Re: Space elevator - cut this thread, please?

[Martin Schweiger <martins@xxxxxxxxxxxxxxxxx>]

> i was trying to convince others that the elevator is realistic because i
> really want them to take an interest to help me build such a model in the
> sim :)

Sorry for posting to the same topic after it's been closed
by the moderator, but I should point out that a space elevator,
whether physically possible or not, currently *can't* be
simulated in orbiter. Orbiter uses a rigid-body model for its
vessels, and assumes that a vessel is small enough so that
the gravity field is constant over its volume.

It would however be pretty simple to build a standalone finite
element model which would do the necessary calculations. It would
not even have to be real-time, so could be designed for high
accuracy. A simple linear elasticity FEM solver with 6 DOF
beam elements should do fine. You would use the gravity field
at each node as an external load, and the position of a fixed point
on the rotating Earth's
surface as a boundary condition. I don't know the material
properties of the elevator cable, but I suspect you would need
an anisotropic elasticity tensor. Since it's is a time-dependent
problem, you will probably end up having to solve a parabolic
PDE (but I could be wrong - I am just speculating)

If you don't want to develop the FEM solver yourself, there should
be loads of code out there, since this is a bread-and-butter type
of problem for mechanical engineers.

Let me know if you get results. I can't help feeling that the
solutions would be unstable, but I am prepared to be convinced
otherwise.

Martin


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