SPACE tethers are long members that connect two or more end bodies in the space environment. The tether tension force acting on the end bodies influences the dynamics of the entire system. Because of the variety of interesting dynamics they exhibit, space tethers have many scientific and research applications [1, 2]. Some space tether applications are rudimentary; for example, space tethers are used to ensure that astronauts and equipment do not separate from a vehicle during space walks [3]. More sophisticated applications of space tethers are presented next.

Electrodynamic tethers reduce the need for conventional energy sources such as chemical propellants and even stored electrical power [2, 4]. As a conductive tether travels with high velocity through the Earth’s magnetic field, a Lorentz force can be imparted to the tether by forcing current through the tether; this force can be used for orbital transfer [5]. In addition to providing orbital propulsion, electrodynamic tethers can be used to deorbit low-Earth-orbit (LEO) satellites that have fulfilled their missions; such satellites would be designed to deploy an electrodynamic tether to initiate the deorbiting process. After the satellite is deorbited in a controlled manner, it no longer poses a collision threat to other satellites in LEO [6–8]. Beyond simply enhancing the capabilities of satellite systems, tethers have also attracted considerable interest among researchers as data-gathering and space access tools; a number of these applications have been proposed [9–12]. One such tethered system concept under study uses tethered satellites to employ a momentum transfer technique with the goal of transferring payloads from low orbit to a higher orbit [13, 14]. One far-term application of space tethers is a “space elevator”[13, 15, 16]. Space elevators consist of a cable that is deployed by a satellite in geosynchronous orbit. The purpose of a space elevator is to provide support for crawlers that move from the surface of the earth to space; space elevators present an economical alternative to chemical rockets for delivering payloads to space. Tethered satellites can also be used to produce an artificial gravity effect in orbit. The artificial gravity effect produced by a rotating body is currently under study because significant bone and muscle loss can occur in humans exposed to a microgravity environment for long periods of time [17]. The tethered artificial gravity (TAG) satellite mission was designed to study the operation and dynamics of an artificial-gravity-generating tethered satellite system. The TAG mission profile involves boosting the TAG system to LEO in a packaged configuration using a conventional rocket, deploying the tether, and then causing the system to spin about its center of mass to produce an artificial gravitational effect on bodies located within the end bodies. Preliminary studies of the TAG system deployment dynamics have been performed assuming nearly equal end-body masses [17]. A detailed list of other applications of space tethers and tethered satellites can be found in the Tethers in Space Handbook [18].