English: Artist concept: The One and only Russian Space Elevator. The 'once upon a time' science fiction concept of a space elevator has been envisioned and studied as a real mass transportation system in the latter part of the 20th century. David Smitherman of NASA's Marshall Space Flight Center's Advanced Projects Office has compiled plans for such an elevator. The space elevator concept is a structure extending from the surface of the Earth to geostationary Earth orbit (GEO) at 35,786 km in altitude. The tower would be approximately 50 km tall with a cable tethered to the top. Its center mass would be 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. Electromagnetic vehicles traveling along the cable could serve as a mass transportation system for transporting people, payloads, and power between space and Earth. This illustration by artist Pat Rawlings shows the concept of a space elevator as viewed from the geostationary transfer station looking down the length of the elevator towards the Earth.