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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 o
by gpt5 9mo ago
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?
- space_fountain 9mo agoIt'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?)
- murderfs 9mo ago> The maintenance costs are higher because the lifetime of satellites is pretty low Presumably they're planning on doing in-orbit propellant transfer to reboost the satellites so that they don't have to let their GPUs crash into the ocean...
- sanex 9mo agoOr maybe they want to just use them hard and deorbit them after three yesrs?
- JumpCrisscross 9mo ago> Presumably they're planning on doing in-orbit propellant transfer to reboost the satellites so that they don't have to let their GPUs crash into the ocean Hell, you're going to lose some fraction of chips to entropy every year. What if you could process those into reaction mass?
- falcor84 9mo agoThis brings a whole new dimension to that joke about how our software used to leak memory, then file descriptors, then ec2 instances, and soon we'll be leaking entire data centers. So essentially you're saying - let's convert this into a feature.
- lambdaone 9mo agoIt's certainly one way to do arena-based garbage collection.
- 3eb7988a1663 9mo agoI believe that a modern GPU will burn out immediately. Chips for space are using ancient process nodes with chunky sized components so that they are more resilient to radiation. Deploying a 3nm process into space seems unlikely to work unless you surround it with a foot of lead.
- mike_hearn 9mo agoOr cooling water/oil?
- JumpCrisscross 9mo ago> Or cooling water/oil? Oh. You surround it with propellant. In a propellant depot.
- mike_hearn 8mo agoHah, kill three birds with one stone? The satellites double up as propellant depots for other space missions, that just happen to have GPUs inside? And maybe use droplet radiators to expel the low grade heat from the propellant. I wonder if that can be made safe at all. They use propellant to cool the engine skins so... maybe?
- XorNot 9mo agoAnd just like that you've added another not never done before, and definitely not at scale problem to the mix. These are all things which add weight, complexity and cost. Propellant transfer to an orbital Starship hasn't even been done yet and that's completely vital to it's intended missions.
- zeofig 9mo ago"Planning" is a strong word..
- mlyle 9mo agoAnother significant factor is that radiation makes things worse. Ionizing radiation disrupts the crystalline structure of the semiconductor and makes performance worse over time. High energy protons randomly flip bits, can cause latchup, single event gate rupture, destroy hardware immediately, etc.
- Aerolfos 9mo agoIf anything, considering this + limited satellite lifetime, it almost looks like a ploy to deal with the current issue of warehouses full of GPUs and the questions about overbuild with just the currently actively installed GPUs (which is a fraction of the total that Nvidia has promised to deliver within a year or two). Just shoot it into space where it's all inaccessible and will burn out within 5 years, forcing a continuous replacement scheme and steady contracts with Nvidia and the like to deliver the next generation at the exact same scale, forever
- JumpCrisscross 9mo ago> Everything about operating a datacenter in space is more difficult than it is to operate one on earth Minus one big one: permitting. Every datacentre I know going up right now is spending 90% of their bullshit budget on battlig state and local governments.
- deepGem 9mo agoThis is a huge one. What Musk is looking for is freedom from land acquisition. Everything else is an engineering and physics problem that he will somehow solve. The land acquisition problem is out of his hands and he doesn't want to deal with politicians. He learned from building out the Memphis DC.
- EdwardDiego 9mo agoSo freedom from law and regulation?
- deepGem 9mo ago[flagged]
- jeltz 9mo agoSo why does he not build here in Europe then? Getting a permit for building a data center in Sweden is just normal industrial zoning that anyone can get for cheap, there is plenty of it. Only challenge is getting enough electricity.
- deepGem 9mo agoI meant Europe is an example of how not to do regulation. The problem you just mentioned. If you get land easily electricity won't be available and vice versa.
- aforwardslash 9mo ago
- trhway 9mo ago>1. The capital costs are higher, you have to expend tons of energy to put it into orbit putting 1KW of solar on land - $2K, putting it into orbit on Starship (current ground-based heavy solar panels, 40kg for 4m2 of 1KW in space) - anywhere between $400 and $4K. Add to that that the costs on Earth will only be growing, while costs in space will be falling. Ultimately Starship's costs will come down to the bare cost of fuel + oxidizer, 20kg per 1kg in LEO, i.e. less than $10. And if they manage streamlined operations and high reuse. Yet even with $100/kg, it is still better in space than on the ground. And for cooling that people so complain about without running it in calculator - https://news.ycombinator.com/item?id=46878961 https://news.ycombinator.com/item?id=46878961 >2. The maintenance costs are higher because the lifetime of satellites is pretty low it will live those 3-5 years of the GPU lifecycle.
- viraptor 9mo ago> will come down to the bare cost of fuel + oxidizer And maintenance and replacing parts and managing flights and ... You're trying to yadda-yadda so much opex here!
- trhway 9mo agoIt is SpaceX/Elon who bet billions on that yadda-yadda, not me. I wrote "If" for $10/kg. I'm sure though that they would easily yadda-yadda under sub-$100/kg - which is $15M per flight. And even with those $100/kg the datacenters in space still make sense as comparable to ground based and providing the demand for the huge Starship launch capacity. A datacenter costs ~$1000/ft^2. How much equipment per square foot is there? say 100kg (1 ton per rack plus hallway). Which is $1000 to put into orbit on Starship at $100/kg. At sub-$50/kg, you can put into orbit all the equipment plus solar panels and it would still be cheaper than on the ground.
- javascriptfan69 9mo ago100 x 100 is 10,000.
- sarchertech 9mo ago
- WillPostForFood 9mo agoWhat about sourcing and the cost of energy? Solar Panels more efficient, no bad weather, and 100% in sunlight (depending on orbit) in space. Not that it makes up for the items you listed, but it may not be true that everything is more difficult in space.
- edoceo 9mo agoI'm stretched to think of one thing that is easier in space. Anything I could imagine still requires getting there (in one piece)
- blipvert 9mo agoAchieving a zero-gravity environment, or a vacuum?
- esquivalience 9mo agoDeath, and some science. That's it?
- ljsprague 9mo agoHorseshoes.
- DharmaPolice 9mo agoNoise insulation.
- pclmulqdq 9mo agoSolar panels in space are more efficient, but on the ground we have dead dinosaurs we can burn. The efficiency gain is also more than offset by the fact that you can't replace a worn out panel. A few years into the life of your satellite its power production drops.
- duskwuff 9mo ago> Solar panels in space are more efficient... ... if you completely ignore the difficulty of getting them up there. I'd be interested to see a comparison between the amount of energy required to get a solar panel into space, and the amount of energy it produces during its lifetime there. I wouldn't be surprised if it were a net negative; getting mass into orbit requires a tremendous amount of energy, and putting it there with a rocket is not an efficient process.
- smileeeee 9mo agoThe cost might be the draw (if there is one). Big tech isn't afraid of throwing money at problems, but the AI folk and financiers are afraid of waiting and uncertainty. A satellite is crazy expensive but throwing more money at it gets you more satellites. At the end of the day I don't really care either way. It ain't my money, and their money isn't going to get back into the economy by sitting in a brokerage portfolio. To get them to spend money this is as good a way as any other, I guess. At least it helps fund a little spaceflight and satellite R&D on the way.
- actionfromafar 9mo agoIt's just tax payer money, who cares right? :)
- tw04 9mo agoAmazon’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.
- Aurornis 9mo ago> 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.
- hirsin 9mo agoSimply 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.
- tensor 9mo agoHow much of that power is radiated as the radio waves it sends?
- adgjlsfhk1 9mo agothe majority is likely in radio waves and the inter satellite laser communication
- hirsin 9mo agoGood point - the comms satellites are not even "keeping" some of the energy, while a DC would. I _am_ now curious about the connection between bandwidth and wattage, but I'm willing to bet that less than 1% of the total energy dissipation on one of these DC satellites would be in the form of satellite-to-earth broadcast (keeping in mind that s2s broadcast would presumably be something of a wash).
- markhahn 9mo ago50MW 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.
- hackernudes 9mo agoHigh latency to earth but low latency (potentially) to other satellites.
- javascriptfan69 9mo agoStarlink provides a service that couldn't exist without the satellite infrastructure. Datacenters already exist. Putting datacenters in space does not offer any new capabilities.
- _fizz_buzz_ 9mo agoThis is the main point I think. I am very much convinced that SpaceX is capbable to put a datacenter into space. I am not convinced they can do it cheaper than building a datacenter on earth.
- notahacker 9mo agoI would be a lot more convinced they had found a way to solve the unit economics if it was being used to secure billion dollar deposits from other companies rather than as the narrative for rolling a couple of Elon's loss making companies into SpaceX and IPOing...
- adgjlsfhk1 9mo ago> 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).
- gclawes 9mo agoStarlink satellites also radiate a non-trivial amount of the energy they consume from their phased arrays
- antonvs 9mo ago> 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.
- kristjansson 9mo ago50MW might be one aisle of a really dense DC. A single rack might draw 120kW.
- pdpi 9mo ago5kW 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/supermicro-hgx-h200-gpu-server https://www.arccompute.io/solutions/hardware/gpu-servers/sup...
- MadnessASAP 9mo agoI 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 https://news.ycombinator.com/item?id=46087616#46093316
- ViewTrick1002 9mo agoWhich GPU runs at 1400C?
- MadnessASAP 9mo agoOne made of steel presumably. I would assume such a setup involves multiple stages of heat pumps to from GPU to 1400C radiatoe. Obviously that's going to impact efficiency. Also I'm not seriously suggesting that 1400C radiators is a reasonable approach to cooling a space data centre. It's just intended to demonstrate how infeasible the idea is.
- adrian_b 9mo agoThe idea of using heat pumps to increase the temperature of the radiator is unlikely to allow an increase of the fraction of the original amount of heat that is radiated per heatsink surface, i.e. the added heat may be higher than the additionally radiated heat, though I am too lazy to compute now whether this is possible. Moreover, a heat pump would add an equipment with moving parts that can fail, requiring maintenance.
- deleted 9mo ago[deleted]
- adrian_b 9mo agoThe temperature of space datacenters will be limited to 100 Celsius degrees, because otherwise the electronic equipment will be destroyed. So your huge metal plate would radiate (1673/374)^4 = 400 times less heat, i.e. only 125 kW. In reality, it would radiate much less than that, even if made of copper or silver covered with Vantablack, because the limited thermal conductivity will reduce the temperature for the parts distant from the body.
- phs318u 9mo agoBecause 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.
- thebolt00 9mo agoIt's linear to surface area, but 4th power to temperature.
- dguest 9mo agoAlso worth noting that if computing power scales with volume then surface area (and thus radiation) scales like p^2/3. In other words, for a fixed geometry, the required heat dissipation per unit area goes like p^1/3. This is why smaller things can just dissipate heat from their surface, whereas larger things require active cooling. I'm not a space engineer but I'd imagine that smaller satellites can make due with a lot of passive cooling on the exterior of the housing, whereas a shopping-mall sized computer in space would will require a lot of extra plumbing.
- phs318u 9mo agoThanks for the correction. Last time I looked at it was in 2nd year Thermodynamics in 1985.
- padjo 9mo agoAre starlink satellites in sun synchronous orbits? Doesn't constant solar heating change the energy balance quite a bit?
- cjfd 9mo agoSure, 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.
- ndsipa_pomu 9mo ago> The law of Stefan-Boltzman is free and open source... What do you mean by "open source"? Can we contribute changes to it?
- PurpleRamen 9mo agoA 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.
- Sharlin 9mo agoSquare–cube law.
- michaelmrose 9mo agoWhy 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?
- chairmansteve 9mo agoA 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.
- kimixa 9mo agoOutput 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.
- sandworm101 9mo agoWhatever sat datacenter they biuld, it would run better/easier/faster/cheaper sitting on the ground in antarctica than it would in space, or floating on the ocean, without the launch costs. Space is useful for those activities that can only be done from space. For general computing? Not until all the empty parts of the globe are full. This is a pump-and-dump bid for investor money. They will line up to give it to him.
- krisoft 9mo ago> Whatever sat datacenter they biuld, it will run better/easier/faster/cheaper sitting on the ground in antarctica than it will in space That is clearly not true. How do you power the data center on antarctica? May i remind you it will be in the shadow of earth for half a year.
- ErroneousBosh 9mo ago> 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.
- rootnod3 9mo agoForget heat. Replacing disks alone is a deal breaker on that one.
- jdhwosnhw 9mo ago> 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.
- whiplash451 9mo agoNot 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?
- deleted 9mo ago[deleted]