At the conference, scientists presented calculations that examined details. Vibrations in the elevator ribbon, which would act like an extremely long plucked guitar string, appeared manageable.
Dr. Anders Jorgensen of Los Alamos raised concerns that as the ribbon swung around through the earth's magnetic field, it would create strong electric currents. Because of the elevator's relatively slow pace, a larger problem could be that any human passengers would receive dangerous doses of radiation as they passed through pockets of high-energy particles trapped in Earth's magnetic field.
The first space elevator would be built to carry only cargo, not people, Edwards said. The dangers could be reduced on subsequent elevators by speeding them up or providing shielding through magnetic fields.
The logistics of construction "appear to be an interesting problem, as well," said Carey Butler, a program manager at the Institute for Scientific Research.
The idea is to launch a spacecraft with the initial spools of ribbon into geosynchronous orbit. As the ribbon unspools and falls to the ground, the spacecraft moves higher to keep the center of mass, or balance point, at the same geosynchronous height. By the time the ribbon reaches the ground, the spacecraft has reached an altitude of 80,500km.
After the ribbon is attached to the base station, the spacecraft unfurls another 16,000km of ribbon. Then a series of about 230 mechanical construction platforms will ascend to stitch on additional ribbon.
While technologically feasible, years of engineering will still be needed. Nonetheless, Clarke, who came up with the idea of using satellites in geosynchronous orbit for communications long before any were launched, thought that he might live to see to live this science fiction idea come true, too.
"I'm 86 now," Clarke said. "So in 20 years' time, I'll only be 106. So maybe I will see it."
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