So like I don't get to use my degree except to tutor kids and answer physics questions and the like, so indulge me for a second because this doesn't make much sense to me. So like the endgame is to create a new Pryor, OK facility in space, right? It doesn't make sense if we're not shipping something that's about the same as what you can build on Earth.
Epoch.AI says that this facility has 100,000 TPU chips, eats 370 megawatts of electricity, but designed to get rid of up to 480 megawatts of heat. Sun power is 1.36 kW/m^2, which is something like 7 megawatts per football field (assuming ~5000 m^2), but you have to put up something like 3-5x that because solar panels are only 20-30% efficient, right? Assume that you can arrange it so that the solar panels are one side, the radiators on the other, you can maybe get away with only 300-400 football fields maybe? So like 1.5 million m^2 or 1.2 km wide, right? At LEO, 650 km, you have (1.2km)/(650 km) * 180 degrees/pi is 0.11 degrees or 6.6 arcminutes of visual size. The moon is only like 30 arcminutes. And the paper talks about how they're going to not do one big monolithic construction but an oval of fridge-sized objects separated out 2-3 times this size -- so like I don't see how you get another Pryor, OK size data center in LEO without basically having it look like a second, smaller moon flying across the sky 10 times per day.
And if this were a wildly successful idea are we talking about having like 5-10 of them, a few for each big frontier lab? This just sounds like we're talking about the most profound shift to our night skies since we started having to deal with light pollution in our cities.
There's a lot of different designs besides this one.
So far as I can work out, literally all of the plans are bad. The "why" varies, but they're all bad.
I'm too tired to double check your maths, so I will assume correct: one likely difference even for this plan is a terminator following sun-synchronous orbit, which means you'll only see it twice a day despite the orbital period being about 90-100 minutes, and when you see it will be specifically at sunrise and sunset.
Visibility is also a question of reflection, not just size. Terminator following orbits are worse than normal satellites, because one of the tricks for reducing e.g. Starlink visibility is to tilt them as they cross the terminator and you can't do that if they're always on the terminator.
The SpaceX plans (a million small ones) becomes a glitter band in some parts of the sky and will appear visually contiguous in other parts, though I need to double check my maths and assumptions about visibility given this happens during sunrise and sunset so the sky itself is pretty bright.
I think there are at least a few problems with the math’s assumptions:
1) Don’t the radiators need to have more surface area than the solar? (Unless the chips run very hot.)
2) The datacenter will have the pesky earth between it and the sun some fraction of the time, and have to either shut down or run off batteries. ~50%, assuming LEO, right? If you leave LEO, then the latency sucks, so they’re training-only clusters. At 50% the solar doubles and you need 370 megawatt hours per hour of darkness, or you run the machines 50% of the time, rebooting for each orbit. If you make the orbit shorter (so you can have smaller batteries), then they wear out faster. The batteries also emit heat. Plus, you need to double the solar so they charge while the workload is running.
3) How do they cope with cosmic rays? The standard approach is still to duplicate or triplicate all computation, or use larger/slower processes, right?
The obvious answer to each question makes the engineering design at least twice as dumb, and they stack. There are many other problems like these.
The radiators are what need to be very hot. IIRC it works out to, order of magnitude, a similar area to the solar panels. These satellites would likely be placed in SSO, a polar orbit that precesses at the same rate that the Earth orbits the sun. So the fraction of time they see the sun would be very high. Cosmic rays are a little bit of an unknown, we don't know exactly how a commercial GPU running an LLM deals with cosmic ray radiation. I think the intuition is that it would be very little because a single bit flip in that vast array of matrix math and many times its result might not actually change any activations anyway.
I think the big problem with the idea is that GPUs have a failure rate and even if they didn't, they become obsolete. Most orbital DC plans are really more like flying server racks with no servicing in orbit. So when the GPUs die the satellite is a flying brick. All the power equipment, all the thermal equipment, all the comms equipment now depreciates at the same rate as GPUs. Very different economics from terrestrial DCs. And that's all assuming that you can launch everything up there quite efficiently. And the satellites take time to engineer but DCs are a more known quantity.
>1) Don’t the radiators need to have more surface area than the solar? (Unless the chips run very hot.)
to generate 1KW you need 5m2 of solar panels. And black body radiation of 1.5m2 at 70 C is 1KW.
A unit with 1 GPU, 2m2 radiator and 5m2 solar panels is say 20kg. At promised Starship price well under $100/kg, that is less than $2000 to put that unit into orbit. That is much cheaper than $15000 per 1KW of a ground-based datacenter, especially when additionally factoring in [expensive and climate change causing] ground-based electricity vs. free electricity in space once you launched the unit with its solar panels.
Add political opposition on Earth, Iranian drones hitting datacenters, various laws (i.e. costs) that your ground-based datacenter is subject too ... the space starts to look like a very cozy place for a datacenter :)
at current prices it's above $1000/kg to orbit, and we're just conveniently ignoring all of the operational constraints of a completely unmanned datacenter upon which you can perform no maintenance.
What do you do when a micrometeorite causes pinprick leaks in your radiator loop?
is LEO sufficiently shielded from cosmic and solar radiation?
nobody is building real datacenters in space at $1000/kg - at that price the cost is comparable to ground-based and thus no big point. The explosion will start at $100/kg when as i mentioned the base cost would beat ground-based almost 10x, and thus would allow for the additional costs (with total cost still beating ground-based) of all the additional issues/concern you and the others usually mention in this context.
4 years ago we had the ChatGPT moment and notice how civilizational change has been accelerating since then. In a few years we're gong to have the seemingly profound Starship moment. Back at the time it was obvious, i may be said it is even here, that Starship low price will cause explosion of amount of launched payloads and a technological revolution as a result, yet it wasn't clear what kind of payloads it would really be. And now we have the AI - Starship and AI are basically ideally dove-tail each other. Two revolutionary technologies accelerating each other - Strarship lowering deployment cost and removing other obstacles for AI while AI providing guaranteed massive scale launch market for Starship - that will be a thing to watch (or participate if you're lucky :)
As per another of my comments, Alphabet, applying learning curves arbitrarily far into the future, recon it will take SpaceX launching 370,000 tons to LEO to make the costs come down enough to be worth it: <a href="https://arxiv.org/pdf/2511.19468" rel="nofollow">https://arxiv.org/pdf/2511.19468
That's not even $100/kg, that's $200/kg.
Even my bull case puts that ($200/kg) 10 years off, which is so far away it lacks relevance just because compute and AI models move so much faster than that timescale; my bear case says that's about 45 years off.
Always account for how over-optimistic Musk's public timelines are. Starship has only just a few days ago managed its first circular orbit, but when he first talked about it:
The basic game plan is like we're going to send a mission to Mars with every Mars opportunity from 2018 onwards. So and they occur approximately every 26 months. So you know, we're establishing cargo flights to Mars that people can count on for cargo.
1) Not even if the PV was 100% efficient, which is impossibly good.
Imagine this side on, as a T-shape: the top bar is the PV, sunlight coming downwards, and because of that only one side is illuminated. The radiator is the vertical bar, in shadow, but crucially it's two-sided, so 1m^2 of material is 2m^2 of surface. If they're the same area of material, thanks to that 2:1 advantage the radiator has naturally, this would only need to run at 58°C: <a href="https://www.wolframalpha.com/input?i=%281361+watt+%2F+%281*σ*2m%5E2%29%29%5E%281%2F4%29" rel="nofollow">https://www.wolframalpha.com/input?i=%281361+watt+%2F+%281*σ...
(Adjust as you prefer for power, area, emissivity is 1 here which isn't possible either but realistic radiators are more like 0.8-0.95 and even 0.8 only raises the above to 77°C)
One of the bigger problems for radiator size is putting them in LEO. Earth is warm and a big fraction of the sky at that altitude. Less of a problem as you get hotter, because radiated power is proportional to the fourth power of temperature in Kelvin, but the closer you operate to Earth's temperature the worse it is.
However, one of the things I am trying to sort out for the blog post is what happens exactly, as a function of temperature, if you just put this all on the ground, because down here you have convection as well as radiation; I'm sure I've seen someone do this and their conclusion was that any radiator good enough to work in space will actually work better on the ground for realistic operating temperatures.
If that rings a bell for anyone else, and you can remember a link to who already worked that out, please let me know :)
2) Not necessarily, but different people pursuing this have different plans: that's why I said the thing about terminator-following sun synchronous orbit, it's a special class of orbits that are always on the edge between day and night at all times.
If you don't do use that class of orbit, then yes, you lose half the supposed benefit on the power front.
3) The current plans seem to be "wing it". Given how resilient LLMs are to noise, this might even work.
you're correct. this video was a pretty good visual exploration of some of it: <a href="https://www.youtube.com/watch?v=_qpdUNMt2yg" rel="nofollow">https://www.youtube.com/watch?v=_qpdUNMt2yg
my personal understanding is that in-orbit compute is perfectly practical up to some obvious limits like the ones you describe. a few reasonably sized clusters up there (tens of kilowatts) doing high priority processing jobs paid by the flop is a great idea. localized compute on existing satellites already does some of this but some earth observation company being able to rapidly scale up image processing for an hour is a great option to have. the really big stuff is just a fantasy.
To take it to more absurd levels, further out and spread out we could create a mesh like structure and throw a bit (a tiny bit) of a shade on the planet and fight global warming.
Starship’s economics will make such projects inevitable, if it’s not data centers it will be something else. Ideally, the solar panels will be efficient enough to minimize albedo.
A facility in space will likely have better uptime then a terrestrial facility with lower costs for disaster mitigation/insurance. The economics are surprisingly close when you do the back of the napkin kg math, but you can mass-produce orbital data centers in a way that’s not possible for terrestrial facilities.
Granted, the same pitch could have been made for orbital telecommunications vs terrestrial wires… that bet hasn’t paid off yet.
crdrost · · focus · HN ↗
Epoch.AI says that this facility has 100,000 TPU chips, eats 370 megawatts of electricity, but designed to get rid of up to 480 megawatts of heat. Sun power is 1.36 kW/m^2, which is something like 7 megawatts per football field (assuming ~5000 m^2), but you have to put up something like 3-5x that because solar panels are only 20-30% efficient, right? Assume that you can arrange it so that the solar panels are one side, the radiators on the other, you can maybe get away with only 300-400 football fields maybe? So like 1.5 million m^2 or 1.2 km wide, right? At LEO, 650 km, you have (1.2km)/(650 km) * 180 degrees/pi is 0.11 degrees or 6.6 arcminutes of visual size. The moon is only like 30 arcminutes. And the paper talks about how they're going to not do one big monolithic construction but an oval of fridge-sized objects separated out 2-3 times this size -- so like I don't see how you get another Pryor, OK size data center in LEO without basically having it look like a second, smaller moon flying across the sky 10 times per day.
And if this were a wildly successful idea are we talking about having like 5-10 of them, a few for each big frontier lab? This just sounds like we're talking about the most profound shift to our night skies since we started having to deal with light pollution in our cities.
ben_w · · focus · HN ↗
So far as I can work out, literally all of the plans are bad. The "why" varies, but they're all bad.
I'm too tired to double check your maths, so I will assume correct: one likely difference even for this plan is a terminator following sun-synchronous orbit, which means you'll only see it twice a day despite the orbital period being about 90-100 minutes, and when you see it will be specifically at sunrise and sunset.
Visibility is also a question of reflection, not just size. Terminator following orbits are worse than normal satellites, because one of the tricks for reducing e.g. Starlink visibility is to tilt them as they cross the terminator and you can't do that if they're always on the terminator.
The SpaceX plans (a million small ones) becomes a glitter band in some parts of the sky and will appear visually contiguous in other parts, though I need to double check my maths and assumptions about visibility given this happens during sunrise and sunset so the sky itself is pretty bright.
hedora · · focus · HN ↗
1) Don’t the radiators need to have more surface area than the solar? (Unless the chips run very hot.)
2) The datacenter will have the pesky earth between it and the sun some fraction of the time, and have to either shut down or run off batteries. ~50%, assuming LEO, right? If you leave LEO, then the latency sucks, so they’re training-only clusters. At 50% the solar doubles and you need 370 megawatt hours per hour of darkness, or you run the machines 50% of the time, rebooting for each orbit. If you make the orbit shorter (so you can have smaller batteries), then they wear out faster. The batteries also emit heat. Plus, you need to double the solar so they charge while the workload is running.
3) How do they cope with cosmic rays? The standard approach is still to duplicate or triplicate all computation, or use larger/slower processes, right?
The obvious answer to each question makes the engineering design at least twice as dumb, and they stack. There are many other problems like these.
sobellian · · focus · HN ↗
I think the big problem with the idea is that GPUs have a failure rate and even if they didn't, they become obsolete. Most orbital DC plans are really more like flying server racks with no servicing in orbit. So when the GPUs die the satellite is a flying brick. All the power equipment, all the thermal equipment, all the comms equipment now depreciates at the same rate as GPUs. Very different economics from terrestrial DCs. And that's all assuming that you can launch everything up there quite efficiently. And the satellites take time to engineer but DCs are a more known quantity.
trhway · · focus · HN ↗
to generate 1KW you need 5m2 of solar panels. And black body radiation of 1.5m2 at 70 C is 1KW.
A unit with 1 GPU, 2m2 radiator and 5m2 solar panels is say 20kg. At promised Starship price well under $100/kg, that is less than $2000 to put that unit into orbit. That is much cheaper than $15000 per 1KW of a ground-based datacenter, especially when additionally factoring in [expensive and climate change causing] ground-based electricity vs. free electricity in space once you launched the unit with its solar panels.
Add political opposition on Earth, Iranian drones hitting datacenters, various laws (i.e. costs) that your ground-based datacenter is subject too ... the space starts to look like a very cozy place for a datacenter :)
eutropia · · focus · HN ↗
What do you do when a micrometeorite causes pinprick leaks in your radiator loop?
is LEO sufficiently shielded from cosmic and solar radiation?
trhway · · focus · HN ↗
4 years ago we had the ChatGPT moment and notice how civilizational change has been accelerating since then. In a few years we're gong to have the seemingly profound Starship moment. Back at the time it was obvious, i may be said it is even here, that Starship low price will cause explosion of amount of launched payloads and a technological revolution as a result, yet it wasn't clear what kind of payloads it would really be. And now we have the AI - Starship and AI are basically ideally dove-tail each other. Two revolutionary technologies accelerating each other - Strarship lowering deployment cost and removing other obstacles for AI while AI providing guaranteed massive scale launch market for Starship - that will be a thing to watch (or participate if you're lucky :)
ben_w · · focus · HN ↗
That's not even $100/kg, that's $200/kg.
Even my bull case puts that ($200/kg) 10 years off, which is so far away it lacks relevance just because compute and AI models move so much faster than that timescale; my bear case says that's about 45 years off.
Always account for how over-optimistic Musk's public timelines are. Starship has only just a few days ago managed its first circular orbit, but when he first talked about it:
- Musk, 2016: <a href="https://elonmuskarchive.org/fr/video/code-conference-2016-06-01" rel="nofollow">https://elonmuskarchive.org/fr/video/code-conference-2016-06...jeezfrk · · focus · HN ↗
This is all wildly short term mania.
trhway · · focus · HN ↗
ben_w · · focus · HN ↗
Imagine this side on, as a T-shape: the top bar is the PV, sunlight coming downwards, and because of that only one side is illuminated. The radiator is the vertical bar, in shadow, but crucially it's two-sided, so 1m^2 of material is 2m^2 of surface. If they're the same area of material, thanks to that 2:1 advantage the radiator has naturally, this would only need to run at 58°C: <a href="https://www.wolframalpha.com/input?i=%281361+watt+%2F+%281*σ*2m%5E2%29%29%5E%281%2F4%29" rel="nofollow">https://www.wolframalpha.com/input?i=%281361+watt+%2F+%281*σ...
(Adjust as you prefer for power, area, emissivity is 1 here which isn't possible either but realistic radiators are more like 0.8-0.95 and even 0.8 only raises the above to 77°C)
One of the bigger problems for radiator size is putting them in LEO. Earth is warm and a big fraction of the sky at that altitude. Less of a problem as you get hotter, because radiated power is proportional to the fourth power of temperature in Kelvin, but the closer you operate to Earth's temperature the worse it is.
However, one of the things I am trying to sort out for the blog post is what happens exactly, as a function of temperature, if you just put this all on the ground, because down here you have convection as well as radiation; I'm sure I've seen someone do this and their conclusion was that any radiator good enough to work in space will actually work better on the ground for realistic operating temperatures.
If that rings a bell for anyone else, and you can remember a link to who already worked that out, please let me know :)
2) Not necessarily, but different people pursuing this have different plans: that's why I said the thing about terminator-following sun synchronous orbit, it's a special class of orbits that are always on the edge between day and night at all times.
If you don't do use that class of orbit, then yes, you lose half the supposed benefit on the power front.
3) The current plans seem to be "wing it". Given how resilient LLMs are to noise, this might even work.
[deleted] · · focus · HN ↗
[deleted]
devindotcom · · focus · HN ↗
my personal understanding is that in-orbit compute is perfectly practical up to some obvious limits like the ones you describe. a few reasonably sized clusters up there (tens of kilowatts) doing high priority processing jobs paid by the flop is a great idea. localized compute on existing satellites already does some of this but some earth observation company being able to rapidly scale up image processing for an hour is a great option to have. the really big stuff is just a fantasy.
aaron695 · · focus · HN ↗
[dead]
Keyframe · · focus · HN ↗
trhway · · focus · HN ↗
a formation in the shape of the client's logo.
justinclift · · focus · HN ↗
Maybe even a new "Shade as a Service" business model. ;)
MisterKent · · focus · HN ↗
lumost · · focus · HN ↗
A facility in space will likely have better uptime then a terrestrial facility with lower costs for disaster mitigation/insurance. The economics are surprisingly close when you do the back of the napkin kg math, but you can mass-produce orbital data centers in a way that’s not possible for terrestrial facilities.
Granted, the same pitch could have been made for orbital telecommunications vs terrestrial wires… that bet hasn’t paid off yet.
sjs382 · · focus · HN ↗
Say more about that