clipka <ano### [at] anonymousorg> wrote:

>
> If free-fall without air resistance is what you want to model, you
> should use a /single/ rotation about an arbitrary axis.
>
> This is because without external forces, angular momentum is conserved,
> i.e. the axis of rotation doesn't change.

So an analogy would be a chicken on a spit, roasting over an open fire while the
single rod is rotated? (I must be hungry at the moment...)

If we're on the same wavelength, that goes against what I *think* my eyes see
when, for example, the ISS astronauts have some playful fun by spinning
weightless objects for the camera. It looks like two-axis (POV-Ray) rotation to
me. But that's only my recollection; I need to take another look at some of
those videos. (BTW-- 2001:A SPACE ODYSSEY recently celebrated its 50th
anniversary, and there are some space shots that have asteroids tumbling near
the Discovery. I always thought they looked a bit fake-- because they are
spinning around only one axis. Granted, Stanley Kubrick spared no expense in
getting scientific details right; but my opinion is that the spinning of the
asteroids (as special-effects models) had to be constrained, simply as a
practical matter for filming. A chicken on a spit, in other words.)
>
>
> A rotation about a third axis adds yet another layer of complexity,
> turning the precessing motion into a tumbling motion. This should be the
> closest to realism at least for highly asymmetric objects.

To me, the 3-axis rotation looks not so much like tumbling, but rather like the
object has a 'shifting mass' inside it, kind of sloshing around. It's the
'changing/reversing' of directions that seems odd. (Multiple precessions?) Yet,
it DOES appear to be a good stand-in for chaotic air-resistance.

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