Re: Structure around the planet.

From: Ross A. Finlayson (raf@tiki-lounge.com)
Date: Wed Nov 29 2000 - 10:26:51 MST


hal@finney.org wrote:

> Ross writes:
> > Can tethers have a complete orbit? For example, from an orbit could a
> > satellite have a cable that reached all the way around the planet back to
> > itself? That might be a first stage about putting a structure around the
> > entire planet. If a couple cables were in orbit, they could generate
> > deionizing fields around the planet outside of it's magnetosphere.
>
> I think there are problems with stability in such a structure.
>
> I've read that if you had a *rigid* ring, it could not be in orbit.
> One side or the other would tend to drift downwards. It wouldn't make
> any difference if it were rotating or not. Of course this is only for
> an idealized, perfectly rigid ring, and no solid materials could be
> particularly rigid at the size scale we are talking about.
>
> For a flexible ring, I think the problem is that if the orbit is slightly
> elliptical, as any true orbit will be, the particles of the ring want to
> move faster during the lower part of the orbit. This will compress the
> ring in some portions and stretch it elsewhere. I suspect that this
> energy transfer will cause the ring to become deformed and to collapse
> into the atmosphere eventually.
>
> You could possibly fix these problems with active elements, little rockets
> or perhaps solar mirrors to monitor the position of each ring element
> and herd it back into the desired configuration. But this would add
> greatly to the complexity of an already difficult project. 25000 miles
> of cable of any practical thickness is going to be a mighty big spool.
>
> Also I'm skeptical of this "deionizing fields" concept, because a cable
> moving parallel to it own length won't cut any magnetic field lines and
> so won't generate any significant currents.
>
> Hal

That's why there would be two. If one is in orbit and the the other one floats
over and beneath the poles, I thought that would have to do with field. If a
field could be established, then it could deionize incoming solar mass, for
example. So one equatorial and the other polar. If that worked, you could make
more.

If there are ways to store and reuse kinetic energy, then torsion could be
smoothed out of the flexible orbital ring. Maybe it could be magnetically
connected at joints.

Maybe it is better to try it on other planets and planetoids, extraterrestrial
construction.

Ross

--
Ross Andrew Finlayson
Finlayson Consulting
Ross at Tiki-Lounge: http://www.tiki-lounge.com/~raf/



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