[amluto]

This isn’t that big a win. If you put the radiator in the shadow of the solar panels then a good fraction (which depends on the geometry) of the radiated heat from the side facing the panels hits the panels and warms the panels, and the radiated heat from the back of the panels warms the radiator. And the panels themselves are less efficient when they’re warmer.

On the flip side of all this, the Starlink satellites work, and I would expect SpaceX to have some idea what they’re doing. Starlink satellites have largish power systems (smaller than these proposed AI satellites, but not outrageously so). They presumably turn a smaller fraction of their power into low-temperature heat: the ion thrusters and the various transmitters emit a good deal of non-thermal power. A good fraction of Starlink’s electronics way well function at rather higher junction temperatures than 100C. And I imagine that Starlink satellites are economical to operate at an average of much less than 100% power. So I don’t really know what’s going on. It’s plausible that Starlink gets away with a cooling system that’s not so great for a compute satellite.