In-situ Resource Utilization Research Articles

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.

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.

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.

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.

Lunar Regolith Geopolymer Concrete for In-Situ Construction of Lunar Bases: A Review.

The construction of lunar bases represents a fundamental challenge for deep space exploration, lunar research, and the exploitation of lunar resources. In-situ resource utilization (ISRU) technology constitutes a pivotal tool for constructing lunar bases. Using lunar regolith to create geopolymers as construction materials offers multiple advantages as an ISRU technique. This paper discusses the principle of geopolymer for lunar regolith, focusing on the reaction principle of geopolymer. It also analyzes the applicability of geopolymer under the effects of the lunar surface environment and the differences between the highland and mare lunar regolith. This paper summarizes the characteristics of existing lunar regolith simulants and the research on the mechanical properties of lunar regolith geopolymers using lunar regolith simulants. Highland lunar regolith samples contain approximately 36% amorphous substances, the content of silicon is approximately 28%, and the ratios of Si/Al and Si/Ca are approximately 1.5 and 2.6, respectively. They are more suitable as precursor materials for geopolymers than mare samples. The compressive strength of lunar regolith geopolymer is mainly in the range of 18~30 MPa. Sodium silicate is the most commonly utilized activator for lunar regolith geopolymers; alkalinity in the range of 7% to 10% and modulus in the range of 0.8 to 2.0 are suitable. A vacuum environment and multiple temperature cycles reduce the mechanical properties of geopolymers by 8% to 70%. Future research should be concentrated on the precision control of the lunar regolith's chemical properties and the alkali activation efficacy of geopolymers in the lunar environment.

Oven Design for In‐Situ Thermal Extraction of Volatiles From Lunar Regolith

AbstractExtracting volatiles from lunar regolith for analysis or utilization is one of the most important aspects of future lunar exploration. However, the low thermal conductivity of lunar regolith poses a challenge. Here, we conduct simulations to analyze the heat and mass transfer processes within the sample inside the oven. We identify three main factors affecting oven heat‐up rate: water ice content (WIC) in the regolith, oven diameter, and power supply. Taking these factors into account, we devise an oven design and apply it to three case studies: (a) assessing water ice and isotopic composition in Permanently Shadowed Regions, akin to Chang'e‐7 mini‐fly probe missions; (b) measuring noble gases, as Chang'e‐7 and Luna‐27 landers; and (c) large‐scale in‐situ resources utilization (ISRU). The simulation results indicate that water ice can be extracted using sufficiently high heating power without issues. However, the complete extraction of noble gases is challenging and may require alternative heating methods. For ISRU purposes, large ovens can be subdivided into smaller ones by adding internal structures, for example, honeycomb, to improve the heat‐up rate by at least 1.5 times. Additionally, we find that the oven can serve as a scientific payload for WIC measurement using the heating curve. A flowchart of this new WIC measurement method is provided, offering an alternative method to mass spectrometry or spectroscopy measurements.

Location-dependent flight cost difference from the lunar surface to an orbital fuel depot and its influence on in situ resource utilisation location selection

Given the increasing relevance of lunar activities, the location selection for in situ resource utilisation (ISRU) facilities is necessary for identifying the most suitable configuration during mission planning. To gather information about the dominant location dependencies, a scenario is established wherein an ISRU product is exported to an orbital depot and its mass costs are used for classification. In the selected scenario, oxygen is produced in an ilmenite reduction plant and subsequently exported to the lunar gateway via an oxygen–hydrogen fuelled launcher operated in a round-trip to refuel oxygen at the lunar surface and hydrogen at the lunar gateway. This showed that the transport cost variations could be avoided entirely or have a recessive influence on the mission’s total costs over an extended period of time, such as 20 years. The identification of the top-10 most optimal locations for various resolutions was altered only slightly upon consideration of flight costs as compared to considering only the ISRU factors; this indicates the insignificance of flight cost dependencies for the analysed case.

Radiator production for Pylon Fission Surface Power System through lunar In-Situ Resource Utilization

Background Fission Surface Power (FSP) is currently being considered by NASA for future lunar exploration and Ultra-Safe Nuclear Corporation (USNC) is developing their Pylon FSP system. Methods This paper introduces the system focusing on the materials used for its main components. It also analyses the lunar availability of the elements required to produce these components and suggests that In-Situ Resource Utilization (ISRU) should be considered. Results As a result of the conducted analysis, it is concluded that since mass is the most important parameter when launching payload from Earth, the Pylon component with the largest mass should be considered further. The heaviest system component is the power system which, however, consists of many other components that are made from various materials. The second heaviest component is the radiator made of Titanium (Ti) metal heat pipes and Graphite Fiber Reinforced Composite (GFRC) face sheets with water as the working fluid. Since the production of Ti metal on the Moon is non-economical, Aluminum (Al) metal utilized for the International Space Station (ISS) is considered. Lunar infrastructure required to produce Al using ISRU is already available. Further analysis will be conducted in the future to look into laser 3D printing technologies. Lunar Resources Inc. is already developing techniques for Al extraction from regolith for the production of Al wires. Conclusions This research shows that all the required technologies already exist, and the next step will be to identify how the obtained Al can be manufactured into radiators. It will also be important to identify how much of the total radiator mass is Al metal to increase the fidelity of this analysis Future research will find the break-even point between the Pylon Ti radiators launched from Earth and the production of Al radiators on the Moon.