Space elevator

A space elevator is a type of space transportation system.

Tethered space elevator

The main component of a tethered space elevator is a ribbon-like cable (also called a tether) anchored to the surface of a planet and extending into space. It is designed to permit vehicle transport along the cable from a planetary surface, directly into space or orbit, without the use of large rockets. An space elevator would consist of a cable with one end attached to the surface near the equator and the other end in space beyond geostationary orbit.

The competing forces of gravity, which is stronger at the lower end, and the outward/upward centrifugal force, which is stronger at the upper end, would result in the cable being held up, under tension, and stationary over a single position. Once the tether is deployed, climbers would repeatedly climb the tether to space by mechanical means, releasing their cargo to orbit. Climbers would also descend the tether to return cargo to the surface from orbit.

High strength materials used for the tethers include carbon nanotubes and continuous pseudo-one-dimensional diamond crystal hyperfilaments. For locations with weaker gravity, the strength-to-density requirements are not as great for tether materials.

Freestanding space tower

A more advanced version of the space elevator is the free-standing tower reaching from the surface of a planet to the height of geostationary orbit. Like all buildings, the structure is be under compression, supporting its weight from below.

Among the technologies used in space towers of this type are high strength materials such as super tensile solids. Tubular columns of antigravity generators, dynamic stabilization systems including gyroscopes and "pressure balancing" can also be used to support the structure.