A Real-Time Guidance Algorithm for Aerospace Plane Optimal Ascent to Low Earth Orbit

Problems of on-board trajectory optimization and synthesis of suitable guidance laws for ascent to low Earth orbit of an air-breathing, single-stage-to-orbit vehicle are addressed A multimode propulsion system is assumed which incorporates turbojet, ramjet, SCRAMJET, and rocket engines. An algorithm for generating fuel-optimal climb profiles is presentd. This algorithm results from application of the minimum principle to a low order dynamic model that includes angle of attack effects and the normal component of thrust Maximum dynamic pressure and maximum aerodynamic heating rate constraints are considered. Switching conditions are derived which, under appropriate assumptions, govern optimal transition from one propulsion mode to another. A nonlinear transformation technique is employed to derive a feedback controller for tracking the computed trajectory. Numerical results illustrate the nature of the resulting fuel-optimal climb paths.