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Economics of Orbital vs. Terrestrial Data Centers

andrewmccalip.com

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Re: Economics of Orbital vs. Terrestrial Data Centers

#231

Post by IncreasePosts »

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…

Who says that?

Every conversation I've seen is despite how many serious organizations with talented people, the "uhhh how do you cool it?" Is brought up immediately

Re: Economics of Orbital vs. Terrestrial Data Centers

#232

Post by pfdietz »

krisoft wrote: post #202
Nevermark wrote: post #131

Earlier quoted context omitted.

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…

> active fluid exchangers operating at speed spanning kilometers of real estate, to get dissipation/area anywhere back near linear/area again Could the compute be distributed instead? Instead of gathering all the power into a central location to power the GPUs there, stick the GPUs on the back of the solar panels as modules? That way even if you need active fluid exchanger it doesn’t have to span kilometers just mete…

It's easier to shield the GPUs if they're all grouped up.

Re: Economics of Orbital vs. Terrestrial Data Centers

#233

Post by fulafel »

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…

Related: what color is space?

Re: Economics of Orbital vs. Terrestrial Data Centers

#234

Post by modeless »

terminalshort wrote: post #156
modeless wrote: post #114

Earlier quoted context omitted.

The temperature that you raise to the fourth power is not Celsius, it's Kelvin. Otherwise things at -200 C would radiate more heat than things at 100 C. Also the temperature of space is ~3 K (cosmic microwave background), not 10 C.

Yeah, if you forget about the giant fucking star nearby

The Sun is also not 10 C. Luckily you have solar arrays which shade your radiators from it, so you can ignore the direct light from it when calculating radiator efficiency. The actual concern in LEO is radiation from the Earth itself.

Re: Economics of Orbital vs. Terrestrial Data Centers

#235

Post by DoctorOetker »

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…

Assuming merely attitude control, sure only radiative cooling is available, but its very easy to design for arbitrary cooling rates assuming any given operating temperature:

Budget the solar panel area as a function of the maximum computational load.

The rest of the satellite must be within the shade of the solar panel, so it basically only sees cold space, so we need a convex body shape, to insure that every surface of the satellite (ignoring the solar panels) is radiatively cooling over its full hemisphere.

So pretend the sun is "below", the solar panels are facing down, then select an extra point above the solar panel base to form a pyramid. The area of the slanted top sides of the pyramid are the cooling surfaces, no matter how close or far above the solar panels we place this apex point, the sides will never see the sun because they are shielded by the solar panel base. Given a target operating temperature, each unit surface area (emissivity 1) will radiate at a specific rate, and we can choose the total cooling rate by making the pyramid arbitrarily long and sharp, thus increasing the cooling area. We can set the satellite temperature to be arbitrarily low.

Forget the armchair "autodidact" computer nerds for a minute

Re: Economics of Orbital vs. Terrestrial Data Centers

#236

Post by two_handfuls »

torginus wrote: post #226
TheOtherHobbes wrote: post #194

Earlier quoted context omitted.

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. Depen…

Yes it's fun. One small note, for the outside temp you can use 3K, the cosmic microwave background radiation temperature. Not that it would meaningfully change your conclusion.

Re: Economics of Orbital vs. Terrestrial Data Centers

#237

Post by kristianbrigman »

yabones wrote: post #51
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…

Yeah, I don't see a way to get around the fact that space is a fabulous insulator. That's precisely how expensive insulated drink containers work so well. If it was just about cooling and power availability, you'd think people would be running giant solar+compute barges in international waters, but nobody is doing that. Even the "seasteading" guys from last decade. These proposals, if serious, are just to avoid plann…

But heat = energy, right? So maybe we don’t really want to radiate it, but redirect it back into the system in a usable way and reduce how much we need to take in? (From the sun etc)

Re: Economics of Orbital vs. Terrestrial Data Centers

#238

Post by Glyptodon »

KineticLensman wrote: post #34
Glyptodon wrote: post #4

I guess I'd assume that the premise driving this would be that there will eventually be enough business in space that it's necessary for space-centric use, and that terrestrial use is just a fringe benefit or loss leader or something. But oddly this doesn't seem to be how the concept is typically framed. My second level curiosity is how much cheaper/competitive it'd be if we had space elevators.

space-elevators require various types of unobtanium and have their own logistics challenges not to mention failure modes that involve spattering fast moving debris round the entire equator

Obviously I don't expect one next Tuesday. I just think it'd be interesting to see how it alters the picture.

Re: Economics of Orbital vs. Terrestrial Data Centers

#240

Post by margalabargala »

zeofig wrote: post #139
PeterHolzwarth wrote: post #132

Earlier quoted context omitted.

"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…

A perfect vacuum might have no temperature, but space is not a perfect vacuum, and has a well-defined temperature. More insight would be found in thinking about what temperature precisely means, and the difference between it and heat capacity.

I think the better argument to be made here is "space has a temperature, and in the thermosphere the temperature can get up to thousands of degrees. Space near Earth is not cold."
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