by Monika Aichele

Space travel is relatively cheap compared with the cost of leaving Earth. The space shuttle, for instance, burns more than half a million gallons of fuel blasting into orbit, making every pound of payload cost $10,000. Now the nonprofit Spaceward Foundation, with a $400,000 grant from NASA, hopes to fast-track the technology to reach space on the cheap, without rockets.

Later this month, the agency will host the 2005 Beam Power Challenge, a $50,000-prize contest to inspire the automated climbing machines and wireless power necessary to lift people and cargo into space on a 21st-century elevator cable.

First imagined by Russian space pioneer Konstantin Tsiolkovsky in 1895, a space elevator consists of a thin, ultrastrong tether that would stretch from Earth’s surface to geosynchronous orbit, a distance of about 22,300 miles. Laser or microwave beams would power elevator cars up the tether.

The goal of the challenge, expected to take place at the NASA Ames Research Center in Mountain View, California, is a bit more modest: to send an automated climber, loaded with cargo, to the top of a 200-foot Kevlar-like tether at a rate of at least one meter per second. A 10-kilowatt xenon spotlight, shining upward from the base of the cable, will power each climber. The fastest climber toting the heaviest payload wins.

Such a setup won’t whisk you into orbit, but that’s beside the point, says Spaceward Foundation director Ben Shelef. “It will get more minds working,” he says. Below, Brad Edwards, author of The Space Elevator: A Revolutionary Earth-to-Space Transportation System, rates the favorites.

Team: University of British Columbia

Climber: A 1.7-pound aluminum disk hugs the cable. It’s driven by a 60-watt DC motor, controlling one roller. Payload: 15 kg.

Power System: The xenon beam strikes 320 silicon photovoltaic cells connected like Christmas lights so that failure in one cell won’t knock out the whole system.

Stumblink Block: Complicated clutch/gear system improves lift but wastes nearly 70 percent of available energy.

Brad’s Take: “The total power is a bit low. It doesn’t sound as if it’s going to go really fast, but in this first test, if you make it up to the top, that’s a success.”

Team: MNK Scientific

Climber: A three-foot, Mylar-coated parabolic dish focuses the beam onto a solar engine, which powers the climber. Payload: 30 kg.

Power System: The beam powers a highly efficient Stirling engine, heated to 1,202