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(詳細はspace tethers have been deployed in space missions. Tether satellites can be used for various purposes including research into tether propulsion, tidal stabilisation and orbital plasma dynamics. The missions have met with varying degrees of success; a few have been highly successful. ==Description== Tethered satellites are composed of three parts: the base-satellite; tether; and sub-satellite. The base-satellite contains the sub-satellite and tether until deployment. Sometimes the base-satellite is another basic satellite, other times it could be a shuttle, space station, or the Moon. The tether is what keeps the two satellites connected. The sub-satellite is released from the base assisted by a spring ejection system, centrifugal force or gravity gradient effects. Tethers can be deployed for a range of applications, including electrodynamic propulsion, momentum exchange, artificial gravity, deployment of sensors or antennas etc. Tether deployment may be followed by a station-keeping phase (in particular if the target state is a vertical system orientation), and, sometimes, if the deployment system allows, a retraction. The station-keeping phase and retraction phase need active control for stability, especially when atmospheric effects are taken into account. When there are no simplifying assumptions, the dynamics become overly difficult because they are then governed by a set of ordinary and partial nonlinear, non-autonomous and coupled differential equations. These conditions create a list of dynamical issues to consider:〔NASA, (Tethers In Space Handbook ), edited by M.L. Cosmo and E.C. Lorenzini, Third Edition December 1997 (accessed 20 October 2010); see also version at (NASA MSFC ); available on (scribd )〕 * Three-dimensional rigid body dynamics (librational motion) of the station and subsatellite * Swinging in-plane and out-of-plane motions of the tether of finite mass * Offset of the tether attachment point from the base-satellite center of mass as well as controlled variations of the offset * Transverse vibrations of the tether * External forces 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Space tether missions」の詳細全文を読む スポンサード リンク
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