Power for a Mars colony

[Burninate]

So assume you have a magic-powered excavator which can dump Martian regolith into a hopper.

Could anyone do a detailed breakdown of how much energy might be needed to turn that into, say, 500 tons of compressed cryogenic methalox? Where there is a wide variance in possibilities, like water content, split it into 5-50-95 confidence interval estimates.  Based on that energy figure we could determine how much power is necessary for 18 months (or 26+18=44 months, if two-launch option in Mars Direct) of operation.

[CuddlyRocket]

dust storms can be dealt with by having more area of solar panel.

and by storing energy. Eventually you'll be cracking CO2/water anyway.

Dust storms will be dealt with by a combination of measures. Some overcapacity of the solar panels as you state; there'll be battery storage for night time in any event, and there can be overcapacity there; and there'll be protocols for reducing power usage, stopping some activities, turning lights down etc.

The ultimate back up will be simply running the methane and oxygen stores for your ISRU propellant through an internal combustion engine attached to a generator, probably an engine normally used in a transport vehicle. (And shutting down propellant manufacture could be one of the activities stopped during a dust storm.)

Solar power will be the initial option, because with all the other attendant difficulties in starting a Mars colony no-one will want to get into a full-scale political war with environmentalists over launching a nuclear reactor into space!

[gospacex]

So assume you have a magic-powered excavator which can dump Martian regolith into a hopper.

Could anyone do a detailed breakdown of how much energy might be needed to turn that into, say, 500 tons of compressed cryogenic methalox?

We had a discussion here about processing Martian CO2 into CO + Oxygen fuel combination. IIRC the conclusion was that its Isp is low-ish, but not too bad.

You may avoid needing that excavator. Ditto for PITA of extracting and purifying water from regolith.

[Burninate]

So assume you have a magic-powered excavator which can dump Martian regolith into a hopper.

Could anyone do a detailed breakdown of how much energy might be needed to turn that into, say, 500 tons of compressed cryogenic methalox? Where there is a wide variance in possibilities, like water content, split it into 5-50-95 confidence interval estimates.  Based on that energy figure we could determine how much power is necessary for 18 months (or 26+18=44 months, if two-launch option in Mars Direct) of operation.

The 10,000 foot view is that if martian soil is approx. 2% water, then you'd need to crush regolith and heat it above 0 degrees Celsius to free the trapped water.  Your energy cost (after harvesting the soil) is going to be the energy expended to crush the rock, and the energy needed to heat soil of a certain density above freezing.  The latter could be done like a salt pond though.  Spread the soil out under a dome and allow the sun to heat it up, then collect the water vapor through a passive dehumidifying process (at night).

I think it'd be cheaper to drill to an aquifer, and/or use heated rods sunk in the ground from the reactor to free water and cool the reactor.

And after that?  Once you have the water & the CO2 atmosphere, how much energy is involved in turning that into, presumably, methane+LOX?

[RanulfC]

A completely unshielded, minimum-coolant-encased fission reactor of any substantial size outweighs solar & cosmic ray radiation by many orders of magnitude.  We keep them behind tons of concrete in addition to the containment dome for a reason.

Uhm, you are aware of the fact that a Nuclear Reactor is in fact NOT itself "behind tons of concrete" in-addition-to-the-containment-dome? Inside the dome the reactor is surrounded by two "shells" the outer mechanical shell and the inner pressure vessel. The containment dome itself is designed to NOT block radiation from the operating reactor because it doesn't put OUT that much radiation in the first place. Between the core design and the sheilding built into the pressure and mechanical vessels there is really no significant radiation exposure within the dome.

The "tons-of-concrete" are meant foremost to protect the reactor itself from OUTSIDE forces with a secondary purpose of containing and encapsulating the reactor in case of a total structural failure (meltdown) scenerio. Contrary to the popular (but highly incorrect) "China Syndrome" theory they are specifically designed to handle the latent heat of a reactor core during melt down and contain the materials.

However the Navy does not operate any of its shipboard reactors behind "tons-of-concrete" and don't seem to have entire ships companies dropping dead of radiation sickness now do they? (I have freinds who served in the Navy who pretty much slept on top of the reactors who don't have any health issues. Well, ok, other than the mental ones that usually took them along the path to being squids in the first place...)

Lastly the Army designed, built, and tested several small nuclear power plants (including one that was until very recently powering the American Antarctic base) that were run in close constant proximity with people with no problems. So in essence your "assumption" of nuclear reactor design requirements and systems is VERY inacurrate and seriously needs updating/research.
For example:

Aside from normal operation, the prospects for a nuclear accident are substantial in a harsh unfamiliar environment, even if we suspect our design is passively safe on Earth.

We have had over 50 years of experiance designing and building various types and styles of reactors here on Earth and both the simulation and practical experiance database are extensive. Designing "passive" safety into a reactor is actually pretty easy. Reactors have been designed and tested for conditions far worse than we will find on Mars, (the Moon comes to mind) and "assuming" that the engineers are not capable of CONFIRMING design safety (no "suspect" involved) prior to operation is ignoring the entire history of nuclear power generation.

The reactor being several kilometers downwind provides a safe buffer from even the worst meltdown / explosion / contamination risk, and is a cheap substitution for providing the traditional precautions against the worst case scenario, which we have the mass to do here on Earth.  On Mars, anything more complex to manufacture than structures an electric backhoe can make is inherently questionable.  I would like to see things like bricks produced, but I wouldn't bet colony success on it.

Nuclear power reactors are designed around the basic assumption that there is no such thing as "down-wind" from them during an accident. They are designed and built to NOT include such factors during an emergency, but such factors are "additive" to the safety factor. On Mars a properly designed and built reactor would simply be inclosed in regolith bermed and covered structure. Since it would not be a "pressurized water" design there would be no "explosion" possible so the only "real" threat to worry about would be melt down which would be mitigated by proper siting. (You don't dig the reactor in, you put it on the surface and let the ground soak up the heat of a melt down. Neither would it require "brick" or "concrete" for the structure it could be as simple as regolith filled "bags" or tubes)

A breeder reactor is something we'd have to master on Earth before we could think about using it on Mars.

And here's where I now KNOW you don't know anything about EARTH nuclear power let alone nukes for Mars!

We've had "breeder" reactors since the begining of the, point of fact that's exactly what the first "reactor" ever built was for! Plans were in work to build 4 or more "breeder" reactor facilities across the US for power and plutonium production before President Carter cancled the program. Most "nuclear weapons" owning nations have operational breeders for weapons grade plutonium production. (IIRC the US is the only one that currently doesnt)

A breeder reactor for Mars is problimatical not for the reactor but for the needed infrastructure and systems needed to reprocess the fuel rods once they reach certain levels. (Operationally you basically take apart and rebuild the reactor core every couple of months to continue the "breeding" process and remove "spent" materials)

A straight-up, long-life uranium or thorium power reactor design would be operationally simpler and easier to use.

A U238-fueled breeder is something that would be immensely useful, but that we have not done successfully on a commercial basis yet.

I'd suggest looking up the cycle to see how breeder reactors work before you go to far:
http://en.wikipedia.org/wiki/Breeder_reactor

We've built and operated them before, but interest declined as political pressure mounted and uranium supplies became more abundant.

Nuclear tech back when we were building reactors was every bit as hamstrung by conservatism and the lobbyists of interested parties as rocket launch tech was 10 years ago - with the difference that a lone billionaire is not sufficient to disrupt the nuclear industry.

Which is why Bill Gates is "teaming-up" with some buddies to try and "disrupt" things in the nuclear power industry rather than going it alone

*Hopefully* as we start to rev up the nuclear powerplant building corporate engines again, we'll opt for gen 4 designs exclusively - we should have been perfecting them for the last 30 years, once it became clear that gen 2/3 designs could fail catastrophically.

While I agree with the sentiment I have to point out that ANY power plant can "fail-catastrophically" if given the chance (When asked a Solar Engineer during the construction of our local solar plant pointed out that "catastrophic" failure is a very relative term. People tend to "assume" that something like a solar panel farm can't "fail" catastrophically, but if you are anywhere near a failed pipe connection that is spewing liquid salts or under a scafollding with welds that fail it is just as "catastrophic" as a steam pipe or boiler exploding. In any case you're not going to be "happy" with the results )

On Earth, once-through cooling systems are often considered wasteful, particularly by the cities downstream during droughts.

Actually on Earth, especially in the US regulations require that there be NO "significant population" downstream of a nuclear reactor Silly, but the induced "fear-mongering" about radiation contamination rammed through a lot of rather "silly" regulations over the decades.

Lastly I'm going to point out that almost all your points are centered around the assumption of a pressurized water reactor design, which are NOT the ones being suggested nor the ones that have been previously researched and designed for off-Earth applications. Can I suggest you take some time to study the different reactor designs that have been suggested instead of just applying a single general type to base your arguments on?

Randy

[RanulfC]

And after that?  Once you have the water & the CO2 atmosphere, how much energy is involved in turning that into, presumably, methane+LOX?

Zubrin baselined an SP100 (100kwe) reactor for MD.

And I should probably point out that the various "questions" about heat dissipation problems are missing the fact that this (along with most suggested off-Earth nuclear power reactors) is a SPACE nuclear power design. It is in fact designed to operate in a VACUUM with a fully SELF-CONTAINED heat radiation system

For reference here's the SP100 report online:
http://www.osti.gov/scitech/servlets/purl/10184691

Its not a pressurized water system but a thermionic (http://en.wikipedia.org/wiki/Thermionic_converter) system. And a lot of discussion of off-Earth nuclear power has most recently been in reviving and updating the designs for small or compact nuclear power reactors which were extensivly studied in the late 50s and through the 1960s.
(http://www.world-nuclear.org/info/Nuclear-Fuel-Cycle/Power-Reactors/Small-Nuclear-Power-Reactors/)

Though the US Armies original design for a "compact" reactor design (SL1) was a failure later designs, such as the PM-2 reactor at Camp Century in Greenland (http://www.thuleforum.com/alconotebook.htm) were a success.
List of various Army power reactors and cycles:
http://alternatewars.com/BBOW/Nuclear/US_Army_Reactors.htm

(It's actually interesting to note that the US Army is again activly researching mobile nuclear power: http://www.usmilitariaforum.com/forums/index.php?/topic/37995-the-army-nuclear-power-program/, http://www.almc.army.mil/alog/issues/SepOct01/MS684.htm)

Randy

[guckyfan]

I am not sure what technological readines level this is but demo plants are being built. It sounds promising for the needs of Mars assuming nuclear is not available.

http://spectrum.ieee.org/energywise/energy/the-smarter-grid/new-flow-battery-aims-to-replace-gas-plants/#.U37i_bCIBD0.facebook

Iron-Chromium Flow Battery Aims to Replace Gas Plants

The membranes would have to be brought in from earth for the power throughput needed. The electrolytes could probably be sourced locally quite early. So the storage capacity can be increased by adding tanks unlike other battery concepts.

[john smith 19]

<long post snipped>

I will have to admit that PWR's are the most common design of nuke on the Earth.

Basically because the effectively the USN paid the development tab and that let Westinghouse knock them out cheaper than less developed (if better) types. 

For a lot of people therefor "nuclear power reactor" --> PWR. 

So it's understandable that if you were uninformed on the subject that's what you'd know.

I think there are a couple of questions that if you're designing a colony nuke you need to think about.

1) Will the colony be self supporting or will all reactors be imported from Earth? If you want to be self sufficient a simpler design is better. I'd suggest that means no enrichment (or as Yoda might put it: "Enrichment leads to the dark side.") Natural circulation (no pumps to design, build or have shipped in) and a molten metal coolant (my preference is Lead. Sodium does not mix well with water and Bismuth generates Gammas and Po210, which has limited uses unless you've a long list of investigative journalists you want to kill  Mercury has been used as a reactor coolant, but do I need to say it's highly toxic?) It's a containment vessel, not a pressure vessel, which should be much easier to construct out of available material.

No you can't buy such a reactor, but that does not make its design impossible.   

2) Capacity. Natural circulation reactors are believed capable of operation up to about 400MW thermal. AFAIK the Lead Bismuth Eutectic ones on the Soviet Alpha class submarines were in the 10s of MW range and were the fastest in the fleet. The USN single attempt (the "Skipjack" IIRC) used Sodium. It was not a success. 

So is 400MW thermal enough?

Incidently since this thread is specifically about Mars the heat dissipation problem has some features.

Earth based nuclear plants have use CO2 as a coolant, for example the UK "Magnox" and AGR types. Also the idea of "process heat" to run industrial processes (or just heating the base) would be an option.

At the end of the day Mars may not have much of an atmosphere but it does have an atmosphere.
[EDIT Incidentally the thermal Vs breeder debate is a bit of a red herring as AFAIK all thermal reactors "breed" some of their U238 into Pu239 and then burn it internally. IIRC something like 50% of the power in some reactors comes from that breed/burn process, conducted without any reprocessing.

The more I read about reactor types the more I think that this obsession with fission product containment is not the way to go. People want burn up but don't want reprocessing yet they insist that fission poisons must  remain intimately mixed with the fuel.

Just hypothetically I wonder what would happen if you could let Kr and Xe be vented to some kind of "plenum" out of the way, and how that affects the burn up. In reality this is one of the key abilities of the molten salt reactor, because the fuel is not broken into sealed solid packages. ]

[ncb1397]

http://cleantechnica.com/2013/04/24/high-concentration-photovoltaic-thermal-system-from-ibm-promises-80-efficiency-potable-water-and-air-conditioning/

Provides both heat and electricity. The Photovoltaic cells, motors and control electronics are imported. Most of the mass would be constructed from insitu materials. The power feeds energy storage when sunlight is available. Night time storage is done through battery power. Long term emergency backup for the inevitable global dust storm(happens about once every 3 years) is through reservemanufactured chemical fuel that also run the cars, trucks and rockets.

[A_M_Swallow]

Here is a simple way of making concentrators with local materials on the Moon and Mars.  The wooden frame can be replaced by stone.  Stainless steel can be replaced by aluminium or any shiny metal.  To power a turbine feed the water through a row of them.

[GregA]

The 10,000 foot view is that if martian soil is approx. 2% water, then you'd need to crush regolith and heat it above 0 degrees Celsius to free the trapped water.  Your energy cost (after harvesting the soil) is going to be the energy expended to crush the rock, and the energy needed to heat soil of a certain density above freezing.  The latter could be done like a salt pond though. 

Is there a chance that isru water requirements might be tied to other related mining?

So your generation needs are not just water reclamation and conversion to methalox etc, but also includes mining equipment and ore processing.

It's the larger power requirements that always turn me away from solar.

[Vultur]

Solar power will be the initial option, because with all the other attendant difficulties in starting a Mars colony no-one will want to get into a full-scale political war with environmentalists over launching a nuclear reactor into space!

Exactly.

(Also, SpaceX is probably the most 'credible' group seriously talking about Mars colonization right now... and Elon Musk is also chairman of a solar power company. So I'd tend to think SpaceX would be thinking along solar rather than nuclear lines.)

EDIT: Mars One is also talking about solar power, not that I seriously expect them to get that far...

[Dalhousie]

It's the larger power requirements that always turn me away from solar.

What qualifies as larger power requirements?

[ChrisWilson68]

SpaceX is probably the most 'credible' group seriously talking about Mars colonization right now... and Elon Musk is also chairman of a solar power company. So I'd tend to think SpaceX would be thinking along solar rather than nuclear lines.

I wouldn't be so sure about that.  Musk is an idealist in his long-term goals but a pragmatist in doing what it takes to achieve them.  He has said space-based solar power beamed to Earth is nuts, even though he runs both a solar and a space launch company.

Musk has never committed to a power source for a Mars colony and probably hasn't decided yet, but has mentioned nuclear as a possibility.  I have no doubt Musk will go with nuclear if that gives his colony on Mars the best chances.

[savuporo]

It's the larger power requirements that always turn me away from solar.

What qualifies as larger power requirements?

Again, solar can be feasibly gradually expanded with mostly in situ materials - without too complicated tooling setup. Dopants are small quantities and can be brought from earth.

[ChrisWilson68]

It's the larger power requirements that always turn me away from solar.

What qualifies as larger power requirements?

Again, solar can be feasibly gradually expanded with mostly in situ materials - without too complicated tooling setup. Dopants are small quantities and can be brought from earth.

But you need very high purity of your semiconductor material.  The whole reason that you only need a very small amount of dopants is that it only takes a small amount of impurity to change the properties of a semiconductor drastically.  It would take a large, complex industrial plant to refine silicon or any other material to the needed purity for solar cells.

It would be far easier, at least until a large industrial city is established on Mars, to bring a nuclear reactor core from Earth.

If you're really against nuclear, some sort of solar thermal electrical plant would be easier to produce on Mars than photovoltaic cells.

[john smith 19]

But you need very high purity of your semiconductor material.  The whole reason that you only need a very small amount of dopants is that it only takes a small amount of impurity to change the properties of a semiconductor drastically.  It would take a large, complex industrial plant to refine silicon or any other material to the needed purity for solar cells.

Depends what you mean by "industrial scale." Simpler systems with lower throughput might be just as good for start up colony, and more adaptable for other uses. "Zone melt refining" would be an obvious choice. Slower but the induction furnace could be used for other things.

It would be far easier, at least until a large industrial city is established on Mars, to bring a nuclear reactor core from Earth.

Yes and no. Nukes have the issue of how do you reprocess them at end of life? That supply chain from Earth is long and fragile.

If you're really against nuclear, some sort of solar thermal electrical plant would be easier to produce on Mars than photovoltaic cells.

For a colony that's looking to be independent this seems to be the way to go. Easier to expand the installation and power storage options exist. The NRL did a lot of work in the early 80's under "Solchem" to collect energy by driving cyclic chemical reactions using solar heated reactions then pipe the reactions to a storage system and recombine them. They looked at high temperature salt storage just above the melting point.

Quite a lot of the hardware has been tested and some plants built in the US and Spain. The EU is quite interested in the tech for energy security as well. 

[CuddlyRocket]

SpaceX is probably the most 'credible' group seriously talking about Mars colonization right now... and Elon Musk is also chairman of a solar power company. So I'd tend to think SpaceX would be thinking along solar rather than nuclear lines.

I wouldn't be so sure about that.  Musk is an idealist in his long-term goals but a pragmatist in doing what it takes to achieve them.  He has said space-based solar power beamed to Earth is nuts, even though he runs both a solar and a space launch company.

That's because for the same money you get more power from ground-based solar than space-based. (And a Mars colony will be using ground-based solar!) Also, he may be thinking of the benefits of distributed power generation over concentrated (SolarCity promoting the former); especially if he envisages the colony having a number of outposts fairly quickly.

Musk has never committed to a power source for a Mars colony and probably hasn't decided yet, but has mentioned nuclear as a possibility.  I have no doubt Musk will go with nuclear if that gives his colony on Mars the best chances.

It wouldn't just be up to him; he'd have to get permission to launch it from a number of government agencies.

[ChrisWilson68]

SpaceX is probably the most 'credible' group seriously talking about Mars colonization right now... and Elon Musk is also chairman of a solar power company. So I'd tend to think SpaceX would be thinking along solar rather than nuclear lines.

I wouldn't be so sure about that.  Musk is an idealist in his long-term goals but a pragmatist in doing what it takes to achieve them.  He has said space-based solar power beamed to Earth is nuts, even though he runs both a solar and a space launch company.

That's because for the same money you get more power from ground-based solar than space-based. (And a Mars colony will be using ground-based solar!) Also, he may be thinking of the benefits of distributed power generation over concentrated (SolarCity promoting the former); especially if he envisages the colony having a number of outposts fairly quickly.

You're missing my point.  It's irrelevant to my point whether solar power on Mars is similar to solar power beamed from orbit to Earth.  It's irrelevant whether it's a good idea on Mars or not.  It's irrelevant whether Musk thinks it's a good idea or not.

My point was that Musk will not be biased in favor of solar regardless of whether it's a good idea just because he has an interest in solar power on Earth, which is what the post I was responding to was implying.

Musk has never committed to a power source for a Mars colony and probably hasn't decided yet, but has mentioned nuclear as a possibility.  I have no doubt Musk will go with nuclear if that gives his colony on Mars the best chances.

It wouldn't just be up to him; he'd have to get permission to launch it from a number of government agencies.

Elon Musk knows a thing or two about getting governments to help him. :-)

Virtually everything SpaceX does requires permission from government agencies.  Not only that, but all the SpaceX launch sites are really government-owned pads that Musk has convinced the government to turn over to him.  And not only that but he has managed to convince the government to be a big customer of SpaceX.  And not only that but he has managed to get the government to pay much of the development cost of Falcon 9 and Dragon.

Next to all that, permission to launch some nuclear material seems like a small obstacle.

[savuporo]

It would take a large, complex industrial plant to refine silicon or any other material to the needed purity for solar cells.

Actually no, especially if you are happy with lower performing cells. And there is no reason why one wouldn't be, as there is a lot of available real estate to make up for lower efficiency.

You can make a super low efficiency solar cell out of sheet of copper basically in your kitchen by forming cuprous oxide - but there is a good middle ground between that and commercial grade best performing cells.