Trading Rockets for Space Elevators

August 25, 2005

Blasting a space shuttle away from Earth's gravity and through atmospheric friction at 15,000 miles an hour (24,140 kilometers an hour) is the most dangerous and costly part of every mission.

Why not just take an elevator instead? Thanks to a new development in the manufacture of molecule-size cylinders known as carbon nanotubes, that may one day be a viable option.

In theory, space elevators need a fixed line, or cord, that stretches from an anchor on Earth to a station out in space. The station acts like a counterweight, forever "held" above the planet by the centrifugal force from Earth's rotation.

A tram-like vehicle equipped with electric motors could climb this tether from Earth's surface into space at a safer speed than rocket alternatives.

In theory, space elevators would need far less energy than conventional space launches. As a result, the cost of transporting matter could drop from U.S. $20,000 a kilogram (the going rate for the space shuttle) to as little as $250 a kilogram.

"This is a trillion-dollar moneymaker for a ten billion dollar investment," said Bradley Edwards, whose work with Los Alamos National Laboratory and the NASA Institute for Advanced Concepts has made him a go-to expert on space elevators. "Some of the largest companies in the world are just waiting for the word that this is possible."

Conquering Carbon

The word on cheap space freight rates won't be sounded until at least one major obstacle is overcome: developing a strong enough material for the tether. Scientists believe they found the fibers for that material—carbon nanotubes—in 1991.

The tubes are molecules of carbon linked together in a shape that resembles a Chinese finger trap. Carbon is among the stickiest elements, and these tubes hold together hundreds of times better than Kevlar, the material used to make bullet-proof vests.

In theory, a space elevator tether made of carbon nanotubes would look and feel like a span of three-foot-wide (one-meter-wide) plastic wrap that stretched skyward as far as the eye could see. It could be rolled up and simply dropped to the ground from space-based orbit.

The problem with this scenario is that individual carbon nanotubes are only millimeters tall and nanometers wide. (A nanometer is a billionth of a meter.) No one has successfully woven the tubes together in a way to make sheets that are as strong as their individual fibers.

But Ray Baughman, who directs the Nanotech Institute at the University of Texas at Dallas, and his team have developed what could be a first step.

Continued on Next Page >>




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