Space ElevatorClimbing into Earth orbit on a Space Elevator
In "Jack and the Beanstalk," some magic seeds grow into a giant beanstalk that soars high into the sky. Jack climbs it to find a land populated by a giant ogre who owns a hen that lays golden eggs.
Engineers are working on a very similar concept today. Called a space elevator, it would enable us to literally climb into Earth orbit instead of blasting off aboard fiery rockets that unfortunately have a tendency to explode. Space elevators could significantly reduce the cost of getting materials and people into space.
That sounds like science fiction, doesn't it? Until recently it was, but new scientific advances are making the prospects for a space elevator stronger.
Constructing a space elevator inside a conventional building is impossible. There is no technology in the world that would allow engineers to build a structure that could reach all the way into space. A space elevator would have to be built outside, which on the surface, sounds even more impossible but is, in fact, theoretically possible.
The space elevator would consist of a long tether or cable anchored to the ground that would extend up into space. The tether would be connected to a counterweight located in a geosynchronous orbit of 22,236 miles (37,786 km) above the surface. Tension between the Earth and the counterweight, whose orbit keeps it over the same location above the surface, would keep the tether taut.
A conventional elevator uses an electrically powered pulley system with thick wires to move cars up and down. The space elevator would use centrifugal force that results as the elevator cable rotates along with Earth's rotation. Any objects fastened to the cable would experience an upward movement that would counteract the force of gravity. The higher the object travels along the cable, the stronger the upward centrifugal force would become.
Several options are being considered for powering the climbing vehicle, including transferring the energy to the climber through wireless energy transfer and storing the energy in the vehicle before it leaves the ground.
The biggest challenge with a space elevator is constructing the tether. It is difficult to build anything that is more than 22,000 miles long, much less something that would be strong enough to survive the tensions placed upon it in a space elevator. For decades, this obstacle stymied anything other than conceptual work on the idea.
However, recent work in advanced materials has made the space elevator more feasible. Researchers have developed ultra-strong materials using carbon and boron nitride nanotubes, which are very light but extremely strong.
There are other concerns as well. A space elevator would travel relatively slowly, taking about five days to reach geosynchronous orbit. This would make it perfect for bulk cargo, which could be transported at extremely low cost but would not be required to reach its destination quickly. (This is similar to the operation of freight trains today.) Any humans traveling on a space elevator would need protection from the high radiation in the Earth's Van Allen belts.
Space elevators could really open up the cosmos to business. Current launch costs are about $11,000 per pound ($25,000 per kilogram). Space elevators could reduce those costs to about $100 per pound ($220 per kilogram).