The International Spation (ISS) will require periodic reboost due to amospheric aerodynamic drag. This is nominally achieved throught the use of thruster firings bu the attached Progress M spacecraft. many Progress flights to the ISS are required annually. Electrodynamic tethers provide an attractive alternative in that they can provide periodic reboost or continuous drag cancellation using no consumables, propellant, nor conventional propulsion elements. The system could also serve as an emergency backup reboost system used only in the event resupply and reboost are deayed forsome reason. The system also has direct application to spacecraft a nd upper stage propulsion. Electrodynamic tethers have been demonstrated in space prviously with the plasma motor generator (PMG) expriment and the Tethered Stallite System Reflight (TSS-lR). The advanced electrodynamic tether proposed for ISS reboost has significant advantages over proevious systems in that higher thrust is achievable with significantly shorter tethers and without the need for an active current collection device, hence making the system simpler and much less expensive.
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