我国未来探月工程任务对材料需求展望

月球是深空探测的热点,也是美、欧等国家航天技术的竞技场。随着我国"绕、落、回"探月工程的成功实施,建设月球基地和月球空间站已成为新任务的论证热点,这将对材料提出新的需求和发展方向。本文在概述月球环境对航天材料的影响的基础上,分析我国未来探月工程的任务难点,并从轻量化结构、高效热管理、先进热防护、低温润滑、防尘、缓冲吸能等不同角度提出了探月工程对航天材料的新需求,最后给出了后续如何发展探月工程新材料新技术的建议。     

Influence of lunar regolith compressibility on sampling performance of thick wall spiral drills

A 2 m class robotic drill was sent to the Moon and successfully collected and returned regolith samples in late 2020 by China. It was a typical thick wall spiral drill (TWSD) with a hollow auger containing a complex coring system to retain subsurface regolith samples. Before the robotic drill was launched, a series of laboratory tests were carried out to investigate and predict the possible drilling loads it may encounter in the lunar environment. This work presents how the sampling performance of the TWSD is affected by the regolith compressibility. Experiments and analysis during the drilling and sampling process in a simulated lunar regolith environment were conducted. The compressibility of a typical lunar regolith simulant (LRS) was measured through uni-directional compression tests to study the relationship between its inner regolith stress and bulk density. A theoretical model was established to elucidate the cutting discharge behavior by auger flights based on the aforementioned relationship. Experiments were conducted with the LRS, and the results show that the sampling performance is greatly affected by the flux of the drilled cuttings into the spiral flight channels. This work helped in scheduling reasonable drilling parameters to promote the sampling performance of the robotic drill in the Chinese Chang'E 5 mission.     

地外天体着陆巡视探测自主智能技术进展

以月球、火星和小行星等地外天体着陆巡视探测任务为背景，对自主智能技术的发展现状、应用情况与未来趋势进行了分析研究。回顾了目前国内外地外天体着陆巡视探测任务的实施情况；从导航定位与环境感知、轨迹优化与制导控制、自主探测与路径规划、故障诊断与自主处理等四个方面，阐述了该领域自主智能技术的研究现状，并对未来发展态势进行了展望。     

Autonomous navigation for lunar final approach based on gravity gradient measurements

Lunar final approach navigation is critical for pin-point lunar landing in future missions. This study investigates the use of lunar gravity gradient measurements for autonomous navigation of a lunar probe during the final approach phase. As the spacecraft approaches the Moon, the strength of gravity gradient signals improves. A spaceborne gravity gradiometer can precisely measure local gravity gradients, and the latest lunar gravity model GL1500E is used to provide reference values. The employed truncation degree and order of the gravity model are increased stepwise considering the decreasing altitude of the spacecraft in order to reach a compromise between computational costs and model accuracy. An iterative Kalman filter is developed for coupled orbit and attitude estimation using gravity gradient measurements and attitude quaternions obtained from star sensors. A simulated spacecraft with a gradiometer noise level of 0.01 E is considered. Simulation results show that the spacecraft’s position converges rapidly and achieves an accuracy of less than 100 m at the last epoch.     

Ground-based investigations on phase-moving phenomenon with space sublimation cooling for lunar exploration missions

The lunar surface is a typical vacuum environment, and its harsh heat rejection conditions bring great challenges to the thermal control technology of the exploration mission. In addition to the radiator, the sublimator is recommended as one of the promising options for heat rejection. The sublimator makes use of water to freeze and sublimate in a porous medium, rejecting heat to the vacuum environment. The complex heat and mass transfer process involves many physical phenomena such as the freezing and sublimation phase change of water in the porous medium and the movement of the phase-change interface. In this paper, the visualized ground-based experimental approaches of space sublimation cooling were presented to reveal the moving law of three-phase point and the growth phenomenon of ice-peak and icicle in microchannels under vacuum conditions. The visualized experiments and results prove that the freezing ice is divided into the porous ice-peak and the transparent icicle. As the sublimation progresses, the phase-change interface moves downward steadily, the length of the ice-peak increases, but the icicle decreases. The visualized experiments of space sublimation cooling in the capillary have guiding significance to reveal the sublimation cooling mechanism of water in the sublimator for lunar exploration missions.     

弱全局信息下月面超远距离保通行性移动规划

针对月面超远距离移动规划任务因缺乏精确全局信息而导致的规划路径可通行性不足问题，提出了月面道路拓扑网的构建设想及相应路径规划技术，凭借复杂道路网络的连通能力确保巡视器超远距离规划路径的可通行性。首先进行月面道路拓扑网的设计方法研究，分别提出了基于滑动最优泊松采样算法的网络节点设计方法和基于均匀领邻网络拓扑模型网络结构设计方法，使月面道路网网络节点分布均匀、密度适中且覆盖完整，网络连接合理且各路径尽量远离障碍区域。然后进行基于月面道路拓扑网的超远距离移动规划研究，分析了基于月面道路拓扑网路径规划技术的概率完备性和整体可通行概率，并提出了基于月面道路拓扑网的K优路径规划方法，通过道路网的连通性来提高超远距离移动探测任务的整体可通行概率。最后以阿波罗两次登月任务的着陆点之间进行超远距离转移任务为仿真场景，验证了本方法的有效性。