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.

Even 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).