Abstract: For hypersonic vehicles which use scramjets as their propulsion systems, there is a potential coupling effect between engine thrust and structure flexibility, which may result in thrust coupling aeroservoelasticity (ASE). In order to research the mechanism and effect of the coupling, the longitudinal dynamic characteristics of a simple air-breathing hypersonic vehicle with a scramjet are studied. A general methodology to model and analyze the thrust coupling aeroservoelasticity of this kind of hypersonic vehicles is developed, which takes into consideration the coupling of structure flexibility, unsteady aerodynamics, propulsion system and flight control system. The unsteady aerodynamics of the hypersonic flow is computed using Newton impact theory, and the engine performance is analyzed based on one-dimensional flow assumption. Simulation results indicate that, the coupling of the propulsion system affects obviously the short period mode and the aeroservoelastic characteristics of a hypersonic vehecle. The aeroservoelastic stability margin of the numerical example in this paper is decreased by 16%, which should be brought to the attention of those concerned with flight control system design.

Key words: hypersonic vehicle, aeroservoelasticity, scramjet, thrust coupling, Newton impact theory