基于气动导数的类X-37B飞行器纵向稳定性分析

In order to quantitatively examine the dynamic characteristics in pitching direction of the tans-atmospheric orbiter under different flight conditions, on the basis of the Etkin aerodynamic model, the effects of Mach number, reduced frequency, oscillation amplitude, and average angle of attack on longitudinal dynamic performance of the orbiter were studied in detail. The results show that the average angle of attack and the Mach number determine the basic characteristics of the flow filed, so they have a great effect on the aerodynamic derivatives. The reduced frequency and oscillation amplitude determine the strength of the unsteady disturbance and that of the unsteady hysteresis effect, so they have a great effect on the unsteady aerodynamic forces. For X-37B like trans-atmospheric orbiter, with the increase of the average angle of attack, the effect of the vortical structure at the leeward side of the afterbody is larger and the longitudinal stability is increased. In the subsonic range, as the Mach number increases, the stability increases, and in the supersonic range, as the Mach number increases, the stability decreases. Although the amplitude has some effects on the flow field, it has no significant effect on the value of the aerodynamic derivative. The influence of oscillation frequency on dynamic characteristics is also not obvious. And we hope that these conclusions would provide some technical guidelines and reference for the future research and development of similar vehicle in China.