Russell McMahon <apptech@PARADISE.NET.NZ> wrote:
> Geosynchronous orbit is at about 22,236 miles.

Yes.

> A space elevator that is earth anchored must reach at least that far and
> in practice somewhat more.

Actually quite a lot more. The 22k mile cable itself is by far the heaviest
part of such a system. Its center of mass must be at the 22K mile orbit,
and the simplest and most cost-effective way to do this is to make it
44.472K miles long.

> Earth circumference is about 24,000 miles. If you cut the elevator below
> its anchor point it will fall.

What "anchor point"? Are you imagining some sort of massive object (many
times more massive than the cable itself) in the geosynchronous orbit?

> Such an elevator is the ultimate logical target for terrorists. A small
> nuke somewhere near the top is liable to be enough. Stopping anyone
> getting one there could be an interesting task if large amounts of
> freight and people are travelling up it constantly (as they would have
> to be).

I think such an elevator is most vulnerable at the bottom, where it is
attached to the earth anchor. There's just enough tension at this point to
make the cable stiff enough to use and to provide a margin for any minor
orbital anomalies. If it gets separated at that point, the whole system
will just slowly drift away.

Protecting the rest of the cable shouldn't be all that difficult. The
cargo containers can be held at some distance from the cable itself,
and energy-absorbing/deflecting shielding materials can be placed in
between.

-- Dave Tweed

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics