Arthur C Clarke said that the space elevator would be built "about 20 years
after everyone stops laughing." I think we
have a while to wait yet (heh heh).


My concerns are also practical. The things I have read sound like a bunch of
folks who have the theory analyzed, but
don't really want to confront the real world details. The math has been
worked out in great detail by a cadre of folks
who have been working on this for many years. Just because something is
impossible doesn't stop folks from designing it.
http://www.space.com/businesstechnol..._020327-1.html


anything with the kind of strength we're talking about here,
under that amount of tension ain't gonna be much bothered by the
occaisional blow.


The tensions are unimaginably high at the hub, but at ground level (at the
ends of the tether), they are zero. A typhoon
would be a BIG problem.


Then there are the electrical effects. A carbon nanotube cable will
conduct
electricity pretty well. Some claim it's a room temperature
superconductor
candidate. A tropical lightning strike can be several million amps and
this
cable will be a pretty good lightning rod. There's the induced voltages
too. The normal atmospheric potential gradient is several million volts
per
meter.

Last I checked deltaV/m was more liket ~200V.

A dV/dM of 200V per meter, in anything approaching a superconductor could
give nearly infinate
current (I=V/R as R approachs 0 --- Ohms law). That is what burned the
Italian tether. I have not seen
any data on how they plan to avoid this fate. I am sure they have a plan - I
just haven't seen it.

Lightening would do bad things to it I am sure.


I heard the speculation about nanotubes being superconductors a few years
ago back before they
were able to produce them in decent quantities but haven't heard anything
since, If they really are I
think somebody would have noticed by now.

I agree. It probably isn't a superconductor, although there might be a way
to make it into one.


To bad though, a superconducting space elevator would be a
neat way to generate "free" power, a-la the NASA/Italian experiment
with a tether a few years back.

The power is there, using it to power the tram would be downright elegant,
but you sure can't ignore it - ask the Italians.

And the next detail is bullistic damage. It forms a ribbon, very thin but a
meter or so wide (tapering). If a piece of
space debris were to blow a hole in it half way up, sufficiently large to
cause a failure, the consequences
would be amazing, as the upper part went winging off into space, and the
lower part came crashing to
earth with a lot of mass and residual velocities of up to 17,000 mph.



Bottom line - the advances in carbon nanotube manufacture show promise. It
used to be said that this thing needed to be made
from "unobtainium" - now it is not quite so unobtainable (but still not
exactly available either.) but there are still many problems,
and more than one look to me to be showstoppers for now.