Thread

1. zactato · 1790267254 · focus · HN ↗

   How are they solving the heat dissipation issues?

   1. lopsotronic · 1790268994 · focus · HN ↗

      For real. It's an enormous problem solved only with 1) sheer scale, and 2) Science Fiction.

      Both of those are expensive as hell, by the way.

      Cooling via radiation follows Stefan–Boltzmann: P = εσAT⁴. Let's assume a good surface (emissivity ~0.9) at 300 K (27 °C) at 400 W per square meter per side. A flat panel radiating from both faces into deep space gets 800 W/m, not including the losses from, say, the Sun, or from IR coming off the Earth. Now, input power. Sunlight in orbit ~1,360 W/m², assume ~22% cell efficiency, we got 300 W/m². So each 1 MW compute, 3,300 m² of solar panel and minimum 1,200–1,500 m² of radiator.

      In case ya didn't know - 1 MW is tiny from a present-day-datacenter perspective. It's like 8 racks. So we're talking orbital megastructures here, many many many square kilometers, and this is with all the best case assumptions, and magic radiator panels that never see the sun, or the earth, or the moon.

      This is just the basic numbers here, by the way. There's a garbage truck full of other unsolvable problems if you poke your head in there.

      Aside from the "Avoid Regulations" aspect, and the "Everything That Burns Deorbiting is Depreciation" aka "The Starlink Trick", I'm not sure what the hell the draw is.

      1. tintor · 1790283931 · focus · HN ↗

         Is it possible for one side of panel to be used for solar power and other side for radiating heat?

         1. lopsotronic · 1790619582 · focus · HN ↗

            Radiative coolers also can't be facing the Earth, or it turds up the efficiency by (up to) half. Rotate the whole rigamarole in your head, and you see the conflicting goals when it comes to where to point the thing.

            Also also, how do you get the heat out there, to the panel? You are talking a lot of plumbing, and a lot of working fluid. As mentioned, ISS's two external cooling loops hold about 540 kg of ammonia combined to dump 70 kW of heat, so at the megawatt scale thousands and tens of thousands of kg of working fluid. I know, new heat exchanger, lots of people have brought up "Magic Heat Exchanger Technology X", but no one's given me a cite to at least lay down the fundamentals on how these things manage to bang all over the Carnot numbers.

            I'm no downer on space solar. It's probably the long term solution for humanity's energy needs - an equatorial band on the Moon, or even Mercury, would give us more power than we could ever reasonably use. But presenting it as the fix for the data center problem . . . I'm sorry, it sounds like people chasing other people's money. Which is what got us into this mess in the first place.

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