Lunar soil, as an in-situ resource, holds significant potential for constructing bases and habitats on the Moon. However, such constructions face challenges including limited mechanical strength and extreme temperature fluctuations ranging from -170 degrees C to +133 degrees C between lunar day and night. In this study, we developed a 3D-printed geopolymer derived from lunar regolith simulant with an optimized zig-zag structure, exhibiting exceptional mechanical performance and thermal stability. The designed structure achieved remarkable damage tolerance, with a compressive strength exceeding 12.6 MPa at similar to 80 vol% porosity and a fracture strain of 3.8 %. Finite element method (FEM) simulations revealed that the triangular frame and wavy interlayers enhanced both stiffness and toughness. Additionally, by incorporating strategically placed holes and extending the thermal diffusion path, we significantly improved the thermal insulation of the structure, achieving an ultralow thermal conductivity of 0.24 W/(m K). Furthermore, an iron-free geopolymer coating reduced overheating under sunlight by 51.5 degrees C, underscoring the material's potential for space applications.

In situ resource utilization of lunar regolith provides a cost-effective way to construct the lunar base. The melting and solidifying of lunar soil, especially under the vacuum environment on the Moon, are the fundamentals to achieve this. In this paper, lunar regolith simulant was melted and solidified at different temperatures under a vacuum, and the solidified samples' morphology, structure, and mechanical properties were studied. The results indicated that the density, compressive strength, and Vickers hardness of the solidified samples increased with increasing melting temperature. Notably, the sample solidified at 1400 degrees C showed excellent nanohardness and thermal conductivity originating from the denser atomic structure. It was also observed that the melt migrated upward along the container wall under the vacuum and formed a coating layer on the substrate caused by the Marangoni effect. The above results proved the feasibility of employing the solidified lunar regolith as a primary building material for lunar base construction.

The lunar base establishing is crucial for the long-term deep space exploration. Given the high costs associated with Earth-Moon transportation, in-situ resource utilization (ISRU) has become the most viable approach for lunar construction. This study investigates the sintering behavior of BH-1 lunar regolith simulant (LRS) in a vacuum environment across various temperatures. The sintered samples were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), along with nanoindentation, uniaxial compression, and thermal property tests to evaluate the microstructural, mechanical, and thermal properties. The results show that the sintering temperature significantly affects both the microstructure and mechanical strength of the samples. At a sintering temperature of 1100 degrees C, the compressive strength reached a maximum of 90 MPa. The mineral composition of the sintered samples remains largely unchanged at different sintering temperatures, with the primary differences observed in the XRD peak intensities of the phases. The plagioclase melting first and filling the intergranular pores as a molten liquid phase. The BH-1 LRS exhibited a low coefficient of thermal expansion (CTE) within the temperature range of - 150 degrees C to 150 degrees C, indicating its potential for resisting fatigue damage caused by temperature fluctuations. These findings provide technical support for the in-situ consolidation of lunar regolith and the construction of lunar bases using local resources.

The solidification and molding of lunar regolith are essential for constructing lunar habitats. This study introduces an innovative lunar regolith molding technique that synergistically combines solar concentration, flexible optical fiber bundle energy transfer, and powder bed fusion. A functional prototype is developed to validate the proposed scheme. Systematic experiments including fixed beam spot melting, line melting, surface melting, and body melting are conducted using simulated basalt lunar regolith. Through in-situ observation of the melt pool's formation, evolution, and expansion dynamics, we identify a sequential transformation mechanism on the powder bed's surface: initial curling evolves into detachment from the bed, subsequent incorporation into a molten droplet, and ultimate solidification. A comprehensive evaluation of density and mechanical properties across multiple parameter combinations reveals that energy flux density of 3.33 MW/m2 with a scan speed of 30 mm/min, inter-track spacing of 3 mm, and layer thickness of 2 mm enables the production of structurally integral samples with continuous morphology. The resulting specimens demonstrate a maximum compressive strength of 4.25 MPa and a density of 2.31 g/cm3. This solar-powered additive manufacturing approach establishes a viable reference framework for large-scale on-site construction of lunar research stations.

Preparing regolith-based composites for 3D printing is crucial in lunar base construction, leveraging costeffective and mechanically favorable materials for lunar construction by utilizing lunar regolith as the reinforcing phase. This research focuses on developing lunar regolith simulant as a matrix for 3D printing, which is crucial for in-situ resource utilization on the Moon. Resin-based composites, well-established in aerospace, are explored for their simple manufacturing and robust properties. The formulation involves simulated regolithbased polymer for direct ink writing printing. Rheological properties, including yield stress and plastic viscosity, are characterized across various cementite-sand ratios and printing temperatures. The relationship between extrudability, the time interval of the printing material and its rheological attributes is investigated. Quantitative assessment of material buildability employs three-dimensional scanning of the printed parts. Freeze-thaw cycle tests explore its temperature resilience. The influence of varying the printing infill rate on printing efficiency and the performance of the printed parts was assessed. It was found that modulating the printing infill rate affects the efficiency and performance of parts, with a 1:4 cementite-sand ratio and a 40 degrees C print temperature demonstrating optimal printing workability. These findings offer an efficient scheme for the automated production of regolithbased epoxy composites with precise structural, temperature-resistant, and favorable mechanical properties.

Grain size distribution (GSD) is crucial for understanding soil properties and surface processes. We find that both terrestrial soils and lunar soils are subjected to a unified GSD function, P(D)= g(mu )D-mu exp(-D/Dc), reducing the textural fractions and grade modes to a parameter pair (mu, Dc), which unifies terrestrial and extraterrestrial soils in granular configuration, beyond the environments and mechanisms of soil genesis. To construct a framework of the soil formation, we generalize the textural composition to a grade space representing the granular configuration, and conceptualize soil genesis as the random aggregation of the fractal fragmentation of parent lithospheric material and fragments from other sources (e.g., meteorites impacts or surface transport processes). Random simulation reproduces the multiple grade modes observed in soils, and spontaneously derives the unified GSD function. Then we numerically generate the (mu, Dc)-fields for soils on earth and moon, which refine the digital data mapping based on site measurements and depict the local fluctuation of soil parameters. The GSD unity also provides a tool of generating numerical simulants of lunar soils to fill the gap in material simulants. The study leads to a GSD-paradigm (in contrast to the conventional landscape-paradigm) in soil study, which is expected to facilitate the data harmonization on earth and promote the generation of lunar regolith data in favor of the in-situ resource utilization and base construction on moon.

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 singlelayer-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.

The technology of 3D printing, referred to as additive manufacturing, is widely acknowledged as a transformative innovation that has the potential to supplant traditional processing methods in numerous domains. The present study showcases a quantitative assessment of the mechanical properties of moon dust, also known as Lunar Regolith Simulants (LRS), printed through vat polymerization. In this study, we conduct a thorough investigation and explore the effects of layer height [LH] (LH = 10 mu m, 20 mu m, 30 mu m, 40 mu m, 50 mu m, 60 mu m]), exposure time [ET] (ET = 3000 ms, 5000 ms, 7000 ms, 11,000 ms), and sintering impact [1075 degrees C, 1082 degrees C, 1083 degrees C, 1085 degrees C, 1086 degrees C, 1087 degrees C, 1090 degrees C] on the mechanical properties of printed structures. Herein, we utilize a 55 % volume suspension of LRS to print rod and block configurations via digital light printing [DLP] that are subsequently consolidated through sintering in ambient air. This 55 % LRS via vat polymerization approach has not been previously reported. The morphology of the simulant powders exhibited irregular and angular features. Our experimental results show that a 30 um (LH) with (ET) 11,000 ms exhibits maximum compressive and flexural strength of 330 MPa and 100 MPa at 1085 degrees C. The sintering atmosphere greatly affects the microstructure, macroscopic features, and mechanical strength of 3D-printed LRS, which reveals diverse chemical compositions and underlying reaction mechanisms. This sintering process improves particle bonding, resulting in densification and reduced voids within the 3D-printed structure. It is essential to optimize the annealing parameters to achieve the desired strength while avoiding excessive sintering that may cause dimensional distortions or structural defects. This innovative approach opens new possibilities for future space exploration and extraterrestrial construction.

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.

In-Situ Resource Utilisation (ISRU) is increasingly being seen as a viable and essential approach to constructing infrastructure for human habitation on the moon. Transporting materials and resources, from Earth to the Moon, is prohibitively expensive and not sustainable for long-term, large-scale development. Various fabrication technologies have been investigated in recent years, designed for extra-terrestrial exploration and settlement. This review presents a comprehensive study on the development of several sintering techniques of lunar regolith simulant to demonstrate its feasibility for ISRU on the moon. Various critical processing parameters are evaluated in pursuit of creating a structural material that can withstand the extreme lunar environment. Key outcomes are summarised and assessed to provide insight into their viability. Finally, current challenges are addressed and potential improvements, and avenues for further research, suggested.