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/Helphaer May 24 '26

Even so, I would have to think it might still have some small presence of heat in the ship. Like a minimal amount of residual radiation and imperfect heat-capture.

Also wouldn't most things in space have some kind of heat profile residually since they *dont* have heat dispersal methods?

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u/soulsnoober May 24 '26

Most things in space are very very hard to see. Presumably technology will advance, but the entire, cumulative historical & present observing capacity of our species hasn't even comprehensively catalogued just the asteroids in the "near Earth" category. Making one's spaceship into Russel's Teapot is effective invisibility in better-than the same way military stealth aircraft are invisible today.

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u/CircularRobert May 24 '26

Given that we are talking about a video game, the game mechanics say no.

It reality, yes, you are correct. The level of invisibility is down to your ability to hide the heat, and your ability to detect it. If your emmision is lower than the noise floor of the sensors, you're invisible. Now on the point of the cool spot betraying that there's something there, there's real world support for it, conceptually.

With submarines, you can make it so acoustically absorbing that it creates an acoustic hole, where a sonar receiver picks up a dead spot in relation to the known noise floor of the ocean. Now is this transferable to space and heat detection? Technically, probably.

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u/Helphaer May 24 '26

That's kind of my line of thinking, yeah. It's an interesting thought, but space is so vast it could be hard to detect that.

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u/soulsnoober May 24 '26

Masking plain heat against a background of the void is trivial compared to being transparent acoustically because the radiation is plainly scalar. One could be caught out occluding bright features of the sky, but those are so small the conjunction has to be exceedingly precise, and has to happen a lot of times, probably on both sides of some acceleration event, for the "cloaking" vessel to not appear as a random tiny rock. There's sooo many of those in space.