<h2>AAS  96-198</h2><h2>CLOSED-FORM THRUST ACCELERATION FOR OPTIMAL POWER-LIMITED TRAJECTORIES</h2><h4>J. E. Prussing, University of Illinois at Urbana-Champaign</h4><h2> Abstract </h2>A subset of minimum-fuel power-limited trajectories has been recently discovered for which the optimal thrust acceleration is a simple, time-varying scalar multiple of the velocity vector. The existence of this solution in an arbitrary gravitational field is proved.  Applications and limitations of this solution are investigated.  Closed-form expressions are obtained for the orbital angular momentum and the time rate of change of the total orbital energy.  Related problems having cost functionals other than fuel consumption are considered, for which this solution is shown to be non-optimal.<br><br>