Comment by alangibson
8 hours ago
Either this is a straight up con, or Musk found a glitch in physics. It's extremely difficult to keep things cold in space.
8 hours ago
Either this is a straight up con, or Musk found a glitch in physics. It's extremely difficult to keep things cold in space.
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...
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.
I find HN and the tech circles to be one of the main community pillars holding up X. None of my social friends use it anymore, but links absolutely abound here, and it seems like the standard line is to pretend Elon, Grok, all the one button revenge and child porn etc don’t exist. I truly can’t fathom the amount of not thinking about it it would take to keep using the platform.
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I am with you 100%.
It was easy to support SpaceX, despite the racist/sexist/authoritarian views of its owner, because he kept that nonsense out of the conversation.
X is not the same. Elon is actively spewing his ultraconservative views on that site.
Now that these are the same company, there's no separation. SpaceX is part of Musk's political mission now. No matter how cool the tech, I cannot morally support this company, and I hope, for the sake of society, it fails.
This announcement, right after the reveal that Elon Musk reached out to Jeffrey Epstein and tried to book a trip to Little St. James so that he could party with "girls", really doesn't bode well.
It's a shame you can't vote these people out, because I loved places like Twitter, and businesses like SpaceX and Tesla, but Elon Musk is a fascist who uses his power and influence to attack some of the most important pillars of our society.
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> 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.
Twitter also has more (not total, but more) free speech than any other social networking site. For example, you are allowed to discuss empirical research on race, crime and IQ. That would get you rate limited or banned quickly on other websites, including HN.
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?
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.
The point of the Starship program is to drop the cost of a kg going to space significantly - this isn't meant to be launched with rockets that aren't fully reusable.
The ISS creates radically less heat than a datacenter
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.
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.
Wouldn't they?
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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.
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
The ISS isn't consuming and generating megawatts+ of power.
Yes but if the solar panel area scales linearly with radiator area, the problem doesn't get worse?
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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.
If you solve 2, heat dissipation goes away on earth too, so what’s the advantage of space
I'm not the best person to make that case as I can only speculate (land cost, permitting, latency, etc). /Shrug
In all the conversations I've seen play out on hacker news about compute in space, what comes up every time is "it's unviable because cooling is so inefficient".
Which got me thinking, what if cooling needs dropped by orders of magnitude? Then I learned about photonic chips and spintronics.
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> space is called “space” for a reason.
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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.
> new technology improves vacuum heat radiation efficiency
Isn't this fixed by blackbody radiation equations?
That equation have surface area ? What if new material found to be extremely large surface area to weight ratio to dissipate lots of heat ?
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.
If they AI business is failing why did they just do a successful large raise?
Maybe Karpathy has been hired to design a Full Self Cooling system.
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.
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.
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.
you put the radiators and the rest of the satellite within the shade of the solar panels, you can still make the area arbitrarily large
EDIT: people continue downvoting and replying with irrelevant retorts, so I'll add in some calculations
Let's assume
1. cheap 18% efficient solar panels (though much better can be achieved with multijunction and quantum-cutting phosphors)
2. simplistic 1360 W/m^2 sunlight orthogonal to the sun
3. an abstract input Area Ain of solar panels (pretend its a square area: Ain = L ^ 2)
4. The amount of heat generated on the solar panels (100%-18%) * Ain * 1360 W / m ^ 2, the electrical energy being 18% * Ain * 1360 W / m ^ 2. The electrical energy will ultimately be converted to computational results and heat by the satellite compute. So the radiative cooling (only option in space) must dissipate 100% of the incoming solar energy: the 1360 W / m^2 * Ain.
5. Lets make a pyramid with the square solar panel as a base, with the apex pointing away from the sun, we make sure the surface has high emissivity (roughly 1) in thermal infrared. Observe that such a pyramid has all sides in the shade of the sun. But it is low earth orbit so lets assume warm earth is occupying one hemisphere and we have to put thermal IR reflectors on the 2 pyramid sides facing earth, so the other 2 pyramid sides face actual cold space.
6. The area for a square based symmetric pyramid: we have
6.a. The area of the base Ain = L * L.
6.b. The area of the 4 sides 2 * L * sqrt( L ^ 2 / 4 + h ^ 2 )
6.c. The area of just 2 sides having output Area Aout = L * sqrt( L ^ 2 / 4 + h ^ 2 )
7. The 2 radiative sides not seeing the sun and not seeing the earth together have the area in 6.c and must dissipate L ^ 2 * 1360 W / m ^ 2 .
8. Hello Stefan-Boltzmann Law: for emissivity 1 we have the radiant exitance M = sigma * T ^ 4 (units W / m ^ 2 )
9. The total power exited through the 2 thermal radiating sides of the pyramid is then Aout * M
10. Select a desired temperature and solve for h / L (to stay dimensionless and get the ratio of the pyramid height to its base side length), lets run the satellite at 300 K = ~26 deg C just as an example.
11. If you solve this for h / L we get: h / L = sqrt( ( 1360 W / m ^ 2 / (sigma * T ^ 4 ) ) ^ 2 - 1/4 )
12. Numerically for 300K target temperature we get: h/L = sqrt((1360 / (5.67 * 10^-8 * 300 ^ 4)) ^ 2 - 1/4) = 2.91870351609271066729
13. So the pyramid height of "horribly poor cooling capability in space" would be a shocking 3 times the side length of the square solar panel array.
As a child I was obsessed with computer technology, and this will resonate with many of you: computer science is the poor man's science, as soon as a computer becomes available in the household, some children autodidactically educate themselves in programming etc. This is HN, a lot of programmers who followed the poor man's science path out of necessity. I had the opportunity to choose something else, I chose physics. No amount of programming and acquiring titles of software "engineer" will be a good substitute for physicists and engineers that actually had courses on the physical sciences, and the mathematics to follow the important historical deductions... It's very hard to explain this to the people who followed the path I had almost taken. And they downvote me because they didn't have the opportunity, courage or stamina to take the path I took, and so they blindly copy paste each others doomscrolled arguments.
Look I'm not an elon fanboy... but when I read people arguing that cooling considerations excludes this future, while I know you can set the temperature arbitrarily low but not below background temperature of the universe 4 K, then I simply explain that obviously the area can be made arbitrarily large, so the temperature can be chosen by the system designer. But hey the HN crowd prefers the layers of libraries and abstractions and made themselves an emulation of an emulation of an emulation of a pre-agreed reality as documented in datasheets and manuals, and is ultimately so removed from reality based communities like physics and physics engineering, that the "democracy" programmers opinions dominate...
So go ahead and give me some more downvotes ;)
If you like mnemonics for important constants: here's one for the Stefan Boltzman constant: 5.67 * 10^-8 W / m^2 / K ^ 4
thats 4 consecutive digits 5,6,7,8 ; comma or point after the first significant digit and the exponent 8 has a minus sign.
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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.
the radiators would be lighter compared to the solar panels, and slightly smaller surface area so you can line them back to back
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> 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.
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.
Water is not needed to move heat. Heat pipes do it just fine. There's one in your laptop and one in your phone too. It does scale up.
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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.
> 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.
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.
Just put a fan in a window.
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.
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.
please check my didactic example here: https://news.ycombinator.com/item?id=46862869
"Radiators can shadow each other," this is precisely why I chose a convex shape, that was not an accident, I chose a pyramid just because its obvious that the 4 triangular sides can be kept in the shade with respect to the sun, and their area can be made arbitrarily large by increasing the height of the pyramid for a constant base. A convex shape guarantees that no part of the surface can appear in the hemispherical view of any other part of the surface.
The only size limit is technological / economical.
In practice h = 3xL where L was the square base side length, suffices to keep the temperature below 300K.
If heat conduction can't be managed with thermosiphons / heat pipes / cooling loops on the satellite, why would it be possible on earth? Think of a small scale satellite with pyramidal sats roughly h = 3L, but L could be much smaller, do you actually see any issue with heat conduction? scaling up just means placing more of the small pyramidal sats.
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
attitude control doesn't need to consume propellant, there's reaction wheels.
but you'd rarely ever need it though: it just needs to rotate at a low angular velocity of 1 rotation per year to keep facing the sun.
https://en.wikipedia.org/wiki/Spacecraft_attitude_determinat...
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?
Fluid in heat pipes moves through capillary action.
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.
No, we just "assume" (i.e. know) that radiation in a vacuum is a really bad way of dissipating heat, to the point that we use vacuum as a very effective insulator on earth.
Yes, you can overcome this with enough radiator area. Which costs money, and adds weight and space, which costs more money.
Nobody is saying the idea of data centers in space is impossible. It's obviously very possible. But it doesn't make even the slightest bit of economic sense. Everything gets way, way harder and there's no upside.
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what? the heat is coming from inside the house
which house?