Trajectory Optimization and Guidance for Solid Motor Propelled Launch Vehicle Ascent

A solid motor propelled launch vehicle is used to inject an air-breathing engine into a predetermined flight envelope defined by altitude, flight path angle, Mach number and angle of attack. For solid motors, thrust termination is only through fuel exhaustion, and thus the desired terminal conditions are to be achieved precisely at stage burn-out time. Path constraints of dynamic pressure, bending load, and heat flux also need to be satisfied. The problem is formulated as a trajectory optimization problem, which is further reduced to a nonlinear programming problem (NLP) using discretization of the control, and is solved using a metaheuristic optimization technique called harmony search optimization. The versatility of the proposed method is demonstrated by optimizing for different objectives and constraints. Additionally, an endo-atmospheric closed loop guidance algorithm based on model predictive control is proposed to track the trajectory precisely and achieve desired terminal conditions in presence of dispersions during flight. The execution time of the proposed guidance algorithm is also minimized by optimum selection of guidance cycle time, prediction horizon time, and integration time step of the predictor model. Robustness of the proposed guidance algorithm is evaluated for aerodynamic and thrust uncertainties.