Айналмалы арқан жүйесі: ғарышқа шығудың жаңа жолы

Proposed momentum exchange tether

A skyhook is a proposed momentum exchange tether that aims to reduce the cost of placing payloads into low Earth orbit. A heavy orbiting station is connected to a cable which extends down towards the upper atmosphere. Payloads, which are much lighter than the station, are hooked to the end of the cable as it passes, and are then flung into orbit by rotation of the cable around the center of mass. The station can then be reboosted to its original altitude by electromagnetic propulsion, rocket propulsion, or by deorbiting another object with the same kinetic energy as transferred to the payload. A skyhook differs from a geostationary orbit space elevator in that a skyhook would be much shorter and would not come in contact with the surface of the Earth. A skyhook would require a suborbital launch vehicle to reach its lower end, while a space elevator would not.

Different synchronous non rotating orbiting skyhook concepts and versions have been proposed, starting with Isaacs in 1966, Artsutanov in 1967, Pearson and Colombo in 1975, Kalaghan in 1978, and Braginski in 1985. The versions with the best potential involve a much shorter tether in low Earth orbit, which rotates in its orbital plane and whose ends brush the upper Earth atmosphere, with the rotational motion cancelling the orbital motion at ground level. These "rotating" skyhook versions were proposed by Moravec in 1976, and Sarmont in 1994. This resulted in a Shuttle based tether system: the TSS 1R mission, launched 22 February 1996 on STS 75 that focused in characterizing basic space tether behavior and space plasma physics. The Italian satellite was deployed to a distance of from the Space Shuttle. In 2000 and 2001, Boeing Phantom Works, with a grant from NASA Institute for Advanced Concepts, performed a detailed study of the engineering and commercial feasibility of various skyhook designs. They studied in detail a specific variant of this concept, called "Hypersonic Airplane Space Tether Orbital Launch System" or HASTOL. This design called for a hypersonic ramjet or scramjet aircraft to intercept a rotating hook while flying at Mach 10. While no skyhook has yet been built, there have been a number of flight experiments exploring various aspects of the space tether concept in general.

By rotating the tether around the orbiting center of mass in a direction opposite to the orbital motion, the speed of the hook relative to the ground can be reduced. This reduces the required strength of the tether, and makes coupling easier. The rotation of the tether can be made to exactly match the orbital speed (around 7–8 km/s). In this configuration, the hook would trace out a path similar to a cardioid. From the point of view of the ground, the hook would appear to descend almost vertically, come to a halt, and then ascend again. This configuration minimises aerodynamic drag, and thus allows the hook to descend deep into the atmosphere.

The capture ejector rim is a variation that consists of a rim or ring shaped structure. Like a rotating skyhook, it would rotate in a direction opposite to its orbital motion, allowing a spacecraft at suborbital velocity to attach to its lower portion and later be flung into orbit from its upper portion. It would be easier for a spacecraft to attach to the lower portion of a capture ejector rim than to attach to the end of a skyhook (which would only point downwards for a brief period of time).