The cost of replacement is exorbitant for commercial usecases, but is acceptable for defense usecases.
The issue is too many people are looking at the commercial usecase while ignoring the defense usecase that is what is actually driving the conversation and dealflow in this segment.
First, it assumes the radiator is at the same temperature as the GPU. But radiators become dramatically more effective as temperature increases, with radiated power increasing as the fourth power of absolute temperature. So a heat pump that drives the radiator at higher temperature could make the radiator far smaller. More power would be required (and the radiator would have to radiate this energy too) but the radiator could become much smaller.
The other problem is assuming the radiator is intercepting sunlight. But it can be shaded by reflective films or kept edge-on to the Sun.
> Ok, there are at least two bad assumptions there.
> First, it assumes the radiator is at the same temperature as the GPU. But radiators become dramatically more effective as temperature increases, with radiated power increasing as the fourth power of absolute temperature. So a heat pump that drives the radiator at higher temperature could make the radiator far smaller.
Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C. So small radiator = big pump + extra solar panels and batteries + dead GPU
Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?
> Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C.
Sorry, that's all nonsense. Yes, the extra power needs to be radiated. But the advantage of operating at high temperature is so extreme that the more effective radiation will overwhelm that unless the heat pump is extraordinarily inefficient. If the heat pump would be perfect, operating at the Carnot limit, then if it doubled the absolute radiator temperature it would double the amount of energy to be radiated, but the area of the radiator would decrease by a factor of (2^4)/(2) = 8.
As for the second point, no, this does not require the GPU to operate at higher temperature. What made you conclude it would?
> Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?
I don't need to; I'm just debunking a bad argument. What you are doing there is called "moving the goalposts". But satellites normally have means of orienting PV toward the Sun. So, maybe have the radiator perpendicular to those? Those claiming the idea violates the laws of physics and using solar absoption on the radiator as part of the argument need to show no such scheme can work, even in principle.
OP is quoting Mikhail Klassen at Planet Labs [0].
The cost of replacement is exorbitant for commercial usecases, but is acceptable for defense usecases.
The issue is too many people are looking at the commercial usecase while ignoring the defense usecase that is what is actually driving the conversation and dealflow in this segment.
[0] - https://www.mikhailklassen.com/posts/orbital-data-centers/or...
Ok, there are at least two bad assumptions there.
First, it assumes the radiator is at the same temperature as the GPU. But radiators become dramatically more effective as temperature increases, with radiated power increasing as the fourth power of absolute temperature. So a heat pump that drives the radiator at higher temperature could make the radiator far smaller. More power would be required (and the radiator would have to radiate this energy too) but the radiator could become much smaller.
The other problem is assuming the radiator is intercepting sunlight. But it can be shaded by reflective films or kept edge-on to the Sun.
> Ok, there are at least two bad assumptions there.
> First, it assumes the radiator is at the same temperature as the GPU. But radiators become dramatically more effective as temperature increases, with radiated power increasing as the fourth power of absolute temperature. So a heat pump that drives the radiator at higher temperature could make the radiator far smaller.
Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C. So small radiator = big pump + extra solar panels and batteries + dead GPU
Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?
> Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C.
Sorry, that's all nonsense. Yes, the extra power needs to be radiated. But the advantage of operating at high temperature is so extreme that the more effective radiation will overwhelm that unless the heat pump is extraordinarily inefficient. If the heat pump would be perfect, operating at the Carnot limit, then if it doubled the absolute radiator temperature it would double the amount of energy to be radiated, but the area of the radiator would decrease by a factor of (2^4)/(2) = 8.
As for the second point, no, this does not require the GPU to operate at higher temperature. What made you conclude it would?
> Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?
I don't need to; I'm just debunking a bad argument. What you are doing there is called "moving the goalposts". But satellites normally have means of orienting PV toward the Sun. So, maybe have the radiator perpendicular to those? Those claiming the idea violates the laws of physics and using solar absoption on the radiator as part of the argument need to show no such scheme can work, even in principle.
Again,
Smaller radiator = bigger heat pump + more batteries and solar panels
Satellites have a mass and power budgets. Your scheme only looks at temperature. If you want to build infinitely large AI Data satellites, go ahead.
I encourage you to actually run the numbers before continuing to make a fool of yourself.
Also, budgets and such is beside the point when arguing against someone who makes a wrong claim about "the laws of physics".