Summarizer

It kinda does make sense if you consider that solar panels in space have been used for a very long time (to power satellites). However, getting the electricity they generate down to Earth is very complicated, so you end up having to use it in space, and one of few things that would make sense for that is indeed data centers, because getting the data to Earth is easier (and Elon already handily has a solution for that). However I'm curious how many solar panels you would need to power a typical data center. Are we talking something like a large satellite, or rather a huge satellite with ISS-size solar arrays bolted on? Getting rid of the copious amounts of heat that data centers generate might also be a challenge ( https://en.wikipedia.org/wiki/Spacecraft_thermal_control )...

> It kinda does make sense if you consider that solar panels in space have been used for a very long time (to power satellites). It stops making sense the second you ask how you’d dissipate the heat any GPU would create. Sure, you could have vapour chambers. To where? Would this need square kilometers of radiators on top of square kilometers of solar panels? All this just to have Grok in space?

You have a dark radiating side on the back of the solar panels. You can spread the GPUs around the solar panels. All the energy in comes from the sun so the temperature should be much the same as any dark panel like object floating in sunlight in space.

> It stops making sense the second you ask how you’d dissipate the heat any GPU would create. The answer, as you surmised, is indeed radiators.

But space is very cold, so no problem there /sarcasm

>Getting rid of the copious amounts of heat that data centers generate might also be a challenge at 70 Celsius - normal for GPU - 1.5m2 radiates something like 1KWt (which requires 4m2 of panels to collect), so doesn't look to a be an issue. (some look to ISS which is a bad example - the ISS needs 20 Celsius, and black body radiation is T^4)

So for the ISS at 20c you'd get 481 W/m^2 so you'd only need 2.3m2. So comparing the ISS at 20c to space datacenters at 70c you get an improvement of 63%. Nice, but doesn't feel game-changing. The power radiated is T^4, but 70c is only about 17.1% warmer than 20c because you need to compare in kelvin.

Just scratching at the surface, assuming the increase in production capacity is only realistically possible if you can bring prices down (or this "project" would start to consume a proportion of economic output large enough to seem implausible), you can address the intermittency problem in several ways: Driving down the cost makes massive overprovision a means of reducing the intermittency because you will be able to cover demand at proportionally far lower output, which also means you'll be able to cover demands in far larger areas, even before looking at storage. But lower solar costs would also make storage more cost effective, since power cost will be a lower proportion of the amortised cost of the total system. Same with increasing transmission investments to allow smoothing load. Ever cost drop for solar will make it able to cover a larger proportion of total power demand, and we're nowhere near maximising viable total capacity even at current costs. A whole lot of industrial costs are also affected by energy prices. Drive down this down, and you should expect price drops in other areas as well as industrial uses where energy expensive processes are not cost-effective today. The geopolitical consequences of a dramatic acceleration of the drop in dependency on oil and gas would also take decades to play out. At the same time, if you can drive down the cost of energy by making solar so much cheaper, you also make earth-bound data centres more cost-competive, and the cost-advantage of space-bound data centres would be accordingly lower. I think it's an interesting idea to explore (but there's the whole issue of cooling being far harder in space), but I also think the effects would be far broader. By all means, if Musk wants to poor resources into making solar cheap enough for this kind of project to be viable, he should go ahead - maybe it'll consume enough of time to give him less time to plan a teenage edgelor - because I think the societal effects of driving down energy costs would generally be positive, AI or not, it just screams of being a justification for an xAI purchase done mostly for his personal financial engineering.

5 to 7 months given they want 100kw Per ton and magical mystery sauce shielding is going to do shit all.

Yes, because launching then immersed in something that will greatly increase the launch weight will help...

Tell me about your cooling medium in space

A large piece of aluminum with ammonia pumped through it?

Right up to the radiation limit and then you'll either have to throttle your precious GPUs or you'll be melting your satellite or at least the guts of it. You're looking at an absolutely massive radiator here, many times larger than the solar panels that collect the energy to begin with.

not really, for A_radiator / A_PV = ~3; you can keep the satellite cool to about 27 deg C (300K) check my example calculation (Ctrl-F: pyramid)

> > absolutely massive radiator here, many times larger than the solar panels > A_radiator / A_PV = ~3; Seems like you're in agreement. There's a couple more issues here-- 1. Solar panels are typically big compared to the rest of the satellite bus. How much radiator area do you need per 700W GPU at some reasonable solar panel efficiency? 2. Getting the satellite overall to an average 27C temperature doesn't necessarily keep the GPU cool; the satellite is not isothermal.

Where does the heat collected by amminia get evacuated?

Through thermal radiation, it's called radiative cooling. But it's not trivial indeed, especially if you want good power density in your space data center.

Datacenter capacity (and thus heat) grows by the cube law, but the ability to radiate heat grows by the square law, so it seems like it would be advantageous to have a bunch of smaller satellites, if you were concerned about cooling them.

> it would be advantageous to have a bunch of smaller satellites, if you were concerned about cooling them. ...That's only relevant if you start from the position that your datacenters have to be space. You could already make smaller datacenters on earth, and still have better cooling, if you were concerned about that. We don't do that because on earth it's more efficient to have one large datacenter than many small ones.

1) yes solar panels should be cooled, but this is feasible with thermal radiation (yes it takes surface area) 2) pointing the panels straight at the sun for a sun-synchronous orbit is not exactly unobtainium technology 3) through 6) agreed, these issues need to be taken into account but I don't see how that meaningfully invalidates my claim that a solar panel operated at 25% efficiency turns ballpark ~75% of incident photons into heat. Thats basic thermodynamics.

You don't need any major technological advances to build a proof-of-concept You do - cooling those datacenters in space is an unsolved problem.

Sure it is, just not economically at that scale yet. But if Starship brings the cost to orbit down significantly, maybe.

We have radiators on the ISS. Even if you kept the terrible performance of those ancient radiator designs (regularly exposed to sunlight, simplistic ammonia coolant, low temperature) you could just make them bigger and radiate the needed energy. Yes it would require a bit of engineering but to call it an "unsolved problem" is just exaggerating.

It's a solved problem. The physics is simply such that it's really inefficient. > ... we'd need a system 12.5 times bigger, i.e., roughly 531 square metres, or about 2.6 times the size of the relevant solar array. This is now going to be a very large satellite, dwarfing the ISS in area, all for the equivalent of three standard server racks on Earth. https://taranis.ie/datacenters-in-space-are-a-terrible-horri... The gist of it is that about 99% of cooling on earth works by cold air molecules (or water) bumping into hot ones, and transferring heat. There's no air in space, so you need a radiator 99x larger than you would down here. That adds up real fast.

I think you may be thinking of cooling to habitable temperatures (20c). You can run GPUs at 70c , so radiative cooling density goes up exponentially. You should need about 1/3 of the array in radiators.

A really painfully laboured way of just saying conduction.

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. ----------- 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.

Your calculations are based on cooling to 20c, which is exponentially harder than cooling to 70c where GPUs are happy. Radiators would be roughly 1/3 the size of the panels for 70c.

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?

What do you do with the steam afterwards? If you eject it, you have to bring lots of it with your spacecraft, and that costs serious money. If you let it condensate to get water again, all you did is moving some heat inside the spacecraft, almost certainly creating even more heat when doing that.

It's a good question, but in a closed system (like you have in space) the heat from the turbine loop has to go somewhere in order to make it useful. Let's say you have a coolant loop for the gpus (maybe glycol). You take the hot glycol, run it through your heat exchanger and heat up your cool, pressurized ammonia. The ammonia gets hot (and now the glycol is cool, send it back). You then take the ammonia and send it through the turbine and it evaporates as it expands and loses pressure to spin the turbine. But now what? You have warm, vaporized, low pressure ammonia, and now you need to cool it down to start over. Once it's cool you can pressurize it again so you can heat it up to use again, but you have to cool it, and that's the crux of the issue. The problem is essentially that everything you do releases waste heat, so you either reject it, or everything continues to heat up until something breaks. Developing useful work from that heat only helps if it helps reject it, but it's more efficient to reject it immediately. A better, more direct way to think about this might be to look at the Seebeck effect. If you have a giant radiator, you could put a Peltier module between it and you GPU cooling loop and generate a little electricity, but that would necessarily also create some waste heat, so you're better off cooling the GPU directly.

You can't easily use low grade heat. However there are workarounds. People are talking like the only radiator design is the one on the ISS. There are other ways to build radiators. It's all about surface area. One way is to heat up a liquid and then spray it openly into space on a level trajectory towards a collecting dish. Because the liquid is now lots of tiny droplets the surface area is huge, so they can radiate a lot of heat. You don't need a large amount of material as long as you can scoop up the droplets the other end of the "pipe" and avoid wasting too much. Maybe small amounts of loss are OK if you have an automated space robot that goes around docking with them and topping them up again.

Harder to direct waste heat in space if you dont have gravity for convection.

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.

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.

It's a minor point but the Earth doesn't radiate all of that heat to equilibrium, that's why we have climate change.

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.

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.

Data centers ultimately need to provide power and remove heat. Solar might be a little easier for power in space, maybe, but heat is an absolute no-go, stop, this will never ever work. You can't engineer your way out of the fact that space is a vacuum.

if the thermal radiation panels have ~3 x the area of the solar panels, the temperature of the satellite can be contained to about 300 K (27 deg C). Ctrl+F:pyramid to find my calculations.

The vacuum is the problem. It might be cold but has terrible heat transfer properties. The area of radiators it would take to dissipate a data center dwarfs absolutely anything we’ve ever sent to orbit

Also solar wind, cosmic rays etc. We don't have perfect shielding for that yet. Cooling would be tricky and has to be completely radiative which is very slow in space. Vacuum is a perfect insulator after all, look how thermos work.

It's not only about destruction. It's also about reliability. Without proper shielding and error correction you're going to have lots and lots of reliability issues and data corruption. And if we're talking about AI and given the current reliability problems of the Nvidia hardware, plus the radiation, plus the difficulty for refrigerating all that stuff on space... That's a big problem. And we still haven't started to talk about the energy generation. I think there's a very interesting use case on edge computing (edge of space, if you wanna make the joke) that in fact some satellites are already doing, were they preprocess data before sending back to Earth. But datacenter-power-level computing is not even near. I have no idea and numbers to back it up, but I feel it would be even easier to set up a Moon datacenter than an orbital datacenter (when talking about that size of datacenter)

Thank you. The waste heat problem is so bad but no one gets around to mentioning the fact that you can't have AI grade chips and space at the same time.

Car-grade inference hardware is fundamentally different from data center-grade inference hardware, let alone the specialized, interconnected hardware used for training (like NVLink or complex optical fabrics). These are different beasts in terms of power density, thermal stress, and signaling sensitivity. Beyond that, we don't actually know the failure rate of the Tesla fleet. I’ve never had a personal computer fail from use in my life, but that’s just anecdotal and holds no weight against the law of large numbers. When you operate at the scale of a massive cluster, "one-in-a-million" failures become a daily statistical certainty. Claiming that because you don't personally see cars failing on the side of the road means they require zero intervention actually proves my original point: people who haven't managed data center reliability underestimate the sheer volume of "rare" failures that occur at scale.

The quoted "1 TW of photovoltaic cells per year, globally" is the peak output, not the average output. They're only about 20% higher peak output in space… well, if you can keep them cool at least.

Does that include all the required radiators to vent heat?

and of course, the continuous opposite boost needed to prevent the heat vent from knocking them out of orbit.

I think this is all ridiculous, to be clear, but re: this problem couldn't the radiators in theory be oriented so that they vent in opposite directions and cancel out any thrust that would be generated?

That's super interesting. STC uses an irradiance of irradiance 1000W/m2, in space it seems like you get closer to 1400W/m2. That's definitely better, but also not enormously better. Seems also like they are rated at 25C, I am certainly not a space engineer but that seems kind of temperate for space where cooling is more of a challenge. Seems like it might balance out to more like 1.1x to 1.3x more power in space?

would you prefer big tech to piss their waste heat into your rivers, soils and atmosphere? or would you prefer them to go to the bathroom upstairs? at some point big tech is in a "damned if you do, damned if you don't" situation...

Now do waste heat.

Here you go: https://news.ycombinator.com/item?id=46862869

The intractable problem is heat dissipation. There is to little matter in space to absorb excess heat. You'd need thermal fins bigger than the solar cells. The satellite's mass would be dominated by the solar panels and heat fins such that maybe 1% of the mass would be usable compute. It would be 1000x easier to leave them on the moon and dissipate into the ground and 100000x easier to just keep making them on earth.

> The intractable problem is heat dissipation. 3 times the area of the heat dissipating surface compared to solar panel surface brings the satellite temp down to 27 deg C (300 K): https://news.ycombinator.com/item?id=46862869 > There is to little matter in space to absorb excess heat. If that were true the Earth would have overheated, molten and turned to plasma long ago. Earth cools by.... radiative cooling. Dark space is 4 K, thats -267.15 deg C or -452.47 deg Fahrenheit. Stefan-Boltzmann law can cool your satellite just fine. > You'd need thermal fins bigger than the solar cells. Correct, my pessimistic calculation results in a factor of 3,... but also Incorrect, there wouldn't be "fins" thats only useful for heat conduction and convection.

The inner planets contain enough mass to create a shell of 1 AU radius with mass of 42 kg/m^2. That sounds like a plausible thickness and density for a sandwich of photovoltaics - GPUs - heat sinks. You don't build a rigid shell of course, you build a swarm of free-floating satellites in a range of orbits. See https://www.aleph.se/Nada/dysonFAQ.html#ENOUGH for numbers.

Is there a credible way to cool a space-based data center on that scale?

You also have all that heat to dissipate....

A former NASA engineer with a PhD in space electronics who later worked at Google for 10 years wrote an article about why datacenters in space are very technically challenging: https://taranis.ie/datacenters-in-space-are-a-terrible-horri... I don't have any specialized knowledge of the physics but I saw an article suggesting the real reason for the push to build them in space is to hedge against political pushback preventing construction on Earth. I can't find the original article but here is one about datacenter pushback: https://www.bloomberg.com/opinion/articles/2025-08-20/ai-and... But even if political pushback on Earth is the real reason, it still seems datacenters in space are extremely technically challenging/impossible to build.

Okay, but a human being represents what, 200 W of power? The ISS has a crew of 3, so that's less than a beefy single user AI workstation at full tilt. If the question is whether it's practical to put 1-2 kW worth of computing power in orbit, the answer is obviously yes, but somehow I don't think that's what's meant by "datacenter in space".

I don't know, 10 years seems reasonable for development. There's not that much new technology that needs to be developed. Cooling and communications would just require minor changes to existing designs. Other systems may be able to be lifted wholesale with minimal integration. I think if there were obstacles to building data centers on the ground then we might see them in orbit within the next ten years. I don't see those obstacles appearing though.

The same things you are saying about data centers in space was said by similar people 10-15 years ago when Elon musk said SpaceX would have a man on Mars in 10-15 years. We have had the tech to do it since the 90's, we just needed to invest into it. Same thing with Elon Musks hyperloop, aka the atmospheric train (or vactrain) which has been an idea since 1799! And how far has Elon Musks boring company come to building even a test loop? Yeah, in theory you could build a data center in space. But unless you have a background in the limitations of space engineering/design brings, you don't truly understand what you are saying. A single AI data center server rack takes up the same energy load of 0.3 to 1 international space station. So by saying Elon musk can reasonable achieve this, is wild to anyone who has done any engineering work with space based tech. Every solar panel generates heat, the racks generate heat, the data communication system generates, heat... Every kW of power generated and every kW of power consumes needs a radiator. And it's not like water cooling, you are trying to radiate heat off into a vacuum. That is a technical challenge and size, the amount of tons to orbit needed to do this... Let alone outside of low earth... Its a moonshot project for sure. And like I said above, Elon musk hasnt really followed through with any of his moonshots.

> A single AI data center server rack takes up the same energy load of 0.3 to 1 international space station. The ISS is powered by eight Solar Array Wings. Each wing weighs about 1,050kg. The station also has two radiator wings with three radiator orbital replacement units weighing about 1,100kg each. That's about 15,000 kg total so if the ISS can power three racks, that's 5,000kg of payload per rack not including the rack or any other support structure, shielding, heat distribution like heat pipes, and so on. Assuming a Falcon Heavy with 60,000 kg payload, that's 12 racks launched for about $100 million. That's basically tripling or quadrupling (at least) the cost of each rack, assuming that's the only extra cost and there's zero maintenance.

> Cooling and communications would just require minor changes to existing designs. "Minor" cooling changes, for a radically different operating environment that does not even have a temperature, is a perfect insulator for conduction and convection, and will actively heat things up via incoming radiation? "Minor" ? Citation very much lacking.

Take the area of solar panels, multiply by 3, thats the area of black body thermal radiation surface. The sattelite will chillax to 27 deg C (300 K): https://news.ycombinator.com/item?id=46862869

if you focus on shedding heat and make it sound like an impossibility, don't be surprised when people describe what it would take.

I don't know what you call minor or major. I know what physics tells us.

Data centers don't do anything other than sit there and turn electricity into heat. They only emit nothing but heat (which could be useful to others in the building).

Google is currently working on AI data centers in space. https://blog.google/innovation-and-ai/technology/research/go...

> A former NASA engineer with a PhD in space electronics who later worked at Google for 10 years wrote an article about why datacenters in space are very technically challenging It's curious that we live in a world in which I think the majority of people somehow think this ISN'T complicated. Like, have we long since reached the point where technology is suitably advanced to average people that it seems like magic, where people can almost literally propose companies that just "conjure magic" and the average person thinks that's reasonable?

It's just the thought process that comes with shallow understanding: "I can buy a server" "We can put things in space" "What do you mean I can't get a server in space?!"

"Technically challenging", a nice way to say "impossible"

No, rockets landing themselves is just controlling the mechanism you use to have them take off, and builds on trust vectoring technology from 1970s jet fighters based on sound physics. Figuring out how to radiate a lot of waste heat into a vacuum is fighting physics. Ordinarily we use a void on earth as a very effective _insulator_ to keep our hot drinks hot.

> Figuring out how to radiate a lot of waste heat into a vacuum is fighting physics. Radiators should work pretty well, and large solar panels can do double duty as radiators. Also, curiously, newer GPUs are developed to require significantly less cooling than previous generations. Perhaps not so coincidentally?

Well there lies the rub, solar panels already need their own thermal radiators when used in space ...

> And not having to buy land and water to power/cool it. It's interesting that you bring that up as a benfit. If waterless cooling (i.e. closed cooling system) works in space, wouldn't it work even better on Earth?

You need to understand more of basic physics and thermodynamics. Fighting thermodynamics is a losing race by every measure of what we understand of the physical world.

> Fighting thermodynamics is a losing race The great thing about your argument is that it can be used in any circumstance! Cooling car batteries, nope can't possibly work! Thermodynamics! Refrigerator, are you crazy? You're fighting thermodynamics! Heat pump! Haah thermodynamics got you.