That should be better than a sphere. Though I imagine there could be some fancier 3D geometry designs.
Even for a simple sphere, if we give it different surface roughnesses on the sun-facing side and the "night" side, it can have dramatically different emissivity.
This is a common way of thinking. In practice this type of thing is more like optimizing flop allocation. Surely with an infinite compute and parameter budget you could have a better model with more intensive operations.
Another thing to consider is that transformers are very general computers. You can encode many many more complex architectures in simpler, multi layer transformers.
What you're describing is one of two mechanisms of shedding heat which is convection, heating up the environment. What the long comment above is describing is a _completely_ different mechanism, radiation, which is __more__ efficient in a vacuum. They are different things that you are mixing up.
Solar in space is a very different energy source in terms of required infrastructure. You don't need batteries, the efficiency is much higher, cooling scales with surface area (radiative cooling doesn't work as well through an atmosphere vs. vacuum), no weather/day cycles. Its a very elegant idea if someone can get it working.
The panels suffer radiation damage they don't suffer on Earth. If this is e.g. the same altitude orbits as Starlink, then the satellites they're attached to burn up after around tenth of their ground-rated lifetimes. If they're a little higher, then they're in the Van Allen belts and have a much higher radiation dose. If they're a lot higher, the energy cost to launch is way more.
If you could build any of this on the moon, that would be great; right now, I've heard of no detailed plans to do more with moon rock than use it as aggregate for something else, which means everyone is about as far from making either a PV or compute factory out of moon rock as the residents of North Sentinel Island are.
OK, perhaps that's a little unfair, we do actually know what the moon is made of and they don't, but it's a really big research project just to figure out how to make anything there right now, let alone making a factory that could make them cost-competitive with launching from Earth despite the huge cost of launching from Earth.
> The panels suffer radiation damage they don't suffer on Earth.
I don't think this is true, Starlink satellites have an orbital lifetime of 5-7 years, and GPUs themselves are much more sensitive than solar panels for rad damage. I'd guess the limiting factor is GPU lifetime, so as long as your energy savings outpace the slightly faster gpu depreciation (maybe from 5 -> 3 years) plus cost of launch, it would be economical.
I've said this elsewhere, but based on my envelope math, the cost of launch is the main bottleneck and I think considerably more difficult to solve than any of the other negatives. Even shielding from radiation is a weight issue. Unfortunately all the comments here on HN are focused on the wrong, irrelevant issues like talking about convection in space.
> I don't think this is true, Starlink satellites have an orbital lifetime of 5-7 years,
That's better than I thought, but still means their PV is only lasting order-of 20% of their ground lifespans, so the integrated lifetime energy output per unit mass of PV isn't meaningfully improved by locating them in space, even if they were launched by an efficient electromagnetic system rather than by a rocket.
1. solar is very efficient at generating energy, no moving parts, simple physics etc.
2. in space you don't deal with weather or daylight cycle, you can just point your panels at the sun and generate very stable energy, no batteries required
3. environmental factors are simpler, no earthquakes, security, weather. Main problem here is radiation
In theory its a very elegant way to convert energy to compute.
2 is wrong. At a Lagrange point you can do this. Not in low earth orbit - in LEO sunset is every 60 minutes or so, and you spend the next 60 minutes in darkness.
Satellites are heavily reliant on either batteries or being robust to reboots, because they actually do not get stable power - it's much more dynamic (just more predictable too since no weather).
You can line the solar panels and radiators facing away from each other, and the radiators would take up less surface area. I think maybe the tricky part would be the weight of water + pipes to move heat from the compute to the radiators.
That is not a realistic test, as any space engineer could’ve told them. First of all that’s on the very low end for a cosmic ray, an order of magnitude below the average energy. But the average energy doesn’t matter because there is a very wide distribution and the much more intensive cosmic rays do far more damage. It was also not a fully integrated test with a spacecraft, which matters because a high energy cosmic ray, striking other parts of the spacecraft, generates a shower of secondary particles that do most of the damage of a cosmic ray strike.
If someone has a design out there where this works and you can launch it economically on a rocket today, I wanna see that. And then I wanna compare it to the cost of setting up some data centers on earth (which BTW, you can service in real time, it sounds like these will be one-and-done launches).
these same comments pop up every time someone brings up satellite data-centers where people just assume the only way of dissipating heat is through convection with the environment.
No, we just "assume" (i.e. know) that radiation in a vacuum is a really bad way of dissipating heat, to the point that we use vacuum as a very effective insulator on earth.
Yes, you can overcome this with enough radiator area. Which costs money, and adds weight and space, which costs more money.
Nobody is saying the idea of data centers in space is impossible. It's obviously very possible. But it doesn't make even the slightest bit of economic sense. Everything gets way, way harder and there's no upside.
> No, we just "assume" (i.e. know) that radiation in a vacuum is a really bad way of dissipating heat, to the point that we use vacuum as a very effective insulator on earth.
In space or vacuum radiation is the best way to dissipate heat, since it's the only way.
I believe the reason the common person assumes thermal radiation is a very poor way of shedding heat is because of 2 factoids commonly known:
1. People think they know how a vacuum flask / dewar works.
2. People understand that in earthly conditions (inside a building, or under our atmosphere) thermal radiation is insignificant compared to conduction and convection.
But they don't take into account that:
1) Vacuum flasks / dewars use a vacuum for thermal insulation. Yes and they mirror the glass (emissivity nearer to ~0) precisely because thermal radiation would occur otherwise. They try their best to eliminate thermal radiation, a system optimized to eliminate thermal radiation is not a great example of how to effectively use thermal radiation to conduct heat. The thermal radiation panels would be optimized for emissivity 1, the opposite of whats inside the vacuum flask.
2) In a building or under an atmosphere a room temperature object is in fact shedding heat very quickly by thermal radiation, but so are the walls and other room temperature objects around you, they are reheating you with their thermal radiation. The net effect is small, in these earthly conditions, but in a satellite the temperature of the environment faced by the radiating surfaces is 4K, not a temperature similar to the object you are trying to keep cool.
People take the small net effect of thermal radiation in rooms etc, and the slow heat conduction through a vacuum flasks walls as representative for thermal radiation panels facing cold empty space, which is the mistake.
Well no, it’s because conduction/convection into a fluid is so much more effective.
Just look at a car. Maybe half a square meter of “radiator” is enough to dissipate hundreds of kW of heat, because it can dump it into a convenient mass of fluid. That’s way more heat than the ISS’s radiators handle, and three orders of magnitude less area.
Or do a simple experiment at home. Light a match. Hold your finger near it. Then put your finger in the flame. How much faster did the heat transfer when you made contact? Enough to go from feeling mildly warm to causing injury.
but thats what you don't get: conduction / convection on the ground is ultimately still radiation to space: you heat up our rivers, soils, atmosphere and the heat is eventually shed... by thermal radiation.
its not exactly good advertisement for conductive or convective heat transfer if its really employing thermal radiation under the hood!
but do you want big tech to shit where you eat? or do you want them to go to the bathroom upstairs?
At some point I'm thinking the large resistance to the idea I am seeing in a forum populated with programmers is the salivation-inducing idea that all that datacenter hardware will eventually get sold for less and less, but if we launch them to space there won't be any cheap devalued datacenter hardware to put in their man-caves.
I just get tripped up when I see people disbelieve physics, especially laws that have been known for about 150 years!
The economics and energy balance is where I too am very skeptical, at least near term.
Quick back of envelope calculations gave me a payback time of about 10 years, so which is only a single order of magnitude off which can easily accumulate by lack of access to detailed plans.
I can not exclude they see something (or can charge themselves lower launch costs, etc.) that makes it entirely feasible, but also can't confirm its infeasible economically. For example I have no insight of what fraction of terrestrial datacenter establishment cost goes into various "frictions" like paying goverments and lawyers to gloss over all the details, paying permission taxes etc. I can see how space can become attractive in other ways.
Then again if you look at the energetic cost to do a training run, it seems MW facilities would suffice. So why do we read all the noise about restarting nuclear power plants or trying to secure new power plants strictly for AI? It certainly could make sense if governments are willing to throw top dollar at searching algorithmic / mathematical breakthroughs in cryptography. Even if the compute is overpriced, you could have a lot of LLM's reasoning in space to find the breakthroughs before strategic competitors do. Its a math and logic race unfolding before our eyes, and its getting next to no coverage.
What false dichotomy? At no point did I even suggest that cooling by convection/conduction on the ground or cooling by radiation in space are the only two possibilities. I am not, despite what one might think, a complete moron. I know that there are more things. You could cool by radiation on the ground. You could cool in space by launching blocks of ice into orbit. You could put your computers on a balloon floating in Neptune and use its atmosphere for cooling.
The reason I'm talking about computers on the ground using the atmosphere for cooling is because that's how things are done right now and that's the obvious alternative to space-based computing.
Why does it matter what I prefer? I'd love to see all industry in space and Earth turned into a garden. I'm not talking about what I want. I'm talking about the economics. I'm asking why so many people are talking about putting data centers in space when doing so would be so much more difficult than putting data centers on Earth. If your argument is that it's more difficult but it's worth the extra effort so we don't "shit where we eat," great, but that's the first time I've ever seen that argument put forth. None of the actual players are making that case.
Additional radiator area means bigger spacecraft, implies more challenge with attitude control. Lower down you get more drag so you use propellant to keep yourself up, higher up you have more debris and the large area means you need to frequently manoeuvre to avoid collisions. Making things bigger in space is not trivial! You can't just deploy arbitrarily large panels and expect everything to be fine.
heavier boats are also slower to accelerate or decelerate compared to smaller boats, does this mean we should ban container ships? having special orbits for megastructure lanes would seem a reasonable approach.
The radiators would be lighter compared to the solar panels, and slightly smaller surface area so you can line them back to back
I don't think dissipating heat would be an issue at all. The cost of launch I think is the main bottleneck, but cooling would just be a small overhead on the cost of energy. Not a fundamental problem.
If you solved this problem apply at nasa because they still haven't figured it out.
Either that or your talking out of your ass.
FYI a single modern rack consumes twice the energy of the entire ISS, in a much much much much smaller package and you'll need thousands of them. You'd need 500-1000 sqm of radiator per rack and that alone would weight several tonnes...
You'll also have to actively cool down your gigantic solar panel array
eldenring is slightly wrong: for reasonable temperatures the area of the radiating panels would have to be a bit more than 3 times the area of the solar panel, otherwise theres nothing wrong.
No need to apply at NASA, to the contrary, if you don't believe in Stefan Boltzmann law, feel free to apply for a Nobel prize with your favorite crank theory in physics.
Whats your definition for reasonable temp? my envelope math tells me at 82 celsius (right before h100s start to throttle) you'd need about 1.5x the surface area for radiators. Not exactly back to back, but even 3x surface area is reasonable.
Also this assumes a flat surface on both sides. Another commenter in this thread brought up a pyramid shape which could work.
Finally, these gpus are design for earth data centers where power is limited and heat sinks are abundant. In the case of space data centers you can imagine we get better radiators or silicon that runs hotter. Crypto miners often run asics very hot.
I just don't understand why every time this topic is brought up, everyone on HN wants to die on the hill that cooling is not possible. It is?? the primary issue if you do the math is clearly the cost of launch.
I am the person who gave the pyramid shape as a didactic example (convexity means we can ignore self obscuration, and giving up 2 of the 4 triangular side surfaces of the pyramid allows me to ignore the presence of lukewarm earth).
My example is optimized not for minimal radiator surface area, but for minimal mathematical and physical knowledge required to understand feasibility.
Your numbers are different because you chose 82 C (355 K) instead of my 26 C (300 K).
Near normal operating temperatures hardware lifetime roughly doubles for every 10 deg C/K decrease in temperature (this does not hold indefinitely of course).
You still need to move the heat from the GPU to the radiator so my example of 26 deg C at the radiator just leaves a lot of room against criticism ;)
Who’s saying cooling is not possible? Cooling gets brought up because it’s presented as an advantage of putting stuff in space. But it’s not an advantage, cooling is harder in space than on the ground.
Search "data centers in space" and it gets mentioned constantly. Cooling is even mentioned in this announcement. It's not explicitly described as an advantage for putting things in space, but it states that terrestrial data centers "require immense amounts of power and cooling," and that heavily implies that cooling is less of a problem in space.
The distinction is that you don't need to compete for land area, that you don't cause local environmental damage by heating say a river or a lake, that you don't compete with meatbags for energy and heat dissipation rights.
Without eventually moving compute to space we are going to have compute infringe on the space, energy, heat dissipation rights of meatbags. Why welcome that?!?
> How efficient is thermal radiation through a vacuum again?
I provided the calculation for the pyramidal shape: if the base of a pyramid were a square solar panel with side length L, then for a target temperature of 300K (a typical back of envelope substitute for "room temperature") the height of the pyramid would have to be about 3 times the side length of the square base. Quite reasonable.
> Sure, it occurs, but what does the Stefan–Boltzmann law tell us about GPU clusters in space?
The Stefan-Boltzmann law tells us that whatever prevents us from putting GPU clusters in space, it's not the difficulty in shedding heat by thermal radiation that is supposedly stopping us.
Just picture a square based pyramid, like a pyramid from egypt, thats the rough shape. Lets pretend the bottom is square. For thermodynamic analysis, we can just pretend the scale is irrelevant, it could be 4 cm x 4 cm base or 4 km x 4 km base. Now stretch the pyramid so the height of the tip is 3 times the length of the sides of the square base, so 12 cm or 12 km in the random examples above.
If the base were a solar panel aimed perpendicular to sun, then the tip is facing away and all side triangles faces of the pyramid are in the shade.
I voluntarily give up heat dissipation area on 2 of the 4 triangular sides (just to make calculations easier, if we make them thermally reflective -emissivity 0-, we can't shed heat, but also don't absorb heat coming from lukewarm Earth).
The remaining 2 triangular sides will be large enough that the temperature of the triangular panels is kept below 300 K.
The panels also serve as the cold heat baths, i.e. the thermal sinks for the compute on board.
Not sure what you mean with wings, I intentionally chose a convex shape like a pyramid so that no part of the surface of the pyramid can see another part of the surface, so no self-obstruction for shedding heat etc...
If this doesn't answer your question, feel free to ask a new question so I understand what your actual question is.
The electrical power available for compute will be approximately 20% (efficiency of solar panels) times the area of the square base L ^ 2 times 1360 W / m ^ 2 .
The electrical power thus scales quadratically with the chosen side length, and thus linearly with the area of the square base.
Some people on here are such NPCs, you can give them all calculations, numbers and diagrams as to how this is not an impossible concept, and all they will say is "Thermal radiation is not efficient".
You can prove that the lower efficiency can be managed, and they will still say the only thing they know: "Thermal radiation is not efficient".
as an example my points almost instantly fell down 15 points, but over the last 11 hours it has recuperated back to just a 1 point drop.
it's not because they don't like to write an apology (which I don't ask for) that they aren't secretly happy they learnt something new in physics, and in the end thats what matters to me :)
Cooling is being presented as an advantage of putting these things in space. Of course the lower efficiency can be managed. But it’s not an advantage. If cooling is harder (which it is) the what’s the point of this whole thing?
So how big are you proposing the solar panel be to be able to provide 1GW to the GPUs? Nearly a square kilometer? With an additional 3 square kilometers of radiators?
Yeah doesn't sound particularly feasible, sorry. Glad you know all the math though!
For a 230 kW cluster: 16 x DGX (8x)B200; we arrived at a 30m x 30m solar PV area, and a 90 meter distance from the center of the solar array to the tip of the pyramid.
1 GW = 4348 x 230 kW
sqrt(4348)= ~66
so launch 4348 of the systems described in the calculation I linked, or if you insist on housing them next to each other:
the base length becomes 30 m x 66 = 1980 m = ~ 2 km. the distance from center of square solar array to the tip of the pyramid became 6 km...
any of these systems would need to be shipped and collected in orbit and then assembled together.
Musk wants to put up 500-1000 TW per year. Even 1 TW would be 4.348 million of your systems. Even one of your clusters is at the edge of what we've built, and you talk about snapping 4000 of them together as if they were legos.
To run just one cluster (which would be generally a useless endeavor given it is just a few dozen GPUs) would be equivalent to the best we've ever done, and you wonder why you're being downvoted? Your calculations, which are correct from a scientific (but not engineering) standpoint, don't support the argument that it is possible, but rather show how hard it is. I can put the same cluster in my living room and dissipate the heat just fine, but you require a billion dollar system to do it in space.
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