[alangibson]

Either this is a straight up con, or Musk found a glitch in physics. It's extremely difficult to keep things cold in space.

[darth_avocado]

He buys twitter at an inflated valuation. Runs it to the ground to a much lower valuation of $9B. [1] Then, his company Xai buys Twitter at a $33B, inflating the valuation up. Then SpaceX merges with Xai for no particular reason, but is expected to IPO at a $1T+ in the upcoming years. [3]

I’m not that smart, but if I were, I would be thinking this is an extended way to move the losses from the Twitter purchase on to the public markets.

[1] https://www.axios.com/2023/12/31/elon-musks-x-fidelity-valua...

[2] https://www.reuters.com/markets/deals/musks-xai-buys-social-...

[3] https://www.cnbc.com/amp/2026/02/02/elon-musk-spacex-xai-ipo...

[SilverElfin]

It also makes it impossible for Twitter/X to die, as it deserves. It is by far the most toxic mainstream social network. It has an overwhelming amount of far right supremacist content. So bad that it literally resulted in Vivek Ramaswamy, a gubernatorial candidate in Ohio, to quit Twitter/X - nearly 100% of replies to his posts were from far right racists.

Obviously advertisers have not been fans. And it is a dying business. But rather than it dying, Elon has found a clever (and probably illegal) way to make it so that SpaceX, which has national security importance, is going to prop up Twitter/X. Now our taxpayer dollars are paying for this outrageous social network to exist.

[nutjob2]

It's a con, his AI business is failing, so he's rolling it up into the profitable business. Did a similar thing with Twitter.

This is so obvious, but it's so stupid and at this scale that people find it hard to believe.

[DoesntMatter22]

If they AI business is failing why did they just do a successful large raise?

[dahinds]

This isn't really true, though? The ISS does it with radiators that are ~1/2 the area of its solar panels, and both should scale linearly with power?

[alangibson]

ISS radiators run on water and ammonia. Think about how much a kg costs to lift to space and you'll see the economics of space data centers fall apart real fast. Plus, if the radiator springs a leak the satellite is scrap.

[wild_egg]

The ISS creates radically less heat than a datacenter

[IvyMike]

I don't pretend to understand the thermodynamics of all of this to do an actual calculation, but note that the ISS spends half its time in the shadow of the earth, which these satellites would not do.

[el_nahual]

Radiator size scales linearly with power but, crucially, coolant power, pumps, etc do not.

Imagine the capillary/friction losses, the force required, and the energy use(!) required to pump ammonia through a football-field sized radiator panel.

[nomilk]

Also, space solar is around 4-8x more efficient (24h/day full sun instead of ~4-8 on Earth), and 40% gain due to no atmospheric loss.

[wongarsu]

Moving electricity long distance is a lot easier than moving coolant long distances, which puts a soft limit on the reasonable size of the solar array of these satellites. But as long as you stay below that and pick a reasonable orbit it's indeed not too bad, you just have to properly plan for it

[invalidusernam3]

Here's an interesting post linked elsewhere in this thread https://taranis.ie/datacenters-in-space-are-a-terrible-horri...

[FireBeyond]

The ISS isn't consuming and generating megawatts+ of power.

[nhq1298]

Maybe Karpathy has been hired to design a Full Self Cooling system.

[umeshunni]

> It's extremely difficult to keep things cold in space.

This is one of those things that's not obvious till you think about it.

[FloorEgg]

Setting aside the possibility it's window dressing for a financial bailout, there would be two ways compute in space makes sense:

1) new technology improves vacuum heat radiation efficiency

2) new technology reduces waste heat generation from compute

All the takes I've seen have been focused on #1, but I'm starting to wonder about #2... Specifically spintronics and photonic chips.

[brandonlovesked]

If you solve 2, heat dissipation goes away on earth too, so what’s the advantage of space

[TheDong]

1. It's cheaper to make a vacuum on earth around a computer than it is to send a computer into space.

2. That would also presumably work on earth, unless it somehow relied on low-gravity, and would also be cheaper to benefit from on earth.

[tbrownaw]

> new technology improves vacuum heat radiation efficiency

Isn't this fixed by blackbody radiation equations?

[pantalaimon]

Existing satellites manage to keep their equipment that already can consume several kW cool just fine.

You might need space for radiators, but there is plenty space in space.

[nerdsniper]

5,000 Starship launches to match the solar/heat budget of the 10GW "Stargate" OpenAI datacenter. The Falcon 9 family has achieved over 600 launches.

The ISS power/heat budget is like 240,000 BTU/hr. That’s equivalent to half of an Nvidia GB200 NVL72 rack. So two international space stations per rack. Or about 160,000 international space stations to cool the 10GW “Stargate” datacenter that OpenAI’s building in Abilene. There are 10,000 starlink satellites.

Starship could probably carry 250-300 of the new V2 Mini satellites which are supposed to have a power/heat budget of like 8kW. That's how I got 5,000 Starship launches to match OpenAI’s datacenter.

Weight seems less of an issue than size. 83,000 NVL72’s would weigh 270 million lbs or 20% of the lift capacity of 5000 starship launches. Leaving 80% for the rest of the satellite mass, which seems perhaps reasonable.

Elon's napkin math is definitely off though, by over an order of magnitude. "a million tons per year of satellites generating 100 kW of compute power per ton" The NVL72's use 74kW per ton. But that's just the compute, without including the rest of the fucking satellite (solar panels and radiators). So that estimate is complete garbage.

One note: If you could afford to send up one of your own personal satellites, it would be extremely difficult for the FBI to raid.

[alangibson]

Several kW is nothing for a bank of GPUs.

Radiators in space are extremely inefficient because there's no conduction.

Also you have huge heat inputs from the sun. So you need substantial cooling before you get around to actually cooling the GPUs.

[TheGRS]

I'm not big on this subject, but I understand that heat transfer is difficult in space, because there's little to transfer to. If the solution is just making large radiators, then that means you're sending some big payloads full of radiators. Not to mention all the solar panels needed. I wanna live in sci-fi land too, but I don't see how it makes any sense compared to a terrestrial data center.

[Aurornis]

> keep their equipment that already can consume several kW cool just fine

That's equivalent to a couple datacenter GPUs.

> You might need space for radiators, but there is plenty space in space.

Finding space in space is the least difficult problem. Getting it up there is not easy.

[eldenring]

You can line the solar panels and radiators facing away from each other, and the radiators would take up less surface area. I think maybe the tricky part would be the weight of water + pipes to move heat from the compute to the radiators.

[wat10000]

There's plenty of space in space, but there isn't plenty of space in rocket fairings, nor is there plenty of lift capacity for an unlimited amount of radiators.

[kristjansson]

The physical constraints aren’t insane for black body radiators. The engineering to run radiators at 90C in space OTOH…

[JeremyNT]

It's such bullshit that we've decided this moron and others in his cohort can unilaterally reallocate such vast portions of humanity's labor at their whims.

This is an extremely stupid idea, but because of our shared delusion of capitalism and the idea that wealth accumulation at the top should be effectively limitless, this guy gets to screw around and divert actual human labor towards insane and useless projects like this rather than solving real world problems.

[Wilder7977]

I wanted to come and express this thought, but you did that already very well, thanks for that.

I am saddened too by the fact that the system is designed so that people like him can waste a large amount of economic and human capital.

[pupppet]

Just put a fan in a window.

[DoctorOetker]

what makes you believe this?

radiators can be made as long as desirable within the shade of the solar panels, hence the designer can pracitically set arbitrarily low temperatures above the background temperature of the universe.

[c1ccccc1]

Radiators can shadow each other, so that puts some kind of limit on the size of the individual satellite (which limits the size of training run it can be used for, but I guess the goal for these is mostly inference anyway). More seriously, heat conduction is an issue: If the radiator is too long, heat won't get from its base to its tip fast enough. Using fluid is possible, but adds another system that can fail. If nothing else, increasing the size of the radiator means more mass that needs to be launched into space.

[alangibson]

Shading does work; JWST does this. However I don't see how you can make it work for satellite data centers. You would constantly be engaging attitude control as you realigned the panels to keep the radiators in shade. You'd run out of thruster fuel so fast you'd get like a month out of each satellite

[eldenring]

these same comments pop up every time someone brings up satellite data-centers where people just assume the only way of dissipating heat is through convection with the environment.

[DontBreakAlex]

Radiators can only be made as long as desirable because there's gravity for the fluid inside to go back down once it condenses. Even seen those copper heat pipes in your PC radiator?

[ares623]

what? the heat is coming from inside the house