undefined

points

by ben_w5 hours ago |

comments

by hedora3 hours ago|

[-]

I think there are at least a few problems with the math’s assumptions:

1) Don’t the radiators need to have more surface area than the solar? (Unless the chips run very hot.)

2) The datacenter will have the pesky earth between it and the sun some fraction of the time, and have to either shut down or run off batteries. ~50%, assuming LEO, right? If you leave LEO, then the latency sucks, so they’re training-only clusters. At 50% the solar doubles and you need 370 megawatt hours per hour of darkness, or you run the machines 50% of the time, rebooting for each orbit. If you make the orbit shorter (so you can have smaller batteries), then they wear out faster. The batteries also emit heat. Plus, you need to double the solar so they charge while the workload is running.

3) How do they cope with cosmic rays? The standard approach is still to duplicate or triplicate all computation, or use larger/slower processes, right?

The obvious answer to each question makes the engineering design at least twice as dumb, and they stack. There are many other problems like these.

by sobellian1 hours ago|

parent|

[-]

The radiators are what need to be very hot. IIRC it works out to, order of magnitude, a similar area to the solar panels. These satellites would likely be placed in SSO, a polar orbit that precesses at the same rate that the Earth orbits the sun. So the fraction of time they see the sun would be very high. Cosmic rays are a little bit of an unknown, we don't know exactly how a commercial GPU running an LLM deals with cosmic ray radiation. I think the intuition is that it would be very little because a single bit flip in that vast array of matrix math and many times its result might not actually change any activations anyway.

I think the big problem with the idea is that GPUs have a failure rate and even if they didn't, they become obsolete. Most orbital DC plans are really more like flying server racks with no servicing in orbit. So when the GPUs die the satellite is a flying brick. All the power equipment, all the thermal equipment, all the comms equipment now depreciates at the same rate as GPUs. Very different economics from terrestrial DCs. And that's all assuming that you can launch everything up there quite efficiently. And the satellites take time to engineer but DCs are a more known quantity.