Energy Generation in Space

Mitchell James wrote: I have always had a problem with turbines that I have never seen brought
up as a reason for not using them and that is that they are rotating
machinery. When one piece of a machine turns in space then the rest of
the machine has to turn in the opposite direction with the same
rotational energy. Now you could have a turbine pair that rotated in
opposite directions connected by a solid structure then as long as the
torques were equally matched the structure could remain stationary (a
long list of assumptions). (I really would like to see somebody do this
while generating electricity under varying load.) No machine runs
forever. It is just a question of how it is going to fail. So a
bearing freezes on one of the turbines and all of the rotational energy
is quickly transfered to the structure. In my mind something turning
fast enough to generate a usable voltage is going to transfer enough
energy to do a good job of trashing the overall structure. This
structure is going to be designed for minimum weight not maximum strength.

One of the things that I have learned is that the customer's memory of
what happens in failure mode overrides what they remember when
everything is working correctly. To me the failure modes associated
with rotating machinery in space out weigh anything else.
Mitchell James

> There are two MAJOR problems that attend the use of
> turbines in hard vacuum and orbit.
> 1) They are machines with moving parts that must be
> lubricated and replaced on a regular basis. The
> failure rate of mechanical devices, regardless of
> environment, is easily 10,000 times more likely than
> the failure rate of solid state devices.
> 2)For a turbine to function, it must have a heat sink
> somewhere, which necessitates the building of a LARGE
> radiative surface to dump the residual heat of
> operation. No such requirement for the solor cells
> themselves, though the conversion to micro waves would
> have some residual waste heat, I doubt it would be as
> significant as that from a heat engine such as
> turbines.
>
> Gary 7

What if the turbines were mounted on the lunar surface? Let's say you had multiple turbines, working independently of each other to isolate any failures and allow for periodic maintenance. Transfer all reactions to the planet. Mechanical and rotary systems are all prone to failure and require maintenance, but we do have a long experience base with the technology, and a base on the Moon would allow tending of the machinery. Is this preferable to a more exotic technology?

Andy