how critical is passive stability?

I think you'll find that with the below design, air drag will create a significant problem. The peer-reviewed studies sometimes looked at separate, stationary slag shields, and I've elsewhere seen it proposed that a stationary outer structure take up some portion of the load bearing, but the assumption is always that there's a vacuum between the rotating inner structure and the stationary outer structure.

Regards,
is a complete, closed system. I have proposed encasing
the rotating portion within a passive, non rotating,
outer slag cylinder, that could itself be capped and
act as a pressurized enclosure for the rotating "life
enclosure". The end caps could then be an inverted
geodesic structure of Borosylicate glass, very tough
and radiation resistant triangular "plugs" of glass,
3m wide by 3m long by three meters thick, inserted
into a geodesic framework made of aluminum.
Penetration of any single glass plug would result in
an insignificant air loss until it could be replaced.
Larger penetrants, those pieces of space debris large
enough to cause damage to sections of the geodesic
larger than 1 plug, could be detectable by radar and
vaporized or at least broken up with small lasers.
Ablation of the outer layers of the rocks should be
sufficient to deflect the debris and avoid impact with
our glass endcaps.

The rotating inner cylinder could ride on magnetic
bearings within the passive shell, transferring load
to that shell and reducing the inner cylinder load
considerably. The passive shell then provides
radiation protection, acts as an air containment
vessel and load containment structure, plus any micro
g environmental requirements could be constrained
within that shell, even to the growth of air recycling
plants, which as far as I know can be grown in the
absence of gravity. Additional plant/animal life could
be grown within the rotating cylinder as required. As
long as the cylinders come as a counter rotating pair,
there would be no energy transfer to the shell and the
life cylinders would be rotationally stable at
Length =