The Space Elevator
New Book on an Intriguing Alternative
I got a note from Graham O'Neil, recommending a book entitled The Space Elevator, by Bradley C. Edwards and Eric A. Westling, which brings up to date the fascinating idea of achieving low-cost transportation to space by means of a "vertical railroad to synchronous orbit" -- popularized by Arthur C. Clarke in The Fountains of Paradise. A synchronous satellite orbits above the equator at such a distance (about 22,000 miles) as to have the same period as the Earth's rotation, which keeps it hanging over the same fixed point -- which is why you can keep your satellite dish pointing at it. The idea of the elevator is to construct a line (the one proposed in the book is a ribbon 2 meters wide, shaped to minimize wind loading within the atmosphere and damage from meteoroids, radiation, etc. beyond it) up to a synchronous station and beyond, the excess portion providing an outward force that would enable payloads to be winched up. As they climb, the energy to accelerate them to synchronous orbital velocity is imparted by the Earth's rotation. At the top, you just step off into freefall.
What makes the concept worth looking at again now is that by the authors' calculations, carbon nanotube fibers possess the tensile strength to make such a project feasible with a comfortable margin. In fact, they estimate that a system capable of lifting a 13-ton payload to orbit every few days be built . . . in 10 years for a cost of $6 billion -- less than half NASA's annual budget. The main obstacle at present is the lack of an infrastructure for mass-producing carbon nanotube materials.
Wider ribbons would afford the capacity to lift 200-ton loads, setting the scene for a significant human presence at geosynchronous orbit, with costs reducing to the level where a university could afford to run its own launch system. Taking the concept out to 100,000 kilometers distance would provide sufficient centrifugal acceleration at the tip to fling loads out to Mars, Venus, and the Asteroid Belt with little additional energy expenditure. The book ends with a fanciful vision of space elevators bristling around Earth, Mars, and the Jovian moons, providing an efficient space transportation network for the inner Solar System.
The Space Elevator: A Revolutionary Earth-to-Space Transportation System by Bradley C. Edwards and Eric A. Westling, Spageo Inc., ISBN: 0972604502. Full review at Slashdot.com.