Our Project Suncatcher prototype satellite is in orbit
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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.
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.
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.
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: 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.
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.
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 :)
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.
a formation in the shape of the client's logo.
Maybe even a new "Shade as a Service" business model. ;)
Capacity factor of terrestrial solar panel: 23%
Retail cost per watt for terrestrial panel: under 45c
Manufacturing cost per watt of space grade solar panel: up to $450
Annual performance degradation of terrestrial solar panel: under 0.5%
That of space-grade solar panel: up to 2%
Life span of terrestrial panel: about 2x that of space panel.
Total difference in cost per watt feeding a DC load in space vs on land: about x400
And that's ignoring launch costs. It makes absolutely zero sense. And given the scale of production and investment in manufacturing, terrestrial is likely to stretch even further ahead in the cost stakes.
Where did this number come from, and why is it literally 1000x more than the Earth version?
I can totally believe the cost of the ISS panels was in that ballpark, but if we're talking about putting megawatts of these things in orbit, economics of scale will very quickly come into play.
Best cost to orbit I am seeing is $1500/kg. A GPU rack is ~1500kg. Let’s imagine you can take a terrestrial data center rack, no scaffolding, solar panels, radiators, radios, propellant, or propulsion. Fly it into orbit, kick it out the airlock, and let it work through magic. That’s $2.2 million to get into position.
Industrial power rates are cheap, say $.10/kwh, but pretend you sign terrible deals, and it costs you $.30/kwh to run and cool a terrestrial GPU rack. A 150kw unit will then be (150x24x365x.3) =$394k/year.
You can operate the terrestrial version for 5.7 years before the two hit parity.
They're projecting the learning curve, that the more you do it the cheaper it gets, continues arbitrarily far.
However, they recon it will take SpaceX launching 370,000 tons to LEO to make the costs come down enough to be worth it: https://arxiv.org/pdf/2511.19468
Even my bull case put that 10 years off, which is so far away it lacks relevance just because tech moves so much faster than that timescale; my bear case says that's about 45 years off.
BUT it doesn't need to be cheaper for there to be value. Its much harder to shoot down a space GPU farm than a terrestrial one. And its closer to space assets which might want it for targeting during times of war.
Not by as much as you may hope. Getting a rocket up to altitude is much, much easier than getting one to orbital speed:
Hitting satellites in orbit is still hard, but ASAT was demonstrated (albeit the target was designed for the test) by the USSR no later than 1968, and on a more arbitrary (end of life) satellite by the USA no later than 1985: https://en.wikipedia.org/wiki/Anti-satellite_weapon#List_of_...
The severity of one single missile depends on the orbital configuration; I'm expecting everyone to declare "we have adjusted our strategic priorities elsewhere" (i.e. "this was a bad idea") well before there's a relevant quantity of them.
Given how cheap laser welding has become, I also foresee ground-to-orbit lasers being credible. They still need quite a large aperture and corrective optics, but that's had known solutions for a while now thanks to astronomy.
> And its closer to space assets which might want it for targeting during times of war.
Not so far as I can see. If you want really low-latency you have edge compute on the weapon systems themselves; otherwise you use the existing satellite comms (e.g. Starlink) to just talk to something hardened outside weapons range.
5 years is a standard depreciation cycle for hardware, but plenty of machines last longer than that, but these satellites will not. On top of that, power distribution, cooling etc in the data centers is a huge percentage of cost and lasts much longer than 5 years.
If you think you can make a space air conditioner for less than a terrestrial one, I have a bridge to sell you.
I've actually got to finish working on that blog post about why this is all a terrible idea; there are many different proposals for how this will work, and they all suck.
Starlink satellites already use silicon solar cells, since they too are cost sensitive and don't have long lifespans:
https://starlink.com/public-files/Starlink_Approach_to_Satel...
On the Starlink V2 mini satellite, we predict that approximately 5% of the mass of the entire satellite could survive reentry. The biggest contributor (~90% of the surviving mass) is silicon from the solar cells, which has a high melting point...
[1] https://www.cell.com/joule/fulltext/S2542-4351(26)00362-4
Someone else said the facility needs 370MW. Great, because SMR designs provide 470MW. That’s 100MW excess, given for free to locals to entice them to support the project. That can power 40k homes, easily. People object to these projects partly because their bills go up? Cool, those bills disappear now.
But no, I guess we’re creating massive arrays in space and polluting the night sky forever.
The AI industry spends crazy money to reduce latency and increase density. The act of placing resources in space, to be used by people on earth, only increases latency, and reduces density. The performance metrics are ops/power/space/$, not G ratings, unless its being validated for flight.
Also: low Earth orbit is already pretty low latency. A lot of people’s intuitions about space latency are from when satellite internet was based out of distant geosynchronous satellites, but even that is probably just fine for most inference workloads.
150kw design Launch on 4000kg is 4 million. 150kw solar Radiator Electronics
20/watt is 3 million. We are above your budget.
One of the "holy grail" things the military has wanted for a long time is to be able to treat a satellite not just like a bent pipe repeater but to do active signal processing and data processing such as for communication between disparate air and ground, naval units.
What do you need to distill a 24/7 stream of everything on Earth in roughly 1m^3 voxels into data like humans and vehicles? Bearing in mind the data torrent is gigantic and can't always be reliably downlinked: co-orbital AI.
I think it’s somewhat impressive they got it into orbit quickly since surely a year ago this wasn’t an earnest idea, and I think it’ll be interesting to see the affects of space on high end chips and connectivity fabric.
But also I agree that this just doesn’t make sense from a performance standpoint.
I was trying to rack my head for any possible way this made sense and was coming up empty. Normally i mistrust conspiracy theories like this, but its the only explanation that seems remotely plausible.
Google's first Suncatcher orbital data center test launches October 1 - https://news.ycombinator.com/item?id=49837350 - Sept 2026 (96 comments)
Google’s Project Suncatcher to put ML infrastructure in space - https://news.ycombinator.com/item?id=49830606 - Sept 2026 (551 comments)
All of that said, I'm skeptical we'll see this in a big way any time soon.
When you add in the VRT and the QML (even not including the ZB-PRP 5) you get far lower than what a naive USP calculation gets you. Horner Weisenbach talked about this recently on their blog.
They did not even attempt to solve the main issues: energy and heat management. The GPUs can work only for 15 minutes and are cooled by a phase change material that then slowly sheds the heat.
Three launches from one company is unusual though.
[0]: https://en.wikipedia.org/wiki/2025_in_spaceflight#Orbital_la...
[1]: https://en.wikipedia.org/wiki/2026_in_spaceflight#Orbital_la...
Edit: mistyped 317 as 313
For civilian purposes this would be even more dystopian. Communication satellites and propaganda from space have always existed, but AI manufactured mass slop and propaganda from space really raises philosophical objections.
I still think it’s mostly a way to put pressure on politicians, « you either give us tax cut, fast tracked permits, and let us do what we want with the land or we go to space and you get no benefits »
Not sure what interest the government would have in stricter regulation of the rocket launching side of SpaceX. Environmental impact and impact on air traffic and boats is regulated. And SpaceX existing is strongly benefiting the US government. They are their biggest customer
If launch cost was truly $0 you could also do maintenance in space but I think it's more likely that you'd work to push up reliability instead. That's what SpaceX did with Starlink.