Optimal orbit maneuvers with electrodynamic tethers

Abstract

Electrodynamic tethers can be employed to effect spacecraft orbital maneuvering outside of Keplerian motion without incurring the mass penalty of traditional propulsion systems. Recently, several studies have been conducted to establish a framework for guidance and control of such orbit maneuvers, including the optimization of a particular maneuver, the orbit transfer. This thesis provides an overview of the concept of electrodynamic tether employment, summarizes research in the field, and catalogues recent proposals. Two minimum-time orbit transfer problems are considered - an orbit raising and a deorbit problem. Both formulations use an identical set of initial conditions for the spacecraft. In the case of the orbit raising problem formulation, the terminal manifold requires an increase in semimajor axis and return to initial eccentricity and inclination values. Other orbital elements are unconstrained. For the deorbit case, optimal control is developed for a minimum time decrease in semimajor axis; the remaining orbital elements are unconstrained. The totality of optimality conditions for both cases of using electrodynamic tethers to maneuver from an initial orbit is examined. Observations and recommendations for future work are presented in the conclusions.