Generating power in space.

[Damien Huxley]

Hi guys, I have a question about generating power in space. On earth in many places we use thermal power plants, why aren't we using them in space?

A satellites typical range of temperatures was found to be from -170 ˚C to 123 ˚C for LEO satellites while -250 ˚C to 300 ˚C could be experienced in other orbits.

A spinning hourglass with refrigerant gas would be heated and cooled as it rotated around, at a turbine into the middle of it and you have a power source, add multiple hourglasses and control the speed of rotation to optimise heating and cooling.

I gather it depends on the radiant heat loss as space is a good insulator and the performance compared to solar?

Regards
Damien

[holmes4]

We do use thermoelectric power in space craft when solar won't do the job. Check out Voyager I and II.

Mark

[cjameshuff]

The parts of a satellite that are cold are so because they're not radiating much heat. You could run a heat engine off the temperature difference, but you won't get much power out before you've pretty much equalized the temperature across the spacecraft.

Concentrated solar thermal power has been considered, but the simplicity of photovoltaic panels has generally won out.

[Solfe]

A mechanic device would wear out faster than a solar panel. Plus you would have heat rejection issues. It would also introduce yet another liquid to the spacecraft's systems make it more complex. The ship would have to anticipate motion in that liquid to stay on the correct course or not rotate. It's all one more moving part.

An electromechanical device would probably be more suited for the ISS, but then you have the issue of noise and vibration. The ISS is loud already.

[Van Rijn]

I gather it depends on the radiant heat loss as space is a good insulator and the performance compared to solar?

Welcome to the board, Damien. With solar, mostly it has to do with mass, simplicity and reliability. In the very early days there were ideas about thermal solar and you'll see this on '50s spacecraft concepts, but PV was lighter and more robust when needed in the '60s. PV has improved by leaps and bounds, in the '60s there was limited efficiency but now it's easy to roll out thin, large, highly efficient (more efficient than lower cost commercial panels) panels for spacecraft. Sometimes these panels are huge, like on Juno, which doesn't get as much sunlight out at Jupiter.

As holmes4 mentioned, there is an exception - radio thermal generators or RTGs. Usually these have no moving parts, but there is a newer type called the ASRG that uses a sterling engine and provides more power for the same mass due to higher conversion efficiency. See:

https://en.wikipedia.org/wiki/Advanc...tope_generator

RTGs are on the missions to the outer solar system and on the Curiousity and Mars 2020 rovers. The big limitation for their use is the amount of available PU238.

One other item you'd mostly see with some old Soviet satellites would be full nuclear reactors. These have been used (and will be again) where a lot of power is needed, and these use a thermal generator as well.

And for chemical energy production, again safety and simplicity are the priority, so there have been fuel cells and batteries, not using a heat engine scheme.

[Damien Huxley]

Thanks �� great answers

[Marsdmitri]

a terrible huge weight and unreliability.
Would you see on the construction of Soviet Lunohod-1? https://en.wikipedia.org/wiki/Lunokhod_1 please.
It worked on the Moon 50 years ago.
It used 2 source of energy: quantum solar cell for moving for electric engines for 12 wheels and nuclear RTG for heating inside at the night (https://en.wikipedia.org/wiki/Radioi...tric_generator). It is hybrid. It is standard. Any other devices used the same construction or a part of it.