In-situ Resource Utilization Research Articles

Carbon Nanotube Reinforced Lunar-Based Geopolymer: Curing Conditions

Current space exploration focuses on returning to the Moon to expand space exploration capacity by improving technology. The long-term presence of humans and robots on the Moon requires the development of durable habitats for space missions. In recent decades, in situ resource utilization (ISRU) for construction materials has been recognized as a viable option. However, the addition of nanomaterials, which exhibit a high strength-to-weight ratio, has not been incorporated with the ISRU framework in space missions. This paper investigates the impact of carbon nanotubes (CNTs) on lunar simulant-based geopolymers’ compressive strength and water retention. The evaluation of water retention indicates another potential in water recapturing capability. In this study, CNTs can enhance the mechanical properties of lunar simulant-based geopolymer. Two lunar simulants were used, representing the Highland and Mare regions of the Moon. Experimental variables included CNT concentration, four curing regimes (ambient curing, two oven-curing methods, and microwave radiation), and dispersion time in aqueous solutions. Results showed that CNTs can positively influence both strength gain and water retention during curing regimes, but the extent of influence appears to be dependent on simulant type and curing regime. The Highland simulant consistently outperformed the Mare simulant in oven-curing regimes from a strength perspective, regardless of CNT presence. The strength benefits of CNTs were more pronounced at ambient curing temperatures. Even under poor curing conditions—where water availability may be limited at temperatures of 80 °C—CNTs aid in retaining water within the geopolymer matrix, leading to improved strength compared to counterparts. Under the same conditions, a higher concentration of CNTs further confirmed their role in water retention during geopolymerization, with consistently greater water retention observed in samples containing CNTs. Additionally, microwave radiation was explored as an alternative to conventional oven drying, showing potential for reducing curing duration. Finally, the findings suggest that combining CNTs and microwave radiation could enhance water recovery and reuse, contributing to the development of high-strength infrastructure materials on the Moon with reduced energy and cost requirements.

Soil flow behavior in baffled rotary drum based icy lunar regolith simulant preparation

Icy lunar regolith(ILR) exists in lunar permanently shadowed regions. The preparation of ILR simulant is crucial for conducting ground-based tests for in-situ resource utilization(ISRU). To improve the fidelity of ILR, a novel method for ILR preparation was introduced, termed the water molecule deposition coating(WMDC) method, anchored in the natural formation mechanism of ILR. The cold regolith particles undergo complete tumbling, effectively trapping the water molecules. ILR samples were evaluated for uniformity in water content and micro-morphological characteristics to substantiate the effectiveness of this method. The discrete element method(DEM) was used to analyze the motion and mixing processes of lunar regolith particles within a baffled rotary drum and to determine the impact of various conditions on particle flow behaviors. The results revealed positive correlations between rotation speed, baffle number, and filling degree with central particle density (CPD), with optimal mixing index (MI) achieved at higher rotation speeds and lower filling degrees.

Impacts of thermal activation on lunar regolith simulant-based precursor and resulting geopolymer: Composition, structure, solubility, and reactivity

Alkali activation presents a promising method for the in situ resource utilization (ISRU) of lunar regolith. Enhancing the geopolymerization reactivity of lunar regolith simulant is key in minimizing alkali activator usage and improving raw material utilization. This study investigates the impact of thermal activation on precursor materials and the resultant geopolymers. Initially, the mineralogical composition and chemical structural changes in thermally activated samples were analyzed using XRD-Rietveld, XPS, and Raman spectroscopy. Subsequently, ICP-OES was employed to measure the solubility of various thermally activated samples in NaOH solution. Finally, the physicochemical composition and microstructure of the geopolymers were evaluated using SEM-EDS, FTIR, DSC, and compressive strength tests. The results show that thermal activation enhances precursor reactivity by increasing the non-bridging oxygen (NBO) content, reducing polymerization, and altering the binding energies of Si, Al, and O. Following thermal activation, the solubility of Si and Al in the NaOH solution was significantly improved. A more comprehensive thermal activation process produces geopolymers with improved compressive strength, a higher reaction degree, and a denser microstructure, and encourages the formation of Si-rich gels. Hence, treating precursor materials via thermal activation offers vast potential for creating lunar regolith geopolymer-based building materials with excellent properties.

Coupling thermodynamic modelling with experimental study to reveal the evolutionary relationship of pore solutions, products, and compressive strength for lunar regolith simulant geopolymers

Alkali-activation is a highly promising approach for the in situ resource utilisation (ISRU) of lunar regoliths. However, the considerable variation in the composition of lunar regolith simulants can complicate the optimal design of geopolymer mixture ratios, necessitating an in-depth analysis of composition–performance correlations. This study proposes a calculation method that couples thermodynamic modelling with an experimental study to reveal the evolutionary relationship between the pore solution, product formation, and compressive strength. The results indicate that the modulus and dosage of the alkali activator can substantially change the relative content of reactive elements in the pore solution and affect the product type and content. Among these, [Si] and [Al] in the pore solution and gel production are key factors affecting the compressive strength of geopolymers. Understanding these composition–performance relationships is critical for offering essential guidance for performance-based, on-demand material design and optimisation.

The Dehydration of Serpentines and Extraction of Water

Some groups of carbonaceous chondrites are dominated by phyllosilicates, specifically the serpentine group, which are characterized as alternating layers of silicates, metal cations, and hydroxyl (OH). Both antigorite, an Mg-rich member, and cronstedtite, an Fe-rich member, can be found in hydrated carbonaceous chondrites. Cronstedtite is found in substantial amounts in CM chondrites. The hydroxyl can make up to a quarter of the molecular mass, and part of it can turn into molecular water through thermal-induced crystal structure breakup. Understanding how the water is released through thermal effects is important for describing the history of certain near-Earth asteroids, as well as for ascertaining the viability of in situ resource utilization (ISRU) for a given object. Here we investigate the temperature of dehydration of the main serpentine constituents of carbonaceous chondrites—antigorite, lizardite, and cronstedtite—under both atmospheric and vacuum conditions. Our results show that the mass loss for cronstedtite starts at about 150 °C lower temperature than for the Mg serpentines. Additionally, vacuum does not affect significantly the onset of the mass loss, but it affects its dynamics. Finally, our observations suggest that cronstedtite loses additional oxygen molecules besides the ones contained within the hydroxyl. These results provide an important new perspective on the orbital history of certain asteroids and the required proximity to the Sun in order for them to lose water. Additionally, it puts the CM-type asteroids on the center stage for ISRU.

Modeling and simulation of a full ISRU-based system for energy storage and electricity generation on the Moon

The survival of the crew and assets during the lunar night is one of the biggest challenges in the exploration of the Moon. The storage and supply of energy are key elements for the success of a mission. We present an EcosimPro model and numerical simulations of a system based on In-Situ Resource Utilisation (ISRU) that stores solar energy during the day and generates electricity during the night. We carried out analyses of each subsystem as well as simulations of the full system. Estimates of the performance of the system in terms of power output and mass of the system are presented. Results show that the ISRU-based thermal energy storage and electricity generation system is very competitive in comparison to a system composed of photovoltaic panels and batteries.

Selective laser melting of partially amorphous regolith analog for ISRU lunar applications

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.

Liquid Rocket Engine Performance Characterization Using Computational Modeling: Preliminary Analysis and Validation

The need to refuel future missions to Mars and the Moon via in situ resource utilization (ISRU) requires the development of LOX/LCH4 engines, which are complex and expensive to develop and improve. This paper discusses how the use of digital engineering—specifically physics-based modeling (PBM)—can aid in developing, testing, and validating a LOX/LCH4 engine. The model, which focuses on propulsion performance and heat transfer through the engine walls, was created using Siemens’ STAR-CCM+ CFD tool. Key features of the model include Eulerian multiphase physics (EMP), complex chemistry (CC) using the eddy dissipation concept (EDC), and segregated solid energy (SSE) for heat transfer. A comparison between the complete GRI 3.0 and Lu’s reduced combustion mechanisms was performed, with Lu’s mechanism being chosen for its cost-effectiveness and similar output to the GRI mechanism. The model’s geometry represents 1/8th of the engine’s volume, with a symmetric rotational boundary. The performance of this engine was investigated using NASA’s chemical equilibrium analysis (CEA) and STAR-CCM+ simulations, focusing on thrust levels of 125 lbf and 500 lbf. Discrepancies between theoretical predictions and simulations ranged from 1.4% to 28.5%, largely due to differences in modeling assumptions. While NASA CEA has a zero-dimensional, steady-state approach based on idealized conditions, STAR-CCM+ accounts for real-world factors such as multiphase flow, turbulence, and heat loss. For the 125 lbf case, a 9.2% deviation in combustion chamber temperature and a 15.0% difference in thrust were noted, with simulations yielding 113.48 lbf compared to the CEA’s 133.52 lbf. In the 500 lbf case, thrust reached 488 lbf, showing a 2.4% deviation from the design target and an 8.6% increase over CEA predictions. Temperature and pressure deviations were also observed, with the highest engine wall temperature at the nozzle throat. Monte Carlo simulations revealed that substituting LNG for LCH4 affects combustion dynamics. The findings emphasize the need for advanced modeling approaches to enhance the prediction accuracy of rocket engine performance, aiding in the development of digital twins for the CROME.

Use of Extraterrestrial Resources and Recycling Water: Curb Your Enthusiasm

The NASA approach for technology development for missions is to (1) wait for a mission need, and (2) upgrade the technology available at that time, however inadequate. This is illustrated with two important NASA technologies: in situ resource utilization (ISRU) and recycling wastewater. It also serves as a review with 49 references provided. NASA funding for ISRU has been sporadic and minimal, probably because no mission was being implemented that used ISRU. The state of the technology remains underdeveloped. For example, CO2 in the Mars atmosphere supplies carbon and oxygen. However, we still do not have a viable system to acquire CO2 and compress it with acceptable power requirements and adequate lifetime. NASA technology for recycling wastewater was developed for the International Space Station. It requires frequent attention with replenishment and replacement of subsystems. This system appears to be inadequate for Mars missions and there is no evidence that NASA has a viable plan to fix that.

Raman characterization of lunar highlands simulants for in-situ resource utilization in a lunar setting

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).

Flash sintering of HUST-1 lunar regolith simulant: Effects of processing temperature on microstructure characteristics and mechanical properties

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.

Simulating lunar highlands regolith profiles on Earth to inform infrastructure development and ISRU activities on the Moon

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.

A moderate-Ti lunar mare soil simulant: IGG-01

Lunar soil simulants play a crucial role in scientific research, payload tests and in-situ resource utilization (ISRU) experiments. However, the currently available lunar soil simulants are either low in TiO2 content (≤3 wt%) or high in TiO2 content (≥6.7 wt%), despite orbital observations indicating lunar soils with moderate TiO2 content being widely distributed on the lunar surface. In December 2020, China's Chang'e−5 (CE-5) mission successfully returned a new mare soil sample characterized by high FeO content (22.5 wt%) and moderate TiO2 content (5.5 wt%), providing an opportunity to develop moderate-TiO2 lunar soil simulants. This study presents a newly developed simulant of the CE-5 lunar soil named IGG-01, which closely replicates the major physical and chemical properties of the CE-5 lunar soil. The median particle size of IGG-01 is 68.69 ± 4.44 μm, and its estimated specific surface area is 0.34 m2/g. It contains 17.6 wt% FeO and 4.8 wt% TiO2. It consists of pyroxene (49.3 wt%), plagioclase (40.9 wt%), ilmenite (6.1 wt%), and olivine (3.7 wt%), with specific gravity and bulk density are 3.33 g/cm³ and 1.86 g/cm³, respectively. The friction angle is 41.8°, and the cohesion is 19.2 kPa. It exhibits strong and weak reflectance absorption features in the 1 and 2 μm band centers. The physical properties of IGG-01 are also comparable to those of Apollo samples and typical lunar mare soil simulants. The unique chemical composition of IGG-01 makes it suitable for various scientific and engineering experiments, including but not limited to the study of dusty plasma migration, water formation via solar wind injection, oxygen preparation via hydrogen reduction, and tests involving the movement of rovers and excavation equipment.

Additive manufacturing development of construction materials for a lunar base via spark plasma sintering of volcanic rocks using in-situ resource utilization concept

This work presents an innovative approach for creating ceramic materials based on andesite-basalts for construction on the Moon. Employing the concept of in-situ resource utilization (ISRU), the authors simulated the composition of lunar regolith using volcanic rocks from Kamchatka and Primorsky Krai (Russia, Far East). These rocks were ground into submicron powders and sintered via spark plasma sintering (SPS) at temperatures of 800, 900, and 1000 °C. The resulting ceramic samples demonstrate exceptional physicomechanical properties comparable to lunar regolith – compressive strength up to 566 MPa and Vickers hardness up to 650 HV. Optimal characteristics were achieved at a sintering temperature of 1000 °C with a heating rate of 300 °C/min. It was determined that the heating rate during sintering has a decisive influence on the density of the resulting ceramics.This research vividly demonstrates the potential of SPS technology and the ISRU concept for creating high-strength construction materials on the Moon using local lunar raw materials, paving the way for large-scale construction of lunar bases utilizing the Moon's own mineral resources.

Electromagnetic Characterization of EAC-1A and JSC-2A Lunar Regolith Simulants.

The development of devices for the in situ resource utilization (ISRU) of lunar surface powder (regolith) by means of microwaves needs regolith simulants with electromagnetic properties similar to the lunar regolith. This document deals with the measurement of complex permittivity and dielectric loss tangent of the aforementioned simulants at ambient temperature from 400 MHz to 20 GHz, performing measurements using two lunar dust simulants, EAC-1A and JSC-2A, resulting, on the one hand, in permittivity values of ε'=-0.0432f+4.0397 for the EAC-1A lunar dust simulant and ε'=-0.0432f+4.0397 for the JSC-2A simulant, and on the other hand, in loss tangent values of tanδe=-0.0015f+0.0659 for the EAC-1A powder and tanδe=-0.0039f+0.1429 for the JSC-2A powder. In addition, further studies are carried out taking into account the humidity of the samples and their densities at room temperature. The obtained results are applicable for comparing the measured values of EAC-1A and JSC-2A between them and with other previously measured simulants and real samples. The measurements are carried out by applying two different nonresonant techniques: Open-Ended Coaxial Probe (OECP) and transmission line. For this purpose, the DAK and EpsiMu commercial kits are used, respectively.

On the viability of electrochemical carbon dioxide in-situ resource utilization to produce chemical feedstocks on Mars

The long-term, crewed exploration of Mars is a priority for both national and private space entities. Given economical constraints on the mass sent off-world from Earth, in situ resource utilization (ISRU) through ultra-low temperature CO2-H2O electrolyzer technology that is fed using the Martian atmosphere’s CO2 (∼95 %) and the subsurface Martian water cycle (enabled by perchlorate salts that depress the Martian brine’s freezing point to < 213 K) has been proposed as a pathway towards fuel and chemical feedstock. Herein we applied a validated, computationally frugal electrolyzer model to a Martian CO2-H2O electrolyzer and examined its viability. Through a judicious combination of catalysts, such electrolyzers could produce O2, CO, HCHO, CH3OH, CH4, C2H4, and C2H5OH even at ambient Martian temperatures (∼237 K). Our modeling herein shows the theoretical production of these key resources in acidic electrolyzers to be at a scalable rate of 0.052 – 1.13 g per cm2 per day of CO, 0.0004 – 0.086 g per cm2 per day of CH3OH, 0.001–0.048 g per cm2 per day of CH4, 0.0164 – 0.171 g per cm2 per day of C2H4, 0.008 – 0.0125 g per cm2 per day of C2H5OH. A range of catalyst candidates were examined for product selectivity, energy efficiency and throughput. Ambient temperature CO2-H2O electrolysis is shown to be an energy efficient approach to chemical feedstocks needed for the sustained exploration of Mars and beyond. This model can inform future astronaut life support device development for NASA and other space faring entities.

Geological evidence for extensive basin ejecta as plains terrains in the Moon’s South Polar Region

Water ice and other volatiles that accumulated in the Moon’s polar regions are among the top priority targets for lunar exploration, due to their significances in both lunar geology and extraterrestrial resource utilization. Locating suitable landing sites and determining the provenance of sampled/measured surface materials are critical for future landed missions. Here, we map over 800 sites of plains terrains in the Moon’s south polar region, with a total surface area of ~46,000 km2. Orbital measurements and analog studies show that most of these plains have apparently higher albedo and lower iron content than volcanic mare plains, suggesting an origin of ejecta-induced debris flows from distant impact craters, especially from the Schrödinger basin. Our findings suggest that the entire lunar south polar region probably have experienced contributions from distant basin materials. We recommend these plains as priority landing sites for future exploration of lunar polar volatiles and early bombardment history.

CONCENTRATION OF LUNAR PLAGIOCLASE FOR SOLAR CELLS FABRICATION. AN ISRU CONCEPTUAL ARCHITECTURE

Solar panels are required on the Moon to provide power for human activities, especially mining and civil operations. To provide enough power and maintain human settlements working, a technical solution known as the Tall Lunar Tower (TLT) claims to be able to capture sunlight 93% of the time through solar panel structures and provide 50 kW per tower. A typical photovoltaic panel is made of 76% glass, 10% polymer, 8% aluminum, 5% silicon, and 1% other metals. Delivering these materials from Earth is expensive and risky. Fortunately, lunar regolith contains large amounts of silicon and aluminum oxides and silicates, thus, it would be feasible to use the resources in situ for metal production, hence, we just need to transport polymers, wire, and minor components from Earth. This article presents an ISRU (in-situ resource utilization) architecture to provide plagioclase concentrate, the economic lunar ore for aluminum and silicon extraction. The document details engineering aspects and technological solutions for lunar mining, including excavation, transport, and beneficiation operations; based on a hypothetical construction and deployment of TLT at the South Pole. Processing techniques such as screening and magnetic separation are discussed to evaluate their advantages and drawbacks to obtain an expected plagioclase concentration of 70% grade with 18% recovery. Finally, an outline of recommendations for industrial manufacture is discussed, considering the sequential lunar metals extraction and the quality required.

Synthetic space bricks from lunar and Martian regolith via sintering

The prospect of establishing extra-terrestrial habitats using in situ resource utilization (ISRU) constitutes a long-term goal of multiple space agencies around the world. In this work, we investigate furnace sintering as a potential route for making building blocks—termed synthetic space bricks—using in situ regolith material. By systematically evaluating sintering parameters using a numerical lattice model, coupled with experimental observations and post-sintering characterization, we propose a process protocol for two lunar simulants (lunar highland simulant (LHS-1) and lunar mare dust simulant (LMS-1)) and one Martian simulant (mars global simulant, MGS-1). The resulting bricks demonstrate compressive strengths of up to 45 MPa under uniaxial loading, depending on the simulant used. These strengths are much greater than those typically mandated for structural applications under reduced gravity. Taking recourse to classical ceramic sintering studies, we infer particle-level sintering mechanisms indirectly by measuring temporal evolution exponents of sample dimensions. For all three simulants, volume diffusion appears to be the primary mechanism for particle coalescence. Our results clearly make a strong case for the use of sintering as a potentially scalable method for consolidating regolith into brick-like structures for construction and load-bearing applications in extra-terrestrial settings.

Autonomous construction of lunar infrastructure with in-situ boulders

Significant infrastructure is required to establish a long-term presence of humans on the lunar surface. In-situ resource utilization (ISRU) is a fundamental approach to ensure the viability of such construction. Here, we investigate the feasibility of constructing blast shields as one example of lunar infrastructure using unprocessed lunar boulders and an autonomous robotic excavator. First, we estimate the volume of unprocessed material required for the construction of blast shield segments. Secondly, we quantify the amount of available boulders in two exploration zones (located at the Shackleton-Henson Connecting Ridge and the Aristarchus Plateau pyroclastic deposit) using LRO NAC images and boulder size-frequency distribution laws. In addition, we showcase an alternative approach that relies on Diviner rock abundance data. Thirdly, we use a path planning algorithm to derive the distance, energy, and time required to collect local material and construct blast shield elements. Our results show that our construction method requires two orders of magnitudes less energy than alternative ISRU construction methods, while maintaining realistic mission time and payload capacity margins.