I like the space elevator a whole lot. Imagine practically no
throw-away
mass vs when you do it with rockets, you're doing fine if you wind up
with 1% of the mass you started with. Further, if a booster fails, the
whole thing comes crashing down; vs, using an elevator, it simply stops.
Inconvenient, maybe, but I know which transportation method I'd
prefer for getting out of this Terran gravity well.

I've been to some talks about space elevators. The platform can sit
on some large ships, like oil tankers; when one of the ships needs
overhaul you pull it out and slip in the replacement standing by. One
of the ship's engines could provide the power. My imagination runs
like this:

1) Goggles, everyone!

2) A great big engine cranks up somewhere nearby.

3) Nobody looks at the elevator, which starts rising quietly. (Beware
reflected laser light!)

4) Maybe not impressive, but deeply satisfying from my point of view.

If an airplane flies into the elevator cable, the most expectable result
is two pieces of airplane falling from the sky.

A ribbon cable can be renewed by continually adding on one side, and
removing on the other.

The problem I do not hear anyone talking about is, how do you
consistently and efficiently grow nanotubes up to a few cm long? If
we can learn to do that, seems to me, the rest of it is (relatively)
easy. My guess for the #2 major problem: achieving an adequate
energy density of the laser light that powers the elevator's motors,
without melting the hardware.

Re airplanes again, have you thought what you might do with such
a laser if you spotted a known hostile airplane coming up over the
horizon? The laser will have to be gimballed in any case, to track
the elevator through the cable's swinging across some of the sky.
Just make the gimbals with a wider range.

My guess for the #3 major problem: destructive people who have no
contributions to society but they will run around breaking things.

I've seen a book around, and I had a peek into it. Space elevator
theory (i.e, mathematical). It outlines where the physics pinches if
you want to do a space elevator. I think one of the Liftport principals
wrote it.

Cheers -- Martha Adams

"sal" wrote in message
news
I have two naive questions about a space elevator to which I haven't
seen clear answers. Both have to do with the bottom 0.5% of the
cable:
the part in the atmosphere. (I hope this isn't too off-topic for a
_policy_ newsgroup...)

1) How is the cable expected to handle tropical storms? Is it
believed that such a structure could ride out hurricane force winds
without turning into Galloping Gertie? Or is it assumed that, since
the
elevator will touch down either on the equator or very near to it,
hurricanes won't be an issue, since they normally don't form closer
than
about +/- 300 miles from the equator (due to lack of Coriolis effect)?

The 300 mile "restricted zone" for hurricanes sounded good until I
realized massive storms can migrate to the equator, even if they can't
form there, and even if they're doomed by crossing the equator they
still
might be able to cause significant havoc to a ground station on the
equator.

One issue with riding out strong winds, of course, is that the
tension vector is almost straight up, even if the the cable has been
pulled far off to one side: at the top of the atmosphere we're already
more than 99 percent of the way down. This would seem to suggest that
the cable will not be very "stiff" in response to horizontal
wind loading.

2) What's the current story on the atmospheric E and B fields? I seem
to recall a shuttle experiment with a tethered satellite failed due to
high electrical tension along the cable. Now, as I understand it,
that was most likely due to the earth's B field (which the shuttle
cuts across at high speed), which would presumably not be an issue
for something stationary WRT the Earth's surface. But the atmosphere
also has a significant (vertical) E field. I've seen speculation
(elsewhere) that this would be a problem for an elevator; I've
speculated
privately that this could be a great resource for an elevator to tap
(if
the voltage isn't too impossibly high). Does anyone here know the
correct
story on this? Is it even an issue?


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