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Comment by curtis | Hacker News Reader

Electronics aren't the only problem for a Venus probe. You also need some way to power the thing. One interesting possibility is that lithium will combust in a carbon dioxide atmosphere, and it is also, conveniently, liquid at Venus surface temperature.

http://www.bbc.com/future/story/20160705-the-toughest-spaces...

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Idea: put a good insulator under the surface of the probe to keep as much of it as cool as possible (first making sure it cools off in space). Ship it with a thermoelectric generator. I'm not sure how much useful power you'd get from the spacy-cool - Venus hell temperature gradient, so maybe it's a stupid idea.

> first making sure it cools off in space

Heat dissipation is actually a gigantic problem in space: you can only radiate heat away (and try to reflectively shield against the sun) since you're in hard vacuum which is a fantastic insulator.

Basically, you need a sun-facing shield that is perfectly reflective, and diamond fins with a perfectly black surface coating, forever in its shadow.

An effective radiator is an equally effective absorber, so management of light and shadow is critical.

But it's still sort of moot when you consider atmospheric friction on the way down.

You're not going to get much power out of the gradient. Even if you cooled an object in space to near absolute zero, space probes must necessarily be low mass to get into orbit from Earth. The low mass of the whole object, and the low heat capacity of most space-grade building materials combines to make it a really awful cold sink. You would essentially need to harvest water and ammonia from somewhere outside of a gravity well, use your radiator to cool it off as much as possible, and then drop it in the heat well. That's an awful lot of trouble to go to for the amount of power you will then get out of it.

What would be the total energy required to heat the probe from space cold to venus hot?

That's your theoretical maximum output. Assuming the probe doesn't heat up during entry.

The old style thermoelectric generators (like used for Voyager 1 & 2) were able to operate at high enough temperature that they could dump heat at Venus ambient temperature and still generate power.

Park a satellite in orbit and beam down energy.

The atmosphere of Venus is remarkably opaque to many forms of beamed energy.

Create a permanent "wide tornado"

To be fair, lithium will react quite fast with our atmosphere as well, so we are pretty good at keeping atmosphere out of batteries. 460C temperatures on the other hand is a challenge.

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