A radiator that has to run hot to cool anything

You know the noise a laptop makes when the fan kicks in. That is the sound of a chip trying to get rid of its own heat. Without it, it would run red hot and burn out in a few minutes.

In June, SpaceX showed the blueprint for a satellite that will carry one (!) cabinet of AI chips into orbit. Seventy metres across once unfolded, so wider than the largest Boeing 747. It draws a hundred and fifty kilowatts while doing what it is there to do. That is the consumption that feeds a small data centre on the ground.

In a vacuum there is no air, so there is no fan. The heat from the chips can leave in one way only: radiated away as light. Space is cold, true, but that cold does not help, because there is nothing else there to carry the heat off.

Radiating is a slow way to move heat. A panel warmed to around twenty degrees sheds about 633 watts per square metre. The satellite has a hundred and ten of them, both sides. Multiply that out and you get roughly 70 kilowatts. The chips produce 120 on average.

On paper, then, the arithmetic does not add up.

But it does work anyway, because of one detail: radiated heat does not rise with temperature in a straight line, but with the fourth power of it. Double the radiator’s temperature and you do not get twice as much heat dissipation, you get sixteen times. So the panels are not kept at room temperature; they are deliberately driven to fifty, sixty, eighty degrees. The coolant keeps picking the heat off the chips and carrying it out to those scorching panels. The chips stay cool precisely because the radiator is hot.

It is fascinating that this whole mini AI data centre depends on its radiators having to be scalding.

And then comes the financial arithmetic.

Today, putting one kilogram into orbit costs about 1,500 dollars. By the harshest calculation quoted in the video, for a business like this to pay off, that price would have to fall to 20 or 30 dollars. Not half as cheap but fifty times!

And that is not the worst of it. AI chips go out of date every year or two. The one you launch today turns slow the moment a better one ships on Earth, and you cannot replace it, because it is floating five hundred kilometres above you. They will have to keep launching them, just to stop the chips in orbit from turning into junk.

The video also cites Morningstar giving that outcome a seven per cent chance, and the research firm Gartner calling the whole idea peak insanity.

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The video is below, the channel is Farzad. There are more numbers in it that I did not want to retell, and if you find this fascinating, watch the whole thing.