Fundamental Study on Response Properties of Structures Constructed on Lunar Regolith

The Artemis Program, for constructing the lunar base, is in progress. How to design and construct architectural and civil engineering structures in the lunar environment has become an important issue. The lunar surface is covered with soft sand, called regolith, and it is required to protect lunar bases and structures, as well as internal precision equipment, against vibrational disturbances such as moonquakes and meteorite collisions. Therefore, in this study, the static and cyclic triaxial compression tests of the regolith simulant were conducted. The reference strain and equivalent damping factor of the regolith simulant were smaller compared to sandy soil on Earth. In addition, a shaking table test using model specimens was conducted on the response properties of regolith ground alone and structures set on regolith ground. The buried foundation and pile foundation notably suppressed the horizontal response attributed to the rocking component compared to a direct foundation.

Simulation Research on the Effect of Spreading Process Parameters on the Quality of Lunar Regolith Powder Bed in Additive Manufacturing

Lunar surface additive manufacturing with lunar regolith is a key step in in-situ resource utilization.The powder spreading process is the key process,which has a major impact on the quality of the powder bed and the precision of molded parts.In this study,the discrete element method(DEM)was adopted to simulate the powder spreading process with a roller.The three powder bed quality indicators,including the molding layer offset,voidage fraction,and surface roughness,were established.Besides,the influence of the three process parameters,which are roller’s translational speed,rotational speed,and powder spreading layer thickness on the powder bed quality indicators was also analyzed.The results show that with the reduction of the powder spreading layer thickness and the increase of the rotational speed,the offset increased significantly;when the translational speed increased,the offset first increased and then decreased,which resulted in an extreme value;with the increase of the layer thickness and the decrease of the translational speed,the values for voidage fraction and surface roughness significantly reduced.The powder bed quality indicators were adopted as the optimization objective,and the multi-objective parameter optimization was carried out.The predicted optimal powder spreading parameters and powder bed quality indicators were then obtained.Moreover,the optimal values were then verified.This study can provide informative guidance for in-situ manufacturing at the moon in future deep space exploration missions.

Review on retrieval of lunar regolith thickness by active and passive microwave measurements

It is one of the important methods to retrieve lunar regolith thickness using active and passive microwave techniques.The retrieval of lunar regolith thickness is based on microwave radiation transfer process simulation in the regolith media.The lunar regolith model is first introduced,and the features of the involved physical parameters are indicated thereafter,such as dielectric constants,surface roughness,particle size and thermal grads of the lunar regolith.The time delay and the migration of the radar echoes from the different interfaces is the key problem for active microwave measurement.And the simulation of the microwave radiative transfer in the regolith media is the important technique for the passive microwave measurement.The important parameters and the physical mechanism for the two measurements are also presented.

On Modeling Drilling Load in Lunar Regolith Simulant

Drilling and coring, as effective ways to obtain lunar regolith along the longitudinal direction, are widely applied in the lunar sampling field. Conventionally, modeling of drill-soil interaction was divided into soil cutting and screw conveyance processes, ignoring the differences in soil mechanical properties between them. To improve the modeling accuracy, a hypothesis that divides the drill-soil interaction into four parts: cuttings screw conveyance, cuttings extruding, cuttings bulldozing, and in situ simulant cutting, is proposed to establish a novel model based on the passive earth pressure theory. An iterative numerical calculation method is developed to predict the drilling loads. A drilling and coring testbed is developed to conduct experimental tests. Drilling experiments indicate that the drilling loads calculated by the proposed model match well the experimental results. The proposed research provides the instructions to adopt a suitable drilling strategy to match the rotary and penetrating motions, to increase the safety and reliability of drilling control in lunar sampling missions.

Preparation and characterization of a specialized lunar regolith simulant for use in lunar low gravity simulation

Lunar in-situ resource utilization(ISRU)has been put on the agenda by many countries.Due to the special material nature and low gravity environment,the lunar regolith demonstrates significantly different behavior from terrestrial geomaterials.However,the systematic understanding of its geotechnical behavior is now seriously restricted by the scarcity of lunar regolith and the difficulty in simulating lunar gravity.A new lunar regolith simulant,termed as China University of Mining and Technology Number One(CUMT-1),has been developed to recover properties of the lunar regolith and simulate the lunar gravity by adopting the recently advanced geotechnical magnetic-similitude-gravity model testing(GMMT)method.The CUMT-1 simulant was prepared by reproducing the in-situ formation and fragmentation of the lunar matrix,which plays a key role in the irregular particle morphology.The mineralogical compositions,particle morphology and gradation,specific gravity,bulk density,void ratio,shear strength,and compressibility were determined.After quantifying the magnetization and magnetic-similitude-gravity characteristics,an application of the cone penetration resistance under low gravity was further given.The obtained results are compared to the values known for lunar regolith samples and other simulants,which demonstrates promising characteristics for use in geotechnical engineering-based and scientificbased applications,especially considering the influence of lunar gravity.

Influence of Temperature and Frequency on Microwave Dielectric Properties of Lunar Regolith Simulant

The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.

Noble Gases in the Lunar Regolith

The most fundamental character of lunar soil is its high concentrations of solar\|wind\|implanted elements, and the concentrations and behavior of the noble gases He, Ne, Ar, and Xe, which provide unique and extensive information about a broad range of fundamental problems. In this paper, the authors studied the forming mechanism of lunar regolith, and proposed that most of the noble gases in lunar regolith come from the solar wind. Meteoroid bombardment controls the maturity of lunar soil, with the degree of maturation decreasing with grain size; the concentrations of the noble gases would be of slight variation with the depth of lunar soil but tend to decrease with grain size. In addition, the concentrations of noble gases in lunar soil also show a close relationship with its mineral and chemical compositions. The utilization prospects of the noble gas \{\}\+\{\}\+3He in lunar regolith will be further discussed.

Endomycorrhizal Fungi and <i>Opuntia ficus-indica</i>Seed Germination on a Lunar Regolith Simulant

Endomycorrhizal fungi play an important role in the survival of plants on poor soils. Planting seeds into lunar soil at a lunar colony will be a challenge for seeds of any plant. The seeds will need a special microbial “tool kit” that will help them germinate and the young seedlings establish themselves. In this study, seeds of the prickly pear cactus, Opuntia ficus-indica, were chosen to examine the presence of fungus spores in the soil, inside the seeds and after germination in the rhizosphere, roots and other tissues of the young seedlings. The nutrient poor lunar regolith simulant JSC-1A was used as autoclaved or untreated growth medium. The mycorrhizal fungus Trichoderma viride was predominantly identified on the roots of new seedlings. This fungus also demonstrated the strongest effect on the germination rate of the seeds in comparison with other fungi isolated from the rhizosphere of Opuntia plants. T. viride was not detected within seeds and also not within seedlings, besides the root tips, whereas an arbuscular mycorrhizal Glomus species was seed-borne and present throughout most of the seedling. A close association between T. viride and a Glomus species associated with O. ficus-indica is demonstrated through light microscopic and electron microscopic images of the outside and inside root tips of the seedlings.

Laser welding study of vacuum sintered HUST-1 lunar regolith simulant

Efforts are underway to establish a permanent lunar base on the Moon. In situ lunar regolith is anticipated to be useful as a building material after sintering. However, sintering lunar regolith into a large-scale structure presents challenges. Therefore, the key to lunar construction lies in assembling multiple small-sized sintered modules into a stable, large-sized structure. This study explored the feasibility of welding the sintered HUST-1 lunar regolith simulant(HLRS) using a laser device and conducted experiments using lasers of varying power. The microstructure, mineral composition, element distribution, and shear strength of the welded joint were investigated. A few low-melting minerals were fused and vaporized during welding, leading to the generation of thermal decomposition gas. Furthermore, the welded joint exhibited numerous micro-cracks, pores, and bubbles,resulting in reduced weld shear strength. Finally, the influence of laser power on weld shear strength was investigated, revealing that the highest shear strength(15.69 N/cm) was achieved at a laser power of 1000 W. This study demonstrates the feasibility of laser welding of sintered HLRS for the first time, with potential applications in lunar base construction.

Development and characterization of the PolyU-1 lunar regolith simulant based on Chang’e-5 returned samples

Leading national space exploration agencies and private enterprises are actively engaged in lunar exploration initiatives to accomplish manned lunar landings and establish permanent lunar bases in the forthcoming years.With limited access to lunar surface materials on Earth,lunar regolith simulants are crucial for lunar exploration research.The Chang’e-5(CE-5)samples have been characterized by state-of-the-art laboratory equipment,providing a unique opportunity to develop a high-quality lunar regolith simulant.We have prepared a high-fidelity PolyU-1 simulant by pulverizing,desiccating,sieving,and blending natural mineral materials on Earth based on key physical,mineral,and chemical characteristics of CE-5 samples.The results showed that the simulant has a high degree of consistency with the CE-5 samples in terms of the particle morphology,mineral and chemical composition.Direct shear tests were conducted on the simulant,and the measured internal friction angle and cohesion values can serve as references for determining the mechanical properties of CE-5 lunar regolith.The PolyU-1 simulant can contribute to experimental studies involving lunar regolith,including the assessment of interaction between rovers and lunar regolith,as well as the development of in-situ resource utilization(ISRU)technologies.

Physical,mechanical and thermal properties of vacuum sintered HUST-1 lunar regolith simulant

Establishing a base on the Moon is one of the new goals of human lunar exploration in recent years.Sintered lunar regolith is one of the most potential building materials for lunar bases.The physical,mechanical and thermal properties of sintered lunar regolith are vital performance indices for the structural design of a lunar base and analysis of many critical mechanical and thermal issues.In this study,the HUST-1 lunar regolith simulant(HLRS)was sintered at 1030,1040,1050,1060,1070,and 1080℃.The effect of sintering temperature on the compressive strength was investigated,and the exact value of the optimum vacuum sintering temperature was determined between 1040 and 1060℃.Then,the microstructure and material composition of vacuum sintered HLRS at different temperatures were characterized.It was found that the sintering temperature has no significant effect on the mineral composition in the temperature range of 1030-1080℃.Besides,the heat capacity,thermal conductivity,and coefficient of thermal expansion(CTE)of vacuum sintered HLRS at different temperatures were investigated.Specific heat capacity of sintered samples increases with the increase of test temperature within the temperature range from-75 to 145℃.Besides,the thermal conductivity of the sintered sample is proportional to density.Finally,the two temperatures of 1040 and 1050℃were selected for a more detailed study of mechanical properties.The results showed that compressive strength of sintered sample is much higher than tensile strength.This study reveals the effects of sintering temperature on the physical,mechanical and thermal properties of vacuum sintered HLRS,and these material parameters will provide support for the construction of future lunar bases.

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 unidirectional 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.

3D-printed Lunar regolith simulant-based geopolymer composites with bio-inspired sandwich architectures

Over time,natural materials have evolved to be lightweight,high-strength,tough,and damage-tolerant due to their unique biological structures.Therefore,combining biological inspiration and structural design would provide traditional materials with a broader range of performance and applications.Here,the application of an ink-based three-dimensional(3D)printing strategy to the structural design of a Lunar regolith simulant-based geopolymer(HIT-LRS-1 GP)was first reported,and high-precision carbon fiber/quartz sand-reinforced biomimetic patterns inspired by the cellular sandwich structure of plant stems were fabricated.This study demonstrated how different cellular sandwich structures can balance the structure–property relationship and how to achieve unprecedented damage tolerance for a geopolymer composite.The results presented that components based on these biomimetic architectures exhibited stable non-catastrophic fracture characteristics regardless of the compression direction,and each structure possessed effective damage tolerance and anisotropy of mechanical properties.The results showed that the compressive strengths of honeycomb sandwich patterns,triangular sandwich patterns,wave sandwich patterns,and rectangular sandwich patterns in the Y-axis(Z-axis)direction were 15.6,17.9,11.3,and 20.1 MPa(46.7,26.5,23.8,and 34.4 MPa),respectively,and the maximum fracture strain corresponding to the above four structures could reach 10.2%,6.7%,5.8%,and 5.9%(12.1%,13.7%,13.6%,and 13.9%),respectively.

Printability and hardening performance of three-dimensionally-printed geopolymer based on lunar regolith simulant for automated construction of lunar infrastructure

Using an in situ lunar regolith as a construction material in combination with 3D printing not only reduces the weight of materials carried from the Earth but also improves the automation of lunar infrastructure construction.This study aims to improve the printability of a geopolymer based on a BH-1 lunar regolith simulant,including the extrudability,open time,and buildability,by controlling the temperature and adding admixtures.Rheological parameters were used to represent printability with different water-to-binder ratios,printing temperatures,and contents of additives.The mechanical properties of the hardening geopolymer with different filling paths and loading directions were tested.The results show that heating the printed filaments with a water-to-binder ratio of 0.32 at 80°C can adjust the printability without adding any additive,which can reduce the construction cost of lunar infrastructure.The printability of the BH-1 geopolymer can also be improved by adding 0.3%Attagel-50 and 0.5%polypropylene fiber by mass at a temperature of 20℃to cope with the changeable environmental conditions on the Moon.After curing under a simulated lunar environment,the 72-h flexural and compressive strengths of the geopolymer specimens reach 4.1 and 48.1 MPa,respectively,which are promising considering that the acceleration of gravity on the Moon is 1/6 of that on the Earth.

Experimental constraints on the formation of oxychlorine species by UV irradiation and mechanical pulverization on the lunar surface

Perchlorate and chlorate are present in various extraterrestrial celestial bodies throughout the solar system,such as Mars,the moon,and asteroids.To date,the origin mechanisms of perchlorate and chlorate on the Martian surface have been well-established;however,relatively little attention has been cast to airless bodies.Here,we experimentally investigated the potential oxidation mechanisms of chloride to chlorate and perchlorate,such as ultraviolet irradiation under H_(2)O-and O_(2)-free conditions and mechanical pulverization processes.Individual minerals,olivine,pyroxene,ilmenite,magnetite,TiO_(2)and anhydrous ferric sulfate,and lunar regolith simulants(low Ti,CLRS-1;high-Ti,CLRS-2)and their metallic iron(Fe^( 0))bearing counterparts were examined.We found that pulverization of dry matrix material-halite mixtures,even in the presence of O_(2),does not necessarily lead to perchlorate and chlorate formation without involving water.Under photocatalytic and H_(2)O and O_(2)-free conditions,olivine and pyroxene can produce oxychlorine(ClO_(x)^(−))species,although the yields were orders of magnitude lower than those under Martian-relevant conditions.Nanophase-Fe^(0)particles in the lunar regolith and the common photocatalyst TiO_(2)can facilitate the ClO_(x)^(−)formation,but their yields were lower than those with olivine.The oxides ilmenite and magnetite did not efficiently contribute to ClO_(x)^(−)production.Our results highlight the critical role of H_(2)O in the oxidation chloride to chlorate and perchlorate,and provide essential insights into the environmental influence on the formation of oxychlorine species on different celestial bodies.

Research on microwave radiation features and lunar regolith parameters inversion of the Rümker region

Chang'e-5(CE-5)mission is expected to land and sample in the Rümker region,north of the Oceanus Procellarum.To select optimal sampling points,the microwave radiation features in this mare unit are analyzed,and the dielectric constant and thickness of lunar regolith are retrieved based on Chang'e lunar microwave sounder(CELMS)data.According to the microwave brightness temperature(TB)maps,TB varying with frequency at noon and midnight are different,in which noon TB increases with frequency,but midnight TB does not follow this rule.Moreover,there are differences among TB distributions at the three higher frequencies,especially in the southern part.In addition,a great TB difference between noon and midnight can be seen in Rümker E that shows higher daytime temperature but lower nighttime temperature.The inversion results reveal that the dielectric constant is lower in the west and north,higher in the middle and east,and the largest value occurs in Rümker E.As for the regolith thickness,most areas are uniform and no more than 4 m,with the thickest and thinnest regolith appearing in the northwest and Rümker E,no less than 6 m and about 2.5 m,respectively.Considering the safety and operability of landing and sampling,the northwest with thick regolith is recommended,while the Rümker E should be eluded.

Synthesis and characterization of geopolymer from lunar regolith simulant based on natural volcanic scoria

In this study,a new GVS(Ground Volcanic Scoria)lunar regolith simulant was produced.The similarity between GVS and lunar soil was proved by comparison with Apollo lunar soil samples and other commercial lunar soil simulants.Then,GVS lunar regolith simulant was investigated as the source material for preparing geopolymer to produce building material for lunar colony construction.To study the possibility of preparing geopolymer from GVS lunar regolith simulant and the optimum activator formulation as well as the optimum curing conditions,alkaline activated GVS slurries with different mixing ratios based on an orthogonal test scheme were prepared.The geopolymer products based on GVS were characterized by flexural strength test,compressive strength test,X-ray fluorescence(XRF),X-ray diffraction(XRD),Fourier Transform Infrared Spectroscopy(FTIR),Scanning Electron Microscope coupled with Energy Dispersive Spectroscopy(SEM-EDS),29Si magic angle spinning-nuclear magnetic resonance(29Si MAS-NMR),and 27Al MAS-NMR.The experimental results indicate that changes in the mass ratio of sodium hydroxide and GVS and curing temperature have the most significant influence on the flexural strength and compressive strength,respectively.The GVS-based geopolymer can obtain the highest 28-day compressive strength and 28-day flexural strength up to 75.6 MPa and 6.3 MPa.Microstructural results imply that the changes of Si occurring in a variety of environments that explaining preliminarily about the reaction mechanism of GVS-based geopolymer.This study approves the feasibility of making a geopolymer derived from the GVS lunar regolith simulant and the potential utilization of geopolymer based on lunar regolith for construction of the lunar colony in future space exploration.

Influence of(FeO+Ti O_2) abundance on the microwave thermal emissions of lunar regolith

One of the essential controls on the microwave thermal emissions(MTE) of the lunar regolith is the abundance of Fe O and TiO_2, known as the(Fe O+Ti O_2) abundance(FTA). In this paper, a radiative transfer simulation is employed first to study the change in the brightness temperature(T_B) with FTA under a range of frequencies and surface temperatures. Then, we analyze the influence of FTA on the MTE of the lunar regolith using microwave sounder(CELMS) data from the Chang'E-2 lunar orbiter, Clementine UV-VIS data, and lunar samples recovered from the Apollo and Surveyor projects. We conclude that:(1) FTA strongly influences the MTE of the lunar regolith, but it is not the decisive control, and(2) FTA decreases slightly with depth. This research plays an essential role in appropriately inverting CELMS data to obtain lunar regolith parameters.

月球样品的中子活化分析技术研究

月球的起源是月球研究的核心问题。月球探测任务返回的数据和样品极大地提高了人类对地月系统的认知,同时也发现了更多未解之谜,亟待未来的探测任务和科学研究来解答。嫦娥五号月壤是我国首次地外天体采集返回的样品,也是继美国和苏联探月采样任务45年后人类再次获得的月球样品。鉴于月球样品的珍贵性和特殊性,利用先进技术开展其全元素含量的非破坏精准分析对于认识月球演化和月球资源就地开发利用具有重要的意义。依托大型核反应研究堆和加速器中子注量率优势,利用中子活化分析技术可实现月球样品中的全元素非破坏分析:1)仪器中子活化分析技术(INAA)可测量Na—U元素之间的60余种元素;2)瞬发γ中子活化分析技术(PGNAA)可补充测量INAA不适合测量的元素如H、B、C、N等;3)中子深度剖面分析技术(NDP)可测量样品近表面(微米级)聚变能源3He的浓度深度分布;4)缓发中子测量技术(DNC)可定量样品中痕量裂变核素如^(235)U和^(239)Pu,并结合INAA可测量238U/235U同位素比值;5)14 MeV快中子活化分析技术(FNAA)可测量INAA和PGNAA不灵敏或不适合测量的元素如O、Si、P等。因此,中子活化分析技术(NAA)可有效解决月球样品中全元素、非破坏和精准测量问题,为我国深空探测珍贵样品研究提供核分析技术支撑。

面向月面原位资源利用的嫦娥五号月壤样品颗粒形态特征研究

月壤颗粒形态特征对月面原位挖掘、运输、3D打印等具有重要影响,我国自主获取的嫦娥五号样品可为月球科研站建设等提供月壤关键参数信息。以月面原位资源利用过程关注的月壤颗粒形态特征为目标,利用体视光学显微镜获取了同济大学获批的嫦娥五号月壤颗粒样品图像,构建了一套图像处理和颗粒识别方法,并提出方向差异指数表征颗粒表面粗糙程度,实现了自动提取颗粒边缘并计算其粒度和形态指标。结果表明,所研究嫦娥五号样品颗粒粒径范围为4.36~792.30μm,均值纵横比为0.66,均值圆形度为0.806,均值方向差异指数为0.111。小粒径颗粒占比大,10μm以下颗粒占44.19%。颗粒方向差异指数呈近似正态分布,表明大量颗粒表面粗糙程度近似,并存在少量表面较为光滑和粗糙的颗粒。小粒径颗粒大小与纵横比、圆形度均呈负相关,与表面粗糙程度相关性低,大粒径颗粒大小与形态没有相关性。研究还发现嫦娥五号样品比Apollo 11和Apollo 15样品的颗粒的圆形度更小,形态更不规则。