A bundle of seven wires
(Is it me or does this look obscene?)
|Carbon has long been known to make lightweight, tough materials.
Dr. Sumio Ijima of Japan's NEC Corp. officially discovered multi-walled
nanotubes in 1991, though carbon "whiskers" had been observed
as far back as the 1960s.
But what has engineers and scientists excited, (if in fact engineers CAN get excited), are carbon nanotubes that are cigar-shaped molecules with atoms connected in a kind of hexagonal chicken wire -with the seams sealed along the vertical axis and in their rounded ends -so it has no reactive edges from which it might unravel. It's also flexible, with great tensile strength. The number most often quoted is, 100-times stronger than steel, at about one-sixth the weight.
Dr. Richard Smalley of Rice University shared in the 1996 Nobel Prize
in chemistry for the 1985 discovery of spheres of 60 carbon atoms, called
Buckminster Fullerines or Buckyballs. He says, "Individual tubes
are the strongest, meanest damned thing going".
Theoretically, one could create nanotubes that extend from the Earth into space - there's no physical limit to their length. They are currently made using four basic approaches, but only two are mainly being used because they're fast. With Pulsed Laser Vaporization, pulsed lasers strike a catalyst of graphite and metal - cobalt and nickel - which are vaporized into a tube filled with pressurized argon in an oven heated to 1473 degrees Kelvin. In those extreme conditions the nanotubes self-assemble from the carbon vapor and then condense on the flow tube's walls.
In Electric Arc Discharge, developed at the University of Montpellier in France, the carbon is also vaporized but this time catalysts of nickel and yttrium are vaporized from an anode when it's hit with 100 amps of electricity at 35 volts. The nanotubes self assemble in a stainless steel chamber filled with low-pressure helium gas, cooled by water. Got all that? Me either.
The longest single wall nanotube to date is a millimeter, and even Smalley's technique yields just 10 grams of useful material per day.
"In regards to the space elevator using carbon nanotubes - I myself do not personally see the benefit of using single walled or multiwalled carbon nanotubes when composite materials made from graphitic fibers can perform similarly, and much more cheaply. The bulk use of carbon nanotubes is still a very long way off, and a tremendous amount of development effort will be required for this vision to ever be realized. I think this application for CNTs is a little crazy, but hey, a lot of crazy ideas have eventually found their niche. It just may take a very long time," argues Dr. Alan M. Cassell, Senior Research Scientist of the Eloret Corporation at NASA Ames Research Center.
As Smalley remarked, "until strong, continuous tubes are in the hands of engineers, it's all idle speculation."
And Bill Gates once said about hard drives, "483k ought to be enough for anyone". :)