<h2>AAS  96-194</h2><h2>OPTIMAL LOW THRUST INTERPLANETARY TRAJECTORIES BY DIRECT METHOD TECHNIQUES</h2><h4>C. A. Kluever, University of Missouri-Columbia/Kansas City</h4><h2> Abstract </h2>A direct optimization technique for obtaining optimal, low-thrust, interplanetary trajectories has been developed.  The program allows free and fixed end-time problems, multiple powered and coasting arcs, planetary gravity assists, constant and variable thrust models, and a variety of launch vehicle options.  The ability to optimize spacecraft sizing parameters is also included.  The optimal control problem is replaced by a nonlinear programming problem which in turn is solved by utilizing sequential quadratic programming.  Three optimal trajectories are obtained and presented: 1) an Earth-Mars transfer with Venus gravity assist, 2) an Earth-Jupiter transfer, and 3) an orbit transfer to the heliopause boundary with multiple planetary gravity assists.<br><br>