Going up? Space elevator could slash launch costs.

Since the dawn of the Space Age, people and hardware have thundered into orbit, shoved skyward by barely controlled explosions. Now, a loosely connected group of scientists and engineers hopes to make a launch as easy - and nearly as gentle - as pushing the "penthouse" button on an elevator.

To proponents, space elevators promise to slash the cost of sending cargo and people into space. And, they say, elevators would eliminate the costly need to overengineer satellites and other payloads to survive the rigors of a launch.

And where once even supporters held that space elevators were decades away, some scientists and engineers suggest that the first elevator could be running in 15 years. That bold prediction involves two big assumptions, they acknowledge. First, new materials currently in the laboratory will live up to their potential; second, potential environmental and political hurdles will be overcome.

Space elevators long have drawn snickers from skeptical aerospace engineers.

"The concept always has been seen as science fiction," says David Smitherman Jr., with the advanced-projects office at NASA's Marshall Space Flight Center in Huntsville, Ala. He notes that many people believed that the right materials for building one didn't exist.

With the discovery in the 1990s that a unique type of carbon can form tiny tubular strands, however, some of the chuckling began to subside. Dubbed carbon nanotubes for their vanishingly small dimensions (roughly 10,000 times as thin as a human hair), in principle these tubes are "strong enough and light enough" to form the backbone of a space-elevator system if the right fabrication techniques can be developed, Mr. Smitherman adds.

Indeed, in its fiscal 2004 budget, the National Aeronautics and Space Administration is seeking $2.5 million to conduct more detailed feasibility studies of space elevators and the role these new materials can play in building them as part of its effort to stimulate thinking about advanced concepts for spaceflight.

One idea that has energized the space-elevator community involves using cargo-carrying "crawlers" that climb and descend along paper-thin ribbons made from carbon nanotubes, anchored to ocean platforms located along the equator. Reaching altitudes of some 62,000 miles, the ribbons would be held taut directly over the same spot on Earth by distant counterweights flung outward in response to Earth's rotation. The crawlers would run on electricity generated by solar cells whose light came from powerful ground-based lasers. Payloads could be released at a range of orbits, while at the far end of the ribbon, they could be released to leave Earth orbit without any additional propulsion.

The concept, developed by Bradley Edwards, a researcher at the Institute for Scientific Research in Fairmont, W. Va., formed the centerpiece of an international space-elevator conference at the Los Alamos National Laboratory last month.

He envisions the elevator being built in stages, with either the shuttle or an unmanned spacecraft unrolling an initial cable or ribbon capable of handling payloads up to 13 tons. Climbers would then continue construction. He estimates that the system could be built for $40 billion some 10 years after the technology is ready. By the standards of today's rockets, which reach speeds of more than 17,000 miles per hour to reach orbit, a space-elevator climber would make its ascent at a far more leisurely pace: about 124 m.p.h.

Such a project would face a range of technical, political, and economic hurdles, notes Bryan Laubscher, an astrophysicist at Los Alamos National Laboratory. One is space junk. Collisions with orbiting debris left over from more than 40 years of rocket launches could severely damage the system. Also, free oxygen atoms at very high altitudes can speed corrosion. Moreover, it remains unclear if carbon nanotubes can be fabricated to produce thousands of miles of continuous fibers.

Still, he adds, he is confident that these problems can be overcome. Given the potential savings in launch costs and in simpler payload designs, it's imperative to push toward developing space elevators, he says. Citing one of the conference speakers, he points out that given its potential economic advantages over chemical rockets, "the first entity to build a space elevator will own space."