Settlement/Pow sat./Space Elevator @ Geosynronous orbit

--- In spacesettlers@yahoogroups.com, "Xenophile"
wrote:
> --- In spacesettlers, "Ed Minchau" wrote:
>

> > SPS and/or space station handy, then put them in geocynch orbit
> > just ahead of or just behind the SE.
> >
> > Ed
>
> My understanding of SE is that you need a counter out beyond GEO.
> So, since you need something out there anyway, why not a
powersat? A
> beefed-up structure, as it will not be floating in microgravity.
> That will make it more massive, but that's good in this case. And
> you now have the electricity to run the SE and all the stuff
> associated with it.
>
> Xenophile (and perhaps the reason you need a habitat is to build
the
> SE, as well as the SPS)

If the counterweight is simply more ribbon material, then it can
extend well beyond GEO, perhaps up to 100000 km. A climber could
let go near the end and automatically be in Mars transit orbit.

An SPS or large rotating space station, in GEO but not fixed to the
elevator, would maintain a fixed position relative to the SE, so it
would be easy to reach from the space elevator. An SPS microwave
beam coming down from GEO would probably be safer (useable at higher
power with a larger margin of error) if the SPS is located some
distance away from the space elevator, say 20 to 30 km away (double
the amplitude of oscillation of the ribbon). A space station could
be located between the two, not directly connected to either SPS or
SE but easily accessible to either.

There is another reason I wouldn't attach an SPS or rotating space
station. If say a space station is attached to the ribbon at its
hub, then the hub must be pointing at the earth constantly; however
it would be rotating about that hub, and therefore the axis of
rotation would have to precess once per day. That would require a
constant external force applied to the hub, perpendicular to the
ribbon/axis of rotation. Even if that issue can be resolved
(without using lots of energy), the hub could not be directly
connected to the space station; it would have to be free to move to
avoid twisting the ribbon. On a large space station this would
present interesting engineering challenges and would represent an
unacceptable supply chain bottleneck. Better to simply orbit in GEO
a short distance from an SE, rotate in the plane of the earth's
orbit, and live with docking to a spinning hub a la 2001.

A solar power satellite would also have a rotation problem if
connected to an SE. The largest part of any SPS would be its
collectors; the equipment to convert the light energy into
electrical energy and eventually microwave energy represents only a
small part. The collectors will likely be no more than reflective
surfaces for the most part, which must track the sun to reflect
light to the light->electricity converters. If an SPS is fixed in
orientation with respect to earth, as it would have to be if it were
attached to a space elevator, then it could not track the sun.

Ed