[mrandish]

I was initially very skeptical about the viability of space-based data centers but after a couple hours reading papers, studies and summary technical assessments I realized there are a range of credible expert viewpoints from, "pretty unlikely" to "it could actually work". There at least appear to be plausible, though unproven, solutions to the most obvious drive-by objections I had off the top of my non-expert head.

Of course, there are still a lot of unknowns, any of which could prove fatal to the concept but I'm no longer comfortable just dismissing it as "obviously ridiculous."

[Teever]

Putting a datacentre in space may be feasible but the scale that he's suggesting is really unbelievable.

And if he's actually capable of producing solar panels in the quantity that he's talking about in the time frame that he's talking about -- why doesn't he just put them on earth to solve our growing climate change problems and fuel shortages?

[mrandish]

> but the scale that he's suggesting...

Well, yeah but that's just Elon being Elon. At this point I think even the most pro-Elon folks freely admit "The first rule of Elon is: 'Ignore everything he says about timeframes and scale.'"

[johnsimer]

Permitting/regulation issues

[luke5441]

I think what often gets confused is people saying it isn't viable with "it is not physically possible".

It is physically possible, but it won't have positive ROI so it is not viable.

If you have a paper/post doing the calculations for positive ROI, I'd be all ears. It can even have the optimistic Elon assumptions about price of mass to orbit.

[geertj]

I don’t think people are confused between the two. What’s happening is that drive by objections have no real way to assess viability. That calculation you ask for has line items in it that greatly depend on engineering optimizations that, unless you work in the field, are hard to estimate accurately.

[IshKebab]

I don't think you really need those calculations to know that it is always going to be less viable than a traditional data centre. It's like the idea about putting data centres under water.

I'm sure you can do it and you can come up with estimates over how much it will cost... but it's always going to cost more than not putting your data centre underwater.

[luke5441]

On those line items make the most optimistic assumption. E.g. use Elons Starship cost to orbit. Assume useful GPU lifetime of 6+ years. Assume max physical possible radiators etc.

[saberience]

Yeah you would need 10-20 American football fields worth of radiators for a single data-center... so yes, it "can" work, but it's completely inefficient and unrealistic.

[geertj]

The plan is to launch a constellation of smaller AI sats not a monolithic large data center. The calculations I have seen actually have a smaller radiator area than solar panels. Scott Manley’s has a video on this where he goes into some numbers.

[saberience]

Scott Manley's video uses 20kw as a reference number which isn't even half of the power usage of a modern GB200 rack. I.e. not even close to the power usage of an actual datacenter. In fact, not even 1% of the power usage of a datacenter...

Also, how is a constellation of satellites any easier in this case? They all need extremely large radiators, they all need maintenance, they all need high bandwidth communication.

If you calculate the actual cooling requirements for megawatts of server, you end up with needing many, many football fields of cooling.

It's nonsensical. Sure you can make the numbers sort of work for a single server, but a single server on earth costs MUCH MUCH less to launch, maintain, etc. So why bother doing it in space? We just end up with loads of unusable space servers as they gradually breakdown and cannot be repaired.

[randallsquared]

In fact, not even 1% of the power usage of a datacenter...

Right, but SpaceX has already filed plans with the FCC to launch a million of them, which is to say, 10K of your datacenter units. Tying back to the article, this plan is definitely going to require Starship and airline-like operations.

[Symmetry]

Yeah. I don't have any doubts that this is something that can be done. But doing it cheaply enough to be worth while is the difficult bit. Elon does have reputation for delivering impressive things, but not for finishing them on the deadlines he sets.

[saberience]

Ok, how many Starship launches have there been so far? Ok, 11 tests, of which only one has sent a dummy payload. Of the 11 tests, you can say that the latest one was closest to a final (sort of) working version. So we're still very early in the Starship launch program.

Let's do the math on "millions of datacenters" worth of launches.

In fact, let's try and do it for a single 50k GPU datacenter:

50,000 GPUs at GB200 density = 695 NVL72 racks at 1360 kg (1.36 tonnes) each, so the racks are roughly 950 tonnes.

GPUS = 950 tons

85MW of power needed for the GPUs. Latest solar power panels give roughly 120-150 watts per kg. Let's be generous and say 150 W/kg. So 85 MW / 150 W/kg = 570 tonnes of solar arrays

Power = 570 tons

Thermal management (radiators). Real space radiators are around 12 kg/m² for a heavy deployable radiator and its support structure, though ISS radiators are 8 kg per square meter, or 2.75 kg/m² if we only consider the exposed panels. (Using 8 kg/m² for an estimate). 200,000 m² × 8 kg/m² = 1,600 tonnes of radiators

Plus working fluid (ammonia or similar), pumps, manifolds, redundant loops: 150 tonnes.

Radiators Total: 1750 tons.

Structure, Propulsion, Comms, Avionics, Attitude Control Systems, plus Margin. Hard to estimate but conservatively several hundred tons extra. (Actual spacecraft programs always add roughly 20-30% mass margin).

Extras: 750 tons. (being very conservative).

Total = 950+570+1750+750 = 4020 tons.

And note, this is for a single 50k GPU datacenter with all the numbers being skewed to most optimistic.

That would be 40 (!!!) Starship launches. So far we've had 11 launches total with none being successful (100% successful I mean). Each of those launches currently costs 90M dollars. And note, we are assuming a fully working 100 ton payload for Starship of which none of the launches so far have been close to at all.

So our full datacenter to space would cost 3.6B dollars (at current SpaceX prices)... (just to launch it, not to actually buy the equipment). And realistically would cost far more than that...

Note, this is for (by today's standards) a small datacenter with only 50k GPUs and I haven't included any testing, R&D costs, costs of "maintenance", station keeping, replacements, etc etc.

Let alone the question of huge amounts more satellites in orbit, risks of space junk, Kessler syndrome, etc etc.

[db48x]

You’re way overestimating the size of the radiators needed. Then you overestimate their mass, because the ISS has huge heavy radiators that operate at <30°C. A rack of computers can run at much higher temperatures and therefore need much smaller, lighter radiators. The radiators would be smaller and lighter than the solar panels.

[randallsquared]

I have a lot of miscellaneous quibbles with your assumptions and numbers, but even if you grant many of them, 40 launches is not many for Starship's planned cadence. HLS is going to require 10-16 Starship launches just to get it fueled enough for one landing, and they have to be close enough together to minimize boil-off.

[amoss]

Later in the video he runs through the changes needed for 100kw per rack.

[saberience]

Wow, one 100kw rack!

Dude, you realize that right now there are 100+s of data centers in construction around the world often in the 500MW to 1PW range? I.e. there are many, many datacenters (100s) in construction, right now, with 100s of MW up to multiple PW?

Scott's analysis is out by several orders of magnitude!

Everyone knows its "theoretically" possible to have a single server or a single rack in space.

The big and most obvious glaring miss is, how would it be economically viable and operationally viable to have datacenters in space which compete with datacenters on the ground.

We are experts are creating economically profitable (very profitable) datacenters on the ground, which work really well for inference and training, which are cooled really well, can be maintained easily, etc. The idea that we are going to have 100s of MW clusters or 1PW clusters in space, and they are going to be competitive economically, and we are going to be able to maintain them, and they are going to actually WORK (i.e. how will the networking be competitive with datacenters on earth), is frankly laughable.

Scott is totally talking rubbish on this.

[amoss]

Nobody said one rack. Your entire rant is misguided. He analyzed what it would take to put one rack on one starlink like package in order to build a constellation.

[xnx]

There are a lot of things that are possible that make no financial sense.

[saalweachter]

If you spot Datacenters In Space as making sense, why does SpaceX acquiring XAi make sense to do it?

Why not have SpaceX build datacenter satellites and lease them to XAi et al, or XAi design and manufacture satellite datacenters and pay SpaceX to launch them? Heck, why not start a third company which focuses exclusively on datacenters in space, buying services from one company and selling them to another, so they can concentrate on this rather specialized skillset without distraction?

How does SpaceX acquiring XAi help anything but Elon Musk's personal portfolio?

[mrandish]

> why does SpaceX acquiring XAi make sense to do it?

I never said it did. My post didn't even mention SpaceX, Elon or XAI. I just shared that my initial drive-by opinion on space-based compute, as a general concept (regardless which company does it, when or how), was reflexively dismissive but after a tiny bit of research, it's now risen to the lofty epistemic level of "not completely ridiculous." And I discovered it's a much more interesting and complex question than I assumed, involving highly uncertain estimates of rapidly evolving technology, physics and economics.

For me the question starts more akin to "could a Dyson sphere ever be viable for human civilization in this solar system" than "should grandma invest her life savings in SpaceX this afternoon." But it seems some can't reason about the potential future viability of space-based compute independent of current politics, personalities, culture war or whether AI is a bubble inflated by circular deals. To be clear, I do think AI valuations are wildly over-inflated and propped up by financial engineering bordering on fraud likely to trigger a huge economic crash. But it can be simultaneously true that there will be hugely profitable AI businesses in 2035 and it's possible space-based compute might be viable for some company in 2040.

As for Elon, ever since I met him a couple times closer to the Paypal days, I've felt he's an eccentric, impulsive nut but that he's also a savvy, technically-minded entrepreneur with a sharp eye for opportunity who's compelled by obsessive, visionary zeal. And everything he's done since has been consistent with that assessment, from the successes of Tesla and SpaceX to his bizarre, self-destructive detours into politics, social media and AI. I don't understand why so many can't deal with the reality that a person can be deeply flawed and wildly irrational in some ways while simultaneously being highly effective and immensely valuable in other ways. Steve Jobs was a brilliant visionary entrepreneur yet also an asshole in his personal life who believed some crazy shit so deeply it contributed to his early death.

[foxylad]

Did you find a credible solution for heat dissipation in the papers you read? I fear the laws of thermodynamics will kill this project.

[hvb2]

https://youtu.be/FlQYU3m1e80

Is a good start