AAS 95-451

Electric Propulsion for Orbit Transfer in a Resistive Medium

M. Guelman, Aerospace Eng., Technion, Haifa, Israel

Abstract

This paper presents a power limited low thrust optimal guidance law for spacecraft transfer in a central gravitational field with drag effects considered. Drag forces acte along and opposite the vehicle inertial velocity vector. For optimal thrust control synthesis a stationary atmosphere with constant density is assumed. An optimal guidance law is obtained analytically as a particular solution to the case of transfer with free final time. The extremal guidance law is shown to be colinear with the spacecraft velocity vector multiplied by a time varying gain that depends on a single constant of integration. By adequately choosing the integration constant and the free final time, transfer to a final orbit with predesigned semimajor axis and excentricity is performed. Based on the extremal thrust acceleration guidance, a suboptimal guidance for spacecraft orbit transfer in an atmosphere with variable density is developed. Numerical results for a representative case are presented.