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NASA NTRS2011

Radiation Shielding of Lunar Regolith/Polyethylene Composites and Lunar Regolith/Water Mixtures

Space radiation is a complex mixed field of ionizing radiation that can pose hazardous risks to sophisticated electronics and humans. Mission planning for lunar exploration and long duration habitat construction will face tremendous challenges of shielding against various types of space radiation in an attempt to minimize the detrimental effects it may have on materials, electronics, and humans. In late 2009, the Lunar Crater Observation and Sensing Satellite (LCROSS) discovered that water content in lunar regolith found in certain areas on the moon can be up to 5.6 +/-2.8 weight percent (wt%) [A. Colaprete, et. al., Science, Vol. 330, 463 (2010). ]. In this work, shielding studies were performed utilizing ultra high molecular weight polyethylene (UHMWPE) and aluminum, both being standard space shielding materials, simulated lunar regolith/ polyethylene composites, and simulated lunar regolith mixed with UHMWPE particles and water. Based on the LCROSS findings, radiation shielding experiments were conducted to test for shielding efficiency of regolith/UHMWPE/water mixtures with various percentages of water to compare relative shielding characteristics of these materials. One set of radiation studies were performed using the proton synchrotron at the Loma Linda Medical University where high energy protons similar to those found on the surface of the moon can be generated. A similar experimental protocol was also used at a high energy spalation neutron source at Los Alamos Neutron Science Center (LANSCE). These experiments studied the shielding efficiency against secondary neutrons, another major component of space radiation field. In both the proton and neutron studies, shielding efficiency was determined by utilizing a tissue equivalent proportional counter (TEPC) behind various thicknesses of shielding composite panels or mixture materials. Preliminary results from these studies indicated that adding 2 wt% water to regolith particles could increase shielding of the regolith materials by about 6%. The findings may be utilized to extend the possibilities of potential candidate materials for lunar habitat structures, will potentially impact the design criteria of future human bases on the moon, and provide some guidelines for future space mission planning with respect to radiation exposure and risks posed on astronauts.

Johnson, Quincy F.↗

NASA NTRSDate not supplied

Design and Testing of a Device for Homogeneous Moon Dust Deposition on Test Articles/Systems

During this decade, NASA is charged to return humans to the surface of the Moon. One of the most challenging aspects to operating on the lunar surface is the regolith present, which is pervasive and damaging. To support systems design and validation for this environment, the handling and application of lunar simulants onto test articles or systems becomes important, albeit difficult. A device to apply the same amount of dust uniformly was developed in a previous study (Hollingsworth et al., 2006) but was only utilized with Mars dust simulant during that previous project. The current work provides evaluation of this device with multiple lunar simulants, each representing different composition as found at various locations on the Moon’s surface. Enhancements to the design and operation of the dust distributor are also described, along with a new digital imaging technique to calculate the percent surface coverage of the dust after deposition. The results support the use of the distributor and improved techniques to provide a uniform coating of dust on test articles and systems.

lunar↗

NASA NTRSDate not supplied

Design and Testing of a Device for Moon Dust Deposition on Test Articles/Systems

During this decade, NASA is charged to return humans to the surface of the Moon. One of the most challenging aspects to operating on the lunar surface is the regolith present, which is pervasive and damaging. To support systems design and validation for this environment, the handling and application of lunar simulants onto test articles or systems becomes important, albeit difficult. A device to apply the same amount of dust uniformly was developed in a previous study but was only utilized with Mars dust simulant during that previous project. The current work provides evaluation of this device with multiple lunar simulants, each representing different composition as found at various locations on the Moon’s surface. Enhancements to the design and operation of the dust distributor are also described, along with a new digital imaging technique to calculate the percent surface coverage of the dust after deposition. The results support the use of the distributor and improved techniques to provide a uniform coating of dust on test articles and systems.

Kathryn M Hurlbert↗

NASA NTRSDate not supplied

NASA's Ground Test Unit (GTU) Lunar Terrain Vehicle (LTV) Conceptual Hand Controllers Studies

Over that past year, the National Aeronautics and Space Administration (NASA) has been preparing and developing a set of standardized testing protocols for the commercial LTV vendor selection. Two studies have been conducted on two possible hand controller concepts specifically designed for the operation of NASA’s Ground Test Unit (GTU) Lunar Terrain Vehicle (LTV) that can be applied to the heretofore unknown designs developed by future LTV vendors. The objective for the two studies were to determine which hand controller enable acceptable operation of the LTV in a simulated lunar traverse. In the first evaluation a total of nine subjects in shirtsleeves with ungloved hands performed two simulated lunar driving courses in an engineering simulator with each hand controller. Controller concept one was the T-handle fashioned after the Apollo Lunar Roving Vehicle’s (LRV) T-Handle controller. The rational for using this design is it’s a proven design while in a pressurized suit. However, the LTV does have a driving mode the LRV did not consider. The mode of crabbing or strafing the vehicle at different angles; thus, the idea of a dual T-Handle controllers to accommodate this function without using a switch or display was introduced. The second concept controller is a new innovative controller call the Tri-Rotor [NASA patent review MSC-27385-1]. Inspired by Formula One race steering, the Tri-Rotor was designed to take advantage of the restricted movement and dexterity of a pressurized space suit. During testing, all subjects were able to successfully navigate through two test courses of varying lengths and complexity. Results indicated the dual Thandle had minimal recommendations for improvement while the Tri-Rotor had more extensive ones. It must be noted, the Tri-Rotor is a first-generation prototype and has some known mechanical concerns; thus, recommendations from this study will be incorporated into the second generation.

Human Factors↗

NASA NTRS2011

Downhole Elemental Analysis with LIBS

In this paper we discuss a novel instrument, currently under development at Honeybee Robotics with SBIR funding from NASA. The device is designed to characterize elemental composition as a function of depth in non-terrestrial geological formations. The instrument consists of a miniaturized laser-induced breakdown spectrometer (LIBS) analyzer integrated in a 2" diameter drill string. While the drill provides subsurface access, the LIBS analyzer provides information on the elemental composition of the borehole wall. This instrument has a variety of space applications ranging from exploration of the Moon for which it was originally designed, to Mars, as well as a variety of terrestrial applications. Subsurface analysis is usually performed by sample acquisition through a drill or excavator, followed by sample preparation and subsequent sample presentation to an instrument or suite of instruments. An alternative approach consisting in bringing a miniaturized version of the instrument to the sample has many advantages over the traditional methodology, as it allows faster response, reduced probability of cross-contamination and a simplification in the sampling mechanisms. LIBS functions by focusing a high energy laser on a material inducing a plasma consisting of a small fraction of the material under analysis. Optical emission from the plasma, analyzed by a spectrometer, can be used to determine elemental composition. A triangulation sensor located in the sensor head determines the distance of the sensor from the borehole wall. An actuator modifies the position of the sensor accordingly, in order to compensate for changes due to the profile of the borehole walls. This is necessary because LIBS measurements are negatively affected by changes in the relative position of the focus of the laser with respect to the position of the sample (commonly referred to as the "lens to sample distance"). Profiling the borehole is done by adjusting the position of the sensor with a vertical stage; a second actuator at the top of the downhole probe allows radial scanning of the borehole. Analysis of iron and titanium in lunar simulant with LIBS was performed in air using the method of standard addition. The results for lunar simulant NU-LHT-2M show a value for the concentration of iron ranging between 2.29% and 3.05% depending on the atomic line selected. The accepted value for the sample analyzed is 2.83%, showing the capability for the system in development to provide qualitative and semi-quantitative analysis in real-time.

Moreschini, Paolo↗

NASA NTRSDate not supplied

Grain Shape Characterization as an Enabling Capability for Lunar Surface Technologies

Lunar regolith has unique physical and geotechnical properties compared with familiar granular materials on Earth, and most lunar simulants as well. Specifically, the cohesion, angle of repose, and compressibility are much higher, and flowability is much lower for lunar regolith than otherwise similar terrestrial-derived materials[1,2]. There is confusion in the literature about the relative importance of vacuum, gravity, and inherent grain characteristics in driving these differences. Here we emphasize the importance of characterizing grain types and shapes for designing and test-ing lunar surface technologies, including for rover mobility, material handling, soil sampling, and heat transfer analyses. We demonstrate laboratory capabilities and preliminary studies, and outline further work to better characterize and simulate lunar grains to reduce risks for surface activities

K. M. Cannon↗

NASA NTRSDate not supplied

Development of New Lunar Highland Regolith Simulant, NUW-LHT-5M

Introduction: NASA has a need for large quantities of lunar simulants that closely match future manned lunar missions at landing sites near the Lunar South Pole. The current simulant was designed to approximate NU-LHT-2M, and -4M, except using natural minerals and a fully synthetic, non-basaltic, high calcium glass. Washington Mills in Niagara Falls, NY was contracted to produce this new simulant due to their electric arc furnace (EAF) fusion technology and capabilities for crushing and sizing ceramics. The primary objectives of this work were: (1) to create a commercially produced simulant that contains a high fidelity, high calcium (An90+), low Mg/Fe glass without basaltic constituents; (2) to create a simulant that uses existing, terrestrially mined, and readily available minerals blended with a synthetic glass, and (3) accomplish objectives (1) and (2) using conventional processing methods capable of production levels that can meet substantial current and future demands of NASA projects. Another consideration was that highland simulants closest to meeting these requirements, NU-LHT-2M and -4M types, are out of production and largely out of stock. Design: The design chosen for development and production for this work is NU-LHT-2M, de-signed by Doug Stoeser and Douglas Rickman, which uses Stillwater anorthosite and norite rocks and synthetic glass. The composition targeted the average composition, glass content and particle size distribution of Apollo 16 samples [1]. The design utilizes two Stillwater minerals, anorthosite (37.7 wt.%), norite (17.6 wt.%), a commercially sourced olivine (4.7 wt.%), and a synthetic glass (40 wt.%). Processing: Stillwater rocks were hand collected and initially crushed by the USGS. Further crushing and milling was performed at Washing-ton Mills. For the glass, oxides were blended in the ap-propriate ratios, blended in a v-blender, and placed in a graphite lined, water cooled pot. The mixture was fused in Washington Mills’ pilot scale, 500 kW EAF. The molten glass was then poured into water and quenched to inhibit crystallization. Several pour/quench cycles were required to produce the total quantity of glass needed. Anorthosite, norite and olivine were milled together to the target particle size in a ball mill. The glass was ball milled separately. The complete simulant was produced by blending the milled materials. Particle size distribution, phase and chemical analyses of the materials was were per-formed at Washington Mills. Results: The glass composition was found to match the Apollo 16 oxide content average [1] quite well, with the exception of SiO2 and Fe2O3. The deviation of SiO2 and Fe2O3 from batched content was believed to be due to limitations inherent in the use of the arc furnace technique for these types of materials. A particle size distribution of the full simulant formulation closely matching the average for the Apollo 16 samples was also achieved. Fig. 1 shows the morphology of the final simulant particles. The size distribution is compared to the target in Fig. 2. Conclusions: A new lunar highlands type simulant containing a high-quality synthetic glass, closely matching an average composition of the Apollo 16 regolith was produced. Processing utilized easily scalable mineral and glass making methods.

simulant↗

NASA NTRSDate not supplied

Autonomous Lunar PNT Simulator (ALPS)

In this paper we present a simulation tool that has been used to develop an architecture for a low-cost Position, Navigation and Time (PNT) system to provide PNT services on and around the Moon using non-dedicated low-cost orbital and ground assets. The simulation tool has been developed to be flexible and is capable of modeling and analyzing the many different capabilities and configurations that the non-dedicated assets could support. The tool models the creation of an ad hoc swarm, the localization of this swarm and the subsequent provision of PNT services from this swarm. We present results from several studies of select configurations chosen to reflect existing and future real-world needs and capabilities. Over the next few decades there is expected to be a substantial increase in Lunar missions supporting and inspired by NASA’s Artemis Program. It is expected that a large fraction of these missions will be low cost, utilizing rideshares and CubeSats, just as has seen in Earth orbit over the past decade. Many of these missions will need navigation capabilities but may be unable to support the large power, mass and weight that a weak GNSS or DSN based navigation solution would entail. As Lunar PNT service demand is not likely to be needed over the entire lunar surface 24/7, the creation of a dedicated Lunar GNSS constellation cannot be justified. Hence, our proposed architecture envisions utilizing existing Lunar science and exploration assets to create ad hoc and on demand Lunar PNT swarms capable of providing PNT services to low cost missions. The simulation reflects the two distinct parts of the architecture: the creation of a Lunar PNT swarm using non-dedicated existing assets, and the quantitative modeling of the quality of the PNT services that this swarm provides. To support the former, the simulation supports various swarm localization techniques, including centralized and distributed EKFs both of which support pluggable dynamics models. In modeling the PNT service performance the simulation adopts standard techniques from the GNSS community, including providing degree of precision (DOP) estimates for theoretical end users. Crucially, all asset capabilities, including clock accuracy, independent location self-knowledge and timing measurement precision can be set independently for each asset, reflecting the key concept of utilizing non-dedicated assets. The simulation is predominantly implemented in MATLAB, with GMAT being used for the propagation of orbital assets. The paper will present results from the simulation reflecting the tool’s flexibility and focusing on scenarios that match real-world proposed missions, including scenarios designed to provide PNT support to lunar surface missions similar to NASA Ames' forthcoming VIPER mission. The performance of centralized and decentralized swarm configuration and localization techniques will be compared. Finally, performance of the PNT service provided by an autonomous Lunar PNT swarm will be compared to existing radiometric and weak GNSS methods.

Kelley Elizabeth Hashemi↗

NASA NTRS1992

Strength and fracture of glass in the lunar environment

Due to the lack of water on the moon, the effects of hydrolytic depolymerization - stress corrosion cracking - will be nonexistent in glasses produced and used on the moon. This would seem to make lunar glass very attractive for use in a wide variety of space engineering applications. We have applied the equation that describes stress corrosion cracking to lunar glass to show that, indeed, decreasing water vapor pressure results in an increase in strength. Experimental results on simulated lunar glass confirm this. The stress corrosion equation predicts an extremely high strength for glasses produced on the moon. This equation, however, cannot be applied to glasses under anhydrous conditions. In an environment completely devoid of water, the strength of glass will be determined by the fracture of the glass at the tip of a flaw, without the corrosive effects of water. Under this condition, in accordance with fracture theory, the strength of the glass will primarily be a function of the flaw size. Our experimental results show that the presence of surface flaws is more detrimental to the strength of simulated lunar glass than the effect of hydrolytic depolymerization.

Allen, Daniel D.↗

NASA NTRS1987

Soil experiment

An experimental procedure was devised to investigate the effects of the lunar environment on the physical properties of simulated lunar soil. The test equipment and materials used consisted of a vacuum chamber, direct shear tester, static penetrometer, and fine grained basalt as the simulant. The vacuum chamber provides a medium for applying the environmental conditions to the soil experiment with the exception of gravity. The shear strength parameters are determined by the direct shear test. Strength parameters and the resistance of soil penetration by static loading will be investigated by the use of a static cone penetrometer. In order to conduct a soil experiment without going to the moon, a suitable lunar simulant must be selected. This simulant must resemble lunar soil in both composition and particle size. The soil that most resembles actual lunar soil is basalt. The soil parameters, as determined by the testing apparatus, will be used as design criteria for lunar soil engagement equipment.

Hutcheson, Linton↗

NASA NTRSDate not supplied

Development of New Lunar Highland Regolith Simulant, NUW-LHT-5M

simulant↗

NASA NTRS1973

Evidence for a ubiquitous, sub-microscopic 'magnetite-like' constituent in the lunar soils

Electron spin resonance (ESR) has been employed in a study of the ferromagnetic constituents of a wide variety of soils from six sampled regions of the moon as well as glasses made to simulate lunar compositions. A significant result has been that magnetite-like phases (magnetic iron spinel) precipitated in and on simulated lunar glasses as a result of sub-solidus oxidation yield room-temperature ESR spectra virtually identical with the line shape predicted for spherical, single domain particles of metallic Fe. It is shown that such magnetite-like phases can nevertheless be distinguished from metallic iron on the basis of the temperature dependence of the ESR intensity.

Griscom, D. L.↗

NASA NTRS1993

Experimental Determination of in Situ Utilization of Lunar Regolith for Thermal Energy Storage

A Lunar Thermal Energy from Regolith (LUTHER) experiment has been designed and fabricated at the NASA Lewis Research Center to determine the feasibility of using lunar soil as thermal energy storage media. The experimental apparatus includes an alumina ceramic canister (25.4 cm diameter by 45.7 cm length) which contains simulated lunar regolith, a heater (either radiative or conductive), 9 heat shields, a heat transfer cold jacket, and 19 type B platinum rhodium thermocouples. The simulated lunar regolith is a basalt, mined and processed by the University of Minnesota, that closely resembles the lunar basalt returned to earth by the Apollo missions. The experiment will test the effects of vacuum, particle size, and density on the thermophysical properties of the regolith. The properties include melt temperature (range), specific heat, thermal conductivity, and latent heat of storage. Two separate tests, using two different heaters, will be performed to study the effect of heating the system using radiative and conductive heat transfer. The physical characteristics of the melt pattern, material compatibility of the molten regolith, and the volatile gas emission will be investigated by heating a portion of the lunar regolith to its melting temperature (1435 K) in a 10(exp -4) pascal vacuum chamber, equipped with a gas spectrum analyzer. A finite differencing SINDA model was developed at NASA Lewis Research Center to predict the performance of the LUTHER experiment. The analytical results of the code will be compared with the experimental data generated by the LUTHER experiment. The code will predict the effects of vacuum, particle size, and density has on the heat transfer to the simulated regolith.

Richter, Scott W.↗

NASA NTRS2010

Preliminary Assessment of Seals for Dust Mitigation of Mechanical Components for Lunar Surface Systems

Component tests were conducted on spring-loaded Teflon seals to determine their performance in keeping lunar simulant out of mechanical component gearbox, motor, and bearing housings. Baseline tests were run in a dry-room without simulant for 10,000 cycles to determine wear effects of the seal against either anodized aluminum or stainless steel shafts. Repeat tests were conducted using lunar simulants JSC-1A and LHT-2M. Finally, tests were conducted with and without simulant in vacuum at ambient temperature. Preliminary results indicate minimal seal and shaft wear through 10,000 cycles, and more importantly, no simulant was observed to pass through the seal-shaft interface. Future endurance tests are planned at relevant NASA Lunar Surface System architecture shaft sizes and operating conditions.

Delgado, Irebert R.↗

NASA NTRS2010

Preliminary Assessment of Seals for Dust Mitigation of Mechanical Components for Lunar Surface Systems

Delgado, Irebert R.↗

NASA NTRS1982

Fractionation of mineral species by electrophoresis

The fractionation of fine-grained aggregates into their major components is a problem in many scientific areas including earth and planetary science. Electrophoresis, the transport of electrically charged particles, immersed in a suspension medium, by a direct current field (Bier, 1959), was employed in this study as a means of separating simulated lunar soil into its constituent minerals. In these tests, conducted in a static analytical cylindrical microelectrophoresis apparatus, samples of simulated lunar soil and samples of pure mineral constituents were placed in the chamber; the electrophoretic mobilities of the lunar soil and the individual mineral constituents were measured. In most of the suspension buffers employed separability was indicated, on the basis of differences in mobility, for all the constituent mineral species except ilmenite and pyroxene, which were not efficiently separable in any of the buffers. Although only a few suspension media were employed, the success of this initial study suggests that electrophoresis may be an important mineral fractionation option in fine-grained aggregate processing.

Dunning, J. D.↗

NASA NTRSDate not supplied

Immersive Technologies for Human-in-the-Loop Lunar Surface Simulations

NASA, the National Aeronautics and Space Administration, continually seeks innovative solutions to enhance its operations, particularly in the realms of testing, evaluation, and training for future missions. Immersive technologies, such as virtual, augmented, and mixed reality have proven to be powerful tools for realistic, interactive, and engaging environments. This paper explores how the Simulation and Graphics Branch at NASA’s Johnson Space Center (JSC) leverages immersive technology, modern commercial rendering engines, and physics-based systems simulations to develop human-in-the-loop systems for humanity’s return to the Moon through the Artemis program. When NASA returns to the Moon, astronauts will travel to the Moon’s South Pole where lighting conditions will cause a more complex operational environment. Human-in-the-loop testing plays a crucial role in NASA's mission planning, spacecraft and space systems development, and evaluation of operational scenarios. The development of immersive environments such as a lunar rover mockup at a video wall enables engineers and astronauts to simulate and experience mission scenarios, integrated spacecraft systems, and operational procedures in a relevant environment before deployment. By integrating realistic virtual environments, immersive technology allows for the visualization and interaction with virtual spacecraft models, mission landscapes, and complex operational tasks. This approach helps identify potential design flaws, operational challenges, and safety considerations. It also provides valuable insights for risk reduction and helps improve mission efficiency and effectiveness. With advanced motion tracking systems and custom virtual environments data can be gathered and evaluated to help NASA refine training protocols, develop specialized training procedures and optimize human-robotic interactions for future space missions. Furthermore, immersive technology offers opportunities for future training initiatives at NASA. The Virtual Reality Laboratory at JSC has pioneered training with Virtual Reality (VR) since the Hubble Space Telescope repair missions in the early 1990’s. Extended Reality (XR) simulations enable astronauts to rehearse complex spacewalks, spacecraft maneuvers, and extravehicular activities in a safe and controlled environment. By replicating the physical and cognitive challenges of space missions, immersive training experiences enhance astronauts' situational awareness, decision-making abilities, and adaptability to unexpected scenarios. Additionally, immersive technology facilitates collaborative training, allowing geographically dispersed crew and mission control personnel to engage in synchronized simulations, fostering teamwork and effective communication. The adoption of immersive technology in NASA's testing, evaluation, and future training programs has yielded significant benefits. By incorporating human-in-the-loop testing for studies involving Extra Vehicular Activities (EVA), surface mobility and landing systems, NASA can identify and mitigate risks, optimize operational procedures, and enhance mission success. Ultimately, immersive training experiences can empower astronauts to better navigate the complexities of space missions, ensuring their safety, productivity, and success in the dynamic and challenging environments they will experience at the Lunar South Pole.

Simulation Modeling Virtual Reality Immersive Tech↗

NASA NTRS2006

Lunar Metal Oxide Electrolysis with Oxygen and Photovoltaic Array Production Applications

This paper presents the results of a Marshall Space Flight Center funded effort to conduct an experimental demonstration of the processing of simulated lunar resources by the molten oxide electrolysis (MOE) process to produce oxygen and metal from lunar resources to support human exploration of space. Oxygen extracted from lunar materials can be used for life support and propellant, and silicon and metallic elements produced can be used for in situ fabrication of thin-film solar cells for power production. The Moon is rich in mineral resources, but it is almost devoid of chemical reducing agents, therefore, molten oxide electrolysis, MOE, is chosen for extraction, since the electron is the most practical reducing agent. MOE was also chosen for following reasons. First, electrolytic processing offers uncommon versatility in its insensitivity to feedstock composition. Secondly, oxide melts boast the twin key attributes of highest solubilizing capacity for regolith and lowest volatility of any candidate electrolytes. The former is critical in ensuring high productivity since cell current is limited by reactant solubility, while the latter simplifies cell design by obviating the need for a gas-tight reactor to contain evaporation losses as would be the case with a gas or liquid phase fluoride reagent operating at such high temperatures. In the experiments reported here, melts containing iron oxide were electrolyzed in a low temperature supporting oxide electrolyte (developed by D. Sadoway, MIT). The production of oxygen and reduced iron were observed. Electrolysis was also performed on the supporting electrolyte with JSC-1 Lunar Simulant. The cell current for the supporting electrolyte alone is negligible while the current for the electrolyte with JSC-1 shows significant current and a peak at about -0.6 V indicating reductive reaction in the simulant.

Curreri, P. A.↗