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'[OT]: Thread spun from pure carbon nanotubes'
2002\10\24@082504 by Russell McMahon

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Thread spun from pure carbon nanotubes

           http://www.newscientist.com/news/news.jsp?id=ns99992965

One small step towards a Space Elevator ... ?
(method not ideal, but allows pure nanotube threads to be drawn.)

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2002\10\31@010226 by Brendan Moran

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At 01:18 AM 25/10/2002 +1300, you wrote:
>Thread spun from pure carbon nanotubes
>
>             http://www.newscientist.com/news/news.jsp?id=ns99992965
>
>One small step towards a Space Elevator ... ?
>(method not ideal, but allows pure nanotube threads to be drawn.)

I'd like to know what the tensile strength of said thread is rumored to
be.  I forget the exact figures, but I expect that the elevator would still
need to be tapered to handle the useful load of several hundred tonnes
required to produce an effective elevator.

--Brendan

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2002\10\31@183933 by Russell McMahon

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> >One small step towards a Space Elevator ... ?
> >(method not ideal, but allows pure nanotube threads to be drawn.)
>
> I'd like to know what the tensile strength of said thread is rumored to
> be.  I forget the exact figures, but I expect that the elevator would
>  still need to be tapered to handle the useful load of several hundred
> tonnes required to produce an effective elevator.

Tensile strength of properly constructed carbon nano-tubes is "enough". The
present material will almost certainly be well below ideal so far.

Regardless of material ANY space elevator will be tapered as the material
use is very much reduced by this and it makes very little sense not to taper
it. We could theoretically make one with currently available materials but
the dimensions and taper ratio would in practice be unmanageable. Diamond
works well enough I believe, but current synthesis techniques and consequent
material cost make it a little impractical so far :-)

"When" we get a practical Space Elevator material it will also be good
enough to allow a single span suspension bridge across the Straits of
Gibraltar. And a few other interesting places as well no doubt.


       RM

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2002\10\31@233047 by Brendan Moran

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>"When" we get a practical Space Elevator material it will also be good
>enough to allow a single span suspension bridge across the Straits of
>Gibraltar. And a few other interesting places as well no doubt.

Of course as with a space elevator, the big problem is the anchor, and the
mechanism for placing the system to begin with.

I read a book called "web between the worlds" (I forget the author and am
trying to find the book;) that detailed the technique required to make a
useful space elevator, and attach it.

He suggested that it could be done by attaching a large captive meteor at
one end, in order to keep the fiber extended.  The anchoring was
accomplished by digging a 2km deep hole in the earth, and piling all the
earth and rock from that next to explosive charges right at the lip of the
hole.  The actual elevator was manufactured in space, and had small
steering rockets connected to a control system that ran its whole length.

The anchoring process was somewhat hair raising, as he had the base of the
elevator drop in from space, using the steering rockets to align the
"bean-stock" and blew the charges to dump in the piled earth as the base of
the stalk was on its descent.  The result was that the coupling to the
earth was earthquake proof, since what was holding it was a mass of several
hundred tonnes of earth, and, due to the asteroid, the "bean-stalk"
wouldn't be likely to collapse.

The power source for the mag trains that hoisted the cargo was supposedly a
large power satellite at the geosynchronous point, and room temperature
superconductors the length of the "bean-stalk".

Other than the anchoring process, the idea seems reasonable.

The question remains: How would we anchor such a space elevator?

We can't build up.  We can't realistically build down, due to the rotation
of the earth...  This anchoring process could have too much go wrong...

When the materials are there, what do we do with them to make the anchor?

--Brendan

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'[OT]: Thread spun from pure carbon nanotubes'
2002\11\02@050839 by Peter L. Peres
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On Thu, 31 Oct 2002, Brendan Moran wrote:

*>The anchoring process was somewhat hair raising, as he had the base of the
*>elevator drop in from space, using the steering rockets to align the
*>"bean-stock" and blew the charges to dump in the piled earth as the base of
*>the stalk was on its descent.  The result was that the coupling to the
*>earth was earthquake proof, since what was holding it was a mass of several
*>hundred tonnes of earth, and, due to the asteroid, the "bean-stalk"
*>wouldn't be likely to collapse.

I would hate to have to deal with the effects of the longitudinal and
other oscillations of this system (and what happens if the asteroid orbit
becomes elliptical because of them). Earthquake on demand ? Meteroite on
demand ? Weather effects on the lower end could be enough to induce the
oscillations. Anybody who knows about wind loads on tall structures etc
will tell you this. The tension induced by weather could exceed the
payload capacity by a couple of orders of magnitude.

Peter

*>Other than the anchoring process, the idea seems reasonable.

Hmmm.

*>The question remains: How would we anchor such a space elevator?

The best way imho would be to have the beanstalk free-floating with a
weight at the bottom flying high in the atmosphere (a big aircraft
basically). Access from ground would be by aircraft docking/landing on
the lower station.

Maintaining such a system in dynamic stability would be less hard than
maintaining an achored beanstalk. Besides it could be moved.

Peter

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