Solar Power Satellites

> From: Dave Handwerk
>
> > We could slowly rotate the entire STEG, ISRCCs and
> > all. It would also probably require rotating the
> > entire SSPS, and having a method detached from the
> > SSPS to steer the Microwave beam?
--- "Combs, Mike" wrote:
>
> It's a tempting idea, but the problem with rotating
> the SSPS is that you
> will then have gyroscopic forces which will make it
> difficult to steer
> the array. And solar-concentrating SPS have more
> rigorous pointing
> requirements than do flat PV arrays.
>
> Regards,
>
> Mike Combs
>
Hi Mike,

The gee forces to collect the condensed coolant should
be around 1/200th gee, and to change the axis of
rotation to continuously point at the sun, requires a
small force perpendicular to both the spin axis and
the direction you want it to turn to. The small Xenon
Ion thrusters used for station keeping would easily
handle it.

Pointing is more vigorous, but that very gyroscopic
effect will keep it pointed at the sun, unless we
apply the above mentioned force. The pointing vector
only has to move about 1 degree per day.

OK it will be more complex (needs more control
electronics) but let me list the Pros:
1. efficiency 2 to 4 times that of solar cells.
(which lowers the size needed and hence the cost)
2. about half the cost per watt collected (assuming
the stuff in made on earth)
3. about 1/4 to 1/10th the mass (which lowers the
launch cost)
4. I'm not sure about the poly-amide or polyacetate
films, but the Diamond Thermionic converters are
supposed to last well over 30 years in the high
radiation area of GEO, while solar cell will degrade
about 10% per year.
5. It may be possible combine the STEG with the
microwave amplifier, increasing efficiency, etc...

I think Solar (Diamond) Thermionic Electric (Power)
Generators (STEGs) are a superior method for the Space
Solar Power Satellite (SSPS) industry. At least in
its infancy - while we have to shoot it all up there.

Maybe later when we have Silicon from the moon as a
by-product of something else, the situation may
change?

regards,

Dave Handwerk