OPTIMAL TRAJECTORIES FOR AEROASSISTED, NONCOPLANAR ORBITAL TRANSFER

This thesis considers both classical and minimax problems of optimal control arising in the study of noncoplanar, aeroassisted orbital transfer. The maneuver considered involves the transfer from a high planetary orbit to a low planetary orbit with a prescribed atmospheric plane change. With reference to the atmospheric part of the maneuver, trajectory control is achieved by modulating the lift coefficient and the angle of bank. The presence of upper and lower bounds on the lift coefficient is considered. Within the framework of classical optimal control, the performance indexes studied are the energy required for orbital transfer and the time integral of the square of the path inclination. Within the framework of minimax optimal control, the performance index studied is the peak heating rate. Numerical solutions are obtained by means of the sequential gradient-restoration algorithm for optimal control problems. Numerical examples are presented, and their engineering implications are discussed