Instability of long cylinders

Counter rotating cylinders DOES address the problem of
long cylinder instability and eliminates that problem
however,, my favorite design is the rotating pie pan
approach, with multiple levels that can take advantage
of lower acceleration levels for food growth, etc.
After all, plants don't seem to have a problem with
reduced acceleration effects and animals are going to
be sacrificed for food anyway, so their lack of strong
bones is inconsequential.

Gary 7

> From time to time on these maillists the subject has
> come up that
> spheres and tori might be better shapes for habitats
> than long cylinders
> because of the latter's tendency to eventually
> tumble end-for-end.
> While on the newsgroup rec.arts.sf.science somebody
> was talking about
> the ultimate size for space habitats given current
> materials, and I was
> mentioning the dimensions of Island 3. This
> prompted James A. Donald to
> say:
> "Island 3 is not practical. Being longer than it is
> wide, will be unstable. Will flip over, killing
> everyone inside."
>
> To which I responded:
>
> "Eh, you're referring to a real-life aspect of
> physics, but needlessly
> hyperbolizing it. It's more like if civilization
> fell in an O'Neill
> cylinder, and the stabilization systems failed, and
> if you went away and
>
> came back after a few decades, it would be tumbling
> end-for-end rather
> than
> on its long axis.
>
> "Frankly, I consider the mirror design of Island 3
> to come closer to
> making
> it impractical than the simple fact that it's longer
> than it is wide.
>
> "But the point relevant to Knobby's point was that
> cylinders 4 miles in
> diameter are possible with present materials."
>
> He came back to say that "It would tumbling be end
> for end in about ten
> minutes or half an hour" and further went on to say
> that an above-ground
> swimming pool breaking and dumping its water would
> be sufficient to
> destabilize the cylinder.
>
> So what say you guys? A problem if the automatic
> stabilization system
> remains off-line for weeks or months, or a
> catastrophic flip within the
> hour, killing millions?
>
> But ultimately, it occurs that my very first
> response should have been
> that an O'Neill Cylinder(s) habitat would actually
> have 0 net angular
> momentum because it's actually two counter-rotating
> cylinders. In The
> High Frontier, O'Neill only mentioned this as a
> solution to the problem
> of turning the axis of the habitat so as to track
> the sun, but could it
> be that this design solution was also proposed for
> the second reason of
> the instability of long cylinders?
>
> Regards,
>
> Mike Combs
>

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