Space Elevator

A space elevator will facilitate faster and cheaper travel of humans, materials and equipment from Earth to space. This structure is slated to replace conventional 'spaceships'.

Scientists and engineers are divided when it comes to the space elevator design. There are those who are convinced that tethering is necessary and there are those who believe otherwise. Tethered designs are more widely accepted than non-tethered designs.

Components of a Tethered Space Elevator

Tethered space elevators require a base station. The base station can be found on a huge floating barge out in the Pacific Ocean or somewhere near the equator. It can also be placed aboard a special aircraft. The base station can also be land-based; such a station has to be built in a location with high altitude.

From the base station will project a stationary, precisely engineered, tapered cable of great strength and flexibility. This cable will be around 60,000 miles (35,800 km) long. Centripetal forces (resulting from the earth's motion) as well as the effects of gravity on the ground-based systems will keep the ribbon in a specific spot above the earth; this ribbon-like cable will be under constant and enormous tension.

Thus the cable needs to be lightweight yet strong enough to resist the constant tension. Though there are no such materials yet, carbon nanotubes show great promise in the field of space elevator cable manufacture.

At the space end of the tethered cable will be a counterweight to keep the other end of the cable positioned in space. This will also serve as the elevator's landing platform in space. There are two proposed designs in this regard. Some believe it would be better to place the apparatus at an orbit that is synchronized with Earth's (geosynchronous orbit) while more scientists like the idea of a counterweight extending above the geosynchronous orbit.

To transport passengers and cargo to and from space, there will be climbers that will 'climb' the tethered cable. The climbers or robotic 'lifters' (comparable to an elevator car) will use the cable or ribbon as a guide track for its ascent into space. Rollers will be clamped on the ribbon and, using a traction-tread mechanism, will pull the cable/ribbon through the lifter. Current plans call for the use of a free-electron laser to beam 2.4 megawatts of energy to photovoltaic batteries or cells on the lifter; these batteries will convert the energy into electricity to power conventional DC electric motors for the lifter.

Once made operational, the lifters would be lifting payload and people nearly everyday. Plans initially call for a five ton lifter at first, eventually increasing the size to 20 tons – which will carry up to 13 tons of cargo in 900 cubic meters of space, at an estimated speed of around 118 miles per hour. Estimated cost for transport will be $100 to $400 per pound; this represents major savings when compared to the thousands of dollars per pound currently spent using rockets to send humans and cargo up to space.