Trading Rockets for Space Elevators

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The scientists have produced yards of woven, pure nanotubes in sheets two inches (five centimeters) wide. The method is easily scalable to produce sheets of any dimension and can roll them out as fast as 33 feet (7 meters) a minute.

The technique, which is described in the August 19 issue of the journal Science, begins by building nanotubes. Gaseous carbon atoms are coaxed to deposit themselves onto a specially prepared surface in an oven. The surface "catches" the atoms in such a way that they cling to each other and form into tubes.

Baughman likens the result to a tiny bamboo forest. The researcher catches the row of tubes from the "forest edge" with an adhesive strip. As the first row is pulled away, the second row clings to its neighbor and is also pulled away. Eventually, enough of a sheet is pulled away that it can be reeled up with a plastic roller.

But for now, the resulting "fabric" isn't nearly as strong as Kevlar.

Versatile Tubes

Other scientists have experimented with producing nanotube-based materials by embedding the tubes in polymers—large, chain-like molecules made from repeating links of smaller molecules. Rodney Andrews from the University of Kentucky has produced fibers this way that are five times stronger than Baughman's.

"What's good about Ray's [product] is that it's made entirely out of nanotubes," Edwards said. "And the final material that will make up the [space elevator] tether will probably have to be at least 50 percent nanotubes."

Making the new carbon nanotube sheets stronger is a matter of finding better pulling methods and more advanced surfaces. Still, research won't produce a viable tether for some time, probably a few decades, Baughman said.

Edwards's own company, Carbon Designs Inc., also develops nanotube-based materials. He and other experts are slightly more optimistic, putting the estimated time of arrival of a space elevator tether at less than 20 years.

So don't pack your bags for the first space elevator trip anytime soon. But in the near future you might see carbon nanotubes coming to more commonplace products.

Carbon nanotubes have other interesting properties besides their strength, and Baughman has already demonstrated that their conductivity can make his sheets glow, providing whole surfaces that give light.

He's also shown that a sheet placed between pieces of glass will heat up when electrified, and may make for the perfect in-glass radio antenna.

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