Comment by elamje
1 day ago
I was talking to someone about this the other day. I was part of a team at NASA that developed a cooling system for the ISS and this whole premise makes no sense to me.
1. Getting things to space is incredibly expensive
2. Ingress/egress are almost always a major bottleneck - how is bandwidth cheaper in space?
3. Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire teams at NASA dedicated to special hardware for this.
4. Gravity and atmospheric pressure actually do wonders for easy cooling. Heat is not dissipated in space like we are all used to and you must burn additional energy trying to move the heat generated away from source.
5. Energy production will be cheaper from earth due to mass manufacturing of necessary components in energy systems - space energy systems need novel technology where economies of scale are lost.
Would love for someone to make the case for why it actually makes total sense, because it’s really hard to see for me!
It sounds hard but it shouldn't not make sense.
1. Solving cost of launching mass has been the entire premise of SpaceX since day one and they have the track record.
2. Ingress/egress aren't at all bottlenecks for inferencing. The bytes you get before you max out a context window are trivial, especially after compression. If you're thinking about latency, chat latencies are already quite high and there's going to be plenty of non-latency sensitive workloads in future (think coding agents left running for hours on their own inside sandboxes).
3. This could be an issue, but inferencing can be tolerant to errors as it's already non-deterministic and models can 'recover' from bad tokens if there aren't too many of them. If you do immersion cooling then the coolant will protect the chips from radiation as well.
4. There is probably plenty of scope to optimize space radiators. It was never a priority until now and is "just" an engineering problem.
5. What mass manufacture? Energy production for AI datacenters is currently bottlenecked on Siemens and others refusing to ramp up production of combined cycle gas turbines. They're converting old jet engines into power plants to work around this bottleneck. Ground solar is simply not being considered by anyone in the industry because even at AI spending levels they can't store enough power in batteries to ride out the night or low power cloudy days. That's not an issue in space where the huge amount of Chinese PV overproduction can be used 24/7.
> There is probably plenty of scope to optimize space radiators. It was never a priority until now and is "just" an engineering problem.
It's a physics problem, as others pointed out, but even if we take it as another "just an engineering problem", have a look at the Hyperloop. Which is similarly just a long vacuum tube, and inside is like an air hockey table, not that big a deal, right?...
Musk's companies never tried to make the hyperloop, they never even started on it. SpaceX is a bit different.
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3. There are WAY more things to get corrupted on a computer system than tokens. And non-determinism does NOT mean it’s tolerant to faults. Random values are intentionally introduced at the right moment for LLMs.
> There is probably plenty of scope to optimize space radiators. It was never a priority until now and is "just" an engineering problem.
Well, it's a physics problem. The engineering solution is possibly not cost efficient. I'd put a lot of money that it isn't.
That bit reminded me of someone who wanted us to design a patch the size of a small postage stamp, at most 0.2mm thick, so you could stick on products. It was to deliver power for two years of operation, run an LTE modem, a GNSS receiver, an MCU, temperature and humidity sensor and would cost $0.10. And it would send back telemetry twice per day.
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Not only is it not cost-effective, it's pointless (in this context).
Radiators works almost just as well on Earth. Convection and conduction more than make up the difference.
What makes you so sure? SpaceX already has thousands of 6 kW networking racks flying around in LEO and they dissipate their heat just fine, and are plenty cost-effective. You think they can't do any better than that with a new design specifically optimized for computing rather than networking?
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“just an engineering problem”
Sounds a bit like that Dilbert where the marketing guy has sold a new invisible computer and is telling the engineers to now do their job and actually make it.
> It sounds hard but it shouldn't not make sense.
It does not make sense.
The question isn't "can you mitigate the problems to some extent?", it's "can you see a path to making satellite data centers more appealing than terrestrial?"
The answer is a flat out "no," and none of your statements contradict this.
Terrestrial will always be better:
1. Reducing the cost of launches is great, but it will never be as cheap as zero launches.
2. Radio transmissions have equally high bandwidth from Earth, but fiber is a better network backbone in almost every way.
3. Radiation events don't only cause unpredictable data errors, they can also cause circuit latch-ups and cascade into system failure. Error-free operation is still better in any case. Earth's magenetosphere and atmosphere give you radiation shielding for free, rad-hard chips will always cost more than standard (do they even exist for this application?), and extra shielding will always cost more than no shielding.
4. On Earth you can use conduction, convection, AND radiation for cooling. Space only gets you marginally more effective radiation.
5. Solar is cheaper on the ground than in space. The increase in solar collection capability per unit area in space doesn't offset the cost of launch: you can get 20kW of terrestrial solar collection for around the price of a single 1U satellite launch, and that solar production can be used on upgraded equipment in the future. Any solar you put on a satellite gets decommissioned when the inference hardware is obsolete.
And this ignores other issues like hardware upgrades, troubleshooting, repairs, and recycling that are essentially impossible in space, but are trivial on the ground.
> Solving cost of launching mass has been the entire premise of SpaceX since day one and they have the track record.
They have to solve for it being cheaper to launch and operate in space vs building and operating a datacenter with its own power generation on Earth.
My lord a sensible comment her. A hearty upvote.
It really isn't. It's plainly incorrect and ignorant of the actual problems.
I have no expertise is this area, so I'm not getting into whether or not this idea makes sense.
That being said, this statement strikes me as missing the point:
> Solving cost of launching mass has been the entire premise of SpaceX since day one and they have the track record.
As I understand it, SpaceX has a good track record of putting things into space more cost effectively than other organisations that put things into space.
That is not the benchmark here.
It doesn't matter if Musk can run thousands of data centres in space more cost effectively than (for example) NASA could. It matters whether he can do it more cost effectively than running them on earth.
The cost of "launching" mass on Earth is not zero, though.
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I don’t think that statement was missing the point. As you point out, what matters is the total cost of ownership of the system. The cost of launching mass into space today isn’t the only reason terrestrial data centers are more cost effective today, but it’s the main one. If you make it cheap enough to send giant solar arrays and radiators to space, the other costs of operating in space may start to look like a small price to pay to eliminate the need for inputs like land and batteries.
> Would love for someone to make the case for why it actually makes total sense, because it’s really hard to see for me!
Elon musk has a history of making improbable-sounding promises (buy a tesla now, by 2018 it will be a self-driving robotaxi earning money while you sleep, humanoid robots, hyperloops).
The majority of these promises have sounded cool enough to enough people that the stock associated with him (TSLA) has made people literal millionaires just by holding onto the stock, and more and more people have bought in and thus have a financial interest in Musk's ventures being seen in a good light (since TSLA stock does not go up or down based on tesla's performance, it goes up or down based on the vibes of elon musk. It is not a car company stock, it is an elon vibes check).
The thing he's saying now pattern matches to be pretty similar, and so given Musk's goal is to gain money, and he gains money by TSLA and SpaceX stock going up, this makes perfect sense as a thing to say and even make minor motions towards in order to make him richer.
People will support it too since it pattern matches with the thing prior TSLA holders got rich off of, and so people will want to keep the musk vibes high so that their own $tsla holdings go to the moon.
Make sense now?
The story here is even simpler. SpaceX is going public this year. Elon made a monumentally shitty investment in Twitter and then poured a stupid amount of money into xAI at the peak of the cycle. By having SpaceX buy xAI, he gets to swap worthless shares in that company for more SpaceX liquidity. Simple as that.
Exactly, and there needs to be some economic justification for a giant rocket. There is no money to be made by going to Mars, and AI data centers in space could attract investors (who are just riding the data center hype).
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Really seems silly to think that the guy with $800 billion is spending most of his time maximizing his money.
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Yeah, but landing a rocket backwards also sounded very improbable to me, yet it looks pretty cool now.
Also people made fun of tesla that it will never be able to compete with the big carmakers. Now I would rather have some stocks in tesla than holding on to volkswagen.
I wouldn’t be so sure about Tesla stock. Tesla has only weathered 1 market downturn cycle and that was when it was a very different company. The company has thus far had access to plentiful capital since the Model S started being delivered.
Famous investors like to repeat the quote that “when the tide goes out, that’s when we find out who’s wearing no pants.” When Tesla actually weathers its first market downturn is when we find out how much investors interest is maintained When investment dollars are scarce.
Oh no! He promised my car would be self driving in 2018 but it took until 2026 before that was true.
How dare he not have accurately predicted when one of the hardest technical problems in history is solved?
“At SpaceX we specialize in making the impossible merely late.” -Elon
Regarding 3, they're almost certainly thinking of putting these in SSO where the radiation environment isn't too much worse than you see on the ISS. If they were going to go outside the Van Allen belts it would be a different story.
The whole AI bubble makes way more sense if you model it not as rational economic activity, but rather as the actions of a rogue AI slowly taking over our institutions and redirecting them towards its goals. Data centers in space make no sense economically, but think of how survivable the rogue AI will be once we build those orbiting data centers! (I am joking about this, but it's weird that my logic makes sense.)
> 5. Energy production will be cheaper from earth
Sun-synchronous orbit means solar panels collect the same amount 24/7. I guess that's the #1 benefit. Cheap energy.
Read the whole sentence. He’s talking about the cost to make solar panels that can be deployed in space, not the efficacy of said panels.
Added some math on my comment that outlines the boundaries of economics of this considering most of what you mentioned.
for the chips to both be radiation hardened and as powerful as our current chips they'd need to be massive. There's a reason the mars rover uses a PowerPC G3
It doesn't make sense. It is just Musk trying to pump up SpaceX valuation before the IPO.
>Ingress/egress are almost always a major bottleneck - how is bandwidth cheaper in space?
Free space optics are much faster than data to/from the ground. If the training workloads only require high bandwidth between sats, this isn’t a real issue.
> Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire teams at NASA dedicated to special hardware for this.
They don't do RAD hardening on chips these days, they just accept error and use redundant CPUs.
There are apparently rad-hard DDR4 chips these days so this is patently false. SpaceX used to talk a lot about substituting rad-hard components with triple redundant regular x86 years ago, that's true.
I think I've also seen someone mention that the cost and power benefit of substituting rad-hard chips with garden variety wean off fast once the level of redundancy goes up, and also it can't handle deep space radiations that just kill Earthbound chips rather than partially glitching them.
You are confidently incorrect. Even Starlink uses rad-hardened CPUs. Redundant error correction is only really an option on launch hardware that only spends minutes in space.
Note that on modern hardware cosmic rays permanently disable circuits, not mere bitflips.
> You are confidently incorrect.
No, he's not. Dragon is using CotS, non rad-hardened CPUs. And it's rated to carry humans to space.
> AWST: So, NASA does not require SpaceX to use radiation-hardened computer systems on the Dragon?
John Muratore: No, as a matter of fact NASA doesn't require it on their own systems, either. I spent 30 years at NASA and in the Air Force doing this kind of work. My last job was chief engineer of the shuttle program at NASA, and before that as shuttle flight director. I managed flight programs and built the mission control center that we use there today.
On the space station, some areas are using rad-hardened parts and other parts use COTS parts. Most of the control of the space station occurs through laptop computers which are not radiation hardened.
> Q: So, these flight computers on Dragon – there are three on board, and that's for redundancy?
A: There are actually six computers. They operate in pairs, so there are three computer units, each of which have two computers checking on each other. The reason we have three is when operating in proximity of ISS, we have to always have two computer strings voting on something on critical actions. We have three so we can tolerate a failure and still have two voting on each other. And that has nothing to do with radiation, that has to do with ensuring that we're safe when we're flying our vehicle in the proximity of the space station.
I went into the lab earlier today, and we have 18 different processing units with computers in them. We have three main computers, but 18 units that have a computer of some kind, and all of them are triple computers – everything is three processors. So we have like 54 processors on the spacecraft. It's a highly distributed design and very fault-tolerant and very robust.
[1] - https://aviationweek.com/dragons-radiation-tolerant-design
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Where did you hear this?
When they talk about "space" they are, right now, talking about the moon. Which has some gravity. They are putting the data centers on the moon. And the satellites are lunar satellites not earth-orbit satellites. Lonestar physical data center payload landed on the moon in Feb 2025 and Sidus space developing the lunar satellites.
They are not. xAI/SpaceX is talking about millions of satellites in sun-synchronous orbit.
Yeah, the cost of doing it on the moon would be even more astronomical. Then there also is the three second of round-trip latency to consider (ca. 2.6 s just the signal, but processing adds a bit more).