Propellantless Transport with the Electrodynamic Tether Sling

The electrodynamic tether sling, a spinning tether with electrodynamic thrust, is described and has the ability to catapult spacecraft onto a variety of trajectories without the need for propellant. The electrodynamic force is used to recover the transferred momentum, change the orbit of the tether, and, because of its asymmetric design, alter the spin rate of the tether. A simple bang–bang current control scheme is developed for the spin-up maneuver, and an elliptical spiral current control scheme is developed to increase the energy of the orbit of the tether while maintaining the perigee close to the high-magnetic-field region near Earth. The equations of motion governing the system are derived and used to demonstrate the effectiveness of the two control schemes. An integral motion of the planar attitude dynamics within magnetic equatorial orbits is obtained, which aids in comprehending the dynamic structure of the attitude motion of the electrodynamic tether sling under the influence of gravitational and electrodynamic torques.