starship-design: just a note..

[Steve VanDevender <stevev@efn.org>]

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_.