月球着陆器辐射器安装与散热关系分析

根据月球着陆器初步构型方案,辐射器可采取平行平坦月表安装和倾斜安装两种方式,安装方式不同时辐射器将面临不同的外热流环境。文章通过分析辐射器采取不同安装方式时的散热能力,对辐射器安装方式进行了优化设计。     

卫星跟踪卫星应用于月球重力场探测的模拟研究

月球卫星跟踪卫星技术作为月球和行星重力场探测的一种解决方案已经初步研究和讨论。文章引入已有的解析方法在理论上分析卫星间精密测距与月球重力场信号的频率响应关系，并通过模拟计算，以分析月球卫星跟踪卫星方法应用于月球重力场探测的可行性和恢复重力场的能力。由于月球卫星跟踪卫星方法是目前解决远月面重力探测最有潜力的方法之一，且已为一些月球探测计划采用，而我国的月球探测计划也同样面，临远月面探测的难题，文章的研究成果可为我国月球和行星重力场的探测提供参考。     

月球返回舱跳跃式再入弹道设计方法研究

不同于近地航天器返回地球,月球返回舱存在再入速度更高、大气和气动参数误差影响更大以及再入动力学耦合更强烈的特点。为缓解这些突出问题,降低月球返回舱所受到的冲击,对跳跃式再入弹道进行了研究,给出了跳跃式返回弹道的设计流程和算法,分析了不同再入角和航程约束下的弹道形态,并针对7 500 km航程可能出现的横向超调现象提出了3种解决方案。其中控制出口射面法引入了"预测-校正"思想,从根本上解决了自由飞行段可能出现的问题。数值仿真结果验证了弹道设计流程和算法的有效性。     

基于模糊理论的跳跃轨迹多目标优化设计

针对探月返回跳跃轨迹的多目标优化设计问题,提出了一种基于模糊理论的优化设计方法,并对非线性隶属度函数对优化结果的影响进行了研究.首先,将连续的无限维优化问题进行离散化,转化为非线性规划问题;其次,用隶属度函数将各个子目标进行模糊化,将多目标优化问题转化为求模糊判决隶属度函数的最大值问题;最后,求解经过模糊化的非线性规划问题.分析了探月返回跳跃轨迹的特性,表明模糊多目标优化更能体现决策者的偏好.构造了具有不同凹凸性、不同形状的非线性隶属度函数,比较了它们对优化结果的影响,结果表明隶属度函数影响多目标模糊优化结果的首要因素是隶属度函数的凹凸性.     

Hybrid uncertainty-based design optimization and its application to hybrid rocket motors for manned lunar landing

Design reliability and robustness are getting increasingly important for the general design of aerospace systems with many inherently uncertain design parameters. This paper presents a hybrid uncertainty-based design optimization (UDO) method developed from probability theory and interval theory. Most of the uncertain design parameters which have sufficient information or experimental data are classified as random variables using probability theory, while the others are defined as interval variables with interval theory. Then a hybrid uncertainty analysis method based on Monte Carlo simulation and Taylor series interval analysis is developed to obtain the uncer-tainty propagation from the design parameters to system responses. Three design optimization strategies, including deterministic design optimization (DDO), probabilistic UDO and hybrid UDO, are applied to the conceptual design of a hybrid rocket motor (HRM) used as the ascent propulsion system in Apollo lunar module. By comparison, the hybrid UDO is a feasible method and can be effectively applied to the general design of aerospace systems.     

Properties of transit trajectory in the restricted three and four-body problem

In the restricted three-body problem if the Jacobi constant is just below the value corresponding to Lagrangian point only a little neck exists around the equilibrium point and capture trajectories are indicated as low-energy. Capture properties depend on the dynamics around these critical points and qualitative results can be obtained using linearized systems. In this paper, to study transit trajectory properties in the restricted three and four-body problem, the Earth–Moon–Sun–Satellite system is considered as example and studied using different models. In the circular restricted three-body problem (Earth–Moon–Satellite), transit, non transit and asymptotic trajectories, are easily identified by using the principal reference frame. Dynamics around Lagrangian point are then studied introducing the Moon eccentricity into the elliptical restricted three-body model. A preferential region for transit orbit is individuated and studied as a function of eigenvalue properties. To introduce the Sun effect, the bi-circular four-body model is considered and dynamics around Lagrangian points studied as a function of angular distance between Earth–Sun and Earth–Moon line. Finally, results obtained in the elliptical three-body model and bi-circular four-body model, are compared with numerical simulations using real Sun–Moon–Earth ephemeris.     

一种基于概率路线图的月球巡航车路径规划算法

为提高月球巡航车自主探测时的安全，提出一种基于概率路线图(Probabilistic Roadmap, PRM)的改进路径规划算法.该算法基于距离变换地图，改善PRM算法的采样方式，控制采样点远离障碍物，使规划的路径远离障碍物，避免紧贴障碍物前进的危险情况，提高了月球巡航车自主探测过程中的安全程度.为评估路径的安全性，提出安全警戒系数和最小安全警戒系数两个安全指标，并在月球表面仿真环境下对A*，PRM和改进的PRM算法生成的路径进行安全评估.结果表明改进的PRM算法相较于A*算法，安全警戒系数和最小安全警戒系数分别提升了2.20 m，1.00 m；相较于PRM算法，安全警戒系数和最小安全警戒系数分别提升了1.68 m，1.00 m.改进的PRM算法不局限于月球巡航车的路径规划，还可以应用于对路径安全性要求较高的探索机器人和自动驾驶汽车.     

月面无人自主采样返回任务动力下降点确定及验证

动力下降点确定是实施月面软着陆的重要环节，是多系统间复杂迭代的过程，涉及轨道设计、制导律设计、着陆目标的采样区确定、着陆及起飞安全分析。其设计结果直接影响了最终着陆点的位置和着陆过程的着陆安全，也间接影响采样安全和采样工程目标的实现结果。针对嫦娥五号在实施月面软着陆前确定动力下降点的任务需求，提出了通过多次轨道控制与最优标称制导轨迹搜索联合控制策略的动力下降点确定方法。首先，根据月面无人自主采样返回任务设计总结了动力下降点确定原理和约束条件；然后，详细论述了月面无人自主采样返回任务软着陆过程动力下降点确定方法；最后，通过嫦娥五号在着陆前主要的几次轨控实施结果分析了其对动力下降点的影响，同时综合了着陆区地形分析及着陆、起飞安全性分析，对动力下降点进行确定并根据最终在轨飞行结果进行验证。验证结果表明，基于“逐次逼近寻优方法”的月面软着陆环节动力下降点的确定方法有效，可以为后续地外天体软着陆等任务提供参考和借鉴。     

载人登月着陆器奔月窗口搜索方法

对环月轨道共面交会的载人登月任务中,着陆器(LM)奔月零窗口与轨道参数精确快速设计方法进行了研究。任务采用人货分离奔月模式,着陆器于载人飞船到达环月轨道前抵达环月共面交会轨道,着陆器近月点一次共面减速完成近月制动。提出一种三层快速精确奔月窗口搜索方法:第一层采用地心二体轨道理论解析计算月窗口及奔月轨道参数初值,作为正确性基本参考;第二层采用改进的双二体解析动力学模型求解月窗口内奔月轨道参数变化规律;第三层采用高精度轨道动力学模型和SQP_Snopt优化求解奔月零窗口及轨道参数精确解。仿真结果表明,本文提出的三层逐级奔月窗口搜索方法能快速精确求解载人登月任务中着陆器奔月窗口及精确轨道参数,也揭示了影响着陆器奔月窗口的主次因素和规律,为中国未来载人登月工程提供参考。     

Sulfur “concrete” for lunar applications – Sublimation concerns

Melting sulfur and mixing it with an aggregate to form “concrete” is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO₂ powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.