From HomoExcelsior

(aka Space Elevator)

A strong cable extending from the surface of the Earth to geo-stationary Earth orbit (GEO). Its center of mass is at GEO such that the entire structure orbits the Earth in sync with the Earth's rotation maintaining a stationary position over its base attachment at the equator. It is envisioned that such a structure would be used as a mass transportation system in the latter part of the 21st century for transporting people, payloads, gasses and power between Earth and space.

Five Key Technologies for Future Space Elevator Development:

1. Nanotechnology has led to the development of a carbon nanotube material that exhibits strengths 100 times stronger than steel. This material is a prime candidate for the space-segment of the space elevator structure.
2. Tether technologies developed for space transportation systems will advance new construction materials and methods in the deployment and control of long structures. The Momentum Exchange Facility is an example utilizing advanced tether technology.
3. Tall tower technology 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. The Launch Arch is a concept utilizing this advanced technology.
4. Electromagnetic propulsion development for high-speed ground transportation, launch assist, and high velocity launch rails 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.
5. Space infrastructure 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 infrastructure could build a space-based economy that would eventually require the development of space elevators to support mass transportation to orbit.