Integrated aerodynamic-trajectory optimization method considering stability constraints of air-breathing hypersonic vehicle

The typical feature of an air-breathing hypersonic vehicle is the integrated design of the airframe and propulsion systems, which introduces a coupling challenge among aerodynamics, propulsion, control, and flight trajectory. In this study, an integrated aerodynamic-trajectory optimization method incorporating stability constraints is proposed to address this issue. The proposed method adopts a two-layer optimization framework. The outer-layer optimization focuses on configuration parameters, while the inner-layer optimization deals with flight trajectory. In the optimization process, static stability is taken into account as a constraint condition. This integrated method enables mission-level co-optimization of airframe geometry and flight trajectory, achieving synergistic improvements in overall system performance. Meanwhile, to validate this method, a Sänger-type two-stage-to-orbit (TSTO) vehicle was investigated with the minimum climb-phase fuel consumption as the optimization objective. The key design variables included the parameters of the integrated forebody-inlet and aftbody-nozzle. Optimization results demonstrate a 13.6% reduction in fuel consumption of the climb phase compared to baseline configuration, which effectively improves the climbing performance of the vehicle and validates the optimization framework in this paper.