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Comment by vlovich123 | Hacker News Reader

The Microsoft design of filling an airtight submersible structure with argon and dropping it to the bottom of the ocean floor is the alternative design - you’re not looking to do repairs but amortize the low cost of failures across the value you extract.

The biggest issue with space is not repairability but heat - when you’re in a vacuum the only way to disperse heat is through black body radiation and that’s horribly slow compared with normal mechanisms. It means you need giant physical structures whose sole job is to accept heat from the processing core and radiate it away and have so much more material that you can radiate it at the speed you generate. It’s a huge unsolved physics problem which is why everyone is skeptical.

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It’s not an unsolved physics problem. Every satellite in space has to deal with it and even the ISS deals with it by having massive radiator arrays that face perpendicular to the sun.

The problem with data centers in space is one of materials science and engineering: how to make radiators large enough and effective enough to cool it while also being economically feasible, both in terms of construction and getting them up there in the first place.

We can make a space data center right now. It would just be terrible and expensive.

I think it's not necessarily about being the cheapest option, but a more politically acceptable one. I don't think you're going to get people protesting a data center in space considering it won't be next to their house, won't use water, and won't lead to increased electricity rates. I could see companies paying a premium to keep the political heat associated with traditional data centers off their backs.

The physics problem regarding radiator arrays isn't unsolved, but it's not a problem that scales up gracefully. Small-scale radiators could get by via passive cooling, but large-scale radiators need active cooling, and now you need fluid, pipes, and pumps that all represent additional launch mass and points of failure (and the pumps are generating heat of their own, so now you need more radiators...).

Doesn't active cooling provide counterbalancing options to improve efficiency though? For example, use multi-stage heat pumps with different refrigerants so that you can make the hot side very hot and thereby need less mass for radiators.

Thermal dissipation scales quartically with T, that's about as graceful as you can get from a physics POV, very few things scale at that rate.

COTs GPUs throttle at about 90-100C but that's because they have plastic parts and solder that melts. Those are relatively easy to eliminate.

We haven't tried much to scale up operating temp.

Apple tried the damnedest at that during their intel era. Silicon gets exponentially leakier at higher temperatures, and that will outpace quadratic growth easily.

(Electronics that works at 200C do exist, but they're not gonna meet a modern smartphone's specs, let alone a datacenter)

>Apple tried the damnedest at that during their intel era.

The story I heard was intel failed to deliver on die shrinks that were supposed to increase thermal efficiency. The fan also had poor routing and basically did nothing.

Apple was clearly not at the top of their game for that design, nor would you expect them to be as the decision was likely already made to move to apple silicon.

So what’s the unsolved physics problem? Everything you’re describing are engineering challenges.

Nobody said space data centers are impossible, it’s just wasteful and ineffective.

Right, but nobody's sure just how wasteful. And at these scales small factors make or break things. That's why it's hard to predict who's bullshitting. A fairly small unforeseen factor here and there adds up to wild financial success or failure over the course of an entire project.

I think that's an incorrect way of looking at it. A small unforeseen factor is almost always going to be a negative factor, not an unforeseen benefit. Space is a hostile and unforgiving environment without an easy way to bring things back, fix stuff, and/or re-deploy. A small mistake on the engineering, planning and/or implementation is likely to sink the whole thing worse than the napkin math suggests is almost certain failure anyway. Similarly, there are few ways to "get it right" and many ways to fail.

The maximum heat rejection capacity of the ISS is 126Kw.

Musk’s proposal is to put 1 rack per satellite drawing 150kw using 110 m^2 of radiators (1/4th that of the ISS). The only way to do that is by running the satellite at 71-100C which is a problem for the chips to actually run.

So the open questions are: * can they actually dump the heat and can they have the racks running so hot for so long * is it economical to in one year replace all the capacity you launched 5 years ago (you save up to 0.5B in electricity costs over that time frame but that doesn’t seem like a lot for having to replace that much capacity buildup)? And given they’re running racks way hotter than has been validated on earth, will those chips end up lasting 5 years (including space radiation).

Pretending like it’s a solved problem is neat but I’m not saying sure it’ll be so easy.

Those temperatures aren't necessarily a problem for the chips (there are some minor design changes needed, so it's more a question of having enough volume to justify doing it). The real issue is that this is yet another thing you could do better on earth.

In other words, run fully lights-out datacentres that no humans will access during normal operation - this allows you create more extreme temperature gradients and to replace the atmosphere with CO2 (or even He2), both of which will make your cooling solution much more efficient as well as increasing rack density and perhaps even taking the place of a fire suppression system.

The reason that no-one's actually doing that at scale is that it's currently significantly more expensive than traditional datacentre designs. And yet, that's still much less expensive than boosting racks into space and then letting them burn up in the atmosphere five years later.

It’s as solved as FSD.

Wouldn't it be possible to use heat pumps, making radiators 100C or hotter while running GPUs much below that?

That's how space heat radiators already work. Which, by the way, add significant costs to both energy and weight for space-based data center. The problem is once you 'pump' the heat out is what happens next. With out conductive or convective heat transfer, all that is left is radiation of that heat. Which is the slow.

> It’s not an unsolved physics problem. Every satellite in space has to deal with it and even the ISS deals with it by having massive radiator arrays that face perpendicular to the sun.

The problem is not solved for something of this scale, I think its solvable, but no has done anything at the size these would have to be. And if the physics and engineering can be made to work, they are unlikely to be solved AND ALSO be economical.

It's classic type problem where the choices are:

- economical

- in-space

- big

Now pick two.

There is also the unsolved problem that the radiators would be absolutely massive in area. Making damage from flying objects, meteorites, space jump, close to 100% likely over any reasonable life span. Repairs would be expensive AF. Again economics is the driver of why this is dumb.

Right, a heat exchange is reusable though on earth and can be recycled across multiple SKUs and thus depreciates longer. In space similar to how you can’t repair you also can’t swap.

It's so, so cheap to buy tap water and dump it on the heat exchange.

With well considered engineering it doesn't even need to be tap water. If you have a closed loop thermal conductor that interacts with the components themselves you can then use really trashy contaminated water that just needs to be clean enough not to actively erode the heat transfer mechanism. We have setups like this all the time that use condensed air via cooling towers or salt water immersed heat sinks to discharge energy - it's more expensive than tap water but it isn't technically complex. So if it ever becomes unpalatable (likely due to politics) to use tap water there are some readily available alternatives.

The big win of being in space is just a worse alternative to using an intermediary heat transfer medium.

It's the same reason we use single use plastics. No matter the politics the business decision is going to use the cheapest option available. I'm confident that all the hyperscalers could create datacenters that don't affect the local community basically in anyway. There's been data centers hidden in plain sight for decades. The demand drives it to the lowest common denominator

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