Effect of electrodynamic forces on the orbital dynamics of tethered satellites

Tethered satellites have a vast potential for space applications. If the tether is conductive, electrodynamic forces result from the motion of the conductive tether relative to the magnetic field of the Earth. The long-term effect of electrodynamic forces on the equinoctial orbital elements of a tethered system is studied with use of a detailed model of the Earth's magnetic field as well as of the tether dynamics. A detailed gravity and aerodynamic model is used. In all cases studied, bare tethers induce larger electrodynamic forces than insulated tether systems. The results show that Lorentz forces can remove a satellite from orbit more effectively than air drag if a conductive tether is attached to it. A simple control law is used to stabilize tether librations caused by electrodynamic forces. Such an approach for junk removal is practical if the satellite mass is greater than 100 kg or so.