Type of nuclear power plant is needed by Mars astronauts ?

EuroLauncher · 2006-09-10 18:25:19

I'm not talking about Nuke Powered Rockets like Orion (watch out for crazy Wayne) or a GCNR rocket I'm talking about getting electricity and heat for people on Mars and talking about Nuclear Powered mining colonies on Moon/Mars. For power on Mars, it unlikely that wind is going to do much and Solar energy may not provide enough. So the first people on Mars may be getting their energy from device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate. So no talk about 'Fusion-reactors' or such stuff because they only exist in science fiction. Would a PWR or fission fragment reactor work best on a Lunar site or Mars base ?

PurduesUSAFguy · 2006-09-10 19:32:29

I think there a couple of safe bets as for a space/surface power reactor. It will most likley be a conventional arangemeent with MOX fuelrods with in core control rods as well as a rotating reflector drum to provide two methods of reactor shutdown.

As for power conversion I would expect to see a direct Brayton cycle conversion most likley using Helium as the working fluid. Liquid Lithium reactors are a possibility as well but I see major problems with the reliability of liquid metal cooled reactors as the experience with the liquid lead fast reactor on the Russian 'Alpha' class submarines.

GCNRevenger · 2006-09-10 20:15:00

Plain old MOX doesn't have the punch, the fuel will definatly be bomb-grade uranium or plutonium to hold the mass and volume down.

I see there being two options, the first as Purdue's points out is a gas-cooled Brayton setup, most recently explored under the SAFE-400 project. it would be a small reactor, cooled by some inert gas, but has the drawbacks of moving turbines and low radiator temperature (leading to bulky radiators). 400kW thermal/100kW electric output. The plant itself would weigh around a tonne, but the radiators more, so all together with shielding would be a few tonnes probably.

Another option is likely a revival of the 1990's SP-100 project, which would have used a lithium cooled reactor feeding a thermoelectric converter like on an RTG. It would make up for the lousy conversion efficiency (5%) with brute force thermal output and high-ish operating temperatures. 2000kW thermal/100kW electrical output sounds lousy, but the whole plant would have no moving parts except the control mechanism and the liquid lithium, no turbines, no generators, no coolant pumps.

The massive thermal output would also be great for future Mars heat requirements, like extracting water from permafrost underground and the better-than-electrolosys thermochemical cracking of water into hydrogen and oxygen, and later on the same core could be modified wih more efficient conversion systems to quintuple the electrical output for a surface base. Maybe use it to bake the oxygen out of Lunar dirt too. The most efficient way to use nuclear power is to use the heat directly from the core, the hotter the better, and here the SP-100 has an edge for future base applications.

I like this option since its pretty well researched, a billion dollars was already spent on it, and the radiator mass would be very low due to its high coolant temperatures. It would require a bit more radiation shielding, but nothing really extreme. Predicted mass was around 5-6 tonnes.

http://www.uic.com.au/nip82.htm

blueyes · 2006-09-14 15:12:20

How about a smoke detector-like isotope cell?

blueyes

GCNRevenger · 2006-09-14 15:16:10

Not powerful enough. An RTG arrangement of comperable mass would probably only generate a tenth of the power or so, and the cost of the fuel is far higher. Plus, there is no "off switch" for isotope decay, and the fuel of choice for RTGs is actually far more dangerous than plain old Uranium. Uranium is about as dangerous as dirt, unless it is or has recently been used in a nuclear reactor.

Mars_B4_Moon · 2006-09-19 09:42:17

I always had thought something that the Russians use for submarine propulsion or the US Navay reactors copuld become useful for a Mars mission.

What are the main problems with using Solar panels or Windmills for a Mars colony ?

GCNRevenger · 2006-09-19 10:27:04

With exception to the not-so-reliable liquid metal cooled reactors, none of the submarine reactors built are very suitable for space application. The biggest obvious problem is scale, where a naval reactor is far more powerful than whats needed for a Mars mission, running in the low to mid tens of megawatts. The target electrical output for a Mars mission is somewhere around 100-200 kilowatts.

Second is mass, that due to the much higher power output and no signifigant restriction on mass, submarine reactors are too heavy for space use. We need complete power plants, with all ancillary equipment, to preferably be 5MT or less. Thats pretty small by any standard I think.

Third is temperature & cooling, that naval reactors have an unlimited supply of a rather good cooling fluid (sea water) to keep the thing cooled off, but on Mars there isn't any readily accessable supply of coolant. Therefore, heat will have to be dumped thru radiators, which will be alot different than submarine heat exchangers. The temperature the reactor operates at is also important, that the higher the temperature the smaller the radiators you need. Naval reactors generally operate at lower temperatures, while space reactors need to be run as hot as reasonably possible.

I think the best option is to revive the 1990's NASA/USAF SP-100 reactor; it would be relatively light, very compact, and very reliable. Plus, in the future the cooling system could be upgraded to generate much more electricity without having to alter the core. It also generates very large amounts of heat for a reactor its size/mass, and this excess heat could later go into melting subsurface permafrost, thermochemically splitting water into Oxygen & Hydrogen, and supplying needed heat to a future heavy ISRU plant. Perhaps even provide heat for large greenhouses. You won't get these bennefits with solar or wind.

Solar and windmills?

-Martian windmills wouldn't have the output nor the reliability. Very bulky too.
-Solar pannels only get half the light on Mars than Earth, and thats best-case with little or no dust. It could drop to a fraction of Earth-normal in a dust storm. Dust is also known to adhere to solar cells, which would require daily maintenance.
-Solar pannels don't work at night, nessesitating a very reliable power storage system plus low overnight power consumption. This multiplies the size of ISRU equipment if it can only operate half the day, and you couldn't recharging vehicle/equipment batteries overnight.
-To supply full 100-200kWe continuously so as not to affect other equipment, the solar array would have to generate 300-600kWe with a 50% efficient storage system.
-This is all assuming a full 12.25hr of operating time at full power, which would require sun-tracking cells and an equitorial landing site. If you used non-tracking cells and/or land anywhere away from the equator or even in shadowed terrain, the output needed could run up to 1MWe. This would likewise nessesitate an even larger and heavier power storage system.

Its a much better idea just to bring a damn reactor!

RobS · 2006-09-19 11:57:44

GCNR, eventually would air cooling work for reactors? I doubt we'd want to use it on the first missions. A cubic meter of martian air masses about 0.1 kg, I think. A two meter in diameter intake with fans blowing the air at 50 meters per second would push about 15 kilograms of cold air (average, 50 below) past a radiator per second. That could provide a decent amount of cooling.

-- RobS

GCNRevenger · 2006-09-19 12:05:50

I doubt it would be effective given how thin it is, direct air cooling hasn't been used since the early days of atomic bomb fuel piles. Plus, how do you get the energy out of this thin, cold, possibly dusty air coming through the reactor? And why would you want to? Isn't it better if the coolant is a fluid that you can pass through pipes to do with as you want? A melt down is another issue, that if you leave the blowers running it will shower the area around the core with fallout, but if you turn them off then the core will really heat up.

The SP-100 is a good solution, liquid lithium cooled, circulated with non-moving magnetic "pumps" through non-moving thermocouples and very compact high-temperature radiators. A billion dollars has already been spent on its engineering, and if you piped the lithium through a heat exchanger instead of radiators you can make a much more powerful power plant without signifigant change to the core later.

GCNRevenger · 2006-09-19 12:16:33

Also nice: the SP-100 would probably work on the Moon with essentially no modification at all versus the Martian version.

Austin Stanley · 2006-09-19 15:28:06

GCNR, eventually would air cooling work for reactors? I doubt we'd want to use it on the first missions. A cubic meter of martian air masses about 0.1 kg, I think. A two meter in diameter intake with fans blowing the air at 50 meters per second would push about 15 kilograms of cold air (average, 50 below) past a radiator per second. That could provide a decent amount of cooling.
-- RobS

I disagre with GCRN here. Harnesing the martian air to help augment cooling is highly logical and practical. As we all know their are only 2 ways for us to get rid of heat, radiation (which is the only method the SP-100 uses) or conduction (wicking away heat with something like water or gas), or to simply through the heat away with something.

Radiation is the default answer, but is not very practical. Radiation is a very inefficent way of getting rid of heat, unfortunatly, it's the only game in space or the moon, where conduction is not practical (only thing to conduct the heat to is the ground).

Convection on the other hand is much, much more efficent than radiation. This is why power-plants and the like are cooled with river water rather than massive radiators. It is true that Martian air is probably not a very good conductor of heat compared to Earth Air or much less water. But it is still vastly superior to vacume radiation.

Happily the design requirments for radiation cooling and air-conduction cooling are fairly similar. Both are dependant on the hot body having a lot of surface area. Also good radiators are also generaly good conductors. So not much modification is necessary to let you're radiator harness the power of convection, putting a fan in front of it to blow the thin (but very cold) martian air across it's surface would increase the efficency of the system greatly, and could thus lower the mass of the radiator.

The disadvantage is that if you're fan breaks, you're cooling slows down. Which can obviously be a bad thing for the reactor. I would solve this in two ways, firstly I think such a critical item like the reactor should have a back-up anyways. Secoundly, the reactor should be able to moderate itself (I know pressurised water reactors like the navy uses can do this, I'm not sure how self-moderating liqual lithium ones are), and decrease their power-output in case of a fan failure. The Mission should be surviable on this lessened amount of power.

I'm sure we could do it with just Radiation, but since we don't have to, it makes little sense to ignore the options avaliable to us.

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Long term Air-cooling makes even more sense, but their may be even better alternatives in the future. Importing ice for cooling the reactor (or drinking), tapping into underground water and/or ice supplies for cooling, or most likely heating the ground and permafrost on Mars using Martian air as the working medium.

----------

Also I wouldn't dis submarine nuke technology so much. Obviously the power plants use by the navy are not appropriate for use on Mars. They are much to heavy, generaly produce more power than we need, and don't have to worry about the cooling issues. However, the relability and simplicity of these systems is something we do well to emulate. Also, nuclear subs have been the birth place for much nuclear technology that we certianly need, such as liquid metal cooled engines (some Russian subs have some) and self moderating pressurised water reactors.

GCNRevenger · 2006-09-19 18:07:18

I disagree, or a least I am very skeptical;

The low density of the Martian air, over a hundred times thinner than ours, is so puny as to be almost non-exsistant. I doubt that the air is thick enough to accomplish much, or at least increase power output sufficently to justify the development of a different variant than the Lunar version.

And there are signifigant differences, just pointing a fan at the Lunar-style "X" radiators will do little good, since most of the air will not pass close to the surface to carry away the heat. You would also need an awfully big and/or fast spinning fan to move lots of air, which presents mass/volume or reliability issues respectively. Not to mention, just how much power does this fan use?

Anyway, the radiator for an air-cooled plant should be rows of parallel fins with a blower(s) pushing air between them to minimize the distance between air and surface, just like in various automobile radiators. This is exactly the wrong thing if you want radiant cooling, where you want to avoid any parallel planes to minimize re-absortion of infrared radiation. I think it unlikely that natural convection without a blower would be able to maintain minimum backup power.

Given the differences, the radiator array would have to be suited to one or the other function in order to be effective, which presents some further implications: if you included two descrete sets of radiators, in the event the blower fails to produce backup power, this adds signifigantly to the mass and reduces the reliability of the no-moving-parts coolant system, which must now include a bypass valve plus mass and coolant for both systems.

So instead, skip the blower, skip the convection, and instead use this extra mass (if available) for larger radiant radiators to increase the temperature delta across the thermocouples. Not needing to feed power for a blower will probably make up for a good chunk of the difference.

Save development instead for future versions of the reactor, with a low-temperature heat exchanger, probably for heating water or liquified carbon dioxide for permafrost extraction, ISRU heating, or large-scale green house heating. 100-200kWe (depending on modern thermocouples and radiator area) should be enough for the time being until we have a base, especially since the basic radiant SP-100 is fairly light and quite compact, just pack more of them instead of fiddling with the design for unnessesarry middling increases in output with poor reliability.

GCNRevenger · 2006-09-20 07:43:31

Long term Air-cooling makes even more sense, but their may be even better alternatives in the future. Importing ice for cooling the reactor (or drinking), tapping into underground water and/or ice supplies for cooling, or most likely heating the ground and permafrost on Mars using Martian air as the working medium.

Long term air-cooling may be a bit more attractive, when efficiency of conversion and use of precious Uranium is a big deal, but not with the early compact small scale power plants. In the future, perhaps a gas-cooled reactor with electrical outputs in the megawatt range, perhaps based on the SAFE-400 core, then it would make sense to consider air cooling. Even then though, by that point I would hope we would be drilling for permafrost, where we could leave a reseviour of liquid water under ground to act as the heat sink instead of a surface radiator/blower arrangement.

And I wasn't "dissing" submarine reactors, they are fine reactors, they just aren't suited to the purpose. For instance, water cooled reactors are preferred on Earth in part because its easy to build them on large scales. On Mars however, with scarce water, a water-cooled reactor doesn't make as much sense: its still going to be fabricated on Earth, so mass and volume will still be an issue, which points to a gas-cooled or liquid metal cooled reactor, and not a water cooled one.

Yang Liwei Rocket · 2007-10-09 07:38:50

NASA To Accelerate Space Nuclear Power
http://www.spaceref.com/news/viewnews.html?id=1237

JoshNH4H · 2007-11-10 20:52:31

I have no real information to add to this topic, but it is very important, so I am posting to have it brought up to the top for more discussion. I agree, however that mars will be highly nuclear.

cIclops · 2007-11-11 08:49:56

Yes it's an important topic for living on Mars and the Moon, for life support and ISRU.

Perhaps it should be in the Life support systems forum ?

Terraformer · 2007-11-11 10:47:07

I always thought nuclear reactors used the heat to turn water into steam. In that case the water would be taking away the excess heat by tuning into steam. If that isn't true then we need to vastly improve the efficiency of nuclear power plants.

Martian Republic · 2007-11-11 15:57:24

Here my favorite nuclear power plant type. It the Pebble-bed Nuclear reactor. It a forth generation Nuclear power plant that can be built modally and assemble on site to cut cost and for faster manufacturing and assembly.

http://web.mit.edu/erc/spotlights/pp.html

http://web.mit.edu/pebble-bed/background.pdf

Larry,

cIclops · 2007-11-11 16:27:22

Here my favorite nuclear power plant type. It the Pebble-bed Nuclear reactor. It a forth generation Nuclear power plant that can be built modally and assemble on site to cut cost and for faster manufacturing and assembly.

Lots of potentially leaky plumbing connections, but high quality mass production should fix that.

Austin Stanley · 2007-11-12 16:52:12

I don't think a pebble bed type design much merit for a martian design. Its primary design imperatives aren't very important to the martian enviroment.

A pebble bed reactor is designed to be simple to manufacture and to have minimal risk of a meltdown. However on Mars these consideration are less important. I mean if a reactor meltsdown on Mars the biggest concern is loss of power to the crew, not the release of radiation into the inhospitable environment. And since the reactor must be imported and is operated by highly trained individuals, the simplicity and safety of a pebble bed design are also less of a concern.

More important for a Mars reactor is high power/weight ratio. The reactor needs to be as small and light as possible while still meeting the mission power generation requirements. This means that it will probably be some sort of relatively high temperature operating design using fairly highly enriched fuel (maybe not weapons grade, but close). High operating temperatures mean the radiators operate more efficiently, and higher enriched fuel means you need less of it (and also higher operating temperatures).

----

BTW I ran some of the numbers and it appears that GCRN is right, air cooling is not particularly relevant in a Martian atmosphere.

SpaceNut · 2007-11-12 20:36:02

Yes these types are a deliverable for nuclear but it sure would be nice that when we are ready that we could go Fussion instead.

The perfect fuel: N.H. helping to outfit the first fusion reactor

The ITER project hopes to demonstrate the scientific and technological feasibility of fusion energy, using sea water to create an inexhaustible, environmentally friendly energy source. The acronym for International Thermonuclear Experimental Reactor also means "the way" in Latin.
The project is being designed and built by a partnership of the European Union, India, Japan, China, South Korea, Russia, and the United States. The device will be constructed at Cadarache in southeastern France on nearly 100 acres of land

So how much wire is needed???

the full contract would be for nine cables 765 meters long, or a little less than half a mile, and 18,000 pounds each, to be manufactured in mid-2008. The cables are less than two inches in diameter, but contain more than 1,000 strands of wire.

Antius · 2007-11-14 02:10:05

Likely requirements:

1) Compact (as small as reasonably practicable)
2) Low in mass (both the reactor and subsystems)
3) Able to function for years without any significant maintenance
4) Able to operate remotely from any Earth-bound operator.

What do these requirements tell us? The core must have high power density, which generally requires highly enriched fuel. The secondary plant must be very simple and reliable, either eliminating all moving parts (thermoelectric) or using a moving system that is both simple and robust: probably a sterling cycle. Getting good heat transfer out of the core and getting a reasonable theremodynamic efficiency implies the use of very high temperatures, which also implies liquid metal or molten salt coolant, with sodium being the most likely coolant.

This leads us to a small, high temperature, liquid metal cooled, fast reactor, with a sterling or thermoelectric secondary side. Unsurprisingly, the SP-100 includes all of these features.

One more thing; for a long term base: The mass of the subsystems probably dominates the mass of the power plant, the reactor itself being only a small fraction of the total mass. The core will probably incorporate an enlonged fuel assembly and movable reflector, along with burnable poisons, allowing the core to produce power for up to 3 decades without refuelling. The reacto will retire at the end of its core life, given that it would not be practical to consider refuelling it.

One additional complication of mars would be the prospect of martian dust settling of radiator panels following a dust storm. In this respect, the atmosphere is likely to be more of a hidrence than a help.

Gregori · 2008-01-15 00:11:25

I think, why bother?

By the Time Nasa puts a man on the Mars, Fusion power is probably going to be possible. Most of the public would be against putting a fission reactor into space, they already go apeshit about RTG's.

There is no need real requirement for that amount of power in the first missions to Mars, they could easily get by on Solar. Giant Solar panels would be much lighter to carry across space. 40% efficiency is already possible, in 2 or 3 decades, much higher efficiencies will be possible with quantum and nano technology. The wind on Mars has been shown to clear dust of the 2 rover's panels.

I get the feeling some people here just get a boner talking about Nuclear Fission Reactors....

louis · 2008-03-28 19:07:55

Austin Phillips talks of the

"reliability and simplicity of these systems " (i.e. nuclear power systems on subs).

I don't buy into this.

Are you saying we don't have nuclear engineers on board subs? Are you saying the engines don't have to be monitored?

The really reliable system is solar power (as we've seen with the Mars Rovers). And part of the reason it's reliable is that it is indeed simple and difficult to disrupt or destroy.

If we can use ultra thin PV film on Mars then we also have something that will weigh v. little. A few hundred Kgs could produce a great abundance of energy per capita. And it will be reliable and safe.

Swoosh · 2008-04-04 04:12:48

Likely requirements:
1) Compact (as small as reasonably practicable)
2) Low in mass (both the reactor and subsystems)
3) Able to function for years without any significant maintenance
4) Able to operate remotely from any Earth-bound operator.

I would add another -

5) Able to self-deploy and self-start

...since many mission designs, most notably MarsDirect, call for an ERV powered by a reactor to precede the manned craft. I'm sure the startup of many of these systems is quite sophisticated.

On the other hand, solar would need no "starting", but it would be very difficult to deploy 100KW worth of solar panels

I wonder how much 100KW worth of solar would weigh?

Sorry- 200KW worth, because solar doesn't work at night.

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