Optimal Ascent Guidance for Air-Breathing Hypersonic Flight Vehicle

摘要

Due to the strong nonlinear coupling between aerodynamics and propulsion of air-breathing hypersonic vehicle, the optimal ascent trajectory problem is very complicated. This paper investigates a feasible and reliable method to generate optimal ascent trajectories for air-breathing hypersonic flight vehicle. The vehicle model is a single stage to orbit vehicle with full flight envelope engine which include turbojet cycle, ramjet cycle, and scramjet cycle Optimal formulation has been developed to the ascent dynamics by using the indirect method This method is very sensitive to any changes of parameters but can produce accurate results for specific problem. The trajectory optimization is to find the body-axis orientation which determines the thrust direction and aerodynamic forces for any given time. Performance index is chosen to maximize final mass. The classic finite difference and modified Newton method is used to numerically solve the two point boundary value problem. A homotopy scheme to the vehicle reference area is used to get final solution from initial guesses. The converged solution for the current value of reference area serves as initial guess for the solution with the next value of reference area till it is full size. A number of test cases are presented to verify the optimal algorithm.