3 ms·

Something like a vacuum flask, I imagine. Vacuum is a very good insulator already and you minimise radiative heat transfer (infrared glow) by making a surface s

Something like a vacuum flask, I imagine. Vacuum is a very good insulator already and you minimise radiative heat transfer (infrared glow) by making a surface shiny and metallic usually (low emissivity)

jstanley 10mo ago
If you have to bring your own vacuum flask, don't you lose half the benefit of doing it in space?
- rokkamokka 10mo ago
  Isn't the primary benefit the lack of gravity?
  - imtringued 10mo ago
    You can reduce metals through vacuum pyrolysis at much lower temperatures without a reducing agent if you have a vacuum. This could make industrial scale processing of steel relatively easy on the moon.
    - pfdietz 10mo ago
      Reducing ferric oxide to magnetite, perhaps, but I think if you tried that with ferrous oxide you'd get iron vapor coming off along with the oxygen. An issue with any high temperature process is things start evaporating. This is part of why carbothermal reduction of aluminum oxide doesn't work: at the required temperature aluminum oxide is volatile. (There are thermochemical water splitting technologies that exploit partially reducing transition or rare earth oxides at high temperature, then reacting them with steam at a bit lower temperature to make hydrogen. I believe cerium oxides are the current best approach there, although still not competitive.)
- RobotToaster 10mo ago
  I imagine you just need the flask part, the vacuum is rather easy in space.
willis936 10mo ago
Good electrical conductors are also good thermal conductors. It's a fun system challenge to minimize what needs to be hot, but some things will have to get hot. It could be reduced to a photodiode, transistor, and a relay. But how do you get the power to the heater in a compact way?
- aeonik 10mo ago
  Diamond is my favorite exception to this, one of the best thermal conductor and insulators.
  - HPsquared 10mo ago
    Boron nitride too. I guess the thermal vibrations transmit well through a stiff microstructure.
- pfdietz 10mo ago
  One notable exception to this is superconductors. One might naively think that because superconductors have zero electrical resistance, they also have zero thermal resistance. But this is wrong (sorry, Larry Niven)! The superconducting charge carriers (Cooper Pairs) have zero entropy, so they can't carry heat. Thermal conductivity of a superconducting material drops when it becomes superconductive. I believe high Tc superconductors have been used (or at least proposed to be used) as current leads for carrying current into low Tc superconductors from somewhat higher temperature normal conductors.

jstanley 10mo ago

If you have to bring your own vacuum flask, don't you lose half the benefit of doing it in space?

rokkamokka 10mo ago
Isn't the primary benefit the lack of gravity?
- imtringued 10mo ago
  You can reduce metals through vacuum pyrolysis at much lower temperatures without a reducing agent if you have a vacuum. This could make industrial scale processing of steel relatively easy on the moon.
  - pfdietz 10mo ago
    Reducing ferric oxide to magnetite, perhaps, but I think if you tried that with ferrous oxide you'd get iron vapor coming off along with the oxygen. An issue with any high temperature process is things start evaporating. This is part of why carbothermal reduction of aluminum oxide doesn't work: at the required temperature aluminum oxide is volatile. (There are thermochemical water splitting technologies that exploit partially reducing transition or rare earth oxides at high temperature, then reacting them with steam at a bit lower temperature to make hydrogen. I believe cerium oxides are the current best approach there, although still not competitive.)
RobotToaster 10mo ago
I imagine you just need the flask part, the vacuum is rather easy in space.

willis936 10mo ago

Good electrical conductors are also good thermal conductors. It's a fun system challenge to minimize what needs to be hot, but some things will have to get hot. It could be reduced to a photodiode, transistor, and a relay. But how do you get the power to the heater in a compact way?

aeonik 10mo ago
Diamond is my favorite exception to this, one of the best thermal conductor and insulators.
- HPsquared 10mo ago
  Boron nitride too. I guess the thermal vibrations transmit well through a stiff microstructure.
pfdietz 10mo ago
One notable exception to this is superconductors. One might naively think that because superconductors have zero electrical resistance, they also have zero thermal resistance. But this is wrong (sorry, Larry Niven)! The superconducting charge carriers (Cooper Pairs) have zero entropy, so they can't carry heat. Thermal conductivity of a superconducting material drops when it becomes superconductive. I believe high Tc superconductors have been used (or at least proposed to be used) as current leads for carrying current into low Tc superconductors from somewhat higher temperature normal conductors.