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On Venus, the conditions are really extreme in terms of heat and pressure.

Say we take many layers of rockets' lab heat shield for Electron (which I am not sure what is made of). Could it provide heat protection when it is wrapped around an electrical circuit (as an example) so that circuit could function?

Maybe other types of heat shields could achieve long term maintenance of bearable temperature? I guess they would need to melt themselves, but do you have any estimate?

And yes, I am asking because I was interested by the challenge of NASA to Venus, but just to get a general perspective.

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  • $\begingroup$ I am referring to the time it lies safely on the surface on Venus, not the actual decent. $\endgroup$
    – user2679290
    Feb 29, 2020 at 10:44
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    $\begingroup$ A heat shield designed for reentry is exposed to much higher temperatures than on Venus surface but only for a short time of some minutes and not hours. $\endgroup$
    – Uwe
    Feb 29, 2020 at 11:28
  • $\begingroup$ This is true, but What does this mean for the longterm? $\endgroup$
    – user2679290
    Feb 29, 2020 at 21:10

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The problems with temperature insulation for a situation like Venus, where you are surrounded by very high temperatures on all sides:

  1. Insulation is heavy.

  2. Insulation slows down the gradual spread of heat inwards towards your vulnerable interior, but it cannot stop it.

  3. All power sources, electronics, and other active, useful equipment that would be found in any kind of spacecraft produce heat themselves.

  4. Many power sources, such as nuclear reactors, internal combustion engines, and RTGs put out large amounts of heat as a necessary part of their operation (required by the Laws of Thermodynamics), and moreover they want to put out heat at a low-ish temperature (since in these power sources, useful energy is extracted from a flow of heat from high temperatures to low).

This is not too much of a problem in the vacuum of space; you can go very near the sun by just having a very heat-resistant sunshade and having the rest of your spacecraft in the shade and exposed to the cold darkness. But on Venus, the heat is on every side, and it will gradually leak through the insulation and cook the electronics.

Some potential solutions are:

  • Have some kind of open-loop coolant venting (water would work well), but this will only keep you safe until you run out of it. Heat shielding insulation will make the limited supply of coolant last longer.

  • Make your entire lander / rover out of equipment that can survive being heated to Venus-temperatures. This is difficult: We have plenty of materials that work at those temperatures, but electronics and computers that can survive such conditions are much harder. And obviously a manned mission is then totally impossible.

  • Use a heat pump (like a super-powered air conditioning system) to keep the interior of the spacecraft cool. Heat shielding insulation will reduce the required power for this. However, you are going to need a LOT of power to run this, and because of problem 4, having lots of power on Venus is a bit tricky.

As a sidenote, the kinds of heat shielding that are used for protection of re-entering spacecraft are not really the same as the ones that would be used for insulating a Venus probe.

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    $\begingroup$ As far as #4 goes, the atmosphere of Venus is actually not hugely hotter than the "cold side" temperature of an RTG in vacuum, due to limited radiator area. RTGs will be less efficient on Venus, but still effective as power sources. You could also use the heat to directly run a cooling system, avoiding the losses of thermoelectric conversion. $\endgroup$
    – Christopher James Huff
    Mar 1, 2020 at 13:09
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    $\begingroup$ Are heat-pumped refrigerators workable with high discharge temperatures? $\endgroup$
    – ikrase
    Mar 1, 2020 at 13:42
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    $\begingroup$ As proof that the basic idea is sound, consider that you could just run a Stirling cooler from a Stirling engine. A more realistic cycle would use different temperatures and pressures, but I know of nothing that would make it unworkable. (It would likely be difficult to test on Earth, though.) $\endgroup$
    – Christopher James Huff
    Mar 1, 2020 at 14:24
  • $\begingroup$ @ikrase, The trick to pumping heat across a great temperature difference is to do it in stages. I.e., the "cold" side of one heat pump is used to extract heat from the "hot" side of the next stage. Each different stage can use a different working fluid, appropriate to its nominal "hot" and "cold" temperatures. (Note: I'm not suggesting that it would be practical to build this for a Venus mission. I'm only saying that staging is how it's actually done here on Earth.) $\endgroup$
    – Solomon Slow
    Mar 7, 2022 at 15:11

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