Pat Flannery writes:
Then you've got the docking problem; you need a de-spun docking port, you
have to stop the spinning when you want to dock, or you do the 2001 trick
and spin your spacecraft up to the same rotational speed as the module.

I'd go with the 2001 trick, but rather than a slot, I'd go with a conical
docking adapter with axial symmetry at the centerline front of the main
spacecraft. Doesn't present any special problem for docking.

You could put a de-spun section on one end of the module and use that to
hold the docking collar, solar arrays, and communication antennas (this is
done on

Nah. Spin the whole thing. If you're using solar arrays, arrange them in
cylindrical shells around the craft with mirrors to direct sunlight into them
as the craft rotates.

a lot of communications satellites where the cylindrical solar-cell-covered
body spins for stability, while the antennas remained pointing at Earth),
but now you are spinning a large diameter airtight seal between the two
sections, and that's going to be difficult to design from both a air leakage
and no torque transference point of view.

For comms, send out a non-spinning co-orbital satellite module that can use
standard wi-fi techniques for comms between the main craft and itself but
since it's not spinning it can have the high gain dishes and be able to
carefully align them back to Earth w/o fancy mechanics to keep it pointed
properly on a spinning spacecraft.

Also provides some failure isolation from the main ship and if you co-orbit a
couple of them, some failure redundancy as well....

To keep the centrifuge in balance you could use a vibration sensor that
detects it being off-balance and transfers some sort of fluid from one side
to the other to balance it out. Another concept would be to not directly
attach the centrifuge proper to the module at its axis points, so that
vibrations can't be transferred from one to the other; it could either spin
on a air bearing at either end like a lot of gyroscopes do, or use a
magnetic field to do the same thing. I'm really surprised they had such
trouble with the ISS centrifuge module, as this doesn't sound like a
insurmountable problem to address in its design.

Not me. I've always considered a spinning centrifuge inside a spacecraft to be
a major mechanical headache/nightmare. You don't want *that* gyro seizing up
on you. No way....

One oddball problem would be that the centrifuge would act like a gyro wheel
and try to rotate the station as it orbited around the Earth. Two
counter-spun sections to it might solve that problem by canceling out the
gyroscopic effects.

Yep. Seen that all over the place. The issue is addressed head on in the book
and movie 2010. In fact it is a major plot element for the first EVA team.

Dave