Nasa

Space Elevators: an Advanced Earth-space Infrastructure for the New Millennium Nasa

What is a space elevator? A space elevator is a physical connection from the surface of the Earth to a geostationary Earth orbit (GEO) above the Earth .35,786 km in altitude. Its center of mass is at the geostationary point such that it has a 24-hr orbit and stays over the same point above the equator as the Earth rotates on its axis. The vision is that a space elevator would be utilized as a transportation and utility system for moving people, payloads, power, and gases between the surface of the Earth and space. It makes the physical connection from Earth to space in the same way a bridge connects two cities across a body of water. The Earth to GEO space elevator is not feasible today, but could be an important concept for the future development of space in the latter part of the 21st century. It has the potential to provide mass transportation to space in the same way highways, railroads, power lines, and pipelines provide mass transportation across the Earth's surface. The low energy requirements for moving payloads up and down the elevator could make it possible to achieve cost to orbit <$10/kg. The potential for low-cost mass transportation to space makes consideration of the technology paths required for space elevator construction very important today. The technology paths are beneficial to many other developments and can yield incremental benefits as progress is made toward making space elevator construction feasible.