This is mistaken. In space a radiator can radiate to cold (2.7K) deep space. A thermos on earth cannot. The temperature difference between the inner and outer walls of the thermos is much lower and it’s the temperature difference which determines the rate of cooling.

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pclmulqdq 10 hours ago | parent | next [-]

"Radiate" is exactly what you have to do, and that is extremely slow. You need a huge area to dissipate the amount of power you are talking about.

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fnordpiglet 9 hours ago | parent [-]

Basically you concentrate the heat into a high emissivity high temperature material that’s facing deep space and is shaded. Radiators get dramatically smaller as temperature goes up because radiation scales as T⁴ (Stefan–Boltzmann). There are many cases in space where you need to radiate heat - see Kerbal Space Program

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pclmulqdq 8 hours ago | parent [-]

"High emissivity, high temperature" sounds good on paper, but to create that temperature gradient within your spacecraft the way you want costs a lot of energy. What you actually do is add a shit load of surface area to your spacecraft, give that whole thing a coating that improves its emissivity, and try your hardest to minimize the thermal gradient from the heat source (the hot part) throughout the radiator. Emissivity isn't going past 1 in that equation, and you're going to have a very hard time getting your radiator to be hotter than your heat source.

Note that KSP is a game that fictionalizes a lot of things, and sizes of solar panels and radiators are one of those things.

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WalterBright 7 hours ago | parent | prev [-]

I have a vacuum thermos. I've been unimpressed with its ability to keep coffee hot.