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I wonder how the affordability equation would change with a nuclear power plant. It could be pretty light weight, there is no need for shielding, and the water

I wonder how the affordability equation would change with a nuclear power plant. It could be pretty light weight, there is no need for shielding, and the water could possibly be used to cool it.

azernik 6y ago
Unclear - NASA is currently working on the Kilopower reactor, which is probably lower-power than the enormous solar arrays SpaceX is considering. However, if they're expanded into the megawatt range they could be usable. Shielding is still required, as humans are not the only thing that's vulnerable - electronic and chemical systems are also vulnerable. Burying the reactor in Martian regolith is probably a more risky project than unrolling a massive solar array. The other problem is the cold. At low latitudes, the temperatures are at a relatively warm Antarctica-like level, sometimes getting to room temperature at the equator at noon. At high latitudes, though, we're talking cryogenics - lows of -150C, averages of perhaps -100C. Making machinery work at those temps is expensive.
- jacobush 6y ago
  I don't understand any of this. On Mars there's a lot of radiation anyway, and humans shouldn't go near the reactor after it's going critical. I don't know what you mean by chemical systems. The point is the reactor doesn't have to be buried, just put it so it's in a crater or behind a ridge (as seen from any settlement) and the radiation is not a problem. As for cryogenics, either make sure it never drops to cryogenic temperatures in the first place, or make something which can be stored at these temperatures. Once it's operational, the temperature should never drop ever again until it's decommisioned.
  - azernik 6y ago
    The cold is a problem not for the reactor itself (it'll heat itself up quite nicely) but for the other gear involved with a settlement. Chemical plants, mining bulldozers, habitat seals - all of these things get seriously weird when you bring them down to ~125K. (For example: IIRC sabatier plants need to run in the high hundreds of K; if you're going to keep that going in a cryogenic environment you need either an enormous amount of insulation or to be willing to lose a lot of energy to the environment.) The obvious solution would be to use waste heat from the reactor in a combined heat and power installation, but then you run into the radiation problem. Coolant tubes or heat pipes that run a significant distance are heavy and bulky, but if you want to move your gear closer to keep that weight down you get in trouble from radiation. Note that it's not just people that are sensitive to radiation - the chemical beds required for fuel and oxygen production, electronics on any moving rovers. If you just want power, that's fine, bury it a few km away; but if you also need heat you're out of luck.

I wonder how the affordability equation would change with a nuclear power plant. It could be pretty light weight, there is no need for shielding, and the water could possibly be used to cool it.

azernik 6y ago

Unclear - NASA is currently working on the Kilopower reactor, which is probably lower-power than the enormous solar arrays SpaceX is considering. However, if they're expanded into the megawatt range they could be usable. Shielding is still required, as humans are not the only thing that's vulnerable - electronic and chemical systems are also vulnerable. Burying the reactor in Martian regolith is probably a more risky project than unrolling a massive solar array. The other problem is the cold. At low latitudes, the temperatures are at a relatively warm Antarctica-like level, sometimes getting to room temperature at the equator at noon. At high latitudes, though, we're talking cryogenics - lows of -150C, averages of perhaps -100C. Making machinery work at those temps is expensive.

jacobush 6y ago
I don't understand any of this. On Mars there's a lot of radiation anyway, and humans shouldn't go near the reactor after it's going critical. I don't know what you mean by chemical systems. The point is the reactor doesn't have to be buried, just put it so it's in a crater or behind a ridge (as seen from any settlement) and the radiation is not a problem. As for cryogenics, either make sure it never drops to cryogenic temperatures in the first place, or make something which can be stored at these temperatures. Once it's operational, the temperature should never drop ever again until it's decommisioned.
- azernik 6y ago
  The cold is a problem not for the reactor itself (it'll heat itself up quite nicely) but for the other gear involved with a settlement. Chemical plants, mining bulldozers, habitat seals - all of these things get seriously weird when you bring them down to ~125K. (For example: IIRC sabatier plants need to run in the high hundreds of K; if you're going to keep that going in a cryogenic environment you need either an enormous amount of insulation or to be willing to lose a lot of energy to the environment.) The obvious solution would be to use waste heat from the reactor in a combined heat and power installation, but then you run into the radiation problem. Coolant tubes or heat pipes that run a significant distance are heavy and bulky, but if you want to move your gear closer to keep that weight down you get in trouble from radiation. Note that it's not just people that are sensitive to radiation - the chemical beds required for fuel and oxygen production, electronics on any moving rovers. If you just want power, that's fine, bury it a few km away; but if you also need heat you're out of luck.