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Data centers in space makes no sense

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Re: Data centers in space makes no sense

#761

Post by Symmetry »

beloch wrote: post #115

I would not assume cooling has been worked out. Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot. A satellite is, if nothing else, a fantastic thermos. A data center in space would necessarily rely completely on cooling by radiation, unlike a terrestrial data center that can make use of convection and conduction. You can't just pipe heat out into the atmosphere or build…

Space is a vacuum and yet here we are on a rock floating in space warmed by the sun and the temperate is actually pretty comfortable. Indeed, without the greenhouse effect it would be positively chilly. An important part of a thermos is that you have to use high albedo materials in the vacuum chamber or else it would lose heat too quickly to radiation.

A satellite as a whole will come to thermal equilibrium with space at a fairly reasonable temperature, the problematic part is that the properties of electricity make it easy to concentrate a good part of the incoming energy in a small area where the GPU is. Heat is harder to move than electricity and getting that heat back out to the solar panels or radiators requires either heavy heat pipes or complex coolant pumps.

Re: Data centers in space makes no sense

#762

Post by verzali »

Ajedi32 wrote: post #755
FranklinJabar wrote: post #609

Earlier quoted context omitted.

> There is probably plenty of scope to optimize space radiators. It was never a priority until now and is "just" an engineering problem. Well, it's a physics problem. The engineering solution is possibly not cost efficient. I'd put a lot of money that it isn't.

What makes you so sure? SpaceX already has thousands of 6 kW networking racks flying around in LEO and they dissipate their heat just fine, and are plenty cost-effective. You think they can't do any better than that with a new design specifically optimized for computing rather than networking?

Probably, but they likely can't do better than we can do on Earth. Networking in space offers specific advantages that are not easy to replicate on Earth. Data centers in space don't have clear advantages beyond easily debunked ideas about cooling and power.

Re: Data centers in space makes no sense

#763

Post by Symmetry »

elamje wrote: post #353

I was talking to someone about this the other day. I was part of a team at NASA that developed a cooling system for the ISS and this whole premise makes no sense to me. 1. Getting things to space is incredibly expensive 2. Ingress/egress are almost always a major bottleneck - how is bandwidth cheaper in space? 3. Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire t…

Regarding 3, they're almost certainly thinking of putting these in SSO where the radiation environment isn't too much worse than you see on the ISS. If they were going to go outside the Van Allen belts it would be a different story.

Re: Data centers in space makes no sense

#764

Post by matthewdgreen »

elamje wrote: post #353

I was talking to someone about this the other day. I was part of a team at NASA that developed a cooling system for the ISS and this whole premise makes no sense to me. 1. Getting things to space is incredibly expensive 2. Ingress/egress are almost always a major bottleneck - how is bandwidth cheaper in space? 3. Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire t…

The whole AI bubble makes way more sense if you model it not as rational economic activity, but rather as the actions of a rogue AI slowly taking over our institutions and redirecting them towards its goals. Data centers in space make no sense economically, but think of how survivable the rogue AI will be once we build those orbiting data centers! (I am joking about this, but it's weird that my logic makes sense.)

Re: Data centers in space makes no sense

#765

Post by bunderbunder »

weregiraffe wrote: post #664
bunderbunder wrote: post #236

Earlier quoted context omitted.

My guess is it’s just another example of his habit of trying to use one of his companies to manufacture demand for another of his companies’ products. Specifically: Starship makes no economic sense. There simply isn’t any pre-existing demand for the kind of heavy lift capacity and cadence that Starship is designed to deliver. Nor is there anyone who isn’t currently launching heavy payloads to LEO but the only thing h…

>Specifically: Starship makes no economic sense. Starship can replace Falcon 9 and probably be cheaper, if fully reusable, so more profitable. So at least some economic sense is there already.

I have noticed that there are two radically different approaches to assessing Starship.

One is based on boring old analysis, hard numbers, and, worst of all, continually updating the analysis as more information (e.g., Raptor’s severe expectations vs reality shortfall) becomes available. People who use this approach don’t seem to have an opinion of Starship that is trending upward.

The other approach seems to be based on vibes, and trusting that Starship will meet its original design goals despite the fact that no rocket project has ever come close to such an achievement. If there’s ever any introspection about why Starship should be the exceptional project that actually does meet its performance goals, the conclusion tends to be something about how Starship is special because it’s being developed by a private company. And I’ve noticed that, if the conversation does get to this point, you can send it in all sorts of unpredictable and fascinating directions by saying words like “OTRAG” and “Conestoga.”

Re: Data centers in space makes no sense

#766

Post by adrian_b »

MadnessASAP wrote: post #479
gpt5 wrote: post #235

Earlier quoted context omitted.

I'm confused about the level of conversation here. Can we actually run the math on heat dissipation and feasibility? A Starlink satellite uses about 5K Watts of solar power. It needs to dissipate around that amount (+ the sun power on it) just to operate. There are around 10K starlink satellites already in orbit, which means that the Starlink constellation is already effectively equivalent to a 50 Mega-watt (in a rou…

I ran the math the last time this topic camps up The short answer is that ~100m2 of steel plate at 1400C (just below its melting point) will shed 50MW of power in black body radiation. https://news.ycombinator.com/item?id=46087616#46093316

The temperature of space datacenters will be limited to 100 Celsius degrees, because otherwise the electronic equipment will be destroyed.

So your huge metal plate would radiate (1673/374)^4 = 400 times less heat, i.e. only 125 kW.

In reality, it would radiate much less than that, even if made of copper or silver covered with Vantablack, because the limited thermal conductivity will reduce the temperature for the parts distant from the body.

Re: Data centers in space makes no sense

#767

Post by tgtweak »

The crux of it is that radiative cooling in space is dependent on exposed surface, not total surface area like a radiator or heatsink on earth - this means if you just put an existing finned heatsink in space it would radiate most of it's heat back to itself - the only net cooling you'd have is the amount that can radiate outwards without hitting itself.

For a benchmark - the IIS uses about 4500sqft (420 sqm) of radiators just to keep it's onboard equipment (~70KW) cooled. That's ~150-200 W/sqm.

That means, per GPU, you'd need about 2.5-3.0 sqm of passive radiators.

For a 1MW satellite (~8 datacenter racks of GB200/NVL72) you'd need basically half a football field of bleeding-edge solar panels (that also need to radiate their heat on the reverse side) and a similar sized cooling array of heat radiators for the electronics.

This is on the scale of 40-50 tons - about 10% of the IIS. This should fit on falcon heavy or starship - assuming the solar array and radiators can fold up to fit inside. You could, purely based on weight, launch 2 of these per starship launch.

If you consider the Opex savings (electricity, rent, facilities maintenance) and putting 2 of these on a single starship launch, I still think the ROI would be too long. You're saving about ~$1M per year in Opex but it's costing you $25M to launch it into space and likely an extra ~$50M in satellite equipment (based on starlink satellite costs) on top of the compute. Will those GPUs still be useful in 10 years? Probably not.

I don't think the math is there that justifies the free electricity - even at gigawatt scale (thousands of satellites mass-produced) and at a dramatically lower cost per satellite and per launch. Getting costs down on this would involve tightly integrating the compute and the satellite hardware which would make upgrading the compute independently from the cooling/power infrastructure in the future a significant challenge.

Re: Data centers in space makes no sense

#768

Post by its-summertime »

Symmetry wrote: post #761
beloch wrote: post #115

I would not assume cooling has been worked out. Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot. A satellite is, if nothing else, a fantastic thermos. A data center in space would necessarily rely completely on cooling by radiation, unlike a terrestrial data center that can make use of convection and conduction. You can't just pipe heat out into the atmosphere or build…

Space is a vacuum and yet here we are on a rock floating in space warmed by the sun and the temperate is actually pretty comfortable. Indeed, without the greenhouse effect it would be positively chilly. An important part of a thermos is that you have to use high albedo materials in the vacuum chamber or else it would lose heat too quickly to radiation. A satellite as a whole will come to thermal equilibrium with spac…

a data center in space doesn't have a gigantic rock taking up most of its area, a data center in space is 100% data center 0% rock.

If it had the same data center to rock ratio as earth, it would just end up being earth in the end, and earth doesn't seem to be wanting to stick to its equilibrium either right now

Re: Data centers in space makes no sense

#769

Post by tgtweak »

elamje wrote: post #353

I was talking to someone about this the other day. I was part of a team at NASA that developed a cooling system for the ISS and this whole premise makes no sense to me. 1. Getting things to space is incredibly expensive 2. Ingress/egress are almost always a major bottleneck - how is bandwidth cheaper in space? 3. Chips must be “Rad-hard” - that is do more error correcting from ionizing radiation - there were entire t…

Added some math on my comment that outlines the boundaries of economics of this considering most of what you mentioned.
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