Abstract: A two dimensional trajectory optimization model in the vertical plane is established for air breathing hypersonic cruise vehicles, including the rocket boost phase and the air breathing phase. The atmospheric model, the aerodynamic models and the thrust models are modeled in detail so that the features of air breathing hypersonic cruise vehicles can be described comprehensively and accurately. A method based on the local collocation method is established for solving the boost cruise trajectory optimization of air breathing hypersonic cruise vehicles. Normalization scaling, sparsity analysis and an efficient partial derivative calculation method are utilized to help solve the nonlinear programming in order to improve the optimization efficiency. Numerical simulation is carried out for the boost cruise trajectory optimization of air breathing hypersonic cruise vehicles, and the influences of typical design parameters are analyzed. Simulation results show that the proposed method can  solve the trajectory optimization problems of hypersonic cruise vehicles rapidly and accurately, and can be used to analyze the influences of different design parameter values on the optimal trajectory conveniently, demonstrating its application in the flight profile design and optimization of air breathing hypersonic vehicles.

Key words: Air breathing, Hypersonic, Trajectory optimization, Collocation method