Comment by beloch
1 day ago
I would not assume cooling has been worked out.
Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot. A satellite is, if nothing else, a fantastic thermos. A data center in space would necessarily rely completely on cooling by radiation, unlike a terrestrial data center that can make use of convection and conduction. You can't just pipe heat out into the atmosphere or build a heat exchanger. You can't exchange heat with vacuum. You can only radiate heat into it.
Heat is going to limit the compute that can be done in a satellite data centre and radiative cooling solutions are going to massively increase weight. It makes far more sense to build data centers in the arctic.
Musk is up to something here. This could be another hyperloop (i.e. A distracting promise meant to sabotage competition). It could be a legal dodge. It could be a power grab. What it will not be is a useful source of computing power. Anyone who takes this venture seriously is probably going to be burned.
It's exiting the 5th best social network and the 10th (or worse) best AI company and selling them to a decent company.
It probably increases Elon's share of the combined entity.
It delivers on a promise to investors that he will make money for them, even as the underlying businesses are lousy.
I'm confused about the level of conversation here. Can we actually run the math on heat dissipation and feasibility?
A Starlink satellite uses about 5K Watts of solar power. It needs to dissipate around that amount (+ the sun power on it) just to operate. There are around 10K starlink satellites already in orbit, which means that the Starlink constellation is already effectively equivalent to a 50 Mega-watt (in a rough, back of the envelope feasibility way).
Isn't 50MW already by itself equivalent to the energy consumption of a typical hyperscaler cloud?
Why is starlink possible and other computations are not? Starlink is also already financially viable. Wouldn't it also become significantly cheaper as we improve our orbital launch vehicles?
Output from radiating heat scales with area it can dissipate from. Lots of small satellites have a much higher ratio than fewer larger satellites. Cooling 10k separate objects is orders of magnitude easier than 10 objects at 1000x the power use, even if the total power output is the same.
Distributing useful work over so many small objects is a very hard problem, and not even shown to be possible at useful scales for many of the things AI datacenters are doing today. And that's with direct cables - using wireless communication means even less bandwidth between nodes, more noise as the number of nodes grows, and significantly higher power use and complexity for the communication in the first place.
Building data centres in the middle of the sahara desert is still much better in pretty much every metric than in space, be it price, performance, maintainance, efficiency, ease of cooling, pollution/"trash" disposal etc. Even things like communication network connectivity would be easier, as at the amounts of money this constellation mesh would cost you could lay new fibre optic cables to build an entire new global network to anywhere on earth and have new trunk connections to every major hub.
There are advantages to being in space - normally around increased visibility for wireless signals, allowing great distances to be covered at (relatively) low bandwidth. But that comes at an extreme cost. Paying that cost for a use case that simply doesn't get much advantages from those benefits is nonsense.
19 replies →
Simply put no, 50MW is not the typical hyperscaler cloud size. It's not even the typical single datacenter size.
A single AI rack consumes 60kW, and there is apparently a single DC that alone consumes 650MW.
When Microsoft puts in a DC, the machines are done in units of a "stamp", ie a couple racks together. These aren't scaled by dollar or sqft, but by the MW.
And on top of that... That's a bunch of satellites not even trying to crunch data at top speed. No where near the right order of magnitude.
96 replies →
It's like this. Everything about operating a datacenter in space is more difficult than it is to operate one on earth.
1. The capital costs are higher, you have to expend tons of energy to put it into orbit
2. The maintenance costs are higher because the lifetime of satellites is pretty low
3. Refurbishment is next to impossible
4. Networking is harder, either you are ok with a relatively small datacenter or you have to deal with radio or laser links between satellites
For starlink this isn't as important. Starlink provides something that can't really be provided any other way, but even so just the US uses 176 terawatt-hours of power for data centers so starlink is 1/400th of that assuming your estimate is accurate (and I'm not sure it is, does it account for the night cycle?)
126 replies →
Amazon’s new campus in Indiana is expected to use 2.2GW when complete. 50Mw is nothing, and that’s ignoring the fact that most of that power wouldn't actually be used for compute.
> A Starlink satellite uses about 5K Watts of solar power. It needs to dissipate around that amount (+ the sun power on it) just to operate.
The “+ solar power” part is the majority of the energy. Solar panel efficiency is only about 25-30% at beginning-of-life whereas typical albedos are effectively 100%. So your estimate is off by at least a factor of three.
Also, I’m not sure where you got 5 kw from. The area of the satellite is ~100 m2, which means they are intercepting over 100 kw of bolometric solar power.
Starlink provides a service that couldn't exist without the satellite infrastructure.
Datacenters already exist. Putting datacenters in space does not offer any new capabilities.
2 replies →
> Isn't 50MW already by itself equivalent to the energy consumption of a typical hyperscaler cloud?
xAI’s first data center buildout was in the 300MW range and their second is in the Gigawatt range. There are planned buildouts from other companies even bigger than that.
So data center buildouts in the AI era need 1-2 orders of magnitude more power and cooling than your 50MW estimate.
Even a single NVL72 rack, just one rack, needs 120kW.
5kW means you can't even handle a single one of these[0], compared to a handful per rack on an earthbound data centre.
0. https://www.arccompute.io/solutions/hardware/gpu-servers/sup...
I ran the math the last time this topic camps up
The short answer is that ~100m2 of steel plate at 1400C (just below its melting point) will shed 50MW of power in black body radiation.
https://news.ycombinator.com/item?id=46087616#46093316
5 replies →
Starlink satellites also radiate a non-trivial amount of the energy they consume from their phased arrays
Not related to heat, but a com satellite is built from extremely durable HW/SW that's been battle-tested to run flawlessly over years with massive MTBF numbers.
A data center is nowhere near that and requires constant physical interventions. How do they suggest to address this?
50MW is on the small side for an AI cluster - probably less than 50k gpus.
if the current satellite model dissipates 5kW, you can't just add a GPU (+1kW). maybe removing most of the downlink stuff lets you put in 2 GPUs? so if you had 10k of these, you'd have a pretty high-latency cluster of 20k GPUs.
I'm not saying I'd turn down free access to it, but it's also very cracked. you know, sort of Howard Hughesy.
1 reply →
50MW might be one aisle of a really dense DC. A single rack might draw 120kW.
Are starlink satellites in sun synchronous orbits? Doesn't constant solar heating change the energy balance quite a bit?
A Starlink satellite is mainly just receiving and sending data, the bare minimum of a data center-satellite's abilities; everything else comes on top and would be the real power drain.
Forget heat. Replacing disks alone is a deal breaker on that one.
> A Starlink satellite uses about 5K Watts of solar power. It needs to dissipate around that amount (+ the sun power on it) just to operate.
This isn't quite true. It's very possible that the majority of that power is going into the antennas/lasers which technically means that the energy is being dissipated, but it never became heat in the first place. Also, 5KW solar power likely only means ~3kw of actual electrical consumption (you will over-provision a bit both for when you're behind the earth and also just for safety margin).
> A Starlink satellite uses about 5K Watts of solar power
Is that 5kW of electrical power input at the terminals, or 5kW irradiation onto the panels?
Because that sounds like kind of a lot, for something the size of a fridge.
Because 10K satellites have a FAR greater combined surface area than a single space-borne DC would. Stefan-Boltzman law: ability to radiate heat increase to the 4th power of surface area.
3 replies →
Square–cube law.
Why would anyone think the unit cost would be competitive with cheap power / land on earth? If that doesn't make sense how could anything else?
A typical desktop/tower PC will consume 400 watts. So 12 PC's equals 1 starlink satellite.
A single server in a data center will consume 5-10 kW.
> Why is starlink possible and other computations are not?
Aside from the point others have made that 50 MW is small in the context of hyperscalers, if you want to do things like SOTA LLM training, you can't feasibly do it with large numbers of small devices.
Density is key because of latency - you need the nodes to be in close physical proximity to communicate with each other at very high speeds.
For training an LLM, you're ideally going to want individual satellites with power delivery on the order of at least about 20 MW, and that's just for training previous-generation SOTA models. That's nearly 5,000 times more power than a single current Starlink satellite, and nearly 300 times that of the ISS.
You'd need radiator areas in the range of tens of thousands of square meters to handle that. Is it theoretically technically possible? Sure. But it's a long-term project, the kind of thing that Musk will say takes "5 years" that will actually take many decades. And making it economically viable is another story - the OP article points out other issues with that, such as handling hardware upgrades. Starlink's current model relies on many cheap satellites - the equation changes when each one is going to be very, very expensive, large, and difficult to deploy.
Sure, we can run the math on heat dissipation. The law of Stefan-Boltzman is free and open source and it application is high school level physics. You talk about 50 MW. You are going to need a lot of surface area to radiate that off at somewhere close to reasonable temperatures.
1 reply →
> 10th (or worse) best AI company
You might only care about coding models, but text is dominating the market share right now and Grok is the #2 model for that in arena rankings.
Arena rankings, lol.
Openrouter is a decent proxy for real world use and Grok is currently 8% of the market: https://openrouter.ai/rankings (and is less than 7% of TypeScript programming)
2 replies →
Grok is losing pretty spectacularly on the user / subscriber side of things.
They have no path to paying for their existence unless they drastically increase usage. There aren't going to be very many big winners in this segment and xAI's expenses are really really big.
12 replies →
Plus government backstop. The federal government (especially the current one) is not going to let SpaceX fail.
Maybe not, but they might force it to sell at fire sale prices to another aerospace company that doesn't have the baggage.
xAI includes twitter? I thought twitter was just X?
xAI acquired twitter in 2025 as part of Musk's financial shell game (probably the same game he is playing with SpaceX/xAI now).
Elon's always looking for another Brooklyn Bridge to sell to the rubes...
Sounds like Elon hurt someone’s feelings
In 2024, Starcloud posted their plans to "solve" the cooling problem. https://starcloudinc.github.io/wp.pdf
> As conduction and convection to the environment are not available in space, this means the data center will require radiators capable of radiatively dissipating gigawatts of thermal load. To achieve this, Starcloud is developing a lightweight deployable radiator design with a very large area - by far the largest radiators deployed in space - radiating primarily towards deep space...
They claim they can radiate "633.08 W / m^2". At that rate, they're looking at square kilometers of radiators to dissipate gigawatts of thermal load, perhaps hectares of radiators.
They also claim that they can "dramatically increase" heat dissipation with heat pumps.
So, there you have it: "all you have to do" is deploy a few hectares of radiators in space, combined with heat pumps that can dissipate gigawatts of thermal load with no maintenance at all over a lifetime of decades.
This seems like the sort of "not technically impossible" problem that can attract a large amount of VC funding, as VCs buy lottery tickets that the problem can be solved.
Yes, on the face of it, the plan is workable. Heat radiation scales linearly with area and exponentially (IIRC) with temperature.
It really is as simple as just adding kilometers of radiatiors. That is, if you ignore the incredible cost of transporting all that mass to orbit and assembly in space. Because there is quite simply no way to fold up kilometer-scale thermal arrays and launch in a single vehicle. There will be assembly required in space.
All in all, if you ignore all practical reality, yes, you can put a datacenter in space!
Once you engage a single brain cell, it becomes obvious that it is actually so impractical as to be literally impossible.
> Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot.
1) The heat can be transported by a heat carrier conducting heat standing still.
2) The heat can be transported by a heat carrier in motion.
3) The heat can be transported by thermal radiation.
The first 2 require massive particles, the latter are spontaneous photons.
A thermos bottle does not simply work by eliminating the motile mass particles.
Lets consider room temperature as the outer thermos temperature and boiling hot water as the inner temperature, that is roughly 300 K and 400 K.
Thermal radiation is proportional to the fourth power of temperature and proportional to emissivity (which is between 0 and 1).
Lets pretend you are correct and thus thermally blackened glass (emissivity 1) inside the vacuum flask would be fine according to you. That would mean that the radiation from your tea to the room temperature side would be proportional to 400^4 while the thermal radiation from room temperature to the tea would be proportional to 300^4. Since (400/300) ^ 4 = 3.16 that means the heat transport from hot tea to room temperature is about 3 times higher.
If on the other hand the glass was aluminized before being pulled vacuum the heat transports are proportional to 0 * 400 K ^ 4 and 0 * 300 K ^ 4 . So the heat transport in either direction would be 0 and no net heat transport remains.
If you believe the shiny inside of your thermos flask is an aesthetic gimmick, think again.
You are making a non-comparison.
Imagine comparing a diesel engine car to an electric car, but first removing the electric motor. Does that make a fair comparison???
Nobody made any of the claims you're "refuting".
You've imagined an argument so you can dunk on it to appear superior.
In addition, thermoses aren't made of glass. It is far more common to make them out of steel or aluminum.
It has been worked out. Just look at how big are ISS radiators and that they dissipate around 100kW then calculate cost of sending all that to space. And by that I mean it would be even more expensive that some of the estimates flying around
While personally I think it's another AI cash grab and he just wants to find some more customers for spacex, other thing is "you can't copyright infringe in space" so it might be perfect place to load that terabytes of stolen copyrighted material to train data sets, if some country suddenly decides corporation stealing copyright content is not okay any more
DGX H200 is 10,2 kW. So that like 10 of them. Or only 80 H200. Doesn’t sound like a big data center. More like a server room.
ISS radiators are huge 13.6x3.1 m. Each radiates 35 kW. So you need 3 of them to have your 100 kW target. They are also filled with gas that needs pumping so not exactly a passive system and as such can break down for a whole lot of reasons.
You also need to collect that power so you need about the same amount of power coming from solar panels. ISS solar array wings are 35x12 m and can generate about 31 kW of power. So we’ll need at least 3 of them. BTW each weighs a ton, a literal metric ton.
It hardly seems feasible. Huge infrastructure costs for small AI server rooms in space.
if I may add, you can't really launch a station three times the size of ISS with a single rocket so there will be multiple launches. Just the launch costs alone could likely finance multiple similarly sized server rooms on land.
1 reply →
Maybe you can't copyright infringe in space, but it's still infringement when the result gets back to earth.
These major AI tools have already been trained on infringing works.
Keep the result in space, and use large telescopes to look at it!
2 replies →
Its very simple, xAI needs money to win the AI race, so best option is to attach to Elon’s moneybank (spacex) to get cash without dilution
Remember how he argued for Tesla’s Solarcity acquisition because solar roofs?
Data centers in space are the same kind of justification imo.
Solar roofs are much more practical to be honest.
7 replies →
> win the AI race
I keep seeing that term, but if it does not mean "AI arms race" or "AI surveillance race", what does it mean?
Those are the only explanations that I have found, and neither is any race that I would like to see anyone win.
Big tech businesses are convinced that there must be some profitable business model for AI, and are undeterred by the fact that none has yet been found. They want to be the first to get there, raking in that sweet sweet money (even though there's no evidence yet that there is money to be made here). It's industry-wide FOMO, nothing more.
20 replies →
A significant number of AI companies and investors are hoping to build a machine god. This is batshit insane, but I suppose it might be possible. Which wouldn't make it any more sane.
But when they say, "Win the AI race," they mean, "Build the machine god first." Make of this what you will.
2 replies →
It’s a graft to keep people distracted and allow for positioning as we fall off the end of the fossil energy boom.
It’s a framing device to justify the money, the idea being the first company (to what?) will own the market.
Being too far ahead for competitors to catch up, similar to how google won browsers, amazon won distribution, etc
I’m not certain spacex is generating much cash right now ?
Starship development is consuming billions. F9 & Starlink are probably profitable ?
I’d say this is more shifting of the future burden of xAI to one of his companies he knows will be a hit stonk when it goes public, where enthusiasm is unlikely to be dampened by another massive cash drain on the books.
> xAI needs money to win the AI race
Off on a tangent here but I'd love for anyone to seriously explain how they believe the "AI race" is economically winnable in any meaningful way.
Like what is the believed inflection point that changes us from the current situation (where all of the state-of-the-art models are roughly equal if you squint, and the open models are only like one release cycle behind) to one where someone achieves a clear advantage that won't be reproduced by everyone else in the "race" virtually immediately.
I _think_ the idea is that the first one to hit self improving AGI will, in a short period of time, pull _so_ far ahead that competition will quickly die out, no longer having any chance to compete economically.
At the same time, it'd give the country controlling it so much economic, political and military power that it becomes impossible to challenge.
I find that all to be a bit of a stretch, but I think that's roughly what people talking about "the AI race" have in mind.
Like any other mega-scaler, theyre just playing Money Chicken.
Everyone is spending crazy amounts of money in the hopes that the competition will tap out because they can't afford it anymore.
Then they can cool down on their spending and increase prices to a sustainable level because they have an effective monopoly.
1 reply →
> Off on a tangent here but I'd love for anyone to seriously explain how they believe the "AI race" is economically winnable in any meaningful way.
Because the first company to have a full functioning AGI will most likely be the most valuable in the world. So it is worth all the effort to be the first.
1 reply →
They ultimately want to own everyone's business processes, is my guess. You can only jack up the subscription prices on coding models and chatbots by so much, as everyone has already noted... but if OpenAI runs your "smart" CRM and ERP flows, they can really tighten the screws.
2 replies →
That may be the plan, but this is also a great way for GDPR's maximum fine, based on global revenue, to bite on SpaceX's much higher revenue. And without any real room for argument.
The energy economics in space are also a bit more complicated than usually thought. I think Starlink has been using Si cells instead of III-V-based ones, but in addition to lower output they also tend to degrade faster under radiation. I guess that's ok if the GPU is going to be toast in a few years anyway so you might as well de-orbit the whole thing. But that same solar cell on Earth will happily be producing for 40+ years.
Also the same issue with radiative cooling pops up for space solar cells - they tend to run way hotter than on Earth and that lowers their efficiency relative to what you could get terrestrially.
People did the calculation: radiative cooling requires smaller surface area than solar panels. So, basically, a solar panel itself can radiate heat.
Have you done a calculation yourself?
How can the solar panel itself radiate heat when it's being heated up generating supplying power? Looking at pictures of the ISS there's radiators that look like they're there specifically to cool the solar panels.
And even if viable, why would you just not cool using air down on earth? Water is used for cooling because it increases effectiveness significantly, but even a closed loop system with simple dry air heat exchangers is quite a lot more effective than radiative cooling
You take the amount of energy absorbed by the solar panels and subtract the amount they radiate. Most things in physics are linear systems that work like this.
The same radiative (radiant) cooling on Earth works almost just as well, but without the cost of a rocket launch.
(DTC) Datacentres take electricity and turn it into low grade heat e.g 60c water. Put them anywhere where you've either got excess (cheap) energy or where you can use the heat. Either is fine, both is great, but neither is both bad and current standard practice.
It's perfectly possible to put small data centres in city centres and pipe the heat around town, they take up very very little space and if you're consuming the heat, you don't need the noisy cooling towers (Ok maybe a little in summer).
Similarly if you stick your datacentre right next to a big nuclear power plant, nobody is even going to notice let alone care.
Well a few considerations:
- You have to size your cooling towers for your hottest hour. Doing this saves you no capital costs.
- You barely have to run the fans on your cooling towers in the winter because the air is so cold. So often this also won’t save you much operating costs.
- Already there is an essentially unlimited amount of so called “waste heat” from power plants and factories. Building district heating systems is extremely capital intensive, which is why this isn’t done more.
- As a municipality it’s just a horrible idea to make the heating system of your whole city rely on a random company continuing to operate (even worse if said company is in a potential bubble). This is why most district heating systems work with power plants - they already have the government involved in ensuring their continuing operations.
I don't think I ever said it reduced capital cost. I agree (though you might be willing to take more risk on reducing redundancy e.g instead of 2+1 cooling towers you may be more willing to just buy 2).
You cannot put a power station in the middle of a city centre, you can put a datacentre there. The main reason this isn't done more is that it's expensive to build heat network between the 'far out of town industrial area' where they put the heat sources and the city centre where the heat consumers are.
I don't know why a municipality is involved, but regardless you can simply install a backup heat source and/or add a mix of heat suppliers to the network. Backup gas boiler or similar is not that problematic or expensive to add particularly because you don't need to add redundancy as it's just there for a backup scenario.
Resistive heating is a tremendously inefficient way to generate heat. Sometimes it's worth it if you get something useful in exchange (such as full spectrum light in the winter). But it's not all upsides.
Heat pumps are magic. They're something like 300% efficient. Each watt generates 3 watts of useful heat.
I share your enthusiasm about heat pumps, but I wonder what the efficiency of using waste heat is. Couldn't it be competitive with heat pumps? As it's a waste product, isn't it reasonable to also expect it to be more than 100% efficient?
6 replies →
Its not inefficient if you were creating the heat anyway, its a completely free byproduct.
1 reply →
I don’t believe you’ve considered the possibility of a data center on Pluto…
But in all seriousness, if there is a possibility of building industrial centers outside of the Earth’s atmosphere, it is surely not here yet. Lots of areas would need improvement.
> It makes far more sense to build data centers in the arctic.
What (literally) on earth makes you say this? The arctic has excellent cooling and extremely poor sun exposure. Where would the energy come from?
A satellite in sun-synchronous orbit would have approximately 3-5X more energy generation than a terrestrial solar panel in the arctic. Additionally anything terrestrial needs maintenance for e.g. clearing dust and snow off of the panels (a major concern in deserts which would otherwise seem to be ideal locations).
There are so many more considerations that go into terrestrial generation. This is not to deny the criticism of orbital panels, but rather to encourage a real and apolitical engineering discussion.
> A satellite in sun-synchronous orbit would have approximately 3-5X more energy generation than a terrestrial solar panel in the arctic.
Building 3-5x more solar plants in the Arctic, would still be cheaper than travelling to space. And that's ignoring that there are other, more efficient plants possible. Even just building a long powerline around the globe to fetch it from warmer regions would be cheaper.
> Even just building a long powerline around the globe to fetch it from warmer regions would be cheaper.
Deserts have good sun exposure and land availability but extremely poor water resources, which is necessary for washing the sand off the panels. There are many challenges with scaling both terrestrial and orbital solar.
1 reply →
> Building 3-5x more solar plants in the Arctic, would still be cheaper than travelling to space.
Well first you have to make solar panels works in the polar nights, in winter they have a few minutes of sun in the day at most.
Sunlight is unevenly distributed in the arctic during the year to say the least.
I think he has rocket company that needs more work.
Sufficient hype funds more work for his rocket company.
The more work they have the faster they can develop the systems to get to Mars. His pet project.
I really think it's that simple.
Starlink and Falcon 9 have been an excellent pairing, Falcon 9 partially reusable rockets created a lot launch capacity and starlink filled the demand. Starship if it meets its goals will create more launch fully reusable supply by orders of magnitude, but there is not the demand for all that launch capacity. Starlink can take some of it but probably not all so they need to find a customer to fill it in order to build up enough to have the volume to eventually colonize mars.
Going to Mars is not a serious goal.
We can tell because it’s not being treated as a serious goal. 100% of the focus is on the big vroom vroom part that’s really exciting to kids who get particularly excited by things that go vroom, and approximately 0% of the focus is on developing all the less glamorous but equally essential components of a successful Mars mission, like making sure the crew stays healthy.
Correct, and this is meant to attract the same investors and Bulls that already think Mars colonies is a solved problem, just need a few more years to run some tests. As with all, it is only about making himself richer.
Nobody colonizing Mars. Get real. The most likely outcome, is him landing on a cell when the full Epstein files come out.
1 reply →
> colonize mars
Oh, that crap again.
What in particular is wrong/misleading in the Starcloud whitepaper, then?
https://starcloudinc.github.io/wp.pdf
In Table 1, the cost of cooling of a terrestrial data centre is listed as $7M. The cost of cooling in space is assigned a value of $0 with the claim:
"More efficient cooling architecture taking advantage of higher ΔT in space"
My bold claim: The cost of cooling will not be $0. The cost of launching that cooling into space will also not be $0. The cost of maintaining that mechanically complex cooling in space will not be $0.
They then throw in enough unrealistic calculations later in the "paper" to show that they thought about the actual cost at least a little bit. Apparently just enough to conclude that it's so massive there's no way they're going to list it in the table. Table 1 is pure fantasy.
That row specifically says "chiller energy cost" which is 0
Previous discussions on HN: - https://news.ycombinator.com/item?id=43977188
I will not re-read them, but from what I recall from those threads is numbers don't make sense. Something like:
- radiators the multiple square kilometers in size, in space;
- lifting necessary payloads to space is multiples of magnitudes more than we have technology/capacity as the whole world now;
- maintanence nightmare. yeah you can have redundancy, but no feasable way to maintain;
- compare how much effort/energy/maintenance is required to have ISS or Tiangong space stations - these space datacenters sound ridiculous;
NB: I would be happy to be proven wrong. There are many things that are possible if we would invest effort (and money) into it, akin to JFK's "We choose to go to the Moon" talk. Sounded incredible, but it was done from nearly zero to Moon landing in ~7 years. Though as much as I udnerstand - napkin math for such scale of space data centers seem to need efforts that are orders or magnitude more than Apollo mission, i.e. launching Saturn V for years multiple times per day. Even with booster reuse technology this seems literally incredible (not to mention fuel/material costs).
A giant space datacenter with square kilometers of solar panels doesn't make sense. A cluster of Starlink-sized satellites, which orbit near each other(1) and which are connected using laser-links might make sense.
(1) There are orbital arrangements that allow satellites to stay close together with minimal orbital corrections. Scott Manley mentioned this in one of his videos.
1 reply →
They do not at any point outline how cooling will be done, they simply say "it will be more efficient than chillers due to the larger delta T" which is incorrect because it's about dT not delta T
Probably this bit on page 4, which parent comment addresses: “More efficient cooling architecture taking advantage of higher ΔT in space.”
It’s funny how quickly the general public forgot about the “vacuum thermos”. (Perhaps more popular before StarBucks overran society).
Those flasks don’t have any space age insulating material - mainly just a vacuum…
Technology from 1892…
They are more popular than ever, actually. Pretty much all those fancy cups and bottles (like Stanley, other brands available) sold to keep your coffee hot/drink cold on the go are vaccum ones. It's just updated and more robust design compared to the older thermos flasks.
> It could be a legal dodge. It could be a power grab. What it will not be is a useful source of computing power
It's a way to get cheap capital to get cool tech. (Personal opinion.)
Like dark fibre in the 1990s, there will absolutely–someday–be a need for liquid-droplet radiators [1]. Nobody is funding it today. But if you stick a GPU on one end, maybe they will let you build a space station.
[1] https://en.wikipedia.org/wiki/Liquid_droplet_radiator
You can reject the heat by shedding hot mass, but only once.
Cooling by mass effect style yeeting hot chunks of metal out the back.
Where will they go, nobody knows!
Depending on where they land, you can double the service you offer. AI computations coupled with rods from God.
When the radiation burns out a GPU, just dump as much heat into it as possible and yeet it into the atmosphere. Ez.
2 replies →
"A satellite is, if nothing else, a fantastic thermos."
A satellite is quite unlike a thermos in the sense that it is carefully tuned to keep its temperature within a relatively narrow band around room temperature.[1] during all operational phases.
This is because, despite intended space usage, devices and parts are usually tested and qualified for temperature limits around room temperature.
[1] "Room temperature" is actually a technical term meaning 20°C (exceptions in some fields and industries confirm the rule).
> 1] "Room temperature" is actually a technical term meaning 20°C (exceptions in some fields and industries confirm the rule).
Yes 20 and 25°C I believe are the two most popular choices. In many cases it makes little difference with units in Kelvin ¯\_(ツ)_/¯
I have reached the same conclusion -- this is perhaps not a distraction but an attempt to gather funds to pursue the One True Goal...
Exactly - satellites need to be cooled to prevent overheating that wouldn’t happen on earth.
(Space doesn’t help in cooling GPUs in a satellite - space makes cooling worse)
I think it's possibly more informative to look at what happened with SolarCity and Tesla and contemplate if there's not a similar dynamic here.
As an engineer of the software variety, logically heat dissipation would seem like a difficult problem.
But SpaceX has lots of real engineers who are very smart. I’m certain they ran the math on it. Which is more than you or I have done.
If they say it can be done, I’m inclined to believe them.
Wow. Definitely not a textbook fallacy.
I mean why think about anything, you know. Critical thinking is for losers, am I right?
I think it's more an appeal to (expert) authority
"But even if we stipulate that radiation, cooling, latency, and launch costs are all solved, other fundamental issues still make orbital data centers, at least as SpaceX understands them, a complete fantasy. "
I'm pretty his point is that while cooling is an impossibility, it is not the only one!
I used to really enjoy musk's talks when he was spooling up tesla. He was an engineer and obviously the world is missing what engineers see clearly.
But now looking back and accounting for the claims he made there's a pattern.
I saw this article:
https://www.wired.com/story/theres-a-very-simple-pattern-to-...
that said... he did jumpstart the EV industry. He has put up satellites every week for years. He is still a net benefit to all of us.
> he did jumpstart the EV industry.
This is widely believed (especially in the US, where, other than the Leaf, most early electric cars never launched), but honestly pretty dubious. The first real electric cars, with significant production:
2010 - Mitsubishi i-MiEV, Nissan Leaf
2011 - Smart electric, Volvo C30 electric, Ford Focus electric, BYD e6.
2012 - Renault Zoe (Renault launched a couple of other vehicles on the same platform ~2010, but they never saw significant production), Tesla Model S (Tesla had a prior car, the Roadster, but it never saw significant production).
2013 - VW eUP, eGolf (VW occasionally put out an electric Golf historically, going back to 1992, but again those were never produced in large quantities).
The big change ~2010 was around the economics of lithium ion batteries; they finally got cheap enough that everyone started pulling their concept designs and small-scale demonstration models into full production.
> he did jumpstart the EV industry. He has put up satellites every week for years. He is still a net benefit to all of us.
Talk to any former SpaceX or Tesla employee. They will clue you in that both were successful in spite of Elon, not because of him.
The Cybertruck was really the first product he saw to completion from his own design. And well...
I think you under appreciate him a bit here. No he's not a super genius. He's probably not even a good engineer. But he is a) a total a.hole and b) a tremendous bullshitter. There are circumstances in which you need such a person to succeed (see also Steve Jobs). He yelled at people for 10 years straight and he was crucial in facilitating capital to build these very capital intensive products. A regular smart person would absolutely not have succeeded, for these reasons.
5 replies →
He's got a trillion dollar compensation package on the line. You can absolutely guarantee he's doing something shady.
It links his middling AI company and his failing social media company with the only company that can send the United States to space.
X failing and can't pay its debts? Welp, better give him a government bailout otherwise no more rockets for you!
This exactly. His other companies are failing. He links the shitty companies with the only one working.
The 4-5nm gpu will break from high energy protons from the sun.
Lag for roundtrip: 35ms. But when satelite needs to pass through other satellites as has no ground coverage you add more lag and reduce bandwidth of the whole network.
The best part is jurisdiction safety. Very hard to get raided by govs.
AI sovereignty, not AI efficiency. Redesign AI chips with lower power density and higher thermal tolerances and you get more efficient radiation with some sacrifice in compute power. But you are outside the jurisdiction of every country.
Then you get people paying much more money to use less-tightly-moderated space-based AI rather than heavily moderated AI.
The only way I see this actually working given the resource requirement is delta-v style with in orbit resource extraction using robots. By transferring heat to asteroids in the shade of the solar panels at L1 or something.
https://share.google/uXWQyAp7a8nE03qoi
Can’t you heat exchange inside the satellite, and make one part of the satellite incredibly hot so that it radiates a lot and dissipates.
This is just a question. I have no expertise at all with this.
Yes, but you need energy to pump heat, and that has an efficiency maximum (thx ~~Obama~~ Carnot), and radiative cooling scales with the ~4th power of the temperature, so it has to be really hot, and so it requires a lot of energy to "cool down" the already relatively cool side and use that "heat" to heat up the other side that's a thousand degree hotter.
All in all, the cooling system would likely consume more energy than the compute parts.
yes. it is how sats currently handle this. its actually exponentially effective too P = E S A T^4
requires a lot of weight (cooling fluid). requires a lot of materials science (dont want to burn out radiator). requires a lot of moving parts (sun shutters if your orbit ever faces the sun - radiator is going to be both ways).
so that sounds all well and good (wow! 4th power efficiency!) but it's still insanely expensive and if your radiator solution fucks up in any way (in famously easy to service environment space) then your entire investment is toast
now i havent run the math on cost or what elon thinks the cost is, but my extremely favorable back of hand math suggests he's full of it
Be careful with the math there. While a 4th power is awesome you got the Stefan-Boltzman constant to consider and that's on the order of 10^-8
Radiative power is really efficient for hot things but not so great when you're trying to keep things down to normal levels. Efficient for shedding heat from a sun but not so much for keeping a cpu from overheating...
Pet peeve:
T^4 is not exponential in T, it’s polynomial. For exponential, T must be in the exponent, e.g. 2^T or so.
Still, pretty effective.
Having said that, agree that Elon is full of it.
1 reply →
Good intuition, that is generally how radiators work in space.
You can. This is how it is currently done, but it is not easy. It needs to have a large enough surface area to radiate the heat, and also be protected from the sun (as to not collect extra heat). For a data centre, think of an at least 1000m2 heat exchange panel (likely more to train a frontier model).
Sure but if it was a good idea we could do it on earth too and datacenters could stop gurgling a city worth of water
You definitely _can_ the question is, can you do it by enough for a reasonable amount of money. There are a few techniques to this but at the end of the day you need to radiate away, the heat otherwise it will just keep growing. You cannot keep pumping energy into the satellite without distributing the same amount back out again.
yeah if you want a heat thruster
>>This is just a question. I have no expertise at all with this.
On the similar lines, why can't one run a refrigerator in space?
You can, but the heat needs to go somewhere, and now you're back to square one, with "how do I get rid of all this heat". Earth refrigerators have a large heat exchanger on the back for this purpose. In fact now you need to get rid of both of the heat your compute generates and the energy your refrigerator pump uses - an example people often give is that a fridge with an open door actually heats the room, as it spends energy on moving heat around pointlessly.
> Musk is up to something here. This could be another hyperloop (i.e. A distracting promise meant to sabotage competition). It could be a legal dodge. It could be a power grab. What it will not be is a useful source of computing power. Anyone who takes this venture seriously is probably going to be burned.
That.
Also, am I the only one to remember when SpaceX was supposed to pivot to transporting people from cities to cities, given how cheap and reusable and sure BFF/Starship was going to be ?
Or how we were all going to earn money by pooling our full self driving cars in a network of robo taxis ?
In all seriousness, what is the number of "unrealized sci-fi pipe dreams" that is acceptable from the owner a company ? Or, to be fair, what is the acceptable ratio of "pipe dreams" / "actually impressive stuff actually delivered (reusable rockets, starlink, decent EVs, etc...)" ?
You're thinking of outer space. At any distance away from earth where space is so thin that heat dissipation is impossible, then the speed of light will be prohibitive of any workloads to/from space. there is plenty of altitude above the karman line where there is enough atmosphere to dissipate heat. Furthermore, i don't know if they figured it out, but radiation can dissipate heat, that's how we get heat from the sun. Also, given enough input energy (the sun), active closed-cooling systems might be feasible.
https://www.nasa.gov/smallsat-institute/sst-soa/thermal-cont...
But I really hope posts like this don't discourage whoever is investing in this. The problems are solvable, and someone is trying to solve them, that's all that matters. My only concern is the latency, but starlink seems to manage somehow.
Also, a matter of technicality (or so I've heard it said) is that the earth itself doesn't dissipate heat, it transforms or transfers entropy.
> At any distance away from earth where space is so thin that heat dissipation is impossible, then the speed of light will be prohibitive of any workloads to/from space.
Why would they need to get data back to earth for near real time workloads? What we should be thinking about is how these things will operate in space and communicate with each other and whoever else is in space. The Earth is just ancient history
I feel like this is an incredibly fantastic goal-post-moving from the original announcement.
SpaceX: "we're going to put datacenters in space"
HN comments: "obviously we'll need to move human civilization into space first for this to make sense. checks out."
3 replies →
My guess is it’s just another example of his habit of trying to use one of his companies to manufacture demand for another of his companies’ products.
Specifically: Starship makes no economic sense. There simply isn’t any pre-existing demand for the kind of heavy lift capacity and cadence that Starship is designed to deliver. Nor is there anyone who isn’t currently launching heavy payloads to LEO but the only thing holding them back is that they need weekly launches because their use case demands a whole lot of heavy stuff in space on a tight schedule and that’s an all-or-nothing thing for them.
So nobody else has a reason to buy 50 Starship launches per year. And the planned Starlink satellites are already mostly in orbit. So what do you do? Just sell Starship to xAI, the same way he fixed Cybertruck’s demand problem by selling heaps of them to SpaceX.
There might be a lot of induced demand from starship. I’m sure defense is a big one.
No, but really, where will it come from?
If (as seems to be the case) nobody can identify a specific source of latent demand that is large enough to soak up the two order of magnitude increase in the supply of heavy lift launch capacity that Elon wants to deliver, then that strongly suggests that SpaceX does not actually have a business plan for Starship. Or at least, not a business plan that’s been thought through as clearly as a $5 billion (and counting) investment would warrant.
“Defense” is not nearly specific enough to count as an answer. What kind of defense application, specifically, do you have in mind, and why does it need specifically this kind of heavy lift capacity to be viable?
>Specifically: Starship makes no economic sense.
Starship can replace Falcon 9 and probably be cheaper, if fully reusable, so more profitable. So at least some economic sense is there already.
I have noticed that there are two radically different approaches to assessing Starship.
One is based on boring old analysis, hard numbers, and, worst of all, continually updating the analysis as more information (e.g., Raptor’s severe expectations vs reality shortfall) becomes available. People who use this approach don’t seem to have an opinion of Starship that is trending upward.
The other approach seems to be based on vibes, and trusting that Starship will meet its original design goals despite the fact that no rocket project has ever come close to such an achievement. If there’s ever any introspection about why Starship should be the exceptional project that actually does meet its performance goals, the conclusion tends to be something about how Starship is special because it’s being developed by a private company. And I’ve noticed that, if the conversation does get to this point, you can send it in all sorts of unpredictable and fascinating directions by saying words like “OTRAG” and “Conestoga.”
No, that's not how any of this works. Try to think for a moment why we still overwhelmingly use non-jumbo jets for aviation in a world where jumbo jets exist.
1 reply →
> It makes far more sense to build data centers in the arctic.
Unfortunately no. The arctic region is too cold and humid. You need way more energy to manage the cooling of a datacenter there than somewhere hotter.
This is mistaken. In space a radiator can radiate to cold (2.7K) deep space. A thermos on earth cannot. The temperature difference between the inner and outer walls of the thermos is much lower and it’s the temperature difference which determines the rate of cooling.
"Radiate" is exactly what you have to do, and that is extremely slow. You need a huge area to dissipate the amount of power you are talking about.
Basically you concentrate the heat into a high emissivity high temperature material that’s facing deep space and is shaded. Radiators get dramatically smaller as temperature goes up because radiation scales as T⁴ (Stefan–Boltzmann). There are many cases in space where you need to radiate heat - see Kerbal Space Program
2 replies →
I have a vacuum thermos. I've been unimpressed with its ability to keep coffee hot.
>i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot
e.g. the lack-of-a-thing that makes a thermos great at keeping your drink cold too
At risk of stating the obvious - computers produce heat. "Keeping them cool" really means dissipating that heat. Insulating them will cause them to get hotter.
Yes but in this case the lack-of-a-thing keeps GPUs hot
people who do understand thermodynamics will already understand the problem, but innocent people who don't understand thermodynamics should not be misled by poorly chosen examples presented as proof.
I have no idea how it compares to the heat being generated, but one advantage of space would be totally efficient radiative cooling, I believe. Assuming you can pump the heat, and can deploy a large enough surface area (the key question I assume), then you have that at least.
> I would not assume cooling has been worked out.
That's wise.
However, TFA's purpose in assuming cooling (and other difficulties) have been worked out (even though they most definitely have not) was to talk about other things that make orbital datacenters in space economically dubious. As mentioned:
or perhaps as simple as saving xAI for himself as he prepares to offload rest of Twitter?
> Musk is up to something here. This could be another hyperloop (i.e. A distracting promise meant to sabotage competition). It could be a legal dodge. It could be a power grab.
It could also just be ignorance and talking out of his ass to look smart. Like when he took over Twitter and began publicly spewing wrong technical details as if he knew what he was talking about and being corrected by the people actually working on the product.
I suspect Musk has a workable plan of some sort, realistically. Clearly, the one thing that is available in space is an abundance of square meters. There is no need whatsoever to conserve space at sufficient orbit. It is a little counter intuitive as we are so used to needing to conserve all the things.
Power input and heat radiation both scale with area so maybe there is some way to achieve this at scale. For instance, maybe it will not look like a traditional data center or even traditional chips.
The rumor I heard is that Musk's big issue with SpaceX was that he was only able to employ US citizens with a security clearance, as per the limitations of a rocket company, which he has rallied against multiple times.
One of the motivations behind this whole thing could be that he could make a way for foreign talent to work on space projects without the necessary government signoff.
Would that really be that much of an unlock?
2 replies →
> Musk is up to something here.
This is Musk, yet again, pulling themes from sci-fi books. He has that vision of ushering in the "future" which is good for dragging us forward but also he fails a lot. His open letter cited the Kardashev scale and his vision for getting us forward like in the novel accelerando.
He goes on about putting a mass driver on the moon for ultra-low-cost space launches.
His plan here clearly hinges around using robots to create a fully-automated GPU manufacturing and launch facility on the moon. Not launching any meaningful number from earth.
Raises some big questions about whether there are actually sufficient materials for GPU manufacture on the moon... But, whatever the case, the current pitch of earth-launches that the people involved with this "space datacenter" thing are making is a lie. I think it just sounds better than outright saying "we're going to build a self-replicating robot factory on the moon", and we are in the age of lying.
If any single country tried to create a whole production chain to single-handedly manufacture modern computer equipment it would be on the order of decades to see any result. Doing it on the moon is just not realistic this century, maybe the next one. Although i don't think the economics would ever work out.
Do you acknowledge how much change was there in the XX century? How can you probably make such predictions with such confidence?
The ideal would be to park the data centers at the lagrange point behind the Earth in its umbra, so they don't need to dissipate direct solar heat.
Musk lies with ease and routinely. This and Optimus are both just more examples of that.
Its not just cooling thats totally not worked out, its internal networking, its power management (what happens when its in darkness?) how do you certify servers for +/-10g vibration (https://www.ralspace.stfc.ac.uk/Pages/Dynamics-and-vibration...)
What about gamma rays? there is a reason why "space hardened" microcontrollers are MIPS chips from the 90s on massive dies with a huge wedge of metal on it. You can't just take a normal 4micron die and yeet it into space and have done with it.
Then there is the downlink. If you want low latency, then you need to be in Low earth orbit. That means that you'll spend >40% of your time in darkness. So not only do you need to have a MAssive heat exchanger and liquid cooling loop, which is space rated, you need to have ?20mwhr of battery as well (also cooled/heated because swinging +/- 140 C every 90 minutes is not going to make them happy)
Then there is data consistency, is this inference only? or are we expecting to have a mesh network that can do whole "datacentre" cache coherence? because I have bad news for you if you're going to try that.
Its just complete and total bollocks.
utter utter bollocks.
You don't put it in a standard orbit, you put it in a polar orbit with near 100% suntime ... obviously.
Obviously you use the backside of the massive area of PV you need, for an equally massive area for HOPG radiator films with condensor coils (because obviously you use heatpumps for cooling, not pure liquid).
Consider the obvious ways you'd actually do it, not the most naive ways.
The GPU pods obviously won't weigh the same as a terrestrial rack. Space based solar arrays obviously don't weigh the same as your hail and storm resistant panels on your roof (see ROSA, but there might be another 10x weight reduction if using flexible solar in tension from rotation). Noone cares about a couple 100 ms extra for first token.
Solar wind and drag are in my opinion the biggest issue. Problem : it's a giant surface catching drag and solar wind. Solution : it's a giant solar sail. Controlling the angle of PV for useful thrust, that's never really been done for a satellite.
apocalyptic space twitter with satellites shaped like whales that drop from the sky would have been cooler.
Yeah the Space Data Center companies completely gloss over this fact by saying "oh yeah and we'll need radiators 10x the size of our solar panels. NBD."
> It makes far more sense to build data centers in the arctic
This. Like it would make far more sense to colonize the poles than Mars.
It's not just Musk, Google is working on it too... very soon to actually launch tests. I have a feeling it's a regulatory dodge of some kind.
You can't exchange heat with vacuum
If you put a pipe with hot gas inside, in space, it will get colder by convection.
Blow air through the pipe.
ok. your pipe is full. now what
The equation has a ^4 to the temperature. If you raise the temperature of your radiator by ~50 degrees you double its emission capacity. This is well within the range of specialised phase change compressors, aka fancy air conditioning pumps.
Next up in the equation is surface emissivity which we’ve got a lot of experience in the automotive sector.
And finally surface area, once again, getting quite good here with nanotechnology.
Yes he’s distracting, no it’s not as impossible as many people think.
> And finally surface area, once again, getting quite good here with nanotechnology.
So your hot thing is radiating directly onto the next hot thing over, the one that also needs to cool down?
> aka fancy air conditioning pumps
Yeah, pumps, tubes, and fluids are some of the worst things to add to a satellite. It's probably cheaper to use more radiators.
Maybe it's possible to make something economical with Peltier elements. But it's still not even a budget problem yet, it's not plainly not viable.
> getting quite good here with nanotechnology
Small features and fractal surfaces are useless here.
Peltiers and heat pipes don't remove heat, they just move it. You still need the radiator.
My dude, heat pipes were invented for satellites and there’s people walking around with piezo pumps in their phones these days. We’re getting close.
Peltiers generate a lot of heat to get the job done so even though electricity is pretty much free, probably not a sure bet.
Raise the temperature of your radiator by 50 degrees and you double its emission capacity. Or put your radiator in the atmosphere and multiply its heat exchange capacity by a factor of a thousand.
It's not physically impossible. Of course not. It's been done thousands of times already. But it doesn't make any economic sense. It's like putting a McDonald's at the top of Everest. Is it possible? Of course. Is it worth the enormous difficulty and expense to put one there? Not even a little.
For thousands of years we never even looked to Mount Everest, then some bloke on the fiver said he’d give it a shot. Nowadays anyone with the cash and commitment can get the job done.
Same with datacenters in space, not today, but in 1000 years definitely, 100 surely, 10?
As for the economics, it makes about as much sense as running jet engines at full tilt to power them.
2 replies →
Even if you create a material with surface emissivity of 1.0:
- let's say 8x 800W GPUs and neglect the CPU, that's 6400W
- let's further assume the PSU is 100% efficient
- let's also assume that you allow the server hardware to run at 77 degrees C, or 350K, which is already pretty hot for modern datacenter chips.
Your radiator would need to dissipate those 6400W, requiring it to be almost 8 square meters in size. That's a lot of launch mass. Adding 50 degrees will reduce your required area to only about 4.4 square meters with the consequence that chip temps will rise by 50 degrees also, putting them at 127 degrees C.
No CPU I'm aware of can run at those temps for very long and most modern chips will start to self throttle above about 100
Hence the fancy air conditioning pumps
8 replies →
This makes zero sense.
> Next up in the equation is surface emissivity which we’ve got a lot of experience in the automotive sector.
My car doesn't spend too much time driving in vacuum, does yours?
Engine bays have a lot of design go into where to keep heat and where to get rid of it. You can look up thermal coatings and ceramics etc.
2 replies →
Let's just hope the person you are responding to isn't Elon Musk!
1 reply →
All of this and more.
For example: quite apart from the fact of how much rocket fuel is it going to take to haul all this shit up there at the kind of scale that would make these space data centres even remotely worthwhile.
I'm not against space travel or space exploration, or putting useful satellites in orbit, or the advancement of science or anything like that - quite the opposite in fact, I love all this stuff. But it has to be for something that matters.
Not for some deranged billionaire's boondoggle that makes no sense. I am so inexpressibly tired of all these guys and their stupid, arrogant, high-handed schemes.
Because rocket fuels are extremely toxic and the environmental impact of pointlessly burning a vast quantity of rocket fuel for something as nonsensical as data centres in space will be appalling.
Starship is fueled with methane (natural gas) and liquid oxygen which aren't toxic. It does produce a lot of CO2 which is a problem with lots of flights.
IIRC the methane is produced at launch site with considerable pollution
Does that emit more than Elon's terrestrial data centers powered by natural gas, per unit of compute?
I think Musk is backed into a corner financially. Most of his companies don't have that much revenue and their worth is mostly based on hope.
They might be closer to collapsing than most people think. It's not unheard of that a billionaires net worth drops to zero over night.
I think it's mostly financial reasons why they merged the companies, this space datacenter idea was born to justify the merge of SpaceX and xAI. To give investors hope, not to really do it.
“Musk is on to something here”? Really? Any high school student with a basic grasp of physics could explain that. But sure, the idiot billionaire nazi “is on to something”. That’s giving him too much credit.
Of course it doesn’t fucking make sense to put data centers into space. Even if heating were solved somehow magically, server disks are veeery prone to fail and need replacement. Shoot a rocket up every week to replace failed drives or absolutely burned through GPUs? Yeah, that doesn’t even remotely sound feasible.
Unless you want cash-rich AI companies to pay a certain company for weekly / daily lifts during the build-out phase. Eventual crash be damned, make hay while the sun shines
And burn even more energy and fuel than DCs on the ground, great idea :D
1 reply →
The materialist take is that his plan is to eventually over-value and then trade on his company valuations, and also have another merger lined up for future personal financial bailouts.
> You can't exchange heat with vacuum. You can only radiate heat into it.
I don’t remember the difference from my science classes, isn’t This the same thing essentially?
The other two methods of heat transfer apart from radiation are conduction (through “touch”, adjacent molecules, eg from the outside of a chicken on the BBQ to the inside) and convection (through movement, eg cold air or water flowing past).
quantum computers on the sun!
Not going to read the article, because Data centers in space = DOA is common sense to me, however, did the article really claim cooling wasn't an issue? Do they not understand the laws of thermodynamics, physics, etc?
Sure, space is cold. Good luck cooling your gear with a vacuum.
Don't even get me started on radiation, or even lack of gravity when it comes to trying to run high powered compute in space. If you think you are just going to plop a 1-4U server up there designed for use on earth, you are going to have some very interesting problems pop up. Anything not hardened for space is going to have a very high error/failure rate, and that includes anything socketed...
> Not going to read the article, because Data centers in space = DOA is common sense to me, however, did the article really claim cooling wasn't an issue?
No. Nearly everyone that talks about data centers in space talks about cooling. The point of this article was to talk about other problems that would remain even if the most commonly talked about problems were solved.
It says:
> But even if we stipulate that radiation, cooling, latency, and launch costs are all solved, other fundamental issues still make orbital data centers, at least as SpaceX understands them, a complete fantasy.
and then talks about some of those other issues.
Not disagreeing with you at all: that physics fact always come up. My honest question is: if it's a perfect thermos, what does, for example, the ISS do with the heat generated by computers and humans burning calories? The ISS is equipped with a mechanism to radiate excess heat into space? Or is the ISS slowly heating up but it's not a problem?
Massive radiators. In this photo[0], all of the light gray panels are thermal radiators. Note how they are nearly as large as the solar panels, which gives you an idea about the scale needed to radiate away 3-12 people's worth of heat (~1200 watts) + the heat generated by equipment.
[0] https://images-assets.nasa.gov/image/jsc2021e064215_alt/jsc2...
The ISS is designed to emit 126kW of heat radiation between the active cooking systems and the solar array cooling system.
1 reply →
I agree, all the good papers definitely talk about custom designed radiators being used on the dark sides of data center in space.
Let me google that for you.
https://en.wikipedia.org/wiki/External_Active_Thermal_Contro...
The ISS has giant heat sinks[1]. Those heat sinks are necessary for just the modest heat generated on the ISS, and should give an idea of what a sattelite full of GPU's might require...
[1] https://en.wikipedia.org/wiki/External_Active_Thermal_Contro...
The ISS has MASSIVE radiators. Most of its volume is radiator. 900 cubic meters of space 2500 square meters of radiator.
The TL;DR is they radiate it into space via large, high surface area arms that stick out of the station.
It will be the communications, not the compute part.
One man able to put a data center worth of mass in orbit is one man able to crash a datacenter worth of mass into Earth anywhere he wants.
Not a given. Re enter the atmosphere. Sure. Avoid vaporization? Much harder problem.
I think it's actually the other way around, satellites need to be specifically designed to burn up fast in the atmosphere. See for example the warnings about space debris from Chinese satellites not designed with this in mind.
There is some evidence to suggest that spacex knows how to reenter an object without burning it up.
2 replies →
100 tons of steel will not vaporize before it hits the ground
A glaring lack of oceans to boil
Jeffrey Epstein's friend Elon Musk is trying to stop a financial disaster in xAi that would expose how irresponsible he is. He's gonna put all that in a company that has real money coming from government and soon will get retail investors money.
I think people underestimate how quickly heat radiates to space. A rock in orbit around Earth will experience 250F/125C on the side facing the Sun, and -173C/-280F on the other side. The ability to rotate an insulating shield toward the sun means you're always radiating.
I think you may be overestimating how quickly this happens and underestimating how much surface area that rock has. Given no atmosphere, the fact that the rock with 1/4 the radius of Earth has a temperature differential of only 300C between the hot side and the cold side, there's not a lot of radiation happening.
In deep space (no incident power) you need roughly 2000 sq meters of surface area per megawatt if you want to keep it at 40C. That would mean your 100 MW deep space datacenter (a small datacenter by AI standards) needs 200000 sq meters of surface area to dissipate your heat. That is a flat panel that has a side length of 300 meters (you radiate on both sides).
Unfortunately, you also need to get that power from the sun, and that will take a square with a 500 meter side length. That solar panel is only about 30% efficient, so it needs a heatsink for the 70% of incident power that becomes heat. That heatsink is another radiator. It turns out, we need to radiate a total of ~350 MW of heat to compute with 100 MW, giving a total heatsink side length of a bit under 600 meters.
All in, separate from the computers and assuming no losses from there, you need a 500x500 meter solar panel and a 600x600 meter radiator just for power and heat management on a relatively small compute cluster.
This sounds small compared to things built on Earth, but it's huge compared to anything that has been sent to space before. The ISS is about 100 meters across and about 30 meters wide for comparison.
First, thanks for your knowledgeable input.
Second, are you saying that we basically need to have a radiator as big (approximately) as the solar panels?
That is a lot, but it does sound manageable, in the sense that it approximately doubles what we require anyway for power.
So, not saying that it’s easy or feasible, but saying that cooling then seems “just” as difficult as power, not insurmountably more difficult. (Note that the article lists cooling, radiation, latency, and launch costs as known hard problems, but not power.)
1 reply →
What do you think about droplet radiators? E.g. using a ferrofluid with magnetic containment for capture and enough spare on board to last five years of loss due to occasional splashes?
> 2000 sq meters of surface area per megawatt if you want to keep it at 40C
What is this figure based on?
> it's huge compared to anything that has been sent to space before
That is the goal of Starship though. The ISS has a mass of 400 ton, the goal is to need only two cheap launches of Starship v4 for that.
> It makes far more sense to build data centers in the arctic.
Please, no!
I want to nitpick you here but a thermos is specifically good at insulating because not only does it have a vacuum gap, it's also got two layers of metal (inner and outer) to absorb and reflect thermal radiation.
That specific aspect is NOT true in space because there's nothing stopping thermal radiation.
Now you're correct that you can't remove heat by conduction or convection in space, but it's not that hard to radiate away energy in space. In fact rocket engine nozzle extensions of rocket upper stages depend on thermal radiation to avoid melting. They glow cherry red and emit a lot of energy.
By Stefan–Boltzmann law, thermal radiation goes up with temperature to the 4th power. If you use a coolant that lets your radiator glow you can conduct heat away very efficiently. This is generally problematic to do on Earth because of the danger of such a thing and also because such heat would cause significant chemical reactions of the radiator with our corrosive oxygen atmosphere.
Even without making them super hot, there's already significant energy density on SpaceX's satellites. They're at around 75 kW of energy generation that needs to be radiated away.
And on your final statement, hyperloop was not used as a "distraction" as he never even funded it. He had been talking about it for years and years until fanboys on twitter finally talked him into releasing that hastily put together white paper. The various hyperloop companies out there never had any investment from him.
> a thermos is specifically good at insulating because not only does it have a vacuum gap, it's also got two layers of metal (inner and outer) to absorb and reflect thermal radiation.
Not necessarily. There are many modern thermos "cups" that are just a regular cup, except with two layers of glass and a vacuum. Even the top is open all the time. (e.g. https://www.ikea.com/us/en/p/passerad-double-wall-glass-8054... )
It's still good enough to keep your coffee hot for an entire day.
It is well known that Musk primary reason to push Hyperloop was because he didn’t want them to build a high speed rail for some reason:
> Musk admitted to his biographer Ashlee Vance that Hyperloop was all about trying to get legislators to cancel plans for high-speed rail in California—even though he had no plans to build it.
https://time.com/6203815/elon-musk-flaws-billionaire-visions...
musk is always up to something but remarkably people still eat this stuff up - remarkable to watch!
[dead]
[flagged]
There are several companies working on this, and the first generation tech is already proven, working in space on the ISS. Even Paul G is on board. https://x.com/paulg/status/2009686627506065779?s=20
Of course it's working. We've had computers operating in space for decades. There's no doubt it can be done.
The question isn't whether it's possible, the question is why you'd do it just for data centers. We put computers in space because they're needed to do things that can only be done from there. Data centers work just fine on the ground. What's so great about data centers in space that makes them worth the immense cost and difficulty.
I know a lot of prominent people are talking about this. I do not understand it. pg says "when you look at the tradeoffs" well what exactly is he looking at? Because when I look at the tradeoffs, the whole concept makes no damned sense. Sure, you can put a bunch of GPUs in space. But why would you do that when you can put them in a building for orders of magnitude less money?
https://xcancel.com/paulg/status/2009704615508586811#m for those who don't partake.
I liked one comment someone made: if it's just about dodging regulation, then put the data centers on container ships. At any given time, there are thousands of them sailing in international waters, and I'm sure their operators would love to gain that business.
That being said, space would be a good place to move heat around with Peltier elements. A lot of the criticisms revolve around the substantial amount of coolant plumbing that will be needed, but that may not necessarily be what SpaceX has in mind.
> I would not assume cooling has been worked out.
There should be some temperature where incoming radiation (sunlight) balances outgoing radiation (thermal IR). As long as you're ok with whatever that temperature is at our distance from the sun, I'd think the only real issue would be making sure your satellite has enough thermal conductivity.
The Stefan-Boltzmann Law tells us that radiative power scales to the fourth power of temperature (T^4). While terrestrial cooling is largely linear and dependent on ambient air/water temperature (the "wet-bulb" limit), a radiator in space is dumping heat into a 3-Kelvin sink. That thermal gradient is massive.
This is misleading: - A radiator only “sees” 3 K if it’s perfectly shielded from the Sun, Earth albedo, and Earth IR. In Earth orbit you can easily get hundreds of W/m^2 incident; without sunshields the net rejectable heat is greatly reduced. - You have a "massive" advantage only if the radiator is allowed to run very hot: At 300–310 K with \epsilon \approx 0.9: about 400–500 W/m^2. Effective "radiative heat transfer coefficient" at 300 K: h_rad \approx 4\epsilon\sigma T^3 \approx 5-6 W/m^2K. That's orders of magnitude lower than forced convection in air (\approx 50–500 W/m^2K) or the water side of a heat exchanger (>=1000 W/m^2K).
Yeah I took the best case scenario in space, I did not account for anything else. I imagine the space DC be like two sides, one is pointing towards the sun and being a solar panel the other is a cold radiator radiating heat into the void. I am not sure how feasible this is.
The thermal gradient in space is meaningless because there is hardly any matter to dump the energy into. This means you are entirely reliant on thermal radiation. If you look at the numbers given by Stefan-Boltzmann law you'd see that means to radiate a significant amount of energy you need a combination of a lot of surface area and high temperatures.
This means you need some sort of heat pump. For a practical example you can look at the ISS, which has what they call the "External Active Thermal Control System" (EATCS), it's a complicated system and it provides 70kW of heat rejection. A datacenter in space would need to massively scale up such a system in order to cool itself.
The ISS comparison is a bit of a category mismatch. The EATCS is complex because it’s a life-support system that must keep humans at exactly 22C (295K) while managing ammonia loops in a manned environment.
Computers aren't humans. High-performance silicon can comfortably operate at a junction temperature of 80C to 90C (approx. 360K). Because of that T^4 relationship, a radiator at 85C rejects nearly double the heat per square meter than a radiator at 20C, unless I miss something.
So this makes it a bit more nuanced.
Stefan-Boltzmann is about absolute, not relative temperature.
When one does the math on the operating temperatures of regular computing equipment that we use on Earth, how much heat it generates per watt, and how fast it would need to sink that heat to allow for continuous operation, one gets surface areas that are not impossible, but are pretty on the high end of anything we've ever built in space.
And then you have to deflect the incoming light from the Sun which will be adding to your temperature (numbers published by private space companies regarding the tolerances of payloads those companies are willing to carry note that those payloads have to be tolerant of temperatures exceeding 100° C, from solar radiation alone). That is doable, you could sunshield the sensitive equipment and possibly decrease some of your thermal input load by putting your craft out near L2 which hangs out in the penumbra of Earth. Still a daunting technical challenge when the alternative is just build it on the planet with the technology and methods we already have.
You’re correct that Stefan-Boltzmann uses absolute temperature (K), but that only reinforces the advantage of moving the "hot side" of the gradient up. If you increase your radiator temp from 300K (standard Earth ambient) to 360K (hot silicon), your radiative efficiency doesn't just go up by 20%—it nearly doubles.
The Solar Load is Directional: Unlike a terrestrial atmosphere where heat is omnidirectional, space allows for "shadow engineering." A simple multi-layer insulation (MLI) sunshield can reduce solar flux by orders of magnitude. We do this for the James Webb Space Telescope to keep instruments at 7K while the sun-facing side is at 380K. For a data center, you don't need 7K; you just need to keep the "dark side" radiators in the shade.
[dead]
Space is a vacuum and yet here we are on a rock floating in space warmed by the sun and the temperate is actually pretty comfortable. Indeed, without the greenhouse effect it would be positively chilly. An important part of a thermos is that you have to use high albedo materials in the vacuum chamber or else it would lose heat too quickly to radiation.
A satellite as a whole will come to thermal equilibrium with space at a fairly reasonable temperature, the problematic part is that the properties of electricity make it easy to concentrate a good part of the incoming energy in a small area where the GPU is. Heat is harder to move than electricity and getting that heat back out to the solar panels or radiators requires either heavy heat pipes or complex coolant pumps.
a data center in space doesn't have a gigantic rock taking up most of its area, a data center in space is 100% data center 0% rock.
If it had the same data center to rock ratio as earth, it would just end up being earth in the end, and earth doesn't seem to be wanting to stick to its equilibrium either right now
The rock in this case acts as extra thermal mass that makes it take longer to reach thermal equilibrium, but doesn't change what the ultimate thermal equilibrium is. Only the configuration of the parts of the surface that can absorb or radiate electromagnetic radiation do that. And because rock is a fairly good insulator we only really benefit from the top layer and if the sun went out we would all freeze in a week or so.
2 replies →
Well, they do have silicon, with some more additives they can make rocks in space! And throw them at earth, that will show em
>I would not assume cooling has been worked out
On the other hand Starlink has several thousand satellites up there using solar power to run processors and cooling them with radiators so it's not totally new technology.
Here's a Musk tweet linking some analysis https://x.com/elonmusk/status/2013676764099199156