thermal energy.  The overall system is the system of interest, from the point of view of power generation of the Martian settlement.

In other words 1 J of solar or nuclear energy transformed into methane gives 0,78 J available in the methane and oxygen and 0,22 J as heat, in a perfect reaction.  The actual energy available will be lower due to inefficiencies.
On earth, this is a bad thing, but on mars, being so damm cold,  that "waste heat" has value.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 08:04 pm

Yes, but the system as a whole must be oriented toward production and long-term storage of methane and oxygen for use as propellant, so it will already be optimized for that. My guess is that using this resource as needed for second-level electrical backup will be cheaper than adding a system that must store a large amount of hydrogen. At scale, hydrogen storage is a lot harder than methane storage. Spend the capital on expanding your solar, battery, and methane/oxygen storage. That gives you more methane/oxygen production in the first place and less need to use it to produce electricity (fewer hours/year of empty battery) I don't know what the electrcity==>gasses==>electricity  round-trip efficiency will be, but it will be good enough.
True.

This comes up in proposals for hydrogen powered cars.  Basically there are 3 ways to do it.
1)Pressurise GH2. This typically targets 5000Psi. 2)Cool it to boiling point (-397F i think) 3)Absorb onto metal alloys.

1 & 2 use about 3x as much energy to make the conversion as in the orginal mfg process. I don't know enough about 3. It seems intuitively heavy but H2 is such a massive PITA to handle it might actually be quiet light weight. I'd try to avoid large quantities of H2 on general principles. Anything with an explosive range of (IIRC) 4-96% is just a bit too easy to burn.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 08:07 pm

Hydrogen compressors aren't cheap, require electricity, and are mechanical components that will break down sooner or later.  Then there is where hydrogen will be stored to consider.  If you want to store hydrogen I suggest considering these (https://www.hydrogencomponents.com/hydride.html).  Discharge is endothermic so they don't pair well with fuel cells but at one point Rouch Racing was developing a hydrogen fueled ICE for ULA's ACES.  The same engine should work for a generator.
Interesting people. Worth a closer look.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 08:12 pm
We often counter the 'spend the money to solve earths problems' argument by claiming the spinoffs make life better. Screw the velcro. Living on Mars demands efficiencies that are directly applicable to earth. We need to optimize systems, not the parts. And strengthen our argument in the process.
"Screw the velcro."

I might have to add that to my sig.   ;)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 08:21 pm
A wide variety of metals can be used.  One option that can be made on Mars using existing well-understood technology is nickel purified via the Mond process.  Nickel is also an acceptable Sabatier reactor catalyst.   
Mond is a way of making making pure nickel by decomposing Nickel carbonyl (also quite an attractive way to making 3d ojbects in various metals by decomposing over a hot former, provided you can deal with the toxicity of metal carbonyls, which generally seems high  :(  )

OTOH Raney Nickel is a way of making high surface area catalysts by mixing up a nicke/aluminum alloy and dissolving out the aluminum to create a sponge.

Which seems like a better fit to either application of Sabatier catalyst or hydride storage.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 08:28 pm
I expect nuclear on Mars will follow nuclear on Earth.  If it regains momentum on Earth it will be used on Mars; if not then there will be too small a market to develop it.  Nuclear in a sense is a solved problem on Mars.  If it works and can be made available then there are few energy limitations.  Solar is more fussy to run, so it requires more detailed analysis of the power options and the demand variations.
Short term space nuclear is Kilopower at 10Kw, with a cluster of them if you need greater power.

Transferring earths existing civilian nuclear technology to mars is a stunningly bad idea.  :(
Massive containment (10x the volume of water in a reactor) and enrichment just make them very poor choices for mars.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 08:34 pm

The potential market for nuclear reactors and solar panels on Earth is 15 to 20 000 GW.  At a minimum 9 000 GW of generation is required to replace fossil fuels.  The market on Mars may eventually be 1 GW, in quite a few years.
There is no demand for nuclear reactors on Mars.  I think the only realistic Mars settlement path goes through SpaceX and they seem to have decided to go for Solar.  I believe that to get a demand for nuclear on Mars one would need to prove that solar cannot do the job.  And that doesn't seem to be the case, as far as I know.  I think everyone agrees that nuclear fission would be simpler.  Nuclear fusion would be perfect.  But if solar can do the job, why not solar?
"Market" in the conventional sense, no.

But as part of a partnership with NASA to enable and test deployment of nuclear power to mars, and as a backup option, yes.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 08:44 pm
Edit - The question becomes, what is the best cell possible with the materials available on Mars, for use on Mars, not the most efficient possible on Earth. Since the atmosphere, temperature operating range, illumination and radiation environments are different any way the "best" solution is probably different too.
Exactly.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 09:04 pm
Sorry. In this context, the proliferation concern is the high-enriched uranium going into the reactor as the initial fuel load. There's not much plutonium produced in HEU-fueled reactors. Plutonium is a product of irradiating the >95% U238 in low-enriched uranium fuel. There's a proliferation vector regardless of whether we have a low-enriched uranium fuel cycle or a high-enriched uranium fuel cycle, but a consensus formed that the proliferation risk of fueling a civilization with essentially weapons-grade uranium is greater than the proliferation risk of extracting weapons-grade plutonium from the irradiated waste of LEU reactors.
True. You might add that most of those schemes have a hub-and-spoke concept of the power plants shipping their used fuel to central reprocessing plant, rather than stripping out the crud on site and refabricating the fuel for re-insertion to the reactor. The standard processing chain was also developed specifically to extract weapons grade Pu from used reactor fuel so is an exceptionally poor choice to build "proliferation resistance" into the system  :(

Quote from: butters
The bummer is that, proliferation risks aside, HEU is a vastly better reactor fuel. The reactor can run for 20-30 years, maybe more, on a single fuel load. The reactor vessel can be permanently sealed after fueling, never needing to be opened to remove and replace fuel rods, and buried underground at the end of its life, with very little fissile material remaining in the waste. Long-lived HEU cores typically have much lower power to mass ratios than short-lived LEU cores, so in terrestrial light water reactors, the decay heat after shutdown is low enough that exposure to ambient air is sufficient cooling to prevent melting even in the event of a complete loss of water in the primary loop. Naval light water reactors are extraordinarily safe and simple to operate, and that's because they run on HEU.
At the expense of needing the enrichment technology to begin with.  :(

BTW PWR's couldn't last as long as they do without refuelling unless they did in-situ breeding of fuel from the U238.
The challeng of making a low-enrichment long-lived core is how do you get rid of the poisons like Krypton and Samarium? One of the drivers behind the molten salt work at ORNL.

Quote from: butters
Kilopower is important because it's a rare opportunity to actually develop an HEU reactor for non-military applications. Because it's managed by NASA, the authorities trust that the sensitive material will be adequately secured throughout the supply chain. So NASA can have a reactor that runs for decades without refueling. NASA can use metallic fuel instead of ceramic oxide fuel, which means they can use liquid sodium coolant instead of water, which means the reactor vessel doesn't have to be 8 inches thick and the reaction can run on fast neutrons, eliminating the moderator.
As was EBR II. Again Kilopower (or rather the follow NASA programme) uses heat pipes and will be moving to HALEU.
Quote from: butters
None of this currently possible in the private sector in the United States. The innovation has to come from somewhere inside the government that is authorized to use non-standard nuclear fuel specifications. We do not trust some startup backed by Bill Gates to develop a type of reactor that requires a small amount of medium-enriched uranium as part of its initial fuel configuration. NASA could develop a traveling wave reactor. But not Bill Gates. It's not a problem that can be solved with money. It's a policy issue and a trust issue.
As I've looked at all the various ideas for reactors I've noticed there are recurring issues.

Fast spectrum reactors do a lot more damage to their structures than other types in terms of DPA (displacements per atom of structure)
Roughly
Gas cooled reactor 30-0
Pressurised Water  70+
Fast Breeder  200
Travelling wave 600+ (I think I've only seen one reference for this, but the others have come up in different contexts and sources).

As an independent martian option any enrichment for nuclear is a bad idea.  :( No earth government would allow the transfer of the technology.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/28/2023 09:07 pm
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
I don't think anyone is arguing any differently.

It's what happens when the sun don't shine that's the issue.

A non-storage based option would be nice.

And remember if you can make 1 Kilopower you can make n Kilopowers considerably more easily.
Title: Re: Power options for a Mars settlement
Post by: colbourne on 01/29/2023 01:46 am
Agreed about diversification. But you'd need dozens of Kilopowers for even one regular Starship mission per Synod. One Kilopower would be nice for base backup power. But the vast majority of the power will be produced via solar.
I don't think anyone is arguing any differently.

It's what happens when the sun don't shine that's the issue.

A non-storage based option would be nice.

And remember if you can make 1 Kilopower you can make n Kilopowers considerably more easily.
Very large flywheel energy storage would work well on Mars. Most of the mass of the flywheel could be sourced locally.
Title: Re: Power options for a Mars settlement
Post by: daveglo on 01/29/2023 02:41 am

Very large flywheel energy storage would work well on Mars. Most of the mass of the flywheel could be sourced locally.

Dude.  You can't source a practical flywheel energy storage system on Earth, much less Mars.  That's a pipe dream.

My opinion: Power options for a Mars colony are going to be:

1 - Nuclear.  Pros: Reliable (24/7)  Cons: Expensive, heavy  <--My personal favorite, I like reliable if my life depends on it.
2 - Solar.  Pros: Cheap, light, reliable in daylight  Cons: Darkness, dust
3 - Batteries. Pros: Almost cheap, reliable as a backup  Cons: Heavy, prone to nasty fires

You might get away with mitigating the overnight power demands for heating by using a geothermal heat pump.  Perhaps the Boring Company will have a berth on one of those early ships?
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 01/29/2023 03:19 am
That said I don't think any power plant on mars will be producing "waste" heat for a looooong time. The settlers will find a use for every BTU of output somehow.

[Small quibble] Efficiency of conversion of thermal energy to electrical energy depends on temperature difference. The hotter the hot-end and colder the cold-end, the greater the conversion efficiency. Putting any intermediate "warm" stage between the two ends reduces the efficiency of your power system. There's always a trade-off when "using" waste heat.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 01/29/2023 08:13 am
That said I don't think any power plant on mars will be producing "waste" heat for a looooong time. The settlers will find a use for every BTU of output somehow.

[Small quibble] Efficiency of conversion of thermal energy to electrical energy depends on temperature difference. The hotter the hot-end and colder the cold-end, the greater the conversion efficiency. Putting any intermediate "warm" stage between the two ends reduces the efficiency of your power system. There's always a trade-off when "using" waste heat.
The observation is correct, but the thing is that as you try to reject at lower and lower temperatures, the size of the heat exchangers increases.

If you can use the colony as the heat sink (e.g. taking hot showers or cooking soup or even keeping the habitats warm) then maybe some of that mass is free.

I think that's what JS may have been aiming for.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 08:58 am
Sure CO is toxic, but no more than a lot of other industrial feed stock chemicals that will be needed. Colorless and odorless is a bit of a problem but detectors are cheap and effective and I doubt anybody plans to pipe it to space heaters in the habitat  ::)

The question was raised about what to do with excess power when the air is clear for an array sized to provide life support in the worst case dust storm. Storing some of it as chemical energy in multi use feed stocks seems worth looking at. There are probably a number of basic carbon, nitrogen, oxygen etc compounds with potential. CO / O2 was just what came to mind first.
Ammonia also looks viable in this area. Relatively easy to liquify (certainly at mars temperatures) and combustible (but with some effort, and easy to detect if it leaks).  :)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 09:10 am
So, there were some papers a few years back (2018 I think) noting some geologically (areologically?) significant areas of melt apparently cause by natural nuclear reactions between thorium and probably natural uranium.

Apparently Mars is filthy rich in thorium.

A gas-moderated pebble bed nuclear reactor using local thorium would only require a bit of engineering and a minimum mass (maybe a few kg) of u-232 or other neutron source. In fact, the neutron source could be non-nuclear, such as a stripped ion beam. It doesn't have to be power self-sufficient. Just enough the start the thorium cycle. Once the cycle is started you can turn it off, since the cycle is self sustaining. Further, DoD is funding development of just such a reactor for field base use, so the tech is pretty well understood.

Why would that not be a good idea compared to using rocket fuel?

update: Apparently not such a new idea
https://www.popsci.com/technology/article/2010-08/thorium-reactors-could-wean-world-oil-just-five-years/
The then West Germany did indeed build a 300MW thorium pebble bed reactor. so something is possible, but IIRC there was significant enrichment of the thorium, and that is a technology that will be very difficult to get exported off earth.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 09:20 am
Do you have a reference for the Thorium values?  Because the data I have is not as positive.
Here is a map of Thorium average concentration as measured form orbit (isotopic radiation measurement)
The average value is lower than 1 ppm, with one northern area near to 1.
On Earth the average value of soil is 6 ppm of thorium and 8 ppm in the crust. https://en.wikipedia.org/wiki/Thorium#Occurrence

That is not conclusive, of course, but not very encouraging.
Thorium is a great idea, however thorium reactor are not an existing product.  Ideas are wonderful and fun, but actual products are useful and you can plan on them.
Indeed. It's showing mars is about 1/8-1/6 of the average level on earth. and to put the 1 ppm figures in perspective that'a 1g/metric tonne.

While not a product it thorium pebble bed reactors have been built. The former West Germany built one (https://en.wikipedia.org/wiki/THTR-300).

However to build one using martian materials implies setting up a mfg line and a mining operation before this comes on line.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 09:47 am
Oh boy, who is J.E Brandenberg?

Google scholar yields some seemingly normal articles, and then some very strange stuff.

This commentary found in my Google search makes me wonder just how serious/professional he is.  The articles seem logical at first glance, but strange tangents creep in...

https://core.ac.uk/download/pdf/42773562.pdf
This article is not by him.

It's a commentary on an article he wrote.

Are you talking about the commentary or the original article?

If the commentary then your remarks seem to apply to that author.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 09:50 am
The Sabatier reactor runs at ~350 C.  What type of heat storage will be able to ensure the reactor is up to temperature every morning?

How is it charged?

What does this system mass?
The classic way to do it would be to use some kind of phase-change material that melts around that temperature and put it in an insulated container. Concentrated "power tower" salt mixes usually do so at 700c, but I'm sure there's a salt mix that will run at 350c.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 09:54 am

None, i guess molten aluminum might do the trick.  Would have to be electrically.
Would have to mass way too much. 
Thermal storage ideas almost never work, do they?  It was just an idle notion, now thoroughly shot down :-)
Molten aluminium is around 635-650c.

Lead melts at 327c so some kind of lead/something-with-a-higher-melting-point  alloy would get you in the right range.

Ideally (again) you'd want ISRU rather than bringing it with you as it's going to be heavy.

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 10:03 am
One of the biggest problems with the reduction of available solar energy during dust storms is the dust storm.

Not only is the available energy reduced to ~2% as mentioned earlier, the ability to collect that reduced energy is hindered by dust settling on the solar collectors.

The solar array may be able to support minimal power requirements with a ~2% solar availability but if you then cover those panels with dust they will not be able to harvest even a fraction of the reduced available energy.
And let's just keep in mind what that 2% number actually means.

That means to keep running at full power during a dust storm takes an array 50x bigger than the baseline.

That's 50x the size and mass that would need to be brought from earth otherwise.

So 1 tonne baseline becomes 50 tonnes for safety. A 10 tonne baseline is 1/2 kilotonne for safety.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 10:10 am
Power lines is easily the better option.

I mean… there are high voltage power lines on Earth going literally thousands of kilometers (over 3000km), the same as the radius of Mars. That’s equivalent to roughly going from the equator of Mars to 60 degrees latitude.

That’s longer than just about any practical off-road rover, particularly if hauling batteries.

Power lines are more efficient and are automated.
Also this is OTS technology. Fully developed and ready to install.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 10:16 am

I vaguely remember reading about an unexpected high voltage arcing problem on Mars many moons ago.  My memory suggests the problem was with Curiosity's laser but numerous searches over the last few years have come up empty.  Perhaps Paschen's law in action was what I am recalling.

Then again perhaps not.  Either way I'm pretty sure avoiding arcing problems is an actual issue that will require insulation mass that we don't need to use for transmission lines here on Earth.  Thank you for raising science that supports why I chose to ask how much mass per km Martian power lines will require instead of extrapolating based on terrestrial power lines.
There's a book on High Voltage Engineering written (IIRC) by NASA WRT to issues of HV equipment in space.

The first thing to note is "High Voltage" can mean as little 300-500volts before you start seeing arcing effects.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 10:24 am
For the second, I think an asteroid is a bit over dramatic. I know enough about solar/battery on an industrial scale to have a good idea of how much I don't know, so any specific I might come up with can probably be shot down. One that does comes to mind is fines penetrating the control boxes and creating an unexpected progressive corrosion - in the middle of a bad dust storm.
Not unknown on earth.  The equivalent is where some building work has been done and plaster has got into the light switches. Cue the flickering lights of a "poltergeist"  :)
Quote from: OTV Booster
It's the things that aren't thought of that get you. Just look at the history of automotive recalls and WW2 torpedoes that didn't work in the Pacific because they were tested in the Atlantic. The list is long.
Indeed. The pervasive background of the test environment. How realistic is it? :(

A kilopower would be very nice to have for a last ditch survival effort but still a big unknown, for both dependability and availability. One big ICE generator, or better yet, several small ones, would be great. In the end no approach is without risk. It's a question of reducing the risk as much as possible.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 10:31 am

At about 1 tonne of food per year per person, 100 tonnes, or 1 Starship of ration packs, could feed 50 for 2 years.  Might make sense to include one of these in the first few Starships to Mars.  Simpler than a robust self sustaining ecosystem.
Data point. NASA ECLSS studies baseline 5Kg of water/food/air for an astronaut.

So  years worth is 1825Kg or 1.825tonnes.
Quote from: lamontagne
One of the interesting points of solar might be that is should be a very robust and distributed architecture, while a large central nuclear plant would be in a way less robust.  Perhaps a multitude of small reactor would also provide redundancy.
The baseline Kilopower unit is 10Kw, because there's lots of uses that NASA can find at that scale. Design can stretch up to (IIRC) 1MW.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 10:55 am
Solar panels can be installed at or near each colony or outpost.  No real need for long distance transmission of power on Mars as other than dust storms there are no cloudy days to keep from producing power.
Except the "cloudy days" can last for months and cover the entire planet as this thread has been discussing  :(



Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 11:00 am

Interestingly, on July 8 2018 the Mars Reconnaissance Orbiter captured several images of Olympus Mons's surface, unobscured by dust. Moreover, the article describing the images mentions the height of the volcano as the reason why the surface is visible. [1] Meanwhile, the modeled data suggests that Olympus Mons is covered with dust to an optical depth of 3 tau.


[1]: https://www.uahirise.org/ESP_056010_1985 (https://www.uahirise.org/ESP_056010_1985)
Thank you for this information. So it looks like LMT's animation was model derived.

A lot of stuff has to be done based on models.

And those models have to be taken seriously. If they are wrong they need to be challenged, because only by being challenged can models be improved.

But what is the conclusion? 

As a precaution agains worst case dust storms would be simpler just to land somewhere up the top of the volcano?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 11:12 am
Yes, I love Lithium Iron Phosphate and kin for the high C rate alone. Batteries you can probably weld with and not catch fire/explode.

For static backup applications though, weight and energy density are not as important as they are for mobile and vehicular use so I expect other traits such as cost, simplicity and scalability to predominate. If they want to be able to run the whole Mars complex on stored power for days or weeks in a pinch, that's a lot of storage.
Indeed.

For static power mass and volume are not that important except if you're bringing them to mars from earth.

OTOH if you can mfg them from mars marterials you could (if you want to be up and running ASAP) bring the containers with you. Those would be big, but quite light.

When you start doing the math for settlement support during realistic storm durations power needs get quite big quite fast.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 11:43 am
I think one potentially promising yet overlooked power and grid energy storage option for Mars settlements would be the solar thermal potion.
I think you mean "option," although I think we'd all like a "solar thermal potion"  :)

I like the concept very much for all the reasons you mention.  I didn't know that light-weight options existed for the tower as well as the reflectors. The question "how long can you provide power?" becomes "how big a tank of salt do you want to build?" and how to keep it out of contact with the ground (although making it a two layer tank with a really low pressure between (not 720Pa, 1Pa) would take care of all everything not the bottom

What I most like about it is the relativley simple infrastructure you need to build more of them.

The argument has always been that it doesn't handle light scattering by airborne dust well, and of course it shuts down entirely during a sand storm.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 12:18 pm
JohnSmithxxx (I forget the number attached to his handle) brought up the idea of salt storage a long time ago in this thread. He said something about salt in beer cans of all things, buried in a pit, and claimed it had been done. I consider him a high quality info source.
Thank you. I try to be accurate.

It was run by the US Navy Naval Research Laboratory in the late 70's/early 80's and was called "SolChem." It planned to use a cyclic chemical reaction (several were being looked at, ammonia was one of them) to move heat without needing insulated pipes.

The ultimate goal was to make the US Navy independent of oil supplies for its non-nuclear fleet by mfg synthetic fuel with systems mfg from materials available on CONUS. So the salt was a mix of Sodium and potassium chloride (IE Rocksalt) rather than some more exotic mix.

But salt dissolves easily with even a little water around so they planned to put it in beverage cans. OTS technology able to support very large volumes. To keep moisture out and ensure thermal transfer remained good after the salt had reached its melting temp (not something that would happen if it melted into a big pool then was frozen back again.  :(  I can't recall if they were actually going with Aluminum or steel. the operating temp was about 500c, so Aluminum is possible but AIUI steel was still in common use for beverage cans at the time.

Quote from: OTV Booster
I question aluminum beer cans but following the idea, steam from the tower flows into the salt bunker, then to the turbines. After dark, the tower is cut out of the loop to avoid unnecessary cooling of the working fluid. This avoids the problems associated with molten salt. It might cut energy density but that sounds like a good trade for an early infrastructure.
However using steam in the tower as you propose complicates things. Nitrate salts melt around 700c and (IIRC) Solchem was targetting about 500c. If you match the operating temp of modern Super and Ultra-Supercritical steam turbines you can buy them OTS, like the 8000+ used in fossil fuel power plants around the globe, not the 390 of water moderated reactors.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 12:27 pm
Just realized I forgot my source: https://an.rsl.wustl.edu/merb/merxBrowser/an3.aspx?it=D1&ii=22771

Quote
Opportunity is currently in the midst of a severe dust storm though all subsystems are still operating as expected in RAM mode as of the Sol 5111 UHF pass. Solar array energy is approximately 22 W-hrs, with a measured tau of 10.8. This Tau measurement is the highest ever recorded from a ground station on the planet Mars. Dust factor was previously estimated at 3.27 as of Sol 5108.
22 W-hrs?

that's not a solar cell output that's a measure of energy in a battery.  :(

The output of a PV array should be in watts only.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 12:33 pm
What you are saying is just wrong, but you constantly repeat it. The figure of Watt-hours is integrated received power that day, NOT battery state of charge. Quit accusing others of ignoring something which is really just you misinterpreting something clear as day.
OK that makes a bit more sense.

The units are still quite odd.

So the average that day should be that figure divided by 24? that would give 0.9167w as the average PV array output.

Which doesn't seem like much.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 01:19 pm
I disagree that the reactor does not exist as yet, seems to me that modest size submarine reactors are pretty routine.
Weight is the main issue, mostly due to passive shielding that can be eliminated just by siting the reactor remotely.

Solar takes acres of cells to get reasonable power, so mandates a construction project right after getting there. Imho, that is a serious negative.
They're not that small as their typical size in 60MW, about the size of the few merchant ship reactors that have been built outside the former Soviet Union (the one for the NSS Savanah and one built in Germany IIRC)

And of course any naval reactors come under national security regulations.

So you've got a) A couple of reactors built 70 odd years ago or b)Modern one whose technology is a state secret.

Neither is exactly accessible  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 01:27 pm

The observation is correct, but the thing is that as you try to reject at lower and lower temperatures, the size of the heat exchangers increases.

If you can use the colony as the heat sink (e.g. taking hot showers or cooking soup or even keeping the habitats warm) then maybe some of that mass is free.

I think that's what JS may have been aiming for.
Exactly.

Mars is damm cold  :(  The power engineers "Low grade waste heat" is the ECLSS engineers fish tank and greenhouse temperature management supply.  :)

In chemical engineering it's sometimes called "Scavenging," but people feel that's a bit pejorative.
Let's call it "re-purposing" heat.  ;)
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 01/29/2023 02:10 pm
The argument against wind power is that the surface winds are too low and would need either a very tall tower or a balloon. Hmmm.

A new form of cogeneration? Mars is so power poor ya gotta take what you can get. Actually this emphasizes an important point. There is probably no one solution.


Diversification can only be a good thing until real people (not us armchair guys) get their hands dirty over time. Then they'll have ground truth knowledge of what works best under different circumstances. Theory is great but experience is better.


An minor nit Ive thrown out on occasion. Needs for expedition 1-3 are entirely different than later. 1-3 are strictly about survival and initial build out. The next several (or many) synods are about more than survival but not yet about thriving. That's when the technology shakeout will happen. Once they know what works and what doesn't, the stage will be set for Mars to thrive. This applies to everything, not just power.


A lot of the disagreement here is because of us thinking about but not acknowledging different phases of future history. Is there any way to fix this?
Good points. Yes Mars is very power poor. No coal or oil (and very little free oxygen to burn them with if they existed  :(  ). I'm not sure how well people actually appreciate this fact.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 01/29/2023 07:23 pm
The argument against wind power is that the surface winds are too low and would need either a very tall tower or a balloon. Hmmm.

A new form of cogeneration? Mars is so power poor ya gotta take what you can get. Actually this emphasizes an important point. There is probably no one solution.


Diversification can only be a good thing until real people (not us armchair guys) get their hands dirty over time. Then they'll have ground truth knowledge of what works best under different circumstances. Theory is great but experience is better.


An minor nit Ive thrown out on occasion. Needs for expedition 1-3 are entirely different than later. 1-3 are strictly about survival and initial build out. The next several (or many) synods are about more than survival but not yet about thriving. That's when the technology shakeout will happen. Once they know what works and what doesn't, the stage will be set for Mars to thrive. This applies to everything, not just power.


A lot of the disagreement here is because of us thinking about but not acknowledging different phases of future history. Is there any way to fix this?
Good points. Yes Mars is very power poor. No coal or oil (and very little free oxygen to burn them with if they existed  :(  ). I'm not sure how well people actually appreciate this fact.
Yup everything will be about power.  You can make all the plastics and glass and metal that you want from local resources, but every little thing costs power and there's no serious source other than nuclear and solar.

I am always wondering what the magic number is, in kWatt-hr/yr, per person, including everything from air to food to transportation to construction.

I've tried to ballpark it before based on terrestrial numbers, but it's not straight forward. I wonder if SpaceX has a firm estimate.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/29/2023 11:07 pm
The argument against wind power is that the surface winds are too low and would need either a very tall tower or a balloon. Hmmm.

A new form of cogeneration? Mars is so power poor ya gotta take what you can get. Actually this emphasizes an important point. There is probably no one solution.


Diversification can only be a good thing until real people (not us armchair guys) get their hands dirty over time. Then they'll have ground truth knowledge of what works best under different circumstances. Theory is great but experience is better.


An minor nit Ive thrown out on occasion. Needs for expedition 1-3 are entirely different than later. 1-3 are strictly about survival and initial build out. The next several (or many) synods are about more than survival but not yet about thriving. That's when the technology shakeout will happen. Once they know what works and what doesn't, the stage will be set for Mars to thrive. This applies to everything, not just power.


A lot of the disagreement here is because of us thinking about but not acknowledging different phases of future history. Is there any way to fix this?
Good points. Yes Mars is very power poor. No coal or oil (and very little free oxygen to burn them with if they existed  :(  ). I'm not sure how well people actually appreciate this fact.
Yup everything will be about power.  You can make all the plastics and glass and metal that you want from local resources, but every little thing costs power and there's no serious source other than nuclear and solar.

I am always wondering what the magic number is, in kWatt-hr/yr, per person, including everything from air to food to transportation to construction.

I've tried to ballpark it before based on terrestrial numbers, but it's not straight forward. I wonder if SpaceX has a firm estimate.
For our Mars settlement we calculated 1600 GJ/Y/person.  Food takes up a lot of that.  If there is absolutely no natural solar used, then it's even more.  Most serious designs I've seen are in that ballpark.

I have  spreadsheet, but it's mostly in French....
Title: Re: Power options for a Mars settlement
Post by: Greg Hullender on 01/30/2023 05:18 pm
Quote from: lamontagne link=topic=39785.msg2453446#msg2453446
For our Mars settlement we calculated 1600 GJ/Y/person.  Food takes up a lot of that.  If there is absolutely no natural solar used, then it's even more.  Most serious designs I've seen are in that ballpark.

I have  spreadsheet, but it's mostly in French....
That's about  50 kW/person. Quite a bit more than the 9 kW/person (284 GJ/y/person) the average American uses (https://www.npr.org/2022/04/12/1092045712/how-much-energy-powers-a-good-life-less-than-youre-using-says-a-new-report#:~:text=Americans%20use%20284%20gigajoules%20a,according%20to%20the%20new%20research.). But the average American doesn't have to manufacture his own air. :-)

That suggests the first settlement is really going to need that megawatt reactor though.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/30/2023 06:10 pm
Quote from: lamontagne link=topic=39785.msg2453446#msg2453446
For our Mars settlement we calculated 1600 GJ/Y/person.  Food takes up a lot of that.  If there is absolutely no natural solar used, then it's even more.  Most serious designs I've seen are in that ballpark.

I have  spreadsheet, but it's mostly in French....
That's about  50 kW/person. Quite a bit more than the 9 kW/person (284 GJ/y/person) the average American uses (https://www.npr.org/2022/04/12/1092045712/how-much-energy-powers-a-good-life-less-than-youre-using-says-a-new-report#:~:text=Americans%20use%20284%20gigajoules%20a,according%20to%20the%20new%20research.). But the average American doesn't have to manufacture his own air. :-)

That suggests the first settlement is really going to need that megawatt reactor though.
The study forgets that Americans eat food.  America has 157 000 000 Ha of arable land, to feed 350 000 000 people, or 2 people per hectare.  Or in other words 5000 m2 of land is required to feed one person.  This land receives about 250 W/m2 on average, including angle effects, nighttime and clouds.  That's 5000 x 250 = 1 250 kW of power per person.  That power is necessary to feed the US population. So the real average power use is 1259 kW, not 9 kW.
Now most of that sunlight is wasted in reflection, evaporation and general weather losses. Much of the food produced is wasted, or eaten by competition. Winter losses and growth cycles losses also affect the production rates.
Greenhouses can be about 30 times more efficient that arable land in food production terms, at 60 tonnes per hectare.  So 1250kW / 30 is about 41 kW.  add that to your 9 kW and you get 50 kW.

On Mars there is no land, all food needs to be produced in greenhouses, and the light levels are 50% of those on Earth.  So the 50 kW per colonist is an optimist number, with the expectation that up to 50% of the food can be produced in natural sunlight greenhouses.  If all food must come from artificial grow rooms and vertical farms, the power usage will be even higher.


Title: Re: Power options for a Mars settlement
Post by: daveglo on 01/30/2023 08:40 pm

The study forgets that Americans eat food.  America has 157 000 000 Ha of arable land, to feed 350 000 000 people, or 2 people per hectare.  Or in other words 5000 m2 of land is required to feed one person.  {snip}


Your math is WAY off. 

Firstly, land in farm production in the US is 895,300,000 acres (362,310,000 Ha), not the value you quoted.

Second, the US feeds far more than it's own population.  Bulk exports of raw products exceed imports by a ratio of almost 40:1.

The reality is that the number you're looking for depends in large part on what you can get away with.  A more general estimate using quality soils would be 1 acre (0.4 Ha) per person.  But of course, the soils on Mars are going to be much more of a challenge, just because of the volume of fertilizer needed to make it suitable for food production.

I would agree that power requirements are going to be a top issue.  The big question is how much power to do you need to get water, oxygen, methane, and nitrogen out of the martian environment?  THAT's the number you're really looking for.
Title: Re: Power options for a Mars settlement
Post by: Ionmars on 01/30/2023 09:00 pm

The study forgets that Americans eat food.  America has 157 000 000 Ha of arable land, to feed 350 000 000 people, or 2 people per hectare.  Or in other words 5000 m2 of land is required to feed one person.  {snip}


Your math is WAY off. 

Firstly, land in farm production in the US is 895,300,000 acres (362,310,000 Ha), not the value you quoted.

Second, the US feeds far more than it's own population.  Bulk exports of raw products exceed imports by a ratio of almost 40:1.

The reality is that the number you're looking for depends in large part on what you can get away with.  A more general estimate using quality soils would be 1 acre (0.4 Ha) per person.  But of course, the soils on Mars are going to be much more of a challenge, just because of the volume of fertilizer needed to make it suitable for food production.

I would agree that power requirements are going to be a top issue.  The big question is how much power to do you need to get water, oxygen, methane, and nitrogen out of the martian environment?  THAT's the number you're really looking for.
The production numbers you cite are new to me, especially the 40:1 ratio. Do you have a reference?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/30/2023 09:10 pm

The study forgets that Americans eat food.  America has 157 000 000 Ha of arable land, to feed 350 000 000 people, or 2 people per hectare.  Or in other words 5000 m2 of land is required to feed one person.  {snip}


Your math is WAY off. 

Firstly, land in farm production in the US is 895,300,000 acres (362,310,000 Ha), not the value you quoted.

Second, the US feeds far more than it's own population.  Bulk exports of raw products exceed imports by a ratio of almost 40:1.

The reality is that the number you're looking for depends in large part on what you can get away with.  A more general estimate using quality soils would be 1 acre (0.4 Ha) per person.  But of course, the soils on Mars are going to be much more of a challenge, just because of the volume of fertilizer needed to make it suitable for food production.

I would agree that power requirements are going to be a top issue.  The big question is how much power to do you need to get water, oxygen, methane, and nitrogen out of the martian environment?  THAT's the number you're really looking for.


Arable land, not farming land.  I don't think we will be grazing many cows out to pasture on Mars.
https://worldpopulationreview.com/country-rankings/arable-land-by-country

Err.... 0.4 Ha is awfully close to 0,5 ha.  5000 m2.  Wouldn't call that way off.  It's basically the same number.

Sorry, but no.  These are all fairly easy to extract.  the most difficult issue is getting plants to function.  Photosynthesis is extremely inefficient (but also almost magical!) and evapotranspiration takes ridiculous amounts of energy.

The entire planetary ecosystem has evolved over billions of years to operate with huge amounts of water and a power level based on 1200+ W/m2 peak.  You won't be able to do the same thing with 600 W/m2.

Regarding import export, it's awfully close to a null game, as far as I can see.

'Agricultural exports support more than one million American jobs, with roughly 70 percent of these jobs in the non-farm sector, such as in processing and agricultural manufacturing. Overall, U.S. farmers and ranchers export more than 20 percent of what they produce.'
vs
'American consumers seek a safe, diverse, and abundant food supply that is simultaneously affordable and available throughout the year. To help meet these consumer demands, the United States imports about 15 percent of its overall food supply.27 sept. 2022'

https://www.foodsafetynews.com/2022/02/rising-food-imports-into-u-s-call-for-a-global-prospective/

I can provide the entire breakdown of the energy use if you want, will just take a few hours to translate :-)

The (practically) only good thing about Mars is that it's so cold that you can cool grow rooms without needing compression and refrigeration, as we do on Earth. 
Title: Re: Power options for a Mars settlement
Post by: daveglo on 01/31/2023 12:37 am
Well, I'll rely on a US source for data about the US:

https://www.nass.usda.gov/Publications/Todays_Reports/reports/fnlo0222.pdf

Page 4.

And I think you're missing the point.  You could feed a dozen people on an acre, or no one.  It's how WELL can you use it.  And that land-use efficiency coefficient is going to vary widely, and is strongly dependent upon light/heat energy input (whether natural or artificial) and fertilization (carbon, hydrogen, nitrogen, oxygen).

You want a good read on a system that lends itself to colonization-style agriculture, try searching for shipping container farming.  It's a hot topic.

https://www.freightwaves.com/news/want-your-own-farm-this-one-comes-in-a-shipping-container
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 01/31/2023 12:47 am
What you are saying is just wrong, but you constantly repeat it. The figure of Watt-hours is integrated received power that day, NOT battery state of charge. Quit accusing others of ignoring something which is really just you misinterpreting something clear as day.
OK that makes a bit more sense.

The units are still quite odd.

So the average that day should be that figure divided by 24? that would give 0.9167w as the average PV array output.

Which doesn't seem like much.

Technically divided by 24.66 hours. ;)

And yes, it's not much. That power output was measured during a very dark dust storm.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 01/31/2023 12:51 am
Now most of that sunlight is wasted in reflection, evaporation

That's not waste, it's water purification. :)

This is true on Earth too. If plants didn't "wastefully" evaporate (really, transpire) water, then we'd lose the source of 80% of rainfall on the land surface. (https://www.nature.com/articles/nature11983)

On a Martian greenhouse, you can recover both the water and the latent heat of evaporation with dehumidifiers. You can pipe the water to a final filtration step, and recuperate the low-grade heat for some purpose (eg space heating).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 01/31/2023 03:07 am
Quote from: lamontagne link=topic=39785.msg2453446#msg2453446
For our Mars settlement we calculated 1600 GJ/Y/person.  Food takes up a lot of that.  If there is absolutely no natural solar used, then it's even more.  Most serious designs I've seen are in that ballpark.

I have  spreadsheet, but it's mostly in French....
That's about  50 kW/person. Quite a bit more than the 9 kW/person (284 GJ/y/person) &lt;a href="https://www.npr.org/2022/04/12/1092045712/how-much-energy-powers-a-good-life-less-than-youre-using-says-a-new-report#:~:text=Americans%20use%20284%20gigajoules%20a,according%20to%20the%20new%20research."&gt;the average American uses&lt;/a&gt;. But the average American doesn't have to manufacture his own air. :-)

That suggests the first settlement is really going to need that megawatt reactor though.
50 kWatt-avg sounds right.  I got numbers from 10 and up, but there are so many variables.

How much is spent recycling CO2/O2?  Food growing? How much is expended on building stuff, like running tractors or tunneling machines...  Creating ISRU materials like plastics, glass, metal? Transportation?  Propellant? 

It's quite the list.

I think proceeding with 50 is a good starting point.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/31/2023 12:47 pm
Probably a good time to repost this:

https://marspedia.org/Embodied_energy

The energy required to produce various goods.  This does not include labor, that could also be represented on Mars by energy usage to maintain the habitat and produce food for humans for a more complete picture.

Future improvements in automation will reduce the labor costs, however.

For the questions about nitrogen and such, see the first few lines of the table.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 01/31/2023 02:26 pm
Going to rework the hydroponics energy figures and refine them a bit.
There are a lot of references to lettuce with the vertical farm growers, which have a fine yields as far as mass goes, but that include very little energy, as they are mostly water.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/01/2023 06:24 am
Anyway, getting back on-topic, Tau Theory's demise is great for would-be Mars colonists. It means that even in the deepest dust storm we don't need supplemental wind / nuclear / whatever. If we have a solar array sized for propellant production, it's plenty oversized for providing life support during a dust storm.

"Good news, everyone!" :D
Provided you ship 50x (not 50%, 50x) the size of array you need under normal circumstances. And ideally that needs to be shipped early because without it any crew will probably die.  :(

Which suggests there is a case for at least considering a secondary system provided it doesn't need too much development work.

That would include wind (a tall  tower with a windmill on top. That sounds like it could be engineered fairly easily) or geothermal (there are houses in the US that are at least partly heated by bore-hole heat exchangers) and it's pretty clear that at least one set of equipment to bore holes through rock is going to be needed anyway.

I'm no fan of mars-specific nuclear projects. If the USG supplied Kilopower units as GSE that would be viable but an actual "SX Reactor (TM)"  is ridiculous given the very steep learning curve in acquiring nuclear technology from scratch. Running on naural uranium to begin with would be a smart move (as most 1st generation designs were) to avoid the endless ITAR issues with enriched uranium, and the whole business of enrichment anyway.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/01/2023 06:31 am
I think this is again a case of not properly identifying when in the development of a settlement we are for the discussion.

I actually said that a power line to the north was possible, just that it might have high losses at lower voltages. At least medium power HVDC is an existing system developed by real companies.  Is there such a thing as UHVDC for a few MW?   It there is so much the better, I have no special love for methalox generators.

There is a cost benefit analysis that is required for every project.  There are at least 20 villages in Quebec and many mining operations that are powered by diesel generators because it is not cost effective to build power lines.  Hydro Quebec, as a state monopoly has the legal obligation to supply electrical power to everyone.  It doesn't have the obligation to use power lines for this. The villages are supplied by ships and have large diesel tanks that stock the fuel for up to a year.  There are no roads to these villages.   
The northern mining site on Mars needs to be more completely described.  If there are trucks or trains of ice coming down, they don't have to go up empty.  They might go up loaded with fuel.

If we need storage to survive dust storms and winter, it can be logical to move the storage medium about, rather than the power itself.  This might be cost effective for a long time during the Mars settlement development.
Excellent points.

The known SoA for this systems  is at a certain point on the demand curve. It works well at that point but as you note does anyone do this at the (relatively) low MW level Mars early settlement would need? IDK either.  :(

What works early on might indeed not be appropriate later in the growth cycle of the settlement, but "early on" could be a looong time. Decades, if not centuries in fact.

Interesting running cables isnt' cost effective. That suggests an environment very hostile to pylons or very difficult to cut a tunnel (or at least a trench, I can't believe there's much paving to dig up  :) ) into.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/01/2023 06:40 am
One thing that didn't come :( up yet was that they observed a substantial increase in dust loading right before Opportunity died. Real Mars solar arrays (which are big) will likely use electrostatic sweeping (https://www.sciencedirect.com/science/article/abs/pii/S0094576511001883) to actively remove dust buildup. Cheaper and vastly fewer moving parts than using robots or EVA-suited astronauts.
Excellent find.

This is one of those things I'd thought was important (at scale) but people were treating as simply as a nuisance.

I'm very glad to see that this has been actively worked on an solutions exist not just for arrays but also clothing and vehicles. This is going to be a real enabler for surface operations. In fact it sounds like it already has been.

When you're running 100s (1000s?) of m^2 of array a tank of compressed air isn't going to cut it.  :(

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/01/2023 06:51 am

So a basic genset providing 40 kW of power, and 60 kW of heat, is a very simple machine.  Of course the Cat unit shown here would need to be extensively modified to burn methalox, but it seems like a very doable project.
And as ULA's work with Intergrated Vehicle Fluids has shown "waste" heat is far from wasted.

But the extensions will be tricky. You could go with liquid methane, so the system's pumping a liquid as it expects, but then you've got all the issues with stuff operating very cold below they are expecting. Or run as a room temperature gas, which is a very different fuel to process.

Actually running with pure GO2 might be the more difficult issue. IIRC submarine disiel engines fed back some of the exhaust to the inlet. This would make sense if they had O2 tanks but I'd presume when  they rechared the tanks on the surface they'd be using compressed air, not separating out just the O2, so I'm not sure why they'd do it.  My memory may be playing tricks.   :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/01/2023 06:56 am
Round trip energy efficiency generally means waste heat somewhere, which on Mars may not be "wasted", depending on equipment placement.
Correct on both counts.

Mars is cold at night.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/01/2023 07:40 pm

.... On Mars the dust electrostatically clings to the panel, so you probably either A) need to wait for a convenient dust devil, or B) need to fight fire electrostatic with electrostatic...."

Do we have a practical way to generate a static electric charge (+/-) across the surface of a solar panel?
Wasn't that the theme of the paper cited a few posts back?
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/01/2023 07:44 pm
At a settlement, self-sufficient agriculture without long-term energy storage correlates with lengthy fallow seasons,

I don't see why that's necessarily a bad thing; you would want a couple years' worth of food storage anyway.

Quote
and greenhouse scale potentially 10x hab scale.

Only if one assumes greenhouses are the primary calorie source; that's not required and maybe not even likely. There are probably more efficient means using microbes in bioreactors as the primary calorie source, ultimately processed into foods, with greenhouses for fresh fruits, vegetables, etc. (things eaten "as fresh") but not staples like wheat/corn/rice.
Well "Quorn" is a micoprotein derived from a fungi so that's certainly an option with TRL9.

But it'll need quite a bit of "post processing" to turn into something people would want to eat.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/02/2023 06:36 pm

Naturally there's an upper limit. If the energy multiplier is very high (eg microchips), then the product will be imported from Earth instead.That's energy import, not energy storage.


The sooner we fully internalize that demand shifting + stockpiling is energy storage (and should be traded & compared on a level playing field), the better off our designs will be.


Edit: thanks for coming to my TED talk. :)
These are excellent points.

Not forgetting that stuff made in the settlement does not have to be bought by the settlement and shipped from earth anything up to 26 months in the future.  :(
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/03/2023 01:31 am

Yes, but the system as a whole must be oriented toward production and long-term storage of methane and oxygen for use as propellant, so it will already be optimized for that. My guess is that using this resource as needed for second-level electrical backup will be cheaper than adding a system that must store a large amount of hydrogen. At scale, hydrogen storage is a lot harder than methane storage. Spend the capital on expanding your solar, battery, and methane/oxygen storage. That gives you more methane/oxygen production in the first place and less need to use it to produce electricity (fewer hours/year of empty battery) I don't know what the electrcity==>gasses==>electricity  round-trip efficiency will be, but it will be good enough.
True.

This comes up in proposals for hydrogen powered cars.  Basically there are 3 ways to do it.
1)Pressurise GH2. This typically targets 5000Psi. 2)Cool it to boiling point (-397F i think) 3)Absorb onto metal alloys.

1 & 2 use about 3x as much energy to make the conversion as in the orginal mfg process. I don't know enough about 3. It seems intuitively heavy but H2 is such a massive PITA to handle it might actually be quiet light weight. I'd try to avoid large quantities of H2 on general principles. Anything with an explosive range of (IIRC) 4-96% is just a bit too easy to burn.  :(
I love this discussion. Just noticed it went active again.


There is a fourth Hydrogen storage technique in current use. Take two molecules of hydrogen and bind them to one Carbon. It takes a ding on theoretical efficiency but by the time all the real world handling problems are factored in, it works out pretty well.  ::)


Seriously, methane production and handling will be a given, and hydrogen is just too finicky. If self sufficiency is a goal it is more efficient to fabricate hardware for one technology for use wherever it will suffice. Waaay down the road, once survival is assured, they'll be able to diversify to tweak optimizations.
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 02/03/2023 03:21 am
Quote from: lamontagne link=topic=39785.msg2453446#msg2453446
For our Mars settlement we calculated 1600 GJ/Y/person.  Food takes up a lot of that.  If there is absolutely no natural solar used, then it's even more.  Most serious designs I've seen are in that ballpark.

I have  spreadsheet, but it's mostly in French....
That's about  50 kW/person. Quite a bit more than the 9 kW/person (284 GJ/y/person) &lt;a href="https://www.npr.org/2022/04/12/1092045712/how-much-energy-powers-a-good-life-less-than-youre-using-says-a-new-report#:~:text=Americans%20use%20284%20gigajoules%20a,according%20to%20the%20new%20research."&gt;the average American uses&lt;/a&gt;. But the average American doesn't have to manufacture his own air. :-)

That suggests the first settlement is really going to need that megawatt reactor though.
50 kWatt-avg sounds right.  I got numbers from 10 and up, but there are so many variables.

How much is spent recycling CO2/O2?  Food growing? How much is expended on building stuff, like running tractors or tunneling machines...  Creating ISRU materials like plastics, glass, metal? Transportation?  Propellant? 

It's quite the list.

I think proceeding with 50 is a good starting point.

The following paper "Electrical Requirements for a Spectrum of Multi Stage Space Farms" from 2018

https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf (https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf)

suggests 11KW is the minimum for quorn type bioreactor food, with most of that pump power, scaling up to 672KW for higher end food.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/04/2023 04:01 am
The following paper "Electrical Requirements for a Spectrum of Multi Stage Space Farms" from 2018

https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf (https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf)

suggests 11KW is the minimum for quorn type bioreactor food, with most of that pump power, scaling up to 672KW for higher end food.

I note that this is true for all scenarios (Table 42).

Perhaps hydroponics is not as "efficient" as is commonly thought.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/04/2023 04:45 am
The following paper "Electrical Requirements for a Spectrum of Multi Stage Space Farms" from 2018

https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf (https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf)

suggests 11KW is the minimum for quorn type bioreactor food, with most of that pump power, scaling up to 672KW for higher end food.

I note that this is true for all scenarios (Table 42).

Perhaps hydroponics is not as "efficient" as is commonly thought.
I'm really doubtful about those pumps.  from table 44, 67000 kW of pumping?  Energy in W and kW? 
Pumping power 60 times higher than lighting power?  ''Little giant'' pumps (table 3) are incredibly crappy pumps used for pumping condensate in air conditioning units, they probably have ridiculously low efficiencies.
What are they using high pressure pumps for anyway?  You don't use a diphragm pump at large scale for oxygenation, you use blowers...

Anyway, 40 000 000 kg per day is one swimming pool per day or recirculation.  You should be able to do that with a one hp pump.
Oups!  1000 swimming pools per day. That's a lot of water, but most of it is used to recirculate for fish, so there should not be much pressure loss there.  The power usage number seems low now.

Table 37: 54 000 000 'W' seems to be 54 000 000 joules per day / 3600/24 = 625 W or about one hp, or 0,62 kW

In table 42, this daily usage of energy becomes an instant power, completely wrecking the calculation.  Using 0,62 kW rather than 54 000 kW makes the pumping an negligeable item.

The lighting for 3 hectares should easily be 250W = 10 000 m2 x 3 or 7 500 kW or 7,5 MW.  They seem to have 10 MW so that works.

I think they screwed up significantly.  I'll stick with Hal Globus' numbers in table 43: 35 to 60 kW per person.

Title: Re: Power options for a Mars settlement
Post by: Paul451 on 02/04/2023 06:34 am
A reminder that there's a thread for discussing Agriculture on Mars (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2454932#msg2454932).

Aside: Asteroza, I cross posted your comment over there.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/06/2023 03:28 pm
Since we will probably need a lot of supplemental lighting for food production on Mars, should we expect a wider daily power swing/peak load on Mars than on the Earth?

Typical ranges in the US seems to about 2.  https://www.eia.gov/todayinenergy/detail.php?id=42915

Since the power required for plant growth will be, perhaps, 5 times the power required for other needs, the daily swing might be up to ten times the minimal demand?  This would impact solar field design.

On the other hand, for a nuclear based power system, staggering the production rates of grow rooms might mean the power swing could be mitigated and the load be more constant, reducing the need to overbuild the nuclear power supply?
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/06/2023 07:47 pm
Since we will probably need a lot of supplemental lighting for food production on Mars, should we expect a wider daily power swing/peak load on Mars than on the Earth?

Typical ranges in the US seems to about 2.  https://www.eia.gov/todayinenergy/detail.php?id=42915 (https://www.eia.gov/todayinenergy/detail.php?id=42915)

Since the power required for plant growth will be, perhaps, 5 times the power required for other needs, the daily swing might be up to ten times the minimal demand?  This would impact solar field design.

On the other hand, for a nuclear based power system, staggering the production rates of grow rooms might mean the power swing could be mitigated and the load be more constant, reducing the need to overbuild the nuclear power supply?
If greenhouses are done away with so does natural insolation, but then if growing is done underground, there is no need for complicated glass insulation schemes. Plants don't really care what time it is, they just want the photons. Sounds like a natural for load balancing.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/07/2023 07:36 am
The following paper "Electrical Requirements for a Spectrum of Multi Stage Space Farms" from 2018

https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf (https://space.nss.org/wp-content/uploads/NSS-JOURNAL-Space-Farm-Electrical-Requirements.pdf)

suggests 11KW is the minimum for quorn type bioreactor food, with most of that pump power, scaling up to 672KW for higher end food.

I note that this is true for all scenarios (Table 42).

Perhaps hydroponics is not as "efficient" as is commonly thought.
I'm really doubtful about those pumps.  from table 44, 67000 kW of pumping?  Energy in W and kW? 
Pumping power 60 times higher than lighting power?  ''Little giant'' pumps (table 3) are incredibly crappy pumps used for pumping condensate in air conditioning units, they probably have ridiculously low efficiencies.
What are they using high pressure pumps for anyway?  You don't use a diphragm pump at large scale for oxygenation, you use blowers...

Anyway, 40 000 000 kg per day is one swimming pool per day or recirculation.  You should be able to do that with a one hp pump.
Oups!  1000 swimming pools per day. That's a lot of water, but most of it is used to recirculate for fish, so there should not be much pressure loss there.  The power usage number seems low now.

Table 37: 54 000 000 'W' seems to be 54 000 000 joules per day

I don't think that's it (based on my cross-check), but I believe I found the root issue. See below.

/ 3600/24 = 625 W or about one hp, or 0,62 kW

In table 42, this daily usage of energy becomes an instant power, completely wrecking the calculation.  Using 0,62 kW rather than 54 000 kW makes the pumping an negligeable item.

The lighting for 3 hectares should easily be 250W

The author assumes 169 W/m2 in Table 2.

= 10 000 m2 x 3 or 7 500 kW or 7,5 MW.  They seem to have 10 MW so that works.

I think they screwed up significantly.  I'll stick with Hal Globus' numbers in table 43: 35 to 60 kW per person.


I think I found it. The author seems to have significantly miscalculated the power consumption figures of the 'reference' commercial pumps.

First the "high pressure" (aerator) gases. In Table 4, they give the power per mass flow as 177 W/(kg/day), referencing the "Blue Diamond® Enviro ETK100." The ET100 (https://www.amazon.com/Blue-Diamond-ET100-Plus-Additional/dp/B08XH6XMF3) is available, and judging by the fact that it has a replacement diaphragm kit interchangeable with the ETK100 (https://www.amazon.com/Blue-Diamond-Pumps-SKET-100/dp/B08M8ZDWFM) I believe the specs are the same.

The specs are:

Max air flow = 3.43 ft3/min
Max pressure = 0.10 bar
Electrical power = 80 watts

If we assume the standard air density of 1.225 kg/m3, that works out to... 177 kg/day (https://futureboy.us/fsp/frink.fsp?fromVal=3.54+ft%5E3%2Fmin+1.225+kg%2Fm%5E3&toVal=kg%2Fday). Hmmm, there's that number again...  ???

However when I calculate the power per mass flow, I get 0.452 watt/(kg/day) (https://futureboy.us/fsp/frink.fsp?fromVal=80+watt+%2F+%283.54+ft%5E3%2Fmin+1.225+kg%2Fm%5E3%29&toVal=watt%2F%28kg%2Fday%29). That's a lot lower than the number given in Table 4, by a factor of ~390x.


Checking the number given for low-pressure gases, the author references the JABSCO® #35440-0010 (https://marinepartssource.com/4-inch-250-cfm-flexmount-blower-24v-jabsco-35440-0010) in Table 4, and give a power per mass flow of 7.33 W/(kg/day). Plugging in the linked specs yields a value of 0.010 W/(kg/day) (https://futureboy.us/fsp/frink.fsp?fromVal=5.3+A+24+V+%2F+%28250+cfm+1.225+kg%2Fm%5E3%29&toVal=watt%2F%28kg%2Fday%29), which is ~720x lower.


Now to check out the "fan/high volume" number, which lists the Schaefer® Versa-Kool® Greenhouse Circulation Fan — 8in., 450 CFM, Model# VK8 (https://www.amazon.com/Schaefer-SCHAEFER-VERSAKOOL-PARENT/dp/B09RQLTL13) as 1.77 W/(kg/day). I get... 0.0031 W/(kg/day) (https://futureboy.us/fsp/frink.fsp?fromVal=0.6+A+115+V+%2F+%28450+cfm+1.225+kg%2Fm%5E3%29&toVal=watt%2F%28kg%2Fday%29) (~575x lower).


Finally, I ran the numbers for the "liquids (with or without solids)" listed in Table 3 as 1.151 W/(kg/day) for the Little Giant® 514420 (https://www.supplyhouse.com/Little-Giant-514420-14S-CIM-1-2-HP-100-GPM-Manual-Submersible-Sewage-Ejector-Pump-20ft-power-cord-3-Discharge-9457000-p). I get 0.0015 W/(kg/day) (https://futureboy.us/fsp/frink.fsp?fromVal=1100+W+%2F+%28133+gpm+1+kg%2Fl%29&toVal=W%2F%28kg%2Fday%29), ie ~760x lower.



"Well 'aire's yer prablem!"  :o
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/07/2023 09:02 am
Correcting Table 37

Scenario 1A: High Pressure = 359 W, Liquids = 988 W, Total = 1374 W

Scenario 1B: High Pressure = 246 W, Low Pressure = 0.1 W, High Volume = 76 W, Liquids = 678 W, Total = 1020 W

Scenario 2A: High Pressure = 2491 W, Low Pressure = 29 W, High Volume = 430 W, Liquids = 4604 W, Total = 7554 W

Scenario 2B: High Pressure = 2196 W, Low Pressure = 26 W, High Volume = 464 W, Liquids = 3784 W, Total = 6470 W

Scenario 3: High Pressure = 7200 W, Low Pressure = 126 W, High Volume = 1540 W, Liquids = 22377 W, Total = 31243 W

Scenario 4: High Pressure = 11249 W, Low Pressure = 145 W, High Volume = 3163 W, Liquids = 63363 W, Total = 77920 W

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/07/2023 09:41 am
Last one, I promise!

When correcting Table 42, note that the "circulation for heat rejection" column seems to be about 2.82x too large, for unknown reasons. See section H.

For this I'll just do the first and last scenario, and leave the others as exercises for the reader.  :)

Scenario 1A: Fluid movement = 1.37 kW, Photosynthetic light = 117 kW, Work light = 0.23 kW, Circulation for heat rejection = 26.55 kW, Total = 144.45 kW, Total per person = 1.44 kW/person (vs 10.83 kW/person)

Scenario 4: Fluid movement = 77.92 kW, Photosynthetic light = 11470 kW, Work light = 3.89 kW, Circulation for heat rejection = 530.50 kW, Total = 12082.31 kW, Total per person = 120.82 kW/person (vs 673.36 kW/person)




So fluid movement is not the "largest power consumer," in any scenario.

The scenarios which don't involve exporting food vary from 1.4 kW/person (Scenario 1A) to 47 kW/person (Scenario 3).

Total farm power consumption is overestimated by 6-8x.

This also changes the conclusion in Table 44. Rather than the solar panels being "many multiples of the size of the farm itself," some scenarios have the solar panels smaller than the farm area.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/07/2023 08:13 pm
Last one, I promise!

When correcting Table 42, note that the "circulation for heat rejection" column seems to be about 2.82x too large, for unknown reasons. See section H.

For this I'll just do the first and last scenario, and leave the others as exercises for the reader.  :)

Scenario 1A: Fluid movement = 1.37 kW, Photosynthetic light = 117 kW, Work light = 0.23 kW, Circulation for heat rejection = 26.55 kW, Total = 144.45 kW, Total per person = 1.44 kW/person (vs 10.83 kW/person)

Scenario 4: Fluid movement = 77.92 kW, Photosynthetic light = 11470 kW, Work light = 3.89 kW, Circulation for heat rejection = 530.50 kW, Total = 12082.31 kW, Total per person = 120.82 kW/person (vs 673.36 kW/person)




So fluid movement is not the "largest power consumer," in any scenario.

The scenarios which don't involve exporting food vary from 1.4 kW/person (Scenario 1A) to 47 kW/person (Scenario 3).

Total farm power consumption is overestimated by 6-8x.

This also changes the conclusion in Table 44. Rather than the solar panels being "many multiples of the size of the farm itself," some scenarios have the solar panels smaller than the farm area.
That last paragraph doesn't stand up to a non math sanity check. Assume a one hectare PV farm working at 100% conversion. Assume a one hectare indoor food farm with lighting powered by the one hectare PV farm. Assume no transmission losses and 100% conversion of electricity to light.


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/07/2023 08:30 pm


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
Although all the errors make this paper very suspect, the earlier scenarios do not use light to produce food.  They use bioreactors, that theoretically, in some cases, can be more efficient that photosynthesis.
You end up surviving on Marmite and algae, or Vegemite if your are Australian.  Not fun.  And no doubt will eventually run into severe vitamin deficiencies.  And go mad from culinary boredom.
Title: Re: Power options for a Mars settlement
Post by: Greg Hullender on 02/07/2023 09:07 pm

That last paragraph doesn't stand up to a non math sanity check. Assume a one hectare PV farm working at 100% conversion. Assume a one hectare indoor food farm with lighting powered by the one hectare PV farm. Assume no transmission losses and 100% conversion of electricity to light.


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
But most plants can only use ~10% of full mid-day sunlight intensity (https://en.wikipedia.org/wiki/Photosynthetic_efficiency). So if you have very efficient solar panels and very efficient, targeted LED lights for the plants, then a given area of solar panels could, in theory, support a much larger area of crops.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/07/2023 11:22 pm

That last paragraph doesn't stand up to a non math sanity check. Assume a one hectare PV farm working at 100% conversion. Assume a one hectare indoor food farm with lighting powered by the one hectare PV farm. Assume no transmission losses and 100% conversion of electricity to light.


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
But most plants can only use ~10% of full mid-day sunlight intensity (https://en.wikipedia.org/wiki/Photosynthetic_efficiency). So if you have very efficient solar panels and very efficient, targeted LED lights for the plants, then a given area of solar panels could, in theory, support a much larger area of crops.
Looking at the Wikipedia article it's more like 1-2% efficiency energy conversion efficiency for crops, with most plants much lower than that.  The 10% is the best they do during the day.  Most of time they don't reach that.  The 1-2% is the efficiency to convert into biomass.  For almost all crops, the edible food portion is less than 50%, with most of it going into undigestible fiber.  Plus the plant needs to feed itself, using energy for its own processes.  So the food production efficiency is actually 1% and less. 
Power on Mars will be build around food.  Well, perhaps around fuel production for the first few years, but if there ever is a real settlement on Mars, plan for it using most of it's energy to produce food.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/07/2023 11:23 pm
Last one, I promise!

When correcting Table 42, note that the "circulation for heat rejection" column seems to be about 2.82x too large, for unknown reasons. See section H.

For this I'll just do the first and last scenario, and leave the others as exercises for the reader.  :)

Scenario 1A: Fluid movement = 1.37 kW, Photosynthetic light = 117 kW, Work light = 0.23 kW, Circulation for heat rejection = 26.55 kW, Total = 144.45 kW, Total per person = 1.44 kW/person (vs 10.83 kW/person)

Scenario 4: Fluid movement = 77.92 kW, Photosynthetic light = 11470 kW, Work light = 3.89 kW, Circulation for heat rejection = 530.50 kW, Total = 12082.31 kW, Total per person = 120.82 kW/person (vs 673.36 kW/person)




So fluid movement is not the "largest power consumer," in any scenario.

The scenarios which don't involve exporting food vary from 1.4 kW/person (Scenario 1A) to 47 kW/person (Scenario 3).

Total farm power consumption is overestimated by 6-8x.

This also changes the conclusion in Table 44. Rather than the solar panels being "many multiples of the size of the farm itself," some scenarios have the solar panels smaller than the farm area.
That last paragraph doesn't stand up to a non math sanity check.

I just scaled the numbers in the paper by the reduction in electrical power.  I didn't double-check it since I didn't feel like doing any more homework just then. I will remedy my deficiency momentarily. ;)

Assume a one hectare PV farm working at 100% conversion. Assume a one hectare indoor food farm with lighting powered by the one hectare PV farm. Assume no transmission losses and 100% conversion of electricity to light.


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.

Let's try to reproduce the paper's calculation.

The author reference LED panels (the VividGro V2 (https://photonicled.com/products/copy-of-vividgro-v1-fixture-led-grow-light)), which are spectrum-matched. They use a figure of 588 W per fixture and 169 watt/m2, which implies each grow lamp illuminates 3.5 m2.

The manufacturer seems to be defunct (always a good sign ::) ), but the dimensions are given elsewhere (perhaps incorrectly) as 43 x 24 x 5 inches (https://sasquatchsoil.co/product/vividgro-v2-fixture/). I believe the authors used 48 x 24 inches, because this (along with the spill from a 65 degree beam angle diverging over the 30 inch height) yields the 3.5 m2 value in the paper.

The lamp puts out 1081 μmol/s (the spec sheets erroneously lists the units as μmol/J, another good sign), that means the system delivers an average PPFD (photosynthetic photon flux density) of 309 μmol/m2/s for the grow area.

While this is much less than 2000 μmol/m2/s for direct sunlight on Earth, most controlled environment agriculture systems run at lower values. This seems very low, however.

It is difficult to check whether the author's assumptions about the yield of potatoes, tomatoes, etc are realistic given these PPFDs, because I can't seem to find where they cite their yield numbers.  :-\


Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 02/08/2023 06:51 am


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
Although all the errors make this paper very suspect, the earlier scenarios do not use light to produce food.  They use bioreactors, that theoretically, in some cases, can be more efficient that photosynthesis.
You end up surviving on Marmite and algae, or Vegemite if your are Australian.  Not fun.  And no doubt will eventually run into severe vitamin deficiencies.  And go mad from culinary boredom.

Quorn uses maize glucose as a feedstock, at 31% caloric conversion efficiency. It's only a carbohydrate to protein converter, which is also handled by simpler (and smellier) feed conversion systems.

A major problem is that their efficiency is effectively capped by the fact that 30% of their biomass is nucleic acid, which must be removed otherwise we get gout from uric acid crystals. This is a peculiarity of human metabolism: other vertebrates can convert the sparingly soluble uric acid to the very soluble acid allantoin. This biomass effectively has to be dumped.

Other energy is still required in the form of ammonia, 40–45 GJ/tNH3 for electrolysis-based production, excluding Mars-related concerns like sourcing, melting ice, heat management. Ammonia otherwise must be produced somehow from biowaste. I'm not sure what the ammonia input to protein output is.

Other mycoprotein options are based on the degradation of plant waste, which seems to be where they get their nitrogen. But plants remain the gateway for energy input for our food cycle, and they need light.

Ammonia:
https://www.frontiersin.org/articles/10.3389/fenrg.2021.580808/full
https://www.frontiersin.org/articles/10.3389/fceng.2021.765457/full

Quorn:
https://controlledmold.com/quorn-a-story-about-single-cell-protein/
http://www.davidmoore.org.uk/21st_century_guidebook_to_fungi_platinum/Ch17_18.htm
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 02/08/2023 07:13 am

That last paragraph doesn't stand up to a non math sanity check. Assume a one hectare PV farm working at 100% conversion. Assume a one hectare indoor food farm with lighting powered by the one hectare PV farm. Assume no transmission losses and 100% conversion of electricity to light.


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
But most plants can only use ~10% of full mid-day sunlight intensity (https://en.wikipedia.org/wiki/Photosynthetic_efficiency). So if you have very efficient solar panels and very efficient, targeted LED lights for the plants, then a given area of solar panels could, in theory, support a much larger area of crops.
Looking at the Wikipedia article it's more like 1-2% efficiency energy conversion efficiency for crops, with most plants much lower than that.  The 10% is the best they do during the day.  Most of time they don't reach that.  The 1-2% is the efficiency to convert into biomass.  For almost all crops, the edible food portion is less than 50%, with most of it going into undigestible fiber.  Plus the plant needs to feed itself, using energy for its own processes.  So the food production efficiency is actually 1% and less. 
Power on Mars will be build around food.  Well, perhaps around fuel production for the first few years, but if there ever is a real settlement on Mars, plan for it using most of it's energy to produce food.


My first thought looking at that is that waste heat is going to be a huge problem with solar–>LED–>plants. Those underground greenhouses will get hot, and there will be a lot of wiring in places that may have unpredictable condensation, lower air pressure, under constant stress to maximally produce. That to me sounds like accidents waiting to happen, even with "a culture of safety". Best part is no part.

A simple setup of solar concentrators (even non-tracking, like a periscope) could get sunlight to plants with minimum fuss and with minimal glass% pressure vessel composition. There are also quantum dot coatings for greenhouses that switch down photon wavelengths to more useful ones – eg, UV–>orange light. Scattered waste light may also be put to use somehow. Eg solar panels on the inside of the mostly opaque greenhouses, though re-reflectance from white walls may be a better option. Heat distribution could be handled with approaches to structure design that take advantage of convection and also put it to some other use. Like the way conservatories in high latitudes are also a passive heat source for the house. Lots of ways to handle that smartly, some of which are also applicable to LED systems, which will likely remain a part of food production.

These plant yield estimates are likely all too optimistic. They're growing in radiation and reduced gravity. Reduced yields means massive investment in more solar panels, more power distribution, more LEDs, more radiators (+- internal heat use), more pressure vessels. Using passive solar, you just need to invest in more pressure vessels.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/08/2023 07:19 pm

That last paragraph doesn't stand up to a non math sanity check. Assume a one hectare PV farm working at 100% conversion. Assume a one hectare indoor food farm with lighting powered by the one hectare PV farm. Assume no transmission losses and 100% conversion of electricity to light.


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
But most plants can only use ~10% of full mid-day sunlight intensity (https://en.wikipedia.org/wiki/Photosynthetic_efficiency). So if you have very efficient solar panels and very efficient, targeted LED lights for the plants, then a given area of solar panels could, in theory, support a much larger area of crops.
Looking at the Wikipedia article it's more like 1-2% efficiency energy conversion efficiency for crops, with most plants much lower than that.  The 10% is the best they do during the day.  Most of time they don't reach that.  The 1-2% is the efficiency to convert into biomass.  For almost all crops, the edible food portion is less than 50%, with most of it going into undigestible fiber.  Plus the plant needs to feed itself, using energy for its own processes.  So the food production efficiency is actually 1% and less. 
Power on Mars will be build around food.  Well, perhaps around fuel production for the first few years, but if there ever is a real settlement on Mars, plan for it using most of it's energy to produce food.
Where does efficiency hit if CO2 scrubbing/O2 production is folded in? There are some other factors that don't easily reduce to numbers.


IMO, the mess/lounge area would best be co-located with a crop area. It's as close as they'll get to outdoors and fresh air. Good for the spirits, but no way to fit it into an efficiency calculation.


I can even see small plots set aside for personal gardens well before survival is assured, and to hell with efficiency. It's too therapeutic to pass up. I'll trade you a bulb of garlic and two cayennes for two ears of corn and a carrot. The other bozo's can try to live on Vegemite, if ya call that living.


Hmmm. Is living in a spacesuit and eating garlic a bad thing? Maybe I'm wandering a bit too far off topic.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/08/2023 09:39 pm

That last paragraph doesn't stand up to a non math sanity check. Assume a one hectare PV farm working at 100% conversion. Assume a one hectare indoor food farm with lighting powered by the one hectare PV farm. Assume no transmission losses and 100% conversion of electricity to light.


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
But most plants can only use ~10% of full mid-day sunlight intensity (https://en.wikipedia.org/wiki/Photosynthetic_efficiency). So if you have very efficient solar panels and very efficient, targeted LED lights for the plants, then a given area of solar panels could, in theory, support a much larger area of crops.
Looking at the Wikipedia article it's more like 1-2% efficiency energy conversion efficiency for crops, with most plants much lower than that.  The 10% is the best they do during the day.  Most of time they don't reach that.  The 1-2% is the efficiency to convert into biomass.  For almost all crops, the edible food portion is less than 50%, with most of it going into undigestible fiber.  Plus the plant needs to feed itself, using energy for its own processes.  So the food production efficiency is actually 1% and less. 
Power on Mars will be build around food.  Well, perhaps around fuel production for the first few years, but if there ever is a real settlement on Mars, plan for it using most of it's energy to produce food.
Where does efficiency hit if CO2 scrubbing/O2 production is folded in? There are some other factors that don't easily reduce to numbers.


IMO, the mess/lounge area would best be co-located with a crop area. It's as close as they'll get to outdoors and fresh air. Good for the spirits, but no way to fit it into an efficiency calculation.


I can even see small plots set aside for personal gardens well before survival is assured, and to hell with efficiency. It's too therapeutic to pass up. I'll trade you a bulb of garlic and two cayennes for two ears of corn and a carrot. The other bozo's can try to live on Vegemite, if ya call that living.


Hmmm. Is living in a spacesuit and eating garlic a bad thing? Maybe I'm wandering a bit too far off topic.
As this thread is about a settlement and not a mere base, that could be fed from Earth, a lot of food production is required.  Plants can recycle CO2 and produce oxygen, in fact they can overproduce oxygen and run out of CO2, in particular for small installations.  So for a settlement CO2 control will be by food production, but with backup systems and chemical analogs to take up the slack when needed.  The energy needed would be a tiny fraction of the light required, so a tiny fraction of overall power.
It makes a lot of sense to have plants in the habitats, both for psychological reasons and as small scale food production.  It also makes a lot of sense to have a lot of strong lighting in the habitats, to avail the strip mall and hotel corridor effects.  You will then want a lot of ventilation to move the air around and in particular to handle the humidity from the plants.  So that does require a certain amount of energy.  But very small compared to growing the food and producing return propellant.
Some garlic would definitively be a great idea.  But also a regenerative type of filter (activated charcoal?) for organic compounds, to control odors over time.

A very important aspect for all this will be cooling.  For  well insulated base, cooling will be a big deal.  Fortunately, it's kind of cold outside, so that will help.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 02/08/2023 09:49 pm
I actually think you’d want a separate system for most of the base vs the greenhouse. Humans have optimal mental clarity at low CO2 levels (think pre-industrial 280ppm) whereas plants have optimal growth at very high CO2 levels where humans would perceive as very stuffy, like 1000-1500ppm.

This is one way where a Mars settlement could actually have a better environment than Earth’s, for both plants and humans (which optimize in opposite directions).
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/08/2023 10:21 pm
I actually think you’d want a separate system for most of the base vs the greenhouse. Humans have optimal mental clarity at low CO2 levels (think pre-industrial 280ppm) whereas plants have optimal growth at very high CO2 levels where humans would perceive as very stuffy, like 1000-1500ppm.

This is one way where a Mars settlement could actually have a better environment than Earth’s, for both plants and humans (which optimize in opposite directions).
I think it's a mistake to try to optimize everything  ;D.

I absolutely agree that the majority of food production needs to be on its own.  However house plants and flowers need to be in the environment as well.  And a significant amount of power should be spent on lighting. Although humans can get by on very little, and plants can also survive with very low light levels, I thing mental clarity and joy will come from more illumination!!  So let's provide for a lot of light in common areas.  A lot more than what is usual in buildings, because we will net really have an outdoors on Mars.  We have to have the outdoors indoors, and that means lots'a lights!
Title: Re: Power options for a Mars settlement
Post by: Asteroza on 02/09/2023 01:48 am


In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.
Although all the errors make this paper very suspect, the earlier scenarios do not use light to produce food.  They use bioreactors, that theoretically, in some cases, can be more efficient that photosynthesis.
You end up surviving on Marmite and algae, or Vegemite if your are Australian.  Not fun.  And no doubt will eventually run into severe vitamin deficiencies.  And go mad from culinary boredom.

Quorn uses maize glucose as a feedstock, at 31% caloric conversion efficiency. It's only a carbohydrate to protein converter, which is also handled by simpler (and smellier) feed conversion systems.

A major problem is that their efficiency is effectively capped by the fact that 30% of their biomass is nucleic acid, which must be removed otherwise we get gout from uric acid crystals. This is a peculiarity of human metabolism: other vertebrates can convert the sparingly soluble uric acid to the very soluble acid allantoin. This biomass effectively has to be dumped.

Other energy is still required in the form of ammonia, 40–45 GJ/tNH3 for electrolysis-based production, excluding Mars-related concerns like sourcing, melting ice, heat management. Ammonia otherwise must be produced somehow from biowaste. I'm not sure what the ammonia input to protein output is.

Other mycoprotein options are based on the degradation of plant waste, which seems to be where they get their nitrogen. But plants remain the gateway for energy input for our food cycle, and they need light.

Ammonia:
https://www.frontiersin.org/articles/10.3389/fenrg.2021.580808/full
https://www.frontiersin.org/articles/10.3389/fceng.2021.765457/full

Quorn:
https://controlledmold.com/quorn-a-story-about-single-cell-protein/
http://www.davidmoore.org.uk/21st_century_guidebook_to_fungi_platinum/Ch17_18.htm

I had been under the impression that the USSR, in follow-on research from their earlier work with bulk single cell protein production from oil refinery hydrocarbon substrates (BVK), had achieved bioreactor production using only gas and electricity inputs, but I can't seem to find a good reference of that.

There's a finnish startup working the electricity+water(electrolyzed)+CO2 input bioreactor angle from research in 2017 though, creating a SCP product called Solein

https://en.wikipedia.org/wiki/Solar_Foods (https://en.wikipedia.org/wiki/Solar_Foods)
https://solarfoods.com/ (https://solarfoods.com/)
this article mentions
https://www.thechemicalengineer.com/news/protein-made-using-co2-and-electricity/ (https://www.thechemicalengineer.com/news/protein-made-using-co2-and-electricity/)
24 kWh of electricity per kg of cells (not sure if that's powdered cell mass or not but probably so)(still needs post processing into usable food...)

There are a few companies working the methane input bioreactor angle, notably Unibio
https://www.unibio.dk/ (https://www.unibio.dk/)

There is a relevant question here, whether you should focus on a water input or a methane input bioreactor system. Mining water leads to direct inputs, but you need a methane infrastructure for going back to space ( which itself uses water for sabatier reactions) so methane is readily available.

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/11/2023 01:38 am
My first thought looking at that is that waste heat is going to be a huge problem with solar–>LED–>plants. Those underground greenhouses will get hot, and there will be a lot of wiring in places that may have unpredictable condensation, ...

... Heat distribution could be handled with approaches to structure design that take advantage of convection and also put it to some other use. Like the way conservatories in high latitudes are also a passive heat source for the house. Lots of ways to handle that smartly, some of which are also applicable to LED systems, which will likely remain a part of food production.

One issue is that ~50% of this waste heat is in the form of latent heat (transpired humidity). This must be removed, or photosynthesis shuts down. So we need to either

  1) use electricity for dehumidifiers to turn that latent heat back into sensible heat (eg to heat the habitat next door), or

  2) use passive cooling for the dehumidifiers, and simply dumping that sensible heat from hot to cold.


Either way you get an ~unlimited supply of distilled water (recycled from potentially dirty irrigation water) without the need to clean and de-foul a large evaporator surface, which is a nice bonus.

(this huge energy flow directed into distillation is another factor not captured in the typical "efficiency" number for photosynthesis...)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/11/2023 01:48 am
I actually think you’d want a separate system for most of the base vs the greenhouse. Humans have optimal mental clarity at low CO2 levels (think pre-industrial 280ppm) whereas plants have optimal growth at very high CO2 levels where humans would perceive as very stuffy, like 1000-1500ppm.


That implies that there's a separate mechanical CO2 scrubber that can "pump" CO2 (against the concentration gradient) into the grow chamber.

I suspect it will be the other way around: the CO2 will be higher in the crew area (a net CO2 source) and lower in the greenhouse (a net CO2 sink).


For the record, the ISS is maintained at 2000-5000 ppm CO2. This is done to maximize the number of crew the CO2 scrubber can support.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/11/2023 02:19 am
I actually think you’d want a separate system for most of the base vs the greenhouse. Humans have optimal mental clarity at low CO2 levels (think pre-industrial 280ppm) whereas plants have optimal growth at very high CO2 levels where humans would perceive as very stuffy, like 1000-1500ppm.


That implies that there's a separate mechanical CO2 scrubber that can "pump" CO2 (against the concentration gradient) into the grow chamber.

I suspect it will be the other way around: the CO2 will be higher in the crew area (the CO2 source) and lower in the greenhouse (the CO2 sink).


For the record, the ISS is maintained at 4000-5000 ppm CO2. This is done to maximize the number of crew the CO2 scrubber can support.
It's not necessarily a rational choice, but schools in Quebec now have CO2 monitors and are aiming for 1000 ppm.

I think we do not fully realize the fact that life is not just people and plants.  There is all the rest of the biome that is required to get everything into equilibrium.  We are going to have to allocate power to support life forms that are not us, tomatoes and yeast.  Perhaps not the first few years, but probably fairly soon.  As all the rest of life shown in the joined graph.

In a study of the Mars one life support, it was determined that the life support system would produce too much oxygen: Do, Sydney, Koki Ho, Samuel Steven Schreiner, Andrew Charles Owens, and Olivier L. de Weck. "An independent assessment of the technical feasibility of the mars one mission plan." (2014). 
So I agree, the CO2 level in the plant area will be low if left to itself.  We are going to have to maintain equilibrium artificially.  In fact, we will have to extract CO2 from the atmosphere to feed the plants, to eventually feed the colonists.  An to create soil, to feed fun plants that are more interesting than strawberries and tomatoes, such as wheat  ;D

As far as I've been able to determine, any sizable settlement will be a net oxygen producer, separating oxygen from hydrogen, carbon, iron and aluminum and eventually Silicon.  Oxygen will be the top waste product on Mars.

From the point of view of energy use, these are all processes that will require significant energy inputs.  Deoxidize Mars should be our slogan.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/11/2023 03:21 am
As this thread is about a settlement and not a mere base, that could be fed from Earth, a lot of food production is required.  Plants can recycle CO2 and produce oxygen, in fact they can overproduce oxygen and run out of CO2, in particular for small installations.  So for a settlement CO2 control will be by food production, but with backup systems and chemical analogs to take up the slack when needed.  The energy needed would be a tiny fraction of the light required, so a tiny fraction of overall power.
It makes a lot of sense to have plants in the habitats, both for psychological reasons and as small scale food production.  It also makes a lot of sense to have a lot of strong lighting in the habitats, to avail the strip mall and hotel corridor effects.  You will then want a lot of ventilation to move the air around and in particular to handle the humidity from the plants.  So that does require a certain amount of energy.  But very small compared to growing the food and producing return propellant.
Some garlic would definitively be a great idea.  But also a regenerative type of filter (activated charcoal?) for organic compounds, to control odors over time.

A very important aspect for all this will be cooling.  For  well insulated base, cooling will be a big deal.  Fortunately, it's kind of cold outside, so that will help.

Having plants in the living space is important. Not just ornamental, they should ideally be functional and productive plants too: herbs, medicines, materials, fibers, support species, etc. "Spilled" light goes from wasted energy to aesthetic dappled illumination (no purple please). Close proximity with people maximizes psychological benefits, and the plants also benefit from opportunistic care and harvesting.

Efficient multi-functional design!


There's a steady supply of activated charcoal "for free" from waste plant material through pyrolysis (aka biochar). Besides recycling valuable nitrogen and hydrogen, this process also consumes excess oxygen production and generates heat energy.

Of course you can use this as a type of energy storage. Build up a buffer of dried plant material + LOX in the energy-rich summer, and burn it in the winter (or dust storm season).

After it's used in air/water filters, the charcoal can be re-activated and reused several times. It loses mass each time, slowly turning back into CO2. The ciiiircle of liiiife.....

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/11/2023 03:51 am
...

For the record, the ISS is maintained at 4000-5000 ppm CO2. This is done to maximize the number of crew the CO2 scrubber can support.
It's not necessarily a rational choice, but schools in Quebec now have CO2 monitors and are aiming for 1000 ppm.

I'm sure it's a very rational choice when you can inexpensively draw in low-CO2 air from the outside, effectively leaching off biosphere services we don't have to explicitly pay for.

On Mars the cost structure will be very different, so the "rational" choice will shift.


So I agree, the CO2 level in the plant area will be low if left to itself.  We are going to have to maintain equilibrium artificially.  In fact, we will have to extract CO2 from the atmosphere to feed the plants, to eventually feed the colonists.  An to create soil, to feed fun plants that are more interesting than strawberries and tomatoes, such as wheat  ;D

You beat me to it! Yes, pumping in Martian atmospheric CO2 is a necessity.

You don't necessarily need a continuous input if you pyrolyze all your uneaten plant biomass. But I suspect you'd do it anyway, just because it's such a cheap way to create biomass — that's the whole point, after all!

Compared to water ice mining/drilling/rodwells or plastic synthesis or hydrogen-smelting steel, "pump CO2 into the greenhouse" is on the easier end of the ISRU Hardness Scale.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/12/2023 04:29 pm
In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.

Although all the errors make this paper very suspect, the earlier scenarios do not use light to produce food.  They use bioreactors...

Twark_Main ran with your vague criticism of Meyer's numbers, but that led him into a huge ISS power discrepancy (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241).  He's off by an order of magnitude.  Can you fix that, concisely?  The forum doesn't need weeks of back-and-forth on basic power numbers.

Or just ask the author at NSS (https://isdc2021.nss.org/home/schedule/speakers/bryce-l-meyer/). 
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/12/2023 04:47 pm
What you are saying is just wrong, but you constantly repeat it. The figure of Watt-hours is integrated received power that day, NOT battery state of charge. Quit accusing others of ignoring something which is really just you misinterpreting something clear as day.
OK that makes a bit more sense.

The units are still quite odd.

So the average that day should be that figure divided by 24? that would give 0.9167w as the average PV array output.

Which doesn't seem like much.

Technically divided by 24.66 hours. ;)

And yes, it's not much. That power output was measured during a very dark dust storm.

No, my posts on the rover's power crisis were correct; e.g., noting that the rover reported current (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309646#msg2309646), not power, and never beyond tau 10.8, where it failed.  Posters ignored many references there, while echoing obvious mistakes. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/12/2023 05:08 pm
In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.

Although all the errors make this paper very suspect, the earlier scenarios do not use light to produce food.  They use bioreactors...

Twark_Main ran with your vague criticism of Meyer's numbers, but that led him into a huge ISS power discrepancy (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241).  He's off by an order of magnitude.  Can you fix that, concisely?  The forum doesn't need weeks of back-and-forth on basic power numbers.

Or just ask the author at NSS (https://isdc2021.nss.org/home/schedule/speakers/bryce-l-meyer/).
I did ask.  Got no reply.  The comment box at NSS seems to be broken. 
I refer you to page 115 of this thread, were I check the calculations that bugged me the most and find them wrong.  Twark_Main checked other elements in a different method and also found them to be wrong.
So I an not using this paper as a useful reference.  It is not my job to fix it.  I think it is enough that I warned others not to use it.  I will not back and forth on it, as there is so little value in its conclusions.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/12/2023 05:13 pm
In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.

Although all the errors make this paper very suspect, the earlier scenarios do not use light to produce food.  They use bioreactors...

Twark_Main ran with your vague criticism of Meyer's numbers, but that led him into a huge ISS power discrepancy (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241).  He's off by an order of magnitude.  Can you fix that, concisely?  The forum doesn't need weeks of back-and-forth on basic power numbers.

Or just ask the author at NSS (https://isdc2021.nss.org/home/schedule/speakers/bryce-l-meyer/).

I did ask.  Got no reply.  The comment box at NSS seems to be broken. 
I refer you to page 115 of this thread, were I check the calculations that bugged me the most and find them wrong.  Twark_Main checked other elements in a different method and also found them to be wrong.
So I an not using this paper as a useful reference.  It is not my job to fix it.  I think it is enough that I warned others not to use it.  I will not back and forth on it, as there is so little value in its conclusions.

No, you both ignored the actual, simplest known case.  Why is Twark_Main's Scenario 1A result off by an order of magnitude, unlike Meyer's?  Your posts are assumed wrong if you can't explain.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/12/2023 05:26 pm
In this perfect but non existent world the PV area to food area ratio would be 1:1. The only wiggle room I can come up with would be the lighting putting out better optimized growing spectrum.

Although all the errors make this paper very suspect, the earlier scenarios do not use light to produce food.  They use bioreactors...

Twark_Main ran with your vague criticism of Meyer's numbers, but that led him into a huge ISS power discrepancy (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241).  He's off by an order of magnitude.  Can you fix that, concisely?  The forum doesn't need weeks of back-and-forth on basic power numbers.

Or just ask the author at NSS (https://isdc2021.nss.org/home/schedule/speakers/bryce-l-meyer/).

I did ask.  Got no reply.  The comment box at NSS seems to be broken. 
I refer you to page 115 of this thread, were I check the calculations that bugged me the most and find them wrong.  Twark_Main checked other elements in a different method and also found them to be wrong.
So I an not using this paper as a useful reference.  It is not my job to fix it.  I think it is enough that I warned others not to use it.  I will not back and forth on it, as there is so little value in its conclusions.

No, you both ignored the actual, simplest known case.  Why is Twark_Main's Scenario 1A result off by an order of magnitude, unlike Meyer's?  Your posts are assumed wrong if you can't explain the simplest case.
That doesn't make sense.  The first case 1a is not the simplest case, it is just the lowest power one, and it is the lowest power one because the author made huge mistakes with pumping calculation.
It is in fact a rather hard case to evaluate because it deals with biorectors, that are not common, and in fact rather speculative to start with.
Before calculating the cases, the author needs to calculate the parameters adequately.  And he doesn't.  So all the cases are wrong.  I use the last case because the error is so glaringly obvious.
Please read table 42 in the paper.  54 000 kW for fluid movement is almost 40 000 horsepower.  It's a pump much larger than a house.  To pump water for three hectares.  It is an absurd result.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/12/2023 05:36 pm
Has this reactor been discussed before?  It seems much more interesting than Kilopower, but also much less real.
https://www.tandfonline.com/doi/epdf/10.1080/00295450.2022.2072649

2 MW electrical is pretty good.
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/12/2023 05:48 pm
Twark_Main ran with your vague criticism of Meyer's numbers, but that led him into a huge ISS power discrepancy (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241).  He's off by an order of magnitude.  Can you fix that, concisely?  The forum doesn't need weeks of back-and-forth on basic power numbers.

Or just ask the author at NSS (https://isdc2021.nss.org/home/schedule/speakers/bryce-l-meyer/).

I did ask.  Got no reply.  The comment box at NSS seems to be broken. 
I refer you to page 115 of this thread, were I check the calculations that bugged me the most and find them wrong.  Twark_Main checked other elements in a different method and also found them to be wrong.
So I an not using this paper as a useful reference.  It is not my job to fix it.  I think it is enough that I warned others not to use it.  I will not back and forth on it, as there is so little value in its conclusions.

No, you both ignored the actual, simplest known case.  Why is Twark_Main's Scenario 1A result off by an order of magnitude, unlike Meyer's?  Your posts are assumed wrong if you can't explain the simplest case.

That doesn't make sense.  The first case 1a is not the simplest case, it is just the lowest power one, and it is the lowest power one because the author made huge mistakes with pumping calculation.
It is in fact a rather hard case to evaluate because it deals with biorectors, that are not common, and in fact rather speculative to start with.
Before calculating the cases, the author needs to calculate the parameters adequately.  And he doesn't.  So all the cases are wrong.  I use the last case because the error is so glaringly obvious.
Please read table 42 in the paper.  54 000 kW for fluid movement is almost 40 000 horsepower.  It's a pump much larger than a house.  To pump water for three hectares.  It is an absurd result.

ISS (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241) is the known case, with obvious similarities.  Don't hand-wave; you two should work out your big 1A / ISS power discrepancy in PM before posting more power criticisms.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/13/2023 02:08 am
Twark_Main ran with your vague criticism of Meyer's numbers, but that led him into a huge ISS power discrepancy (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241).  He's off by an order of magnitude.  Can you fix that, concisely?  The forum doesn't need weeks of back-and-forth on basic power numbers.

Or just ask the author at NSS (https://isdc2021.nss.org/home/schedule/speakers/bryce-l-meyer/).

I did ask.  Got no reply.  The comment box at NSS seems to be broken. 
I refer you to page 115 of this thread, were I check the calculations that bugged me the most and find them wrong.  Twark_Main checked other elements in a different method and also found them to be wrong.
So I an not using this paper as a useful reference.  It is not my job to fix it.  I think it is enough that I warned others not to use it.  I will not back and forth on it, as there is so little value in its conclusions.

No, you both ignored the actual, simplest known case.  Why is Twark_Main's Scenario 1A result off by an order of magnitude, unlike Meyer's?  Your posts are assumed wrong if you can't explain the simplest case.

That doesn't make sense.  The first case 1a is not the simplest case, it is just the lowest power one, and it is the lowest power one because the author made huge mistakes with pumping calculation.
It is in fact a rather hard case to evaluate because it deals with biorectors, that are not common, and in fact rather speculative to start with.
Before calculating the cases, the author needs to calculate the parameters adequately.  And he doesn't.  So all the cases are wrong.  I use the last case because the error is so glaringly obvious.
Please read table 42 in the paper.  54 000 kW for fluid movement is almost 72 000 horsepower.  It's a pump much larger than a house.  To pump water for three hectares.  It is an absurd result.

ISS (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241) is the known case, with obvious similarities.  Don't hand-wave; you two should work out your big 1A / ISS power discrepancy in PM before posting more power criticisms.
Meyer's calculations for case 1A and all the other cases are incorrect. 

The lighting calculation is correct:

286 m2 x 120 W/m2 = 34 286 W  in table 39
He then adds the other loads for a total of 116 793 W, or 117 kW that he writes in table 42.

So far so good.

The pumping calculation is incorrect:

1.151 W/kg/day x 649 208 kg/day = 750 722 Watts in table 37
He then adds the other load (gases) for a total of 890 738 W, or 891 kW that he writes into table 42.

But that is wrong, because the Little Giant pump has a very different power than what Meyer's proposes:
It's a 1/2 hp pump, so 373 Watts.  At 132 usgpm, or 8,35 kg/s.  That's 721823 kg/day.  373W / 721823kg/day = 0,00052 W/kg/day.  Not 1.151 W/kg/day

So that is a difference of 1.151 / 0,00052 = 2227 times more power than the real pumping power.

Meyer's pumping power is completely off, by a factor of over 2000, for all his calculations, and Mark_Twain is correct, since all the other coefficient have similar mistakes.  Pumping power goes away and all that is left is lighting.

As per your own evaluation, Meyer's power is ten times lower than the average ISS power.  So he is completely off the mark, according to your own parameters. 

Looking at it another way, to check the assumptions, in table 11 Meyers says 1a requires 649 208 kg/day.  So 649 208 l/day / 86400 = 7,5 l/s = 118 usgpm.  This is not in alignement with a 891 kW pump (1000 hp imperial).  Because if we go back to the little giant, it just requires 1/2 hp for 132 usgpm.

So Meyer's is wrong, Twain is right.  I was wrong to assume an error in logic, it was even more basic than that, probably some kind of conversion mistake.  It would be fairly simple for Meyer's to correct his tables, because otherwise it seems to be interesting work.

I'll see if I can reach him somehow.  It would be sad to not put all this to good use.

Edit: Found him on Linkedin! Left a note, hope he responds.  https://www.linkedin.com/in/bryce-meyer-88863a1/
Title: Re: Power options for a Mars settlement
Post by: LMT on 02/13/2023 03:44 am
That's... 0,00052 W/kg/day.  Not 1.151 W/kg/day...

...probably some kind of conversion mistake...

The engineer didn't hand you the pump coefficient formula because you didn't ask.  Who's more likely to have a "conversion mistake"?

And remember:  You two still have a huge unexplained power discrepancy relative to ISS reality.  Not Meyer.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/13/2023 12:13 pm
That's... 0,00052 W/kg/day.  Not 1.151 W/kg/day...

...probably some kind of conversion mistake...

The engineer didn't hand you the pump coefficient formula because you didn't ask.  Who's more likely to have a "conversion mistake"?

And remember:  You two still have a huge unexplained power discrepancy relative to ISS reality.  Not Meyer.
If we’re doing appeal to authority I’m a mechanical engineer and I calculate pumps practically every day.  Meyer is an electrical engineer and may not be in the power field at all.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/13/2023 01:29 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 02/13/2023 01:52 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
Title: Re: Power options for a Mars settlement
Post by: Greg Hullender on 02/13/2023 02:03 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
I wonder why the solar cells need a glass cover.
Quote
For protection from the harsh lunar environment, solar cells need cover glass; without it, they would only last for days.
Surely they aren't subliming into the vacuum. Are they?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/13/2023 04:21 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
Absolutely, makes little sense in the short term for Mars, just looking to the future and eventual autonomy.  And the purity is, perhaps, similar to the one required for microprocessor fabrication, that is also a mid to long term application.  Might be interesting short term for large space power satellites but that is another subject!
And if they can make very pure silicon, they might also be able to make very pure glass, and that might make a difference in the capability to produce greenhouses with local materials?  Although re-oxydizing the siliconis probably not an energy efficient process at all!
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 02/13/2023 04:47 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
I wonder why the solar cells need a glass cover.
Quote
For protection from the harsh lunar environment, solar cells need cover glass; without it, they would only last for days.
Surely they aren't subliming into the vacuum. Are they?
The Moon actually has an "atmosphere": i.e., more molecules per m3 than you find in LLO or beyond, and that atmosphere will increase as human activity increases. It includes stuff like rocket exhaust and various outgassing. I think this will be enough contamination to eventually degrade an unprotected semiconductor, especially near landing sites.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 02/13/2023 04:50 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
I wonder why the solar cells need a glass cover.
Quote
For protection from the harsh lunar environment, solar cells need cover glass; without it, they would only last for days.
Surely they aren't subliming into the vacuum. Are they?
Hard UV and high energy electrons. Significantly less of a problem on Mars, but you’d still want coverglass.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/13/2023 11:44 pm
That's... 0,00052 W/kg/day.  Not 1.151 W/kg/day...

...probably some kind of conversion mistake...

The engineer didn't hand you the pump coefficient formula because you didn't ask.  Who's more likely to have a "conversion mistake"?

And remember:  You two still have a huge unexplained power discrepancy relative to ISS reality.  Not Meyer.
I have managed to contact m. Meyer's.  He was aware of the problem and was in the process of updating his paper.  He has already changed his pumping values to Twark's.  I suggested he look also into Twark's calculations about compressed gasses, as there was still a significant possible impact there.

So it seems this discussion will have been fruitful.  For the moment scenario 1A has a value of about 3 kW, rather than 10.  So the fit with the ISS is no longer applicable.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/14/2023 12:36 am
That's... 0,00052 W/kg/day.  Not 1.151 W/kg/day...

...probably some kind of conversion mistake...

The engineer didn't hand you the pump coefficient formula because you didn't ask.  Who's more likely to have a "conversion mistake"?

I never do my own unit conversions. Too risky! I use a unit conversion tool.

I link to the calculations in my original post (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2455596#msg2455596), but they are:

High Pressure / Aerator Gas (specs from here (https://www.amazon.com/Blue-Diamond-ET100-Plus-Additional/dp/B08XH6XMF3)):
https://futureboy.us/fsp/frink.fsp?fromVal=80+watt+%2F+%283.54+ft%5E3%2Fmin+1.225+kg%2Fm%5E3%29&toVal=watt%2F%28kg%2Fday%29

Low Pressure Gas (specs from here (https://marinepartssource.com/4-inch-250-cfm-flexmount-blower-24v-jabsco-35440-0010)): https://futureboy.us/fsp/frink.fsp?fromVal=5.3+A+24+V+%2F+%28250+cfm+1.225+kg%2Fm%5E3%29&toVal=watt%2F%28kg%2Fday%29

Fan / High Volume Gas (specs from here (https://www.amazon.com/Schaefer-SCHAEFER-VERSAKOOL-PARENT/dp/B09RQLTL13)): https://futureboy.us/fsp/frink.fsp?fromVal=0.6+A+115+V+%2F+%28450+cfm+1.225+kg%2Fm%5E3%29&toVal=watt%2F%28kg%2Fday%29

Liquids With or Without Solids (specs from here (https://www.supplyhouse.com/Little-Giant-514420-14S-CIM-1-2-HP-100-GPM-Manual-Submersible-Sewage-Ejector-Pump-20ft-power-cord-3-Discharge-9457000-p)): https://futureboy.us/fsp/frink.fsp?fromVal=1100+W+%2F+%28133+gpm+1+kg%2Fl%29&toVal=W%2F%28kg%2Fday%29

I didn't choose the product models myself, those are the "reference" models given in the paper.

And remember:  You two still have a huge unexplained power discrepancy relative to ISS reality.  Not Meyer.

Explained (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457758#msg2457758). You misconstrued me as making a much stronger statement than I actually was.

The ISS uses a totally different life support technology. Any overlap in specs is purely coincidental.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/14/2023 12:44 am
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/ (https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/)
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
That makes 100% perfect engineering sense but zero long term survival sense. There is no ISRU that is less expensive than imported early in the game except maybe propellant - and that's at least a little bit open for discussion.


This is where the balkanization of discussions works against us. The question is as much about economics and politics as it is about engineering. Power is so very central to every aspect of martian settlement that it is not in Mars' long term interest to not have a PV capability at some point.


How soon is the question. Sooner is probably better than later - especially if the technology fits in well.





Title: Re: Power options for a Mars settlement
Post by: LMT on 02/14/2023 04:18 am
You misconstrued me as making a much stronger statement than I actually was.

No, you just didn't realize that your 1.44 kW number was unphysical (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2457241#msg2457241), and couldn't be right.

You might try again with Lamontagne.

Quote from: Twark_Main
I'll just do the first and last scenario, and leave the others as exercises for the reader (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2455612#msg2455612).
Title: Re: Power options for a Mars settlement
Post by: meekGee on 02/14/2023 05:41 am
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/ (https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/)
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
That makes 100% perfect engineering sense but zero long term survival sense. There is no ISRU that is less expensive than imported early in the game except maybe propellant - and that's at least a little bit open for discussion.


This is where the balkanization of discussions works against us. The question is as much about economics and politics as it is about engineering. Power is so very central to every aspect of martian settlement that it is not in Mars' long term interest to not have a PV capability at some point.


How soon is the question. Sooner is probably better than later - especially if the technology fits in well.
The problem is not cost but energy-cost.

Basically, how many years the cell has to operate in order to pay back the energy invested in making it.

Since the energy investment is upfront, any number larger than a couple of years severely limits the practicality of the process.

Terrestrial cells have a short payback period because the fabs are huge and the processes super-optimized.

Small batch Si production won't be, and that's a problem, leading back to the idea of making the panelizing and mounting hardware in-situ (large mass savings, low energy cost) and shipping thin cells from Earth.

Title: Re: Power options for a Mars settlement
Post by: LMT on 02/14/2023 02:27 pm
I have managed to contact m. Meyer's... 

You dismissed the PM caution, but it's common sense:  you don't post unsourced numbers, second-hand.  The author didn't ask you to start a rumor.

Edit/Lar: Post lacks collegiality. As do the last half dozen.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/14/2023 03:52 pm

The problem is not cost but energy-cost.

Basically, how many years the cell has to operate in order to pay back the energy invested in making it.

Since the energy investment is upfront, any number larger than a couple of years severely limits the practicality of the process.

Terrestrial cells have a short payback period because the fabs are huge and the processes super-optimized.

Small batch Si production won't be, and that's a problem, leading back to the idea of making the panelizing and mounting hardware in-situ (large mass savings, low energy cost) and shipping thin cells from Earth.

I came up with two years a while ago.  Would be nice to be fact checked on this.  The energy used on Mars may be different, I guess we will know more once Blue publishes a bit more information on the process.  If ever.

https://marspedia.org/Embodied_energy#Embodied_energy_in_solar_cells
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 02/14/2023 04:07 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/ (https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/)
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
That makes 100% perfect engineering sense but zero long term survival sense. There is no ISRU that is less expensive than imported early in the game except maybe propellant - and that's at least a little bit open for discussion.


This is where the balkanization of discussions works against us. The question is as much about economics and politics as it is about engineering. Power is so very central to every aspect of martian settlement that it is not in Mars' long term interest to not have a PV capability at some point.


How soon is the question. Sooner is probably better than later - especially if the technology fits in well.
The problem is not cost but energy-cost.

Basically, how many years the cell has to operate in order to pay back the energy invested in making it.

Since the energy investment is upfront, any number larger than a couple of years severely limits the practicality of the process.

Terrestrial cells have a short payback period because the fabs are huge and the processes super-optimized.

Small batch Si production won't be, and that's a problem, leading back to the idea of making the panelizing and mounting hardware in-situ (large mass savings, low energy cost) and shipping thin cells from Earth.
Nevertheless, it’s good that they’re working on it anyway. They’re also working on making the glass.

It all needs to operate on an enormous scale to beat just sending it from Earth, but this is a good start.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/14/2023 04:45 pm
Regarding the Blue Origin announcement of a method and a technology to produce solar cells on the Moon, might a similar method be applied to Mars?  Or are there fundamental differences in the regolith composition?

https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/ (https://www.blueorigin.com/news/blue-alchemist-powers-our-lunar-future/)
It can be done. In both cases, the material regolith needs purification before it can be used for solar cells. Mars has more iron which would need to be removed, but this is a known process.

(Anyway, while I love the Blue Origin project and think it usefully advanced the state of the art… the actual weight saved by making solar cells in situ vs on Earth are minuscule if you have a functional, fully reusable launch system. Making glass and metal frames is much more useful. I doubt this process will be competitive with Earth-made solar cells, which are cheaper than you think they are, like 10¢/Watt. Cents, not dollars. And the cells themselves might be 500-1000W/kg.)
That makes 100% perfect engineering sense but zero long term survival sense. There is no ISRU that is less expensive than imported early in the game except maybe propellant - and that's at least a little bit open for discussion.


This is where the balkanization of discussions works against us. The question is as much about economics and politics as it is about engineering. Power is so very central to every aspect of martian settlement that it is not in Mars' long term interest to not have a PV capability at some point.


How soon is the question. Sooner is probably better than later - especially if the technology fits in well.
The problem is not cost but energy-cost.

Basically, how many years the cell has to operate in order to pay back the energy invested in making it.

Since the energy investment is upfront, any number larger than a couple of years severely limits the practicality of the process.

Terrestrial cells have a short payback period because the fabs are huge and the processes super-optimized.

Small batch Si production won't be, and that's a problem, leading back to the idea of making the panelizing and mounting hardware in-situ (large mass savings, low energy cost) and shipping thin cells from Earth.
As usual, the ambiguous time frame raises its ugly head. By the time a base starts morphing into a settlement, a lot of challenges will have been explored. One of these IMO, would be purifying regolith into pure silicone. Not production, exploration in context of local conditions. It's one of those things that seems to be too multi use to pass up.

Building PV frames out of decommissioned hulks will start well before a single production PV cell is made. The only restraint on frames will be labor availability while power is the constraint on PV.

Here's a question for you. After a period of tapping some small percentage of locally produced power, is it unreasonable to expect local cell production to bootstrap off its own product? I bought 2-3 garlic bulbs a few years ago and now produce enough for next years planting, most of my own culinary needs and several freinds antivampire efforts. PV ain't garlic, but there is a parallel.

Yeah, production will not start out power efficient. Give it some time and the ol' iterative process thing will kick in. A few cycles in and the question will be how much product to plow back into expansion vs how much to release for other uses.
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 02/14/2023 05:09 pm
It's not clear that using PV to produce heat is optimal for smelting and silicon refinement. These are both high-temperature, brute-force operations. I think concentrated solar might be a better choice here. PV is probably better when electricity is the desired output, but not for high-temperature processes and possibly not for most heating.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/14/2023 05:27 pm
It's not clear that using PV to produce heat is optimal for smelting and silicon refinement. These are both high-temperature, brute-force operations. I think concentrated solar might be a better choice here. PV is probably better when electricity is the desired output, but not for high-temperature processes and possibly not for most heating.
The referenced articles says they use electrolysis to remove oxygen.  So they will be using quite a bit of electricity.
On the other hand, for glass you want to leave the oxygen in, so perhaps both heat and electricity would be involved.
Solar concentrators are a bit handicapped on Mars, and I don't know of any process that uses them on a large scale. On a very small scale, as others mention, there is little need for the cells anyway.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/17/2023 10:06 pm
It's not clear that using PV to produce heat is optimal for smelting and silicon refinement. These are both high-temperature, brute-force operations. I think concentrated solar might be a better choice here. PV is probably better when electricity is the desired output, but not for high-temperature processes and possibly not for most heating.
An unverified factoid I heard a long time ago: At earths distance from the sun a 100m collector can focus down enough heat to vaporize 10kg of copper per second. At mars distance (a bit variable) and ambient temps, maybe only a couple of kg.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/17/2023 10:10 pm
It's not clear that using PV to produce heat is optimal for smelting and silicon refinement. These are both high-temperature, brute-force operations. I think concentrated solar might be a better choice here. PV is probably better when electricity is the desired output, but not for high-temperature processes and possibly not for most heating.
The referenced articles says they use electrolysis to remove oxygen.  So they will be using quite a bit of electricity.
On the other hand, for glass you want to leave the oxygen in, so perhaps both heat and electricity would be involved.
Solar concentrators are a bit handicapped on Mars, and I don't know of any process that uses them on a large scale. On a very small scale, as others mention, there is little need for the cells anyway.
Not sure how it applies here but in water electrolysis high temps reduce the electrical power needs.
Title: Re: Power options for a Mars settlement
Post by: Slarty1080 on 02/17/2023 10:38 pm
It's not clear that using PV to produce heat is optimal for smelting and silicon refinement. These are both high-temperature, brute-force operations. I think concentrated solar might be a better choice here. PV is probably better when electricity is the desired output, but not for high-temperature processes and possibly not for most heating.
The referenced articles says they use electrolysis to remove oxygen.  So they will be using quite a bit of electricity.
On the other hand, for glass you want to leave the oxygen in, so perhaps both heat and electricity would be involved.
Solar concentrators are a bit handicapped on Mars, and I don't know of any process that uses them on a large scale. On a very small scale, as others mention, there is little need for the cells anyway.
Not sure how it applies here but in water electrolysis high temps reduce the electrical power needs.
It does, but at the cost of additional complexity and the energy needed to heat it in the first place. Although potentially useful there is a limit to how much improvement you can get and saving a few percent or even ten percent is not really going to change things that much. Water electrolysis will use vast amounts of power.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/18/2023 02:15 pm
It's not clear that using PV to produce heat is optimal for smelting and silicon refinement. These are both high-temperature, brute-force operations. I think concentrated solar might be a better choice here. PV is probably better when electricity is the desired output, but not for high-temperature processes and possibly not for most heating.
The referenced articles says they use electrolysis to remove oxygen.  So they will be using quite a bit of electricity.
On the other hand, for glass you want to leave the oxygen in, so perhaps both heat and electricity would be involved.
Solar concentrators are a bit handicapped on Mars, and I don't know of any process that uses them on a large scale. On a very small scale, as others mention, there is little need for the cells anyway.
Not sure how it applies here but in water electrolysis high temps reduce the electrical power needs.
It does, but at the cost of additional complexity and the energy needed to heat it in the first place. Although potentially useful there is a limit to how much improvement you can get and saving a few percent or even ten percent is not really going to change things that much. Water electrolysis will use vast amounts of power.
If you heat steam enough the bonds will break. Zap it hard enough and the bonds break. If you're heating enough to melt regolith it's probably not to far from that breaking point. At this point voltage would be the fine control.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 02/18/2023 04:55 pm


Here's a question for you. After a period of tapping some small percentage of locally produced power, is it unreasonable to expect local cell production to bootstrap off its own product? I bought 2-3 garlic bulbs a few years ago and now produce enough for next years planting, most of my own culinary needs and several freinds antivampire efforts. PV ain't garlic, but there is a parallel.

Yeah, production will not start out power efficient. Give it some time and the ol' iterative process thing will kick in. A few cycles in and the question will be how much product to plow back into expansion vs how much to release for other uses.

Fair question.

Consider a hypothetical food crop (nobody wants to live on garlic).  You need 1000kg a year of the stuff for sustenance.  But if you eat it all, you can't use it to grow new crops. (The age old hungry farmer dilemma)

So you decide to make do while using only 900 kg for sustenance, and put 100 kg back in the ground.

The question is, how many kg of crops will you get?  Clearly, if the 100 kg you used for seed will net you another 1000 kg of food, then you've broken even.

But in small-batch PV production, the numbers are dismal.  You put the entire 1000 kg in the ground, and you only get 1000 kg back in several years.  That's a terrible recovery rate, and it doesn't allow for meaningful growth.

Factor in the limited lifetime of the panels, and you might even be looking at negative returns.

You need to be at a scale that when you invest a kWatt-hr in PV production (instead of other needs) you manufacture enough PV cells to generate that kWatt-hr back within a year max.  Otherwise you're chasing your own tail, since that energy investment is made upfront, and remember that the colony is growing, so that 1 kWatt-hr you burrowed is much more expensive than the 1 kWatt-hr you'll get back in a couple of years.

In all such cases, what you need is a cheap or free loan...  And that's where the thin cells from Earth come in.

Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/18/2023 07:10 pm


Here's a question for you. After a period of tapping some small percentage of locally produced power, is it unreasonable to expect local cell production to bootstrap off its own product? I bought 2-3 garlic bulbs a few years ago and now produce enough for next years planting, most of my own culinary needs and several freinds antivampire efforts. PV ain't garlic, but there is a parallel.

Yeah, production will not start out power efficient. Give it some time and the ol' iterative process thing will kick in. A few cycles in and the question will be how much product to plow back into expansion vs how much to release for other uses.

Fair question.

Consider a hypothetical food crop (nobody wants to live on garlic).  You need 1000kg a year of the stuff for sustenance.  But if you eat it all, you can't use it to grow new crops. (The age old hungry farmer dilemma)

So you decide to make do while using only 900 kg for sustenance, and put 100 kg back in the ground.

The question is, how many kg of crops will you get?  Clearly, if the 100 kg you used for seed will net you another 1000 kg of food, then you've broken even.

But in small-batch PV production, the numbers are dismal.  You put the entire 1000 kg in the ground, and you only get 1000 kg back in several years.  That's a terrible recovery rate, and it doesn't allow for meaningful growth.

Factor in the limited lifetime of the panels, and you might even be looking at negative returns.

You need to be at a scale that when you invest a kWatt-hr in PV production (instead of other needs) you manufacture enough PV cells to generate that kWatt-hr back within a year max.  Otherwise you're chasing your own tail, since that energy investment is made upfront, and remember that the colony is growing, so that 1 kWatt-hr you burrowed is much more expensive than the 1 kWatt-hr you'll get back in a couple of years.

In all such cases, what you need is a cheap or free loan...  And that's where the thin cells from Earth come in.


AKA EROEI (energy return on energy investment)



https://en.wikipedia.org/wiki/Energy_return_on_investment

https://www.nrel.gov/docs/fy17osti/67901.pdf
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 02/18/2023 07:48 pm
Close, but for Mars, if we’re logistically limited we may consider Mass Return On Mass Invested (well… we’re actually trying to optimize for cost, but mass can act as a pretty good correlate in some cases).
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/18/2023 08:59 pm
Yes, EROEI is one component of the analysis. Nobody is saying it's the only component, but it can easily become a limiting factor if you're not careful.

Ditto for mass.

This is why optimizing complex systems is hard. You end up trading off numerous times, so you're left with a system that makes nobody happy on the subsystems level...
Title: Re: Power options for a Mars settlement
Post by: ppnl on 02/18/2023 10:55 pm

I'm surprised nobody has mentioned perovskite solar cells. Not that I've seen in scanning the thread anyway. As I understand it they offer simpler and faster manufacturing methods useing an order of magnitude less energy to make. Forget Mars that's a game changer even here on Earth. It seems reasonably possible for them to go live in a decade or so. It seems more likely than having an active colony on Mars in a decade anyway.
Title: Re: Power options for a Mars settlement
Post by: eriblo on 02/18/2023 11:14 pm

I'm surprised nobody has mentioned perovskite solar cells. Not that I've seen in scanning the thread anyway. As I understand it they offer simpler and faster manufacturing methods useing an order of magnitude less energy to make. Forget Mars that's a game changer even here on Earth. It seems reasonably possible for them to go live in a decade or so. It seems more likely than having an active colony on Mars in a decade anyway.
Hit "print" and search. Perovskite occurs 26 times including your post. First mention is reply #33:
The up and coming new solar cell tech is lead halide perovskite which is cheap and easy to manufacture as an aqueous solution. In just a few years they've already hit 20% with no real end in site. Certainly not viable yet but it will be a few days before they need them on mars. :) One of the big problem right now is degradation due to atmospheric water, probably not much of an issue on mars. Early indications are that they are well suited to space applications with low temperatures and high radiation flux, exhibiting little degradation compares to silicon or gallium cells. If there is Thorium on mars then there is probably lead at too. Now if SpaceX could just find someone in the solar power industry to look into it ... Definitely something to keep and eye on for the future.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 02/19/2023 11:37 pm
Yes, EROEI is one component of the analysis. Nobody is saying it's the only component, but it can easily become a limiting factor if you're not careful.

Ditto for mass.

This is why optimizing complex systems is hard. You end up trading off numerous times, so you're left with a system that makes nobody happy on the subsystems level...
LoL. I think I've seen most of those planes one place or another.


Yup. At some point, at some level, the value of apples and the value oranges has to be compared and judged by what they contribute to a higher order goal.


In the context of high energy cost PV cell production, the setting of higher order goals is a policy/political decision informed by the engineering and economic, but not dictated by them. The evidence for this relationship is a massive corpus of good and bad science fiction.


Ah rest mah case! 8)
Title: Re: Power options for a Mars settlement
Post by: MickQ on 02/24/2023 08:13 pm
I know there are mixed feelings about the viability of wind power but I do wonder if locating turbines in the upper reaches of Noctis Labyrinthus could take advantage of katabatic winds coming down off Tharsis ?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 02/24/2023 08:34 pm
I know there are mixed feelings about the viability of wind power but I do wonder if locating turbines in the upper reaches of Noctis Labyrinthus could take advantage of katabatic winds coming down off Tharsis ?
Maybe, depends on how reliable the winds are.
https://marspedia.org/Wind_turbine

If you find any numbers, I can uipdate the Marspedia article!
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 02/25/2023 07:37 am
Quote
Wind farms on Mars could power future astronaut bases

...

Hartwick and colleagues calculated the amount of power four different wind turbines might generate on Mars. These included commercial-scale machines such as the 300-kilowatt Enercon E3, which possesses a 100-foot-diameter (33-meter) rotor, and the five-kilowatt Aeolos V, which has a 15-foot-diameter (4.5-meter) rotor.

The researchers found that Martian wind power maximized at night, revealing it could help compensate for solar power. Wind power was also strong during global dust storms and during winter seasons in polar and middle latitudes, periods when solar power is weakest. "We were able to identify 13 broad regions with stable wind resources," Hartwick said...

https://www.space.com/mars-wind-power-support-red-planet-missions


Paper (paywall): https://doi.org/10.1038/s41550-022-01851-4

Pre-print: https://www.researchsquare.com/article/rs-1510777/latest.pdf
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/25/2023 08:48 am
Yes, EROEI is one component of the analysis. Nobody is saying it's the only component, but it can easily become a limiting factor if you're not careful.

Ditto for mass.

This is why optimizing complex systems is hard. You end up trading off numerous times, so you're left with a system that makes nobody happy on the subsystems level...
Perhaps what should be the wallpaper for all aircraft companies? I've seen something like on software design that that's excellent. It's been a while since I had an actual lol moment.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/25/2023 09:00 am

I'm surprised nobody has mentioned perovskite solar cells. Not that I've seen in scanning the thread anyway. As I understand it they offer simpler and faster manufacturing methods useing an order of magnitude less energy to make. Forget Mars that's a game changer even here on Earth. It seems reasonably possible for them to go live in a decade or so. It seems more likely than having an active colony on Mars in a decade anyway.
Hit "print" and search. Perovskite occurs 26 times including your post. First mention is reply #33:
The up and coming new solar cell tech is lead halide perovskite which is cheap and easy to manufacture as an aqueous solution. In just a few years they've already hit 20% with no real end in site. Certainly not viable yet but it will be a few days before they need them on mars. :) One of the big problem right now is degradation due to atmospheric water, probably not much of an issue on mars. Early indications are that they are well suited to space applications with low temperatures and high radiation flux, exhibiting little degradation compares to silicon or gallium cells. If there is Thorium on mars then there is probably lead at too. Now if SpaceX could just find someone in the solar power industry to look into it ... Definitely something to keep and eye on for the future.


Hmm so having spent decades trying to lower the level of a  potent neurotoxin (lead) in the environment we should start increasing it again?

The only way this gets worse is if turns out a squirt of mercury really peps up the efficiency.  :(

However...

This does raise the point that what's optimal (or highly cost effective) on earth might work pretty badly on mars.  What you expand a settlement with without input from earth. Silicon solar works great on earth because a)with enough money you can buy all the hardware to make a solar cell plant (going back to raw sand if you want) b)There is a huge power grid available to power it (and melting silicon takes a shedload of power)

None of which exists on mars.

So yes a PV you can make by (hypothetically) dip coating a sheet of glass or plastic in several solutions (ideally at room temperature) could be highly attractive.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 02/25/2023 09:02 am
Close, but for Mars, if we’re logistically limited we may consider Mass Return On Mass Invested (well… we’re actually trying to optimize for cost, but mass can act as a pretty good correlate in some cases).
Careful. In rockets that way lies "Use hydrogen" as a conclusion  :)
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/29/2023 03:55 pm
What Would Battery Manufacturing Look Like on the Moon and Mars? (https://pubs.acs.org/doi/full/10.1021/acsenergylett.2c02743)

Quote
For martian battery manufacturing, NaClO4 undoubtedly appears as the best option due to its immediate availability on the surface.

Notably, a salt harvester extracting perchlorate salts for their liquid electrolyte (NaClO4) could also extract sulfate salts for a traditional saltwater battery electrolyte (e.g., Na2SO4).  Also, NaClO4 can be used in a 5 M saltwater battery (https://iopscience.iop.org/article/10.1149/2.0121506jes).

Previously:  1 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048640#msg2048640) 3 (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1857626#msg1857626)
 
Title: Re: Power options for a Mars settlement
Post by: Craigles on 03/29/2023 04:46 pm
What Would Battery Manufacturing Look Like on the Moon and Mars? (https://pubs.acs.org/doi/full/10.1021/acsenergylett.2c02743)

Quote
For martian battery manufacturing, NaClO4 undoubtedly appears as the best option due to its immediate availability on the surface.

Notably, a salt harvester extracting perchlorate salts for their liquid electrolyte (NaClO4) could also extract sulfate salts for a traditional saltwater battery electrolyte (e.g., Na2SO4).  Also, NaClO4 can be used in a 5 M saltwater battery (https://iopscience.iop.org/article/10.1149/2.0121506jes).

Previously:  1 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048640#msg2048640) 3 (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1857626#msg1857626)
 
To use regolith minerals, in this example for batteries, first you have to find them. Some of these minerals are exotic or complicated to refine, for example on earth. So until a particular operation of In-Situ mineral utilization matures, that operation will look like major prospecting and infrastructure bootstrapping. That is unlike the Figure 1 infographic in the quoted article.

Of course we're discussing Martian Sodium, sulphates, and perchlorates, which might contribute to some kind of battery. But not a spectacular rechargeable battery chemistry like LiPo etc. Change my mind: show me a relevant lab prototype battery.
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/29/2023 04:59 pm
I know there are mixed feelings about the viability of wind power but I do wonder if locating turbines in the upper reaches of Noctis Labyrinthus could take advantage of katabatic winds coming down off Tharsis?

I think that canyon network would reduce wind speed through hydraulic jump / turbulence.  You want fast laminar flow, from long slopes, yes?

To deliver katabatic wind power across thousands of km, why not deploy an equatorial UHVDC PV grid (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2309792#msg2309792) first?  You could add other power sources, like Tharsis wind farms, afterward, as extensions.

With notional cable deployment from areosynchronous orbit, the grid would run across the Tharsis bulge, even across the long slopes of Pavonis Mons.  Conceivably, your wind farm could attach directly, below Pavonis; no grid extension needed.

Do you have estimates of Tharsis diurnal and seasonal winds?

Image:  Pavonis Mons rendering, Wolfgang Wieser
 
Title: Re: Power options for a Mars settlement
Post by: LMT on 03/29/2023 10:18 pm
What Would Battery Manufacturing Look Like on the Moon and Mars? (https://pubs.acs.org/doi/full/10.1021/acsenergylett.2c02743)

Quote
For martian battery manufacturing, NaClO4 undoubtedly appears as the best option due to its immediate availability on the surface.

Notably, a salt harvester extracting perchlorate salts for their liquid electrolyte (NaClO4) could also extract sulfate salts for a traditional saltwater battery electrolyte (e.g., Na2SO4).  Also, NaClO4 can be used in a 5 M saltwater battery (https://iopscience.iop.org/article/10.1149/2.0121506jes).

Previously:  1 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 2 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2048640#msg2048640) 3 (https://forum.nasaspaceflight.com/index.php?topic=45772.msg1857626#msg1857626)
 
To use regolith minerals, in this example for batteries, first you have to find them. Some of these minerals are exotic or complicated to refine, for example on earth. So until a particular operation of In-Situ mineral utilization matures, that operation will look like major prospecting and infrastructure bootstrapping. That is unlike the Figure 1 infographic in the quoted article.

Of course we're discussing Martian Sodium, sulphates, and perchlorates, which might contribute to some kind of battery. But not a spectacular rechargeable battery chemistry like LiPo etc. Change my mind: show me a relevant lab prototype battery.

The noted battery salts aren't exotic.  What are you asking for, exactly?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/08/2023 03:54 pm
If this works for Earth, would it also work for Mars?  I think so, but there have been diverging opinions over the years.
 ;D

Master plan part III

How heavy would a Master plan part III be for Mars?
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/09/2023 12:21 am
If this works for Earth, would it also work for Mars?  I think so, but there have been diverging opinions over the years.
 ;D

Master plan part III

How heavy would a Master plan part III be for Mars?
OMG. You wouldn't have the cliff notes or the classic comic version by any chance?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/12/2023 03:31 am
It's not a "magic bullet" solution you can sum up in one sentence. Solving a huge global energy problem requires complex ideas. No surprise, really.

The most digestible version is probably the Supercut below.

https://www.youtube.com/watch?v=BoGNEZF2XFQ
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/13/2023 01:15 pm
It's not a "magic bullet" solution you can sum up in one sentence. Solving a huge global energy problem requires complex ideas. No surprise, really.

The most digestible version is probably the Supercut below.


The item that impacts Mars design the most is probably the reliance on batteries, that are fine for a few days but not for months.  They do cover hydrogen storage and methane production for industrial processes, that might be used on Mars to cover winter months and dust storms.  Wonder if we could adapt the usage models?
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/13/2023 04:24 pm
The item that impacts Mars design the most is probably the reliance on batteries, that are fine for a few days but not for months.  They do cover hydrogen storage and methane production for industrial processes, that might be used on Mars to cover winter months and dust storms.  Wonder if we could adapt the usage models?

Round-trip efficiency is extremely low there.

ISRU battery farms can run for months, with high efficiency.  E.g., apply the notional ISRU industrial night-shift farm (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) to winter round-the-clock use, and add an ISRU thermal battery farm (https://forum.nasaspaceflight.com/index.php?topic=41427.msg2445518#msg2445518) to utilize waste heat concurrently. 
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/13/2023 04:40 pm
You oversize the solar so it still performs in winter, then you use ISRU fuel and oxidizer to cover the last 5% of annual electricity usage. Depending on power usage, even just pausing ISRU propellant usage could be enough to get through the sand storms.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/13/2023 04:58 pm
...use ISRU fuel and oxidizer to cover the last 5% of annual electricity usage.

You might calculate for a realistic industrial scenario, e.g., at fleet scale.

Winter daily insolation might be 10% of summer max, even less under winter storms.  How to maintain winter industry in the worst case?
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/13/2023 05:11 pm
You oversize the solar so it still performs in winter, then you use ISRU fuel and oxidizer to cover the last 5% of annual electricity usage. Depending on power usage, even just pausing ISRU propellant usage could be enough to get through the sand storms.
I've always though so, but it would be nice to actually model it.
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 04/13/2023 05:31 pm
You oversize the solar so it still performs in winter, then you use ISRU fuel and oxidizer to cover the last 5% of annual electricity usage. Depending on power usage, even just pausing ISRU propellant usage could be enough to get through the sand storms.
I've always though so, but it would be nice to actually model it.
Basically, your ISRU propellant, oxidizer, and generator becomes your second-level "battery". Its round-trip efficiency is lower than your first-level battery, but the storage capacity is very large. When you have excess PV, you star by filling your first-level batteries, and then use the remainder to generate propellant and oxidizer. Details will depend on the exact parameters of your first-level batteries and second-level "battery" and on your ability to predict insolation for the next week (varies with dust storms). A similar system could be used on Earth, except that utility-scale use of methane historically results in methane leaks.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/13/2023 05:47 pm
A similar system could be used on Earth, except that utility-scale use of methane historically results in methane leaks.
IIRC the industry estimates a typical 3% leakage of Methane, a GH gas 27-30x more potent than CO2.

Sitting behind every "renewable" scheme that isn't backed up by nuclear ready to come on when the sun don't shine, the wind don't blow and the dams empty.  :(
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/13/2023 05:56 pm
An interesting question would be what would an indigenous nuclear power system on Mars look like?

That's one where nearly everything is Made on Mars(TM).  :)

Keep in mind
1) Power is likely expensive
2) Water is likely very expensive
3) CO2 is available outside your front door (or rather the airlock to your burrow)
4) As there are no seas on mars a fuel form that's stable in seawater IE UO2 is irrelevant. It is also energy intensive to make and has both poor thermal conductivity and a lower percentage of Uranium per unit mass than other options.

Now you can call on the earth for knowledge and simulations but you're going to have to make it on mars, or find a way to raise the cash to buy (and ship) any parts you need.

I'm interested to see how that would change peoples approach.

Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/13/2023 06:20 pm
An interesting question would be what would an indigenous nuclear power system on Mars look like?

That's one where nearly everything is Made on Mars(TM).  :)

Keep in mind
1) Power is likely expensive
2) Water is likely very expensive
3) CO2 is available outside your front door (or rather the airlock to your burrow)
4) As there are no seas on mars a fuel form that's stable in seawater IE UO2 is irrelevant. It is also energy intensive to make and has both poor thermal conductivity and a lower percentage of Uranium per unit mass than other options.

Now you can call on the earth for knowledge and simulations but you're going to have to make it on mars, or find a way to raise the cash to buy (and ship) any parts you need.

I'm interested to see how that would change peoples approach.
Fuel is the lightest part of a nuclear reactor.  Most likely it would come from Earth?  Are there uranium rich minerals on Mars? We need boots on the ground to know that.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/13/2023 06:27 pm
I've done some work here (with others) on the cost of nuclear vs solar, but I had handwaved in energy storage, and I would like to go a bit further, and at the same time review this!

https://marspedia.org/Cost_of_energy_on_Mars
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/13/2023 09:24 pm

Fuel is the lightest part of a nuclear reactor.  Most likely it would come from Earth?  Are there uranium rich minerals on Mars? We need boots on the ground to know that.
Well a full reload of a PWR is about 81tonnes.

But that kind of misses the point.

For sustainable development on mars you need to extract and process on mars. So if you want to (say) double capacity you only have to worry about martian resources.

I'd suggest the starting issue is enrichment.

 There's no way that technology will be transferred off earth.

OTOH all of the first generation power reactors in Russia and Europe were fueled with natural uranium. CANDU still has it as an option.

The USN wanted high power density with long lifetime  and were happy to use high neutron absorbing materials to get it, offsetting that with high enrichement (because they could).  Another irrelevant requirement earth based PWR's inherited that can be completely ignored on mars.

If you chose to ditch UO2 the 2nd most researched approach is metal alloys. About 13x the thermal conductivity and castable at 1300c, not the 17-1800c that UO2 needs to be sintered at (in 100% H2 or Ar/4%H2 at best). EBR II also demonstated recycling and refabrication by remote control for years at ORNL.

Metal fuels Achilles Heel is swelling (about 10%) but a lot of work was done on low swelling alloys for sodium cooled FBRs in the 60's and 70's. IIRC quite a lot of progress was made. Whereas UO2 is 1/3 U atoms metallic fuel would be more like 80-90% U atoms. The metal "popcorned" into a foam, but the alloying elements made it weak enough that it could not excert substantial force on the cladding. So no harm done.

In principle melting into a tall, thin(ish) crucible would seperate the various TRU's and FP's based on density (although it turn out despite higher numbers of neutrons in the nucleaus TRU's are often less dense than either U or Pu, so they'd solidify above the U and PU layers, but still below any of the plausible FP's, with their much lower densities
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 04/13/2023 09:48 pm
A similar system could be used on Earth, except that utility-scale use of methane historically results in methane leaks.
IIRC the industry estimates a typical 3% leakage of Methane, a GH gas 27-30x more potent than CO2.

Sitting behind every "renewable" scheme that isn't backed up by nuclear ready to come on when the sun don't shine, the wind don't blow and the dams empty.  :(
3% is high, maybe accurate for a case with zero mitigation.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/13/2023 11:08 pm
I've done some work here (with others) on the cost of nuclear vs solar, but I had handwaved in energy storage, and I would like to go a bit further, and at the same time review this!

https://marspedia.org/Cost_of_energy_on_Mars

Quote from: lamontagne
Cost on Earth:  $800/m2

Bulk-print panels might cost 100x less per square meter.  For example, Paul Dastoor (https://www.reuters.com/business/autos-transportation/australian-scientists-power-tesla-15000-km-trip-with-printed-solar-panels-2022-04-20/) prints half a km at a time, at ~ 100 g/m2, ballparking commercial cost at $8/m2.  His current, short-lived substrate must be upgraded, but PEN might serve.

Also, your nuclear pricing isn't plausible.  NASA has guessed more than its $20 million Krusty demo cost (https://www.sandiegouniontribune.com/business/energy-green/sd-fi-nasa-nuclear-20180523-story.html) to get a Kilopower successor to the Moon, delivering 40 kWe.  (See Phase 1 (https://www.nasa.gov/press-release/nasa-announces-artemis-concept-awards-for-nuclear-power-on-moon) awards.)  You claim $37.5 million to deliver MINERAL's 2 MWe, oddly.  MINERAL is no simpler than Kilopower.  And unlike Kilopower (https://www.tandfonline.com/doi/full/10.1080/00295450.2020.1725382), MINERAL is a grad-school model (https://www.tandfonline.com/doi/full/10.1080/00295450.2022.2072649), on paper.  $37.5 million might cover a lab demo.


https://www.youtube.com/watch?v=eVz2F1Hn65I
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/13/2023 11:55 pm
...use ISRU fuel and oxidizer to cover the last 5% of annual electricity usage.

You might calculate for a realistic industrial scenario, e.g., at fleet scale.

Winter daily insolation might be 10% of summer max, even less under winter storms.  How to maintain winter industry in the worst case?
Size the solar to supply 100% of immediate survival needs under worst case conditions. Budget solar power greater than this to support a relatively low level of other activities with surplus power going to storage in one form or another. This keeps everybody and all programs working at a steady rate all year while establishing a robust storage buffer for that unexpected 90 sol dust storm.


If things go sideways somehow, chances are good that extra power will help. That's when it's time to reassess the non survival power budget and redirect as appropriate.


At some point there will be parties other than NASA, academia and SX. They will always have the option of designing, shipping and installing their own power subgrid to meet their own quirky power needs.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/14/2023 05:23 am
A similar system could be used on Earth, except that utility-scale use of methane historically results in methane leaks.
IIRC the industry estimates a typical 3% leakage of Methane, a GH gas 27-30x more potent than CO2.

Sitting behind every "renewable" scheme that isn't backed up by nuclear ready to come on when the sun don't shine, the wind don't blow and the dams empty.  :(
3% is high, maybe accurate for a case with zero mitigation.
Also not a problem on mars, where a bit more global warming would be a good thing.

OTOH on mars you are going to have to make all the methane to begin with, and people get a lot more careful when a resouce no longer just comes out the ground.  :(
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/14/2023 09:27 am
You oversize the solar so it still performs in winter, then you use ISRU fuel and oxidizer to cover the last 5% of annual electricity usage.

Not just that, but displacing energy use with stored consumables.

You're not going to burn methane and oxygen to generate electricity to run the oxygen generator. That's Rube Goldberg. You're just going to store more liquid oxygen.  :)
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/14/2023 09:31 am
A similar system could be used on Earth, except that utility-scale use of methane historically results in methane leaks.
IIRC the industry estimates a typical 3% leakage of Methane, a GH gas 27-30x more potent than CO2.


Note that this estimate is probably low. https://news.stanford.edu/2022/03/24/methane-leaks-much-worse-estimates-fix-available/

Also 30x is the equivalence factor over a 100 year time horizon. If you're talking 20 years (eg for near-term feedback loops) the equivalence factor rises to 84-86 times.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/14/2023 05:47 pm
I've done some work here (with others) on the cost of nuclear vs solar, but I had handwaved in energy storage, and I would like to go a bit further, and at the same time review this!

https://marspedia.org/Cost_of_energy_on_Mars

Quote from: lamontagne
Cost on Earth:  $800/m2

Bulk-print panels might cost 100x less per square meter.  For example, Paul Dastoor (https://www.reuters.com/business/autos-transportation/australian-scientists-power-tesla-15000-km-trip-with-printed-solar-panels-2022-04-20/) prints half a km at a time, at ~ 100 g/m2, ballparking commercial cost at $8/m2.  His current, short-lived substrate must be upgraded, but PEN might serve.

Also, your nuclear pricing isn't plausible.  NASA has guessed more than its $20 million Krusty demo cost (https://www.sandiegouniontribune.com/business/energy-green/sd-fi-nasa-nuclear-20180523-story.html) to get a Kilopower successor to the Moon, delivering 40 kWe.  (See Phase 1 (https://www.nasa.gov/press-release/nasa-announces-artemis-concept-awards-for-nuclear-power-on-moon) awards.)  You claim $37.5 million to deliver MINERAL's 2 MWe, oddly.  MINERAL is no simpler than Kilopower.  And unlike Kilopower (https://www.tandfonline.com/doi/full/10.1080/00295450.2020.1725382), MINERAL is a grad-school model (https://www.tandfonline.com/doi/full/10.1080/00295450.2022.2072649), on paper.  $37.5 million might cover a lab demo.



Really interesting!  If I read the article correctly, the efficiency at this point is between 1 and 2 %  so 10 to 20 times less efficient than other technologies, but very cheap.  And they might last longer on Mars than on Earth, but on Earth they just last 1-2 years.  At 8$/m2 x 30 then it's about 240$ to equal 1 m2 of conventional panels.  To equal a tracking array for power per year you get, perhaps, 300$/m2.  So it would not be that much of a stretch to divide solar power cost by two, perhaps even 3.
For nuclear, I think it will all depend on who pays the bill for development. If the cost goes to the project, then nuclear power will be more expensive and then solar might win out over nuclear.  It's a pretty close race, and perhaps rather than fixed values I should use a fairly large spread.  These would probably overlap.  Kilopower is a non starter, IMHO,  but an eventual Megapower might squeak by.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/14/2023 05:48 pm
And if these solar paint cells grow in efficiency like other solar systems have grown over time, they might be much more competitive in the future.
Title: Re: Power options for a Mars settlement
Post by: LMT on 04/14/2023 06:58 pm
I've done some work here (with others) on the cost of nuclear vs solar, but I had handwaved in energy storage, and I would like to go a bit further, and at the same time review this!

https://marspedia.org/Cost_of_energy_on_Mars

Quote from: lamontagne
Cost on Earth:  $800/m2

Bulk-print panels might cost 100x less per square meter.  For example, Paul Dastoor (https://www.reuters.com/business/autos-transportation/australian-scientists-power-tesla-15000-km-trip-with-printed-solar-panels-2022-04-20/) prints half a km at a time, at ~ 100 g/m2, ballparking commercial cost at $8/m2.  His current, short-lived substrate must be upgraded, but PEN might serve.

Also, your nuclear pricing isn't plausible.  NASA has guessed more than its $20 million Krusty demo cost (https://www.sandiegouniontribune.com/business/energy-green/sd-fi-nasa-nuclear-20180523-story.html) to get a Kilopower successor to the Moon, delivering 40 kWe.  (See Phase 1 (https://www.nasa.gov/press-release/nasa-announces-artemis-concept-awards-for-nuclear-power-on-moon) awards.)  You claim $37.5 million to deliver MINERAL's 2 MWe, oddly.  MINERAL is no simpler than Kilopower.  And unlike Kilopower (https://www.tandfonline.com/doi/full/10.1080/00295450.2020.1725382), MINERAL is a grad-school model (https://www.tandfonline.com/doi/full/10.1080/00295450.2022.2072649), on paper.  $37.5 million might cover a lab demo.

...efficiency at this point is between 1 and 2 %...

It was one $ example.  Your article isn't ready until you dig for plausible numbers.

Benyon et al. 2023:  10.8% conversion efficiency (https://onlinelibrary.wiley.com/doi/10.1002/adma.202208561), roll-to-roll printed PV.

Refs.

Beynon, D., Parvazian, E., Hooper, K., Mcgettrick, J., Patidar, R., Dunlop, T., Wei, Z., Davies, P., Rodriguez, R.G., Carnie, M. and Davies, M., 2023. All‐Printed Roll to Roll Perovskite Photovoltaics Enabled by Solution Processed Carbon Electrode. (https://onlinelibrary.wiley.com/doi/10.1002/adma.202208561) Advanced Materials, p.2208561.
 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/14/2023 07:37 pm
I've done some work here (with others) on the cost of nuclear vs solar, but I had handwaved in energy storage, and I would like to go a bit further, and at the same time review this!

https://marspedia.org/Cost_of_energy_on_Mars

Quote from: lamontagne
Cost on Earth:  $800/m2

Bulk-print panels might cost 100x less per square meter.  For example, Paul Dastoor (https://www.reuters.com/business/autos-transportation/australian-scientists-power-tesla-15000-km-trip-with-printed-solar-panels-2022-04-20/) prints half a km at a time, at ~ 100 g/m2, ballparking commercial cost at $8/m2.  His current, short-lived substrate must be upgraded, but PEN might serve.

Also, your nuclear pricing isn't plausible.  NASA has guessed more than its $20 million Krusty demo cost (https://www.sandiegouniontribune.com/business/energy-green/sd-fi-nasa-nuclear-20180523-story.html) to get a Kilopower successor to the Moon, delivering 40 kWe.  (See Phase 1 (https://www.nasa.gov/press-release/nasa-announces-artemis-concept-awards-for-nuclear-power-on-moon) awards.)  You claim $37.5 million to deliver MINERAL's 2 MWe, oddly.  MINERAL is no simpler than Kilopower.  And unlike Kilopower (https://www.tandfonline.com/doi/full/10.1080/00295450.2020.1725382), MINERAL is a grad-school model (https://www.tandfonline.com/doi/full/10.1080/00295450.2022.2072649), on paper.  $37.5 million might cover a lab demo.

...efficiency at this point is between 1 and 2 %...

It was one $ example.  Your article isn't ready until you dig for plausible numbers.

Benyon et al. 2023:  10.8% conversion efficiency (https://onlinelibrary.wiley.com/doi/10.1002/adma.202208561), roll-to-roll printed PV.

Refs.

Beynon, D., Parvazian, E., Hooper, K., Mcgettrick, J., Patidar, R., Dunlop, T., Wei, Z., Davies, P., Rodriguez, R.G., Carnie, M. and Davies, M., 2023. All‐Printed Roll to Roll Perovskite Photovoltaics Enabled by Solution Processed Carbon Electrode. (https://onlinelibrary.wiley.com/doi/10.1002/adma.202208561) Advanced Materials, p.2208561.
When I fist did the text, solar won because the nuclear side was Kilopower.
Then someone proposed the larger reactor described in the text, and the situation changed.  Nuclear got competitive again.
The article was written before these cells came along.  Of course, the situation evolves.  Perhaps China will provide a cheap nuclear reactor next year and then everything needs to be calculated again.  The 500$/m2 is perfectly reasonable for a low mass system of conventional cells at 30% efficiency.  a bit optimistic, even.
I fully expect solar to outperform nuclear.  It's just that at the time I wrote this it wasn't the case, when compared to an advanced nuclear reactor that was subsidized in development.
So I guess I may update this, but the main point of the article was to determine a cost for electricity on Mars, and I still think I'm not too far off at this point.
Using the energy cost, it's possible to calculated embodied energy costs, and then all that is left is to determine labor costs and you can cost constructions on Mars.  Seems like a interesting tool to me.

It's a Wiki, if you want to participate, just contact the Mars Society!




Title: Re: Power options for a Mars settlement
Post by: LMT on 04/14/2023 07:51 pm
...the main point of the article was to determine a cost for electricity on Mars, and I still think I'm not too far off at this point.

...if you want to participate, just contact the Mars Society!

No, at this point your nuclear / PV energy cost comparison is off by perhaps three orders of magnitude.

The Mars Society contributed to your article? 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/14/2023 08:03 pm
...the main point of the article was to determine a cost for electricity on Mars, and I still think I'm not too far off at this point.

...if you want to participate, just contact the Mars Society!

No, at this point your nuclear / PV energy cost comparison is off by perhaps three orders of magnitude.

The Mars Society contributed to your article?
The wiki, Marspedia, is hosted by the Mars Society.  It's open to all that want to register.  Three orders of magnitude is a lot! 1000 times more expensive?  Because 1000 times less expensive is getting a bit too cheap. 
The Mars society does not endorse the content.  Readers are supposed to comment and improve articles, like any other Wiki.  Very few active writers, however.

Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/15/2023 09:13 am
Note that this estimate is probably low. https://news.stanford.edu/2022/03/24/methane-leaks-much-worse-estimates-fix-available/
My skim of the article suggests the actual figure is about 9% IE 3x the industry estimate.

This raises 2 interesting (but OT) questions
1) How typical is the loss pattern in this area versus other gas producing areas of the US and elsewhere
2) If the industry has underestimated its own losses does this mean that it has received a loud enoug wakeup call to do something about it, IOW is there enough money leaking into the air that it decides "We should start doing something about this"?

Or will it take actual EPA fines for them to start doing something about this?  :(

Also 30x is the equivalence factor over a 100 year time horizon. If you're talking 20 years (eg for near-term feedback loops) the equivalence factor rises to 84-86 times.
Well I'm using the IPCC reports, which talk 100 year time scales.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/15/2023 09:26 am
1) How typical is the loss pattern in this area versus other gas producing areas of the US and elsewhere

We'll know after MethaneSAT launches in 2024.

Also 30x is the equivalence factor over a 100 year time horizon. If you're talking 20 years (eg for near-term feedback loops) the equivalence factor rises to 84-86 times.
Well I'm using the IPCC reports, which talk 100 year time scales.

Name drop! :)

It's not like any particular time horizon is "correct," it's more about understanding what the equivalence factor really means and then choosing the most appropriate number for your particular context.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 04/16/2023 08:49 am
We'll know after MethaneSAT launches in 2024.
True. Personally I'd like to think that loosing 9% of your raw material was sufficient incentive to actually do something about the losses, but something tells me even that is not enough.  :(

Name drop! :)

It's not like any particular time horizon is "correct," it's more about understanding what the equivalence factor really means and then choosing the most appropriate number for your particular context.

The question for earth would be are there "threshold" temperatures that trigger worse non linear temperature rises (possible melting of deep ocean clathates?)

However that is also OT for this thread.
It's a good idea to set some kind of level playing field and IPCC uses 100 years.

However that's not much help if you're looking at shorter term feedback loops. In which case things are much worse.  :(
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 04/16/2023 04:08 pm
We'll know after MethaneSAT launches in 2024.
True. Personally I'd like to think that loosing 9% of your raw material was sufficient incentive to actually do something about the losses, but something tells me even that is not enough.  :(

Name drop! :)

It's not like any particular time horizon is "correct," it's more about understanding what the equivalence factor really means and then choosing the most appropriate number for your particular context.

The question for earth would be are there "threshold" temperatures that trigger worse non linear temperature rises (possible melting of deep ocean clathates?)

However that is also OT for this thread.
It's a good idea to set some kind of level playing field and IPCC uses 100 years.

However that's not much help if you're looking at shorter term feedback loops. In which case things are much worse.  :(
Most mining operations lose a significant amount of material that ends up in tailings.  Sometimes, a generation later, new technologies come along and they mine the tailings again!  My guess is that as long as the methane isn't in the pipeline it isn't really counted.  Thinking of Mars, they probably will not require geological formation storage before some time, as the population will remain low for many generations?  So loses may be quite low, in particular if the have refrigerated cooling rather than depending on evaporative cooling.
I grew up in a region called the Saguenay, where there used to be ships that brought fuel up the river once or twice a year, stored it in large tanks, and distributed from there for an isolated region with a population of about 200 000 people.  Until they figured out that evaporative losses (5%, I believe) were eating into their profits and they decided to ship it all by truck straight from the refinery.  Cutting loses, and transferring whatever losses came from the tanks in the gas stations to the gas station owners.  Underground storage losses on Mars should be quite low, at an average temperature of -68C?
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 04/17/2023 10:36 am
It's a good idea to set some kind of level playing field and IPCC uses 100 years.

"Setting a level playing field" is good, but that just means using the same time horizon for each gas in your analysis. It doesn't elevate the IPCC's choice of 100 years over other values.

However that's not much help if you're looking at shorter term feedback loops. In which case things are much worse.  :(

My point exactly.


Anyway I don't think this is a viable method to terraform Mars, even as an incidental benefit. All the proposals I've seen require the use of ultra-stable super greenhouse gases (eg fluorocarbons) which have extremely long atmospheric half-lives.

For (previously mentioned) economic reasons I expect extremely low methane leakage on Mars.
Title: Re: Power options for a Mars settlement
Post by: OTV Booster on 04/18/2023 12:32 am
We'll know after MethaneSAT launches in 2024.
True. Personally I'd like to think that loosing 9% of your raw material was sufficient incentive to actually do something about the losses, but something tells me even that is not enough.  :(

Name drop! :)

It's not like any particular time horizon is "correct," it's more about understanding what the equivalence factor really means and then choosing the most appropriate number for your particular context.

The question for earth would be are there "threshold" temperatures that trigger worse non linear temperature rises (possible melting of deep ocean clathates?)

However that is also OT for this thread.
It's a good idea to set some kind of level playing field and IPCC uses 100 years.

However that's not much help if you're looking at shorter term feedback loops. In which case things are much worse.  :(
Most mining operations lose a significant amount of material that ends up in tailings.  Sometimes, a generation later, new technologies come along and they mine the tailings again!  My guess is that as long as the methane isn't in the pipeline it isn't really counted.  Thinking of Mars, they probably will not require geological formation storage before some time, as the population will remain low for many generations?  So loses may be quite low, in particular if the have refrigerated cooling rather than depending on evaporative cooling.
I grew up in a region called the Saguenay, where there used to be ships that brought fuel up the river once or twice a year, stored it in large tanks, and distributed from there for an isolated region with a population of about 200 000 people.  Until they figured out that evaporative losses (5%, I believe) were eating into their profits and they decided to ship it all by truck straight from the refinery.  Cutting loses, and transferring whatever losses came from the tanks in the gas stations to the gas station owners.  Underground storage losses on Mars should be quite low, at an average temperature of -68C?
Just had a conversation with a friend who worked the oil patch for a long time and asked him where methane leaks happen in the real world.


At the well. The bore hole has a metal liner, the casing. The space between the casing and the hole used to be a methane conduit. These days it's grouted with concrete to form a seal but excrement occurs sometimes.


In transmission from the wellhead to the processing facility. The line usually runs through farm fields and is buried deep enough to avoid the plow but excrement occurs.


In processing. Much of the plant is using threaded pipe. Each joint, even if done correctly, is a potential leak site as the plumbing ages.


End user. No details available.


From personal observation, LNG tankers and any LNG storage without recondensers is going to vent to atmosphere.


Mars will not have any wellhead losses and as you say, local ambient temps will go a long way to mitigate LNG boiloff. No farmers will drag a plow through a pipeline for the next few hundred years although dirt moving for other reasons will still offer risk.


To avoid loss at all the other points, economic self interest will probably go a long way. IMO mars will have a survival oriented ethos of thrift.
Title: Re: Power options for a Mars settlement
Post by: john smith 19 on 05/01/2023 07:33 pm
Mars will not have any wellhead losses and as you say, local ambient temps will go a long way to mitigate LNG boiloff. No farmers will drag a plow through a pipeline for the next few hundred years although dirt moving for other reasons will still offer risk.


To avoid loss at all the other points, economic self interest will probably go a long way. IMO mars will have a survival oriented ethos of thrift.
That would be my assumption.

IMHO there will be no "waste" on mars. Just stuff-we-haven't-reused-yet for a very long time to come.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/02/2023 02:51 pm
...the main point of the article was to determine a cost for electricity on Mars, and I still think I'm not too far off at this point.

No, at this point your nuclear / PV energy cost comparison is off by perhaps three orders of magnitude.

The Mars Society contributed to your article?

Readers are supposed to comment and improve articles...

Authors are responsible.

The KRUSTY reactor was built at ~ $150,000 / kg, as a lab demo.  Your $200 / kg number for a Mars-rated MINERAL reactor is not an estimate; just special pleading for federal subsidy.  That's nonsensical in a cost comparison.

You've updated, but haven't fixed, your Marspedia article (https://marspedia.org/Cost_of_energy_on_Mars).  Three orders of magnitude is, still, a huge miss. 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/02/2023 02:58 pm
...the main point of the article was to determine a cost for electricity on Mars, and I still think I'm not too far off at this point.

No, at this point your nuclear / PV energy cost comparison is off by perhaps three orders of magnitude.

The Mars Society contributed to your article?

Readers are supposed to comment and improve articles...

Authors are responsible.

The KRUSTY reactor was built at ~ $150,000 / kg, as a lab demo.  Your $200 / kg number for a Mars-rated MINERAL reactor is not an estimate; just special pleading for federal subsidy.  That's nonsensical in a cost comparison.

You've updated, but haven't fixed, your Marspedia article (https://marspedia.org/Cost_of_energy_on_Mars).  Three orders of magnitude is, still, a huge miss.
It would be appreciated if your were more explicit. I can't even understand if you think the numbers are too high or too low.  I can't fix without a diagnostic, and as far as I know I'm more or less on point.

200$ / kg is a reasonable fabrication number, I believe, but not a program development number.   If you have better reference (you usually do!) I would love to see them.

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/02/2023 09:07 pm
$200/kg is incredibly optimistic for space hardware fabrication. $10,000/kg is more likely even after development. Airplanes and launch vehicles, after development is paid for, have fab costs of about $1000/kg. The only folks I know who could do $200/kg is SpaceX and their Starlink production plant. They use commodity solar cells and modified COTS solar panel stringing equipment. There is no equivalent for nuclear power.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/02/2023 09:23 pm
$200/kg is incredibly optimistic for space hardware fabrication. $10,000/kg is more likely even after development. Airplanes and launch vehicles, after development is paid for, have fab costs of about $1000/kg. The only folks I know who could do $200/kg is SpaceX and their Starlink production plant. They use commodity solar cells and modified COTS solar panel stringing equipment. There is no equivalent for nuclear power.
I was presuming routine fabrication of a large number of small nuclear reactors, because that's the only way I see this happening at the require scale. Plus a large part of the mass is likely to be the heat exchanger, that will not be all that expensive to build.  It's not really space hardware fabrication.  But I'll be glad to adjust! 

If so should I also increase the solar power costs?  Or for that case are we talking volume manufacturing and therefore very low costs like Starlink?
It's hard to be fair.  I actually has solar wining at first, but really Kilopower couldn't compete on any front.  A mid sized nuclear reactor build in thousands of units might be more competitive.  There are many Earth side use cases if we decide to go that route. And the Mars Society is a child of Zubrin's, so nuclear has many advocates there!  It's a tough sell!

Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/03/2023 03:31 pm
Kilopower is made with ASRGs, which are more expensive than solar cells even WITHOUT a reactor.

I personally think nuclear power won't compete with solar unless you're dumping heat into the atmosphere, i.e. with a forced air heat exchanger, and with much higher power levels. Kilopower is just way too niche to compete. Even the fuel cost itself might be a problem as kilopower and others use HEU or HALEU, which costs significantly more power MWh-thermal, and they typically operate at lower efficiency than commercial plants (~20-25% vs ~30-35%), and they typically have much lower burn-up than commercial plants. You need kind of a completely different design, which is heavier and therefore much less competitive in the early days, to achieve good economics.

Even with modern "small" (100MWe) modular reactor designs on Earth designed for high burn-up, they still use HALEU and their fuel costs alone are as high as the LCOE of solar power.

I think early Mars efforts might use some auxilliary nuclear power in cooperation with NASA (NASA has many other uses for nuclear power, including as a supplement/replacement for RTGs for outer planets missions), but 99% of electricity will be produced using solar. Once a Mars settlement gets large and gets some domestic manufacturing capacity for heat exchangers, etc, plus a logistics system and demand for gigawatts of electricity, I think nuclear might become viable again as you can use more cost-optimized fuel cycles, maybe use nuclear heat for process heat applications (melting water, etc) which can do dual-purpose for heat rejection. But overall, I think solar will dominate unless some sort of regulatory arbitrage is possible, where nuclear power becomes much easier regulatorily to do on Mars than it is on Earth (as opposed to the opposite, like right now).
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/03/2023 04:09 pm
Kilopower is made with ASRGs, which are more expensive than solar cells even WITHOUT a reactor.

I personally think nuclear power won't compete with solar unless you're dumping heat into the atmosphere, i.e. with a forced air heat exchanger, and with much higher power levels. Kilopower is just way too niche to compete. Even the fuel cost itself might be a problem as kilopower and others use HEU or HALEU, which costs significantly more power MWh-thermal, and they typically operate at lower efficiency than commercial plants (~20-25% vs ~30-35%), and they typically have much lower burn-up than commercial plants. You need kind of a completely different design, which is heavier and therefore much less competitive in the early days, to achieve good economics.

Even with modern "small" (100MWe) modular reactor designs on Earth designed for high burn-up, they still use HALEU and their fuel costs alone are as high as the LCOE of solar power.

I think early Mars efforts might use some auxilliary nuclear power in cooperation with NASA (NASA has many other uses for nuclear power, including as a supplement/replacement for RTGs for outer planets missions), but 99% of electricity will be produced using solar. Once a Mars settlement gets large and gets some domestic manufacturing capacity for heat exchangers, etc, plus a logistics system and demand for gigawatts of electricity, I think nuclear might become viable again as you can use more cost-optimized fuel cycles, maybe use nuclear heat for process heat applications (melting water, etc) which can do dual-purpose for heat rejection. But overall, I think solar will dominate unless some sort of regulatory arbitrage is possible, where nuclear power becomes much easier regulatorily to do on Mars than it is on Earth (as opposed to the opposite, like right now).
I tend to agree and usually just plan for solar.  However, if large scale nuclear happens on Earth, then it will be competitive and possibly advantageous on Mars.  I don't see large scale nuclear happening on Earth anymore, but I certainly see plenty of lobbying for it still.
The Marspedia article is written in the spirit of the Mars Society colony contests.  One was for one thousand and the other for one million people on Mars.
I think that just food production on Mars will produce so much waste heat that cooling a Martian settlement will be the main issue, not heating it.  So I don't see much for use case for nuclear reactor waste heat.

I would be completely wrong on this if efficient solar greenhouses using entirely natural sunlight were possible at scale.  I have serious doubts.
Title: Re: Power options for a Mars settlement
Post by: CuddlyRocket on 05/03/2023 10:21 pm
I personally think nuclear power won't compete with solar unless you're dumping heat into the atmosphere, i.e. with a forced air heat exchanger, and with much higher power levels. Kilopower is just way too niche to compete.

I think there'll be some nuclear power for the comfort it provides for power security as it adds an independent source of supply.

I agree that solar (with storage for overnight) will provide much the largest share of power needs and with methalox stores as a backup. But I for one would rest easier knowing there was a power supply that is much less subject to the vagaries of the environment and will keep supplying power for a long time; even if the amount of that power was the minimum necessary to keep everyone alive!
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/04/2023 01:46 am
I think people under-estimate how well solar does even in dust storms.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/04/2023 02:19 am
I think there'll be some nuclear power for the comfort it provides for power security...

Yet reliable ISRU electrical and thermal batteries - 1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2474412#msg2474412) 2 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 3 (https://forum.nasaspaceflight.com/index.php?topic=41427.msg2445518#msg2445518) 4 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2306664#msg2306664) 5 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2470549#msg2470549) - can be deployed at farm scale.  Cargo mass fraction might be 1%.

The value of simple, low-tech scaling is often overlooked, when that value pushes out a popular high-tech concept.  Still, a farm could store as many TJ as you like, using waste product.  Many plausible options could be explored in a more active power thread.

Cheap PV and cheap ISRU battery options end the case for $ hundreds of millions - $ billions? - of specialty nuclear development here.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/04/2023 03:37 am
I think there'll be some nuclear power for the comfort it provides for power security...

Yet reliable ISRU electrical and thermal batteries - 1 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2474412#msg2474412) 2 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2305349#msg2305349) 3 (https://forum.nasaspaceflight.com/index.php?topic=41427.msg2445518#msg2445518) 4 (https://forum.nasaspaceflight.com/index.php?topic=53443.msg2306664#msg2306664) 5 (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2470549#msg2470549) - can be deployed at farm scale.  Cargo mass fraction might be 1%.

The value of simple, low-tech scaling is often overlooked, when that value pushes out a popular high-tech concept.  Still, a farm could store as many TJ as you like, using waste product.  Many plausible options could be explored in a more active power thread.

Cheap PV and cheap ISRU battery options end the case for $ hundreds of millions - $ billions? - of specialty nuclear development here.
Much depends on who has to pay for the development of the nuclear reactor used.  If, for example NASA, or the department of energy, or the army footed the development bill entirely, the reactor cost would go way down.  What I'm really looking for are construction costs of actual nuclear reactors.  Perhaps in $ per delivered MW of power? If a nuclear reactor is 10 billion$ for 1000 MW, then it's 10 million $ per MW to build.  That would put the 2 MW Mineral reactor at 20 million$, which is about twice what I budgeted for the nuclear power plant.

Perhaps that number is closer to the truth?  Of course nuclear advocates would be quick top point out that much of the cost of the reactor on Earth is permitting and containment, that might not be required on Mars.  So perhaps my 10 million$ cost is not that wrong?
Title: Re: Power options for a Mars settlement
Post by: edzieba on 05/04/2023 08:20 am
I've done some work here (with others) on the cost of nuclear vs solar, but I had handwaved in energy storage, and I would like to go a bit further, and at the same time review this!

https://marspedia.org/Cost_of_energy_on_Mars

Quote from: lamontagne
Cost on Earth:  $800/m2

Bulk-print panels might cost 100x less per square meter.  For example, Paul Dastoor (https://www.reuters.com/business/autos-transportation/australian-scientists-power-tesla-15000-km-trip-with-printed-solar-panels-2022-04-20/) prints half a km at a time, at ~ 100 g/m2, ballparking commercial cost at $8/m2.  His current, short-lived substrate must be upgraded, but PEN might serve.

Also, your nuclear pricing isn't plausible.  NASA has guessed more than its $20 million Krusty demo cost (https://www.sandiegouniontribune.com/business/energy-green/sd-fi-nasa-nuclear-20180523-story.html) to get a Kilopower successor to the Moon, delivering 40 kWe.  (See Phase 1 (https://www.nasa.gov/press-release/nasa-announces-artemis-concept-awards-for-nuclear-power-on-moon) awards.)  You claim $37.5 million to deliver MINERAL's 2 MWe, oddly.  MINERAL is no simpler than Kilopower.  And unlike Kilopower (https://www.tandfonline.com/doi/full/10.1080/00295450.2020.1725382), MINERAL is a grad-school model (https://www.tandfonline.com/doi/full/10.1080/00295450.2022.2072649), on paper.  $37.5 million might cover a lab demo.

...efficiency at this point is between 1 and 2 %...

It was one $ example.  Your article isn't ready until you dig for plausible numbers.

Benyon et al. 2023:  10.8% conversion efficiency (https://onlinelibrary.wiley.com/doi/10.1002/adma.202208561), roll-to-roll printed PV.

Refs.

Beynon, D., Parvazian, E., Hooper, K., Mcgettrick, J., Patidar, R., Dunlop, T., Wei, Z., Davies, P., Rodriguez, R.G., Carnie, M. and Davies, M., 2023. All‐Printed Roll to Roll Perovskite Photovoltaics Enabled by Solution Processed Carbon Electrode. (https://onlinelibrary.wiley.com/doi/10.1002/adma.202208561) Advanced Materials, p.2208561.
When I fist did the text, solar won because the nuclear side was Kilopower.
Then someone proposed the larger reactor described in the text, and the situation changed.  Nuclear got competitive again.
The article was written before these cells came along.  Of course, the situation evolves.  Perhaps China will provide a cheap nuclear reactor next year and then everything needs to be calculated again.  The 500$/m2 is perfectly reasonable for a low mass system of conventional cells at 30% efficiency.  a bit optimistic, even.
I fully expect solar to outperform nuclear.  It's just that at the time I wrote this it wasn't the case, when compared to an advanced nuclear reactor that was subsidized in development.
So I guess I may update this, but the main point of the article was to determine a cost for electricity on Mars, and I still think I'm not too far off at this point.
Using the energy cost, it's possible to calculated embodied energy costs, and then all that is left is to determine labor costs and you can cost constructions on Mars.  Seems like a interesting tool to me.

It's a Wiki, if you want to participate, just contact the Mars Society!
The key takeway from this process should probably not be "today solar is better" or "today nuclear is better" but "both options are so neck and neck that other operational considerations should probably be making the decision". i.e. do you want to be dealing with the headaches of a nuclear system (needing to procure, handle, and transport nuclear material) or a solar plus storage system (extensive setup process, uncontrolled non-constant power input).
It's no good picking a solar system because it's a few $/khw cheaper if it requires your small station of 10 to have a crew of 200 (or needing to ship over 200 construction robots massing as much or more than the solar array system, and also needing power) in order to set the system up in a short enough time to support your small base before the initial seed stored provisions run out. And its no good picking a nuclear system because it's a few $/khw cheaper if it requires spending a decade wrangling with authorities just to assemble the necessary legal framework to allow you to even purchase the HEU you want. etc.
Title: Re: Power options for a Mars settlement
Post by: Greg Hullender on 05/04/2023 12:57 pm
What solar storage system did you guys have in mind? If it has to store power for months at a time, I think that's going to up your costs quite a bit.

I wasn't aware that there was any way to get solar panels to do much during a severe dust storm. Correct me if I'm wrong, but the effect of tau on energy output should be exp(-tau), and tau values of up to 11 have been recorded. To my mind, that means essentially zero output from the solar panels for weeks or months at a time.

Again, you can solve that just by having a gas generator for backup and using extra solar power to keep oxygen and methane tanks for it filled up, but now you're paying for that system on top of your solar panels. At that point, I'm not at all sure that your system still beats nuclear in price.

Are you assuming that solar panels are fabricated on Mars, saving the transport cost? Have you factored in the mass of the fabrication equipment required to make them? How many megawatts of panels do you need to make before you reach the breakeven point?

I could believe that solar will eventually be the solution on Mars--in a century or two, when the population there reaches a million--but, to start with, it's hard to see how anything but nuclear could work.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/04/2023 01:14 pm

The key takeway from this process should probably not be "today solar is better" or "today nuclear is better" but "both options are so neck and neck that other operational considerations should probably be making the decision". i.e. do you want to be dealing with the headaches of a nuclear system (needing to procure, handle, and transport nuclear material) or a solar plus storage system (extensive setup process, uncontrolled non-constant power input).
It's no good picking a solar system because it's a few $/khw cheaper if it requires your small station of 10 to have a crew of 200 (or needing to ship over 200 construction robots massing as much or more than the solar array system, and also needing power) in order to set the system up in a short enough time to support your small base before the initial seed stored provisions run out. And its no good picking a nuclear system because it's a few $/khw cheaper if it requires spending a decade wrangling with authorities just to assemble the necessary legal framework to allow you to even purchase the HEU you want. etc.
I agree, and one of the points of the exploration was to see if there was a clear advantage in cost of energy that might offset things one way or another.  From what's I've seen there isn't.  So context/availability/constructability will decide, rather than this or that obvious solution.
As a personal conclusion, looking at technology on Earth today, solar is in the lead.  Combined with storage, it can provide the required energy for Earth, and for a Martian settlement.  So there is no obligation to develop a nuclear solution.  It's a nice to have.

The other point that interests me is to estimate what might be the energy cost on Mars in absolute terms, and then use the theory of embodied energy to determine what things produced on Mars might cost, and relate this to what kind of money might be available to produce that good/product.  Basically in the optic of a growing Martian settlement, and not of the first pioneering years.

And although it's a discrete change, I did quantify short term and long term storage costs for solar and included those in the article, so I feel I've reduced the handwaving a bit.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/04/2023 01:25 pm
What solar storage system did you guys have in mind? If it has to store power for months at a time, I think that's going to up your costs quite a bit.

I wasn't aware that there was any way to get solar panels to do much during a severe dust storm. Correct me if I'm wrong, but the effect of tau on energy output should be exp(-tau), and tau values of up to 11 have been recorded. To my mind, that means essentially zero output from the solar panels for weeks or months at a time.

Again, you can solve that just by having a gas generator for backup and using extra solar power to keep oxygen and methane tanks for it filled up, but now you're paying for that system on top of your solar panels. At that point, I'm not at all sure that your system still beats nuclear in price.

Are you assuming that solar panels are fabricated on Mars, saving the transport cost? Have you factored in the mass of the fabrication equipment required to make them? How many megawatts of panels do you need to make before you reach the breakeven point?

I could believe that solar will eventually be the solution on Mars--in a century or two, when the population there reaches a million--but, to start with, it's hard to see how anything but nuclear could work.
I refer you to the Marspedia article here, that serves as the basis for this recent discussion: https://marspedia.org/Cost_of_energy_on_Mars

Actually, nuclear wins on costs in the mid term optic of the article.  However, direct costs are not everything, and availability in this case is the more important metric, IMHO.  Solar is available.  Low cost nuclear is not.

Most of the energy required on Mars is for fuel production and food production.  If you stop these during a storm, then the low solar power is probably enough to get you through.  Storage is a backup plan because of the "probably" and because there is all that fuel around anyway. 

There is still some diffuse lighting available during a storm (5%??) so likely the solar power doesn't go to zero during the whole day.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/04/2023 01:38 pm


Are you assuming that solar panels are fabricated on Mars, saving the transport cost? Have you factored in the mass of the fabrication equipment required to make them? How many megawatts of panels do you need to make before you reach the breakeven point?


Not in the short or mid term.  Eventually, solar may be produced on Mars.  As there may be a market for Solar from the Moon, and certainly some interest in ISRU from Lunar regolith,  locally produced solar panels might happen sooner than later.  On the other hand a fair share of the cost of nuclear is shielding and cooling.  Shielding on Mars should come very quickly, as it is required for habitat construction.  Cooling, using locally produced metal pipes, should be available fairly soon as well.  So that keeps nuclear in the running.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 05/04/2023 02:51 pm
There is still some diffuse lighting available during a storm (5%??) so likely the solar power doesn't go to zero during the whole day.

Yeah, iirc this is why photovoltaic solar power is way better for Mars than concentrating solar power (which won't work with diffuse light).

if efficient solar greenhouses using entirely natural sunlight were possible at scale.  I have serious doubts.

Why not? Because of the amount of material needed to make the greenhouses?

Mars natural sunlight should be plenty for plants. While the ideal solar constant at Mars is about 40% of Earth's, plants generally can't really use the full intensity of near noon sunlight. And places like Britain have farming work fine at high cloudy latitudes which probably don't get as much sun as equatorial Mars.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/04/2023 04:11 pm
There is still some diffuse lighting available during a storm (5%??) so likely the solar power doesn't go to zero during the whole day.

Yeah, iirc this is why photovoltaic solar power is way better for Mars than concentrating solar power (which won't work with diffuse light).

if efficient solar greenhouses using entirely natural sunlight were possible at scale.  I have serious doubts.

Why not? Because of the amount of material needed to make the greenhouses?

Mars natural sunlight should be plenty for plants. While the ideal solar constant at Mars is about 40% of Earth's, plants generally can't really use the full intensity of near noon sunlight. And places like Britain have farming work fine at high cloudy latitudes which probably don't get as much sun as equatorial Mars.
Don't want to diverge too much from the topic, but it's mainly that if we do have greenhouses on Mars with Britain or Canada's level of lighting, we should not expect very high levels of production.  So the greenhouses will be very extensive, and just operate seasonally.  It's not that it's impossible, it's just that they will be quite large, and for that reason possibly not competitive with more compact artificially lit grow rooms.  The solution I have seen is to add reflectors, but as you mention reflectors are not that effective with diffuse lighting.

There are some interesting solutions with light pipes, but I don't think that they are really competitive with grow rooms using artificial lighting.  There is an infinite discussion on this in Scaling agriculture on Mars. https://forum.nasaspaceflight.com/index.php?topic=35877.0
Title: Re: Power options for a Mars settlement
Post by: sebk on 05/04/2023 06:59 pm
Kilopower is made with ASRGs, which are more expensive than solar cells even WITHOUT a reactor.

I personally think nuclear power won't compete with solar unless you're dumping heat into the atmosphere, i.e. with a forced air heat exchanger, and with much higher power levels. Kilopower is just way too niche to compete. Even the fuel cost itself might be a problem as kilopower and others use HEU or HALEU, which costs significantly more power MWh-thermal, and they typically operate at lower efficiency than commercial plants (~20-25% vs ~30-35%), and they typically have much lower burn-up than commercial plants. You need kind of a completely different design, which is heavier and therefore much less competitive in the early days, to achieve good economics.

Even with modern "small" (100MWe) modular reactor designs on Earth designed for high burn-up, they still use HALEU and their fuel costs alone are as high as the LCOE of solar power.

I think early Mars efforts might use some auxilliary nuclear power in cooperation with NASA (NASA has many other uses for nuclear power, including as a supplement/replacement for RTGs for outer planets missions), but 99% of electricity will be produced using solar. Once a Mars settlement gets large and gets some domestic manufacturing capacity for heat exchangers, etc, plus a logistics system and demand for gigawatts of electricity, I think nuclear might become viable again as you can use more cost-optimized fuel cycles, maybe use nuclear heat for process heat applications (melting water, etc) which can do dual-purpose for heat rejection. But overall, I think solar will dominate unless some sort of regulatory arbitrage is possible, where nuclear power becomes much easier regulatorily to do on Mars than it is on Earth (as opposed to the opposite, like right now).
I tend to agree and usually just plan for solar.  However, if large scale nuclear happens on Earth, then it will be competitive and possibly advantageous on Mars.  I don't see large scale nuclear happening on Earth anymore, but I certainly see plenty of lobbying for it still.

The main problem is that reactors designed for Earth are useless for space (including Mars). The very optimization criteria are completely different. Earth designs are optimized around copious cooling available. You want radiological safety, efficiency, etc. You don't care much about mass. On Mars you don't want too much efficiency because your radiator farm size would explode (higher efficiency means lower grade heat requiring radiator area growth with the inverse 4th power of temperature). And your containment requirements are much more lax. And, you do care about the mass a lot.

I think that just food production on Mars will produce so much waste heat that cooling a Martian settlement will be the main issue, not heating it.  So I don't see much for use case for nuclear reactor waste heat.

I would be completely wrong on this if efficient solar greenhouses using entirely natural sunlight were possible at scale.  I have serious doubts.

Regardless if you're using greenhouses or artificial light grow chambers, you are going to be much more concerned with cooling, not heating. The rarefied atmosphere doesn't provide much cooling. Only small things or unpressurized things need heating. Due to square-cube law anything remotely large will need cooling (so experience with rovers and landers freezing doesn't translate to even hundreds of people habitat scale).
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/04/2023 07:02 pm
Greenhouses are trying to maximize surface area because they need to maximize sunlight so I don’t think the square cube law necessarily pushes you into being cooling limited for natural light greenhouses.
Title: Re: Power options for a Mars settlement
Post by: sebk on 05/04/2023 08:09 pm
Greenhouses trap a lot of solar heat (guess how the "greenhouse effect" name came about).

You get about 200W/m^2 average heating during the day (~400W/m^2 peak), or ~100W/m^2 during a whole sol.

If you had very poor heat transfer coefficient of 1W*m^-2*K^-1 you could maintain 100K difference.

Typical 3-layer window panes on Earth have 0.5W*m^-2*K^-1. Those are thin and uncoated and have normal 1bar pressure between the panels. By necessity Martian window panes will be no worse than those (and likely better as likely the gap between the middle and the outer panes would be at mars ambient pressure which would reduce heat transfer tremendously). At 100W sol-average solar heataing would create baking oven levels of heat.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/04/2023 08:17 pm
Most greenhouses on earth are single-layer. You’d like to build that on Mars, too, to minimize cost if you can.
Title: Re: Power options for a Mars settlement
Post by: sebk on 05/04/2023 08:27 pm
I doubt Mars building codes will allow single layer windows in spaces which could be occupied by unprotected people.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 05/04/2023 09:17 pm
There is still some diffuse lighting available during a storm (5%??) so likely the solar power doesn't go to zero during the whole day.

Yeah, iirc this is why photovoltaic solar power is way better for Mars than concentrating solar power (which won't work with diffuse light).

if efficient solar greenhouses using entirely natural sunlight were possible at scale.  I have serious doubts.

Why not? Because of the amount of material needed to make the greenhouses?

Mars natural sunlight should be plenty for plants. While the ideal solar constant at Mars is about 40% of Earth's, plants generally can't really use the full intensity of near noon sunlight. And places like Britain have farming work fine at high cloudy latitudes which probably don't get as much sun as equatorial Mars.
Don't want to diverge too much from the topic, but it's mainly that if we do have greenhouses on Mars with Britain or Canada's level of lighting, we should not expect very high levels of production.

Why? I do not think light is usually the limiting factor for crops on Earth... in fact it very rarely is except maybe for a few oddities like shade grown coffee. Plants hit a limit on how much light they can use (light saturation point).

Canada is (except a few areas which are indeed agriculturally rich) poor for agriculture because of climate (short growing season) and very thin or absent soil (Canadian Shield area) - not because of lack of light.

Areas north of the Black Sea are pretty high latitude and extremely productive grain areas.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/05/2023 03:40 pm
There is still some diffuse lighting available during a storm (5%??) so likely the solar power doesn't go to zero during the whole day.

Yeah, iirc this is why photovoltaic solar power is way better for Mars than concentrating solar power (which won't work with diffuse light).

if efficient solar greenhouses using entirely natural sunlight were possible at scale.  I have serious doubts.

Why not? Because of the amount of material needed to make the greenhouses?

Mars natural sunlight should be plenty for plants. While the ideal solar constant at Mars is about 40% of Earth's, plants generally can't really use the full intensity of near noon sunlight. And places like Britain have farming work fine at high cloudy latitudes which probably don't get as much sun as equatorial Mars.
Don't want to diverge too much from the topic, but it's mainly that if we do have greenhouses on Mars with Britain or Canada's level of lighting, we should not expect very high levels of production.

Why? I do not think light is usually the limiting factor for crops on Earth... in fact it very rarely is except maybe for a few oddities like shade grown coffee. Plants hit a limit on how much light they can use (light saturation point).

Canada is (except a few areas which are indeed agriculturally rich) poor for agriculture because of climate (short growing season) and very thin or absent soil (Canadian Shield area) - not because of lack of light.

Areas north of the Black Sea are pretty high latitude and extremely productive grain areas.
Yields are pretty directly correlated with sunlight.  Both for time and intensity.  A short growing season gives the same result as lower light.  Using greenhouses you are limited to the light that is available.  Using grow rooms you can overbuild the solar arrays and make use of the excess power to create more growth in the same area.  I expect solar arrays to be quite a bit cheaper than greenhouses in $$ per m2.
This is just an example for cucumbers, but using the joined graph from "Optimization and control of the light environment for greenhouse crop production" and a conversion ratio of about 2 for umol/m2s to W/m2 you get light saturation somewhere between 400 and 900 W/m2.  This is a lot more light that you will be getting on Mars naturally.

So yes you can use greenhouses on Mars, and yes they will reduce your power usage, but they will require a very large surface for the same overall food production as grow rooms. So I think we should base our power requirement expectations on grow rooms, while experimenting on greenhouses to find out what might be possible to achieve.

Title: Re: Power options for a Mars settlement
Post by: LMT on 05/05/2023 04:10 pm
I think people under-estimate how well solar does even in dust storms.

Martian panels fail in storms; hence landers fail. 

A PV mod could add a tandem red-shift (IR) active layer, such as QD PV film (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2314870#msg2314870).  Tuned QD would harvest storm IR (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2311200#msg2311200).

An all-weather rover would need to scavenge power aggressively.  Here a tethered PV balloon might work, launched with evaporating ISRU greenhouse ammonia.  Zubrin et al. 1998.

The balloon would shed dust as it deforms in the wind.  Additionally, low-voltage electrostatic repulsion might actively clean the balloon, as with the electric curtain of Williams et al. 2022.

Here both IR and atmospheric triboelectric power would be harvested.  Triboelectric power is maximized when PV power is minimized (https://forum.nasaspaceflight.com/index.php?topic=55111.msg2309328#msg2309328).  Nighttime triboelectric power would complete a round-the-clock storm power supply, cheaply.  If ammonia were used, presumably some fraction of night triboelectric power would also warm ammonia to maintain gas phase, > ~ 180 K, during the coldest nights.

Refs.

Williams, S.J., Schneider, J.D., King, B.C. and Green, N.G., 2022. Particle-Induced Electrostatic Repulsion within an Electric Curtain Operating below the Paschen Limit. (https://www.mdpi.com/2072-666X/13/2/288/pdf) Micromachines, 13(2), p.288.

Zubrin, R., Snyder, G., Chew, G. and Lowther, S., 1998. Report on the analysis, design, construction and testing of a prototype Mars micro balloon probe. (https://www.eoss.org/sites/default/files/imported/eoss043/EOSS43summary.pdf) Mars Micro Balloon Probe (MMBP) final report for contract NAS8-98169.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/06/2023 01:49 pm
I don't think that graph is showing what you think it's showing.

The graph plots the light saturation point, not the photosynthetic output.

So hypothetically if at 35 °C the efficiency of photosynthesis suddenly drops from 10% to 1%, that effect wouldn't appear at all on this graph. The graph is only showing us the point when an increase in light stops producing more photosynthesis.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 05/06/2023 03:20 pm
This is just an example for cucumbers, but using the joined graph from "Optimization and control of the light environment for greenhouse crop production" and a conversion ratio of about 2 for umol/m2s to W/m2 you get light saturation somewhere between 400 and 900 W/m2.  This is a lot more light that you will be getting on Mars naturally.

Hm. That's significantly higher than what I had seen before (~10% of full noon sunlight, which would be 100 W/m^2 at best).

It's not a fixed number, and that paper looks like it uses higher than even modern CO2 levels (600-2000 ppmv vs current 420 ppmv... and presumably the old standard numbers were determined at a somewhat lower level) which might explain some of the difference.

But this maybe should be on a Mars agriculture thread, though it is relevant to power needs.
Title: Re: Power options for a Mars settlement
Post by: meekGee on 05/06/2023 07:52 pm
Most greenhouses on earth are single-layer. You’d like to build that on Mars, too, to minimize cost if you can.
This is a non-power question, but how do you build large greenhouses in a cost efficient manner, given the need to pressurize at least partially?

The nice thing about power technologies is that they work unpressurized, and the grow rooms can be compact pressure vessels.

I mean without compact grow technology, doesn't a person require about an acre?
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 05/06/2023 08:08 pm
Most greenhouses on earth are single-layer. You’d like to build that on Mars, too, to minimize cost if you can.
This is a non-power question, but how do you build large greenhouses in a cost efficient manner, given the need to pressurize at least partially?

The nice thing about power technologies is that they work unpressurized, and the grow rooms can be compact pressure vessels.

I mean without compact grow technology, doesn't a person require about an acre?

Sent from my Pixel 5a using Tapatalk
You can use a tent supported by pressure. Inexpensive but fragile. Use enough of them that you can survive the loss of some of them: say 150 one-acre tents to support 100 people.
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 05/06/2023 11:11 pm
This is a non-power question, but how do you build large greenhouses in a cost efficient manner, given the need to pressurize at least partially?
You can use a tent supported by pressure.

Not really. Plants (well, crops) require fairly high pressure; low pressure triggers the drought response and stops growth. (You might be able to engineer genetics around this, but you shouldn't just assume it to make your job easier.) And higher pressures don't allow "tents" or domes or similar structures without anchoring and sealing requirements that eliminate any apparent simplicity of inflatables or non-pressure-vessel-shapes.

Subbing "balloons" for "pressurised tents", your suggestion still stands; but the tendency to see pressure supported structures as "free" is a personal bug.

[Note: I edited this while Dan was posting a reply, so we crossed-over.]
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 05/06/2023 11:13 pm
Re: Sunlight levels vs growth.

You can include artificial lights in greenhouses to augment natural sunlight. Light levels aren't your limit. Although this obviously reduces/eliminates any infrastructure savings from using greenhouses instead of grow-rooms. (However, this does also let you bypass the upper limits. Usually, the saturation of photosynthesis is at a specific wavelength. Tune the light spectrum to lower that limiting wavelength(s) and you can get higher yields.)

It also lets you tune the "seasons". Generally, you want longer "days" during high-growth phases and shorter "days" during flowering/fruiting. (For eg, I've helped people running a grow-room for a certain unnamed cash-crop, and they tended to run 18hrs light/6hrs dark during the grow phase, and switched to 12/12 when they wanted to trigger flowering.) Mars' two year long "Mars Year" is not going to be innately compatible with Earth-evolved plants. And you certainly don't want one crop per "Mars Year", if you can get four or six with overlapping timing to give continuous harvest. So I doubt you could avoid using artificial lights, even in a natural-light greenhouse.

Hence, the trades between greenhouse vs grow-rooms is more about their relative design complexities, not lighting, nor power costs. Which, IMO, makes it off-topic in this thread. [It's a fun topic, but take it to the scaling-ag-on-Mars thread, not here.]

Just don't treat greenhouses as free. Assume the same power requirements as grow-rooms, because chances are, by the time you've added all the systems necessary for greenhouses in practice (thermal management, augmented lighting, etc), you will probably end up at roughly the same power requirements to get the same yields. Because if your planning can't handle the remaining difference, to the point where you have to make assumptions that your ag-systems must save power or your numbers don't work, then your numbers don't work. You are running on such slim margins that you are designing for idealised conditions, hence designing to fail.

[edit: I suspect there's an exception for algae in simple sun-exposed semi-pressurised transparent tubes. I suspect such a system is almost "free", but it's such a novel system (under Mars conditions at least), it's hard to make realistic estimates of infrastructure complexity/power-requirements, IMO.]
Title: Re: Power options for a Mars settlement
Post by: DanClemmensen on 05/06/2023 11:20 pm
This is a non-power question, but how do you build large greenhouses in a cost efficient manner, given the need to pressurize at least partially?
You can use a tent supported by pressure.

Not really. Plants require fairly high pressure; low pressure triggers the drought response and stops growth. (You might be able to engineer genetics around this, but you shouldn't just assume it to make your job easier.) And higher pressures don't allow "tents" or domes or similar structures without anchoring and sealing requirements that eliminate any apparent simplicity of inflatables or non-pressure-vessel-shapes.

Subbing "balloons" for "pressurised tents", your suggestion still stands; but the tendency to see pressurisation as "free" is a personal bug.
Substitute "structure supported by pressure". You just stated that the plants need the pressure, so yes, you will need to engineer the structure to hold the pressure. You will need to anchor and seal these structures no matter how they are constructed. I did not mean to imply that the structure was simple or cheap, just that it is probably cheaper than the alternatives.
Title: Re: Power options for a Mars settlement
Post by: Vultur on 05/06/2023 11:31 pm
I mean without compact grow technology, doesn't a person require about an acre?

Very roughly, yeah. It's highly dependent on what crop, growing conditions, etc. I think you could do significantly better than that with calories-per-acre efficient crops (which wheat/corn are distinctly not, given how tiny a fraction of their mass is actually edible) but given margin etc. it makes sense.

[edit: I suspect there's an exception for algae in simple sun-exposed semi-pressurised transparent tubes. I suspect such a system is almost "free", but it's such a novel system (under Mars conditions at least), it's hard to make realistic estimates of infrastructure complexity/power-requirements, IMO.]

Yeah. It would make a lot of sense to do stuff like that for basic calories, and traditional crops for variety, taste & fresh foods. I think that could be vastly more efficient.

Vascular plants need oxygen and relatively high pressure, but photosynthesis itself doesn't (supposedly it can work even in ambient Martian equator temperatures & pressure/atmosphere composition) so growing things like algae and processing them makes sense.

Mars' two year long "Mars Year" is not going to be innately compatible with Earth-evolved plants. And you certainly don't want one crop per "Mars Year", if you can get four or six with overlapping timing to give continuous harvest. So I doubt you could avoid using artificial lights, even in a natural-light greenhouse.



That makes sense - with the exception of near the equator, where seasons shouldn't matter much.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/07/2023 08:06 am
This is just an example for cucumbers, but using the joined graph from "Optimization and control of the light environment for greenhouse crop production" and a conversion ratio of about 2 for umol/m2s to W/m2 you get light saturation somewhere between 400 and 900 W/m2.  This is a lot more light that you will be getting on Mars naturally.

Hm. That's significantly higher than what I had seen before (~10% of full noon sunlight, which would be 100 W/m^2 at best).

The number you're remembering is most likely the peak efficiency point of photosynthesis.

Note that the peak efficiency point is very different from the peak productivity point. As usual, high thermodynamic efficiency = low density.

https://www.researchgate.net/figure/Photosynthetic-photon-flux-density-PPFD-response-curves-of-net-photosynthetic-rate-P_fig1_226337316
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/08/2023 01:33 am
...you get light saturation somewhere between 400 and 900 W/m2.  This is a lot more light that you will be getting on Mars naturally.

Hm. That's significantly higher than what I had seen before (~10% of full noon sunlight, which would be 100 W/m^2 at best).

The number you're remembering is most likely the peak efficiency point of photosynthesis.

Note that the peak efficiency point is very different from the peak productivity point. As usual, high thermodynamic efficiency = low density.

https://www.researchgate.net/figure/Photosynthetic-photon-flux-density-PPFD-response-curves-of-net-photosynthetic-rate-P_fig1_226337316

Greenhouse power "efficiency" is found in PPF yield:  e.g., the record yield from wheat (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1055676/pdf/plntphys00633-0369.pdf) (image). That yield meets one person's calorie requirement with a plot just 4 m on a side (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2314181#msg2314181), translating into min greenhouse sizing (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2319400#msg2319400).  These are relevant baseline metrics.

See greenhouse refs (https://forum.nasaspaceflight.com/index.php?topic=58013.msg2454971#msg2454971) for other useful numbers, and hunt for better.
Title: Re: Power options for a Mars settlement
Post by: Robotbeat on 05/08/2023 04:29 am
I doubt Mars building codes will allow single layer windows in spaces which could be occupied by unprotected people.
It's not clear you'd want people working in greenhouses without some protection. Greenhouses need as much area as possible.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/08/2023 05:08 am
Automated farming is likely. This doesn't have to be "robots and tracks," an automated farm on Mars could look like this:

https://www.youtube.com/watch?v=s-8_tiGS9DU#t=13

The large grow area could be housed in an inexpensive single-walled structure, with the plant trays brought into a crew-rated structure (via a safety airlock) for handling.

Bringing this back to power, a higher-plant greenhouse will also act as a source of low-grade heat for space heating, hot water, or ice mining. The large amount of transpired water needs to be re-condensed out of the greenhouse air, and this contains the majority of the heat.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/08/2023 12:41 pm
Automated farming is likely.

The ag thread documents many ideas, e.g., Olympus automated farming, with meaningful numbers (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2314680#msg2314680).  Examine that.
 
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/08/2023 02:04 pm
Taking LMTs numbers in the image 100 kWh/day for 2500 kg per day feeds about 2.5 persons per day if they eat only wheat.  100 kWh/day divided by 2.5 = an average power of 40 kW per person.
Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.  My guess is that survival is about 35-40 kW per person, and comfort and pleasure will be more like 60 kW per person, just for food.  If you are investing energy in the food production infrastructure and fuel production as well, I.E using ISRU, power demand might grow to about 80 to 100 kW per person, or 3000 GJ/year.  Greenhouses would reduce this by some significant fraction, giving a large spread of perhaps 1500 -3000 GJ/year as the energy requirement for a Martian settlement. 

Grow rooms with staged growing patterns might allow for a nearly constant demand, compatible with nuclear, while greenhouses and solar would correspond to very large variations in power demand, following availability.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/08/2023 02:28 pm
Automated farming is likely.

The ag thread documents many ideas, e.g., Olympus automated farming, with meaningful numbers (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2314680#msg2314680).  Examine that.

Two different niches. That's automated vertical farming (artificial light), not automated greenhouse technology (natural light). You can (and should) compare both options, but it's not a simple apples-to-apples comparison.

Also I note that their website is defunct:  https://www.grovtech.com/





Has anyone seen a better greenhouse tech than the video? Or since LMT pivoted straight to vertical farming, can we assume that what's shown in the video is the best technology currently available for automating Mars greenhouses?
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/08/2023 02:38 pm
Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.

Higher calorie yield per MJ?  Which reactors?  Post some info.

Automated farming is likely.

The ag thread documents many ideas, e.g., Olympus automated farming, with meaningful numbers (https://forum.nasaspaceflight.com/index.php?topic=35877.msg2314680#msg2314680).  Examine that.

Two different niches.

No, you're just ignoring forum info there, irrationally.
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/08/2023 02:45 pm
No, you're just ignoring forum info there, irrationally.

If you oppose "ignoring forum info," don't clip one part of my post and ignore the meat and potatoes.

You're literally peddling vaporware. The company's claims were almost certainly fraudulent, which is why they don't exist anymore.




If you disagree, you're never shy about saying so. By your silence, you must agree that the tech shown in my video is the best automated greenhouse technology for Mars!  :)

If not, to quote a wise old sage...

Post some info.
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 05/08/2023 03:32 pm
Acetate could provide plant energy and avoid the need for extensive lighting setups.

https://www.snexplores.org/article/innovation-2022-dark-photosynthesis-process-grow-plants-in-dark
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/08/2023 04:16 pm
No, you're just ignoring forum info there, irrationally.

Put it away, LMT. If you oppose "ignoring forum info," don't clip one part of my reply and ignore the meat and potatoes.

If you disagree with anything I say, you're never shy about saying so! Therefore from your silence, you must surely have agreed that the tech shown in the video is the best automated greenhouse technology for Mars. Q.E.D.  :)

If not....  well.... to quote a wise old sage,

Post some info.

Odd.

--

Minimizing Lighting Power

A self-sufficiency greenhouse system would draw power year-round.  You'd look for efficiencies most anywhere.  How to minimize lighting power?  Spectrum-optimized LEDs give a starting point.  Chen et al. 2023 pulsed such LEDs to boost ATP production and dark phase metabolism.  They also installed a luminaire to even out PPF. 

Result: 

Quote
In an actual planting experiment of Brassica chinensis [Chinese cabbage], the average fresh weight of the plants under the pulsed-lighting LED luminaire was 33.1% higher than that under the conventional LED luminaire.

The results showed that the energy utilization efficiency of the pulsed-lighting LED luminaire is 22.9% higher than that of the conventional LED luminaire.

Q:  Their luminaire used a motor.  Can the result be achieved without motors, while leaving all LEDs active?  Might electrically tunable liquid lenses do the job, with little cargo mass?  E.g., shifting focus with ISRU NaCl salt water total internal reflection (TIR) lenses, applying Li et al. 2019 to Chen et al. 2023.  See also Chen et al. 2021.

Refs.

Chen, F., Zheng, J., Ma, H., Zhang, W., Fan, L., Zhang, F., Li, M., Omer, A.A.A., Zhang, X. and Liu, W., 2023. Pulsed-lighting LED luminaire for agriculture with a geometrical optical solution. (https://opg.optica.org/oe/fulltext.cfm?uri=oe-31-4-5609) Optics Express, 31(4), pp.5609-5624.

Chen, L., Ghilardi, M., Busfield, J.J. and Carpi, F., 2021. Electrically tunable lenses: a review. (https://www.frontiersin.org/articles/10.3389/frobt.2021.678046/full) Frontiers in Robotics and AI, 8, p.678046.

Li, J., Wang, Y., Liu, L., Xu, S., Liu, Y., Leng, J. and Cai, S., 2019. A biomimetic soft lens controlled by electrooculographic signal. (https://onlinelibrary.wiley.com/doi/am-pdf/10.1002/adfm.201903762) Advanced Functional Materials, 29(36), p.1903762.
 
Title: Re: Power options for a Mars settlement
Post by: Paul451 on 05/09/2023 01:36 am
Greenhouses would reduce this by some significant fraction,

Only if there aren't additional energy costs elsewhere, due to thermal issues (for example). Or additional infrastructure costs to solve those issues (such as day/night counter-cycling heat-sinks, deployable insulating night covers, etc) that add to the ISRU-materials and energy-of-production demands on the early settlement.

Given the alien environment, and lack of reasonable analogies on Earth, IMO people should take the numbers from fully artificial grow-rooms (as you did) and assume that's the minimum for any ag on Mars. (The reasoning being, as I said earlier, if your numbers don't work without assuming near-free agriculture, then your margins are too slim for the unexpected realities of Mars.)

Grow rooms with staged growing patterns might allow for a nearly constant demand

You'll almost certainly need supplemental lighting in greenhouses -- even if you're not trying to maximise productivity, you will still need to mimic natural seasonal variation to trigger key stages of growth (such as flowering/fruiting). In which case, you can have staged growing in greenhouses just as you can in grow-rooms. It's not a "trade" between the two.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/09/2023 01:05 pm
Greenhouses would reduce this by some significant fraction,

Only if there aren't additional energy costs elsewhere, due to thermal issues (for example). Or additional infrastructure costs to solve those issues (such as day/night counter-cycling heat-sinks, deployable insulating night covers, etc) that add to the ISRU-materials and energy-of-production demands on the early settlement.

Given the alien environment, and lack of reasonable analogies on Earth, IMO people should take the numbers from fully artificial grow-rooms (as you did) and assume that's the minimum for any ag on Mars. (The reasoning being, as I said earlier, if your numbers don't work without assuming near-free agriculture, then your margins are too slim for the unexpected realities of Mars.)

Grow rooms with staged growing patterns might allow for a nearly constant demand

You'll almost certainly need supplemental lighting in greenhouses -- even if you're not trying to maximise productivity, you will still need to mimic natural seasonal variation to trigger key stages of growth (such as flowering/fruiting). In which case, you can have staged growing in greenhouses just as you can in grow-rooms. It's not a "trade" between the two.
Should have added, ' if greenhouses are built at all, they will need to provide food for less energy overall'
As for the trade in growing times, I agree, however some grow rooms could operate all night, leveling out demand for a nuclear reactor.  Otherwise you would need to have a number of reactors idle at night.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/09/2023 01:11 pm
If somebody was serious about nuclear power on Mars and in space, but did not have access to nuclear materials, could they build 'the rest' of the reactor to test our components and add in the actual core at the end?  I believe Kilopower did something like that, using a core simulator in some of their testing?
You could have a 5 MW electrical heater element, at 1200°C, for example, mimicking a core for a 2 MWe reactor?
Or are the nuclear elements of a design more important that purely thermal loads?
Perhaps the electrical conductors might significantly alter the geometry of the core?
Title: Re: Power options for a Mars settlement
Post by: Vultur on 05/10/2023 06:40 pm
Taking LMTs numbers in the image 100 kWh/day for 2500 kg per day feeds about 2.5 persons per day if they eat only wheat.  100 kWh/day divided by 2.5 = an average power of 40 kW per person.
Most foods hold less power than wheat. 

Maybe calorie density per pound of food, but per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/10/2023 06:56 pm
Taking LMTs numbers in the image 100 kWh/day for 2500 kg per day feeds about 2.5 persons per day if they eat only wheat.  100 kWh/day divided by 2.5 = an average power of 40 kW per person.
Most foods hold less power than wheat. 

Maybe calorie density per pound of food, but per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...
All here: https://marspedia.org/Food
It tends to average out but potatoes are 80% edible, rather than 50% for wheat.
Winners are beans and bananas, but potatoes are very good.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/10/2023 09:13 pm
...per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...

All here: https://marspedia.org/Food

Quote
The values are high but remain below record yields...

Your table actually states the record yield for wheat, from Bugbee & Salisbury.  That's not "theoretical" or "below record", but the achieved record, with calorie density an order of magnitude beyond potatoes, in your table.

Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.

Calories = energy.  Do any reactors truly have higher yields?  What are the facts?  They should be in your article.
Title: Re: Power options for a Mars settlement
Post by: lamontagne on 05/10/2023 09:53 pm
...per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...

All here: https://marspedia.org/Food

Quote
The values are high but remain below record yields...

Your table actually states the record yield for wheat, from Bugbee & Salisbury.  That's not "theoretical" or "below record", but the achieved record, with calorie density an order of magnitude beyond potatoes, in your table.

Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.

Calories = energy.  Do any reactors truly have higher yields?  What are the facts?  They should be in your article.
The article doesn't actually cover bioreactors much.  They have a separate entry.  The reactors seems to be able to use thermal energy to produce food, so they are quite efficient.  I have the paper but I haven't used it for a few years.

Yes, they achieved those numbers with a lot of lighting and multiple trays.  the tables are mostly for single layer growth, unless otherwise stated.
The correlation between lighting and growth seems pretty direct. Energy to energy with the conversion efficiency of photosynthesis.  More light =more food.

Density is important in a space ship or a space station, somewhat less in a surface installation, IMHO, and useless at more than one layer for natural lighting due to shadowing.

Title: Re: Power options for a Mars settlement
Post by: LMT on 05/10/2023 10:21 pm
All here: https://marspedia.org/Food

Quote
The values are high but remain below record yields...

Your table actually states the record yield for wheat, from Bugbee & Salisbury.  That's not "theoretical" or "below record", but the achieved record, with calorie density an order of magnitude beyond potatoes, in your table.

Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.

Calories = energy.  Do any reactors truly have higher yields?  What are the facts?  They should be in your article.

they achieved those numbers with a lot of lighting and multiple trays.  the tables are mostly for single layer growth, unless otherwise stated...

No, their single-layer plots are plain in Fig. 1, with guard areas marked and excluded for accuracy.

The reactors seems to be able to use thermal energy to produce food, so they are quite efficient.  I have the paper but I haven't used it for a few years.

Those aren't the yield facts.  OT now.
Title: Re: Power options for a Mars settlement
Post by: LMT on 05/19/2023 05:28 pm
A perovskite (methylammonium lead iodide perovskite) thin film solar cell has been validated after 10 months in space (https://www.nasa.gov/feature/glenn/2023/10-month-voyage-proves-solar-cell-material-survives-thrives-in-space):

Quote
"A lot of people doubted that these materials could ever be strong enough to deal with the harsh environment of space," McMillon-Brown said. "Not only do they survive, but in some ways, they thrived. I love thinking of the applications of our research and that we're going to be able to meet the power needs of missions that are not feasible with current solar technologies."

This result would seem to open the door for commercial space applications of roll-to-roll printed perovskite PV (https://forum.nasaspaceflight.com/index.php?topic=39785.msg2474980#msg2474980).

With perovskite thin films rated at 10-30 kW/kg, and this particular perovskite offering over 20% conversion efficiency (Hoye et al. 2020), the prospective numbers for a space-rated R2R printed perovskite PV system are looking very good.

Refs.

Li, Y., Hoye, R.L., Gao, H.H., Yan, L., Zhang, X., Zhou, Y., MacManus-Driscoll, J.L. and Gan, J., 2020. Over 20% efficiency in methylammonium lead iodide perovskite solar cells with enhanced stability via "in situ solidification" of the TiO2 compact layer. (https://pubs.acs.org/doi/10.1021/acsami.9b19153) ACS applied materials & interfaces, 12(6), pp.7135-7143.
 
Title: Re: Power options for a Mars settlement
Post by: Twark_Main on 05/26/2023 11:12 am
The reactors seems to be able to use thermal energy to produce food, so they are quite efficient.

Holy thermodynamics, Batman!!

Obviously a biological system can't exceed the efficiency of a Carnot engine, so presumably you're talking about some temperature difference between hot and cold. Or are they actually claiming to turn Brownian motion into usable energy?

Can we see the paper?
Title: Re: Power options for a Mars settlement
Post by: Lampyridae on 06/08/2023 11:26 am
Nature article just dropped:

Assessment of the technological viability of photoelectrochemical devices for oxygen and fuel production on Moon and Mars

https://www.nature.com/articles/s41467-023-38676-2