The problem is not that radiators don't work. The problem is the need for liquid cooling. The heat prduced per area in the GPU/CPU is much bigger than the cooling capacity per area of your radiator.
replyEven here on earth, contemporary GPU racks for AI have had to move to liquid cooling because it is the only way to extract enough heat. At 120 kW for 18x 1U servers (GB200 NVL72), the power density is waaay beyond what you can do with air even.
The last time Starcloud was doing the rounds on HN, I estimated that they need to be pumping water at a flow rate of 60 000 liters per second, if you use the numbers in their whitepaper. That's a tenth of the Sacramento river, flowing in space through a network with a million junctions and hoping nothing leaks.
There's a difference between a couple humans (n150W) and say JUST one H200 DGX (8700W).
replyShouldn't the radiators be directly proportional to the area of the solar panels? (Since there's no one munching on food on board.)
replyyes, exactly. they are going to be absolutely huge and add to launch and engineering costs.
replyEvery part does by definition add to launch and engineering costs…
replyThe point is that heat radiation is not the main deal-breaker regarding this project as some comments in this subthread insinuate.
The point is: the power consumption requirements (quote: considering every satellite still has to dump heat and works just fine) for satellite X is not even close to racks of hyperscaler compute.
replyyes. in general as a rule of thumb your radiator size must scale proportionally to your solar panel size, as parent says:
reply> The ISS's solar panels are MUCH smaller than the radiators.