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Re: starship-design: just a note..

In a message dated 6/12/97 3:58:21 PM, stevev@efn.org (Steve VanDevender)

>Bakelaar writes:
> > ok, first, do you guys remember in gardens of paradise or whatever
> > that book was called, arthur c. clarke made up that space elevator
> > with that string that made it easy to get stuff up into space.. (yea
> > thats a pretty bad description but i cant remember it :D).. well 
> > anyway in popsci they mention that scientists have created some type
> > of carbon filament that can withstand the atmospheric pressure put on
> > itself when suspended from orbit.. theres so much speculation and 
> > guesswork in this group, i figgered we needed a little solid fact :)
>The main technical difficulty with a skyhook is not atmospheric pressure
>but finding a material with sufficient tensile strength.  The skyhook is
>actually a cable in geosynchronous orbit with one end touching the
>ground.  This requires that it be able to withstand the enormous tidal
>differential between the ends, resulting in tremendous tension (not
>compression!) on the cable.  Other problems include anchoring the ground
>end and fabricating a cable that long (as much as 46,000 miles for a
>uniform cable; less if you use a counterweight on the far end) and
>dealing with small but significant changes in the rotation speed of the
>Earth (perhaps a movable counterweight?).
>The concept of a skyhook had been worked on for quite a while before
>Clarke wrote _The Fountains of Paradise_.

The idea also has serious construction and maintenence cost issues and
tremendous safty issues.  All in all I'm not sure it would be cost
competative with the high efficency launchers that would need to be in
operation before anyone could attempt to build it.