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SpaceX Vehicles and Missions => SpaceX Super Heavy/Starship (BFR/BFS) - Earth to Deep Space => 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

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

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

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

ß Human missions can benefit from first userís 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 thatís tricky. Itís 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 itís more mass-efficient. So if youíre taking it to Mars, itís more efficient to ship reactors than it is to ship solar; itís just that nobodyís 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
Theyíve got a program called kilopower going thatís 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 thatís tricky. Itís 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 itís more mass-efficient. So if youíre taking it to Mars, itís more efficient to ship reactors than it is to ship solar; itís just that nobodyís 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
Theyíve got a program called kilopower going thatís 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
Theyíve got a program called kilopower going thatís 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 -40įC 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 -40įC 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 -40įC 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 -40įC 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 ReykjavŪk, 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 ó 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; itís 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 thatís tricky. Itís 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 itís more mass-efficient. So if youíre taking it to Mars, itís 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 theyíre 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 youíre 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 canít 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 SpaceXís presented plans but it can be assumed that what SpaceX is doing is only part of an overall solution.  What Iím 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 įC (218 K; −67 įF).[21] Surface temperatures may reach a high of about 20 įC (293 K; 68 įF) at noon, at the equator, and a low of about −153 įC (120 K; −243 įF) at the poles.[22] Actual temperature measurements at the Viking landers' site range from −17.2 įC (256.0 K; 1.0 įF) to −107 įC (166 K; −161 įF). The warmest soil temperature estimated by the Viking Orbiter was 27 įC (300 K; 81 įF).[23] The Spirit rover recorded a maximum daytime air temperature in the shade of 35 įC (308 K; 95 įF), and regularly recorded temperatures well above 0 įC (273 K; 32 įF), 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. ďThese kinds of products could end up in human protein bars eventually,Ē 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. ďYou would have to modify the process,Ē says Mr Busch-Larsen. ďIt is not for tomorrow.Ē

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 Muskís plans for Mars exploration include generating methane and oxygen for making rocket fuel. Some could be used to make food, too. ďWe have been in touch with SpaceX,Ē 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. ďThese kinds of products could end up in human protein bars eventually,Ē 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. ďYou would have to modify the process,Ē says Mr Busch-Larsen. ďIt is not for tomorrow.Ē
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 Ė 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 wouldnít matter, it could just spiral up and wait for the appropriate window.  It would seem that thereíd 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 youíre trying to avoid problems with dust you donít 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 Ė 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 havenít discussed the other aspects of how the ITS system can support getting materials to Mars doesnít mean they arenít 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 youíll 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 doesnít 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 havenít discussed the other aspects of how the ITS system can support getting materials to Mars doesnít mean they arenít 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 youíll 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 doesnít 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
Itís not the current (as in what kind of current) itís 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 letís 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 doesnít 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 itís 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 youíre 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 youíre 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 youíre 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.  Itís 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.  Youíll find similar situations in mining.  Itís 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 thatís what theyíll do.  But if they have to make an item from scratch, then thatís 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 youíll 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 canít just turn off electrolysis during a dust storm.

And itís worth pointing out that because most power consumption will be due to ISRU, if ISRU is shut down temporarily, then thereís 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 donít have to burn your precious propellant, just stop electrolysis.

Letís 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.

Itís like growing crops: a cloudy week doesnít 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 canít just turn off electrolysis during a dust storm.

And itís worth pointing out that because most power consumption will be due to ISRU, if ISRU is shut down temporarily, then thereís 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 donít have to burn your precious propellant, just stop electrolysis.

Letís 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.

Itís like growing crops: a cloudy week doesnít 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 isnít 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 donít 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
Iím probably going to regret posting this as itís 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 doesnít 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 youíre 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 wasnít 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 youíll 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 canít 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 donít scale very well or donít 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: ďWhen the only tool you have is a hammer you tend to treat everything as if it were a nail.Ē  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.  Thereís 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 doesnít 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 donít get onto this new nuclear technology other countries are pursuing it to a massive amount.  India is now looking at building these reactors today.  Theyíve 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 donít build such a reactor in the United States, theyíll go to China and have them build the reactor.  If the US government wonít 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 doesnít 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 youíre 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 wasnít 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 youíll 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 canít 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, itís 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 2020ís 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, itís 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 2020ís 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.
Itís 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 Iíll concede. Same with D+He3.
Title: Re: Power options for a Mars settlement
Post by: Elmar Moelzer on 04/21/2018 03:52 am
Itís 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 Iíll 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 weíve 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 doesnít 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 weíve 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 doesnít 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 weíve 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 doesnít 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 ďa lot.Ē The chemical energy of 1kg Of split water is over 4kWh per SINGLE kilogram of water, assuming perfect efficiency. With realistic efficiency, weíre 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 youíll 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
Yíall 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 2500000m≤/s≤ 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 2500000m≤/s≤ 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 m≤ per year on Mars, or something like 20W/m≤ average.

So need something like 50000m≤ 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 m≤ per year on Mars, or something like 20W/m≤ average.

So need something like 50000m≤ 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 m≤ per year on Mars, or something like 20W/m≤ average.

So need something like 50000m≤ 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 5m≥ 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, Iíd 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. Iíd like to buy one. I donít 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
Iíd 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. Iíd like to buy one. I donít 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. thereís 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. thereís 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.

Th