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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

#161

Post by davedx »

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…

I think the point is, yes, cooling is a significant engineering challenge in space; but having easy access to abundant energy (solar) and not needing to navigate difficult politically charged permitting processes makes it worthwhile. It's a big set of trade offs, and to only focus on "cooling being very hard in space" is kind of missing the point of why these companies want to do this.

Compute is severely power-constrained everywhere except China, and space based datacenters is a way to get around that.

Re: Economics of Orbital vs. Terrestrial Data Centers

#162

Post by davedx »

fanf2 wrote: post #105
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…

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

Yeah that's just flat out wrong then: you can't use the solar array as a radiator.

Re: Economics of Orbital vs. Terrestrial Data Centers

#164

Post by [deleted] »

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…

[deleted]

Re: Economics of Orbital vs. Terrestrial Data Centers

#165

Post by m_fayer »

SauntSolaire wrote: post #52
m_fayer wrote: post #30

Earlier quoted context omitted.

Your description of Elmo applies to several other billionaires who have somehow avoided quixotic hyper-destructive rampages through American politics. I’m all for wired funny, but not when it comes with this much carnage.

I'm not sure who the whole 'Elmo' thing is for -- more than anything I cringe at the person saying it, rather than thinking less of Elon or whatever the hope is. Like 'drumpf', or the whole small hands thing, it just comes across like a redditism that escaped confinement. Is the hope that Elon or fans of his read it and get offended? I doubt they care much, and I fail to see the point of it.

I use it to indicate my derision, and that I refuse to take this person seriously. That's the point. How the reader reacts is beside the point, to me.

Diminishing names used for delegitimization are not something reddit invented. Calling George W. Bush "dubya", Barack Obama "barry", or Richard Nixon "look it up" are all great examples of a time-honored tradition.

Hope I cleared that up for you.

Re: Economics of Orbital vs. Terrestrial Data Centers

#166

Post by jcattle »

mkesper wrote: post #157
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.

Please have a look at how real stations like ISS handle the problem and do not trust in should-work science fiction. It's hard. https://en.wikipedia.org/wiki/International_Space_Station#Po...

Taking a system which was conceptualized about a quarter of a century ago and serves much different needs than what a datacenter in space needs (e.g. very strict thermal band, compared to acceptable temperature range from 20 to 80 degrees) isn't ideal.

The physics is quite simple and you can definitely make it work out. The Stefan Boltzman law works in your favor the higher you can push your temperatures.

If anything a orbital datacenter could be a slightly easier case. Ideally it will be in an orbit which always sees the sun. Most other satellites need to be in the earth shadow from time to time making heaters as well radiators necessary.

Re: Economics of Orbital vs. Terrestrial Data Centers

#167

Post by ithkuil »

modeless wrote: post #114
terminalshort wrote: post #76

Earlier quoted context omitted.

But space isn't actually cold, or at least not space near Earth. It's about 10 C. And that's only about a 10 C less than room temperature, so a human habitable structure in near earth space won't radiate very much heat. But heat radiated is O(Tobject^4 - Tbackground^4), and a computer can operate up to around 90C (I think) so that is actually a very big difference here. Back of the envelope, a data center at 90C will…

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.

There is a large region of the upper atmosphere called the thermosphere where there is still a little bit of air. The pressure is extremely low but the few molecules that are there are bombarded by intense radiation and thus reach pretty high temperatures, even 2000 C!

But since there are so few such molecules in any cubic meter, there isn't much energy in them. So if you put an object in such a rarefied atmosphere. It wouldn't get heated up by it despite such a gas formally having such a temperature.

The gas would be cooled down upon contact with the body and the body would be heated up by a negligible amount

Re: Economics of Orbital vs. Terrestrial Data Centers

#168

Post by jcattle »

davedx wrote: post #162
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

Yeah that's just flat out wrong then: you can't use the solar array as a radiator.

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...

Re: Economics of Orbital vs. Terrestrial Data Centers

#169

Post by vessenes »

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…

Jusssst had this conversation two nights ago with a smart drunk friend. To his credit when I asked "what's heat?" and he said "molecules moving fast" and I said "how many molecules are there in space to bump against?" He immediately got it. I'm always curious what ideas someone that isn't familiar with a problem space comes up with for solutions, so I canvased him for thoughts -- nothing novel, unfortunately, but if we get another 100 million people thinking about it, who knows what we'll come up with?

Re: Economics of Orbital vs. Terrestrial Data Centers

#170

Post by uplifter »

jcattle wrote: post #166
mkesper wrote: post #157

Earlier quoted context omitted.

Please have a look at how real stations like ISS handle the problem and do not trust in should-work science fiction. It's hard. https://en.wikipedia.org/wiki/International_Space_Station#Po...

Taking a system which was conceptualized about a quarter of a century ago and serves much different needs than what a datacenter in space needs (e.g. very strict thermal band, compared to acceptable temperature range from 20 to 80 degrees) isn't ideal. The physics is quite simple and you can definitely make it work out. The Stefan Boltzman law works in your favor the higher you can push your temperatures. If anything…

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 higher temperature so as to radiate heat efficiently, but that would itself take power, the power required to concentrate heat which naturally/thermodynamically prefers to stay spread out. How much power does that take? I have no idea.

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