Жер айналысындағы жасанды сақина концепциясы

Conceptual artificial ring around the Earth
artificial planet spanning object

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 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.

The orbital ring is somewhat similar to the "classic" space elevator concept. In the traditional space elevator, a large station is placed in geostationary orbit (GEO) so that it remains in a single location above the equator of Earth. A cable is then built and lowered towards Earth while a second cable, providing a counterweight, is built upward from the station and remains in place due to tidal forces. When the structure is complete, elevator like cars can ride the cable into space. The main problem is that no known substance that can be manufactured in large quantities has the tensile strength needed to stretch from GEO to the surface. Orbital rings use a different mechanism. In the orbital ring version, a kinetic ring is moving around the world at a higher speed than circular orbital velocity. This results in a net outward force that is countered by gravity acting on the stationary components. This can be accomplished at any altitude, although building the system above in order to avoid most of the atmosphere is a practical requirement. A cable is then lowered from the ring to the ground and used in the same fashion as a traditional space elevator, with the difference being that the vertical cable is only instead of long. This length is within the capabilities of several known materials. In order to support the elevator, the ring is not circular but slightly elliptical. Two or more stations are placed at the high ends of the path, but below the point where the orbit's apogee would be normally. The station bends the cable downward as it passes through in order to produce an upward force on the station. The resulting orbit for a two station system looks something more akin to an American football than a rounded ellipse. One can reduce the amount of tension in the orbiting ring to any required level by increasing the amount of lift generated by bending the cable. The main downside is that the elevator cable is now suspended from the high point of the system, rather than being close to the ground. The moving ring does not need to be solid and does not need to be entirely encased by a solid sheath. Instead, a large number of individual magnetic objects can be placed in the desired orbit, and the stations deflect their path using magnets as they pass by. This version of the ring has the advantage of being much simpler to construct, as each element in the ring is completely separate and can be launched individually and requires no further working once in space. It also does not have to be a complete ring; depending on the desired lifting power the total mass of objects might be much smaller than even the thinnest cable circling Earth. The main disadvantage is that the process of momentum exchange randomizes their velocity so some other system is required to shepherd the objects back into the correct orbits.

A detailed description of the concept was proposed and analyzed by Paul Birch in 1982, proposing a massive ring that would encircle the globe in low orbit, from which cables hang down to Earth's surface. In 1982, Soviet inventor Anatoly Yunitskiy also proposed an electromagnetic track encircling Earth, which he called "by wheel into space" (later, "String Transportation System"). When the velocity of the string exceeds 10 km/sec, centrifugal forces detach the string from Earth's surface and lift the ring into space. Andrew Meulenberg and his students, from 2008 to 2011, presented and published a number of papers based on types and applications of low Earth orbital rings as humanity's "stepping stones to space". An overview mentions four applications of orbital rings: communication via a fiber optic ring, surface to orbit transport with a "sling on a ring" system, space based solar power and climate change mitigation with a space sunshade. The "sling on a ring" would involve rotating slings (made of colossal carbon tube) attached to the orbital ring that dip down into the atmosphere. The tip of a given sling would reach an altitude of 13–15 km at its lowest, and its rotation would cause it to have near zero tangential velocity relative to the Earth's surface below. Consequently, the sling could pick up a payload from a conventional aircraft flying at that altitude, then lift up this payload to the orbital ring.

Paul Birch published a series of three articles in the Journal of the British Interplanetary Society in 1982 that laid out the mathematical basis of ring systems.

In the close of Arthur C. Clarke's Fountains of Paradise (1979), a reference is made to an orbital ring that is attached in the distant future to the space elevator that is the basis of the novel. Arthur C. Clarke's 3001: The Final Odyssey (1997) features an orbital ring held aloft by four enormous inhabitable towers (assumed successors to space elevators) at the Equator. The manga Battle Angel Alita (1990 1995) prominently features a slightly deteriorated orbital ring. The Star Trek novel, Ring Around the Sky features a decrepit ringworld in orbit above the planet, Kharzh'ulla, connected by a series of space elevators with the surface. Orbital rings are used extensively in the collaborative fiction worldbuilding website Orion's Arm. The third part of Neal Stephenson's 2015 book Seveneves has an orbital ring around a Moon less Earth.