Orbital ring

This article is about artificial planet-spanning object. For naturally occurring rings, see ring system. For rings made of artificial satellites, see orbit.
Lunar orbital rings
An orbital ring that has fixed tethers hanging down to the ground. The stations produce lift by bending the ring cable downward as it passes through them.

An orbital ring is a concept of an artificial ring placed around a body and set rotating at such a rate that the apparent centrifugal force is large enough to counteract the force of gravity. For the Earth, the required speed is on the order of 10 km/sec, compared to a typical low Earth orbit velocity of 8 km/sec. The structure is intended to be used as a space station or as a planetary vehicle for very high-speed transportation or space launch.

Because the cable is spinning faster than orbital velocity, there is a net outward force that is countered by internal tension within the cable. This resists any attempt to bend it and allows it to carry loads. In typical conceptions, a motorized platform is placed on the cable that runs in the opposite direction at the speed that makes it appear stationary above the ground. Above Earth's equator, a platform running at 9.5 km/sec in the direction opposite the cable will appear stationary and allow a cable to be lowered to form a space elevator. This elevator is only perhaps 500 kilometres (310 mi) long, which can be built with existing materials.

The requirement to construct a planet-sized cable in low-earth orbit and accelerate it to a faster-than-orbital velocity is an obvious practical problem. Other architectures have thus been proposed that use active support in different ways and are thus able to circumvent some of these limitations. The launch loop is a partial ring, perhaps 2000 km long, that runs between two ground stations instead of encircling the world. The particle ring uses a series of separate objects that can be launched individually to produce a collection similar to a solid ring and then controlled magnetically, with the disadvantage that they have no internal tension and lifting power is derived separately. The space fountain is a vertical version of the particle ring concept that forms a space elevator. The tethered ring is a dynamic structure that uses at least one complete and continuous non-orbiting ring with a diameter that is smaller than that of the planetary body. It can be built on the planet’s surface, accelerated to operating speed, and raised to a very high altitude mechanically by tensioning its numerous tethers.[1][2]

  1. ^ US 11014692B2, issued 2021-05-25 
  2. ^ Swan, Philip (2023). "The Techno-Economic Viability of Actively Supported Structures for Terrestrial Transit and Space Launch". 2023 IEEE Aerospace Conference. pp. 1–20. doi:10.1109/AERO55745.2023.10115896. ISBN 978-1-6654-9032-0. Retrieved 2023-12-12.