Space elevator



Space Elevator is the term given to an immense structure constructed by humans which is used to ferry large loads of materials into orbit of a planet. Space elevators generally consist of large structures of carbon nanofiber and metal rings which span straight up from the ground, literally miles high, ending at stations in space. Vehicles using the structure derive power from strands of superconducting material.

Space Elevators were once a common construction by the UNSC, both on Earth and her colonies. There were at least two on Earth, the New Mombasa Orbital Elevator in New Mombasa and the Centennial Orbital Elevator in Havana. Before its loss in 2525, Harvest had seven elevators linked to the Tiara, the orbital port of Harvest. However, during the events of the Human-Covenant War, all of these elevators were damaged, some seriously, during combat engagements.

Real World Theory
A space elevator is a theoretical structure designed to transport and ferry different materials from a planet's surface into space and onto a platform. A Space elevator would consist of a cable attached to the surface on the equator and reaching outwards into space. By positioning it so that the total centrifugal force exceeds the total gravity, either by extending the cable or attaching a counterweight, the elevator would stay in place geosynchronously. Once moved far enough, climbers would be accelerated further by the planet's rotation. The most common proposal is a tether, usually in the form of a cable or ribbon, that spans from the surface to a point beyond geosynchronous orbit. As the planet rotates, the inertia at the end of the tether counteracts gravity and keeps the tether taut. Vehicles can then climb the tether and escape the planet's gravity without the use of rockets. While the engineering of a structure is beyond current knowledge, as it requires an extremely light but extremely strong material (current estimates require a material ~2 g/cm³ in density and a tensile strength of ~70 Gpa). Such a structure could eventually permit delivery of great quantities of cargo and people to orbit, and at costs only a fraction of those associated with current means.

Links

 * Centennial Orbital Elevator
 * New Mombasa Orbital Elevator
 * Tiara
 * Quito Space Tether
 * socialtext.net article

Size
The space elevator is almost mind-bogglingly tall, reaching into thousands of kilometers in height. An orbital tether's center of gravity must be above or at a point of geosynchronous orbit above the body it is located on. Because geosynchronous orbit above Earth is quite high, (35,900 KM above the surface) the height of the elevator would be twice the distance from the surface to the point of geo-sync orbit. This gives orbital tethers (Because the same rule would apply to them all) an average height of 70,000 kilometers above the Earth's surface. Additionally, this means that Cairo Station and all other MAC ODPs orbit at around 35,900 KM above the surface.