Trajectory Optimization and Guidance of an Air Breathing Hypersonic Vehicle

Abstract

This paper addresses the problem of trajectory optimization and adaptive guidance law synthesis for constant dynamic pressure ascent phase of a typical Air Breathing Launch Vehicle (ABLV). Characteristics of air-breathing engines, such as fuel flow rate and specific impulse depend upon altitude, Mach number, angle of attack and consequently, a high sensitivity of performance to the flight path exists. Hence the generation of optimal trajectory and development of guidance law for following the prescribed optimal trajectory for ABLV is a challenging task. In the present study, minimum fuel ascent trajectory for constant dynamic ascent phase is first solved using Sequential Quadratic Programming (SQP) technique. Then an adaptive guidance law is developed that controls the angle of attack using a feed back loop based on a second order rate controller for angle of attack (α). The Mission selected is that of a Single Stage To Orbit (SSTO). The algorithm is validated through extensive simulation studies for a conceptual ABLV with launch mass of 200t and 10t payload. Robustness of the developed adaptive guidance algorithm is established through extensive simulation studies. The guidance algorithm ensures that the mission specifications are met accurately for off nominal performance of air-breathing engine as well as aerodynamic parameter dispersions.