38 ms·

What really worries me is that I keep hearing "cooling is cheap and easy in space!" in a lot of these conversations, and it couldn't be farther from the truth.

• IncreasePosts 9mo ago
  Who says that? Every conversation I've seen is despite how many serious organizations with talented people, the "uhhh how do you cool it?" Is brought up immediately
• wmf 9mo ago
  None of it is easy but neither is cooling impossible as many people are saying.
  • mjhay 9mo ago
    There’s a big difference between “impossible” (it isn’t) and “practical” (it isn’t).
    • dzhiurgis 9mo ago
      What happened to "do things that don't scale"?
      • WJW 9mo ago
        Maybe you should re-read the "do things that don't scale" article. It is about doing things manually until you figure out what you should automate, and only then do you automate it. It's not about doing unscalable things forever. Unless you have a plan to change the laws of physics, space will always be a good insulator compared to what we have here on Earth.
        • dzhiurgis 9mo ago
          Ok fair enough. No need to rewrite anything. Radiators are 30% heavier per watt than solar panels. This is far from impossible.
  • cmgbhm 9mo ago
    Doing like an 8xh200 server (https://docs.nvidia.com/dgx/dgxh100-user-guide/introduction-to-dgxh100.html https://docs.nvidia.com/dgx/dgxh100-user-guide/introduction-...) is 10.2kW. Let’s say you need 50m^2 solar panels to run it, then just a ton of surface area to dissipate. I’d love to be proven wrong but space data centers just seem like large 2d impact targets.
    • wmf 9mo ago
      Yeah, you need 50m^2 of solar panels and 50m^2 of radiators. I don't see why one is that much more difficult than the other.
      • rekenaut 9mo ago
        Especially if with the radiators you can just roll out as rolls of aluminum foil, which is very light and very cheap.
        • viraptor 9mo ago
          Only on a short distance. To effectively radiate a significant amount of heat, you need to actually deliver the heat to the distant parts of the radiator first. That normally requires active pumping which needs extra energy. So now you need to unfold sonar panels + aluminium + pipes (+ maybe extra pumps)
          • notahacker 9mo ago
            Orbital assembly of a fluid piping system in space is a pretty colossal problem too (as well as miles of pipes and connections being a massive single point failure for your system). Dispersing the GPUs might be more practical, but it's not exactly optimal for high performance computation...
            • coffeebeqn 9mo ago
              It’s a fun problem to think about but even if all the problems were solved we would have very quickly deprecating hardware in orbit that’s impossible to service or upgrade
• yabones 9mo ago
  Yeah, I don't see a way to get around the fact that space is a fabulous insulator. That's precisely how expensive insulated drink containers work so well. If it was just about cooling and power availability, you'd think people would be running giant solar+compute barges in international waters, but nobody is doing that. Even the "seasteading" guys from last decade. These proposals, if serious, are just to avoid planning permission and land ownership difficulties. If unserious, it's simply to get attention. And we're talking about it, aren't we?
  • eldenring 9mo ago
    You should read the linked article, they talk about it there. You radiate the heat into space which takes less surface area than the solar panels and you can just have them back to back. In general I don't understand this line of thinking. This would be such a basic problem to miss, so my first instinct would be to just look up what solution other people propose. It is very easy to find this online.
    • deleted 9mo ago
      [deleted]
    • mkesper 9mo ago
      Please have a look at how real stations like ISS handle the problem and do not trust in should-work science fiction. It's hard. https://en.wikipedia.org/wiki/International_Space_Station#Power_and_thermal_control https://en.wikipedia.org/wiki/International_Space_Station#Po...
      • jcattle 9mo ago
        Taking a system which was conceptualized about a quarter of a century ago and serves much different needs than what a datacenter in space needs (e.g. very strict thermal band, compared to acceptable temperature range from 20 to 80 degrees) isn't ideal. The physics is quite simple and you can definitely make it work out. The Stefan Boltzman law works in your favor the higher you can push your temperatures. If anything a orbital datacenter could be a slightly easier case. Ideally it will be in an orbit which always sees the sun. Most other satellites need to be in the earth shadow from time to time making heaters as well radiators necessary.
• renewiltord 9mo ago
  For some decades now I’ve heard the debunk many times more than the bunk. The real urban myth appears to be any appreciable fraction of people believe the myth.
• pavon 9mo ago
  Cooling isn't anymore difficult than power generation. For example, on the ISS solar panels generate up to 75 W/m², while the EATCS radiators can dissipate about 150 W/m². Solar panels have improved more than cooling technology since ISS was deployed, but the two are still on the same order of magnitude.
  • Nevermark 9mo ago
    So just 13.3 million sq. meters of solar panels, and 6.67 million sq. meters of cooling panels for 1 GW. Or a 3.651 km squared and 2.581 km squared butterfly sattelite. I don't think your cooling area measures account for the complications introduced by scale. Heat dissipation isn't going to efficiently work its way across surfaces at that scale passively. Dissipation will scale very sub-linearly, so we need much more area, and there will need to be active fluid exchangers operating at speed spanning kilometers of real estate, to get dissipation/area anywhere back near linear/area again. Liquid cooling and pumps, unlike solar, are meaningfully talked about in terms of volume. The cascade of volume, mass, complexity and increased power up-scaling flows back to infernal launch volume logistics. Many more ships and launches. Cooling is going to be orders of magnitude more trouble than power. How are these ideas getting any respect? I could see this at lunar poles. Solar panels in permanent sunlight, with compute in direct surface contact or cover, in permanent deep cold shadow. Cooling becomes an afterthought. Passive liquid filled cooling mats, with surface magnifying fins, embedded in icy regolith, angled for passive heat-gradient fluid cycling. Or drill two adjacent holes, for a simple deep cooling loop. Very little support structure. No orbital mechanics or right-of-way maneuvers to negotiate. Scales up with local proximity. A single expansion/upgrade/repair trip can service an entire growing operation at one time, in a comfortable stable g-field.
    • withinboredom 9mo ago
      Lets not forget that you have to launch that liquid up as well. Liquids are heavy, compared to their volume. Not to mention your entire 'datacenter' goes poof if one of these loops gets frozen, explodes from catching some sunlight, or whatever. This is pretty normal stuff, but not at this scale that would be required.
• terminalshort 9mo ago
  But space isn't actually cold, or at least not space near Earth. It's about 10 C. And that's only about a 10 C less than room temperature, so a human habitable structure in near earth space won't radiate very much heat. But heat radiated is O(Tobject^4 - Tbackground^4), and a computer can operate up to around 90C (I think) so that is actually a very big difference here. Back of the envelope, a data center at 90C will radiate about 10x the heat that a space station at 20C will. With the massive caveat that I don't know what the constant is here, it could actually be easy to keep a datacenter cool even though it is hard to keep a space station cool.
  • modeless 9mo ago
    The temperature that you raise to the fourth power is not Celsius, it's Kelvin. Otherwise things at -200 C would radiate more heat than things at 100 C. Also the temperature of space is ~3 K (cosmic microwave background), not 10 C.
    • terminalshort 9mo ago
      Yeah, if you forget about the giant fucking star nearby
      • modeless 9mo ago
        The Sun is also not 10 C. Luckily you have solar arrays which shade your radiators from it, so you can ignore the direct light from it when calculating radiator efficiency. The actual concern in LEO is radiation from the Earth itself.
    • ithkuil 9mo ago
      There is a large region of the upper atmosphere called the thermosphere where there is still a little bit of air. The pressure is extremely low but the few molecules that are there are bombarded by intense radiation and thus reach pretty high temperatures, even 2000 C! But since there are so few such molecules in any cubic meter, there isn't much energy in them. So if you put an object in such a rarefied atmosphere. It wouldn't get heated up by it despite such a gas formally having such a temperature. The gas would be cooled down upon contact with the body and the body would be heated up by a negligible amount
• fanf2 9mo ago
  This article assumes that no extra mass is needed for cooling, i.e. that cooling is free. The list of model assumptions includes: • No additional mass for liquid cooling loop infrastructure; likely needed but not included • Thermal: only solar array area used as radiator; no dedicated radiator mass assumed
  • davedx 9mo ago
    Yeah that's just flat out wrong then: you can't use the solar array as a radiator.
    • jcattle 9mo ago
      Of course you can. You can use everything as a radiator. Unless you have something which is literally 0 Kelvin everything radiates. See here for all the great ways of getting rid of thermal energy in space: https://www.nasa.gov/smallsat-institute/sst-soa/thermal-control/ https://www.nasa.gov/smallsat-institute/sst-soa/thermal-cont...
      • notahacker 9mo ago
        You can use everything as a radiator, but you can't use everything as a radiator sufficiently efficient to cool hot chips to safe operating temperature, particularly not if that thing is a thin panel intentionally oriented to capture the sun's rays to convert them to energy. Sure, you can absolutely build a radiator in the shade of the panels (it's the most logical place), but it's going to involve extra mass.
        • dsr_ 9mo ago
          You also want to orient those radiators at 90 degrees to the power panels, so that they don't send 50% of their radiation right back to the power panels.
      • oivey 9mo ago
        You can rivet people onto the outside of the ISS to radiate heat, too, but it may be detrimental to the overall system.
• jmyeet 9mo ago
  I've done some reading on how they cool JWST. It's fascinating and was a massive engineering challenge. Some of thos einstruments need to be cooled to near absolute zero, so much so that it uses liquid helium as a coolant in parts. Now JWST is at near L2 but it is still in sunlight. It's solar-powered. There are a series of radiating layer to keep heat away from sensitive instruments. Then there's the solar panels themselves. Obviously an orbital data center wouldn't need some extreme cooling but the key takeaway from me is that the solar panels themselves would shield much of the satellite from direct sunlight, by design. Absent any external heating, there's only heating from computer chips. Any body in space will radiate away heat. You can make some more effective than others by increasing surface area per unit mass (I assume). Someone else mentioned thermoses as evidence of insulation. There's some truth to that but interestingly most of the heat lost from a thermos is from the same IR radiation that would be emitted by a satellite.
  • Turskarama 9mo ago
    The computer chips used for AI generate significantly more heat than the chips on the JWST. The JWST in total weighs 6.5 tons and uses a mere 2kw of power, which is the same as 3 H100 GPUs under load, each of which will weight what, 1kg? So in terms of power density you're looking at about 3 orders of magnitude difference. Heating and cooling is going to be a significant part of the total weight.
• PeterHolzwarth 9mo ago
  "space is cold" I've always enjoyed thinking about this. Temperature is a characteristic of matter. There is vanishingly little matter in space. Due to that, one could perhaps say that space, in a way of looking at it, has no temperature. This helps give some insight into what you mention of the difficulties in dealing with heat in space - radiative cooling is all you get. I once read that, while the image we have in our mind of being ejected out of an airlock from a space station in orbit around Earth results in instant ice-cube, the reality is that, due to our distance from the sun, that situation - ignoring the lack of oxygen etc that would kill you - is such that we would in fact die from heat exhaustion: our bodies would be unable to radiate enough heat vs what we would receive from the sun. In contrast, were one to experience the same unceremonious orbital defenestration around Mars, the distance from the sun is sufficient that we would die from hypothermia (ceteris paribus, of course).
  • zeofig 9mo ago
    A perfect vacuum might have no temperature, but space is not a perfect vacuum, and has a well-defined temperature. More insight would be found in thinking about what temperature precisely means, and the difference between it and heat capacity.
    • bee_rider 9mo ago
      I think your second sentence is what they were referencing. Space has a temperature. But because the matter is so sparse and there’s so little thermal mass to carry heat around as a result, we don’t have an intuitive grasp on what the temperature numbers mean.
      • zeofig 9mo ago
        I think otherwise.
      • fc417fc802 9mo ago
        To rephrase it slightly. It's not a perfect vacuum, but compared to terrestrial conditions it's much closer to the former than the latter. The physics naturally reflects that fact. To illustrate the point with a concrete example. You can heat something with the thermal transfer rate of aerogel to an absurdly high temperature and it will still be safe to pick up with your bare hand. Physics says it has a temperature but our intuition says something is wrong with the physics.
• noosphr 9mo ago
  Space hardware needs to be fundamentally different from surface hardware. I don't mean it in the usual radiation hardenrining etc, but in using computing substrates that run over 1000c and never shut down. T^4 cooling means that you have a hell of a time keeping things cool, but keeping hot things from melting completely is much easier.
  • baq 9mo ago
    if you have a compute substrate at 1300K you don't have a cooling problem - you have an everything else problem
    • noosphr 9mo ago
      There are very high temperature transistors. We don't use them on earth because we expect humans to be near computers and keeping anything extremely hot is a waste of energy. But an autonomous space data center has no reason to be kept even remotely human habitable.
      • TheOtherHobbes 9mo ago
        The transistors are experimental, and no one is building high-performance chips out of them. You can't just scale current silicon nodes to some other substrate. Even if you could, there's a huge difference between managing the temperature of a single transistor, managing temps on a wafer, and managing temps in a block of servers running close to the melting point of copper.
• davedx 9mo ago
  I think the point is, yes, cooling is a significant engineering challenge in space; but having easy access to abundant energy (solar) and not needing to navigate difficult politically charged permitting processes makes it worthwhile. It's a big set of trade offs, and to only focus on "cooling being very hard in space" is kind of missing the point of why these companies want to do this. Compute is severely power-constrained everywhere except China, and space based datacenters is a way to get around that.
  • TheOtherHobbes 9mo ago
    Of course you can build these things if you really want to. But there is no universe in which it's possible to build them economically. Not even close. The numbers are simply ridiculous. And that's not even accounting for the fact that getting even one of these things into orbit is an absolutely huge R&D project that will take years - by which time technology and requirements will have moved on.
    • JoeAltmaier 9mo ago
      Lift costs dropping geometrically. Cost and weight of solar decreasing similarly. The trend makes space-based centers nearly inevitable. Reminds me of "Those darn cars! Everybody knows that trains and horses are the way to travel."
      • Yizahi 9mo ago
        Lift costs are not quite dropping like that lately. Starship is not yet production ready (and you need to fully pack it with payloads, to achieve those numbers). What we saw is cutting off most of the artificial margins of the old launches and arriving to some economic equilibrium with sane margins. Regardless of the launch price the space based stuff will be much more expensive than planet based, the only question if it will be optimistically "only" x10 times more expensive, or pessimistically x100 times more expensive. I don't get this "inevitable" conclusion. What is even a purpose of the space datacenter in the first place? What would justify paying an order of magnitude more than conventional competitors? Especially if the server in question in question is a dumb number cruncher like a stack of GPUs? I may understand putting some black NSA data up there or drug cartel accounting backup, but to multiply some LLM numbers you really have zero need of extraterritorial lawless DC. There is no business incentive for that.
• vessenes 9mo ago
  Jusssst had this conversation two nights ago with a smart drunk friend. To his credit when I asked "what's heat?" and he said "molecules moving fast" and I said "how many molecules are there in space to bump against?" He immediately got it. I'm always curious what ideas someone that isn't familiar with a problem space comes up with for solutions, so I canvased him for thoughts -- nothing novel, unfortunately, but if we get another 100 million people thinking about it, who knows what we'll come up with?
  • BobaFloutist 9mo ago
    I got really annoyed when I first realized that heat and sound (and kinetic energy) are both "molecules moving," because they behave so dramatically differently on a human scale. And yes, obviously they aren't moving in the same way, but it's still kind of weird to think about.
• moralestapia 9mo ago
  Maybe hang out with different people? Everyone I talked to (and everyone on this forums) knows cooling is hard in space. It is always the number one comment on every news piece that is featured here talking about "AI in space".
• BobbyTables2 9mo ago
  Indeed. If cooling in space was that easy then we would have just built datacenters in hermetically sealed terrestrial containers…