[hatthew]

Followup question, wouldn't nearly any cooling solution that works in space also work on the ground? Radiative cooling is the most basic/common cooling solution on the ground, the main challenge is just figuring out how to to move heat from the component to the radiator, which I don't think is solved by simply putting it in space?

[krisoft]

> Radiative cooling is the most basic/common cooling solution on the ground

Thats tricky. I know the heat exchange components are called radiators but most of the heat they give off is by convection not radiation. (At least here on the ground.) I heard 80%-20% rule of thumb.

But you are right in the broad strokes. Cooling is not easier in space. Mostly because you have no convective heat transfer.

[hatthew]

Oh right, that makes sense. So the argument is that comparing a 50C GPU+radiator in a 20C room vs a 50C GPU+radiator in 0K space, the one in space will dissipate more heat via radiation than the one on the ground? As you say, I'd expect that air cooling is much better than EM radiation, but I guess there is some basis for claiming the possibility that cooling in space is somehow better than on the ground, however unlikely.

[Lanzaa]

I think other have already corrected you, but radiative cooling is probably the least common on the ground and the only viable option in space.

I can help explain why. On earth, we are surrounded by stuff. Radiative cooling relies on thermal radiation leaving an object. Crucially, it also requires the object to absorb less thermal radiation than it emits. On earth we are surrounded by stuff, including air, that emits thermal radiation. There is a window of wavelengths, called the atmospheric window[0], that will allow parts of the thermal radiation out into space, rather than returned back. Imagine shining a flashlight on tinted glass, the light will get through depending on the color. If the light gets through, it has escaped. If not, the light is returned and heats up your surroundings again.

Also on earth the other methods (conduction, convection, and phase changes) are more effective. The earth can be used as a very big heat sink. On a spaceship or satellite, you don't have the extra mass to store the energy, so radiative is the only option.

[0] https://en.wikipedia.org/wiki/Atmospheric_window

[ranger207]

Is radiative cooling the most common on Earth? I don't think so. Most terrestial "radiators" actually work with convection, ie moving relatively cold air across hot metal fins, which doesn't work in space.