It’s very easy to overestimate the difficulty of cooling things in space, unless you actually run the numbers. So please follow along as Scott Manley runs the numbers: <https://www.youtube.com/watch?v=FlQYU3m1e80>.

Basically a Starlink v3 satellite has an estimated power budget of 20kW. Add in the heat absorbed from the environment (both directly from sunlight and reflected off of the Earth) and you’ll find that it must reject about 22kW of heat. That’s a fair amount, but at 65°C it can radiate it all away just using it’s own surface area! No radiator required at all!

Of course the power density of computer racks has been going up over the years. If you want to reach 100kW per satellite then they will need a modest radiator, but nothing extravagant. It would still be smaller than the solar panels, and far smaller than the ones on the ISS. And don’t forget that because radiated heat goes up as the fourth power of temperature, raising the temperature of the system by even a small amount raises the radiation emitted by a lot. If you design the system to run hotter you can minimize the size of the radiator. Most chips these days are designed to max out at 100°C to 110°C without lasting damage, although running them at that temperature 24/7 may reduce their lifespan. There will be some sweet spot in the middle.

And it turns out that a Starlink v3 already has a volume somewhat larger than a 48U rack. You talk about launching 250k satellites in order to have 250k GPUs in orbit, but that’s ridiculous. A real compute swarm will be hundreds or thousands of satellites each equivalent to a whole rack of GPUs.

But you’re not wrong to be skeptical. The economics might not work out even if the cooling is easy enough. It’s just that rejecting the idea takes a lot more than back–of–the–envelope calculations.