JSC-1A Lunar Regolith Simulant Research Articles

Thermodynamic and experimental study on carbothermal reduction of JSC-1A lunar regolith simulant for metal and metalloid production

The carbothermal reduction of JSC-1A lunar simulant with activated carbon was investigated for producing metals and metalloids. Chemical equilibrium compositions were examined using Gibb’s free energy minimization to identify favorable operating temperatures at 0.1, 10-8, and 3 × 10-15 bar for Fe and Si production. Complete conversion of Fe2O3 to Fe(g) was predicted at temperatures above 850 °C and about 90 % conversion of SiO2 to Si(g) was predicted at temperatures above 1000 °C for lunar surface pressure of 3 × 10-15 bar. Thermogravimetry was used to examine the reactions with mixtures of JSC-1A and stoichiometric activated carbon in 100 % Ar up to 1500 °C, and comparisons between temporal mass losses and CO evolution were used to estimate volatile production. The results were compared to ultra-high vacuum experiments at ∼ 10-12 bar with temporal CO measured. Solid-state surface material characterization was performed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy to identify elemental distributions and particle morphology of sample surface before and after experiment as well as chemical compositions present after experiment. Changes in elemental distributions and morphologies of Si-, Fe-, and Ti- in the sample before and after the experiment provided strong evidence of reactions of Si-, Fe-, and Ti- compounds in JSC-1A. Characterization of the loose sample after TGA confirmed the presence of crystalline SiC, Si, and Fe. Deposits collected on Cu foils mounted above the sample in the ultra-high vacuum experiments were found to contain Fe-, Al-, Mg-, and Si- volatiles.

Outgassing behavior and heat treatment optimization of JSC-1A lunar regolith simulant

As NASA strives towards a long duration presence on the Moon, it has become increasingly important to learn how to better utilize resources from the lunar surface for everything from habitats, vehicle infrastructure, and chemical extraction. To that end, a variety of lunar simulants have been sourced from terrestrially available volcanic minerals and glass as Apollo regolith is unavailable for experimentation needing large masses. However, while mineralogy and chemical composition can approach that of lunar material in these simulants, there are still distinct non-lunar phases such as hydrates, carbonates, sulfates, and clays that can cause simulants to behave distinctly non-lunar in a variety of processing conditions that maybe applied in-situ to lunar material. Notably, severe glassy bubbling has been documented in a variety of vacuum sintering experiments on JSC-1A lunar mare simulant heated via microwaves. The origins of this outgassing have not been well understood but are normally attributed to the decomposition of non-lunar contaminates intrinsic to virtually all terrestrially sourced simulants. As such, a series of controlled environmental tests were performed to ascertain the origins of the high temperature outgassing and to develop heat treatments that can drive JSC-1A closer to lunar composition and behavior. It was found that in JSC-1A at elevated temperatures distinct gas evolutions of water, carbon dioxide, and sulfur dioxide occur in both inert gas and vacuum. Additionally, the presence of hydrogen during heat treatments was shown to dramatically change gas evolutions, leading to distinctly more lunar-like composition and behavior from JSC-1A simulant.

Marangoni effect and its potential utilization in supporting lunar habitats and other extraterrestrial endeavors

Tears of wine is a phenomenon frequently observed as a ring of wine formed near the top of the glass generates droplets that fall back into the wine. This phenomenon can be explained by the Marangoni effect driven by the surface tension created via gradient on concentration and temperature along the interface between two phases. Besides being observed while drinking wine, the Marangoni effect is crucial for welding metals, manufacturing integrated circuits, and growing crystals. This paper aims to establish that the Marangoni effect has the potential to be also crucial supporting lunar habitats and other extraterrestrial endeavors, as vacuum and reduced gravity are expected to augment the Marangoni effect on extraterrestrial molten soil leading to sustainable extraterrestrial in-situ resources utilization (ISRU). The authors conducted a Marangoni effect assessment on molten lunar regolith via JSC-1A lunar regolith simulant under vacuum yielding a spontaneous upwards migration of a uniform molten thin-film front as well as at bulk scale that climbed the crucible wall covering the entire wall’s surface and reaching the crucible’s top end. This unique formation and self-migration of a thin-film front could enable key ISRU processes such as, thin-film coating, crystal growth, and feedstock generation for additive 3D printing. Further assessment on higher-temperature vacuum-driven decomposition of the uniform thin-film front as it climbed the crucible’s wall revealed a significant decomposition of various simulant’s metal-oxide components into their respective oxygen and metal elements strengthening the feasibility of extraterrestrial generation and fractional separation of oxygen and metals/alloys with none or minimal need for terrestrial precursors. These two-coupled phenomena, spontaneous material transportation at both thin-film and bulk scales via Marangoni effect and vacuum-driven decomposition open novel pathways in extraterrestrial mining and manufacturing. Future extraterrestrial mining will require an operational approach completely different from the terrestrial one that heavily relies on not only mechanical excavation and transportation but also on a stand-alone refinery process to extract the mineral components. In this paper, the authors propose an extraterrestrial all-in-one mining process in which the Marangoni effect would allow non-mechanical transportation of the extraterrestrial mineral to feed an also in-situ pyrolysis-based refinery unit.

A non-motorized spectro-goniometric system to measure the bi-directional reflectance spectra of particulate surfaces in the visible and near-infrared.

Reflectance spectroscopy is a powerful tool for remotely identifying the compositional and physical properties of surface materials. Due to the anisotropic scattering nature of most surfaces, the spectral features, including the absolute reflectance value, spectral slope, and band depth, are influenced by illumination and viewing configurations. Therefore, it is important to understand how spectral features vary with illumination and observation geometries for various particulate surfaces through laboratory measurements. Here, we describe a non-motorized spectro-goniometric system capable of measuring the bi-directional reflectance of particulate surfaces in the upper hemisphere in the wavelength range from 350 to 2150nm. The incident and the viewing zenith angles can be varied from 0° to 55° and from 0° to 70°, respectively. The relative viewing azimuth angle can be varied from 0° to 360°. Measurements on Labsphere Spectralon agree well with measurements done with other instruments. We also present measurement results on two typical planetary analog materials, the JSC-1A Martian soil simulant and the JSC-1A lunar regolith simulant.

Penetration and relaxation behavior of JSC-1A lunar regolith simulant under cryogenic conditions

Lunar in situ resource utilization discussions have recently been focused on the presence and distribution of ice in the upper layers of surface regolith, in particular within the confines of the permanently shadowed regions. Extraction ideas - ranging from simple scooping to percussive drilling and thermal (optical) mining utilizing cold-trap volatile capture – require detailed knowledge of the mechanical properties of icy regolith as we are likely to encounter. Penetrometers provide a robust and straightforward measurement technique for determining soil properties, but previous research fails to reliably show measurement sensitivity to increasing ice content due to difficulties in experimentation at cryogenic conditions. To display the capability of a simple conical penetrometer to discern saturation levels of icy regolith simulant within an expected range, we conducted laboratory penetration and subsequent relaxation measurements of JSC-1A lunar simulant using a specially-designed cryogenic apparatus which minimizes sample temperature fluctuation as well as the thermal mismatch between the penetrating probe and tested sample. We measured penetration resistance and force relaxation behavior for JSC-1A lunar simulant under constant displacement rate penetration at ~300 mTorr pressure, ~110 K sample temperature, 170 K to 190 K probe temperature, and ice contents of 0% to 12% and 100%. Penetration resistance and relaxation behavior both showed sensitivity to ice content, with parameters of best-fit curve models offering simple empirical predictors of saturation. A critical ice content of 1% to 3%, wherein a significant increase in penetration resistance occurs, is identified as being fundamentally influenced by the filling of substantial pore space with grouting ice. A decrease in viscoelastic behavior of high ice content samples at cryogenic temperatures is noted, and inhibition of relaxation mechanisms due to activation-energy-based temperature effects is also demonstrated in dry, ice-free simulant. Additional research across the spectrum of ice saturations, temperatures, and pressure environments likely to be found in extraterrestrial environments is suggested to improve upon these results, in particular using cryogenic systems even more specialized to reduce thermal issues and increase load capacities and apparatus stiffness. Such additional information will serve to advance the potential use of these results and this technology in future exploratory missions.

Bi-directional reflectance and polarization measurements of pulse-laser irradiated airless body analog materials

Space weathering (SW) processes including solar wind irradiation and micrometeorite bombardment produce nano-phase iron (npFe) and amorphous layers that redden and darken the visible and near-infrared (VNIR) reflectance spectra of the surface of airless bodies. To understand how SW may affect the directional reflectance and polarization properties of regolith layers, we carried out pulsed laser irradiation experiments to simulate micrometeorite bombardment process on olivine (OL), orthopyroxene (OPX), anorthosite (AN), ilmenite (ILM), and JSC-1A Lunar Regolith Simulant (LRS). All samples have been equalized with a size distribution of (<45 μm) and the unsieved LRS with (<1 mm) was also used. Depending on each sample's difficulty level of weathering, 2 to 8 irradiations with single pulse energy of 50 mJ were used in the irradiations. We measured the spectral reflectance from 0.5 to 25 μm, bi-directional reflectance distribution function (BRDF) and polarization phase curves at 0.633 μm of the samples before and after irradiations. Scanning electron microscopic images show that the irradiated samples become rougher with produced melts and agglutinates. The VNIR reflectance spectra of all irradiated samples show prominent darkening and reddening, except for the unsieved LSR sample which shows spectral blueing. Compared to that of the original samples, the BRDF of irradiated OL and OPX have both enhanced back- and forward-scattering components, while the other 4 samples have enhanced backscattering but nearly unchanged (AN, ILM, JSC-1A (<45 μm)) or decreased (JSC-1A (<1 mm)) forward scattering. In general, the irradiated samples have larger positive polarization values DOPmax as compared to the original samples, consistent with the Umov law prediction. Within measurement uncertainties, the irradiated samples did not show systematic changes in the minimum polarization value DOPmin and the polarization inversion angle αinv. Using OL as an example, numerical radiative transfer computations verified that, the BRDF of olivine grains with npFe distributed uniformly inside the grains or coated with npFe have enhanced back- and forward scattering components as compared with that of the original grains, consistent with measurement results. A 5-parameter Hapke photometric model inversion has shown that all sample grains except OPX have become more backscattering (with smaller asymmetry parameters) upon the strongest irradiation as compared with the original ones. These results indicate that the directional reflectance properties of space weathered regolith grains of airless bodies may be more backscattering than that of fresh materials.

Upwards migration phenomenon on molten lunar regolith: New challenges and prospects for ISRU

As part of our research on the feasibility of producing commodities from lunar regolith by thermal-driven processes with minimal terrestrial precursors we need to characterize, reproduce, and understand thermophysical properties of the molten regolith still unforeseen under the lunar vacuum conditions at a scalable sample size. Two unanticipated phenomena, apparently caused by lunar melt’s surface tension under vacuum, have been revealed in our research work, vacuum void formation and upwards migration. In this paper we present our findings and thinkable explanation on the upwards migration phenomenon experimentally observed and consistently replicated as JSC-1A lunar regolith simulant melted at high vacuum. Upwards migration of molten lunar regolith will make future lunar ISRU’s melting processes both challenging as molten bulk material would migrate upwards along the container’s walls, and also promising on new opportunities for alternative ISRU’s sustainable processes as regolith’s upwards migration takes place in uniformed thin-film pattern. Among the potential ISRU’s processes that might use controlled thermal thin-film-based migration without the necessity of terrestrial precursors are production of feedstock for 3D printing, fractional separation of regolith’s component’s (O2, metals, and alloys) via pyrolysis, film coating, purification of valuables solid crystals including silicon, and fabrication of key elements for microfluidic, and MEMS devices. Thermal upwards migration phenomenon on JSC-1A’s melt is formulated and explained by the authors as due to thermal Marangoni effect (also known as thermo-capillarity) in which temperature gradients within the melt’s bulk and along the crucible’s wall yield the surface tension large enough to supersede the gravitational force and yield the experimentally observed upwards thin-film migration. As far as the authors know, upwards thermal migration of molten JSC-1A (or other lunar simulant regolith) under vacuum has not been reported in the literature. A thermal mathematical model accounting for thermal Marangoni effect on molten JSC-1A agrees with what experimentally was observed, the formation of the meniscus on the melt-wall surface interface along with an incipient upwards migration in thin-film pattern along the crucible wall that, according to the model, experiences large temperature gradient, an important factor to trigger the thermal Marangoni effect along with the fact that surface tension of the molten lunar regolith material is temperature dependent.

Aluminum–nickel combustion for joining lunar regolith ceramic tiles

Combustion-based methods are attractive for space manufacturing because the use of chemical energy stored in reactants dramatically decreases the required external energy input. Recently, a sintering technique has been developed for converting lunar/Martian regolith into ceramic tiles, but it is unclear how to build a reliable launch/landing pad from these tiles with small amounts of energy and materials. Here we explored the feasibility of joining the regolith tiles using self-propagating high-temperature reactions between two metal powders. Combustion of an aluminum/nickel mixture placed in a gap between two tiles, made of JSC-1A lunar regolith simulant, was studied in an argon environment at 1 kPa pressure. Stable propagation of the combustion front was observed over the tested range of distances between the tiles, 2–8 mm. The front velocity increases with increasing the distance between the tiles. Joining of the tiles was achieved in several experiments and improvement with increasing the tile thickness was observed. Thermophysical properties of the tiles, the reactive mixture, and the reaction product were determined using differential scanning calorimetry and laser flash analysis. A model for steady propagation of the combustion wave over a condensed substance layer placed between two inert media was applied for analysis of the investigated system. Testing the model has resulted in reasonable agreement between the experimental and modeling dependencies. Both experimental and modeling results indicate a narrow quenching distance in the investigated system, which implies that a small amount of the reactive mixture would be required for sintering regolith tiles on the Moon.

Sintering of micro-trusses created by extrusion-3D-printing of lunar regolith inks

The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ∼500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of the sintered lunar regolith micro-trusses are investigated. The air-sintered micro-trusses have higher relative densities, linear shrinkages, and peak compressive strengths, due to the improved sintering of the struts within the micro-trusses achieved by a liquid or glassy phase. Whereas the hydrogen-sintered micro-trusses show no liquid-phase sintering or glassy phase, they contain metallic iron 0.1–2 μm particles from the reduction of ilmenite, which allows them to be lifted with magnets.

Laboratory experiments to investigate sublimation rates of water ice in nighttime lunar regolith

The existence of water ice on the lunar surface has been a long-standing topic with implications for both lunar science and in-situ resource utilization (ISRU). Cold traps on the lunar surface may have conditions necessary to retain water ice, but no laboratory experiments have been conducted to verify modeling results. We present an experiment testing the ability to thermally control bulk samples of lunar regolith simulant mixed with water ice under vacuum in an effort to constrain sublimation rates. The simulant used was JSC-1A lunar regolith simulant developed by NASA's Johnson Space Center. Samples with varying ratios of water ice and JSC-1A regolith simulant, totally about 1kg, were placed under vacuum and cooled to 100K to simulate conditions in lunar cold traps. The resulting sublimation of water ice over an approximately five-day period was measured by comparing the mass of the samples before and after the experimental run. Our results indicate that water ice in lunar cold traps is stable on timescales comparable to the lunar night, and should continue to be studied as possible resources for future utilization. This experiment also gauges the efficacy of the synthetic lunar atmosphere mission (SLAM) as a low-cost water resupply mission to lunar outposts.

Characterization of the permittivity of controlled porous water ice-dust mixtures to support the radar exploration of icy bodies

The internal properties of porous and icy bodies in the Solar System can be investigated by ground-penetrating radars (GPRs), like the CONSERT instrument onboard the Rosetta spacecraft which has sounded the interior of the nucleus of comet 67P/C-G. Accurate constraints on the permittivity of icy media are needed for the interpretation of the data. We report novel permittivity measurements performed on water ice samples and icy mixtures with porosities in the 31–91% range. The measurements have been performed between 50 MHz and 2 GHz with a coaxial cell on a total of 38 samples with a good reproducibility. We used controlled procedures to produce fine-grained and coarse-grained ice samples with a mean diameter of 4.5 μm and 67 μm, respectively, and to prepare icy mixtures. The JSC-1A Lunar regolith simulant was used as the dust component in the mixtures. The results are focused on the real part e′ of the permittivity, which constrains the phase velocity of the radio waves in low-loss media. The values of e′ show a non-dispersive behavior and are within the range of 1.1 to 2.7. They decrease with the increasing porosity Φ according to E(1 − Φ), with E equal to about 3.13 for pure water ice, and in the 3.8–7.5 range for ice-dust mixtures with a dust-to-ice volumetric ratio in the 0.1–2.8 range, respectively. These measurements are also relevant for radiometers operating in the millimeter-submillimeter domains, as suggested by the non-dispersive behavior of the mixtures and of the pure components.

3D printing with moondust

Purpose The purpose of this paper is to investigate the effect of the main process parameters of laser melting (LM) type additive manufacturing (AM) on multi-layered structures manufactured from JSC-1A Lunar regolith (Moondust) simulant powder. Design/methodology/approach Laser diffraction technology was used to analyse and confirm the simulant powder material particle sizes and distribution. Geometrical shapes were then manufactured on a Realizer SLM™ 100 using the simulant powder. The laser-processed samples were analysed via scanning electron microscopy to evaluate surface and internal morphologies, X-ray fluorescence spectroscopy to analyse the chemical composition after processing, and the samples were mechanically investigated via Vickers micro-hardness testing. Findings A combination of process parameters resulting in an energy density value of 1.011 J/mm2 allowed the successful production of components directly from Lunar regolith simulant. An internal relative porosity of 40.8 per cent, material hardness of 670 ± 11 HV and a dimensional accuracy of 99.8 per cent were observed in the fabricated samples. Originality/value This research paper is investigating the novel application of a powder bed fusion AM process category as a potential on-site manufacturing approach for manufacturing structures/components out of Lunar regolith (Moondust). It was shown that this AM process category has the capability to directly manufacture multi-layered parts out of Lunar regolith, which has potential applicability to future moon colonization.

Thermite reactions with oxides of iron and silicon during combustion of magnesium with lunar and Martian regolith simulants

It has been shown recently that mixtures of JSC-1A lunar regolith simulant with magnesium are combustible. Thermite-type reactions in these mixtures could be used for in situ production of construction materials on the Moon. Because of complex composition of lunar regolith, however, the mechanisms of these reactions are not well understood. Also, for Mars mission applications, it is important to explore the possibility of using Martian regolith in such mixtures. In the present paper, combustion of two Martian regolith simulants (JSC-Mars-1A and Mojave Mars) with magnesium is studied using thermodynamic calculations and combustion experiments. To understand the reaction mechanisms in these mixtures as well as in the mixtures of JSC-1A lunar regolith simulant with magnesium, thermoanalytical experiments are also conducted. It has been shown that the Martian regolith simulants form combustible mixtures with magnesium. The measured combustion temperatures and identified product compositions are in reasonable agreement with thermodynamic predictions. The mixtures of JSC-Mars-1A with magnesium at 20–30wt% Mg exhibit higher temperatures and burn more vigorously than mixtures based on Mojave Mars, which is explained by the higher content of iron oxide in JSC-Mars-1A. For Mojave Mars, combustion is accompanied by oscillations in the front motion and by the formation of a layered structure of the product. This effect is more significant at lower concentrations of Mg. Thermoanalytical studies have shown that iron oxide plays a dominant role in the combustion of JSC-Mars-1A simulant with magnesium. However, Mg/SiO2 mixture ignites at a temperature lower by approximately 100°C than for Mg/Fe2O3. For Mojave Mars material and JSC-1A lunar regolith simulant, which include more silica and less iron oxide, silica exhibits a significant effect on the combustion, promoting reactions at lower temperatures.

Design of a Lunar Solar Wind Volatiles Extraction System

Two devices are being developed as part of a project to demonstrate the extraction of helium-3 and other volatiles from lunar regolith. The first is an implantation system to embed helium ions into JSC-1A lunar regolith simulant and the second is a counter flow heat pipe heat exchanger for the subsequent diffusion of the helium out of the regolith. This will simulate the previously proposed acquisition of helium-3 from the Moon for use in nuclear fusion reactors on Earth. Preliminary designs of both of these systems are discussed.1

Extraction of Volatiles from Lunar Regolith Using Solar Power

Recent lunar spacecraft missions have confirmed the presence of water and miscellaneous volatiles within the craters of the moon’s south pole. If harvested, these resources have the potential to provide incredible cost savings to the space program. Challenges include extreme conditions and lack of solar power in the permanently shadowed areas. The proposed concept involves the transfer of beamed power from solar concentrators to extract the volatiles from the regolith within the shadowed craters of the moon. The present paper focuses on the analysis of heat transfer from the regolith surface, irradiated by the light beam. This analysis is needed for the determination of solar power required for the extraction of volatiles. To demonstrate the feasibility of the proposed concept and validate the heat transfer analysis, experiments involving laser irradiation of JSC-1A lunar regolith simulant mixed with water have also been conducted.

Measurement of Dust Charging on a Lunar Regolith Simulant Surface

This paper presents experimental research to determine the charge of individual dust grains on a lunar regolith simulant surface immersed in plasma. The results show that, at similar surface charging potentials, both the charge and the charge-to-mass ratio of dust grains on a JSC-1A lunar regolith simulant surface is about two orders of magnitude smaller than that of a single, isolated dust particle.

Towards better combustion of lunar regolith with magnesium

It has been shown recently that lunar regolith forms combustible, thermite-type mixtures with magnesium. Combustion of these mixtures could be used for the production of construction materials on the Moon. The present paper focuses on decreasing magnesium content in mixtures based on JSC-1A lunar regolith simulant and increasing the density and strength of the combustion products of these mixtures. Combustion of JSC-1A/Mg mixture pellets was studied in argon gas and in silica powder. Preheating to 100°C decreased the minimum concentration of magnesium, required for combustion, from 10wt.% to 8wt.%. Submerging the pellets into silica increased the product strength. SHS compaction experiments were conducted, which involved quasi-isostatic pressing of the products immediately after the end of the combustion process. This resulted in a significant increase in the product density. The compressive strength exceeded 10MPa, i.e., was higher than that of common bricks (5MPa).

Combustion wave propagation in mixtures of JSC-1A lunar regolith simulant with magnesium

Combustion of lunar regolith mixed with energetic additives is a potential method for production of construction materials in future moon missions. Recently, self-sustained combustion in the mixtures of JSC-1A lunar regolith and magnesium has been demonstrated. However, the concentration of magnesium in those mixtures was as high as 26wt%. Note that magnesium must be either transported from Earth or recovered from lunar minerals or used structures. The present paper focuses on the minimization of magnesium content in JSC-1A/Mg mixtures. The mixtures were compacted into pellets and ignited in argon environment. Initial attempts to decrease magnesium concentration resulted in the observations of a spinning combustion wave at 23wt% Mg. The observed spin combustion involved periodical motion of two counterpropagating hot spots along a helical path on the sample surface. These observations, including features such as formation of a faster hot spot after collision of the counterpropagating spots, confirm theoretical predictions for spin combustion in solid–solid mixtures. High-energy mechanical milling of JSC-1A in a planetary ball mill significantly increased its reactivity and improved combustion of its mixtures with magnesium. Mixtures of the obtained powder (the median diameter of about 3μm) with 26wt% Mg exhibit easy ignition and vigorous combustion. The minimum concentration of magnesium required for self-sustained propagation of a planar combustion front is as low as 13wt%.

Combustible Mixtures of Lunar Regolith with Metals: Thermodynamic Analysis and Combustion Experiments

Construction materials could be produced in situ on the surface of the moon or Mars by combustion of regolith mixed with metals such as aluminum and magnesium. In the present paper, the adiabatic flame temperature and combustion products were calculated for the mixtures of JSC-1A lunar regolith simulant with aluminum and magnesium, aswell aswith a titanium/boron pair. It was shown that at the additive concentrations of 20–30wt%, the reaction between titanium and boron provides a lower adiabatic flame temperature of themixture as compared with the thermite-type reaction between regolith and aluminum or magnesium. Also, magnesium exhibits higher temperatures as compared with aluminum. Themaximum temperatures for aluminum andmagnesium are reached at 23 and 26wt%, respectively. Combustion ofmagnesium/JSC-1Amixture pellets was studied experimentally in an argon environment. To facilitate ignition and achieve stable combustion, the original JSC-1A powder was ground in aballmill. It was shown that, with increasing themilling time of JSC-1A, the combustion front velocity ofMg/JSC-1A mixture increases. A decrease in argon pressure from 90 to 10 kPa does not influence the front velocity.

Direct Shear Tests on JSC-1A Lunar Regolith Simulant

A series of direct shear tests were conducted on the JSC-1A lunar regolith simulant in a 101.6-mm- (4-in.-) diameter container. The direct shear test provides a unique mode of failure that aids the development of excavation tools for the Moon. Relative density and normal load were varied to study the strength behavior of such granular material at peak and critical state conditions. The values of the internal friction angle ranged from 30 to 70°. A relationship between the internal friction angle of the direct shear and the published triaxial compression test results is presented. Additionally, the measured dilatancy angle is related to the difference in peak and critical state stress friction angles.