[gpt5]

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?

[hirsin]

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.

[pera]

New GPU dense racks are going up to 300kW, but I believe the normal at moment for hyperscalers is somewhere around ~150kW, can someone confirm?

The energy demand of these DCs is monstrous, I seriously can't imagine something similar being deployed in orbit...

[tensor]

How much of that power is radiated as the radio waves it sends?

[mike_hearn]

But the focus on building giant monolithic datacenters comes from the practicalities of ground based construction. There are huge overheads involved with obtaining permits, grid connections, leveling land, pouring concrete foundations, building roads and increasingly often now, building a power plant on site. So it makes sense to amortize these overheads by building massive facilities, which is why they get so big.

That doesn't mean you need a gigawatt of power before achieving anything useful. For training, maybe, but not for inference which scales horizontally.

With satellites you need an orbital slot and launch time, and I honestly don't know how hard it is to get those, but space is pretty big and the only reasons for denying them would be safety. Once those are obtained done you can make satellite inferencing cubes in a factory and just keep launching them on a cadence.

I also strongly suspect, given some background reading, that radiator tech is very far from optimized. Most stuff we put into space so far just doesn't have big cooling needs, so there wasn't a market for advanced space radiator tech. If now there is, there's probably a lot of low hanging fruit (droplet radiators maybe).

[lloeki]

For another reference, the Nvidia-OpenAI deal is reportedly 10GW worth of DC.

[kimixa]

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.

[sandworm101]

Whatever 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.

[ineedasername]

Why would they bother to build space data center in such monolithic massive structures at all? Direct cables between semi-independent units the size of a star link v2 satellite. That satellite size is large enough to encompass a typical 42U server rack even without much physical reconfiguration. It doesn't need to be "warehouse sized building, but in space", and neither does it have to be countless objects kilometers apart from each other beaming data wirelessly. A few dozen wired as a cluster is much more than sufficient to avoid incurring any more bandwidth penalties on server-to-server communication with correlated work loads than we already have on earth for most needs.

Of course this doesn't solve the myriad problems, but it does put dissipation squarely in the category of "we've solved similar problems". I agree there's still no good reason to actually do this unless there's a use for all that compute out there in orbit, but that too is happening with immense growth and demand expected for increased pharmaceutical research and various manufacturing capabilities that require low/no gravity.

[abalone]

> using wireless communication means even less bandwidth between nodes, more noise as the number of nodes grows, and significantly higher power use

Space changes this. Laser based optical links offer bandwidth of 100 - 1000 Gbps with much lower power consumption than radio based links. They are more feasible in orbit due to the lack of interference and fogging.

> Building data centres in the middle of the sahara desert is still much better in pretty much every metric

This is not true for the power generation aspect (which is the main motivation for orbital TPUs). Desert solar is a hard problem due to the need for a water supply to keep the panels clear of dust. Also the cooling problem is greatly exacerbated.

[space_fountain]

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?)

[WillPostForFood]

What 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.

[smileeeee]

The 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.

[murderfs]

> 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...

[trhway]

>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

>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.

[JumpCrisscross]

> 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.

[tw04]

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.

[Aurornis]

> 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.

[javascriptfan69]

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.

[_fizz_buzz_]

This 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.

[jdhwosnhw]

> 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.

[pdpi]

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...

[MadnessASAP]

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

[adrian_b]

The 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.

[ViewTrick1002]

Which GPU runs at 1400C?

[gclawes]

Starlink satellites also radiate a non-trivial amount of the energy they consume from their phased arrays

[markhahn]

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.

[hackernudes]

High latency to earth but low latency (potentially) to other satellites.

[kristjansson]

50MW might be one aisle of a really dense DC. A single rack might draw 120kW.

[ErroneousBosh]

> 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.

[padjo]

Are starlink satellites in sun synchronous orbits? Doesn't constant solar heating change the energy balance quite a bit?

[antonvs]

> 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.

[whiplash451]

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?

[PurpleRamen]

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.

[michaelmrose]

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?

[adgjlsfhk1]

> 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).

[rootnod3]

Forget heat. Replacing disks alone is a deal breaker on that one.

[Sharlin]

Square–cube law.

[chairmansteve]

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.

[phs318u]

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.

[thebolt00]

It's linear to surface area, but 4th power to temperature.

[cjfd]

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.

[ndsipa_pomu]

> The law of Stefan-Boltzman is free and open source... What do you mean by "open source"? Can we contribute changes to it?