ASCENT GUIDANCE FOR AN AEROSPACE PLANE

Abstract

A single-stage vehicle using airbreathing propulsion holds promise for a more economical delivery of payloads to orbit. The utility of the vehicle is contingent on having a guidance capability for flying a near minimum-fuel ascent trajectory. The challenges in ascent guidance are identified via an analysis of the guidance problem relative to that for the U.S. Space Shuttle. Feedback guidance logic for the hypersonic phase of a near-minimum-fuel ascent trajectory is described. The two-time- scale nature of the vehicle translational dynamics allows the translational state space to be decomposed approximately into an invariant slow manifold and an invariant foliation of fast manifolds. Robust near-optimal guidance is synthesized as a composite of the minimum-fuel control on the slow manifold—as determined by the dynamic pressure and heat rate constraints—and a fast control for robust tracking of the slow manifold in the presence of atmospheric disturbances and modeling errors. The tracking control is designed using feedback linearization and the bandwidth-limited variable structure control method. Simulations indicate the effectiveness of the guidance logic.