zlacker

>>g-mork+(OP)
Either this is a straight up con, or Musk found a glitch in physics. It's extremely difficult to keep things cold in space.

>>alangi+u6
what makes you believe this?

radiators can be made as long as desirable within the shade of the solar panels, hence the designer can pracitically set arbitrarily low temperatures above the background temperature of the universe.

>>Doctor+Ca
Radiators can shadow each other, so that puts some kind of limit on the size of the individual satellite (which limits the size of training run it can be used for, but I guess the goal for these is mostly inference anyway). More seriously, heat conduction is an issue: If the radiator is too long, heat won't get from its base to its tip fast enough. Using fluid is possible, but adds another system that can fail. If nothing else, increasing the size of the radiator means more mass that needs to be launched into space.

>>c1cccc+Rd
please check my didactic example here: >>46862869

"Radiators can shadow each other," this is precisely why I chose a convex shape, that was not an accident, I chose a pyramid just because its obvious that the 4 triangular sides can be kept in the shade with respect to the sun, and their area can be made arbitrarily large by increasing the height of the pyramid for a constant base. A convex shape guarantees that no part of the surface can appear in the hemispherical view of any other part of the surface.

The only size limit is technological / economical.

In practice h = 3xL where L was the square base side length, suffices to keep the temperature below 300K.

If heat conduction can't be managed with thermosiphons / heat pipes / cooling loops on the satellite, why would it be possible on earth? Think of a small scale satellite with pyramidal sats roughly h = 3L, but L could be much smaller, do you actually see any issue with heat conduction? scaling up just means placing more of the small pyramidal sats.

>>Doctor+JO
Kudos for giving a concrete example, but the square-cube law means that scaling area A results in A^(3/2) scaling for the mass of material used and also launch costs. If you make the pyramid hollow to avoid this, you're back to having to worry about heat conduction. You assumed an infinite thermal conductivity for your pyramid material, a good approximation if it's solid aluminum, but that's going to be very expensive (mainly in launch costs).

In reality, probably radiator designs would rely on fluid cooling to move heat all the way along the radiator, rather than thermal conduction. This prevents the above problem. The issue there is that we now need to design this system with its pipes and pumps in such a way that it can run reliably for years with zero maintenance. Doable? Yes. Easy or cheap? No. The reason cooling on Earth is easier is that we can transfer heat to air / water instead of having to radiate it away ourselves. Doing this basically allows us to use the entire surface of the planet as our radiator. But this is not an option in space, where we need to supply the radiator ourselves.

In terms of scaling by instead making many very small sats, I agree that this will scale well from a cooling perspective as long as you keep them far enough apart from each other. This is not as great from the perspective of many things we actually want to use a compute cluster for, which require high-bandwidth communication between GPUs.

In any case, another very big problem is the fact that space has a lot of ionizing radiation in it, which means we also have to add a lot of radiation shielding too.

Keep in mind that the on-the-ground alternative that all this extra fooling around has to compete with is just using more solar panels and making some batteries.