【摘要】 为使航天器在星际航行中实现轨道机动且有效节省燃料,建立了AGA(aero-gravity assist)机动的动力学方程和性能指标函数,给出终端约束和路径约束条件,用拟谱法将连续两点边值问题转换为等价的非线性规划问题,应用SNOPT软件求出飞行器最大化日心速度和最小化日心速度对应的最优轨迹,最后对轨迹优化算法进行了仿真,得出在热流速率峰值约束下的最优轨迹变化规律.结果表明,节点数为40时,最大速度偏差为0.009 m/s,满足收敛精度要求;与引力辅助轨道机动相比,极大化日心速度增大了8.02%,极小化日心速度减小了32.26%,相应偏转角分别增加了42.74°和68.40°;与无热流速率约束情况相比,最大热流速率峰值为500 W/(cm2.s)时,飞行器进入大气的深度、日心速度和偏转角分别减少6.35 km、93 m/s和6°.更多还原

【Abstract】 In order to achieve the orbit maneuver and save the fuel consumption in the space travel mission of spacecrafts,the dynamic equations and performance index functions of aero-gravity assist(AGA) maneuver were established under the terminal constraints and path constraints.The continuous two-point boundary value problem was converted to the equivalent nonlinear programming problem using the pseudospectral method,and the optimal trajectories corresponding to the maximum and minimum heliocentric velocities of the spacecraft were obtained with SNOPT software.Finally,a simulation was made for the trajectory optimization algorithm,and the variation of optimal trajectories under the peak constraint of heat flow rate was obtained.The results show that the maximum velocity deviation is 0.009 m/s when the number of nodes is 40,which satisfy the convergence precision demand.In the AGA maneuver,the maximum heliocentric velocity increases by 8.02%,the minimum heliocentric velocity reduces by 32.26%,and the corresponding deflection angles increase by 42.74° and 68.40°,respectively,when compared with those in the gravity-assist orbit maneuver.When the peak heat flow rate is 500 W/(cm2·s),the depth of spacecraft into the atmosphere,the heliocentric velocity,and the deflection angle reduce 6.35 km,93 m/s,and 6°,respectively,compared with those without heat flow rate constraint.更多还原