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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Regolith Volatile Recovery at Simulated Lunar Environments

Lunar Polar Volatiles: Permanently shadowed craters at the lunar poles contain water, 5 wt according to LCROSS. Interest in water for ISRU applications. Desire to ground truth water using surface prospecting e.g. Resource Prospector and RESOLVE. How to access subsurface water resources and accurately measure quantity. Excavation operations and exposure to lunar environment may affect the results. Volatile capture tests: A series a ground based dirty thermal vacuum tests are being conducted to better understand the subsurface sampling operations. Sample removal and transfer. Volatiles loss during sampling operations. Concept of operations, Instrumentation. This presentation is a progress report on volatiles capture results from these tests with lunar polar drill prototype hardware.

thermal vacuum tests↗
NASA NTRS1992

Dust protection for environmental control and life support systems in the lunar environment

Lunar dust is pervasive, and requirements for dust protection will affect both hardware design and operations planning for lunar surface systems. On Earth, mechanical problems caused by particulates include erosive and abrasive effects, clogging of mechanical equipment, and impairment of seals and bonds. In addition, dust tends to degrade the heat rejection properties of contaminated surfaces. All these effects have been observed on the lunar surface as well. This paper discusses the potential applicability of current dust protection methods to the problem of dust protection for the environmental control and life support (ECLS) systems of a lunar base, and highlights areas where development may be necessary. A review of dust problems experienced during the Apollo missions and of additional, ground-based experience with lunar dust provides a baseline for identifying operations and areas where dust may be expected to affect the ECLS systems. Current Earth-based methods of dust protection are identified and the impact of differences between the Earth and lunar environments on these methods is evaluated. Finally, integration of dust protection equipment with ECLS systems equipment is discussed.

Fuhs, Susan↗
NASA NTRSDate not supplied

Power Hibernation: Surviving the Extreme Cold Lunar Environment

Lunar Power Hibernation is an approach to dramatically extend capabilities and duration of low-cost robotic lunar missions by exploiting the common 18650 Li-Ion battery cell’s ability to tolerate and recover from extreme cold of the lunar night.

Space Power↗
NASA NTRSDate not supplied

The Behavior of High-Velocity Dust Generated by Lander Plumes in the Lunar Environment

Lunar lander plumes are known to accelerate fine dust to speeds exceeding 2 km/s, and the resultant ejecta may remain in lunar orbit for extended periods of time. Such ejecta could become hazardous to objects in lunar orbit as well as systems on the surface. In order to understand the impact on orbiting lunar infrastructure such as Gateway, as well as assets on the lunar surface, here we consider the dynamics of the resultant high-velocity plume ejecta. Initial conditions were set by the expected near-term lunar activity and the known cone of accelerated dust generated by previous lunar landings. The effects of regular 3-body gravitation, solar radiation pressure, and electric field are included in the model. It is found that although the majority of sub-μm dust is carried away by solar wind and electric fields, about ~10% of the dust between 1.7 km/s and 2.3 km/s reimpacts the surface, much of it near the landing site. The hazard posed by that debris is a function of lander mass and distance from the landing site. The Gateway, when orbiting in the nominal NRHO at the time of a landing, is not expected to be significantly affected by the dust. However, other spacecraft in less elliptic orbits may be at greater risk.

Ejecta↗
NASA NTRSDate not supplied

The Behavior of High-Velocity Dust Generated by Lander Plumes in the Lunar Environment

Lunar lander plumes have been determined to generate fine ejecta at speeds exceeding 2 km/s [1], and recent work [2] has shown that Escape Velocity Domain (EVD) ejecta may remain in orbit for extended periods of time. By confining this study to expected near-term lunar activity and the known cone of dust generated by lunar landings, the behavior of high-velocity dust is characterized in an effort to understand its impact on orbiting lunar infrastructure such as the Gateway as well as the footprint of reimpacting dust on the lunar surface. In addition to the regular 3-body gravitation effects, the effects of Solar Radiation Pressure and charge are both quantified and modeled.

Lunar↗
NASA NTRS1988

Design of a rotary stepped auger for a lunar environment

A lunar outpost will have need for deep drilling operations for both explorative and practical purposes. As in any drilling operation, the cuttings must be cleared from the hole. The hard vacuum of the lunar environment renders conventional flushing methods of cutting removal unfeasible, and requires a new system of removal. A rotary stepped auger (RSA) is a simple mechanical method of removing dry cuttings from a deep hole, and is ideally suited to the lunar environment. The RSA consists of a helical auger with stepped ramps which allow cuttings to slide up the helix, but will prevent them from sliding back down. The auger is driven in a pulsed manner by applying a periodic function of acceleration to the auger shaft. These pulses will compel the cuttings to slide up the auger's helix while the stepped ramps prevent the cuttings from backsliding while the auger accelerates. A mathematical model of the RSA was developed and experimentally evaluated. The math model produced a good baseline design, but the experimental model required some tuning to account for the approximations made in the math model. This design is suited for lunar drilling because it is mechanically simple, integral to the drill string, requires no fluids, is suited to the dry soil, and has relatively low weight and power requirements.

Dardet, Eduardo↗
NASA NTRS2008

Lunar Dust Charging by Secondary Electron Emission and its Complex Role in the Lunar Environment

The lunar surface is covered with a thick layer of micron/sub-micron size dust grains formed by billions of years of meteoritic impact. With virtually no atmosphere and exposed to the solar wind plasma and solar electromagnetic radiation, the lunar surface and the dust grains are electrostatically charged. The dominant charging processes include: photoelectric emissions (UV, X-rays), impact of solar wind electrons and ions, and secondary electron emissions (SEE) induced by energetic solar wind electrons. During the Apollo missions, the astronauts found the lunar dust to be extraordinarily high in its adhesive characteristics, sticking to the suits and the mechanical equipment. Electrostatically charged lunar dust is believed to be transported over long distances by the induced electric fields, as indicated by the observed dust streamers and the horizon glow [e.g., 1-3]. The hazardous effects of dust in the lunar environment are recognized to be one of the major issues that must be addressed in planning the forthcoming missions for robotic and human exploration of the Moon. Theoretical studies are being performed along with the development of analytical models and a variety of experimental investigations, to better understand the lunar dust phenomena. [e.g., 4-6]. The lunar dust is believed to be charged negatively on the lunar night-side by interaction With solar wind electrons. However, rigorous theoretical expressions for calculation of SEE yields and the sticking efficiencies of individual micron size dust grains are not yet available, and the information has to be obtained by experiment. On theoretical considerations, however, it is well recognized that SEE yields, similar to the photoelectric yields for small-size grains, would be totally different from the corresponding bulk values [e.g., 7-9]. Some theoretical models for charging of individual small spherical particles have been developed [e.g., 10], and some limited measurements on individual metallic dust grains at keV electron energies have been made [e.g., i 1]. In this paper, we present the first measurements of the secondary electron emission yields of individual micron/sub-micron size dust grains selected from sample returns of Apollo 11 and Apollo 17 missions.

Abbas, M. M.↗
NASA NTRS1960

The Lunar Environment

The NASA lunar exploration program has focused the attention of many scientific and technical groups on such questions as the relative value of lunar experiments, the advantages of manned versus unmanned exploration, and the proper time sequence for the steps to be taken in the exploration program. It is interesting to note that all the approaches to the problem require a definition of the lunar environment at an early stage in the program. The choice of scientific experiments and the design of the required instrumentation is based on our present knowledge of the Moon and on educated guesses as to what data may be obtained. The technical developments required to make possible both a lunar landing and continued operation of scientific equipment on the lunar surface also demand a definition of the lunar environment as a design condition.

Buwalda, Phyllis↗
NASA NTRSDate not supplied

Aerosol Physics for the Lunar Environment: Equations for Lunar Dust Control and Mitigation Technologies

Sticky and jagged dust was ubiquitous during the Apollo missions, causing soiling and abrasion problems with seals, coatings and equipment, in addition to eye irritation and breathing discomfort in the cabin. The Artemis Program of NASA aims to place astronauts on the lunar surface by 2024 and establish a sustainable presence in the following decade. Returning to the Moon requires controlling and mitigating the dust which will be inevitably brought inside the cabins. The state-of-the-science for effective collection of aerosols is based on dynamics of airborne particulate matter under terrestrial conditions. However, the governing physics does not apply to extra-vehicular activity in the hard-vacuum lunar condition. For example, the substantial difference in gravity will dictate particle transport both outside and inside the cabin. In this study, we revisited the aerosol physical phenomena that are assumed in the design of Earth-based aerosol instruments and extend the applicability to different scenarios in lunar missions. As shown, long-term lunar habitats, transfer vehicles to lunar orbital platforms, and low pressure cabin atmospheres have different aerosol dynamics. In all cases, the impact of dust control strategies using gravitational, electrical, and thermal techniques for various mitigation and monitoring hardware is explored. The guidelines provided through this study will show how terrestrial aerosol equipment can translate to lunar dust applications.

Nima Afshar-Mohajer↗
NASA NTRS2024

Electrical Properties of Lunar Environment Used for Predicting Lunar RF Propagation Characteristics

This contribution treats the lunar propagation environment as a three region medium: lunar exosphere, lunar regolith, and lunar bedrocks. Then it provides models for predicting the electromagnetic characteristics of each region. The electromagnetic characteristics could be electric characteristics represented by the complex relative permittivity, or magnetic characteristics represented by the complex relative permeability or both electric and magnetic characteristics. The lunar exosphere and the lunar bedrocks have only electric characteristics. The lunar regolith has both electric and magnetic characteristics. The complex relative permittivity models for lunar regolith are mapping of the corresponding models for Earth surface components reported in ITU-R P. 527-6. The complex relative permittivity prediction model of lunar exosphere is expressed in terms of a plasma frequency similar to the ordinary wave critical frequency in the corresponding model for the ionosphere. Based on this fascicle the following can be concluded for the frequency bands of 390 MHz and above: • The lunar exosphere can be treated as a free space, • The lunar regolith can be considered as non-magnetic, • The regolith complex relative permittivity has no temperature dependence, • The real part of the regolith complex relative permittivity depends only on regolith bulk density and it has no frequency dependence, and • The variation of regolith complex relative permittivity with regolith depth should be taken into consideration. Moreover, at frequencies of 2400 MHz and above, the lunar regolith can be treated as a uniform medium with complex relative permittivity equal to the corresponding complex relative permittivity at the regolith surface.

Electrical Permittivity↗
NASA NTRS2024

Lunar Dust Considerations for Vertical Solar Arrays Volume 1: Lunar Environment and Dust Interactions

Lunar dust can complicate nearly every aspect of operations on the lunar surface. Jagged surface asperities, electrostatic charge, chemical reactivity, and interactions resulting in high-velocity motion enable a myriad of potential interaction pathways for lunar dust to adversely affect any exposed surface. Optimization of solar array energy collection efficiency, which will be important for a sustained lunar presence, will require overcoming many challenges presented by lunar dust. In this work, the fundamental properties of lunar dust, natural aspects of the lunar environment that influence the properties of lunar dust, and lunar exploration activities that will contribute to problems associated with lunar dust exposure are discussed. Aspects of the lunar environment that could contribute to reducing the operational efficiency of vertical solar arrays, which will be required for the lunar south pole region, are also identified.

vertical solar array technology↗
NASA NTRS1970

Thermal control in a lunar environment

Apollo Lunar Surface Experiment Package (ALSEP) component configuration and deployment environment, describing passive thermal control system for data processing equipment

H E Collicott↗
NASA NTRS2008

Extreme Space Weather Events and Charging Hazard Assessments in Lunar Environments

The sunlit lunar surface charges to positive potentials with mean values of a few tens of volts where photoelectron currents dominate the charging process. In contrast, surfaces in darkness may charge to negative potentials on the order of a few hundred volts when the charging process is dominated by hot electron populations in the absence of solar photons. Recently, observations of electron beams measured by instruments on spacecraft in low lunar orbit have been interpreted as evidence for extreme lunar surface potentials exceeding a few kilovolts suggesting that lunar orbital and surface plasma environments may contain charging risks similar to geostationary orbit during extreme space weather conditions. Space system design for successful operation in a wide range of lunar environments will therefore require evaluation of charging hazards during extreme space weather conditions. We present results from a study of space weather environments conducted to obtained credible extreme charging environments for use in charging hazard assessments for lunar missions including extreme conditions encountered when the Moon is in the solar wind, the magnetosheath, and the Earth's magnetotail.

Minow, Joseph I.↗