5 ms·

Cooling in Space

35 points by LolWolf 4mo ago

mike_hearn 4mo ago
All the comments are negative so I'll play the devil's advocate. Here's the steelman case for SpaceX orbital datacenters. # EARTH IS FULL It sounds ridiculous but the ability to build AI datacenters on Earth is nearly exhausted. The options are: • USA, Australia. The electricity infrastructure has already bottlenecked and some datacenters like Colossus are being forced to build their own power plants, but that's also bottlenecked on gas turbine capacity. Hacks like recycling jet turbines only squeeze a bit more out. Terrestrial solar can't be used to escape this problem because you need the clusters to run at night too. • Europe. Deindustrialized, EU Commission is anti AI, very expensive power, grid also bottlenecked. Forget it. • Middle East. Had some datacenters until they got blown up by Iran. • China. Got power but bottlenecked by trade sanctions. Might well do a big buildout when Ascend starts to be competitive, but Chinese demand is likely to absorb it. • Latin America, Africa, south-east Asia, etc: bottlenecked by political stability, not pro-business enough, etc. In space you don't need gas turbines because solar can be 24/7, political risks aren't there, you aren't bottlenecked by grid capacity. Even if it costs more to put stuff in space that doesn't matter if space is the only place you can put stuff. # INFERENCE NOT TRAINING Trying to do backpropagation in space would be a bad idea. You need extreme locality in a single physical location for networking reasons. But a lot of modern AI load including training load is just inference, which only requires small pods not entire clusters, and bandwidth needs in/out aren't that high. Inferencing can fit on a satellite. Space radiation isn't necessarily a problem. Bit flips can be tolerate to quite a high degree for inferencing because models can recover from corruptions in the activation stream or even some bad tokens. # COOLING As the article lays out this isn't necessarily the problem people are assuming. Also there are candidate designs from decades ago for ferrofluid droplet radiators. These might be overkill but can in theory radiate huge amounts of heat without needing to launch big radiators. # COST Unlike terrestrial data centers which are always bespoke projects, inferencing satellites can be mass manufactured. SpaceX and Elon in general are good at setting up mass production lines, and it seems apparent that SpaceX has no intention of throwing very high margin Nvidia hardware into orbit. The plan is to use Tesla's AI chips i.e. SpaceX could acquire accelerators at cost. This changes the cost calculations quite a bit. Although these accelerators might not be useful for training or research, most training workloads would stay on Earth so that doesn't matter (the inferencing loads moved into space would free up terrestrial hardware for training anyway). The real wild card is if there's enough demand for a 'good enough' model that it's predicted to last the lifetime of the satellite. In that case the weights could be fabbed directly into the chips like Taalas does, and so the energy consumption would be far lower. # BUSINESS CASE It's possible that datacenter construction goes the same way as nuclear and becomes impossibly expensive here on Earth. If so then SpaceX can end up with a near monopoly on new inferencing capacity, making them the gateway to AI and the new Nvidia. What's especially confounding is that the mere existence of orbital inferencing might actually create that outcome, because politicians would find it much easier to squash datacenter / power projects to please activists if there is a genuine alternative! Note: I'm not invested in SpaceX.
baq 4mo ago
See also https://andrewmccalip.com/space-datacenters https://andrewmccalip.com/space-datacenters with some models and numbers you can play with.
tristanj 4mo ago
Space data centers are physically possible but don't make financial sense. The total cost of an orbital datacenter over five years is at least 2–3x that of a terrestrial one. But those economics don't matter to SpaceX, because the main purpose of its orbital data centers is to create a use case for Starship. Starship has to fly frequently to iron out the kinks, encounter and fix rare (1/1000) failure situations, and optimize the launch cadence which pushes launch costs down. Plus Starship needs to fly a lot before it's ready for crewed flight. The long-term goal is a Starship optimized for crewed interplanetary travel. Orbital data centers are a payload that bring in some revenue, and provide a reason to launch constantly. It's the same thing they did with Starlink to make Falcon 9 as reliable and rapidly reusable as it is.
- croes 4mo ago
  My guess is: it just sounds cool. Like the cybertruck
- pavlov 4mo ago
  2-3x sounds like a very low estimate. There’s so much data center capacity being built all over the Earth. Thousands of large projects across US / China / Europe / Middle East. It would be astonishing if something that’s never been done before could be so cost-competitive immediately. Starlink wasn’t the first time LEO communications constellations were attempted. Multiple 1990s projects did it (Iridium, GlobalStar…) and went bankrupt. It took 30 years to make the concept work. SpaceX investors seem to be assuming the space data center business will be immediately viable.
  - tristanj 4mo ago
    SemiAnalysis' report on orbital data centers estimated 4x terrestrial costs in 2026, then parity around ~2040. https://newsletter.semianalysis.com/p/to-boldly-go-the-case-for-space-datacenters https://newsletter.semianalysis.com/p/to-boldly-go-the-case-...
    - pavlov 4mo ago
      Based on very specific assumptions: “…the world in which AI demand is so overwhelming as to exceed the already formidable datacenter capacity additions” — but also this same world is one where GPU chip supply is abundant, there just isn’t enough data centers to put them in. This does not seem like the likeliest scenario to me.
amelius 4mo ago
See also: https://www.youtube.com/watch?v=FlQYU3m1e80 https://www.youtube.com/watch?v=FlQYU3m1e80
- tristanj 4mo ago
  And also: https://www.youtube.com/watch?v=JAcR7kqOb3o https://www.youtube.com/watch?v=JAcR7kqOb3o
echoangle 4mo ago
I still don’t see what the advantage is. Of course it’s physically possible to build a datacenter in space, but I can’t imagine land prices being that high that the same data center on earth wouldn’t be cheaper. Even just due to launch costs and the more sophisticated equipment needed for space.
- XorNot 4mo ago
  The real issue is that the power situation in LEO is still actually terrible! Your solar is a little more performant, but you're plunged into hard shade every 45 minutes.
  - athrowaway3z 4mo ago
    I think calling solar a little more performant is underselling it. Once you have LEO getting to a better orbit costs relatively little. Getting from LEO to the moon is only like 30% more than getting from ground to LEO.
    - curiousObject 4mo ago
      True, but lifting the fuel to power that “small” orbital boost is unintuitively expensive (Refer to the tyranny of the “Rocket Equation”)
  - adrian_b 4mo ago
    There exist the so-called Sun-synchronous orbits, which exploit the precession effect caused by the fact that the Earth is not a sphere, to pass over the same point of the Earth at the same local hour. On a small subset of these Sun-synchronous orbits the Sun is always visible from the satellite (i.e. on the subset of orbits whose plane is approximately perpendicular on the radius that connects the Sun to the Earth). Without the precession effect, a satellite that sees the Sun for an entire day would lose this property after a few days, because of the rotation of the Earth around the Sun, which alters the direction in space of the radius from the Sun to the Earth. However, the number of slots that are available in Sun-synchronous orbits with permanent view of the Sun is limited, and many potential users want them. So those who desire to build datacenters would have to compete for such orbital slots. There are much less such slots than for geosynchronous orbits. Other countries would certainly be outraged if USA occupied all the available slots with datacenters. Improved control of the satellites for collision avoidance could allow smaller slots, but maneuvering heavy datacenters would require a lot of fuel, so they might require periodic refueling, greatly increasing the costs.
NBJack 4mo ago
This isn't terribly practical. Yes, we can deal with heat. The trouble is cost, and dealing with high energy radiation both flipping bits and corrupting the silicon.
kryptiskt 4mo ago
Allow me to propose a modest alternative to space data centers, namely mountaintop data centers. This would consist of a container full of servers and GPUs and what else goes into a data center, a wind turbine for power and a communication module (say laser or microwave) for communicating with a base station with a fiber connection. This would be lifted on top of a mountain by a helicopter and bolted in place. Cooling would be provided by heat sinks exposed to the outside air. Some of the nodes could relay traffic from other nodes on remote mountain tops out of sight of the base station. This scheme has many advantages over space data centers including launch costs, cooling, connection latency, servicability and ease of recycling.
- noisy_boy 4mo ago
  What about the rough weather and difficulty of maintenance, especially in rough weather?
  - zarzavat 4mo ago
    Maintenance for a mountaintop data center only requires a team of skilled mountaineers. In space you'd need astronauts. It's at least an order of magnitude cheaper, perhaps two or three.
    - fc417fc802 4mo ago
      Nobody is doing maintenance on a small cluster in a satellite. It's disposable with a timespan of less than a decade to recoup all costs. Note that the usual argument to retire hardware is the electrical costs but when you've got lifetime solar you can run it indefinitely.
      - zarzavat 4mo ago
        Nobody is doing maintenance on an orbital data center because it's too expensive and dangerous, not because it wouldn't be useful. Maintenance in space would in fact be way more useful than on land because the redundancy required by a lack of maintenance necessitates extra mass. If you could pay a few space sherpas $100k to head up into LEO and service the thing, it would definitely be worth it.
neals 4mo ago
I think it's a vary valid option to launch swarms of datacenters into space. I think a few decades to a hundred years from now, it will be the norm. Until then, we can find plany of land to do it. Instead a launch, you just need a battery. Much cheaper. All the rest stays the same.
v9v 4mo ago
I'll add another to the list of relevant links in the comments: https://spectrum.ieee.org/orbital-data-centers-heat https://spectrum.ieee.org/orbital-data-centers-heat
tyeaglet 4mo ago
Only stating the solar panel - radiator area ratio and not mentioning the actual area that a data center should have, is a sin of omission - and a great one. Also, hand-waving numerous engineering problems just by saying “we’ve solve harder problems before / you can come up with a few designs” is the last thing I want to see in anything that comes up in Hacker News.
AnneTrotter 4mo ago
Whyyyy are we not building distributed data centers under driveways? I want one under my driveway to melt the snow. It can use my power and water hookups if it pays for them.
- otherme123 4mo ago
  Aren't some bitcoin farms used for heating in some places, like agriculture in greenhouses?
jdw64 4mo ago
What I don't understand about building a space data center is that you need radiators to release heat. Otherwise, it will become a space thermos. What's even more incomprehensible is that you would need specialized equipment for space radiation, and GPUs are consumables. To make that profitable, you would need pricing that is many times higher than the cost of a regular data center. I don't understand why there are people who actually fall for this. If I say this, people will call me someone who mocks others' challenges, but it seems like they're saying physical problems can be overcome too easily.
- BadBadJellyBean 4mo ago
  I have the feeling that the only reason that might actually be done is to escape from any kind of jurisdiction. In space no one can hear you compute.
  - jdw64 4mo ago
    If that's the case, wouldn't it be better to just put it in the desert? Realistically, if noise from calculations is the problem, placing it in a remote area would be more economical.
    - afavour 4mo ago
      The desert is still under someone’s jurisdiction. Perhaps the best on-planet comparison is creating a man made island in the middle of the ocean.
      - titanomachy 4mo ago
        This also seems more sensible than space, although I guess if you’re in international waters then no military will protect you and someone could eventually destroy it. Way more organizations have the ability to blow up a boat is compared to a space station.
    - _puk 4mo ago
      It's a play on "in space no-one can hear you scream", not a literal "compute is so noisy we need to go to space" The jurisdiction issue is the bigger one. Deserts don't solve this; International waters, possibly do, but then you've got other issues.
mcapodici 4mo ago
Seems reasonable that the area needed would be less than the solar panels. Since it sould be more efficient to dump heat than collect energy from light.
- vessenes 4mo ago
  It seems to me that there’s a lot of math in the middle of this that just doesn’t matter that much: every photon hitting every part of the array is going to add energy. Whatever percent we transform into data doesn’t matter — all the energy from all those photons minus energy used for station keeping needs to be radiated away. I guess if some is used for station keeping so much the better. I was hoping to read about what exactly these ‘heat pump radiators’ look like, but I guess ultimately they’re going to be lasers or flashlights or some such thing. A relativity course question I recall from my youth asked how long an astronaut stranded 1km from a ship would need to point the flashlight away to return to the ship based on the mass of the photons leaving the light — spoiler - this can work in time to save an astronaut’s life — double spoiler: if you’re really accurate, it’s better to throw the flashlight if you’re in a hurry. As I write this I realize my physics model is super weak, because I’m not sure what percent of the energy used to make a photon turns into the photon’s mass (and therefore is pushing against the laser), and what is in light and therefore just, you know, carries on for billions of years until it hits something else.
ep_jhu 4mo ago
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Springtime 4mo ago
There was also this[1] analysis in late 2025 from a former NASA engineer that looked at the impracticability. [1] https://taranis.ie/datacenters-in-space-are-a-terrible-horrible-no-good-idea/ https://taranis.ie/datacenters-in-space-are-a-terrible-horri...
afavour 4mo ago
It’s an interesting era to be alive in, where the rich and powerful (Trump, Musk) just assert things evidence free and then a whole community rolls in to come up with a post-facto rationalisation. Musk hasn’t thought about any of this. He just says stuff. He agreed with a statement that “space cooling is free”[1], as a sign of how deeply considered it all is. [1] https://nitter.net/elonmusk/status/1998483552669937682?lang=en https://nitter.net/elonmusk/status/1998483552669937682?lang=...
andriesm 4mo ago
If I had a dollar for everytime someone told me they have an advanced physics degree and can unequivocally gaurantee me that it will never be physically feasible to cool GPU's in space.... How soon those people have disappeared!
- Arodex 4mo ago
  Advanced physics degree holders are right, the linked article is full of mistakes. You can bullshit humans but you can't bullshit reality.
regularfry 4mo ago
Don't we also have to worry about heating of the solar panels themselves? 150W/m^2 isn't the incident power, it's the output power. Incident is something like ten times that. Some of that's going to be reflected, but not all of it.
JoelJacobson 4mo ago
This article made me think of a strange claim by Elon Musk at 07:08 in this [1] interview: "Cooling is actually much easier in space than it is on earth. You can just radiate to the vacuum." I don't think that follows. The radiator is only the final heat sink. You still need to move heat from very dense chips into a deployable, space-rated radiator, and handle pumps, loops, leaks, redundancy, radiation damage, replacement, eclipses, Earth IR/albedo, and launch mass. [1] https://youtu.be/D_1j5dVWNYI?si=R77VeVKlRXRhaBk5&t=428 https://youtu.be/D_1j5dVWNYI?si=R77VeVKlRXRhaBk5&t=428
- tristanj 4mo ago
  Radiators in space are a solved problem. The ISS has 70 kW of cooling via multiple radiators, using a dual loop water/ammonia system. The water loop cools the station and high-priority electronics, then the ammonia loop cools the water loop and transfers heat to the radiators, which release the heat out to space. There are additional radiators just for the solar panels. AI sat mini can use a simpler single ammonia loop, since the ISS uses a water loop on the station side to avoid toxicity issues in case of a coolant leak. It's a far simpler engineering problem to solve compared to other challenges SpaceX is facing (Starship, Raptor, Starlink).
  - JoelJacobson 4mo ago
    [flagged]
  - JoelJacobson 4mo ago
    [flagged]
  - JoelJacobson 4mo ago
    Sorry, should have emphasized that it was the "much easier" part I didn't agree with in that interview.
adrian_b 4mo ago
The computation in TFA is wrong. The incoming power is not the electrical power generated by the solar panels, but the entire power of the light that is absorbed by the solar panels and by the body of the satellite. Even with a perfectly reflecting body and with SOTA solar panels, the amount of incoming power is at least double in comparison with the electrical power consumed by the datacenter. Also, the heat radiated is smaller than in TFA, because no radiator is perfectly black at the radio waves in the frequency range corresponding to the ambient temperature. I am too lazy to make the correct computation, but there was another article linked on HN some days ago where a more plausible computation was done and the conclusion was that the minimum area of the radiators is slightly larger than the area required for solar panels. This would still be feasible, but in reality the area would have to be even larger, because the radiator cannot have a uniform temperature, the parts where the cooling fluid is incoming will be hotter than the parts where the cooling fluid is outgoing. Moreover, the pumping of the cooling fluid requires extra power that must be added to the power budget. There is no doubt that it is possible to build a space datacenter, if much more GPUs are installed in it than necessary, to enable to correct the more severe transient errors and to preserve enough capacity after many GPUs become permanently defective, but the cost will not be competitive with terrestrial datacenters any time soon.
- LargoLasskhyfv 4mo ago
  There are other options: https://spectrum.ieee.org/orbital-data-centers-heat#liquid-droplet%20radiators:~:text=Another%20possibility%20is%20to%20use%20liquid%2Ddroplet%20radiators https://spectrum.ieee.org/orbital-data-centers-heat#liquid-d... https://en.wikipedia.org/wiki/Liquid_droplet_radiator https://en.wikipedia.org/wiki/Liquid_droplet_radiator ( Myself from 4 months ago: https://news.ycombinator.com/item?id=46895344 https://news.ycombinator.com/item?id=46895344 (giggle) https://spectrum.ieee.org/microfluidics-cooling-ai-chips-corintis https://spectrum.ieee.org/microfluidics-cooling-ai-chips-cor... )
  - jauntywundrkind 4mo ago
    I went in wanting this to look real bad. But the Scott Manley video alas has sort of convinced me this is pretty feasible, that the energy budget is quite doable. https://youtu.be/FlQYU3m1e80 https://youtu.be/FlQYU3m1e80 I do think this is a pretty generous estimate he ends up at. I don't think emissivity is perfectly well dealt with. I don't know if his earth reflection emissivity includes the high energy thermal transfer from particles that do exist on the near vacuum (exosphere be hit, ya'll) or if that matters. But his figures seem ballpark correct & my concerns are at best marginal.
weinzierl 4mo ago
The make the whole calculation more detailed, e.g. include the orbit, there are specialized programs. The one ESA used to use is called ESATAN I used to share office with a colleague who mostly worked with it. This was at a time when the fad of naming products with an initial "e" had just faded. The surviving victim is "ebay" I guess, but at a time there were many like it. So my natural reading of the huge ASCII art rending on ESATAN's title screen has always been E-SATAN. Sorry ESA. Joking aside, you can download ESATAN here: https://www.esatan-tms.com https://www.esatan-tms.com It's not obvious what the download allows but expect restrictions. I remember the version we used had a HW dongle with heavy price tag every month.

35 points by LolWolf 4mo ago

All the comments are negative so I'll play the devil's advocate. Here's the steelman case for SpaceX orbital datacenters. # EARTH IS FULL It sounds ridiculous but the ability to build AI datacenters on Earth is nearly exhausted. The options are: • USA, Australia. The electricity infrastructure has already bottlenecked and some datacenters like Colossus are being forced to build their own power plants, but that's also bottlenecked on gas turbine capacity. Hacks like recycling jet turbines only squeeze a bit more out. Terrestrial solar can't be used to escape this problem because you need the clusters to run at night too. • Europe. Deindustrialized, EU Commission is anti AI, very expensive power, grid also bottlenecked. Forget it. • Middle East. Had some datacenters until they got blown up by Iran. • China. Got power but bottlenecked by trade sanctions. Might well do a big buildout when Ascend starts to be competitive, but Chinese demand is likely to absorb it. • Latin America, Africa, south-east Asia, etc: bottlenecked by political stability, not pro-business enough, etc. In space you don't need gas turbines because solar can be 24/7, political risks aren't there, you aren't bottlenecked by grid capacity. Even if it costs more to put stuff in space that doesn't matter if space is the only place you can put stuff. # INFERENCE NOT TRAINING Trying to do backpropagation in space would be a bad idea. You need extreme locality in a single physical location for networking reasons. But a lot of modern AI load including training load is just inference, which only requires small pods not entire clusters, and bandwidth needs in/out aren't that high. Inferencing can fit on a satellite. Space radiation isn't necessarily a problem. Bit flips can be tolerate to quite a high degree for inferencing because models can recover from corruptions in the activation stream or even some bad tokens. # COOLING As the article lays out this isn't necessarily the problem people are assuming. Also there are candidate designs from decades ago for ferrofluid droplet radiators. These might be overkill but can in theory radiate huge amounts of heat without needing to launch big radiators. # COST Unlike terrestrial data centers which are always bespoke projects, inferencing satellites can be mass manufactured. SpaceX and Elon in general are good at setting up mass production lines, and it seems apparent that SpaceX has no intention of throwing very high margin Nvidia hardware into orbit. The plan is to use Tesla's AI chips i.e. SpaceX could acquire accelerators at cost. This changes the cost calculations quite a bit. Although these accelerators might not be useful for training or research, most training workloads would stay on Earth so that doesn't matter (the inferencing loads moved into space would free up terrestrial hardware for training anyway). The real wild card is if there's enough demand for a 'good enough' model that it's predicted to last the lifetime of the satellite. In that case the weights could be fabbed directly into the chips like Taalas does, and so the energy consumption would be far lower. # BUSINESS CASE It's possible that datacenter construction goes the same way as nuclear and becomes impossibly expensive here on Earth. If so then SpaceX can end up with a near monopoly on new inferencing capacity, making them the gateway to AI and the new Nvidia. What's especially confounding is that the mere existence of orbital inferencing might actually create that outcome, because politicians would find it much easier to squash datacenter / power projects to please activists if there is a genuine alternative! Note: I'm not invested in SpaceX.

baq 4mo ago

See also https://andrewmccalip.com/space-datacenters https://andrewmccalip.com/space-datacenters with some models and numbers you can play with.

tristanj 4mo ago

Space data centers are physically possible but don't make financial sense. The total cost of an orbital datacenter over five years is at least 2–3x that of a terrestrial one. But those economics don't matter to SpaceX, because the main purpose of its orbital data centers is to create a use case for Starship. Starship has to fly frequently to iron out the kinks, encounter and fix rare (1/1000) failure situations, and optimize the launch cadence which pushes launch costs down. Plus Starship needs to fly a lot before it's ready for crewed flight. The long-term goal is a Starship optimized for crewed interplanetary travel. Orbital data centers are a payload that bring in some revenue, and provide a reason to launch constantly. It's the same thing they did with Starlink to make Falcon 9 as reliable and rapidly reusable as it is.

croes 4mo ago
My guess is: it just sounds cool. Like the cybertruck
pavlov 4mo ago
2-3x sounds like a very low estimate. There’s so much data center capacity being built all over the Earth. Thousands of large projects across US / China / Europe / Middle East. It would be astonishing if something that’s never been done before could be so cost-competitive immediately. Starlink wasn’t the first time LEO communications constellations were attempted. Multiple 1990s projects did it (Iridium, GlobalStar…) and went bankrupt. It took 30 years to make the concept work. SpaceX investors seem to be assuming the space data center business will be immediately viable.
- tristanj 4mo ago
  SemiAnalysis' report on orbital data centers estimated 4x terrestrial costs in 2026, then parity around ~2040. https://newsletter.semianalysis.com/p/to-boldly-go-the-case-for-space-datacenters https://newsletter.semianalysis.com/p/to-boldly-go-the-case-...
  - pavlov 4mo ago
    Based on very specific assumptions: “…the world in which AI demand is so overwhelming as to exceed the already formidable datacenter capacity additions” — but also this same world is one where GPU chip supply is abundant, there just isn’t enough data centers to put them in. This does not seem like the likeliest scenario to me.

amelius 4mo ago

See also: https://www.youtube.com/watch?v=FlQYU3m1e80 https://www.youtube.com/watch?v=FlQYU3m1e80

tristanj 4mo ago
And also: https://www.youtube.com/watch?v=JAcR7kqOb3o https://www.youtube.com/watch?v=JAcR7kqOb3o

echoangle 4mo ago

I still don’t see what the advantage is. Of course it’s physically possible to build a datacenter in space, but I can’t imagine land prices being that high that the same data center on earth wouldn’t be cheaper. Even just due to launch costs and the more sophisticated equipment needed for space.

XorNot 4mo ago
The real issue is that the power situation in LEO is still actually terrible! Your solar is a little more performant, but you're plunged into hard shade every 45 minutes.
- athrowaway3z 4mo ago
  I think calling solar a little more performant is underselling it. Once you have LEO getting to a better orbit costs relatively little. Getting from LEO to the moon is only like 30% more than getting from ground to LEO.
  - curiousObject 4mo ago
    True, but lifting the fuel to power that “small” orbital boost is unintuitively expensive (Refer to the tyranny of the “Rocket Equation”)
- adrian_b 4mo ago
  There exist the so-called Sun-synchronous orbits, which exploit the precession effect caused by the fact that the Earth is not a sphere, to pass over the same point of the Earth at the same local hour. On a small subset of these Sun-synchronous orbits the Sun is always visible from the satellite (i.e. on the subset of orbits whose plane is approximately perpendicular on the radius that connects the Sun to the Earth). Without the precession effect, a satellite that sees the Sun for an entire day would lose this property after a few days, because of the rotation of the Earth around the Sun, which alters the direction in space of the radius from the Sun to the Earth. However, the number of slots that are available in Sun-synchronous orbits with permanent view of the Sun is limited, and many potential users want them. So those who desire to build datacenters would have to compete for such orbital slots. There are much less such slots than for geosynchronous orbits. Other countries would certainly be outraged if USA occupied all the available slots with datacenters. Improved control of the satellites for collision avoidance could allow smaller slots, but maneuvering heavy datacenters would require a lot of fuel, so they might require periodic refueling, greatly increasing the costs.

NBJack 4mo ago

This isn't terribly practical. Yes, we can deal with heat. The trouble is cost, and dealing with high energy radiation both flipping bits and corrupting the silicon.

kryptiskt 4mo ago

Allow me to propose a modest alternative to space data centers, namely mountaintop data centers. This would consist of a container full of servers and GPUs and what else goes into a data center, a wind turbine for power and a communication module (say laser or microwave) for communicating with a base station with a fiber connection. This would be lifted on top of a mountain by a helicopter and bolted in place. Cooling would be provided by heat sinks exposed to the outside air. Some of the nodes could relay traffic from other nodes on remote mountain tops out of sight of the base station. This scheme has many advantages over space data centers including launch costs, cooling, connection latency, servicability and ease of recycling.

noisy_boy 4mo ago
What about the rough weather and difficulty of maintenance, especially in rough weather?
- zarzavat 4mo ago
  Maintenance for a mountaintop data center only requires a team of skilled mountaineers. In space you'd need astronauts. It's at least an order of magnitude cheaper, perhaps two or three.
  - fc417fc802 4mo ago
    Nobody is doing maintenance on a small cluster in a satellite. It's disposable with a timespan of less than a decade to recoup all costs. Note that the usual argument to retire hardware is the electrical costs but when you've got lifetime solar you can run it indefinitely.
    - zarzavat 4mo ago
      Nobody is doing maintenance on an orbital data center because it's too expensive and dangerous, not because it wouldn't be useful. Maintenance in space would in fact be way more useful than on land because the redundancy required by a lack of maintenance necessitates extra mass. If you could pay a few space sherpas $100k to head up into LEO and service the thing, it would definitely be worth it.

neals 4mo ago

I think it's a vary valid option to launch swarms of datacenters into space. I think a few decades to a hundred years from now, it will be the norm. Until then, we can find plany of land to do it. Instead a launch, you just need a battery. Much cheaper. All the rest stays the same.

v9v 4mo ago

I'll add another to the list of relevant links in the comments: https://spectrum.ieee.org/orbital-data-centers-heat https://spectrum.ieee.org/orbital-data-centers-heat

tyeaglet 4mo ago

Only stating the solar panel - radiator area ratio and not mentioning the actual area that a data center should have, is a sin of omission - and a great one. Also, hand-waving numerous engineering problems just by saying “we’ve solve harder problems before / you can come up with a few designs” is the last thing I want to see in anything that comes up in Hacker News.

AnneTrotter 4mo ago

Whyyyy are we not building distributed data centers under driveways? I want one under my driveway to melt the snow. It can use my power and water hookups if it pays for them.

otherme123 4mo ago
Aren't some bitcoin farms used for heating in some places, like agriculture in greenhouses?

jdw64 4mo ago

What I don't understand about building a space data center is that you need radiators to release heat. Otherwise, it will become a space thermos. What's even more incomprehensible is that you would need specialized equipment for space radiation, and GPUs are consumables. To make that profitable, you would need pricing that is many times higher than the cost of a regular data center. I don't understand why there are people who actually fall for this. If I say this, people will call me someone who mocks others' challenges, but it seems like they're saying physical problems can be overcome too easily.

BadBadJellyBean 4mo ago
I have the feeling that the only reason that might actually be done is to escape from any kind of jurisdiction. In space no one can hear you compute.
- jdw64 4mo ago
  If that's the case, wouldn't it be better to just put it in the desert? Realistically, if noise from calculations is the problem, placing it in a remote area would be more economical.
  - afavour 4mo ago
    The desert is still under someone’s jurisdiction. Perhaps the best on-planet comparison is creating a man made island in the middle of the ocean.
    - titanomachy 4mo ago
      This also seems more sensible than space, although I guess if you’re in international waters then no military will protect you and someone could eventually destroy it. Way more organizations have the ability to blow up a boat is compared to a space station.
  - _puk 4mo ago
    It's a play on "in space no-one can hear you scream", not a literal "compute is so noisy we need to go to space" The jurisdiction issue is the bigger one. Deserts don't solve this; International waters, possibly do, but then you've got other issues.

mcapodici 4mo ago

Seems reasonable that the area needed would be less than the solar panels. Since it sould be more efficient to dump heat than collect energy from light.

vessenes 4mo ago
It seems to me that there’s a lot of math in the middle of this that just doesn’t matter that much: every photon hitting every part of the array is going to add energy. Whatever percent we transform into data doesn’t matter — all the energy from all those photons minus energy used for station keeping needs to be radiated away. I guess if some is used for station keeping so much the better. I was hoping to read about what exactly these ‘heat pump radiators’ look like, but I guess ultimately they’re going to be lasers or flashlights or some such thing. A relativity course question I recall from my youth asked how long an astronaut stranded 1km from a ship would need to point the flashlight away to return to the ship based on the mass of the photons leaving the light — spoiler - this can work in time to save an astronaut’s life — double spoiler: if you’re really accurate, it’s better to throw the flashlight if you’re in a hurry. As I write this I realize my physics model is super weak, because I’m not sure what percent of the energy used to make a photon turns into the photon’s mass (and therefore is pushing against the laser), and what is in light and therefore just, you know, carries on for billions of years until it hits something else.

ep_jhu 4mo ago

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Springtime 4mo ago

There was also this[1] analysis in late 2025 from a former NASA engineer that looked at the impracticability. [1] https://taranis.ie/datacenters-in-space-are-a-terrible-horrible-no-good-idea/ https://taranis.ie/datacenters-in-space-are-a-terrible-horri...

afavour 4mo ago

It’s an interesting era to be alive in, where the rich and powerful (Trump, Musk) just assert things evidence free and then a whole community rolls in to come up with a post-facto rationalisation. Musk hasn’t thought about any of this. He just says stuff. He agreed with a statement that “space cooling is free”[1], as a sign of how deeply considered it all is. [1] https://nitter.net/elonmusk/status/1998483552669937682?lang=en https://nitter.net/elonmusk/status/1998483552669937682?lang=...

andriesm 4mo ago

If I had a dollar for everytime someone told me they have an advanced physics degree and can unequivocally gaurantee me that it will never be physically feasible to cool GPU's in space.... How soon those people have disappeared!

Arodex 4mo ago
Advanced physics degree holders are right, the linked article is full of mistakes. You can bullshit humans but you can't bullshit reality.

regularfry 4mo ago

Don't we also have to worry about heating of the solar panels themselves? 150W/m^2 isn't the incident power, it's the output power. Incident is something like ten times that. Some of that's going to be reflected, but not all of it.

JoelJacobson 4mo ago

This article made me think of a strange claim by Elon Musk at 07:08 in this [1] interview: "Cooling is actually much easier in space than it is on earth. You can just radiate to the vacuum." I don't think that follows. The radiator is only the final heat sink. You still need to move heat from very dense chips into a deployable, space-rated radiator, and handle pumps, loops, leaks, redundancy, radiation damage, replacement, eclipses, Earth IR/albedo, and launch mass. [1] https://youtu.be/D_1j5dVWNYI?si=R77VeVKlRXRhaBk5&t=428 https://youtu.be/D_1j5dVWNYI?si=R77VeVKlRXRhaBk5&t=428

tristanj 4mo ago
Radiators in space are a solved problem. The ISS has 70 kW of cooling via multiple radiators, using a dual loop water/ammonia system. The water loop cools the station and high-priority electronics, then the ammonia loop cools the water loop and transfers heat to the radiators, which release the heat out to space. There are additional radiators just for the solar panels. AI sat mini can use a simpler single ammonia loop, since the ISS uses a water loop on the station side to avoid toxicity issues in case of a coolant leak. It's a far simpler engineering problem to solve compared to other challenges SpaceX is facing (Starship, Raptor, Starlink).
- JoelJacobson 4mo ago
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- JoelJacobson 4mo ago
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- JoelJacobson 4mo ago
  Sorry, should have emphasized that it was the "much easier" part I didn't agree with in that interview.

adrian_b 4mo ago

The computation in TFA is wrong. The incoming power is not the electrical power generated by the solar panels, but the entire power of the light that is absorbed by the solar panels and by the body of the satellite. Even with a perfectly reflecting body and with SOTA solar panels, the amount of incoming power is at least double in comparison with the electrical power consumed by the datacenter. Also, the heat radiated is smaller than in TFA, because no radiator is perfectly black at the radio waves in the frequency range corresponding to the ambient temperature. I am too lazy to make the correct computation, but there was another article linked on HN some days ago where a more plausible computation was done and the conclusion was that the minimum area of the radiators is slightly larger than the area required for solar panels. This would still be feasible, but in reality the area would have to be even larger, because the radiator cannot have a uniform temperature, the parts where the cooling fluid is incoming will be hotter than the parts where the cooling fluid is outgoing. Moreover, the pumping of the cooling fluid requires extra power that must be added to the power budget. There is no doubt that it is possible to build a space datacenter, if much more GPUs are installed in it than necessary, to enable to correct the more severe transient errors and to preserve enough capacity after many GPUs become permanently defective, but the cost will not be competitive with terrestrial datacenters any time soon.

LargoLasskhyfv 4mo ago
There are other options: https://spectrum.ieee.org/orbital-data-centers-heat#liquid-droplet%20radiators:~:text=Another%20possibility%20is%20to%20use%20liquid%2Ddroplet%20radiators https://spectrum.ieee.org/orbital-data-centers-heat#liquid-d... https://en.wikipedia.org/wiki/Liquid_droplet_radiator https://en.wikipedia.org/wiki/Liquid_droplet_radiator ( Myself from 4 months ago: https://news.ycombinator.com/item?id=46895344 https://news.ycombinator.com/item?id=46895344 (giggle) https://spectrum.ieee.org/microfluidics-cooling-ai-chips-corintis https://spectrum.ieee.org/microfluidics-cooling-ai-chips-cor... )
- jauntywundrkind 4mo ago
  I went in wanting this to look real bad. But the Scott Manley video alas has sort of convinced me this is pretty feasible, that the energy budget is quite doable. https://youtu.be/FlQYU3m1e80 https://youtu.be/FlQYU3m1e80 I do think this is a pretty generous estimate he ends up at. I don't think emissivity is perfectly well dealt with. I don't know if his earth reflection emissivity includes the high energy thermal transfer from particles that do exist on the near vacuum (exosphere be hit, ya'll) or if that matters. But his figures seem ballpark correct & my concerns are at best marginal.

weinzierl 4mo ago

The make the whole calculation more detailed, e.g. include the orbit, there are specialized programs. The one ESA used to use is called ESATAN I used to share office with a colleague who mostly worked with it. This was at a time when the fad of naming products with an initial "e" had just faded. The surviving victim is "ebay" I guess, but at a time there were many like it. So my natural reading of the huge ASCII art rending on ESATAN's title screen has always been E-SATAN. Sorry ESA. Joking aside, you can download ESATAN here: https://www.esatan-tms.com https://www.esatan-tms.com It's not obvious what the download allows but expect restrictions. I remember the version we used had a HW dongle with heavy price tag every month.