these same comments pop up every time someone brings up satellite data-centers where people just assume the only way of dissipating heat is through convection with the environment.
No, we just "assume" (i.e. know) that radiation in a vacuum is a really bad way of dissipating heat, to the point that we use vacuum as a very effective insulator on earth.
Yes, you can overcome this with enough radiator area. Which costs money, and adds weight and space, which costs more money.
Nobody is saying the idea of data centers in space is impossible. It's obviously very possible. But it doesn't make even the slightest bit of economic sense. Everything gets way, way harder and there's no upside.
> No, we just "assume" (i.e. know) that radiation in a vacuum is a really bad way of dissipating heat, to the point that we use vacuum as a very effective insulator on earth.
In space or vacuum radiation is the best way to dissipate heat, since it's the only way.
I believe the reason the common person assumes thermal radiation is a very poor way of shedding heat is because of 2 factoids commonly known:
1. People think they know how a vacuum flask / dewar works.
2. People understand that in earthly conditions (inside a building, or under our atmosphere) thermal radiation is insignificant compared to conduction and convection.
But they don't take into account that:
1) Vacuum flasks / dewars use a vacuum for thermal insulation. Yes and they mirror the glass (emissivity nearer to ~0) precisely because thermal radiation would occur otherwise. They try their best to eliminate thermal radiation, a system optimized to eliminate thermal radiation is not a great example of how to effectively use thermal radiation to conduct heat. The thermal radiation panels would be optimized for emissivity 1, the opposite of whats inside the vacuum flask.
2) In a building or under an atmosphere a room temperature object is in fact shedding heat very quickly by thermal radiation, but so are the walls and other room temperature objects around you, they are reheating you with their thermal radiation. The net effect is small, in these earthly conditions, but in a satellite the temperature of the environment faced by the radiating surfaces is 4K, not a temperature similar to the object you are trying to keep cool.
People take the small net effect of thermal radiation in rooms etc, and the slow heat conduction through a vacuum flasks walls as representative for thermal radiation panels facing cold empty space, which is the mistake.
Well no, it’s because conduction/convection into a fluid is so much more effective.
Just look at a car. Maybe half a square meter of “radiator” is enough to dissipate hundreds of kW of heat, because it can dump it into a convenient mass of fluid. That’s way more heat than the ISS’s radiators handle, and three orders of magnitude less area.
Or do a simple experiment at home. Light a match. Hold your finger near it. Then put your finger in the flame. How much faster did the heat transfer when you made contact? Enough to go from feeling mildly warm to causing injury.
but thats what you don't get: conduction / convection on the ground is ultimately still radiation to space: you heat up our rivers, soils, atmosphere and the heat is eventually shed... by thermal radiation.
its not exactly good advertisement for conductive or convective heat transfer if its really employing thermal radiation under the hood!
but do you want big tech to shit where you eat? or do you want them to go to the bathroom upstairs?
At some point I'm thinking the large resistance to the idea I am seeing in a forum populated with programmers is the salivation-inducing idea that all that datacenter hardware will eventually get sold for less and less, but if we launch them to space there won't be any cheap devalued datacenter hardware to put in their man-caves.
Additional radiator area means bigger spacecraft, implies more challenge with attitude control. Lower down you get more drag so you use propellant to keep yourself up, higher up you have more debris and the large area means you need to frequently manoeuvre to avoid collisions. Making things bigger in space is not trivial! You can't just deploy arbitrarily large panels and expect everything to be fine.
heavier boats are also slower to accelerate or decelerate compared to smaller boats, does this mean we should ban container ships? having special orbits for megastructure lanes would seem a reasonable approach.
The radiators would be lighter compared to the solar panels, and slightly smaller surface area so you can line them back to back
I don't think dissipating heat would be an issue at all. The cost of launch I think is the main bottleneck, but cooling would just be a small overhead on the cost of energy. Not a fundamental problem.
If you solved this problem apply at nasa because they still haven't figured it out.
Either that or your talking out of your ass.
FYI a single modern rack consumes twice the energy of the entire ISS, in a much much much much smaller package and you'll need thousands of them. You'd need 500-1000 sqm of radiator per rack and that alone would weight several tonnes...
You'll also have to actively cool down your gigantic solar panel array
eldenring is slightly wrong: for reasonable temperatures the area of the radiating panels would have to be a bit more than 3 times the area of the solar panel, otherwise theres nothing wrong.
No need to apply at NASA, to the contrary, if you don't believe in Stefan Boltzmann law, feel free to apply for a Nobel prize with your favorite crank theory in physics.
Whats your definition for reasonable temp? my envelope math tells me at 82 celsius (right before h100s start to throttle) you'd need about 1.5x the surface area for radiators. Not exactly back to back, but even 3x surface area is reasonable.
Also this assumes a flat surface on both sides. Another commenter in this thread brought up a pyramid shape which could work.
Finally, these gpus are design for earth data centers where power is limited and heat sinks are abundant. In the case of space data centers you can imagine we get better radiators or silicon that runs hotter. Crypto miners often run asics very hot.
I just don't understand why every time this topic is brought up, everyone on HN wants to die on the hill that cooling is not possible. It is?? the primary issue if you do the math is clearly the cost of launch.
I am the person who gave the pyramid shape as a didactic example (convexity means we can ignore self obscuration, and giving up 2 of the 4 triangular side surfaces of the pyramid allows me to ignore the presence of lukewarm earth).
My example is optimized not for minimal radiator surface area, but for minimal mathematical and physical knowledge required to understand feasibility.
Your numbers are different because you chose 82 C (355 K) instead of my 26 C (300 K).
Near normal operating temperatures hardware lifetime roughly doubles for every 10 deg C/K decrease in temperature (this does not hold indefinitely of course).
You still need to move the heat from the GPU to the radiator so my example of 26 deg C at the radiator just leaves a lot of room against criticism ;)
Who’s saying cooling is not possible? Cooling gets brought up because it’s presented as an advantage of putting stuff in space. But it’s not an advantage, cooling is harder in space than on the ground.
The distinction is that you don't need to compete for land area, that you don't cause local environmental damage by heating say a river or a lake, that you don't compete with meatbags for energy and heat dissipation rights.
Without eventually moving compute to space we are going to have compute infringe on the space, energy, heat dissipation rights of meatbags. Why welcome that?!?
> How efficient is thermal radiation through a vacuum again?
I provided the calculation for the pyramidal shape: if the base of a pyramid were a square solar panel with side length L, then for a target temperature of 300K (a typical back of envelope substitute for "room temperature") the height of the pyramid would have to be about 3 times the side length of the square base. Quite reasonable.
> Sure, it occurs, but what does the Stefan–Boltzmann law tell us about GPU clusters in space?
The Stefan-Boltzmann law tells us that whatever prevents us from putting GPU clusters in space, it's not the difficulty in shedding heat by thermal radiation that is supposedly stopping us.
Yes, you can overcome this with enough radiator area. Which costs money, and adds weight and space, which costs more money.
Nobody is saying the idea of data centers in space is impossible. It's obviously very possible. But it doesn't make even the slightest bit of economic sense. Everything gets way, way harder and there's no upside.