Comment by beAbU | Hacker News Reader

Comment by beAbU | Hacker News Reader

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The starlink satellites have hall effect thrusters, and presumably beefy laser and radio comms systems that will account for a lot of the energy budget. Also, they are sometimes in the earth's shadow, a naive calculation says they have 2x the solar budget they need, in order to charge up batteries for shade-time operations. There is no where near 20kw of compute in a single satellite, and thus no where near 20kw of heat to get rid of.

Furthermore, xAI's colossus supercomputer is specced at 250MW. And this seems to be a number that'll just increase over the coming years with new bigger DCs.

To match this level of performance they will have to launch what, ~15k satellites _per_ equivalent datacentre?

Regarding cooling: you can't just cover the outer surface with pipes. You cant't dissipate the heat, you need to _radiate_ it away. You need to point that surface to the deep dark cold of space. If you point it to the sun, you will heat your satellite. Think a massive "reverse solar panel" that works with infrared. You need surface area, and loads of it.

I'm not saying this is impossible. Obviously elon will prove us all wrong because he's stubborn like that. But there is no way this will ever be economically viable when competing with terrestrial based systems.

The assumption behind "spread the heat over the size of the satellite" is radiative cooling. Admittedly my numbers were a bit off, you need to make the satellite a bit bigger, or use some of your solar panels. A starlink v2 mini has 8m² of area per side, so 16m² total. To dissipate 20kW to space, at a surface temperature of 80°C and emissivity of 0.85, you need about 28m² of space. So you need to increase size a bit, or add 12m² of dedicated radiators. A bit more to deal with the real live complications (the sun exists, the earth is actually warmer than space and covers a significant portion of the sky if you are in leo, etc.).

The actual Starlink V2 Mini is has estimates for solar generation that range up to 35kW. We need a bit more, but not much more.

My numbers are a bit optimistic, but they are in the right order of magnitude. Power and cooling are very achievable in the area of putting one server on one satellite. It's the "putting one DC on one mega satellite" ideas that run into feasability issues, and for inference those aren't needed. The economics are the bigger issue, and launch costs are only moving in one direction

I think you and I are coming to the same conclusion. It's totally viable to have 20kw of compute in a satellite in space. Hell, you can probably get away with 100kW or more with some sort of megasatellite.

I'm pretty sure we'll see this within the next 5 years.

But deploying a megawatt scale DC in space? And then doing that multiple times a year?? I can't see how this is the only solution to this problem. I can't see how that will be the de-facto way of deploying DCs. Not for the next 100 years or more.

The terrestrial based systems getting protested, blocked, and demonized everywhere? Those ones?

For everyone that’s blocked there seems to be another popping up even when the local populace voted against it.

Even then, space is still a harder place to put a satellite than any rural area on the planet.

Plop these satellites on a massive barge in the middle of the ocean with 2x the solar and battery capacity to (to account for day/night cycles) and you have exactly the same solution, only it's multiple orders of magnitude easier to "launch", service and you can actually recycle the deprecated hardware. It will also solve the cooling problem that's associated with space.

The fact that elon's colossus data centre needs to burn jet fuel on site for power tells you everything you need to know about the viability of a solar powered space based solution.

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