Design and experimental performance verification of a thermal property test-bed for lunar drilling exploration

Chinese Chang'e lunar exploration project aims to collect and return subsurface lunar soil samples at a minimum penetration depth of 2 m in 2017. However, in contrast to those on the Earth, automated drilling and sampling missions on the Moon raise the risk of burning bits.Test-beds are required for testing the thermal properties of drill tools in a lunar environment. In this paper, a novel temperature measuring method based on thermocouples and a slip ring was proposed. Furthermore, a data acquisition system for a drilling process was designed. A vacuous,cryogenic, and anhydrous soil environment simulating the lunar surface was established. A drilling test-bed that can reach a depth of 2.2 m was developed. A control strategy based on online monitoring signals was proposed to improve the drilling performance. Vacuum and non-vacuum experiments were performed to test the temperature rising effect on drill tools. When compared with the non-vacuum experiment, the vacuum temperature rise resulted in a 12 °C increase. These experimental results provide significant support for Chinese lunar exploration missions.     

月球钻取采样机构的钻杆结构与运动参数分析

针对月球钻取式自动采样机构空心外螺旋钻杆取样过程,分别建立了月壤内聚力和月壤内摩擦系数随月壤深度变化的数学模型,建立了钻进过程中钻杆运动参数(钻进速度和钻杆转速)与钻杆结构参数(钻杆螺旋升角、外径、槽宽比和螺旋槽深等)之间的关系。建模过程考虑了月壤物理和机械特性随钻进深度变化特性、钻杆钻进牵连速度及月壤微元相互间的抗剪性,使得钻杆参数符合月球钻取采样的实际工况。对模型进行了验证,利用该模型开展了钻杆结构参数对运动参数的影响分析,给出了钻杆结构参数对钻杆运动参数的影响规律,获得了钻杆结构参数的最佳取值范围。以钻杆转速与钻进速度比最小为优化目标,以结构参数为设计变量,基于遗传算法对钻杆结构参数进行了优化,优化后的钻杆转速与转进速度比降低了13.8%。该优化结果降低了系统能耗,提高了钻取采样输月壤效率,可为钻取式自动采样机构的设计提供理论依据。     

阶梯钻钻削碳纤维复合材料的钻削力及孔质量

根据碳纤维复合材料制孔过程中产生的缺陷,自主磨制专用钻头——阶梯钻对碳纤维复合材料进行钻削实验,研究了在不同加工参数下阶梯钻钻削碳纤维复合材料的钻削力、孔出口质量、孔壁表面粗糙度,并与普通麻花钻头进行对比。结果表明:阶梯钻产生的钻削轴向力是麻花钻的一半,孔壁表面粗糙度值更小,孔出口没有明显的缺陷,阶梯钻适合钻削碳纤维复合材料。     

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.     

Astrobiology and habitability of Titan

Largest satellite of Saturn and the only in the solar system having a dense atmosphere, Titan is one of the key planetary bodies for astrobiological studies, due to several aspects. (i) Its analogies with planet Earth, in spite of much lower temperatures, with, in particular, a methane cycle on Titan analogous to the water cycle on Earth. (ii) The presence of an active organic chemistry, involving several of the key compounds of prebiotic chemistry. The recent data obtained from the Huygens instruments show that the complex organic matter in Titan’s low atmosphere is mainly concentrated in the aerosol particles. The formation of biologically interesting compounds may also occur in the deep water ocean, from the hydrolysis of complex organic material included in the chrondritic matter accreted during the formation of Titan. (iii) The possible emergence and persistence of Life on Titan. All ingredients which seem necessary for Life to appear and even develop – liquid water, organic matter and energy – are present on Titan. Consequently, it cannot be excluded that life may have emerged on or in Titan. In spite of the extreme conditions in this environment life may have been able to adapt and to persist. Many data are still expected from the Cassini-Huygens mission and future astrobiological exploration mission of Titan are now under consideration. Nevertheless, Titan already looks like another world, with an active organic chemistry, in the absence of permanent liquid water, on the surface: a natural laboratory for prebiotic-like chemistry.     

Drilling load modeling and validation based on the filling rate of auger flute in planetary sampling

Some type of penetration into a subsurface is required in planetary sampling. Drilling and coring, due to its efficient penetrating and cuttings removal characteristics, has been widely applied in previous sampling missions. Given the complicated mechanical properties of a planetary regolith, suitable drilling parameters should be matched with different drilling formations properly. Otherwise, drilling faults caused by overloads could easily happen. Hence, it is necessary to estab-lish a drilling load model, which is able to reveal the relationships among drilling loads, an auger's structural parameters, soil's mechanical properties, and relevant drilling parameters. A concept for the filling rate of auger flute (FRAF) is proposed to describe drilling conditions. If the FRAF index under one group of drilling parameters is less than 1, this means that the auger flute currently removes cuttings smoothly. Otherwise, the auger will be choked with compressed cuttings. In dril-ling operations, the drilling loads on the auger mainly come from the conveyance action, while the drilling loads on the drill bit primarily come from the cutting action. Experiments in one typical lunar regolith simulant indicate that the estimated drilling loads based on the FRAF coincide with the test results quite well. Based on this drilling load model, drilling parameters have been opti-mized.     

三种钻头钻削CFRP轴向力的时变曲线及预测

采用二刃、三刃双锋角钻头和圆弧形钻头钻削CFRP单向板,研究钻削过程中轴向力时变曲线的特征,并探索用预测轴向力时变曲线上的关键拐点的方法来构建预测轴向力时变曲线模型。结果表明:三刃双锋角钻头的轴向力时变曲线最为稳定,钻削过程最为稳定;轴向力最大的是三刃双锋角钻头,其次是圆弧形钻头,最小的是二刃双锋角钻头,说明二刃双锋角钻头适合钻削CFRP;用预测轴向力时变曲线上的关键拐点的方法构建的轴向力时变曲线可以很好地预测双锋角钻头轴向力时变曲线。     

阶梯钻钻削钛合金实验

采用自主磨制的阶梯钻对钛合金进行钻削实验,并与普通麻花钻进行对比。分析了不同加工参数下的钻削力、切屑形态、孔径、孔壁表面粗糙度以及孔出入口毛刺。实验结果表明:钻削力随着主轴转速的增大而减小,随着进给量的增大而增大。相比普通麻花钻,阶梯钻产生的钻削力更小,切屑尺寸更小,排出顺畅,孔径值接近于钻头直径,孔壁表面粗糙度值更小,孔出入口毛刺少。     

双锋角钻头钻削碳纤维增强树脂基复合材料研究

采用双锋角钻头和普通麻花钻对T700碳纤维复合材料(CFRP)进行钻削试验,从钻削轴向力、制孔出口质量和表面粗糙度等方面分析双锋角钻头在不同加工参数下制孔特点,并与普通麻花钻进行对比。试验结果表明:与普通麻花钻对比,双锋角钻头钻削CFRP时钻削轴向力减小约20%,制孔出口质量更好,孔壁的表面粗糙度值减小,体现优异的切削性能更适合CFRP的制孔加工。     

Simulation and analysis of asteroid force closure anchoring performance based on discrete element method

Asteroid exploration is significant for studying the origin of the solar system, establishing planetary defenses, and alleviating the resource crisis of the Earth. Asteroid anchoring is the basis of in-situ exploration and resource development and utilization. Therefore, the performance of asteroid force-closure anchoring is investigated using the discrete element method. The micro parameters of the simulated materials are calibrated with angle of repose and uniaxial compression experiments, based on which the regional modeling method is adopted to establish the anchoring discrete element model. Asteroid anchoring experiments are conducted on a self-developed microgravity simulation platform to verify the accuracy of the simulation model. The asteroid anchoring simulations are performed to investigate the influence of external force on the anchoring performance. The analysis of anchoring force varying with time and the interaction between the anchor and regolith particles reveals the influence mechanism of external force direction on the anchoring performance. The external force direction affects the critical anchoring force by influencing the failure of the force-closure structure. The comprehensive analysis of simulation results clarifies the variation of the critical anchoring force with the external forces. Finally, a stable anchoring region is established, beneficial for asteroid anchoring device design.     

阶梯钻钻削碳纤维复合材料-钛合金叠层板刀具磨损试验研究

采用自主磨制的阶梯钻对碳纤维复合材料/钛合金叠层板进行钻削磨损试验,并与普通麻花钻进行对比,分析了阶梯钻刀具磨损过程。实验结果表明:阶梯钻主要磨损区域为横刃、第一后刀面和第二后刀面,其中第二后刀面磨损最为严重,相比普通麻花钻,阶梯钻产生的钻削力更小,阶梯钻刀具寿命远远高于普通麻花钻。     

刀具材料对运载火箭叠层厚板高速制孔影响的实验研究

针对当前厚度大于10mm的运载火箭铝合金叠层板在高速制孔过程中存在的钻头折断、噪音、毛刺等问题,开展了刀具材料对运载火箭叠层厚板钻孔影响的实验研究。从孔径、毛刺和切削力等方面分析含钴高速钢、硬质合金和涂层硬质合金3种刀具材料对制孔的影响。结果表明:相比于硬质合金钻头,含钴高速钢麻花钻尽管钻削力较高,但具有钻孔数量多、产生的毛刺高度小、出入口较为光整、细小毛刺少、刀具发生磨损而不断裂等优点,因此,更适合进行2219铝合金叠层厚板的制孔。     

CFRP复合材料超声振动套孔分层抑制机理分析

针对碳纤维增强复合材料在传统钻孔过程易出现分层缺陷,采用金刚石空心套刀和超声振动加工技术进行了CFRP超声振动套孔分层抑制机理分析。理论分析了传统麻花钻钻孔与金刚石套刀普通套孔过程的分层机理及评价,超声振动套孔对分层抑制的机理,并且进行了实验验证。结果表明:相比于CFRP普通套孔,超声振动套孔能够有效提高套刀切削性能和排屑效果,降低钻削力12.5%～19.2%,抑制切屑粉尘黏附套刀和料芯堵塞套刀,抑制CFRP分层缺陷形成,改善孔表面质量。     

Conversations: with Carl Pilcher [interview by Johan Benson

An interview with Carl Pilcher, science program director for solar system exploration at NASA, examines NASA's past, present, and planned missions to explore the solar system. Specific questions relate to the status of current and planned missions, science results of the Pathfinder mission to Mars, cooperation with the Japanese space agency, the status of the search for extraterrestrial life in solar system meteoroids and asteroids, mission size for more in-depth exploration, reports of water on the moon, and the exploration of near-Earth objects.     

Communicating across the solar system

The next chapter in our ongoing quest for discovery began in the last half of the 20th century, with the initiation of robotic exploration of our solar system. In less than fifty years, we have broken free of Earth's gravity and flown spacecraft to every planet in the solar system except Pluto. The ultimate goal of this exploration is to establish a virtual (and, perhaps, someday, an actual) human presence throughout the solar system. Clearly, communications is one of the central elements of creating such a virtual presence, and also one of the biggest technical challenges in planetary exploration. Transmit performance is characterized by the product of antenna gain and transmitter power, while receive performance scales with the ratio of aperture effective area to system noise temperature. A number of key communications technology advances have enabled our planetary exploration to date, and future technology will open the door to new vistas in space exploration     

航天器太阳圆面速度差/太阳视方向组合导航

针对航天器，尤其是深空探测器的自主导航问题，提出了一种新的太阳圆面速度差天文量测信息，该信息利用太阳的较差自转所造成的太阳圆面各点速度不同的特性，是探测器当前位置的函数，其几何本质是一个探测器的位置圆锥。在此基础上，基于太阳圆面速度差和太阳视方向互补的特性，提出了一种太阳圆面速度差/太阳视方向组合导航新方法，将太阳圆面速度差与太阳视方向2种量测量结合起来，实现了量测量之间的优势互补，进一步提高了导航性能。以太阳探测器为例进行了仿真，仿真结果表明相比较于单独用太阳圆面速度差或太阳视方向的导航方法，基于太阳圆面速度差/太阳视方向的组合导航方法精度分别提升了10.2%和16.0%。此外，还分析了光谱仪精度、采样周期和光谱仪数量对导航性能的影响，为深空探测自主导航提供了新的理论与方法。     

C/E 复合材料“以磨代钻冶制孔工艺

为了提高C/E复合材料构件制孔加工质量,以C/E复合材料为研究对象,提出"以磨代钻"制孔新工艺,并研制了电镀金刚石刀具.与传统硬质合金刀具钻孔工艺进行对比试验,结果表明:金刚石刀具钻削轴向力降低30%-50%、刀具耐用度提高3-5倍、缺陷显著减少,更适合C/E复合材料钻孔加工.     

八面钻超声振动钻削钛合金出口毛刺形成机理

钛合金在传统麻花钻常规钻孔后,会产生较大的孔出口毛刺,这将导致孔出口去毛刺困难且影响紧固件装配质量。本文引入一种八面钻新刃型刀具,并利用超声振动钻削技术,进行了八面钻超声振动钻削钛合金出口毛刺形成的基础理论和试验研究。理论分析了普通钻削和超声振动钻削的出口毛刺形成过程以及超声振动钻削的出口毛刺降低机理,同时试验验证了超声振动钻削的出口毛刺降低效果。结果表明:相比于钛合金普通钻削,超声振动钻削极大地提高了钻头刀具的切削能力,分别降低了钻削力16%~20%、切削温度18%~21%和出口毛刺高度82%~89%,有效降低了装配过程的去毛刺困难和生产成本。     

碳纤维复合材料/钛合金叠层钻孔工艺优化

在不同的工艺参数下用硬质合金麻花钻分别对碳纤维复合材料板和碳纤维复合材料板/钛合金叠层板进行钻孔,对钻孔过程用Abaqus有限元软件进行三维仿真,对比仿真和试验结果的轴向力和制孔效果。结果表明,在保证制孔的质量的前提下,选取合理的工艺参数,得到叠层材料制孔的工艺参数的优化结论。     

Present needs,capabilities, and future prospects in rocket technology for space research

The paper is a review of the past, present, and future of rocket technology, relating these to the propulsion requirements for exploration of the solar system. It reviews the U.S.A. approach to planning its launch-vehicle programs for space exploration, covers the present capabilities of the U.S.A. family of launch vehicles, and discusses some technology possibilities for future propulsion systems.