再入飞行器沉浮特性近似解析及应用

摘要

For the hypersonic reentry vehicle adopting the equilibrium glide-based numerical or analytical predictor-corrector guidance,the phugoid oscillation of the reentry trajectory is prone to be caused at the transition point from the initial descent to the equilibrium glide or by large prediction deviations.With the increase of the lift-to-drag ratio of reentry vehicles under research in recent years,the phugoid oscillation becomes more noticeable to cause researchers to re-examine the hypersonic phugoid characteristic.A concise approximate analytical solution for intuitively expressing the dominate factors for hypersonic phugoid characteristic of reentry vehicles is derived,according to three order longitudinal flight dynamics equations and the equilibrium glide condition.It is found that the hypersonic phugoid damping characteristic mainly depends on the ratio of flight speed to orbital speed and the phugoid correction factor,rather than on the atmospheric density-gradient parameter considered by previous researchers.A controller is designed to eliminate the trajectory oscillation by using the approximate relation derived,further improving the equilibrium glide based numerical or analytical predictor-corrector guidance.Effectiveness of the method is verified by the simulation results.%采用基于平衡滑翔的数值或解析预测-校正再入制导方法的再入飞行器,从初始下降段到平衡滑翔段过渡或出现较大预测偏差时易产生沉浮振荡,且随着近年来所研究飞行器升阻比的增加,沉浮振荡更加明显,从而引起了研究者对高超声速沉浮特性的重新审视.首先,通过三阶纵向动态方程及平衡滑翔条件推导出了形式简洁、能直观表达主要影响因素的再入飞行器高超声速沉浮特性近似解.在此基础上,分析发现高超声速沉浮阻尼特性随高度的变化规律主要由轨道速度比和沉浮修正参数主导,澄清了以往对大气密度梯度参数影响的猜测.最后,推导出再入轨迹振荡抑制器设计的近似解析关系,进一步完善了基于平衡滑翔的数值或解析预测-校正再入制导方法,仿真验证表明该方法能够有效抑制再入轨迹的沉浮振荡.