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by typ 132 days ago
It makes sense to target a higher operating temperature, like 375K. At some point, the energy budget would reach an equilibrium. The Earth constantly absorbs solar energy and also dissipates the heat only by radiative cooling. But the equilibrium temperature of the Earth is still kind of cool.

I guess the trick lies in the operating temperature and the geometry of the satellites.
2 comments
golem14 132 days ago
Asking for a friend (who sucks at thermodynamics:) could you use a heat pump to cool down the cold end more and heat up the hot end much higher? Heat radiation works better the higher the temperature?
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typ 132 days ago
Not sure about the effectiveness of a heat pump in this use case.

>Heat radiation works better the higher the temperature?

The power output is proportional to T^4 according to the Stefan-Boltzmann law.

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golem14 131 days ago
https://www.mdpi.com/1996-1073/16/10/4010

40% isn't much in the grand scheme of things, but maybe they can reach higher reduction with more research/materials. Mass and power are pretty cheap for spaceX, so shipping more solar panels and a heap pump might not be a deal breaker.

Would e.g. a reduction of 90% in radiator area change the overall picture on the overall feasibility? I think not, it would still be ludicrous, but I'd be happy to be proven wrong.

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typ 131 days ago
The radiator area is probably not what they need to worry about that much as we thought. When the energy input comes from solar 100%, they just need to optimize the ratio of the sectional area facing the sun over the total surface area of the satellite. If the ratio is low enough, like a fin or cone shaped object, it will be harder to be hot.
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golem14 129 days ago
Are we not talking about radiating away the energy used to run the DC ? I assume the solar panels should face the sun, radiate leftover energy away, hopefully as little as possible as solar cells get more efficient.

The radiators are for dissipating the waste heat coming from the data center equipment. I'd agree they better not be pointed at the sun ;) In fact, the DC should probably hide behind the solar array to not pick up extra heat from the sun.

The radiators, also behind the solar array, will also be hot because of the DC waste heat being conducted there ;)

I probably completely misunderstood your point.

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mathw 132 days ago
It's a minor point but the Earth doesn't radiate all of that heat to equilibrium, that's why we have climate change.
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