Lateral oscillations of an electrodynamic tether

Two important applications of electrodynamic tethers, among others, are those of using them for deorbiting and/or propulsion. A crucial issue for both applications is the dynamic stability of the tether system. The electrodynamic forces on the tether couple in plane and out of plane oscillations and, especially for ligth systems, can drive the tethrs unstable. In both the applications of deorbiting and propulsion, the tether system is supposed to operate for long intervals of time (months) so that a crucial issue, in view of the fact that the system is potentially unstable, is that of analyzing the constraints to ensure long term safe operations (i.e. with the tether oscillation amplitudes below certain limits). In this paper we consider this issue referring to the lateral oscillations of a flexible tether. We refer to a bare conducting tether with the current to the various tether elements calculated from plasma theory. In addition, we impose a time variation of the current and model the response to changes in ionospheric density.