Re: starship-design: Going Up? Space Elevator: Next Stop, Earth Orbit

[Steve VanDevender <stevev@efn.org>]

KellySt@aol.com writes:
 > In a message dated 1/2/01 7:36:51 PM, nlindber@u.washington.edu writes:
 > 
 > >Neat article.  It seems like the nanotubes are the thing.  A question
 > >though.  Since nanotubes are (as i recall) electricly conductive, do you
 > >think it likely that friction with the atmosphere at lowerlevels, and
 > >photoelectric charging in space would tend to induce currents in the
 > >cable?  It seems reasonable to me that the potential between one part of
 > >the cable and another could be quite high.  Comments?
 > >
 > >Nels
 > 
 > Very true.  It would be a spectacular lightnight rod, and could cause arcing
 > up to the orbit.

Either the skyhook cable's a conductor or it's not.  If it's a
conductor, then a potential difference between the ends of the skyhook
will just produce current flow along the cable, which will probably be
more of a problem at the anchor site than along the skyhook itself,
unless the current flow is so great that it results in resistive heating
of the cable to a dangerous level.  If it's an insulator, then you might
get arcing as potential differences build up, but that would happen
primarily in the atmosphere -- you don't get arcing in vacuum, although
charge buildup could be a problem for anything that comes in contact
with the cable.

Lightning rods don't work by attracting lightning; they actually prevent
lightning from happening by dissipating the potential difference
gradually via corona discharge off the lightning rod's tip.  If the
skyhook cable is an insulator, then studding it with lightning rods in
the atmosphere or running conductors along the part in the atmosphere
could help protect it.

I certainly don't remember seeing this issue discussed in the articles
I've seen about skyhooks, although they tended not to be deeply
technical, either.