Future --- Space Elevator --- The Construction

Here are the main components of a space elevator:
- An extremely tall base tower on Earth
- A heavy counterbalance mass orbiting the Earth
- A cable that connects the tower to the weight
- A electromagnetic vehicle that can ride the cable into orbit

To better understand the concept of a space elevator, think of the game tetherball. A ball is attached to a pole by a rope. Think of the rope, the pole and the ball as the cable, the Earth and the counterbalance mass respectively. Imagine the ball is put into perpetual spin around the pole, so fast that it keeps the rope taut. The counterbalance mass at the end of the cable spins around the Earth, keeping the cable taut. The electromagnetic vehicle would simply ride up the cable as a train rolls over tracks.
This is generally how a space elevator works.

The base tower built on the Earth would be about 50 km tall. Once the tower is built, scientists would also have to work on the cable, which would extend more than 144,000 km from the equator into space. By the time it is finished, the cable will cover a third of the distance to the moon. Both the tower and the cable would have to be constructured with a material strong enough to span the large distance without begin pulled apart by the Earth and the counterbalance mass.

Research into the feasibility of space elevators indicates that there are Five Key Technologies for Future Space Elevator Development:

- Carbon nanotube (CNT): A lightweight material 100 times stronger than steel. Until recently, scientists lacked a strong material which is light enough to build a cable that could span more than 160,000 km into space. The development of carbon nanotube makes the space elevator a possible option for getting into space. Carbon nanotubes are pure-carbon cylinders that were first created about a decade ago by zapping graphite with lasers. It has a tensile strength of 200 Giga-Pascals (GPa); for comparison, graphite, quartz and alumina each have a tensile strength of just over 20 GPa. NASA has said that a material used to build a space tether would need a tensile strength of 62 GPa.

- Tether technology: Long cables that can transfer momentum from one object to another. At present, tethers are used to attach astronauts to the space shuttle during spacewalks. Tethers attaching a spacecraft to a satellite can be used to pull the spacecraft up and then sling it into space with higher velocity and more fuel efficiency than current launch methods. When this is successful, scientists can further pursue the idea of an Earth-to-space tether.

- Electromagnetic propulsion: Electromagnetic propulsion currently allows a train to hover on a cushion of air, enabling the vehicle to travel at high speeds by eliminating friction. Magnetic levitation trains that can travel at more than 310 mph (500 kph) are already being developed in several countries. These trains use powerful superconducting magnets that give off a great deal of heat. Scientists are searching for room-temperature superconductors that require no cooling and can be used to create maglev trains that require little energy. It will advance the technology needed to travel the 36,000 kilometer length of the space elevator as part of a fast, safe and energy efficient system.

- Tall tower technology: It will foster the development of multi-kilometer height towers for commercial applications. The tallest buildings and towers today are approaching only 2/3 kilometer. Current materials are capable of heights many times taller.

- Space Spacecraft: Space Spacecraft for transportation, utilities, and facilities out to GEO will be needed to support space construction for the space elevator as well as space development in general. Incremental steps towards the development of this Spacecraft could build a space-based economy that would eventually require the development of space elevators to support mass transportation to orbit.

The idea will be combined to construct four to six maglev tracks that would run the length of the cable into space. The space vechicle would either stop at different stages to float satellites or other payloads into space or would use the track as a high-speed launching ramp.

The Construction The Advantage