Momentum exchange is also useful. This can be done with either a static or a rotating system. Release of an object from the end of a long tether will insert it into a much higher or lower orbit. This could lead to the use of a tethered release from a space station for a shuttle deorbit without an OMS burn. A swinging tethered release could also be used to insert the ET into a high orbit that is long lived and drop an orbiter to a reentry. This exchanges momentum only and uses minimal fuel. A swinging release can also enhance the payload carrying capability of vehicles to higher orbits (including escape orbits). A swinging release 'steals' momentum from the system and can be used to launch a far more massive payload away from LEO than could otherwise be launched with the same onboard propellents. Savings is in fuels and the advantage is that a more massive and more capable payload is possible. Electrical uses of a conducting tether include the generation of station elctrical power and the orbital raising and lowering of the station. A properly designed tether can generate electricity by interacting with the magnetic field. This induces drag and will lower the station. A current can be forced through the tether with excess electricity and the tether can generate a net thrust. This Alfven Engine can be used for orbital maintenance, orbit changing, and energy storage through momentum. Efficiencies are higher than Ion engines and no propellents are required. Shuttle and station mission enhancements with a tether include additional payload capability to orbit, the saving of OMS fuel by a tether mediated rendezvous with a station, and storage of tanks and liquids. The tether mediated rendezvous can enhance the payload to station capability of the orbiter. It can also allow the scavenging of excess orbiter OMS fuel to the station for station requirements. Storage of liquid in a tethered tank takes advantage of the gravity gradient to store liquids where they can be pumped using conventional methods. VI. Miscellaneous The ET in orbit can also be used in a variety of scientific and military applications. The scientific uses include the use of the ET/ACC combination as a way to launch large mirror arrays for telescopes. The hydrogen tank can be used as an affordable high energy observatory of a far larger size than
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