Stabilization of Electrodynamic Space Tethers

Electrodynamic tether propulsion can provide propellantless propulsion capability for a number of important missions in LEO, including stationkeeping for small satellites, boosting of the International Space Station, deorbit of malfunctioning satellites, and orbit raising of payloads. Theoretical analyses, however, indicate that electro-dynamic tethers will experience dynamical instabilities in which the electro-dynamic forces continually pump energy into the tether librations and oscillations. Unless these dynamics are controlled, these instabilities will lead to reduced thrust efficiency and, at worst, loss of control of the tether system. The proposed SBIR effort will develop methods for reliably monitoring the dynamics of both conducting and nonconducting tether structures, and develop control algorithms for stabilizing the dynamical behavior of electro-dynamic tethers. The effort will evaluate several different methods for accomplishing the dynamics monitoring and control, and select for further development the method that provides the optimum balance between reliable control and low hardware and computational costs. The SBIR effort will result in a tether dynamics control package, composed of both dynamics-sensing hardware and feedback control software algorithms, that will enable electro-dynamic tether systems such as propellantless orbital transfer, ISS tether reboost, momentum-exchange/electro-dynamic-reboost tether facilities, and microsatellite stationkeeping to operate safely and effectively.