Image: Pat Rawling/NASA

Now more than two decades after Arthur C. Clarke penned The Fountains of Paradise, space elevators like the one his book described are no longer science fiction. In a recent NASA report (the product of a workshop held at the Marshall Space Flight Center last year), David Smitherman outlines just how researchers might go about constructing such a giant ride.

First, they would need to build a base tower approximately 50 kilometers tall, out of the wind for stability and near the equator for alignment with the geostationary Earth orbit (GEO). The elevator itself would be a long cable tethered to the base tower such that its center of mass was at GEO, some 35,786 kilometers above Earth's surface. Four to six tracks would run up the outside of the tower and cable, carrying electromagnetic vehicles at speeds reaching thousands of kilometers per hour to platforms at various levels. The illustration shows the view from one such platform, looking back towards Earth.

Space elevators, Smitherman concedes, are still some 50 years off: "First, we'll develop the technology," which calls for much stronger materials and higher-speed electromagnetic transit systems, among other things. But the payoff could be enormous: per kilogram of payload, scientists at the workshop estimated the elevator to cost about $1.50 to GEO, compared with the space shuttle's $22,000.