My napkin is with Starcloud https://news.ycombinator.com/item?id=43190778 , ie. one Starship $10M launch - 10 000 GPU datacenter into LEO with energy and cooling. I missed there batteries for the half the time being in the Earth shadow (as originally i calculated that for crypto where you can have half the time off which isn't the case for the regular datacenter) and panels to charge them, that adds 10kg for 1 KWH, and thus it will get down to about 5000 GPU for the same weight and launch cost.
Paradoxically the datacenter in LEO is cheaper than on the ground, and have bunch of other benefits like for example physical security.
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