[yabones]

Yeah, I don't see a way to get around the fact that space is a fabulous insulator. That's precisely how expensive insulated drink containers work so well.

If it was just about cooling and power availability, you'd think people would be running giant solar+compute barges in international waters, but nobody is doing that. Even the "seasteading" guys from last decade.

These proposals, if serious, are just to avoid planning permission and land ownership difficulties. If unserious, it's simply to get attention. And we're talking about it, aren't we?

[eldenring]

You should read the linked article, they talk about it there. You radiate the heat into space which takes less surface area than the solar panels and you can just have them back to back.

In general I don't understand this line of thinking. This would be such a basic problem to miss, so my first instinct would be to just look up what solution other people propose. It is very easy to find this online.

[mkesper]

Please have a look at how real stations like ISS handle the problem and do not trust in should-work science fiction. It's hard. https://en.wikipedia.org/wiki/International_Space_Station#Po...

[jcattle]

Taking a system which was conceptualized about a quarter of a century ago and serves much different needs than what a datacenter in space needs (e.g. very strict thermal band, compared to acceptable temperature range from 20 to 80 degrees) isn't ideal.

The physics is quite simple and you can definitely make it work out. The Stefan Boltzman law works in your favor the higher you can push your temperatures.

If anything a orbital datacenter could be a slightly easier case. Ideally it will be in an orbit which always sees the sun. Most other satellites need to be in the earth shadow from time to time making heaters as well radiators necessary.

[uplifter]

These data centers are solar powered, right? So if they are absorbing 100% of the energy on their sun side, by default they'll be able to heat up as much as an object left in the sun, which I assume isn't very hot compared to what they are taking in. How do they crank their temperature up so as to get the Stefan Boltzmann law working in their favor?

I suppose one could get some sub part of the whole satellite to a higher temperature so as to radiate heat efficiently, but that would itself take power, the power required to concentrate heat which naturally/thermodynamically prefers to stay spread out. How much power does that take? I have no idea.

[TheOtherHobbes]

σ is such a small number in Stefan-Boltzman that it makes no difference at all until your radiators get hot enough to start melting.

You not only need absolute huge radiators for a space data centre, you need an active cooling/pumping system to make sure the heat is evenly distributed across them.

I'm fairly sure no one has built a kilometer-sized fridge radiator before, especially not in space.

You can't just stick some big metal fins on a box and call it a day.

[torginus]

Out of curiosity, I plugged in the numbers - I have solar at home, and a 2 m2 panel makes about 500w - i assume the one in orbit will be a bit more efficient without atmosphere and a bit more fancy, making it generate 750w.

If we run the radiators at 80C (a reasonable temp for silicon), that's about 350K, assuming the outside is 0K which makes the radiator be able to radiate away about 1500W, so roughly double.

Depending on what percentage of time we spend in sunlight (depends on orbit, but the number's between 50%-100%, with a 66% a good estimate for LEO), we can reduce the radiator surface area by that amount.

So a LEO satellite in a decaying orbit (designed to crash back onto the Earth after 3 years, or one GPU generation) could work technically with 33% of the solar panel area dedicated to cooling.

Realistically, I'd say solar panels are so cheap, that it'd make more sense to create a huge solar park in Africa and accept the much lower efficiency (33% of LEO assuming 8 hours of sunlight, with a 66% efficiency of LEO), as the rest of the infrastructure is insanely more trivial.

But it's fun to think about these things.

[wongarsu]

It's definitely a solvable problem. But it is a major cost factor that is commonly handwaved away. It also restricts the size of each individual satellite: moving electricity through wires is much easier than pumping cooling fluid to radiators, so radiators are harder to scale. Not a big deal at ISS scale, but some proposals had square kilometers of solar arrays per satellite

[jofer]

That exactly. It's not that it's impossible. It's that it's heavy to efficiently transport heat to the radiators or requires a lot of tiny sats, which have their with problems.

[kristianbrigman]

But heat = energy, right? So maybe we don’t really want to radiate it, but redirect it back into the system in a usable way and reduce how much we need to take in? (From the sun etc)

[jdhwosnhw]

Useful, extractable energy comes from a temperature differential, not just temperature itself. Once your system is at temperature equilibrium, you cant extract energy anymore and must shed that temperature as heat

[dzhiurgis]

Enter https://en.wikipedia.org/wiki/Thermophotovoltaic_energy_conv...

[jdhwosnhw]

This still relies on a heat differential, as described in the Details section of your linked article: https://en.wikipedia.org/wiki/Thermophotovoltaic_energy_conv...

[estimator7292]

That's not how physics works. Heat in and of itself does not contain usable energy. The only useful energy to be extracted from heat comes from the difference in temperature between two objects. You can only extract work from thermal energy by moving heat from one place to another, which can only happen by moving energy from a hot object to a cold one.

This is all fundamental to the universe. All energy in the universe comes exclusively from systems moving from a low entropy state to a higher entropy state. Energy isn't a static absolute value we can just use. It must be extracted from an energy gradient.