Instability of long cylinders

If the earth were the only gravitational influence, you are correct.

However, step outside the box for a moment and let's look at other
forces.

The moon generates a tide on earth. Certainly, there is a force on the
space station no matter where you put it.

The sun generates a gravitational force. However, it also generates a
particle force (solar wind, CME events).

Pretty much everything else is either too small to have an effect ( 1
part in a million) or is event based such as asteroids, comets, space
garbage.

So, I'm going to guess that the earth moon interaction has a lot to do
with stability, and that the sun plays a major role with radiation
pressure of all sorts, as well as a gravitational source.

David

--- In ssi_list@... GARY ANSORGE
>
> Precession depends upon the application of a force at
> right angles to the direction of rotation. On Earth,
> this force is gravity. Since the gyro/torus is in free
> fall, this force is negligible, therefore there should
> be no substantive precession.
>
> Gary 7
>
> > I think the torus design has precesion issues. Think
> > of it as a slow top.
> >
> > The way around this was highlighted in Kubrick's
> > movie
> > of Clarke's 2001 book. Two parallel torus connect by
> > a
> > common shaft.
> >
> > Another variation on the torus was the Baseball
> > Design
> > of Star Trek: Deep Space Nine.
> >
> > David
> >
> > > Maybe it is better to go with an inherently stable
> > > design, such as a torus.
> > >
> > > Ed
> > >
> > > > Systems are rather interesting...we can classify
> > > > them in a number of
> > > > ways.
> > > >
> > > > COmpletely passive, reinforced,
> > passive-reactive,
> > > > active-reactive.
> > > >
> > > > For space, passive would be the basic structure.
> > > > Reinforced would
> > > > allow a structure to bend with the environment
> > > > without tearing itself
> > > > apart through twisting or resonance.
> > > >
> > > > Passive-reactive is where aerodynamic forces
> > > (space
> > > > dynamic in our
> > > > case) are reacted to by a dynamic system.
> > However,
> > > > it may be one shot
> > > > or reusable.
> > > >
> > > > Active-reactive would include systems where
> > weight
> > > > in the form of
> > > > solids, liquids and gases are moved about in
> > such
> > > a
> > > > way to maintain
> > > > control. Damping out of mass movements either at
> > > the
> > > > object level or
> > > > within the object (creep, center of mass,
> > surface
> > > > transitions, etc.)
> > > >
> > > > Structures in space have no foundation - no
> > earth
> > > -
> > > > to help dampen or
> > > > control external or internal forces. In space,
> > > there
> > > > is weather mostly
> > > > from the sun that must be dealth with
> > constantly.
> > > >
> > > > An active-reactive system can be very expensive.
> > > > However, engineers
> > > > try to reduce the active to a passive problem.
> > > >
> > > > The biggest worries in space for a long cylinder
> > > are
> > > > resonance waves
> > > > where small forces generate end to end waves
> > that
> > > > buildup and
> > > > overwhelm any system. Torquing is also a major
> > > > worry.
> > > >
> > > > The way to make the long cylinder to work is an
> > > > exoskeleton bracing
> > > > such that the thickness of the "skin" is at
> > least
> > > 2%
> > > > of the diameter.
> > > > For 5 miles diameter, this would be 0.1 or 500
> > > feet
> > > > of structure
> > > > although with a buckyball (see your soccerball)
> > > > technique, that might
> > > > be reduced to 50 feet or so.
> > > >
> > > > David
> > > >
> > > >
> > > > --- In ssi_list@... Ed Minchau
> > > > >
> > > > > These towers would act much like the spokes of
> > a
> > > > > wheel-shaped station, and might be a good idea
> > > for
> > > > > structural and aesthetic reasons. However,
> > for
> > > > > rotational stability (and indeed, any critical
> > > > > systems) one would want things to be inherent
> > in
> > > > the
> > > > > design. Critical systems that are active
> > rather
> > > > than
> > > > > passive would be very vulnerable and also lead
> > > to
> > > > the
> > > > > possibility of a "chain reaction" failure,
> > where
> > > > one
> > > > > system going down leads to another going down
> > > and
> > > > so
> > > > > forth.
> > > > >
> > > > > Ed
> > > > >
> > > > > --- ForDutyAndHumanity IAmSpacebearAICDA
> > > > >
> > > > > > How about an active system to keep the
> > > cylinder
> > > > > > stable.
> > > > > >
> > > > > > I know that what everyone loves about the
> > > O'Neal
> > > > > > cylinder is the large spacious feeling. But
> > it
> > > > would
> > > > > > add to the strength of the structure and
> > > permit
> > > > > > active stablization of the cylinder by
> > bulding
> > > > large
> > > > > > skyscrapers/building which are the internal
> > > > diameter
> > > > > > of the cylinder.
> > > > > > People could live and work in these
> > buildings.
> > > > > > elevators would provide easy transport from
> > > one
> > > > side
> > > > > > or the other. But the active stablizing
> > system
> > > > could
> > > > > > be ,lakes at the base of each building,
> > pumps
> > > > could
> > > > > > pump the water up to the weightless center
> > of
> > > > the
> > > > > > building. It would work the same way as
> > when
> > > > ice
> > > > > > skater pull in their arms to spin faster.
> > > > > >
> > > > > > You could wire the whole cylinder with
> > stress
> > > > and
> > > > > > acceration sensors to provide the
> > information
> > > > for
> > > > > > how the pumps would work.
> > > > > >
> > > > > > So these building or even a cross structure
> > > > would
> > > > > > provide added strength to the cylinder,
> > places
> > > > to
> > > > > > live and an active stabilty system. Plus
> > > > tourist
> > > > > > would love the microgravity living in the
> > > middle
> > > > of
> > > > > > these buildings.
> > > > > > BestRegards,
> > > > > > Pete
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > > Be smarter than spam. See how smart
> > > > SpamGuard is at giving
> > > at
> >
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