ISS radiators run on water and ammonia. Think about how much a kg costs to lift to space and you'll see the economics of space data centers fall apart real fast. Plus, if the radiator springs a leak the satellite is scrap.
The point of the Starship program is to drop the cost of a kg going to space significantly - this isn't meant to be launched with rockets that aren't fully reusable.
I don't pretend to understand the thermodynamics of all of this to do an actual calculation, but note that the ISS spends half its time in the shadow of the earth, which these satellites would not do.
The earth is actually a pretty big heat source in space. Solar radiation is a point source, so you can orient parallel to the rays and avoid it. The earth takes up about half the sky and is unavoidable. The earth also radiates infrared, the same as your radiators, so you can't reflect it. Solar light is in the visible spectrum so you can paint your radiators to be reflective in visible wavelengths but emissive in infrared.
Low satellites are still cooler in the Earth's shadow than they would be in unshadowed orbits, but higher orbits are cooler than either. Not where you'd want to put millions of datacenters though.
You would put these in polar orbits so they are always facing the Sun. Basically the longitude would follow the Sun (or the terminator line, whichever you prefer), and the latitude would oscillate from 90°N to 90°S and back every 24 hours.
No. Otherwise how would you power them? We could use nuclear power methods, like we did in the Voyagers for instance. But the press release doesn’t mention that and, for a constellation of satellites around the earth, it would be a terrible idea.
Radiator size scales linearly with power but, crucially, coolant power, pumps, etc do not.
Imagine the capillary/friction losses, the force required, and the energy use(!) required to pump ammonia through a football-field sized radiator panel.
Moving electricity long distance is a lot easier than moving coolant long distances, which puts a soft limit on the reasonable size of the solar array of these satellites. But as long as you stay below that and pick a reasonable orbit it's indeed not too bad, you just have to properly plan for it
It does if you don't turn off the heat source every 30 minutes or so. Since the "datacenters" are targeted at sun synchronous orbits they have 24/7 heat issues. And they convert pretty much all collected energy into heat as well (and some data, but that's negligible). Those GPUs are not magically not generating heat.
Wouldn't the panels themselves need cooling too? The ones on earth generate heat while being in the sun.
There are commercial systems that can use open loop cooling (i.e. spray water) to improve efficiency of the panel by keeping the panel at a optimal temp of ~25C and the more expensive closed loop systems with active cooling recovers additional energy from the heat by circulating water like a solar heater in the panel back.
Twenty-five years after the ISS began operations in low Earth orbit, a new generation of advanced solar cells from Spectrolab, twice as efficient as their predecessors, are supplementing the existing arrays to allow the ISS to continue to operate to 2030 and beyond. Eight new arrays, known as iROSAs (ISS Roll-Out Solar Arrays) are being installed on the ISS in orbit.
The new arrays use multi-junction compound semiconductor solar cells from Spectrolab. These cells cost something like 500 times as much per watt as modern silicon solar cells, and they only produce about 50% more power per unit area. On top of that, the materials that Spectrolab cells are made of are inherently rare. Anyone talking about scaling solar to terawatts has to rely on silicon or maybe perovskite materials (but those are still experimental).
