Orbital ring
From Wikipedia, the free encyclopedia
An Orbital Ring is a concept for a space elevator that consists of a ring in low earth orbit that rotates at slightly above orbital speed, that has fixed tethers hanging down to the ground.
The structure is intended to be used for launching payloads into space.
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[edit] History
The original orbital ring concept was explored in detail by Paul Birch and published in Journal of the British Interplanetary Society.
[edit] Birch's model
In the Paul Birch design of an orbital ring system, a rotating cable is placed in a low Earth orbit, rotating at slightly faster than orbital speed. Not in orbit, but riding on this ring, supported electromagnetically on superconducting magnets, are Ring Stations that stay in one place above some designated point on Earth. Hanging down from these Ring Stations are short space elevators made from cables with high tensile strength to mass ratio. Paul Birch found that since the Ring Station can be used to accelerate the orbital ring eastwards as well as hold the tether, it is possible to deliberately cause the orbital ring to precess around Earth instead of staying fixed in inertial space while the Earth rotates beneath it. By making the precession rate large enough, the Orbital Ring can be made to precess once per day at the rate of rotation of the Earth. The ring is now "geostationary" without having to be either at the normal geostationary altitude or even in the equatorial plane. This means that using the orbital ring concept, a Ring Station can be positioned above any point on Earth that is desired, and anywhere on the globe can be served by a space elevator instead of just the equator. A network of orbital ring systems crossing, for example, at the poles, could cover the whole planet with an array of elevators and geostationary ring stations.
The estimated cost for the system was around $15 billion and a per kilogram cost to place payload in orbit was around $0.05/kg in 1980s money.[1]
