Deorbiting of LEO satellites with electrodynamic tethers

Abstract

We analyze and compare to each other the deorbiting performance of several tether systems where electron collection from ionosphere is obtained with either simple bare wires or bare wires terminated with conducting balloons. Besides enhancing the current, the balloon flattens the current profile along the tether and both the effects cause a significant increase of the electrodynamic drag. The first part of paper is focused in evaluating the deorbiting times of a 5km long tether, equipped with balloons of different radii (up to 2.5m) attached to a satellite of 5OOkg mass. This analysis is performed for the simplest case of equatorial orbits, vertically oriented tethers and constant values of magnetic field and orbital velocity. In a second part of paper, referring to a bare tether with a balloon of 2.5m radius, the study is extended to conditions more realistic for practical applications. In particular we consider inclined orbits, a dipole model of the Earth’s magnetic field, the variation of orbital velocity with altitude and, in addition, the possible tether deviation from a vertical alignment under the combined effects of gravity gradient and electrodynamic force. Our resuits -indicate that the use of systems with terminating balloons significantly enhances the deorbiting capabilities of the electrodynamic bare tethers.