[fnordpiglet]

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

[pclmulqdq]

"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.

[fnordpiglet]

I’m not sure I understand why creating the gradient is hard - use a phase transitioning heat pump to a high surface area radiator. The radiator doesn’t have to be hotter than the heat source the radiator just has to be hot, but given the fact we are talking about a space data center, you can certainly use the heat pump to make the radiator much hotter than any single GPU, and even use the energy from the heat cycle to power the pumps, but I imagine such a data center the power draw of the heat pump would be tiny compared to the GPUs.

To be clear I’m not advocating KSP as a reality simulator, or that data centers in space isn’t totally bonkers. However the reality is the hotter the radiator the smaller the surface area for pure radiance dissipation of heat.