Re: beanstalks (was Re: Metallic hydrogen ...)

From: Vincent Cate (vince_at_offshore.ai)
Date: 06/08/04 

Date: 8 Jun 2004 07:08:40 -0700

henry@spsystems.net (Henry Spencer) wrote in message news:<Hyy6vq.s8@spsystems.net>...
> Ten years ago, it was all very hypothetical, with some laboratory-specimen
> fibers not *too* far below the necessary strength, and little realistic
> hope of practical materials using them. Now, fairly suddenly, the fibers
> have *twice* the required strength, making them in quantity is looking
> feasible, and the one major remaining unknown is making a practical
> material with them.

About 48 years ago they discovered "graphite whiskers" with a tensile
strength of 20 Gpa. These are like a layer of graphite rolled up
like a scroll. Carbon nanotubes are like a layer of graphite rolled
up into a tube and connected to itself. The graphite whiskers leave
an edge for glues to bond to. Still 48 years later we don't know
how to glue graphite whiskers into a rope with near the strength
of the graphite whiskers.

In 1981 Moravec and Forward talked about graphite whiskers said:
"Graphite fiber technology is developing so rapidly that a rotating
space cable will soon be feasible. Shortly after that, we may be able
to make cables strong enough to weave a stationary skyhook."

Carbon-nanotubes do not have an open edge to bond to like graphite
whiskers. So they are more slippery than graphite whiskers.
 
Making fibers twice as strong is not getting us any closer to solving
the really hard problem of how to glue them together into a rope.

In another 48 years we might have a glue, but we might not.

  -- Vince
 
History of Graphite Whiskers:
   http://pubs.acs.org/cen/NCW/8142acsn.html
 
Moravec and Forward
http://www.frc.ri.cmu.edu/~hpm/project.archive/general.articles/1981/high.wire/high.wire.html
 
Graphite Whiskers / Nanotubes:
http://members.tripod.com/marosso/nanotube.pdf
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Vincent Cate Space Tether Enthusiast
 vince@offshore.ai http://spacetethers.com/
 Anguilla, East Caribbean http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
You have to take life as it happens, but you should try to make it
happen the way you want to take it. - German Proverb

Relevant Pages

  • Re: beanstalks (was Re: Metallic hydrogen ...)
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    ... >> hope of practical materials using them. ... Now, fairly suddenly, the fibers ... >how to glue graphite whiskers into a rope with near the strength ... >the really hard problem of how to glue them together into a rope. ...
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