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As lunar exploration progressed, unmanned lunar rovers encountered harsher and more variable working environments, increasingly complex operating conditions, and greater exploration range requirements. Existing unmanned lunar mesh wheels could not meet the demands of future lunar missions, which required higher traction performance, greater reliability, and lower power consumption. In this study, inspired by the functional characteristics of ostrich toes, we designed a bionic wheel and a comparison wheel. By interchanging the wheel surfaces and lugs (grousers), four types of mesh wheels (Wheels 1–4) were developed and tested. Various loads and slip ratios were applied to investigate how the surface shape of the mesh wheel and the shape of its lugs influenced traction performance and enhanced overall traction. The test results indicated that Wheel 1 outperformed the other wheels in terms of traction performance under the specified conditions and demonstrated greater energy efficiency at lower slip ratios. This led the compacted particles beneath the bionic wheel surface to generate a lateral forward reaction force, thereby propelling the wheel. This caused the compacted particles beneath the bionic wheel surface to generate a lateral forward reaction force, thereby propelling the wheel forward. The bionic lugs operated on a similar principle; however, their contribution to traction was less significant than that of the bionic wheel surface. The innovative design of the wheel surface and lugs effectively addressed the limitations of existing lunar mesh wheel structures. • Combine the sieve wheel design with the concave-convex ostrich sole pattern and the toenail-inspired gripping mechanism. • The designed bionic wheel surface can play a role in fixing simulated lunar soil, thereby improving traction capacity. • Breaking through the limitations of the current lunar exploration sieve wheel structure. [ABSTRACT FROM AUTHOR]

Mitigation of lunar regolith particles is one of the challenges for the success of future lunar exploration, and an electrodynamic dust shield (EDS) presents a promising solution. Although a wide range of investigations have been conducted on the cleaning of lunar regolith and its simulants using EDS, the effects of particle size on cleaning performance have not been experimentally investigated in depth. In this study, we conducted EDS cleaning experiments using simulant particles sorted into different size ranges, with the aid of force balance calculations that vary with particle size. The experimental and calculated results reveal a clear trend: the cleaning performance of simulant particles smaller than 25 μm and larger than 250 μm deteriorated owing to the adhesion force of small particles and the dielectrophoresis and gravitational forces of large particles, respectively. In addition, observations of particle motion using a high-speed camera confirmed the role of dielectrophoresis and Coulomb forces on regolith simulants of various sizes during cleaning. In the effects of the dielectrophoresis force on larger particles, the interactions of polarized particles were clearly visible, resulting in the creation of particle chains and the trapping of particles on the substrate surface of EDS. • The effects of simulant size on cleaning efficiency were experimentally confirmed. • The balance of forces varying with particle size explains the experimental results. • The effects of a dielectrophoresis force on simulant particles were observed. • The interactions of polarized particles created chains. [ABSTRACT FROM AUTHOR]

This study presents piezoelectric actuator placement to induce vibration dust mitigation and offers a solution to mitigate dust accumulation on lunar photovoltaic arrays by bonding a system of piezoelectric actuators to the inactive side of a solar cell. Once deployed, the solar cells and actuators can detect dust accumulation and automatically activate to induce surface vibrations, producing surface acceleration on the solar cell sufficient to overcome contaminant adhesive forces. Three solar cell prototypes were created. All three prototypes were tested for mitigation efficiency when clean, when lightly coated in 1. 30 mg / cm 2 of JSC-1A dust simulant, and after vibration dust mitigation. One prototype was tested at an angle of 10 ° for levels of dust loading from 1. 07 mg / cm 2 to 16. 37 mg / cm 2 and results indicated that the mitigation efficiency decreased from 60. 8 % to 33. 6 % with increasing dust loading. An average of 43 % mitigation efficiency was measured with up to 94 % maximum mitigation efficiency (measured by solar cell I-V curve tests), and a prototype was cryogenically cycled without impedance spectrum degradation. An energy reclamation case study result estimated 278 MJ/kg return on actuator mass cost over one year. [Display omitted] • Advanced vibration dust mitigation technology readiness level from TRL 3 to TRL 4. • Prototype vibration overcame adhesion forces between dust simulant and solar cells. • Prototypes increased power production measured by I-V curve tests after dust removal. • Average mitigation efficiency was 43%, and up to 94%. • Energy study estimated 278 MJ/kg return on actuator mass cost over one year. [ABSTRACT FROM AUTHOR]

Water resources on the Moon are a critical component of international strategies for exploration of the solar system and space-based economic development. Liquid water is essential for human life support and propellant generation. Extreme Lunar conditions of near-vacuum and low temperature preclude the natural presence of liquid water; and they provide the thermodynamic context for water occurrence and its potential extraction. Ice crystals were observed by LCROSS and are inferred to reside in pore spaces of lunar regolith or at the surface in places. Any system proposed for lunar ice mining by induced sublimation needs to address potential vapor loss to the ambient near-vacuum; regolith cohesiveness; low regolith thermal conductivity; negligible sublimation rates below ∼200K; low rates of vapor advection-diffusion through porous regolith; and pressurization due to sublimation that causes redeposition. All of these obstacles have potential solutions with available technologies, but they must be designed within power availability constraints and with the potential to scale up to the resource needs of a growing space economy. • Analysis of the context for lunar ice mining shows key remaining challenges. • Regolith heating, vapor transport and loss, and ice redeposition remain challenges. • Technologies developed for ice mining must explicitly address these challenges. • Mining must also operate within power limits and scale up to a new space economy. [ABSTRACT FROM AUTHOR]

The construction of a lunar base requires a huge amount of material, which cannot be entirely transported from Earth. Therefore, technologies are needed to build with locally available resources, such as the lunar regolith. One approach is to directly melt the lunar regolith on the surface and under the vacuum condition of the Moon, using laser radiation. In this article, a lunar regolith simulant is laser beam melted to two-dimensional single-layer-structures using different ambient pressures from 0.05 mbar to 2000 mbar, laser process parameters from 60 W to 100 W laser power, and 1 mm s−1 to 3 mm s−1 feed rates. Additionally, the influence of the ambient gas was investigated using argon as an air alternative. The results show that the ambient pressure on the Moon is not negligible when studying the melting processes of lunar regolith on Earth. With decreasing ambient pressure, the appearance of the melted regolith simulant varies from a shiny to a matt surface. At the highest laser energy density, the thickness of a single-layer increases from 2.6 ± 0.4 mm to 5.3 ± 0.3 mm and the porosity of the melted regolith increases from 17.2 % to 52.2 % with decreasing ambient pressure. Additionally, mechanical properties are determined using 3-point bending tests. The maximum bending strength decreases by 60 % with the increased ambient pressure from 10 mbar to 2000 mbar. Consequently, the development of in-situ resource utilization technologies, which process the lunar regolith directly on the lunar surface, must consider the ambient pressure on the Moon. Otherwise, the processes will not work as expected from the experiments in Earth-based laboratories. • Porosity of melted simulant increases by 67 % when reducing pressure. • The thickness of a melted regolith layer increases by 51 % when reducing pressure. • Maximum bending force of the sample is 75 % higher at low-pressure conditions. • The maximum bending stress increases by 60 % at high-pressure conditions. • Argon leads to higher porosity in the sample than air at high-pressure conditions. [ABSTRACT FROM AUTHOR]

The feasible construction of lunar habitats will be strongly dependent upon the effective utilisation of resources locally available on the Moon. The Moon's surface material, otherwise known as regolith, is an obvious resource. There will, however, be the need to transport materials from Earth to be added to the regolith in order to make viable construction materials. It is noted that material transported from Earth must be kept to a minimum. This paper reports the development of a potential lunar construction material that utilises regolith simulant in combination with epoxy resin (henceforth resin). The material is referred to as regolith-resin-composite (RRC), and the results of an experimental investigation are reported herein. Specific variables of the study include (i) minimum amount of resin required to achieve sufficient mixing and binding with the regolith and (ii) mechanical and analytical properties of a range of resin to regolith mix combinations. Mechanical tests' consist of compressive, flexural, and tensile strength, while analytical tests comprise morphology, microstructure, and thermogravimetric analysis. It is shown that 15% by mass of resin produces a minimum viable material (based on the mix combinations considered in the study), while 20% resin content by mass produces the greatest mechanical strengths, such as 98 MPa compressive strength. The results presented in this study demonstrate that RRC has the potential to become a viable lunar construction material. • Development of lunar regolith-resin-composite (RRC). • Analytical and mechanical properties of RRC. • RRC exhibited high thermal degradation resistance. • RRC has promising mechanical properties. • RRC is advantageous for lunar settlements. [ABSTRACT FROM AUTHOR]

Background: Due to cosmic radiation bombardment and over 4 billion meteorite and micrometeoroid impacts on the airless Moon, the lunar surface is covered by a layer of fine, reactive dust. Very little is known regarding the toxicity of lunar dust on human physiology. This study assessed airborne lunar dust exposure in rats on localized pulmonary and systemic immune parameters. Methods: Rats were exposed to 0 (air only), 20.8 (low), and 60.6 (high) mg/m3 of respirable-size lunar dust for 4 weeks (6 h/day, 5 days/week). Rats were then euthanized either 1 day, 7 days, 4 weeks, or 13 weeks after the last exposure. Peripheral blood and lung lavage fluid samples were collected for analysis. Assays included leukocyte distribution by multicolor flow cytometry and electron/fluorescent microscopy to visualize cell–particulate interactions and lavage/plasma cytokine concentration. Mitogen-stimulated cytokine production profiles, as a measure of cellular function, were performed on whole blood samples only. Results: Untreated lavage fluid was comprised primarily of pulmonary macrophages. High-dose lunar dust inhalation (60.6 mg/m3) resulted in an influx of both neutrophils and lymphocytes. Although the percentage of lymphocytes increased, the T-cell CD4:CD8 ratio was unchanged. Cytokine analysis of the lavage fluid showed increased levels of IL-1β and TNFα. These alterations generally persisted through the 13-week sampling. Blood analysis showed few systemic immune alterations from the lunar dust inhalation. By week 4, the peripheral granulocyte percentage was elevated in the treated rats. Plasma cytokine levels were unchanged in all treated rats compared to controls; however, altered mitogen-stimulated cytokine production profiles were observed consisting of increased IL-1β and IL-6 and decreased IL-2. There were minimal adverse immune effects, in both lung or peripheral blood, following low-dose exposure to 20.8 mg/m3 lunar dust. Conclusion: Exposures to high concentrations of lunar dust resulted in persistent lung inflammation and some systemic immune dysregulation that did not subside even 13 weeks after the dust exposure. This information is beneficial in deriving an exposure limit to airborne lunar dust and for spacecraft engineers considering dust mitigation systems in lunar landers or habitats. [ABSTRACT FROM AUTHOR]

The SurfCam is being developed to understand the microscopic lunar surface structures known as the fairy castle structure, composed of grains with an average size of a few tens of microns. It is designed as a microscopic light-field camera (LFC) and is one of the camera instrument packages in GrainCams, a candidate payload for NASA's Commercial Lunar Payload Services (NASA/CLPS). The light-field camera system allows for obtaining depth maps and 3D images of lunar surface structures on a scale of tens of microns by capturing a 4D light field. This camera system can be achieved by adding a microlens array (MLA) between the main optics and the sensor in a typical camera system. The Cycles render engine, a physically-based path-tracing (one of the ray-tracing types) renderer of Blender 3D software, helps to simulate realistic light-field images. We performed path-tracing simulations by configuring SurfCam's optics and creating test objects to confirm depth estimation results in Blender 3D. In this study, we present the results of simulated images and analyze them based on the current design of the SurfCam. [ABSTRACT FROM AUTHOR]

This paper presents the concept of a radiofrequency (RF) sensor designed to estimate the mass of the regolith acquired by a sampling device or excavator in planetary environments. The sensor utilizes a microstrip line with an open end as the sensing element, with the mass estimation based on measurements of the phase of the reflection coefficient (S11 of the scattering matrix) for the line immersed in the regolith. The Rotary Clamshell Excavator (RCE) was employed for the experimental evaluation of the sensor's performance. The RCE successfully passed an environmental test campaign, demonstrating its suitability for future lunar missions. The test results indicate that the RF sensor can estimate the mass of the acquired regolith with reasonable accuracy, approximately 15%, making it a viable solution for rough mass estimation in sampling devices and excavators. [ABSTRACT FROM AUTHOR]

In recent years, prominent spacefaring nations have redirected their attention towards the Moon as a potential avenue for economic prospects and as a pivotal waypoint for extended space exploration endeavors. Nonetheless, a notable concern has emerged regarding the dispersion of lunar dust during lunar landings, a phenomenon that has been associated with documented instances of equipment damage during prior missions. To mitigate these challenges, leading research institutions are actively engaged in endeavors aimed at minimizing the adverse effects of dust dispersal during lunar and extraterrestrial landings. This review paper provides a comprehensive overview of ongoing research and development endeavors focusing on the interaction dynamics between rocket plumes and lunar surfaces, along with the resultant dispersion of lunar dust triggered by rocket plume impingement. Additionally, it presents research efforts aimed at developing lunar dust mitigation technologies. • This paper conducts a survey of research on rocket plumes and lunar dust dispersal. • The challenges posed by lunar dust during past lunar landings are explored. • The effects of lunar dust dispersal through in-situ experiments are investigated. • Previous and ongoing experiments and numerical methods are examined. • Continued research in plume-surface interactions to mitigate hazards is crucial. [ABSTRACT FROM AUTHOR]

With the development of space technology, in situ resource utilization (ISRU) of lunar resources holds great potential for constructing lunar bases. This study, for the first time, proposes the in situ construction of lunar soil simulants-based battery systems. When novel ilmenite cathode materials are applied in aqueous aluminum-ion batteries (AAIBs), a facile ball milling treatment is used to simulate the natural characteristics of lunar-based ilmenite with proper electrochemical performance. The in situ constructed lunar soil-based batteries demonstrated a practical capacity of 68.1 mAh g−1 at 1.0 A g−1 with a capacity retention rate of 89.6% after 100 cycles. Even at a high current density of 5.0 A g−1, the as-prepared batteries still maintained a capacity of 41.7 mAh g−1. This study provides a promising energy storage solution for lunar bases and promotes sustainable energy technologies through in situ utilization of lunar resources. [ABSTRACT FROM AUTHOR]

In the areas of aerospace and military industry, wheeled vehicles are expected to have the ability of passing various ground surfaces, including lunar soil, sand, marsh, mud flat, etc. This makes vehicle trafficability on soft ground become a very hot research topic. There are very a few difficulties in the present research of vehicle trafficability on soft ground, such as obtaining wheel-ground interaction information, inaccurate identification of soil mechanical characteristics parameters, and single evaluation index. In this paper, a novel approach of evaluating the vehicle trafficability on soft ground using wheel force information is proposed. As parts of the proposed approach, the methods of obtaining wheel force information, identification of soil mechanical characteristics parameters and integated method of trafficability evaluation, are discussed in detail. The proposed approach was validated through a practical test. [ABSTRACT FROM AUTHOR]

Adequate water supplies are crucial for missions to the Moon, since water is essential for astronauts' health. Ionic liquids (ILs) have been investigated for processing metal oxides, the main components of lunar regolith, to separate oxygen and metals. The IL must be diluted in the process. Recycling this diluted IL post-processing is important to reduce the materials required in resupply missions. In addition, water will be needed in lunar greenhouses for growing food and aiding in sustaining a habitable environment. Direct contact membrane distillation (DCMD) is a new technology for water purification that was examined in this study for its feasibility to concentrate IL. Hydrophobic membranes composed of polytetrafluoroethylene (PTFE) and polyvinylidene (PVDF) were found to hold promise in separating solutes from water to concentrate a diluted IL solution and to recover water. A bench-scale DCMD system was employed to test this method at temperatures of 50 °C, 65 °C, and 80 °C. Hence, the benefits and limitations of DCMD with PTFE and PVDF membranes were explored for the aqueous IL 1-ethyl-3 methylimidazolium hydrogen sulfate for DCMD performed at different temperatures. [ABSTRACT FROM AUTHOR]

One of the most surprising and important findings of the first human landings on the Moon was the discovery of a very fine layer of lunar dust covering the entire surface of Moon along with the negative impacts of this dust on the well-being and operational effectiveness of the astronauts, their equipment, and instrumentation. The United States is now planning for human missions to Mars, a planet where dust can also be expected to be ubiquitous for many or most landing sites. For these missions, the design and operations of key hardware systems must take this dust into account, especially when related to crew health and safety. Improved understanding of Martian dust characteristics can inform its potential to also perform transport of microorganisms, both those inadvertently brought to Mars by the astronauts, or, if Martian microorganisms exist, the potential for their inadvertent return to Earth with the astronauts. Careful planning and design are needed to assure that future missions do not violate the United Nations Outer Space Treaty (1967) signed by all spacefaring nations. In this paper, we review the impact of lunar dust on the Apollo missions and identify several questions about dust in the atmosphere of Mars that may be answered by the curated samples that would be returned by the planned Mars Sample Return (MSR) Campaign. These answers would not only provide an opportunity to better understand the history of Mars but could also reduce uncertainty in charting the future of humanity's exploration of the planet. [ABSTRACT FROM AUTHOR]

In-space biomanufacturing provides a sustainable solution to facilitate long-term, self-sufficient human habitation in extraterrestrial environments. However, its dependence on Earth-supplied feedstocks renders in-space biomanufacturing economically nonviable. Here, we develop a process termed alternative feedstock-driven in-situ biomanufacturing (AF-ISM) to alleviate dependence on Earth-based resupply of feedstocks. Specifically, we investigate three alternative feedstocks (AF)—Martian and Lunar regolith, post-consumer polyethylene terephthalate, and fecal waste—to develop an alternative medium for lycopene production using Rhodococcus jostii PET strain S6 (RPET S6). Our results show that RPET S6 could directly utilize regolith simulant particles as mineral replacements, while the addition of anaerobically pretreated fecal waste synergistically supported its cell growth. Additionally, lycopene production using AF under microgravity conditions achieved levels comparable to those on Earth. Furthermore, an economic analysis shows significant lycopene production cost reductions using AF-ISM versus conventional methods. Overall, this work highlights the viability of AF-ISM for in-space biomanufacturing. Reducing reliance on Earth-supplied feedstocks is crucial for advancing in-space biomanufacturing. Here, the authors explored three alternative feedstocks – Martian and Lunar regolith, post-consumer polyethylene terephthalate, and fecal waste – to develop an alternative medium for cost-effective in-space lycopene biomanufacturing. [ABSTRACT FROM AUTHOR]

This study introduces a novel composite construction material composed of lunar regolith combined with PEEK in dry powder form. The work demonstrates significant advantages over alternative methods, primarily by reducing production power consumption and simplifying the manufacturing process. Building on previous research that explored binder optimization through process simplification and targeting predefined shapes, this work delves deeper into a comparative analysis of high-performance thermoplastics. Among the various options, PEEK demonstrates the most favorable properties. The study investigates key processing parameters and evaluates the effects of vacuum processing and temperature testing on mechanical properties. The research also evaluates the effects of vacuum processing and temperature testing to assess the material's performance under lunar conditions. Comparative analysis is performed with standard performance of various reinforced and unreinforced concretes and with standard requirements for construction bricks as per ASTM standards. This shows that the composite, with an organic binder content as low as 5 wt%, has great potential. Notably, the improvements achieved through vacuum curing ensure compliance with lunar environmental conditions and alignment with most Earth-based engineering standards. Samples compacted at 7.50 MPa with 10 wt% binder, and tested at room temperature, achieve a compression strength of 16.3 MPa, exceeding that of industrial floor bricks and matching that of building bricks used on Earth. Bending strength (7.4 MPa) aligns with steel fiber-reinforced and high-strength concretes. Vacuum curing further enhances these properties, with an observed increase of +66% in bending strength and +33% in compression strength. [ABSTRACT FROM AUTHOR]

A magnetic cleaning system comprising a permanent magnetic roll with a non-magnetic sleeve and a particle collection component is a unique dust mitigation technology in lunar explorations. Enhanced cleaning performance can be achieved by optimal balancing of the forces applied to the particles. The effects of particle size on the capture and release performances were investigated through experiments using size-sorted particles of a lunar regolith simulant and a simple analysis of the force balance varying with the particle size. Experimental and calculated results clarified that the capture of the particles was predominantly facilitated by the magnetic force, while their release was primarily due to the centrifugal force. Although the release of captured particles smaller than 25 μm is one of the challenges in this system due to the adhesion force, this force also contributed to the capture of the small particles with lower magnetic permeability. This magnetic cleaning system, demonstrating its utility in removing particles not only from spacesuits but also from other equipment, achieved the capture and release rates exceeding 70 % and 90 %, respectively, when the simulant particles were dispersed on a flat surface. Moreover, the capture rate of simulant particles with higher magnetic permeability improved, reaching approximately 85 %. • The size of regolith particles affects the performance of the magnetic cleaning system. • An adhesion force prevents the release of smaller particles. • The adhesion force also aids in capturing particles with less magnetic permeability. • The captured particles were mainly released by a centrifugal force. [ABSTRACT FROM AUTHOR]

A description is given of simulation experiments of the interaction of lunar dust with the surface of solar panels. The experiments are based on the creation of a dust plasma cloud by exposure of a substance simulating lunar dust to the radiation from a powerful pulse gyrotron. This approach has been tested using a lunar regolith simulant. An analysis is presented of the results of precipitation of charged regolith particles on solar panels of various types and variation in their efficiency. [ABSTRACT FROM AUTHOR]

Due to the Askaryan effect, radio emissions will be produced when ultra-high-energy (UHE) cosmic rays and neutrinos impact the lunar regolith. Many experiments have been proposed and performed to detect such radio emissions from the lunar regolith. However, none of the Cherenkov radio signals has been detected in these experiments up to now. In order to improve the detectability of the UHE particles, we proposed an experiment to carry out the radio observations of the UHE cosmic rays and neutrinos with two 30 m telescopes for a far longer time than the present experiments. The expected sensitivity for the detection of such UHE particles has been calculated, both for cosmic rays and neutrinos. The results show that a few UHE particle events above 1020 eV could be detected with the expected observation time of several thousand hours. [ABSTRACT FROM AUTHOR]

Nanoscale Fourier transform infrared (Nano-FTIR) imaging and spectroscopy correlated with photoluminescence measurements of lunar Apollo samples with different surface radiation exposure histories reveal distinct physical and chemical differences associated with space weathering effects. Analysis of two sample fragments: an ilmenite basalt (12016) and an impact melt breccia (15445) show evidence of intrinsic or delivered Nd3+ and an amorphous silica glass component on exterior surfaces, whereas intrinsic Cr3+ and/or trapped electron states are limited to interior surfaces. Spatially localized 1050 cm−1/935 cm−1 band ratios in Nano-FTIR hyperspectral maps may further reflect impact-induced shock nanostructures, while shifts in silicate band positions indicate accumulated radiation damage at the nanoscale from prolonged space weathering due to micrometeorites, solar wind, energetic x-rays and cosmic ray bombardment. Our observations demonstrate that space weathering alterations of the surface of lunar samples at the nanoscale may provide a mechanism to distinguish lunar samples of variable surface exposure age. [ABSTRACT FROM AUTHOR]

The sharp morphological features of lunar dust particles generate significant elastic–plastic contact forces and deformations upon contact with material surfaces, which considerably affect the mechanical properties of lunar dust particles, including their contact, collision, adhesion, transport, and wear characteristics. Despite these severe effects, valid models considering the contact characteristics of typical sharp-featured lunar dust particles are currently lacking. This study proposes an elastic–plastic contact model for nonrotationally symmetric lunar dust particles showing typical sharp features. Detailed derivations of the expressions for various physical responses observed when lunar dust particles establish normal contacts with elastic and elastic–plastic half-spaces under adhesive conditions are also provided. These include derivations for elastic forces, elastic–plastic forces, contact areas, pull-off forces, residual displacements, and plastic deformation areas. Furthermore, the tangential pull-off force during the tangential loading of lunar dust particles is derived, and the tangential contact characteristics are explored. Comparisons of the results of the proposed model with those of previous experiments reveal that the proposed model shows errors of only 6.06 % and 1.03 % in the maximum indentation depth and residual displacement, respectively. These errors are substantially lower than those of conventional spherical models (60.30 % and 60.13 %, respectively), confirming the superior accuracy of the proposed model. Furthermore, the discrete element method is employed to analyze the effects of normal and tangential contacts, dynamic characteristics, and plastic deformations on the considered lunar dust particles. The results are then compared with those of existing contact models. They reveal that maximum elastic–plastic forces under normal contact conditions are positively correlated with the initial velocity but negatively correlated with the lateral angle. Furthermore, the tangential pull-off force is positively correlated with the normal force and surface energy. In addition, the contact duration of lunar dust particles is positively correlated with their initial velocities, while the residual displacement is negatively correlation. For instance, as the initial velocity increases from 10 to 50 m/s, the maximum elastic–plastic force increases from 37.64 to 321.72 mN. Comparisons of the proposed model with other contact models reveal that the maximum elastic–plastic force of the elastic–plastic triangular pyramid model is only 14.93 % that of the cylindrical model, 34.23 % that of the spherical model, and 76.27 % that of the conical model, indicating significant reductions in the maximum elastic–plastic force owing to the plastic deformations of particles with typical sharp features. Overall, the results of this study offer crucial insights into the mechanical characteristics of nonspherical lunar dust particles under various contact conditions, such as elastic–plastic and adhesive contacts, and can guide in situ resource utilization on the lunar surface and for craft landings. • Elastic–plastic contact forces and deformations of nonrotationally symmetric lunar dust particles. • Normal and tangential contacts, dynamic contact characteristics, and plastic deformations of particles. • Maximum elastic–plastic forces increase with initial velocities and decrease with lateral angles. • Increasing initial velocities increase contact durations and decrease residual displacements. [ABSTRACT FROM AUTHOR]

Based on the temperature change data of the penetrator, to achieve in-situ detection of the thermal conductivity of the lunar regolith profile, it is necessary to establish a heat conduction model between the penetrator and the lunar regolith. This study simplifies the heat conduction model of the complex shaped penetrator through simulation analysis results. Then, we proposed a thermal conductivity inversion method based on the transient thermal cylinder source model. The thermal diffusion test was carried out under normal temperature and pressure on a standard reference object with known thermal conductivity and the thermal conductivity inversion work was completed, which verified the feasibility of the inversion method. Then, we completed the thermal diffusion test of the penetrator and the lunar regolith simulant under the simulated low-temperature vacuum environment of the lunar surface, and carried out the thermal conductivity inversion of the lunar regolith simulant based on the thermal diffusion test data, which proved that the proposed thermal inversion method is applicable for the lunar regolith under the low-temperature vacuum. Finally, the thermal conductivity test was conducted on icy lunar regolith simulant with different water contents and a thermal diffusion test in a vacuum low-temperature environment was carried out. The thermal conductivity inversion was completed using the same method, which proved that the inversion method is suitable for icy lunar regolith simulant. • Simplified heat conduction model of penetrator and lunar regolith. • Heat inversion method of penetrator and lunar regolith. • Verification of penetrator based thermal conductivity inversion method. • Applicability test of inversion method for lunar regolith and icy lunar regolith simulant. [ABSTRACT FROM AUTHOR]

As the idea of crewed outposts on the Moon gains momentum, In-Situ Resource Utilization (ISRU) technologies tend to become imperative to fulfill astronauts' needs. This article explores a way to use the lunar regolith as a source material for the additive manufacturing of complex objects, based on the selective laser melting (SLM) technique. A lunar regolith analog, Basalt of Pic d'Ysson (BPY), is used as a starting point for this study, to investigate the now demonstrated impact of amorphous analog content in the powder bed, substrate type, and post-SLM annealing treatments on the mechanical properties of 3D-printed objects. Improvements to the manufacturing and sample extraction stages are proposed to systematically reproduce the high compressive strength values obtained, thus contributing to the robustness and reliability of the process. • A new basaltic mare analog called BPY is presented and characterized. • Samples are made from this analog with SLM technology. • Objects printed with amorphous analog showed high compressive strength. • The nature of the substrate also plays a role in the final mechanical properties. • Annealed objects have reached maximal compressive stress of up to 132 MPa. [ABSTRACT FROM AUTHOR]

During the final metres of the powered descent of Apollo 11, astronauts Neil Armstrong and Buzz Aldrin lost sight of the lunar surface. As the retro-rockets fired towards the lunar dust – or regolith – to decelerate the spacecraft, soil erosion occurred and the blowing dust led to severe visual obstruction. After a successful landing, the presence of dust continued to impact the mission with adverse effects including respiratory problems and difficulty in performing tasks due to clogging of mechanisms, amongst others. As these effects were observed in subsequent missions, the "dust problem" was identified as one of the main challenges of extra-terrestrial surface exploration. In this work, the focus is placed on dust dispersal, which arises from the interaction between a rocket exhaust flow – or plume – and the planetary surface. Termed plume-surface interactions (PSI), this field of study encompasses the complex phenomena caused by the erosion and lofting of regolith particles. These particles, which are ejected at high-speeds, can lead to damage to the spacecraft hardware or a reduction in functionality. Moreover, plumes redirected back towards the landers can induce destabilising loads prior to touch-down, risking the safety of the landing. To achieve a sustained presence on the Moon, as planned by NASA's Artemis programme, it is essential that PSI are well understood and mitigating measures are put in place, particularly if spacecraft are to land in the vicinity of lunar habitats. Although experimental work began in the 1960s and mission PSI were first recorded in 1969, a fundamental understanding of this phenomena has not yet been achieved. In this paper, a compendium of experimental PSI is presented, identifying the main challenges associated with the design of tests, stating important lessons learnt and the shortcomings of available experimental data and findings. Lastly, recommendations for future experimental work are presented. [Display omitted] • Critical review of plume-surface interactions experimental work. • Retro-propulsive rocket plumes erosion on Lunar and Martian surfaces. • Erosion mechanisms on planetary surfaces. • The challenges and risks of plume-surface interactions. • Evaluation of diagnostic techniques for PSI. [ABSTRACT FROM AUTHOR]

The axis inclination of a slender spiral drill tool is inevitable while drilling and sampling lunar soil; this alters the stress situation of the drill tool. In this paper, the interaction process between the drill tool and lunar soil is simplified and equated to the process of cylindrical cavity expansion caused by bit penetration and the process of soil agitation caused by the inclined auger, and the predictive model of drilling resistance is constructed. The sensitivities of the main soil mechanical parameters are analyzed, and it indicates that cohesion, soil pressure coefficient, and gravitational acceleration have an obvious positive effect on drilling resistance. A simulated lunar soil drilling test is conducted, and the effectiveness of the drilling resistance predictive model are verified by comparing the test and simulation results, providing theoretical support for technological breakthroughs in other extraterrestrial drilling and sampling missions. [ABSTRACT FROM AUTHOR]

Additive manufacturing using lunar regolith can significantly reduce reliance on Earth's resources for future lunar surface construction. To enhance the quality of parts formed through additive manufacturing, a comprehensive understanding of the melting characteristics of lunar regolith is crucial. In this study, the melting temperature range, melt viscosity, workability range, and contact angels between melt and substrates of the CUG-1A lunar regolith simulant were determined. The complete melting temperature of CUG-1A is about 1320 °C, and the corresponding melt viscosity is 8.39 Pa⋅s. The five characteristic temperatures of CUG-1A under argon flow, including sintering point, softening point, half-sphere point, floating point, and fluid point, are 1081 °C, 1115 °C, 1149 °C, 1158 °C, and 1311 °C, respectively. These characteristic temperatures are about 35 °C–50 °C higher in vacuum. The melt demonstrates good wetting ability at the flow point temperature with contact angels of 29° and 21° on corundum and platinum. The bubble generation, growth and release processes were observed for the melts under vacuum conditions. These results would provide essential data for the development of in-situ construction technologies, such as energy beam focused melting lunar regolith. [ABSTRACT FROM AUTHOR]

In order to accurately model the machine-lunar soil simulant interaction, this study combined physical and simulation experiments to calibrate the discrete element simulation parameters of the JLU-H lunar highland simulant. First, the intrinsic parameters and the true angle of repose of the JLU-H were determined through physical tests to provide data for subsequent simulation tests. A Plackett-Burman test was designed to identify and select the parameters that have a significant effect on the angle of repose. The range of values of the significant parameters was then optimized using the steepest climb test. The Box-Behnken test was then utilized to calibrate and obtain the optimal parameter combinations. Finally, a validation test of the angle of repose was conducted using the calibrated DEM parameters. The relative error between the simulation results and the test results was 1.54 %. Then further straight shear tests were conducted to verify the accuracy and validity of the DEM parameters. The results show that the calibrated parameters can provide a reference for the selection of discrete element simulation parameters for lunar soil simulant and the design and optimization of drilling and excavation machinery for lunar exploration. [ABSTRACT FROM AUTHOR]

In-situ construction method is expected to be considered for lunar base construction because of its reducing transportation cost. Among the many in-situ construction processes, the flash sintering process can significantly reduce the processing time and become a potentially effective in-situ resource utilization (ISRU) technology. In this study, the flash sintering process was investigated for the first time to realize the sample forming of HUST-1 lunar regolith simulant (LRS). The effects of sintering temperature on the micro- and macrostructural characteristics and mechanical properties of the samples were systematically studied. The results showed that the densities and mechanical properties of the sintered samples were improved with the increase of the sintering temperature (from 1050 °C to 1290 °C) in a low vacuum environment for 4 min. Joule heating effect was investigated to cause rapid high-temperature solid-phase reactions between the LRS particles. At 1290 °C, the compressive strength of the sintered sample reached maximum 59.47 MPa. This study provides an efficient forming method for lunar construction in the future. [ABSTRACT FROM AUTHOR]

Over the past three decades, advances in crystal nucleation and growth have led to the understanding that crystallization proceeds through various pathways, ranging from the conventional atom-by-atom model to the particle aggregation- or amorphous transformation-based non-classical modes. Here, we present a novel mineralization mechanism exemplified by a lunar chromite formed via solid-liquid interface reactions through investigations of a lunar breccia returned by the Chang'e 5 mission. The chromite occurs in the middle of a whisker-shaped intergrowth structure made by olivine at the bottom and nanospheres of troilite and metallic iron at the top. Morphological observation and size statistics of the nanospheres, including those within the whisker structure and the others dispersed in glass, suggest the nanophases attached to olivine with coherent crystallographic orientations, possibly through an oriented aggregation process. The chromium deficiency in the olivine near the interface between olivine and chromite suggests that Cr in chromite originated from olivine, but the significantly reduced ferrous concentration in the glass surrounding chromite indicates the iron was derived from surrounding impact-induced glass. Based on laboratory observations and simulated calculations of energy and lattice mismatch, we propose that chromite crystallized at the interface between troilite and olivine in the impact melts, during which the nanospheres were lifted and transported away from olivine surface and formed a mushroom-shaped structure. This finding suggests that oriented attachment growth, chiefly confined to homogeneous systems thus far, can also occur in heterogeneous systems far from equilibrium, such as that produced by the impacts. It is conceivable that the studied crystallization pathway occurring on the heterogeneous interfaces may have been a common mineralization mode at highly nonequilibrium conditions. [ABSTRACT FROM AUTHOR]

The Luna Analog Facility, a joint ESA-DLR endeavour, consists of three components and spans an area of 1,000 m2, providing testbeds of simulated lunar environments. The main sections within the facility are a large area filled with lunar mare regolith simulant resembling mare regions and a smaller, individual "Dust Chamber". The latter replicates highland conditions and contains approximately 20 tons of material, specifically simulating the fine-particle lunar regolith portion up to 250 µm. The Dust Chamber serves as a platform for testing various technologies, such as mechanical tools, robotic operations, in-situ resource utilization activities, and astronaut attire, as well as different procedures including rover and astronaut tasks. This work represents the geotechnical, geochemical and mineralogical characterization of the Lumina Sustainable Materials Ltd. 2023 batch highland simulants, from which Lunar250 is intended for use in the Luna Dust Chamber. Additionally, this work provides new results for ESA's mare simulant, EAC-1. We provide data on particle size distribution, particle shape, abrasivity, density, water content, major and trace element geochemistry and modal mineralogy. As the simulants in the Luna Facility will be constantly overseen, this work organized by the Vulcan Facility (ESA) intends to support the monitoring of the geotechnical property variations of the simulants over time. Ultimately, we analysed several properties with different tools to emphasize how different methods and instruments affect the variability and reliability of the results. [ABSTRACT FROM AUTHOR]

This paper presents datasets and analyses of 3D LiDAR scans capturing the rutting behavior of a rover wheel in a single-wheel terramechanics testbed. The data were acquired using a LiDAR sensor to record the terrain deformation caused by the wheel's passage through a Toyoura sandbed, which mimics lunar regolith. Vertical loads of 25 N, 40 N, and 65 N were applied to study how rutting patterns change, focusing on rut amplitude, height, and inclination. This study emphasizes the extraction and processing of terrain profiles from noisy point cloud data, using methods like curve fitting and moving averages to capture the ruts' geometric characteristics. A sine wave model, adjusted for translation, scaling, and inclination, was fitted to describe the wheel-induced wave-like patterns. It was found that the mean height of the terrain increases after the grouser wheel passes over it, forming ruts that slope downward, likely due to the transition from static to dynamic sinkage. Both the rut depth at the end of the wheel's path and the incline increased with larger loads. These findings contribute to understanding wheel–terrain interactions and provide a reference for validating and calibrating models and simulations. The dataset from this study is made available to the scientific community. [ABSTRACT FROM AUTHOR]

This paper presents a systematic analysis of power generation technologies for a lunar outpost supporting six astronauts. Based on a detailed power budget analysis requiring 65 kWe for life support, scientific equipment, and in situ resource utilization (ISRU), a comparative analysis of solar and nuclear power solutions is conducted. Nuclear fission is identified as the most promising technology based on key criteria, including mass efficiency, reliability, and power density. A parametric study is then conducted to optimize the nuclear reactor design, with particular focus on radiation shielding using lunar regolith and its impact on safety distances. The analysis demonstrates that proper shielding can reduce the required safety distance from over 2.5 km to approximately 90 m while maintaining radiation exposure within acceptable limits. Finally, leveraging insights from existing reactor designs, an optimized configuration is proposed that combines multiple small reactors to meet the unique challenges of lunar power generation while ensuring crew safety and operational redundancy. [ABSTRACT FROM AUTHOR]

It is very easy for a small lunar rover to slip on the regolith of the lunar surface and become stuck. Previous studies have quantitatively evaluated the effects of wheel geometry, such as elliptical or eccentric wheels, on the performance of a rover when climbing up slopes. These studies reported that the rovers were able to run on a 30-degree slope made of silica sand. In this study, a small rover was designed and created, and running tests were conducted using lunar soil simulant and silica sand to predict its performance on the lunar surface. The effects of soil differences on the performance of the rover were clarified through the running tests and the measurement of reaction force on the lug. Although the rover exhibited a greater slip ratio on the lunar soil simulant than on the silica sand, the rover with eccentric wheels was able to climb up to a 30-degree angle on the lunar soil simulant. The results for the sinkage measurement of the rover showed that the eccentric wheels prevented sinkage with their up-and-down motion, enabling the rover to climb steep slopes. Furthermore, the tests for measuring the reaction force on the lug indicated that the density change in the lunar soil simulant did not provide sufficient reaction force, and that the running performance on the lunar soil simulant was lower than that on the silica sand. [ABSTRACT FROM AUTHOR]

The Chang'e-6 mission achieved the first successful sample collection and return from the Moon's far side. Accurate alignment detection of the primary packaging container is critical for the success of this mission, as it ensures proper retrieval of lunar soil. To address challenges such as complex backgrounds, uneven lighting, and reflective surfaces, this paper introduces an alignment detection method that integrates YOLO object recognition, Devernay subpixel edge detection, and the RANSAC fitting algorithm. By employing both linear and elliptical fitting techniques, the method accurately determines the median line of the primary packaging container, ensuring precise alignment detection. The effectiveness of this approach is demonstrated by an average alignment distance of 0.28 mm with a standard deviation of 0.03 mm in lunar surface images, underscoring its accuracy and reliability. [ABSTRACT FROM AUTHOR]

The lunar environment is known to be characterized by complex interactions between plasma, the exosphere, dust, and the surface. However, our understanding of the environment is limited due to the lack of experimental evidence. Here, we propose a small, low-cost mission to characterize the dust and exosphere environment of the Moon. Named the Limb Pathfinder (LimPa), this is a proof-of-concept mission aimed toward understanding the coupling between plasma, dust, and tenuous neutral atmosphere. The LimPa mission was proposed to a call for the Small Mission to the Moon issued by European Space Agency in 2023. LimPa is designed to examine the dust exosphere above the lunar polar regions by using an utterly novel remote-sensing technique to measure the solar wind hydrogen atoms—the solar wind protons that are neutralized to hydrogen atoms. Its goals are (1) to detect for the first time the neutralized solar wind hydrogen produced by exospheric gas and levitated dust; (2) to measure the height profiles of the levitated dust and exospheric gas densities; and (3) to determine the emission mechanism of the horizon glow. Our baseline design of the LimPa mission is a 12U CubeSat. Three highly matured instruments are used: an energetic neutral atom camera, a proton sensor, and a camera system. The LimPa CubeSat is proposed to be inserted into a circular lunar polar orbit, with an altitude of 100 km as a baseline. The Sun-pointing attitude will allow measurements of neutralized solar wind that are produced by the exosphere and dust grains above the polar regions. The nominal lifetime is for 3 months as a pathfinder mission. The LimPa mission will open a new window to remote characterization of the lunar dust exosphere environment above the poles, and will demonstrate that this monitoring can be achieved with a simple and low-cost instrument system and spacecraft operation. The concept to be proven by the LimPa mission will enable long-term monitoring of the fragile dust exosphere environment, which substantially impacts on lunar exploration and will be significantly altered by human activities. [ABSTRACT FROM AUTHOR]

The article discusses the discovery of natural few-layer graphene on the Moon, challenging the prevailing theory of a carbon-depleted Moon. The study utilized Chang'e-5 lunar soil samples to visualize the graphene structures and proposed a formation mechanism involving volcanic eruptions and mineral catalysis. The findings provide new insights into the Moon's origin and may lead to breakthroughs in graphene synthesis techniques. The research was supported by the China National Space Administration and the National Natural Science Foundation of China. [Extracted from the article]

Lunar regolith simulants from the NU-LHT series were characterized using different configurations for performing Raman spectroscopy measurements, including with different excitation wavelengths and spot sizes. This testing was performed to explore various Raman measurement configurations for analyzing lunar regolith, especially in terms of capturing distinctive fluorescence features that can provide more information about the composition of the regolith. Results obtained utilizing configurations having a 785 nm laser for excitation showed relatively narrow, intense fluorescence signals between 870 and 890 nm, which, to the best of our knowledge, has not been observed before in lunar regolith or lunar simulant samples. These distinctive fluorescence features, attributed to a specific rare earth element (REE) impurity, adds further support that these types of features can be utilized for identification and potentially quantification of the amount of REE or transition metal impurities in lunar regolith. Further, other aspects of these Raman instrument configurations and their advantages were explored, especially those applicable for use in a lunar environment in support of in-situ resource utilization (ISRU). • Investigated series of lunar simulants with different Raman configurations. • Previously unreported, distinctive fluorescence feature from lunar simulant reported. • Fluorescence feature reported was attributed to a rare earth element, Neodymium. • Further support of applicability of Raman spectroscopy for rare-earth elements. [ABSTRACT FROM AUTHOR]

During penetration, a large quantity of friction-induced heat is generated, significantly increasing the projectile surface temperature. Considering that the temperature variation depends on the physical properties of the target being penetrated, understanding this relationship can aid in extraterrestrial material behavior for detection and analysis efforts. The study investigated the patterns of heat generation and the distribution of temperature on the surface of a projectile as it penetrates lunar regolith. For discrete medium penetration, large deviations appear in temperature prediction due to particle extrusion flow. Thus, a heat flux density model on the projectile surface by introducing a relative velocity factor (RVF) for correction was established. The particle flow characteristics simulation and fitting model of the introduced factor were also obtained. We constructed a theoretical relationship between the resistance and stress model parameters using dynamic modeling. Experimental projectiles recording penetration acceleration and temperature at the points of interest on the projectile surface were designed and tested to obtain recorded data. The temperature field in this process was simulated in COMSOL software to calculate the projectile surface's heat flux density and temperature distribution. The results indicate that the developed model is effective. This research infers the physical characteristics of the penetrating target under specified penetration conditions and provides more dimensional information for lunar regolith exploration. [Display omitted] • Heat flux density model of projectile penetrating soil targets including particles flow was developed. • Realized instantaneous temperature measurement of projectile surface. • Heating simulation model was developed to calculate surface temperature distribution. • Presumed maximum temperature of the nose. [ABSTRACT FROM AUTHOR]

Dust mitigation is one of the most crucial aspects of extraterrestrial exploration. This paper presents a series of experiments on the electrodynamic dust shield (EDS) and how UV radiation affects its efficiency on selected lunar simulants (LHS-1 and LMS-1) across a range of particle sizes, quantities, and surface materials. In this experimental study, VUV is used with a 1500 V AC electric field to mobilise the dust particles resting on either glass, Kapton, or Beta cloth inside a vacuum chamber at ∼ 10 - 6 mbar. The dust removal efficiency is characterised by two quantifying methods: weighing and solar array light transmission. The experimental results show that EDS activation under continuous UV exposure on the simulant particles improves the dust removal rate by 40 to 80 percentage points across all surfaces, with the exception of certain particle size ranges on Beta cloth. The primary force facilitating particle mobilisation was identified as the repulsive electrostatic force, enhanced by ionising mechanisms such as photoemission. [ABSTRACT FROM AUTHOR]

• An improved model for thermal extraction of water resource from icy lunar regolith is introduced. • The importance of thermal transpiration is clarified by numerical analysis. • Water migration process during thermal extraction is visually depicted. • Energy Efficiency Ratio (EER) is introduced to evaluate the parametric effect. The confirmation of water ice's existence in the permanent shadow area led to extensive research in the field of water ice mining from icy lunar regolith. A priori numerical simulation of water ice mining is necessary for guiding the development of lunar water ice mining schemes more reasonably. A 2D axisymmetric numerical simulation model capable of simulating the thermal extraction process about mining water ice from icy lunar regolith is constructed, which is executed in the COMSOL Multiphysics. The thermal extraction cases of lunar regolith with different initial water ice content and heating fluxes are simulated. The EER (energy efficiency ratio) is used to evaluate the efficiency of thermal extraction. The results show that the EER is higher as the initial water ice content is increased, which means more power is used to heat water and less power is used to heat the regolith. The icy lunar regolith with initial water ice content higher than 5.0 wt% is found to be more valuable, over which the EER at the end of thermal extraction will not increase much as the initial water ice content increases. However, the higher heating flux leads to the lower EER at the end of thermal extraction. The speed and economics of thermal extraction are suggested to be weighted before the mission's implementation. The status of thermal diffusion (thermal transpiration) is studied, and the results indicate that thermal diffusion and advection both can be ignored in thermal extraction modeling, unless the average magnitude of temperature gradient and pressure gradient exceed the maximum of 75764 K/m and 11053 Pa/m in our calculation cases, respectively. [ABSTRACT FROM AUTHOR]

Nanophase iron (np-Fe) is widely distributed on the surface of lunar soil particles, forming as a result of space weathering. These np-Fe particles contribute to the reddening and darkening of the visible to near-infrared spectra of weathered lunar material and serve as critical indicators for assessing the maturity of lunar soil. (1) This article reviews the proposed formation mechanisms of np-Fe particles from studies of Apollo and Luna soils, including the thermal reduction of iron melts, vapor deposition caused by micrometeorite impacts, and hydrogen reduction due to solar wind exposure. (2) Additionally, recent findings from the analysis of Chang'E-5 lunar soil are highlighted, revealing new mechanisms such as sub-solidus decomposition of olivine, impact-driven disproportionation, and FeO eutectic reactions. (3) Experimental studies simulating space weathering through laser and ion irradiation are also discussed and compared. Despite extensive research, a definitive understanding of np-Fe particle formation remains elusive. Previous lunar soil samples have been collected from the near side of the Moon. This year, the Chang'E-6 mission has successfully returned the first-ever lunar soil samples from the far side. These samples are expected to exhibit unique space weathering characteristics, providing new insights into the formation mechanisms of np-Fe in lunar soil. [ABSTRACT FROM AUTHOR]

The mechanical and thermal properties of the fabricated structures composed of lunar regolith are of great interest due to the urgent demand for in situ construction and manufacturing on the Moon for sustainable human habitation. This work demonstrates the great enhancement of the mechanical and thermal properties of CUG-1A lunar regolith simulant samples using spark plasma sintering (SPS). The morphology, chemical composition, structure, mechanical and thermal properties of the molten and SPSed samples were investigated. The sintering temperature significantly influenced the microstructure and macroscopic properties of these samples. The highest density (~99.7%), highest thermal conductivity (2.65 W·m−1·K−1 at 1073 K), and the best mechanical properties (compressive strength: 370.2 MPa, flexural strength: 81.4 MPa) were observed for the SPSed sample sintered at 1273 K. The enhanced thermal and mechanical properties of these lunar regolith simulant samples are attributed to the compact structure and the tight bonding between particles via homogenous glass. [ABSTRACT FROM AUTHOR]

The cohesive properties of lunar regolith, combined with a low-gravity environment, result in it having a distinct mechanical behavior from sandy soil on Earth. Consequently, empirical formulas derived from cone penetration tests (CPTs) for calculating the shear strength parameters of Earth's sand cannot be directly applied to lunar regolith. This study utilized the three-dimensional discrete element method (DEM) to numerically simulate triaxial shear tests and cone penetration tests in a lunar environment. The particle contact model for lunar regolith in the discrete element method (DEM) simulation incorporated the hysteresis effect of van der Waals forces, thereby simulating the cohesive properties of lunar regolith in a lunar environment. We proposed a relationship for calculating the shear strength index of lunar regolith based on normalized cone tip resistance using the results from triaxial and CPT simulations and referencing empirical formulas derived from ground-based CPT data. The results of this study provide a valuable reference for future lunar CPTs. [ABSTRACT FROM AUTHOR]

Oxygen produced through in‐situ resource utilization (ISRU) is critical to maintaining a permanent human presence on the lunar surface. Molten regolith electrolysis and carbothermal reduction are two promising ISRU techniques for generating oxygen directly from lunar regolith, which is primarily a mixture of oxide minerals; however, both processes require operating temperatures of 1600°C to melt lunar regolith and dissociate the molten oxides. These conditions limit the use of many oxide refractory materials, such as Al2O3 and MgO, due to rapid degradation resulting from reactions between the refractory materials and molten lunar regolith. Yttria‐stabilized zirconia (YSZ) is shown here to be a promising refractory oxide to provide containment of molten regolith while demonstrating limited reactivity. This work focuses on corrosion studies of YSZ powders and dense YSZ crucibles in contact with molten lunar maria and highlands regolith simulants at 1600°C. The interactions between YSZ and molten regolith were characterized using scanning electron microscopy/energy dispersive spectroscopy, X‐ray diffraction, and electron backscatter diffraction. A FactSage thermochemical model was created for comparison with the experimental results. These combined analyses suggest that lunar maria regolith will degrade the YSZ faster than the lunar highlands regolith due to the lower viscosity of the maria regolith. The feasibility of long‐term molten regolith containment with YSZ is discussed based on the YSZ powder and crucible results. [ABSTRACT FROM AUTHOR]

We formulate a method for predicting peak particle forces in a wavefront within a randomly filled 3D granular channel. The wavefronts in our simulation are driven by a sustained impact originating in the bumpy floor of the channel. We show that, when generated in this manner, forces in the driven wavefront within the 3D assembly follow the same power law scaling on material properties and impact velocity as in a 1D chain. A simple scaling of the 1D forces matches results from simulated impact tests we conduct using Soft Sphere Discrete Element method simulations. We then quantify the magnitude of impulse-induced dilation that occurs as a result of varied material properties and gravitational environments, giving an equation that can be used to predict the lofting depth (depth to which particles experience bulk density changes as a result of a laterally propagating wavefront). As predicted by our equation and confirmed with simulated results, dilation is amplified as particle material properties become closer to lunar regolith grains, supporting the hypothesis that impulse-induced surface dilation is the lunar cold spot formation mechanism. [ABSTRACT FROM AUTHOR]

Existing image analysis algorithms cannot achieve consistency with human visual classification results when classifying particles based on angular levels. To address this issue, this paper proposes an image analysis method based on triangle side ratio to quantify particle angularity, referred to as a TSR method. The proposed method utilizes a primary parameter, Mean Angularity, to assess the mean angularity level, and employs three auxiliary parameters to offer insights into the Sharpest Angularity, the Flat Proportion, and the Number of Angularity. When quantifying the angularity, the method further provides the count of convex angles. Each parameter can reflect different characteristic information of the angularity. When using the mean angularity level to order particles, the TSR method achieves the same results as visual classification, and furthermore introduces a range of values for the main parameter corresponding to the different angularity levels. The TSR method is simpler and more stable, since the particle parameters can be calculated directly without contour smoothing, and consistent results are achieved for different shapes with the same degree of angular sharpness. The results of the study on lunar soil, volcanic rock, mechanism stone, and stream stone, show that the TSR method can objectively and comprehensively analyze and quantify the particle angularity. [ABSTRACT FROM AUTHOR]

Lunar exploration and infrastructure development near the Moon's south pole, and at other future lunar settlements, demand a detailed understanding of the geotechnical properties, structure, composition, and stratigraphy of the near-surface lunar regolith. Long term exploration and development activities will require the use of regolith as a construction material for multiple structures, and as unrefined material for resource extraction during in situ resource utilization (ISRU) activities. Upcoming robotic and human exploration will be concentrated near the lunar south pole, which has a dominantly feldspathic composition typical of the lunar highlands. Past missions to lunar highlands terrain (Apollo 16, Luna 20) provide valuable "ground truth" data regarding the geomechanical properties of highlands regolith that serve as a guide for future exploration at the lunar south pole. Lunar highlands simulant LHS-1 has well-characterized geotechnical properties and is an appropriate analogue for highlands lunar regolith in terrestrial engineering studies. Cone penetrometer testing (CPT) measurements of LHS-1 reveal a strong exponential correlation between the G slope parameter and bulk density, which allows information to be obtained regarding the density profile of simulated regolith columns directly from CPT stress versus penetration curves. We show that LHS-1 can be used to replicate the near-surface regolith stratigraphy at the Apollo 16 highland landing region in Earth-based laboratories. The ultimate CPT penetration resistance measured in the laboratory under terrestrial gravity is not directly comparable to that measured under lunar gravity, and here we derive an average reduction factor of Rf = 0.29 to scale penetration resistance values to those measured in situ on the lunar surface. Geotechnical measurements of other lunar simulants combined with experiments similar to those described herein, tailored to the terrain type of interest, will provide crucial information to guide future regolith excavation, construction, and ISRU activities on the lunar surface. • LHS-1 lunar simulant is an appropriate geotechnical analogue for highlands regolith. • A strong correlation exists between CPT penetration resistance and regolith density. • Apollo 16 highlands regolith stratigraphy can be replicated on Earth using LHS-1. • Earth-based CPT values should be reduced by × 0.29 to adjust for lunar conditions. [ABSTRACT FROM AUTHOR]

The oxide-rich lunar surface regolith can be used to extract the oxygen needed for the future of lunar exploration efforts as a consumable for life-support systems and spacecraft propulsion. Various techniques for the extraction of oxygen have been developed already, with solar vapor-phase pyrolysis shown to be a promising yet understudied approach. In contrast to other techniques, it requires only locally available resources, such as unbeneficiated regolith, sunlight, and vacuum in order to liberate oxygen and oxygen-bearing molecules. This study presents experimental work conducted in a purpose-built solar-vacuum furnace showing the evaporation of sodium and iron from a regolith simulant sample and their deposition on the crucible surface. This is matched by the thermochemical equilibrium modeling done in FactSage, which analyzes the process at varying pressures down to ultra-high vacuum. It highlights the need for precise temperature and pressure control, as well as the impact of regolith composition on oxygen dissociation for an efficient extraction of molecular oxygen. • The thermochemical model of the process shows molecular oxygen yields of up to 14.1%. • Low-Titanium Mare is the most promising composition for oxygen production. • Vapor-phase pyrolysis of regolith was demonstrated in a small solar furnace. [ABSTRACT FROM AUTHOR]