Entry Guidance and Trajectory Control for Reusable Launch Vehicle

Abstract

An entry guidance concept, similar to that of the Space Shuttle, is considered for the reusable launch vehicle (RLV). But the reference trajectory deŽ ned by drag proŽ le is parameterized and optimized as piecewise linear functions of the energy. Analytical expressions for accurate downrange distance prediction and a performance index, theaccumulatedheat load,are obtained.A regularizationtechniqueisemployed toachievedesired properties of the optimal drag proŽ le. These results enable fast design of constrained optimal trajectories for both offline studies and possible onboard application. A nonlinear control law is derived for trajectory tracking, which guarantees globallyasymptoticallystable tracking of the reference drag proŽ le. Numerical results for a conceptual RLV are provided to demonstrate the optimal design of drag proŽ les and the performance of the trajectory control law under a variety of off-nominal conditions and navigationerrors in altitude rate.