Full G on the Moon or other small bodies?

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of wlm_efn

> If humans need a full one Earth gravity after all, a lunar
> settlement could provide that, at least part of the time.
> Build a circular track on the surface, with a radius of 1 km.
> and tilted.
> Then have cars travel around the track at the appropriate
> speed, and one has full Earth gravity on the Moon.

I had to smile when I saw this posting, because over on the
sci.space.policy newsgroup I got into a lengthy debate with someone who
took issue with my point that in an orbital habitat we could have any
level of "gravity" required, whereas on the lunar surface we had to live
with 1/6 gravity. He basically proposed a Stanford Torus for the moon.
I pointed out that such a massive centrifuge would require a huge,
strong bearing, which he angrily denied. There would be no need for a
bearing; it would be designed like a maglev. I told him this only meant
that he was assuming magnetic bearings, but that they were still
required, and were an additional engineering complexity not required in
the orbital case.

For myself, I can see an exercise room or even a small gymnasium built
in this manner. I would expect it to stop to take on passengers. I can
see people scheduled for a return to Earth being encouraged to use it
regularly. But this guy was asserting that something on the scale of a
Stanford Torus could easily be built in this manner on the lunar
surface. I just couldn't see a city of 10,000 built on the principle of
a steeply-banking maglev train.

At the time of the argument I had a concern about lift failure. But
perhaps one could design a massively-parallel system such that complete
failures were nearly impossible. Someone (either on this maillist or
the SSI one) proposed permanent magnets in place of this guy's
electromagnets. That would improve reliability.

> There will be no atmospheric drag, so no energy is required
> to keep the cars going due to this.

There would still be the drag due to the aforementioned bearings,
whether we're talking the friction of physical bearings, or the eddy
current resistive losses of magnetic bearings. But I would certainly
agree that a lunar system would be more practical than one for Mars.

Regards,

Mike Combs