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Data centers in space makes no sense

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Re: Data centers in space makes no sense

#451

Post by adastra22 »

TheDong wrote: post #410
elamje wrote: post #353

I was talking to someone about this the other day. I was part of a team at NASA that developed a cooling system for the ISS and this whole premise makes no sense to me. 1. Getting things to space is incredibly expensive 2. Ingress/egress are almost always a major bottleneck - how is bandwidth cheaper in space? 3. Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire t…

> Would love for someone to make the case for why it actually makes total sense, because it’s really hard to see for me! Elon musk has a history of making improbable-sounding promises (buy a tesla now, by 2018 it will be a self-driving robotaxi earning money while you sleep, humanoid robots, hyperloops). The majority of these promises have sounded cool enough to enough people that the stock associated with him (TSLA)…

The story here is even simpler. SpaceX is going public this year. Elon made a monumentally shitty investment in Twitter and then poured a stupid amount of money into xAI at the peak of the cycle. By having SpaceX buy xAI, he gets to swap worthless shares in that company for more SpaceX liquidity. Simple as that.

Re: Data centers in space makes no sense

#452

Post by adastra22 »

philipwhiuk wrote: post #366
elamje wrote: post #353

I was talking to someone about this the other day. I was part of a team at NASA that developed a cooling system for the ISS and this whole premise makes no sense to me. 1. Getting things to space is incredibly expensive 2. Ingress/egress are almost always a major bottleneck - how is bandwidth cheaper in space? 3. Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire t…

> Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire teams at NASA dedicated to special hardware for this. They don't do RAD hardening on chips these days, they just accept error and use redundant CPUs.

You are confidently incorrect. Even Starlink uses rad-hardened CPUs. Redundant error correction is only really an option on launch hardware that only spends minutes in space.

Note that on modern hardware cosmic rays permanently disable circuits, not mere bitflips.

Re: Data centers in space makes no sense

#453

Post by pclmulqdq »

phendrenad2 wrote: post #383
beloch wrote: post #115

I would not assume cooling has been worked out. Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot. A satellite is, if nothing else, a fantastic thermos. A data center in space would necessarily rely completely on cooling by radiation, unlike a terrestrial data center that can make use of convection and conduction. You can't just pipe heat out into the atmosphere or build…

I think people underestimate how quickly heat radiates to space. A rock in orbit around Earth will experience 250F/125C on the side facing the Sun, and -173C/-280F on the other side. The ability to rotate an insulating shield toward the sun means you're always radiating.

I think you may be overestimating how quickly this happens and underestimating how much surface area that rock has. Given no atmosphere, the fact that the rock with 1/4 the radius of Earth has a temperature differential of only 300C between the hot side and the cold side, there's not a lot of radiation happening.

In deep space (no incident power) you need roughly 2000 sq meters of surface area per megawatt if you want to keep it at 40C. That would mean your 100 MW deep space datacenter (a small datacenter by AI standards) needs 200000 sq meters of surface area to dissipate your heat. That is a flat panel that has a side length of 300 meters (you radiate on both sides).

Unfortunately, you also need to get that power from the sun, and that will take a square with a 500 meter side length. That solar panel is only about 30% efficient, so it needs a heatsink for the 70% of incident power that becomes heat. That heatsink is another radiator. It turns out, we need to radiate a total of ~350 MW of heat to compute with 100 MW, giving a total heatsink side length of a bit under 600 meters.

All in, separate from the computers and assuming no losses from there, you need a 500x500 meter solar panel and a 600x600 meter radiator just for power and heat management on a relatively small compute cluster.

This sounds small compared to things built on Earth, but it's huge compared to anything that has been sent to space before. The ISS is about 100 meters across and about 30 meters wide for comparison.

Re: Data centers in space makes no sense

#454

Post by munchler »

snewman wrote: post #185
bs7280 wrote: post #163

As a thought experiment, if humanity wanted to go all in on trying to move industrial processes and data centers off planet, would it make more sense to do so on the moon? The moon has: - Some water - Some materials that can be used to manufacture crude things (like heat sinks?) - a ton of area to brute force the heat sink problem - a surface to burry the data centers under to solve the radiation problem - close enou…

Water on the moon is limited and difficult to collect, it wouldn't make sense to use it for industrial purposes. It's a very challenging thermal environment (baking during the day, freezing at night). But perhaps worst of all, every month there's a 14-day period with no solar power. Overall seems worse than low-earth orbit.

> every month there's a 14-day period with no solar power

So it's dark 50% of the time on the moon... just like here on Earth.

Re: Data centers in space makes no sense

#455

Post by adastra22 »

notepad0x90 wrote: post #444

Two reasons why it makes sense (really really good reasons): 1) Water scarcity and energy scarcity here on earth 2) It will drive down launch costs and promotes investment in orbital facilities and launch capabilities. those two reasons alone are enough.

What does water scarcity have to do with anything? Data centers don't use water. They slightly heat it, and then it flows back out to whatever it would have done anyway.

Re: Data centers in space makes no sense

#456

Post by m463 »

beloch wrote: post #115

I would not assume cooling has been worked out. Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot. A satellite is, if nothing else, a fantastic thermos. A data center in space would necessarily rely completely on cooling by radiation, unlike a terrestrial data center that can make use of convection and conduction. You can't just pipe heat out into the atmosphere or build…

I used to really enjoy musk's talks when he was spooling up tesla. He was an engineer and obviously the world is missing what engineers see clearly.

But now looking back and accounting for the claims he made there's a pattern.

I saw this article:

https://www.wired.com/story/theres-a-very-simple-pattern-to-...

that said... he did jumpstart the EV industry. He has put up satellites every week for years. He is still a net benefit to all of us.

Re: Data centers in space makes no sense

#457

Post by adastra22 »

yazaddaruvala wrote: post #428

I’m surprised everyone is worried about heat dissipation. Datacenters in space is ambiguous enough to mean on lunar soil which provides plenty of heat dissipation using geothermal heat pumps. Similarly mass to orbit is also less problematic if silicon factories (including the refineries) are built on lunar soil as well.

They have filed actual plans with the FCC for their satellite constellation. They are not talking about lunar data centers.

Re: Data centers in space makes no sense

#458

Post by pclmulqdq »

marcosdumay wrote: post #325
aunty_helen wrote: post #127

Earlier quoted context omitted.

The equation has a ^4 to the temperature. If you raise the temperature of your radiator by ~50 degrees you double its emission capacity. This is well within the range of specialised phase change compressors, aka fancy air conditioning pumps. Next up in the equation is surface emissivity which we’ve got a lot of experience in the automotive sector. And finally surface area, once again, getting quite good here with nan…

> aka fancy air conditioning pumps Yeah, pumps, tubes, and fluids are some of the worst things to add to a satellite. It's probably cheaper to use more radiators. Maybe it's possible to make something economical with Peltier elements. But it's still not even a budget problem yet, it's not plainly not viable. > getting quite good here with nanotechnology Small features and fractal surfaces are useless here.

Peltiers and heat pipes don't remove heat, they just move it. You still need the radiator.

Re: Data centers in space makes no sense

#459

Post by test6554 »

beloch wrote: post #115

I would not assume cooling has been worked out. Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot. A satellite is, if nothing else, a fantastic thermos. A data center in space would necessarily rely completely on cooling by radiation, unlike a terrestrial data center that can make use of convection and conduction. You can't just pipe heat out into the atmosphere or build…

AI sovereignty, not AI efficiency. Redesign AI chips with lower power density and higher thermal tolerances and you get more efficient radiation with some sacrifice in compute power. But you are outside the jurisdiction of every country.

Then you get people paying much more money to use less-tightly-moderated space-based AI rather than heavily moderated AI.

Re: Data centers in space makes no sense

#460

Post by adastra22 »

innis226 wrote: post #421
mrandish wrote: post #313

> Ground-based solar panels have been getting more cost effective for decades and show no sign of slowing down. I'm no expert on solar but I thought there was some upper limit on how much power ground-based solar panels can generate per area based on how much energy gets through the atmosphere all the way to ground - and that panel efficiency was approaching that limit. However, I don't doubt ground-based panels can…

People are gettingtoo hung up on the radiator math and completely missing the massive input advantage of AM0 versus AM1.5. On Earth you get around 1,000 Watts/m^2 (ideal), but in realtiy shave off 20–25% because of clouds and night time. In a sun-synchronous orbit, you’re pulling close to 1300 W/m^2, and that's 24x7. That is easily a 5x to 6x energy yield advantage per square meter of panel per day, and when you have…

You do not solve a problem that is many orders of magnitude more difficult with a mere 5x to 6x efficiency gain.
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