Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Economics of Orbital vs. Terrestrial Data Centers

andrewmccalip.com

Post reply on HN
Print view View original

221–230 of 282 posts

Re: Economics of Orbital vs. Terrestrial Data Centers

#221

Post by moralestapia »

jofer wrote: post #39

What really worries me is that I keep hearing "cooling is cheap and easy in space!" in a lot of these conversations, and it couldn't be farther from the truth. Cooling is _really_ hard and can't use efficient (i.e. advection-based air or water cooling) approaches and are limited to dramatically less efficient radiative cooling. It doesn't matter that space is cold because cooling is damned hard in a vacuum. The artic…

Maybe hang out with different people?

Everyone I talked to (and everyone on this forums) knows cooling is hard in space.

It is always the number one comment on every news piece that is featured here talking about "AI in space".

Re: Economics of Orbital vs. Terrestrial Data Centers

#222

Post by moralestapia »

cmgbhm wrote: post #59
wmf wrote: post #45

Earlier quoted context omitted.

None of it is easy but neither is cooling impossible as many people are saying.

Doing like an 8xh200 server ( https://docs.nvidia.com/dgx/dgxh100-user-guide/introduction-... ) is 10.2kW. Let’s say you need 50m^2 solar panels to run it, then just a ton of surface area to dissipate. I’d love to be proven wrong but space data centers just seem like large 2d impact targets.

>large 2d impact targets

I bet you a million dollars cash that you would not be able to reach them.

Re: Economics of Orbital vs. Terrestrial Data Centers

#223

Post by jofer »

wongarsu wrote: post #177
eldenring wrote: post #136

Earlier quoted context omitted.

You should read the linked article, they talk about it there. You radiate the heat into space which takes less surface area than the solar panels and you can just have them back to back. In general I don't understand this line of thinking. This would be such a basic problem to miss, so my first instinct would be to just look up what solution other people propose. It is very easy to find this online.

It's definitely a solvable problem. But it is a major cost factor that is commonly handwaved away. It also restricts the size of each individual satellite: moving electricity through wires is much easier than pumping cooling fluid to radiators, so radiators are harder to scale. Not a big deal at ISS scale, but some proposals had square kilometers of solar arrays per satellite

That exactly. It's not that it's impossible. It's that it's heavy to efficiently transport heat to the radiators or requires a lot of tiny sats, which have their with problems.

Re: Economics of Orbital vs. Terrestrial Data Centers

#224

Post by dsr_ »

notahacker wrote: post #175
jcattle wrote: post #168

Earlier quoted context omitted.

Of course you can. You can use everything as a radiator. Unless you have something which is literally 0 Kelvin everything radiates. See here for all the great ways of getting rid of thermal energy in space: https://www.nasa.gov/smallsat-institute/sst-soa/thermal-cont...

You can use everything as a radiator, but you can't use everything as a radiator sufficiently efficient to cool hot chips to safe operating temperature, particularly not if that thing is a thin panel intentionally oriented to capture the sun's rays to convert them to energy. Sure, you can absolutely build a radiator in the shade of the panels (it's the most logical place), but it's going to involve extra mass.

You also want to orient those radiators at 90 degrees to the power panels, so that they don't send 50% of their radiation right back to the power panels.

Re: Economics of Orbital vs. Terrestrial Data Centers

#225

Post by arijun »

mojosam wrote: post #211

> That "why" is almost missing from the public conversation. People jump straight to hardware and hand-wave the business case, as if the economics are self-evident. They aren't. But then he never answers that fundamental question, and jumps straight to the hardware and power and cost? What problems are orbital data centers trying to solve? What optimizations are they intended to deliver? Are these optimizations benef…

> But then he never answers that fundamental question

The fundamental question is “is it economically viable”, and the answer from his model is “not really”

> A constellation of 40,000 satellites with GPUs “infrastructure that makes it easier for humans to keep spreading out”?

I think he’s claiming industrializing larger and more economical power generation in space, as well as the means to put it up there, would make it easier to transition to a theoretical space economy

> But isn’t that precisely what everyone has been saying?

From the article, he claims that people handwave the economics, so at least the people he has interacted with haven’t been saying that.

Re: Economics of Orbital vs. Terrestrial Data Centers

#226

Post by torginus »

TheOtherHobbes wrote: post #194
uplifter wrote: post #170

Earlier quoted context omitted.

These data centers are solar powered, right? So if they are absorbing 100% of the energy on their sun side, by default they'll be able to heat up as much as an object left in the sun, which I assume isn't very hot compared to what they are taking in. How do they crank their temperature up so as to get the Stefan Boltzmann law working in their favor? I suppose one could get some sub part of the whole satellite to a hi…

σ is such a small number in Stefan-Boltzman that it makes no difference at all until your radiators get hot enough to start melting. You not only need absolute huge radiators for a space data centre, you need an active cooling/pumping system to make sure the heat is evenly distributed across them. I'm fairly sure no one has built a kilometer-sized fridge radiator before, especially not in space. You can't just stick…

Out of curiosity, I plugged in the numbers - I have solar at home, and a 2 m2 panel makes about 500w - i assume the one in orbit will be a bit more efficient without atmosphere and a bit more fancy, making it generate 750w.

If we run the radiators at 80C (a reasonable temp for silicon), that's about 350K, assuming the outside is 0K which makes the radiator be able to radiate away about 1500W, so roughly double.

Depending on what percentage of time we spend in sunlight (depends on orbit, but the number's between 50%-100%, with a 66% a good estimate for LEO), we can reduce the radiator surface area by that amount.

So a LEO satellite in a decaying orbit (designed to crash back onto the Earth after 3 years, or one GPU generation) could work technically with 33% of the solar panel area dedicated to cooling.

Realistically, I'd say solar panels are so cheap, that it'd make more sense to create a huge solar park in Africa and accept the much lower efficiency (33% of LEO assuming 8 hours of sunlight, with a 66% efficiency of LEO), as the rest of the infrastructure is insanely more trivial.

But it's fun to think about these things.

Re: Economics of Orbital vs. Terrestrial Data Centers

#227

Post by torginus »

Yizahi wrote: post #187
fanf2 wrote: post #105

Earlier quoted context omitted.

This article assumes that no extra mass is needed for cooling, i.e. that cooling is free. The list of model assumptions includes: • No additional mass for liquid cooling loop infrastructure; likely needed but not included • Thermal: only solar array area used as radiator; no dedicated radiator mass assumed

Author also forgot batteries for the solar shade transition period and then additional solar panels to charge these batteries during the solar "day" period. then insulation for batteries. Then power converters and pumps for radiators and additional radiators to cool the cooling infrastructure. Overall not a great model. But on the other hand, even an amateur can use this model and imagine that additional parts and co…

I'd say int makes much more sense to just shut off in the sunshade. The advantage of orbital solar, comes not so much from the lack of atmosphere, but the fact that depending on your orbit, you can be in sunlight for 60-100% of the time.

Re: Economics of Orbital vs. Terrestrial Data Centers

#228

Post by pfdietz »

PeterHolzwarth wrote: post #132
jofer wrote: post #39

What really worries me is that I keep hearing "cooling is cheap and easy in space!" in a lot of these conversations, and it couldn't be farther from the truth. Cooling is _really_ hard and can't use efficient (i.e. advection-based air or water cooling) approaches and are limited to dramatically less efficient radiative cooling. It doesn't matter that space is cold because cooling is damned hard in a vacuum. The artic…

"space is cold" I've always enjoyed thinking about this. Temperature is a characteristic of matter. There is vanishingly little matter in space. Due to that, one could perhaps say that space, in a way of looking at it, has no temperature. This helps give some insight into what you mention of the difficulties in dealing with heat in space - radiative cooling is all you get. I once read that, while the image we have in…

Temperature is a property of systems in thermal equilibrium. One such system is blackbody radiation, basically a gas of photons that is in thermal equilibrium.

The universe is filled with such a bath of radiation, so it makes sense to say the temperature of space is the temperature of this bath. Of course, in galaxies, or even more so near stars, there's additional radiation that is not in thermal equilibrium.

Re: Economics of Orbital vs. Terrestrial Data Centers

#229

Post by DoctorOetker »

anonymousiam wrote: post #126

This is an interesting analysis, and I like the sliders that let you instantly show the impacts of system trades. The one glaring hole that I see is the challenge of moving the data to/from the datacenter while it's on orbit. Bandwidth to/from space isn't free. FCC/ITU licenses are required, transmitters/receiviers/modems/DSP/antennas all add to SWAP (size, weight, and power). Ground-stations are needed to move the d…

The most chased workload will inevitably be cryptographic research, proofs of mathematical statements are hard to find the proof for, but tend to be short and easy to verify once a putative proof is presented. Just send the proofs back to earth.

Re: Economics of Orbital vs. Terrestrial Data Centers

#230

Post by pfdietz »

Nevermark wrote: post #131
pavon wrote: post #70

Earlier quoted context omitted.

Cooling isn't anymore difficult than power generation. For example, on the ISS solar panels generate up to 75 W/m², while the EATCS radiators can dissipate about 150 W/m². Solar panels have improved more than cooling technology since ISS was deployed, but the two are still on the same order of magnitude.

So just 13.3 million sq. meters of solar panels, and 6.67 million sq. meters of cooling panels for 1 GW. Or a 3.651 km squared and 2.581 km squared butterfly sattelite. I don't think your cooling area measures account for the complications introduced by scale. Heat dissipation isn't going to efficiently work its way across surfaces at that scale passively. Dissipation will scale very sub-linearly, so we need much mor…

Solar panels can in principle be made very thin, since there are semiconductors (like CdTe) where the absorption length of a photon is So maybe if we had such PV, we could make huge gossamer-thin arrays that don't have much mass, then use the power from these arrays to pump waste heat up to higher temperature so the radiators could be smaller.

The enabling technology here would be those very low mass PV arrays. These would also be very useful for solar-electric spacecraft, driving ion or plasma engines.

Post reply on HN