Optimal Design and Deorbiting Performance of Thermionic Tethers in Geostationary Transfer Orbits

The application of a recent concept, a thermionic bare tether (that is, a long conductor coated with a thermionic material), to a practical engineering problem (deorbit space debris from geostationary transfer orbit) is presented. Lorentz drag on a thermionic bare tether, during each pass through an arc close to the perigee, lowers the apogee progressively and produces the object reentry. The performance of a spacecraft equipped with a thermionic bare tether is studied at two different levels, using models that couple thermal and electrical effects. In first place, a simple formula for the eccentricity decrement produced during each perigee pass as a function of TBT properties is derived and used to select TBT optimal dimensions. For a given tether mass, the formula shows that long tethers with small cross-section areas, but large enough to accomplish mechanical constraints, yield the best performance. Second, full numerical simulations of the deorbit maneuver including Lorentz force, air drag, and J2 per...