AAS 96-149

OPTIMAL GRAVITY-ASSISTED SPACECRAFT TRAJECTORIES FOR OUT-OF-ECLIPTIC INTERPLANETARY MISSIONS

M. A. Jalali and S. H. Pourtakdoust, Sharif University of Technology

Abstract

The present study focuses on an optimal control and trajectory design of a spacecraft in a three-dimensional fly-by with any planet. The spacecraft equations of motion, in a rotating coordinate system centered at planet, are obtained assuming the Newton's inverse square law and neglecting other disturbances. The optimal control problem is set up using soft-constraints where the cost function penalizes both the total maneuver time as well as the control expenditure in quadratic form. Intermediate coast arcs are not allowed in the maneuver structure and end conditions are in the form of functional constraints requiring the spacecraft absolute velocity vector to be along the required direction. The numerical scheme is through the method of direct collocation and nonlinear programming (DCNLP). Using the above technique a numerical simulation is performed for the trajectory and control design of the Ulysses mission and the results are compared with the baseline available data.