Comment by esseph
9 hours ago
This is such a hypebeast paragraph.
Datacenters in space are a TERRIBLE idea.
Figure out how to get rid of the waste heat and get back to me.
9 hours ago
This is such a hypebeast paragraph.
Datacenters in space are a TERRIBLE idea.
Figure out how to get rid of the waste heat and get back to me.
That's not a new problem that no one has dealt with before. The ISS for instance has its External Active Thermal Control System (EACTS).
It's not so much a matter of whether it's an unsolvable problem but more like, how expensive is it to solve this problem, what are its limitations, and does the project still makes economic sense once you factor all that in?
It's worth noting that the EACTS can at maximum dissipate 70kW of waste heat. And EEACTS (the original heat exchange system) can only dissipate another 14kW.
That is together less than a single AI inference rack.
And to achieve that the EACTS needs 6 radiator ORUs each spanning 23 meters by 11 meters and with a mass of 1100 kg. So that's 1500 square meters and 6 and a half metric tons before you factor in any of the actual refrigerant, pumps, support beams, valve assemblies, rotary joints, or cold side heat exchangers all of which will probably together double the mass you need to put in orbit.
There is no situation where that makes sense.
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Manufacturing in space makes sense (all kinds of techniques are theoretically easier in zero G and hard vacuum).
Mining asteroids, etc makes sense.
Datacenters in space for people on earth? That's just stupid.
> Datacenters in space for people on earth? That's just stupid.
But if completes the vision of ancestors who thought god living in the sky
So "Lord give me a sign from heavens" may obtain a whole new meaning
I'm a total noob on this.
I get that vacuum is a really good insulator, which is why we use it to insulate our drinks bottles. So disposing of the heat is a problem.
Can't we use it, though? Like, I dunno, to take a really stupid example: boil water and run a turbine with the waste heat? Convert some of it back to electricity?
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The ISS consumes roughly 90kW. That’s about *one* modern AI/ML server rack. To do that they need 1000 m^2 of radiator panels (EACTS). So that’s the math: every rack needs another square kilometer of stuff put into orbit. Doesn’t make sense to me.
1000m2 is not a square kilometer (1 square kilometer is 1mil m2)
1000 square meters really isn't that big in space.
And what happens every time a rack (or node) fails? Does someone go out and try to fix it? Do we just "deorbit" it? How many tons per second of crap would we be burning in the upper atmosphere now? What are the consequences of that?
How do the racks (or nodes) talk to eachother? Radios? Lasers?
What about the Kessler Syndrome?
Not a rocket scientist but 100% agree this sounds like a dead end.
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It makes sense to target a higher operating temperature, like 375K. At some point, the energy budget would reach an equilibrium. The Earth constantly absorbs solar energy and also dissipates the heat only by radiative cooling. But the equilibrium temperature of the Earth is still kind of cool.
I guess the trick lies in the operating temperature and the geometry of the satellites.
Asking for a friend (who sucks at thermodynamics:) could you use a heat pump to cool down the cold end more and heat up the hot end much higher? Heat radiation works better the higher the temperature?
Not sure about the effectiveness of a heat pump in this use case.
>Heat radiation works better the higher the temperature?
The power output is proportional to T^4 according to the Stefan-Boltzmann law.
I agree that data centers in space is nuts.
But I think there's solutions to the waste heat issue
https://www.nasa.gov/centers-and-facilities/goddard/engineer...
The distinction is that what they are doing for Webb is trying to dissipate small amounts of heat that would warm up sensors past cryogenic temperatures.
Like on the order of tens or hundreds of watts but -100C.
Dissipating heat for an AI datacenter is a different game. A single AI inference or training rack is going to be putting out somewhere around 100kW of waste heat. Temps don't have to be cryogenic but it's the difference between chiselling a marble or jade statue and excavating a quarry.
That's a solution for minuscule amounts of heat that nevertheless disturb extremely sensitive scientific experiments. Using gold, no less. This does not scale to a crapton of GPU waste heat.
Just have to size radiators correctly. Not a physics problem. Just an economic one.
Main physics problem is actually that the math works better at higher GPU temps for efficiency reasons and that might have reliability trade off.
Anything is possible here, it's just there's no goddamn reason to do any of this. You're giving up the easiest means of cooling for no benefit and you add other big downsides.
It's scifi nonsense for no purpose other than to sound cool.
It's about creating a flywheel for scale.
Getting better at creating and erecting solar panels & AI datacenters on earth is all well and good, but it doesn't advance SpaceX or humanity very much. At lot of the bottlenecks there are around moving physical mass and paperwork.
Whereas combining SpaceX & xAI together means the margins for AI are used to force the economies of scale which drives the manufacturing efficiencies needed to drive down launch etc.
Which opens up new markets like Mars etc.
It is also pushing their competitive advantage. It leaves a massive moat which makes it very hard for competitors. If xAI ends up with a lower cost of capital (big if - like Amazon this might take 20 years horizon to realize) but it would give them a massive moat to be vertically integrated. OpenAI and others would be priced out.
If xAI wants to double AI capacity then it's a purely an automation of manufacturing problem which plays to Elons strengths (Tesla & automation). For anyone on earth doubling capacity means working with electricity restrictions, licensing, bureaucracy, etc. For example all turbines needed for electricity plants are sold years in advance. You can't get a new thermal plant built & online within 5 years even if you had infinite money as turbines are highly complex and just not available.
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