Cooling in Space | Hacker News Reader

Cooling in Space

guille.site

35 pointsLolWolf95 comments

Space data centers are physically possible but don't make financial sense. The total cost of an orbital datacenter over five years is at least 2–3x that of a terrestrial one.

But those economics don't matter to SpaceX, because the main purpose of its orbital data centers is to create a use case for Starship. Starship has to fly frequently to iron out the kinks, encounter and fix rare (1/1000) failure situations, and optimize the launch cadence which pushes launch costs down. Plus Starship needs to fly a lot before it's ready for crewed flight. The long-term goal is a Starship optimized for crewed interplanetary travel. Orbital data centers are a payload that bring in some revenue, and provide a reason to launch constantly.

It's the same thing they did with Starlink to make Falcon 9 as reliable and rapidly reusable as it is.

My guess is: it just sounds cool.

Like the cybertruck

2-3x sounds like a very low estimate.

There’s so much data center capacity being built all over the Earth. Thousands of large projects across US / China / Europe / Middle East. It would be astonishing if something that’s never been done before could be so cost-competitive immediately.

Starlink wasn’t the first time LEO communications constellations were attempted. Multiple 1990s projects did it (Iridium, GlobalStar…) and went bankrupt.

It took 30 years to make the concept work. SpaceX investors seem to be assuming the space data center business will be immediately viable.

SemiAnalysis' report on orbital data centers estimated 4x terrestrial costs in 2026, then parity around ~2040.

https://newsletter.semianalysis.com/p/to-boldly-go-the-case-...

Based on very specific assumptions: “…the world in which AI demand is so overwhelming as to exceed the already formidable datacenter capacity additions” — but also this same world is one where GPU chip supply is abundant, there just isn’t enough data centers to put them in.

This does not seem like the likeliest scenario to me.

Agreed, how could we not have datacenter capacity for the GPUs when Meta has shown that you can go from a bare field to an operational datacenter in about 3 months by using tents instead of buildings?

How hard would it be to weatherproof a GPU computing rack? Like how much more cost would it add? So theoretically you could even forgo tents. Just have them at field. Technically you could even maybe run them in freeports. Thus saving any tariff costs...

You don't even have to weatherproof the rack, putting racks into shipping containers is already done to some extent (and multiple deployments are to my knowledge working fine). It is often also marketed as "module data centers".

The main problem here is that it reduces efficiency (cooling a large datacenter is more efficient per Watt of dissipated heat than a shipping container) and increases initial cost (building in a shipping container is not actually as easy as doing it in a normal-ish building).

Portability (when offline, you can put a shipping container like this on a truck and cart it around) and availability (no need for a new/refit building, only power is required and could be included in the container with a generator (gas/diesel)) are the main reasons for accepting a higher TCO here.

it sort of makes sense, if the need for that compute is in space and not terrestrial.

In my mind its the same sort of thing as mining in space. it makes no sense to mine ores in space for delivery to earth (unless its something exotic that you cant get on earth). Mining in space is best used for manufacturing in space (and furthering building in space)... then the cost benefit ratio suddenly flips hard in the "worth it" direction.

Yeah, there are some established needs for compute in space (edge processing for large datasets collected in space, and autonomous spacecraft control) that already happen to some extent and will happen a lot more with greater volumes of EO/SSA data collected and increasing militarization of space. They just don't look much like a datacentre for inference compute

The computation in TFA is wrong.

The incoming power is not the electrical power generated by the solar panels, but the entire power of the light that is absorbed by the solar panels and by the body of the satellite.

Even with a perfectly reflecting body and with SOTA solar panels, the amount of incoming power is at least double in comparison with the electrical power consumed by the datacenter.

Also, the heat radiated is smaller than in TFA, because no radiator is perfectly black at the radio waves in the frequency range corresponding to the ambient temperature.

I am too lazy to make the correct computation, but there was another article linked on HN some days ago where a more plausible computation was done and the conclusion was that the minimum area of the radiators is slightly larger than the area required for solar panels.

This would still be feasible, but in reality the area would have to be even larger, because the radiator cannot have a uniform temperature, the parts where the cooling fluid is incoming will be hotter than the parts where the cooling fluid is outgoing. Moreover, the pumping of the cooling fluid requires extra power that must be added to the power budget.

There is no doubt that it is possible to build a space datacenter, if much more GPUs are installed in it than necessary, to enable to correct the more severe transient errors and to preserve enough capacity after many GPUs become permanently defective, but the cost will not be competitive with terrestrial datacenters any time soon.

There are other options:

https://spectrum.ieee.org/orbital-data-centers-heat#liquid-d...

https://en.wikipedia.org/wiki/Liquid_droplet_radiator

( Myself from 4 months ago: https://news.ycombinator.com/item?id=46895344 (giggle)

https://spectrum.ieee.org/microfluidics-cooling-ai-chips-cor... )

I went in wanting this to look real bad. But the Scott Manley video alas has sort of convinced me this is pretty feasible, that the energy budget is quite doable. https://youtu.be/FlQYU3m1e80

I do think this is a pretty generous estimate he ends up at. I don't think emissivity is perfectly well dealt with. I don't know if his earth reflection emissivity includes the high energy thermal transfer from particles that do exist on the near vacuum (exosphere be hit, ya'll) or if that matters. But his figures seem ballpark correct & my concerns are at best marginal.

I vaguely recall the Scott Manley video (longtime follower of his channel) - wasn’t he assuming that the chips can be run hot, and because the T^4 factor it results in much better radiative cooling?

I don’t know if the “chips can be run hot” assumption is a fair one. It results in significant degradation of the chips life.

At minimum it needs a redesign of the current set of leading chips which are designed for a specific temperature range. Redesigning at a different operational temperature is not a walk in the park.

He starts with something hot today but viable, 80C. And he goes on to cite and discuss a M*sk tweet about hotter, 97C, and what that density that enables. https://youtu.be/FlQYU3m1e80#t=13:48 and https://youtu.be/FlQYU3m1e80#t=22:11

Allow me to propose a modest alternative to space data centers, namely mountaintop data centers. This would consist of a container full of servers and GPUs and what else goes into a data center, a wind turbine for power and a communication module (say laser or microwave) for communicating with a base station with a fiber connection. This would be lifted on top of a mountain by a helicopter and bolted in place. Cooling would be provided by heat sinks exposed to the outside air. Some of the nodes could relay traffic from other nodes on remote mountain tops out of sight of the base station.

This scheme has many advantages over space data centers including launch costs, cooling, connection latency, servicability and ease of recycling.

What about the rough weather and difficulty of maintenance, especially in rough weather?

Maintenance for a mountaintop data center only requires a team of skilled mountaineers. In space you'd need astronauts. It's at least an order of magnitude cheaper, perhaps two or three.

Nobody is doing maintenance on a small cluster in a satellite. It's disposable with a timespan of less than a decade to recoup all costs. Note that the usual argument to retire hardware is the electrical costs but when you've got lifetime solar you can run it indefinitely.

Nobody is doing maintenance on an orbital data center because it's too expensive and dangerous, not because it wouldn't be useful. Maintenance in space would in fact be way more useful than on land because the redundancy required by a lack of maintenance necessitates extra mass.

If you could pay a few space sherpas $100k to head up into LEO and service the thing, it would definitely be worth it.

I never said it wouldn't be useful, only that it isn't likely to happen. Amortized costs would reflect that. So it seems we agree?

> If you could pay a few space sherpas $100k to head up into LEO and service the thing, it would definitely be worth it.

Would it? Whatever you pay to launch the repair tech plus the replacement parts could instead be spent launching new hardware. Obviously the repair payload is a fraction of the total weight of new hardware but is it a small enough fraction to make repairing things worthwhile? I think it's likely that disposable is cheaper in this scenario.

What advantage does a mountaintop have versus a more accessible earth-based location?

I suspect one of the motivations for space datacenters is to try to stay out of the reach of all jurisdictions so you Musk can start to run his companies as an autonomous state.

If the goal is to avoid various national jurisdictions, what about floating a barge out into international waters? Do it near the equator in the middle of the pacific to maximize the difficulty of humans getting there. Use the money saved by not needing to launch into orbit to purchase massive gun turrets to prevent piracy.

A submarine comes by, says hi by torpedo, bye. Woe!

blub °Oo.

Yes because when your infrastructure is Earth based, your staff is Earth based and your customers are Earth based, your company's legal registration and owner are Earth based, it would be absolutely impossible for a government to enforce any type of jurisdictional control if your datacenters were in space.

And absolutely no one, anywhere, ever, has the capability to damage or destroy a satellite...

Absolutely no one, anywhere, ever, has the capability to damage or destroy many hundreds of satellites (assuming that SpaceX wouldn't be a willing launch partner).

> (assuming that SpaceX wouldn't be a willing launch partner)

really think about that statement when discussing deliberately avoiding government jurisdiction...

(perhaps also consider that it is not the case that no one can damage a lot of satellites in orbit, but that up until recently no one has had any incentive to build the number of interceptors you would need to do it. But how viable is a space-based datacenter business if you decide to try and pretend you're untouchable, and one of the _many_ governments which operates anti-satellite weapons simply shoots one of your satellites? The debris field from ASAT weapons tests has been of considerable concern everytime they've been used - and given the proximity of useful orbital slots for such a service, the number of intercepts required to render a constellation completely inoperable is going to be _far less_ then the number of satellites).

(in the vein of motivation too: it is well within the power of most well-funded governments to build laser systems would would degrade or destroy orbital satellites, but again, no one has had considerable motivation to do so till recently)

(and of course all of this is - again - competing against the simpler option of simply arresting the people on Earth, or interdicting their ground stations)

Lots of words. Can’t honestly say I read them all. Meanwhile Russia had a pretty strong motivation to destroy Starlink. Motivations don’t get much stronger than that.

As I understand it the idea is to have many of such sats. Literally clouds of them.

Not necessarily in orbits which are easily reachable for current ASATs, nor 'economical'.

For now...

China already has a ground based laser array for military purposes (blinding more or less permanently spy satellites). Some think it could be upgraded to hard killing satellites, which I don't think is yet possible (the amount of energy to burn a sat is also enough to ionise air and thus waste and disperse the laser's energy), but with something heavily constrained by heat dissipation like an orbital datacenter, that last array could overload it and fry it...

> the amount of energy to burn a sat is also enough to ionise air and thus waste and disperse the laser's energy

Why would you use a single beam? Place them far enough apart that they don't begin to converge until the atmosphere has thinned out.

Instead of one large floating barge, make it a thousand smaller floating barges connected with Starlink. Monitor vessel activity near them and autonomously move the fleet to make intercepting them as difficult as possible. Rig them to explode upon capture to deter theft.

(Hint to the downvoters: I'm not being serious.)

I think we can't rule out the explanation that all the ideas of space data centers could be connected to a desire by some of finding additional applications for rockets that can transport stuff to space.

I think we can't rule out the explanation that all the ideas of space data centers could have been connected solely to a desire to pump SpaceX's IPO.

It also provides a post hoc rationale for rolling Elon's loss making businesses into SpaceX. The bull case for ODCs looks a lot like the bull case for space based solar power that Musk once called "the stupidest thing ever"...

That said, SpaceX aren't the only entity proposing ODCs, they're just the only ones promising they're going to make country-sized profits out of them...

What would be accomplished by doing this vs placing them basically anywhere else on earth?

It is a comment on the absurdity of orbital data centers. Mountaintop data centers sound absurd, but are more feasible and efficient than orbital ones in nearly every aspect.

That's fine, if the argument for DC in space is just "Let's put them in the hardest place possible". Then less hard -> absurd, implies more harder -> more absurder.

But space based dc accomplish something that mountaintop dc do not. The different list of benefits/tradeoffs are why space DC are proposed and mountaintop ones are not. It's a difference of kind, not degree. It's not a meaningful experiment to just try to build DC in hard places and then we can finally validate space.

Stated benefits in particular:

- Power available 24/7 for "free"

- coms w/o interruption using existing infra

- Rideshare (SPX can build out capacity while other lifts pay some of the bill for lift)

- Nonregulation

- Very low latency to "places of interest far from USA mountains"

And no, I do not believe that mountaintop automatically satisfies these benefits in a smooth way such that mountaintop is a meaningful stepping stone towards space.

> - Power available 24/7 for "free"

The Sun is visible from Earth as well, the last time I checked.

In LEO you don't get power 24/7 because you are only 500km above the Earth. Yes the Sun is more attenuated on Earth but what we care about is $/W not raw wattage, and Earth certainly has cheaper $/W than space.

> - coms w/o interruption using existing infra

I'm perplexed how comms might be easier in space than on Earth where you can just run a cable.

> - Rideshare (SPX can build out capacity while other lifts pay some of the bill for lift)

On Earth you don't need to rideshare because you don't have to ride a rocket.

> - Nonregulation

Space is more regulated than Earth. The only way to get to space is via a rocket which is the same as an ICBM. Governments regulate the process of building ICBMs and what payloads can ride on them.

If you want non-regulation then go to international waters or find a bribable government.

> - Very low latency to "places of interest far from USA mountains"

The latency is not terrible in LEO but it's nowhere near as good as on Earth.

We're losing the direct chain of thought here. My assertion is that "Nonexistence of Mountaintop DC is not a counter-example to space DC". That's it. The reasons were spelled out.

Your points: "Mountaintop" is how comms is easier in space vs on earth. Starlink already serves many rural areas simply b/c it is easier to go to/from space in some places than "running a cable". "Latency is nowhere near as good as on earth" is just false. "Mountaintop" is why. But more broadly, my most recent vacation cabin has higher latency than starlink offers. Case closed I guess?

And one more on latency: I was referring to latency in areas of interest far from USA mountaintops / USA in general. You might want to peruse the DARPA programs on low latency in-situ, closed loop comms for in theater (sometimes space based) compute. Something close to the action.

Power: "Mountaintop" is how space has a better power case than earth. Not all of earth. Mountaintop earth. top level comment was talking about a wind turbine on a mountaintop. That's an attempt at 24h power which is very likely strictly worse.

You can step back and make larger arguments, but this thread is narrower.

"Space is more regulated than Earth". Yes, again, you're talking about wider counts of regulation. Just go look around at the pushback to data centers and you'll see some of the case for DC in space. The path to getting equipment into space is clean - just get permits and launch same as SPX does for starlink. The path to building a data center on a mountaintop probably encounters at least some non-paperwork pushback that's likely to trip big political fights. That's it. Are there a lot of mountaintops that are sufficiently cold to warrant "cooling" arguments that are not part of large state/federal parks?

So going back to the thread - if you believe that a mountaintop datacenter is a counter example to the feasibility of a space-based data center, then I think you're making a category error on some of the above criteria. Your comments don't dissuade me at all about that because they don't address either side of that argument.

Cooling is not the crux of the real problem, it's the fact that we have no way to replace single failed units in a running space-based data center without another launch - and if youre stressing your total launch cadence with 'new' datacenters, at what % do you repair or replace the whole slab.

The launch tempo, following the invention of a functioning approach to in-space single node replacement for even a modest portion of the planned workload capacity is something that strains credulity, even at the normal earth-level maintenance rate.

Addressing the increased failure rates due to the hard rads and geomagnetic effects, while demanding that orbital systems remain above nm% load - that's n% of the hardware still operating - at 100% power and thermal, or 100% of hardware at m% of power and thermal, or the intersection of those two slopes at any given time - in order to meet shareholders profit expectations pushes that launch cadence and cost - to maintain the baseline of workload... and well, the math of that for even a minimal % of earthbound current deployed demand is just staggeringly many launches per year.

Maybe i'm missing something, but bigger vehicles for putting larger payloads doesnt make it better, it makes it worse.

https://en.wikipedia.org/wiki/A_Modest_Proposal

A better idea is to put them on Mars, so people actually think before they send a stupid question.

I'm thinking if we send them out to catch the Voyager probe up, people might have time to write stuff themselves before they ask the computer to do it for them :)

(I know this is a joke, but it made me think): I wonder what side effects having GW-level heat generation would have on the surrounding area. snowcapped mountains turn to rivers? Spring year round? Something else?

You just need to go north. Most of Finland requires massive amounts of heating for most of the year for industrial and residential purposes. If the math doesn’t add up there, I really can’t see how math for orbital data centers would add up.

Only stating the solar panel - radiator area ratio and not mentioning the actual area that a data center should have, is a sin of omission - and a great one. Also, hand-waving numerous engineering problems just by saying “we’ve solve harder problems before / you can come up with a few designs” is the last thing I want to see in anything that comes up in Hacker News.

What I don't understand about building a space data center is that you need radiators to release heat. Otherwise, it will become a space thermos. What's even more incomprehensible is that you would need specialized equipment for space radiation, and GPUs are consumables. To make that profitable, you would need pricing that is many times higher than the cost of a regular data center. I don't understand why there are people who actually fall for this. If I say this, people will call me someone who mocks others' challenges, but it seems like they're saying physical problems can be overcome too easily.

I have the feeling that the only reason that might actually be done is to escape from any kind of jurisdiction. In space no one can hear you compute.

If that's the case, wouldn't it be better to just put it in the desert? Realistically, if noise from calculations is the problem, placing it in a remote area would be more economical.

The desert is still under someone’s jurisdiction. Perhaps the best on-planet comparison is creating a man made island in the middle of the ocean.

This also seems more sensible than space, although I guess if you’re in international waters then no military will protect you and someone could eventually destroy it. Way more organizations have the ability to blow up a boat is compared to a space station.

It's a play on "in space no-one can hear you scream", not a literal "compute is so noisy we need to go to space"

The jurisdiction issue is the bigger one. Deserts don't solve this; International waters, possibly do, but then you've got other issues.

Is that so? How embarrassing. I'm not a native English speaker, so I didn't understand the metaphor.

The Outer Space Treaty [1] says "A State Party to the Treaty on whose registry an object launched into outer space is carried shall retain jurisdiction and control over such object", so no escaping jurisdiction.

[1] https://en.wikipedia.org/wiki/Outer_Space_Treaty, https://en.wikisource.org/wiki/Outer_Space_Treaty_of_1967#Ar...

Resurrect https://en.wikipedia.org/wiki/Sea_Dragon_(rocket) , launch it 'anonymously' from international waters?

It doesn't say anything about launch location, and you'd need to ship it out there from a country using a large (registered) boat. That loophole won't work.

Staying with exploiting loopholes, that happens all the time with ships, while at sea, in international waters.

I think I've read something about similar things happening with new airliners for fiscal reasons.

OFC that doesn't really erase the track, but one could engage in rented or owned 'lawfare' by then?

It is worth noting that this is also identical to the way in which international waters works as well, so there's plenty of legal precedent.

But it's also irrelevant: all your infrastructure supporting such a thing, including your ability to fund it, is on Earth, in someone's jurisdiction.

The US government is hardly going to say "well the datacenter is in space, guess there's nothing we can do about the owner who lives in California..."

You don't get that with the current plans which require them to have FCC licences and be constantly replacing them by launching from the United States though...

I still don’t see what the advantage is. Of course it’s physically possible to build a datacenter in space, but I can’t imagine land prices being that high that the same data center on earth wouldn’t be cheaper. Even just due to launch costs and the more sophisticated equipment needed for space.

The real issue is that the power situation in LEO is still actually terrible! Your solar is a little more performant, but you're plunged into hard shade every 45 minutes.

I think calling solar a little more performant is underselling it. Once you have LEO getting to a better orbit costs relatively little. Getting from LEO to the moon is only like 30% more than getting from ground to LEO.

True, but lifting the fuel to power that “small” orbital boost is unintuitively expensive

(Refer to the tyranny of the “Rocket Equation”)

There exist the so-called Sun-synchronous orbits, which exploit the precession effect caused by the fact that the Earth is not a sphere, to pass over the same point of the Earth at the same local hour. On a small subset of these Sun-synchronous orbits the Sun is always visible from the satellite (i.e. on the subset of orbits whose plane is approximately perpendicular on the radius that connects the Sun to the Earth). Without the precession effect, a satellite that sees the Sun for an entire day would lose this property after a few days, because of the rotation of the Earth around the Sun, which alters the direction in space of the radius from the Sun to the Earth.

However, the number of slots that are available in Sun-synchronous orbits with permanent view of the Sun is limited, and many potential users want them. So those who desire to build datacenters would have to compete for such orbital slots. There are much less such slots than for geosynchronous orbits. Other countries would certainly be outraged if USA occupied all the available slots with datacenters.

Improved control of the satellites for collision avoidance could allow smaller slots, but maneuvering heavy datacenters would require a lot of fuel, so they might require periodic refueling, greatly increasing the costs.

They are mostly planning sun synchronous orbits afaik. That means the orbit is tilted so the earth’s deformed shape continually moves the orbital plane so the satellite is always in the sun (or generally the plane has the same angle to the sun).

Sure: which is a higher and less accessible orbit. The relative fuel cost might be small, but in absolute terms the ship carrying payload is carrying a lot more to do it - see the number of Starships to refuel a Starship in LEO.

And here's the thing: all of this is competing with solar+batteries cost on Earth. The power situation is the only advantage here.

Like why not put a datacenter on a barge and run an HVDC line out to it far offshore? That would be expensive...but more expensive then space? It's not even outside of the capability set of SpaceX, who already run drone ships to facilitate Falcon 9 landings.

> Sure: which is a higher and less accessible orbit. The relative fuel cost might be small, but in absolute terms the ship carrying payload is carrying a lot more to do it - see the number of Starships to refuel a Starship in LEO.

No it’s not, it’s not either SSO or LEO. You can have SSO at 600km which is lower than the normal LEO satellite.

I agree that it doesn’t make a lot of sense (look at the root comment of this thread), but you absolutely can make a LEO datacenter with 100% sun coverage if you want to.

I doubt it'll make sense any time soon, but some arguments I can think of are that solar in space can easily be ~50% more efficient at any moment while also being continuous (enough) in the right orbit.

An even more radical idea is to put nuclear in space which would sidestep all the earthly hurdles (beyond the launch).

Right, but even if you get 100% solar time in orbit and maybe 20% on the ground, I still don’t see it. Just from a procurement cost and maintenance standpoint. I think spreading a few datacenters around the world to have quasi continuous availability is easier than launching them on satellites.

> An even more radical idea is to put nuclear in space which would sidestep all the earthly hurdles (beyond the launch).

That makes even less sense to me. Why would you launch then and not just stay on the ground? Do you think a country would allow you to launch a rocket with a nuclear reactor from their land but the reactor is so unsafe that you’re not allowed to operate it on the ground?

Then I would just say put it on a boat and park it in international waters, that’s surely cheaper than orbit, right?

Nuclear is used in space, but my understanding is that it is too low power and not really scalable to computing needs for this use case. Bonus side really is that nuclear power can provide power for very long time.

Until now only energy sources based on radioactive decay have been used in space, which have very low power, but they can provide it for many decades.

Nuclear fission reactors, similar to those used on submarines or ships, would enable very different applications.

Until now, they have not been used for fear of what would happen after a failed rocket launch, when the reactor would fall back on Earth.

This could be mitigated by sending only components of the reactor and assembling it in space.

I do not think that routine exploration of the Solar System beyond Mars will ever be possible without using at least nuclear fission reactors, because it is too slow with chemical sources of energy.

Actually in the Cold War there were some actual nuclear reactors in space:

https://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor#TOPAZ-I

> This could be mitigated by sending only components of the reactor and assembling it in space.

How would that help? The main problem if the launch fails is that the radioactive material will spread around (in the worst case, they are encased so exactly that doesn’t happen).

You could maybe spread out the nuclear material in multiple launches but you would just increase the risk of a small contamination in exchange for a smaller risk of a large contamination.

I don’t think the individual parts of the reactor are intrinsically safer than the reactor, it’s not like it’s going to become an atomic explosion during launch.

One advantage that does come to mind in light of the Iran war (and the loss of an AWS DC) is difficulty in attacking it, even when it’s directly above foreign territory. I wonder if one of the intended customers will be gov/military? Conjoined spy satellite/DC for some function maybe?

I don’t know what the end game of the US looks like but surely you’ll always find some territory around the world to relatively safely put datacenters? And if your opponent isn’t Iran but something like russia or china, they’ll just blow up your datacenter in orbit, too.

I see the point to maybe do some onboard data processing on spy satellites etc, but on the other hand, downlink bandwidth seems to be become less of an issue over time, so it doesn’t seem that important to me compared to just sending down the raw data over star link or the military equivalent.

Whyyyy are we not building distributed data centers under driveways? I want one under my driveway to melt the snow. It can use my power and water hookups if it pays for them.

Aren't some bitcoin farms used for heating in some places, like agriculture in greenhouses?

There was also this[1] analysis in late 2025 from a former NASA engineer that looked at the impracticability.

[1] https://taranis.ie/datacenters-in-space-are-a-terrible-horri...

The make the whole calculation more detailed, e.g. include the orbit, there are specialized programs.

The one ESA used to use is called

ESATAN

I used to share office with a colleague who mostly worked with it. This was at a time when the fad of naming products with an initial "e" had just faded. The surviving victim is "ebay" I guess, but at a time there were many like it.

So my natural reading of the huge ASCII art rending on ESATAN's title screen has always been E-SATAN. Sorry ESA.

Joking aside, you can download ESATAN here:

https://www.esatan-tms.com

It's not obvious what the download allows but expect restrictions. I remember the version we used had a HW dongle with heavy price tag every month.

This isn't terribly practical. Yes, we can deal with heat. The trouble is cost, and dealing with high energy radiation both flipping bits and corrupting the silicon.

Seems reasonable that the area needed would be less than the solar panels. Since it sould be more efficient to dump heat than collect energy from light.

It seems to me that there’s a lot of math in the middle of this that just doesn’t matter that much: every photon hitting every part of the array is going to add energy. Whatever percent we transform into data doesn’t matter — all the energy from all those photons minus energy used for station keeping needs to be radiated away. I guess if some is used for station keeping so much the better.

I was hoping to read about what exactly these ‘heat pump radiators’ look like, but I guess ultimately they’re going to be lasers or flashlights or some such thing.

A relativity course question I recall from my youth asked how long an astronaut stranded 1km from a ship would need to point the flashlight away to return to the ship based on the mass of the photons leaving the light — spoiler - this can work in time to save an astronaut’s life — double spoiler: if you’re really accurate, it’s better to throw the flashlight if you’re in a hurry.

As I write this I realize my physics model is super weak, because I’m not sure what percent of the energy used to make a photon turns into the photon’s mass (and therefore is pushing against the laser), and what is in light and therefore just, you know, carries on for billions of years until it hits something else.

I think it's a vary valid option to launch swarms of datacenters into space. I think a few decades to a hundred years from now, it will be the norm. Until then, we can find plany of land to do it. Instead a launch, you just need a battery. Much cheaper. All the rest stays the same.

Don't we also have to worry about heating of the solar panels themselves? 150W/m^2 isn't the incident power, it's the output power. Incident is something like ten times that. Some of that's going to be reflected, but not all of it.

If I had a dollar for everytime someone told me they have an advanced physics degree and can unequivocally gaurantee me that it will never be physically feasible to cool GPU's in space.... How soon those people have disappeared!

Advanced physics degree holders are right, the linked article is full of mistakes.

You can bullshit humans but you can't bullshit reality.

This article made me think of a strange claim by Elon Musk at 07:08 in this [1] interview:

"Cooling is actually much easier in space than it is on earth. You can just radiate to the vacuum."

I don't think that follows. The radiator is only the final heat sink. You still need to move heat from very dense chips into a deployable, space-rated radiator, and handle pumps, loops, leaks, redundancy, radiation damage, replacement, eclipses, Earth IR/albedo, and launch mass.

[1] https://youtu.be/D_1j5dVWNYI?si=R77VeVKlRXRhaBk5&t=428

Radiators in space are a solved problem. The ISS has 70 kW of cooling via multiple radiators, using a dual loop water/ammonia system. The water loop cools the station and high-priority electronics, then the ammonia loop cools the water loop and transfers heat to the radiators, which release the heat out to space. There are additional radiators just for the solar panels.

AI sat mini can use a simpler single ammonia loop, since the ISS uses a water loop on the station side to avoid toxicity issues in case of a coolant leak.

It's a far simpler engineering problem to solve compared to other challenges SpaceX is facing (Starship, Raptor, Starlink).

Sorry, should have emphasized that it was the "much easier" part I didn't agree with in that interview.

See also https://andrewmccalip.com/space-datacenters with some models and numbers you can play with.