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It’s not an unsolved physics problem. Every satellite in space has to deal with it and even the ISS deals with it by having massive radiator arrays that face pe

by nkrisc 3mo ago

It’s not an unsolved physics problem. Every satellite in space has to deal with it and even the ISS deals with it by having massive radiator arrays that face perpendicular to the sun. The problem with data centers in space is one of materials science and engineering: how to make radiators large enough and effective enough to cool it while also being economically feasible, both in terms of construction and getting them up there in the first place. We can make a space data center right now. It would just be terrible and expensive.

xienze 3mo ago
I think it's not necessarily about being the cheapest option, but a more politically acceptable one. I don't think you're going to get people protesting a data center in space considering it won't be next to their house, won't use water, and won't lead to increased electricity rates. I could see companies paying a premium to keep the political heat associated with traditional data centers off their backs.
kibwen 3mo ago
The physics problem regarding radiator arrays isn't unsolved, but it's not a problem that scales up gracefully. Small-scale radiators could get by via passive cooling, but large-scale radiators need active cooling, and now you need fluid, pipes, and pumps that all represent additional launch mass and points of failure (and the pumps are generating heat of their own, so now you need more radiators...).
- AnthonyMouse 3mo ago
  Doesn't active cooling provide counterbalancing options to improve efficiency though? For example, use multi-stage heat pumps with different refrigerants so that you can make the hot side very hot and thereby need less mass for radiators.
- aeternum 3mo ago
  Thermal dissipation scales quartically with T, that's about as graceful as you can get from a physics POV, very few things scale at that rate. COTs GPUs throttle at about 90-100C but that's because they have plastic parts and solder that melts. Those are relatively easy to eliminate. We haven't tried much to scale up operating temp.
  - rcxdude 3mo ago
    Apple tried the damnedest at that during their intel era. Silicon gets exponentially leakier at higher temperatures, and that will outpace quadratic growth easily. (Electronics that works at 200C do exist, but they're not gonna meet a modern smartphone's specs, let alone a datacenter)
    - aeternum 3mo ago
      >Apple tried the damnedest at that during their intel era. The story I heard was intel failed to deliver on die shrinks that were supposed to increase thermal efficiency. The fan also had poor routing and basically did nothing. Apple was clearly not at the top of their game for that design, nor would you expect them to be as the decision was likely already made to move to apple silicon.
- nkrisc 3mo ago
  So what’s the unsolved physics problem? Everything you’re describing are engineering challenges.
croes 3mo ago
Nobody said space data centers are impossible, it’s just wasteful and ineffective.
- cucumber3732842 3mo ago
  Right, but nobody's sure just how wasteful. And at these scales small factors make or break things. That's why it's hard to predict who's bullshitting. A fairly small unforeseen factor here and there adds up to wild financial success or failure over the course of an entire project.
  - hcknwscommenter 3mo ago
    I think that's an incorrect way of looking at it. A small unforeseen factor is almost always going to be a negative factor, not an unforeseen benefit. Space is a hostile and unforgiving environment without an easy way to bring things back, fix stuff, and/or re-deploy. A small mistake on the engineering, planning and/or implementation is likely to sink the whole thing worse than the napkin math suggests is almost certain failure anyway. Similarly, there are few ways to "get it right" and many ways to fail.
vlovich123 3mo ago
The maximum heat rejection capacity of the ISS is 126Kw. Musk’s proposal is to put 1 rack per satellite drawing 150kw using 110 m^2 of radiators (1/4th that of the ISS). The only way to do that is by running the satellite at 71-100C which is a problem for the chips to actually run. So the open questions are: * can they actually dump the heat and can they have the racks running so hot for so long * is it economical to in one year replace all the capacity you launched 5 years ago (you save up to 0.5B in electricity costs over that time frame but that doesn’t seem like a lot for having to replace that much capacity buildup)? And given they’re running racks way hotter than has been validated on earth, will those chips end up lasting 5 years (including space radiation). Pretending like it’s a solved problem is neat but I’m not saying sure it’ll be so easy.
- roryirvine 3mo ago
  Those temperatures aren't necessarily a problem for the chips (there are some minor design changes needed, so it's more a question of having enough volume to justify doing it). The real issue is that this is yet another thing you could do better on earth. In other words, run fully lights-out datacentres that no humans will access during normal operation - this allows you create more extreme temperature gradients and to replace the atmosphere with CO2 (or even He2), both of which will make your cooling solution much more efficient as well as increasing rack density and perhaps even taking the place of a fire suppression system. The reason that no-one's actually doing that at scale is that it's currently significantly more expensive than traditional datacentre designs. And yet, that's still much less expensive than boosting racks into space and then letting them burn up in the atmosphere five years later.
- phs318u 3mo ago
  It’s as solved as FSD.
- krcz 3mo ago
  Wouldn't it be possible to use heat pumps, making radiators 100C or hotter while running GPUs much below that?
  - 3mo ago
Eddy_Viscosity2 3mo ago
> It’s not an unsolved physics problem. Every satellite in space has to deal with it and even the ISS deals with it by having massive radiator arrays that face perpendicular to the sun. The problem is not solved for something of this scale, I think its solvable, but no has done anything at the size these would have to be. And if the physics and engineering can be made to work, they are unlikely to be solved AND ALSO be economical. It's classic type problem where the choices are: - economical - in-space - big Now pick two. There is also the unsolved problem that the radiators would be absolutely massive in area. Making damage from flying objects, meteorites, space jump, close to 100% likely over any reasonable life span. Repairs would be expensive AF. Again economics is the driver of why this is dumb.

by nkrisc 3mo ago

xienze 3mo ago

I think it's not necessarily about being the cheapest option, but a more politically acceptable one. I don't think you're going to get people protesting a data center in space considering it won't be next to their house, won't use water, and won't lead to increased electricity rates. I could see companies paying a premium to keep the political heat associated with traditional data centers off their backs.

kibwen 3mo ago

The physics problem regarding radiator arrays isn't unsolved, but it's not a problem that scales up gracefully. Small-scale radiators could get by via passive cooling, but large-scale radiators need active cooling, and now you need fluid, pipes, and pumps that all represent additional launch mass and points of failure (and the pumps are generating heat of their own, so now you need more radiators...).

AnthonyMouse 3mo ago
Doesn't active cooling provide counterbalancing options to improve efficiency though? For example, use multi-stage heat pumps with different refrigerants so that you can make the hot side very hot and thereby need less mass for radiators.
aeternum 3mo ago
Thermal dissipation scales quartically with T, that's about as graceful as you can get from a physics POV, very few things scale at that rate. COTs GPUs throttle at about 90-100C but that's because they have plastic parts and solder that melts. Those are relatively easy to eliminate. We haven't tried much to scale up operating temp.
- rcxdude 3mo ago
  Apple tried the damnedest at that during their intel era. Silicon gets exponentially leakier at higher temperatures, and that will outpace quadratic growth easily. (Electronics that works at 200C do exist, but they're not gonna meet a modern smartphone's specs, let alone a datacenter)
  - aeternum 3mo ago
    >Apple tried the damnedest at that during their intel era. The story I heard was intel failed to deliver on die shrinks that were supposed to increase thermal efficiency. The fan also had poor routing and basically did nothing. Apple was clearly not at the top of their game for that design, nor would you expect them to be as the decision was likely already made to move to apple silicon.
nkrisc 3mo ago
So what’s the unsolved physics problem? Everything you’re describing are engineering challenges.

croes 3mo ago

Nobody said space data centers are impossible, it’s just wasteful and ineffective.

cucumber3732842 3mo ago
Right, but nobody's sure just how wasteful. And at these scales small factors make or break things. That's why it's hard to predict who's bullshitting. A fairly small unforeseen factor here and there adds up to wild financial success or failure over the course of an entire project.
- hcknwscommenter 3mo ago
  I think that's an incorrect way of looking at it. A small unforeseen factor is almost always going to be a negative factor, not an unforeseen benefit. Space is a hostile and unforgiving environment without an easy way to bring things back, fix stuff, and/or re-deploy. A small mistake on the engineering, planning and/or implementation is likely to sink the whole thing worse than the napkin math suggests is almost certain failure anyway. Similarly, there are few ways to "get it right" and many ways to fail.

vlovich123 3mo ago

The maximum heat rejection capacity of the ISS is 126Kw. Musk’s proposal is to put 1 rack per satellite drawing 150kw using 110 m^2 of radiators (1/4th that of the ISS). The only way to do that is by running the satellite at 71-100C which is a problem for the chips to actually run. So the open questions are: * can they actually dump the heat and can they have the racks running so hot for so long * is it economical to in one year replace all the capacity you launched 5 years ago (you save up to 0.5B in electricity costs over that time frame but that doesn’t seem like a lot for having to replace that much capacity buildup)? And given they’re running racks way hotter than has been validated on earth, will those chips end up lasting 5 years (including space radiation). Pretending like it’s a solved problem is neat but I’m not saying sure it’ll be so easy.

roryirvine 3mo ago
Those temperatures aren't necessarily a problem for the chips (there are some minor design changes needed, so it's more a question of having enough volume to justify doing it). The real issue is that this is yet another thing you could do better on earth. In other words, run fully lights-out datacentres that no humans will access during normal operation - this allows you create more extreme temperature gradients and to replace the atmosphere with CO2 (or even He2), both of which will make your cooling solution much more efficient as well as increasing rack density and perhaps even taking the place of a fire suppression system. The reason that no-one's actually doing that at scale is that it's currently significantly more expensive than traditional datacentre designs. And yet, that's still much less expensive than boosting racks into space and then letting them burn up in the atmosphere five years later.
phs318u 3mo ago
It’s as solved as FSD.
krcz 3mo ago
Wouldn't it be possible to use heat pumps, making radiators 100C or hotter while running GPUs much below that?
- 3mo ago

Eddy_Viscosity2 3mo ago

> It’s not an unsolved physics problem. Every satellite in space has to deal with it and even the ISS deals with it by having massive radiator arrays that face perpendicular to the sun. The problem is not solved for something of this scale, I think its solvable, but no has done anything at the size these would have to be. And if the physics and engineering can be made to work, they are unlikely to be solved AND ALSO be economical. It's classic type problem where the choices are: - economical - in-space - big Now pick two. There is also the unsolved problem that the radiators would be absolutely massive in area. Making damage from flying objects, meteorites, space jump, close to 100% likely over any reasonable life span. Repairs would be expensive AF. Again economics is the driver of why this is dumb.