Thermal Generator

[MiketheEngineer]

Old Structural here who has forgotten just about all the Thermodynamics I ever knew.

We know that the "sunny" side of a spacecraft can experience temps in the +250F range while the "dark" side is at about -250F.

Why couldn't some type of fluid be boiled on the "hot" side, run through a turbine/generator and condensed on the "cold" side??

For reasons I don't completely understand why not or otherwise NASA probably would have already done it.

Any help out there telling me why?

 

[MintJulep]

As a first guess I'd say because photovoltaic panels are better for the application.

No moving parts. No fluid to leak. No maintenance needed.

 

[IRstuff]

> It could, possibly, but the boiling and mass transfer affects the momentum of the satellite, and for many applications, such wobbling is unacceptable.
> The usual issue is not the incoming thermal, but the internally generated thermal, which must be removed through radiation.
> Carrying a non-functional fluid into orbit is every expensive, and a thorough cost-benefit analysis probably rules it out.

TTFN
faq731-376

 

[Terminus0]

It would be easy to gain heat of the hot side, but difficult to reject heat out the cold side.

Spacecraft despite what science fiction says about space being cold actually have immense problems with shedding heat because it can only be done through radiation (There is no air to convect to).

To create your system you'd need comparatively immense fins on the dark side to get rid of the heat that has been added to the spacecraft. Frankly it just wouldn't be worth it. Most space craft design involves trying to avoid gaining as little heat from the outside as possible which is why space craft are so shiny.