升力式航天器再入最优轨迹研究

从无量纲飞行器质点运动方程出发，引入了能量参数对运动方程进行推导，使得运动方程和优化问题易于处理．通过将气动力假设为能量参数的分段连续线性函数。并且采用Runge-Kutta数值计算方法，将轨迹优化问题转化为多维非线性规划问题．应用广义乘子法对其进行数值求解．针对给定不同最大航迹角的2种情况，获得了总加热量最小，满足终端要求以及过载、动压、热流约束的最优轨迹，分析了返回最优轨迹的特点。

OPTIMAL REENTRY TRAJECTORY OF LIFT-BODY SPACECRAFT

Based on the standard point mass dimensionless equations of motion over a spherical, nonrotating Earth, the negative specific energy was used in stead of time in the motion equations. The equations and the optimization problem were simplified. The control variable, namely darg and lift were treated as continuous, piecewise linear functions of the negative specific energy. By the Runge Kutta methods, the trajectory optimization problem was transferred to nonlinear programming, which was solved by Generalized Lagrange Multiplier. The optimal entry trajectorie of minimal accumulated heat load with different maximum flight path angle was gained to satisfy the constraints of heating rate, dynamic pressure, load factor and terminal conditions.