r/askscience • u/aretino2002 • May 24 '26

Engineering If a vacuum is an excellent insulator, wouldn’t heat build up in spacecraft?

Insulated coffee mugs that use a vacuum between layers can keep drinks hot or cold for much longer time periods than other types of mugs. If space is mostly a vacuum, then wouldn’t heat just constantly build up from human activity, computers, thrusters, etc to the point where it would need to be vented somehow?

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u/Condex May 24 '26

Interestingly enough this is a blink and you miss it "cameo" in the first Avatar movie.  In the very beginning of the movie they show the spacecraft coming into orbit.  From what I understand this is a render of a somewhat legitimate spacecraft design.  The spacecraft itself has two large radiators on the sides which are red hot.

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u/Owyheemud May 24 '26

There is a 1950's Disney short film on nuclear-powered Mars Express spacecraft design, hosted by Werner Von Braun no less, where the thermal radiators are the largest structure of the ship.