Scientists are working to turn this fantastic concept into reality. They hope that 20 or 30 years from now anyone will be able to travel beyond the Earth’s atmosphere on an elevator. The idea involves hanging an elevator cable, or ”belt,” from a satellite orbiting 36,000 kilometers above the equator.
Satellites orbiting the Earth are affected by two forces. One is gravity, which acts to pull them down toward the Earth. The other is centrifugal force, which pushes them away from the Earth. By positioning and propelling a satellite so that the pushing and pulling of these forces balance each other out, it is possible to keep the satellite in orbit above a certain point on the Earth's surface. This is called ”geostationary orbit.”
A small experimental "space elevator" ascending its belt
modeling the elevator's structure
The components needed to build a space elevator - the materials, the elevator itself, and robots - can already be made with existing technology. What’s more, these technologies are fields in which Japan has a great deal of expertise, so the prospect of Japanese engineers building a space elevator is not merely science fiction.
Carbon nanotubes were discovered in 1991 by a Japanese scientist. As the name suggests, they are tiny cylinders made up of carbon atoms. Carbon nanotubes are lighter and stronger than conventional materials. They are also good conductors of electricity, so a carbon nanotube belt could not only take an elevator up into space but also transmit the energy needed to power it.
The belt and the equipment for the experiment
The shaft down which the weight is dropped
A 100-kilogram weight is dropped on top of a belt made of carbon nanotubes from a height of 16 meters to test the belt's shock resistance
Another idea being considered is to build a vacuum tunnel around the central axis of the space elevator. This would enable the elevator to travel up the 36,000-km tunnel in just 10 hours. There are still some difficulties to be overcome, such as how to deal with the changes in air pressure that the human body is subjected to when traveling at such high speeds. But whatever the shape of future space vehicles, the journey to completion is bound to be a fantastic voyage.
Courtesy of Professor Aoki Yoshio of Nihon University
(Updated in December 2008)