【作者】 苏杭；

【导师】 张世杰；

【作者基本信息】 哈尔滨工业大学 ， 航天工程， 2012， 硕士

【摘要】 月球探测器返回舱以接近第二宇宙速度再入大气层，再入速度较高，会面临气动过载和热流密度大等问题。我国探月三期月球采样返回任务以及美国新一代猎户座乘员探测飞行器（CEV）等现代月球探测任务均采用跳跃式再入轨道，以提高航程调整能力，减少再入过载和热流密度。因此，本文以上述跳跃式返回任务为背景，开展跳跃式再入动力学建模与仿真、轨迹优化以及制导律设计等相关问题研究，取得了如下研究成果。针对探月飞船返回再入问题，在低升阻比飞船再入动力学模型及其无量纲化模型基础上，开发了跳跃式轨迹再入动力学与制导数学仿真程序。在不同的再入角、再入速度、倾侧角等初始再入参数和控制量条件下进行了大量的仿真研究，分析了上述各参数对于飞行轨迹及再入性能的影响程度，为跳跃式再入初始条件的选取及轨迹优化等问题提供了参考。根据跳跃式再入约束条件复杂、初值选取困难的特点，跳跃式再入轨迹优化采用了基于高斯伪谱法的、“由可行解到最优解”的串行优化策略。针对不同的场景，以不同的优化目标对再入轨迹进行了优化仿真，给出了具有一定工程参考价值的优化轨迹。为解决跳跃式再入航程较大、开普勒飞行段无法施控等问题，提出了基于数值预测校正（Numerical Predictor-Corrector，NPC）的再入制导算法。该方法采用数值积分对再入动力学方程进行运算求解，通过改变控制量实现对预测落点与标称落点偏差的校正，具备在线轨迹规划能力，能够满足跳跃式再入制导精度需求。对不同再入初始条件进行数学仿真以验证本文所提出的制导方法的可行性和鲁棒性。更多还原

【Abstract】 The reentry speed of lunar-return vehicle is close to the second cosmic velocity, thevehicle fly in this speed will be faced with high overload and heat flux. The lunarsample return mission in the third phase of China’s lunar exploration program as well asthe USA’s next-generation Orion Crew Exploration Vehicle (CEV) lunar exploremission are both going to adopt skip reentry trajectory in order to enhance the ability ofadjusting a large downrange, and reduce the peak of overload and heat flux. Therefore,this thesis studied the reentry dynamic characteristics, reentry trajectory optimizationapproaches and reentry guidance based on lunar return missions. The main resultsachieved in this dissertation are summarized as follows:To simulate a spacecraft’s entry flight, the dimensionless equations ofthree-dimensional motion for a point mass about a rotating Earth are integrated. A largenumber of simulations were done to analyze the impacts of the initial reentry parameterand the control ones on the reentry trajectory, which provides a reference for theselection of reentry initial conditions;In considering of the complexity of constraints and difficulty of choosing the initialvalue, a serial optimization strategies “from feasible solution to optimal solution” basedon Gauss Pseudospectral Method (GPM) was adopted to approach a reentry trajectoryoptimization. Reentry trajectories in different scenarios with different optimizationobjectives were simulated, the simulation results has certain reference value forengineering;A numerical predictor-corrector (NPC) method for trajectory planning andclosed-loop guidance of low lift-to-drag (L/D) ratio vehicles during the skip entry phaseof a lunar-return mission is presented to adjust the large downrange and solve theproblem of. The strategy calls for controlling the trajectory by modulation of themagnitude of the vehicle’s bank angle. A number of issues are identified and addressedthat are critical in closed-loop implementations. Extensive3DOF dispersion simulationsare performed to evaluate the performance of the proposed approach, and the resultsdemonstrate very reliable and robust performance of the algorithm in highly stressfuldispersed conditions.更多还原