[svantana]

I dunno if it's that clear cut. In space with a shadowless orbit you get 5x more solar energy per day than the sunniest place on earth. And it's always on, so you don't need batteries. Also, the lack of gravity and weather means that the structures can be a lot more brittle - I imagine something like a gpu on the back of a large thin film solar panel, where the panel also acts as heatsink. Could be pretty cheap!

[panick21_]

So you are comparing putting up slightly more solar panels and some batteries, both things that are mass produced commodity with re-engineering the whole computing ecosystem and how data-centers have been done for decades, transporting them on the most expensive known transportation system and then operating it in a way where you need specially educated experts.

So my bet would be that just ordering a bunch of sodium batteries and a bunch of solar panels (or you know using a source of energy that is constant) is cheaper then going threw all the effort of putting things into space.

I have been following everything space for decades, and not once have I thought, wow putting super complex engineering things into space so easy and you should do it for things that have an easy alternative on earth.

[sidewndr46]

while there may not be atmospheric weather, low earth orbit has its own "weather". Before you even reach LEO you start getting bombarded by all forms of energetic particles. None of these are things you want your computers saturated with

[sschueller]

You can only cool by radiation in space. You may get more energy from the sun but how are you going to get rid of all the heat fast enough?

[svantana]

How hot do you think black objects in space get? Something like 10°C. Look up thermal equilibrium of an ideal black body.

[adastra22]

In the vicinity of the Earth, they get to about the temperature of the Earth. That’s not a coincidence. Hotter if they are actively generating heat.

[Symmetry]

Nobody (sane) is talking about putting nuclear reactors on Satellites in close Earth orbit so we don't have to worry about them generating heat. They've got solar panels that move some of the solar energy they absorb to a central location which presents problems in moving the waste heat back out so that spot doesn't get too hot. But that doesn't change the overall equilibrium temperature.

[adastra22]

Running a data center generates heat.

[Symmetry]

Not if you first absorb heat with your solar panels. Conservation of energy and all that.

[Geof25]

So you can have datacenters in space, you are just not allowed to use them

[jeltz]

Not using them would also solve all issues with cosmic radiation.

[philipallstar]

But are they doing work internally that generates heat? Genuine question.

[Schiendelman]

They are. But only as much heat as they get from the solar radiation that's hitting them anyway. Exactly that amount.

[philipallstar]

I didn't think of it like that. Does that mean all solar radiation is heat from when it hits a solar panel? I thought it would be something like solar -> chemical -> electrical -> heat.

[saalweachter]

Except you aren't leaving that heat in place.

You're concentrating it into a very small area of compute.

If you don't spread that heat back out, it's going to find a much higher thermal equilibrium than the solar panels themselves would find just absorbing the sunlight and radiating the energy back into space.

It's like you've pointed a magnifying glass at your compute, except with electricity, which means you can reach temperatures higher than you can with a magnifying glass.

[Schiendelman]

I guess I'm curious: all the comments I see about this act as if the people proposing putting data centers in space are complete idiots. Do you believe they are complete idiots?

[db48x]

If you gather 1kW of power from the sun then you have to reject 1kW of heat once you are done with whatever computation you are doing. There’s a bit more heat absorbed from the environment since some sunlight strikes parts of your satellite that are not solar panels, but it’s not too bad. Starlink satellites, just to pick a relevant example, do not need a radiator at all because they stay mostly edge–on to the sun and they can radiate all the heat through their own surface area. The ISS needs big radiators because they want it to be comfortable for humans, but electronics can run significantly hotter than that.

[lukan]

Yes, you get much more radiation from the sun and other sources. How do you do cooling? Radiators the size of small moons?

Also hard radiation is not something transistors like.

[svantana]

The joint solar panel + computer system will be pretty close to an ideal black body, which near earth will have an average temperature of about 10°C. And radiation is an issue, but starlink seems to work so I don't see why this wouldn't.

[AntiUSAbah]

Of course it works, the question is how this would look like and if its financial feasable.

You make a H100, ship it to a space dock, load it onto a rocket (rocket requires fuuel, the rocket, etc.) send it up, deploy it, monitor it live 24/7, have means of adjusting its orbit, if it breaks, its immediade full loss, otherwise it will degenerate faster in space than on earth, now it needs a high speed up/downlink to do anything reasonable which also requires a base station. The base station has to track this satelite.

One H100 costs 40k, consumes 700 Watt peak and need probably at a minimum 5 square meter of area for cooling and solar.

The colossus datacenter from musk has 250.000 of these.

Now you have to track 250.000 single satelites, you have to coordinate the communication between the, up and downlink to earth.

250.000 * 5 square meter of area.

This alone increases the potential debris in space.

And this is ONE 300 MW Datacenter replacement. ONE.

[db48x]

It’s very easy to overestimate the difficulty of cooling things in space, unless you actually run the numbers. So please follow along as Scott Manley runs the numbers: <https://www.youtube.com/watch?v=FlQYU3m1e80>.

Basically a Starlink v3 satellite has an estimated power budget of 20kW. Add in the heat absorbed from the environment (both directly from sunlight and reflected off of the Earth) and you’ll find that it must reject about 22kW of heat. That’s a fair amount, but at 65°C it can radiate it all away just using it’s own surface area! No radiator required at all!

Of course the power density of computer racks has been going up over the years. If you want to reach 100kW per satellite then they will need a modest radiator, but nothing extravagant. It would still be smaller than the solar panels, and far smaller than the ones on the ISS. And don’t forget that because radiated heat goes up as the fourth power of temperature, raising the temperature of the system by even a small amount raises the radiation emitted by a lot. If you design the system to run hotter you can minimize the size of the radiator. Most chips these days are designed to max out at 100°C to 110°C without lasting damage, although running them at that temperature 24/7 may reduce their lifespan. There will be some sweet spot in the middle.

And it turns out that a Starlink v3 already has a volume somewhat larger than a 48U rack. You talk about launching 250k satellites in order to have 250k GPUs in orbit, but that’s ridiculous. A real compute swarm will be hundreds or thousands of satellites each equivalent to a whole rack of GPUs.

But you’re not wrong to be skeptical. The economics might not work out even if the cooling is easy enough. It’s just that rejecting the idea takes a lot more than back–of–the–envelope calculations.

[causal]

What doesn't make sense to me here is that even on Earth, where we have an atmosphere to disperse heat into, we find that closed-loop cooling is too expensive and so use evaporative cooling.

If the economics make it too expensive not to use freshwater on Earth, I don't see how closed-loop cooling suddenly becomes affordable in space where dispersing heat is already more difficult.

[db48x]

Here in datacenters we use cooling systems to move heat away from the computers and out of the building. If each rack in the data center were outdoors and 100 yards away from every other then almost no cooling would be required. Just some fans to suck in air at the bottom and eject it out the top. Even less would be required if the individual GPUs were somehow separated from each other. Then we would truly be dispersing heat into the atmosphere with no cooling system at all.

Similarly, a satellite only needs a cooling system so that it can move the heat from the internal components outward towards the hull. A satellite containing a rack’s worth of GPUs might literally have heat spreaders that touch the chips on one side and the outer hull of the satellite on the other. Combine that with some heat pipes or something to spread the heat out efficiently and you hardly need anything else. A satellite the size and shape of a Starlink v3 already has enough surface area to dissipate something like 28kW at 80°C, and more if you run it hotter. If you want more than ~30–40 GPUs per satellite then you might need a small radiator to increase the surface area, or you might just make the thing thinner and wider instead. You’ll need more solar panel area anyway, so making the bus wider to match the wider solar panels is fine. The “closed–loop cooling system” you say is so unaffordable might be no more than a bunch of heat pipes. Or it might be an aquarium motor that pumps a few kilos of ammonia through some pipes or channels in the hull of the satellite.

[NetMageSCW]

Those economics only apply when there is a cheaper alternative available. Closed loop becomes economic when alternatives aren’t available.

[AntiUSAbah]

I'm not rejecting the basic idea in itself. There is nothing in this idea which we as humans can't do today. No issues here. Its just so much more expensive than just doing it in a dessert and putting fibre and solar panels and batteries there.

The Starlink v3 doesn't exist yet in space, it also needs Starship apparently and Musk said it will have the size of a Boeing 737 fully deployed. So it will not be small and its not proofen yet.

A rack with 48u will either have 12 or 24 GPUs which equals to 9kW or 17kW. Than its not 250k satellites for a 'small' 300MW DC but only 25k. Still a very crazy number.

I would love to see all of this scifi stuff happening. Spaceship in space, travel gates, dyson sphere but there is just no current breakthrough in our society which would indicate that this makes sense.

In my opinion, we as a society will have to get rid of capitalism first before we will do the next step and just because Musk needs a story to sell to keep his construct alive, doesn't mean its the right time.

[db48x]

> The Starlink v3 doesn't exist yet in space, it also needs Starship apparently

True but not really relevant. All prior versions of Starlink worked well enough, so there’s no reason to suspect that v3 won’t.

> … it will have the size of a Boeing 737 fully deployed. So it will not be small…

Irrelevant. Size is a weird measure here. You should ignore it because it is a marketing thing. All that is meant by it is that once the solar panels are extended they span a distance larger than the wingspan of a 737, nothing more. A Starlink v3 satellite has far less mass, interior volume, or complexity than a 737. I could get a long 30m rope and tell you that it was “larger than a 737”, but you wouldn’t be very impressed.

> A rack with 48u will either have 12 or 24 GPUs which equals to 9kW or 17kW. Than its not 250k satellites for a 'small' 300MW DC but only 25k. Still a very crazy number.

Are you sure? That fits within the estimated power budget of a Starlink v3, but I was assuming that GPUs were denser than that these days. I’m not an expert though. I figured a rack would hold somewhere between 96 and 128 GPUs depending on whether they had to be in 3u or 4u servers. They would need between 60kw and 90kW of power, and would need a modest radiator. The solar panels would be far larger than the radiator.

> I would love to see all of this scifi stuff happening. Spaceship in space, travel gates, dyson sphere but there is just no current breakthrough in our society which would indicate that this makes sense.

Ok, see, your problem is that you haven’t properly distinguished between different types of fiction. You put those three things in one category as if they were all equally fictional, but that cannot be true.

The first one is ambiguous, since the Space Shuttle was definitely a “spaceship in space”, so perhaps you just mean FTL travel like in Star Trek or Star Wars. By “travel gates” I assume you mean something like the eponymous gates from Stargate SG–1. Those are both ruled out by the laws of physics, and we can only tell stories about them because people willingly suspend their disbelief. Campbell said that a true science fiction story can only include one thing that requires the reader to suspend their disbelief. If it includes more than that then it is a fantasy instead.

But a Dyson sphere, or more accurately a Dyson swarm, is not an impossibility at all. If I can put one solar–powered satellite in orbit around the sun then if I am really industrious I could put ten, or a hundred, or a trillion. As many as I wanted and could afford, right? The laws of physics don’t say that a sun can only have 8 satellites around it, or any other number. Dyson knew that enough such satellites would eventually blot out the sun. They would absorb all the sunlight it could emit, and then the satellites would all emit infrared waste heat. If all of those satellites were doing something useful then whoever put them there would have a lot of useful work being done at their command. Even if it’s just trillions of GPUs making AI–powered cat memes, or simulating the minds of a bunch of human uploads, or even if they’re all just mirrors to redirect that light somewhere else, that’s a lot of power at our command. It is fictional only because it is an idea that nobody has actually gotten around to implementing yet. Once we’ve done it then it won't be fictional anymore.

> Its just so much more expensive than just doing it in a dessert and putting fibre and solar panels and batteries there.

No one here is arguing that it isn’t. It might still be cheaper to build datacenters on Earth. But most of the people who say that it’s _definitely_ still cheaper to build them on Earth are overestimating the difficulties, and therefore the costs, of doing it in orbit instead. We’re getting to the point where launch costs are low enough that it is no longer a given that it is cheaper.

For one thing, actually building things in the desert is expensive. You have to build all the necessary infrastructure yourself. Roads, power, water, fuel, etc, etc. You might as well be launching everything into space! No, if you want it to be cheaper you need to build somewhere closer to home, like Ohio.

[kamaal]

Everything you wrote is some definition of hard, but all doable. None of this is purely in the territory of 'known' impossible(like FTL travel).

Now different people have different points where they quit when things get hard.

This is true for even everyday things in life. Quitting triggers exist for people at various points in the ladder. The end of ladder and path both exist, its upto you to decide if you wish to continue climbing, or give up and quit.

Your mileage may vary.

[AntiUSAbah]

My problem is not the doing thing but the economy of it.

We are nowere near any resource limitation on planet earth for AI Datacenters.

Musk sells this story because he has Starship which needs payload to make financial sense. The payload doesn't exist so he inventes DC in Space.

Its the same thing as SpaceX buying Tesla Cybertrucks.

His old colossus datacenter is a 300MW Datacenter he now rents out to Anthropic because he doesn't even need his own compute. Colossus DC is probably 10x cheaper than his whole Space AI DC Story and will be for a long time.

[SideburnsOfDoom]

> Everything you wrote is some definition of hard, but all doable

The first line of the post that you are supposedly replying to is:

> Of course it works, the question is how this would look like and if its financial feasable.

Unless is cost-comparable to a data centre on Earth, and I am told that it very much is not, then there is no financial feasibility for space datacentres.

[orbisvicis]

More energy will be required than radiation absorbed by a spherical (ish) data center. You'll have massive solar panels piping energy in, and so the temperature would by higher than thermal equilibrium at that distance.

[lukan]

Starlink does not need so much energy as a datacenter.

[svantana]

I don't follow your logic. I mentioned starlink as an example of transistors (and solar panels) in space dealing with radiation.

[lukan]

Well I was talking about heat. But regarding radiation, there is a long history of transistors in space dealing with radiation. But ... there is also a whole science how to deal with making it reliable: answer, expensive redundancy.

And about starlink .. as far as I know the fail quite often but work, because of redundancy. So they get replaced.

If you want to ship GPU's to the orbit, then this surely works somehow, if you are willing to replace them often, which is expensive. Or you shield them, but then you will need to get up heavy shields. In general, of course computers work in space, but it is not cheap.

[AntiUSAbah]

Its not always on. Its only 'always' on if you would orbit the sun which starlink can't do, it has to orbit the earth. This only works in a certain constelation which would create a halo around our planet, without clear understanding what even would do.

The more power you consume, the more power you need to dissipate. These constelations wouldn't be small at all. It would also take a interesting solution to be able to move this heat from very small very intense areas to very big cooling areas. How?

And space is not easy. Space is very very cold which puts a lot of stress on materials. It has radiation. And it has A LOT of microasteroids. Stuff in Space breaks down due to this. You would need to replace all of this stuff regularly with resources from the planet earth.

You would basically just spend a lot of resources throwing a lot of resources out into space. You can't even recycle all of this.

Its still lunatic at our current state of our current system. There is so so much space on our planet. Its ridicoulous

The only reason Musk is saying stuff like this is because he knows there is no market and he needs to keep his system alive

[geertj]

The always on orbit exists and is called a dawn-dusk Sun synchronous orbit. It is an orbit that is always above the terminator (line between night and day) where it can face the Sun 100% of the time.

This orbit has to rotate about a degree every day to follow the terminator as the earth orbits the Sun. It uses the equatorial bulge of the earth to achieve that rotation without have to spend rocket fuel. It is really quite interesting.

[adrian_b]

But the slots on such Sun-synchronous orbits are limited and many applications want them.

A few datacenters could occupy some slots, but it would be difficult to accept a large number of datacenters obstructing such orbits.

[saalweachter]

Aren't dusk-dawn orbits already the most crowded orbital space with the most orbital debris?

[geertj]

Yes they are crowded. There are engineering solutions to that, including formation flying based on absolute positioning and space tethers. It is a great time to be an engineer.

[svantana]

A polar low earth orbit can be always-on (no earth shadow). Each satellite will be in thermal equilibrium, around 10°C. Catastrophic destruction from micrometeoroids is rare. I'm not saying it's a good idea, but I don't see any dealbreakers in the math/science.

[mapt]

Kessler Syndrome is the biggest dealbreaker. We're already fairly far advanced in that scenario from Starlink, and competitors/scaleouts to Starlink promise to be worse.

If you plug eleventy trillion dollars of hope that the aristos can finally replace the working class into the issue, Earth loses access to low orbit from orbital debris almost immediately.

Their entire mindset cannot deal with this. Low orbit is a physically-enforced type of commons, inextricably tied to tragedy if overpopulated. You cannot privatize it and scale indefinitely. There is no defense, and any pissed off individual actor who gets malicious can burn it to the ground.

[m4rtink]

Starlinks are in low enough orbit to passively decay in less than 5 years, that really can't meaningfully contribute to a Kessler syndrome.

Chinese mega constellations on higher orbits & their spent stages left in space are a bigger issues.

Still in case it got going & made higher orbits unusable, starlink would likely still work just fine on the lower self-cleaning orbits, not to mention using a partial (and hopefully soon full) RLV for replenishment.

[mapt]

A recent paper came out calculating that it would take two days of lights out at SpaceX headquarters for the whole constellation to shred itself, it was already so reliant on avoidance maneuvers.

SpaceX immediately responded by lowering its target orbits by 70km, the maximum it could legally do without renegotiating formally.

When a high orbit develops Kessler Syndrome, the billions of pieces of debris rain down on lower orbits and cause cascading collisions there, and they keep doing it for centuries.

Not understanding how any of this works, the scientists not being capable of convincing the politicos, or the leaders not being able to escape their local maxima of public stances to recognize a real threat, is a massive, civilizational level hubris. This is pass/fail - the math does not care about our level of understanding or maturity.

[NetMageSCW]

Incorrect. It was two days for one collision to occur. Most of the debris would then decay in a few weeks.

Stop trying to make Kessler Syndrome a thing. It was never a thing, it won’t be a thing, it will never be a thing.

[AntiUSAbah]

5 years is still 5 years and Musk needs A LOT of payload for SpaceX to justify 1 Trillion dollars.

This 1 Trillion Dollar has to be translated to either sending up A LOT of foreign payload OR his payload; All of this payload = new Satelites. Its not like we are sending earth resource up in space to build a dyson sphere.