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At least 289 records · Page 16
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NASA NTRSDate not supplied

Conversion of Environment Files from ORDEM 3 & MEM 3 to STENVI

To perform Micrometeoroid and Orbital Debris (MMOD) analyses, NASA describes the orbital debris particle environment using the ORDEM 3 tool and the micrometeoroid environment using the MEM 3 tool. Both output files that detail the flux of particles as a function of several parameters. European MMOD analyses use different tools to perform similar functions, including the Meteoroid And Space debris Terrestrial Environment Reference (MASTER) environment model, which outputs flux data in the Standard Environment Interface (STENVI) format. The NASA Johnson Space Center Hypervelocity Impact Technology Group was asked to create a converter to translate flux data from the output file formats used by ORDEM 3.x and MEM 3 into the STENVI file format. Validation was performed to ensure that the converter was reproducing the input data correctly. The Bumper 3 MMOD risk assessment tool has a capability for reading ORDEM 3.x, MEM 3, and STENVI environment file formats and was used to compare MMOD risk results generated using the converter’s output STENVI files to the risk results generated using the input ORDEM 3.x and MEM 3 igloo files. Specific point comparisons validated that the converter translated the environment data correctly, producing the intended output. However, realistic risk assessments showed that the bin methodology employed by Bumper for determining particle flux as a function of particle size when reading files in STENVI format produces much higher MMOD risk than the point-interpolation methodology used in Bumper risk assessments using ORDEM and MEM. Modifications to how Bumper 3 reads STENVI files during analyses are considered to improve Bumper’s ability to perform useful analyses with environment files in this format.

STENVI↗
NASA NTRS2023

Conversion of ORDEM 3.X & MEM 3 Into STENVI File Format

To perform Micrometeoroid and Orbital Debris (MMOD) analyses, NASA describes the orbital debris particle environment using the ORDEM 3 tool and the micrometeoroid environment using the MEM 3 tool. Both output files that detail the flux of particles as a function of several parameters. European MMOD analyses use different tools to perform similar functions, including the Meteoroid And Space debris Terrestrial Environment Reference (MASTER) environment model, which outputs flux data in the Standard Environment Interface (STENVI) format. The NASA Johnson Space Center Hypervelocity Impact Technology Group was asked to create a converter to translate flux data from the output file formats used by ORDEM 3.x and MEM 3 into the STENVI file format. Validation was performed to ensure that the converter was reproducing the input data correctly. The Bumper 3 MMOD risk assessment tool has a capability for reading ORDEM 3.x, MEM 3, and STENVI environment file formats and was used to compare MMOD risk results generated using the converter’s output STENVI files to the risk results generated using the input ORDEM 3.x and MEM 3 igloo files. Specific point comparisons validated that the converter translated the environment data correctly, producing the intended output. However, realistic risk assessments showed that the bin methodology employed by Bumper for determining particle flux as a function of particle size when reading files in STENVI format produces much higher MMOD risk than the point-interpolation methodology used in Bumper risk assessments using ORDEM and MEM. Modifications to how Bumper 3 reads STENVI files during analyses are considered to improve Bumper’s ability to perform useful analyses with environment files in this format.

STENVI↗
NASA NTRSDate not supplied

Understanding the Response of Common Spacecraft Shields to Hypervelocity Impacts of Meteorite and Other Terrestrial Analog Materials

Micrometeoroid and orbital debris (MMOD) populations can vary significantly in composition, density, and homogeneity. Hypervelocity testing campaigns intended to design and optimize MMOD shields for spacecraft are recognizing the need to investigate shield response from different types of impactors that span the range of densities observed in the MMOD population, such as nylon, Al, Al 2 O 3 , steel, and Cu. These tests, however, still pre-dominantly employ spherical and homogenous projectiles. Adding any compositional or mineralogical complexity to the impactor, such as what would be expected from a polymineralic micrometeoroid, for ex-ample, will be concomitant with a more complex shockwave structure in the projectile after it impacts the outer surface of any type of MMOD shield. The magnitude of these complexities will depend on how varied the mineralogy of the projectile is, but in the case of a metal-bearing chondrite, the disparate shock impendence between adjacent metal and silicate grains will potentially create localized areas of shock focusing (local increase in nominal shock pressure), or shock shadowing (local decrease in nominal shock pressure). The response of a MMOD shield is generally predicted using a ballistic limit equation – a semiempirical curve, derived from hypervelocity testing data, that denotes a particle diameter (for a given set of impact conditions such as projectile density and impact angle) when a shield will fail as a function of impact speed. These curves exhibit inflection points as a function of impact speed that represent when the projectile experiences sufficient pressure to fragment, melt, or vaporize. The introduction of shock focusing and shadowing in a heterogenous projectile will add uncertainty to the predicted pressures needed to go through each transition, leading to increased uncertainty in the expected performance of the MMOD shield. Therefore, it is necessary to explore the performance of MMOD shields in hypervelocity tests against more complex, natural projectile materials. To this end we have conducted a comparative test series to begin investigating the impact damage caused by meteoritic and terrestrial-analog projectiles, to that of spherical Al projectiles of similar mass.

Impact testing↗
NASA NTRS2024

Investigating Space Weathering of Ryugu Grains Using Electron Microscopy and X-Ray Computed Tomography

The effects of micrometeorite bombardment and solar wind ion irradiation – collectively known as space weathering – alter the microstructural, chemical, and spectral properties of airless surfaces. Characteristics of space weathering include vesiculated textures, amorphous grain rims (upper ~100 nm), and the production of Fe-bearing nanoparticles (npFe). The resulting modifications in the optical properties of the surface regolith include changes in spectral slope and overall reflectance of the surfaces as well as the attenuation of their characteristic absorption bands across VIS-NIR wavelengths. As the surface is continuously exposed to interplanetary space over time, the accrual of these features complicates the interpretation of remote sensing spectral data and the characterization of returned samples. Laboratory experiments that simulate solar wind irradiation and micrometeoroid impacts using carbonaceous analogs have revealed novel and complex microstructural and chemical changes, including the decrease in organic species concentrations and the reduction of Fe 3+ . In 2020, the Japan Aerospace Exploration Agency (JAXA)’s Hayabusa2 mission returned over 5 g of regolith particles from near- Earth C-type asteroid (162173) Ryugu – a unique opportunity to study space weathering on carbonaceous materials. Initial studies have established that the surface morphology and chemical signatures of space weathering in returned samples share characteristics with laser irradiation experiments simulating micrometeoroid bombardment, indicating that impacts are a significant space weathering mechanism operating on Ryugu. Here, we seek to improve our understanding of space weathering of carbonaceous asteroidal regolith grains by characterizing its effects directly on returned samples to determine the nature of space weathering on Ryugu. To do so, we performed coordinated analyses using electron beam techniques and X-ray computed tomography (XCT) to examine the effects of space weathering on grains returned from the surface of Ryugu by the Hayabusa2 mission.

L. E. Melendez↗
NASA NTRS2024

The Spectral Characteristics of Lunar Agglutinates: Visible-Near-Infrared Spectroscopy of Apollo Soil Separates

The lunar surface evolves over time due to space weathering, and the visible–near-infrared spectra of more mature (i.e., heavily weathered) soils are lower in reflectance and steeper in spectral slope (i.e., darker and redder) than their immature counterparts. These spectral changes have traditionally been attributed to the space-weathered rims of soil grains (and particularly nanophase iron therein). However, understudied thus far is the spectral role of agglutinates—the agglomerates of mineral and lithic fragments, nanophase iron, and glass that are formed by micrometeoroid impacts and are ubiquitous in mature lunar soils. We separated agglutinates and non-agglutinates from six lunar soils of varying maturity and composition, primarily from the 125–250 μm size fraction, and measured their visible–near-infrared reflectance spectra. For each soil, the agglutinate spectra are darker, redder, and have weaker absorption bands than the corresponding non-agglutinate and unsorted soil spectra. Moreover, greater soil maturity corresponds to darker agglutinate spectra with weaker absorption bands. These findings suggest that agglutinates (rather than solely the space-weathered rims) play an important role in both the darkening and reddening of mature soils—at least for the size fractions examined here. Comparisons with analog soils suggest that high nanophase iron abundance in agglutinates is likely responsible for their low reflectance and spectrally red slope. Additional studies of agglutinates are needed both to more comprehensively characterize their spectral properties (across size fractions and in mixing with non-agglutinates) and to assess the relative roles of agglutinates and rims in weathering-associated spectral changes. Plain Language Summary - In scientific study of the Moon, one key focus is surface processes: how do physical and chemical properties of the Moon’s surface change over time due to weathering (e.g., bombardment by micrometeoroids and by particles from the Sun)? Such investigations provide valuable insights into the Moon’s history (such as the ages of impact craters) that are often deduced from measurements of reflected light; as a soil is weathered it reflects light differently, which manifests visually as a progressive darkening of the soil. This phenomenon had primarily been attributed to weathering-associated development of rims on individual soil grains, but in this work we explored an alternative cause: soil particles known as agglutinates (misshapen, vesicular agglomerates of mineral fragments, iron, and glass that form due to weathering processes). We isolated agglutinates of six soil samples from the Moon and measured how they reflect light. We find that they reflect light in patterns reminiscent of how the Moon’s surface does when weathered. These findings suggest that agglutinates play a more important role than previously thought in determining the light-reflecting properties of the Moon’s surface, thus warranting greater and more nuanced consideration in future studies of how the Moon’s surface changes over time.

spectroscopy↗
NASA NTRSDate not supplied

Mirror Surface Contamination Specification Derived from Coronagraphy Scatter Error Budget Allocation

Near-Angle Scatter (NAS) of the host star’s light may limit the ability of a potential Habitable Worlds Observatory (HWO) to detect and characterize an Earth-like planet around a Sun-like star via coronagraphy. NAS from each optical surface before the coronagraph’s focal plane mask produces an E-field across the dark hole that is coherent. These E-fields sum and could be as large or larger than the coronagraph mask leakage E-field. This paper assumes an error budget allocation for scatter of 20 ppt. NAS E-fields contribute to the dark hole noise floor via both shot noise and heterodyne amplification of the wavefront instability. While previous papers have developed specifications for scatter from surface scatter, this paper develops specifications for scatter from surface contamination and micrometeoroid impacts. The development process utilizes an expression that predicts scatter throughput into the dark hole based on surface BRDF. Analysis does not include scatter from coating columnar structure, edges, contamination, micrometeoroid impacts, or polarization.

near angle scatter↗
NASA NTRS2024

Bumper Implementation of LMEEM

The Hypervelocity Impact Technology (HVIT) group at the NASA Johnson Space Center (JSC) maintains the Bumper 3 computer program (referred to as “Bumper”) to perform Micrometeoroid and Orbital Debris (MMOD) risk assessments for spacecraft. To perform its calculations, this program requires detailed mathematical models of the space environments and can include those models representing orbital debris, micrometeoroids, and lunar ejecta. The lunar ejecta environment is a projectile environment specific to the lunar surface. Due to the Moon’s lack of an atmosphere, meteoroids frequently strike the lunar surface. When this happens, the impact ejects material radially away from the impact point, which can pose a potential impact hazard to surface-based hardware. This lunar ejecta environment was previously described in 1969, in NASA Special Publication SP-8013, which was used as the basis for a model that will be referred to in this document as the “SP-8013 environment model,” or simply, “SP-8013.” Since around 2020, this model has been used in MMOD risk assessments for the Human Landing System (HLS) program and other lunar surface programs. A new lunar meteoroid ejecta environment was developed via a computer code named Lunar Meteoroid Ejecta Engineering Model (LMEEM), produced by the Natural Environments Branch (NEB) at Marshall Space Flight Center (MSFC). A global lunar surface environment definition using LMEEM is to be provided in the Cross-Program Design Specification for Natural Environments (DSNE) Revision J in 2024. Contact the NASA MSFC Natural Environments Branch for an in-depth discussion of the LMEEM environment model and its derivation. This environment model will supersede SP-8013 for MMOD risk assessments. To perform such assessments, Bumper must read data from text files output by LMEEM and use that data in risk calculations. The purpose of this document is to: •Demonstrate verification that the Bumper code has properly implemented the LMEEM environment model (Section 3) •Discuss the LMEEM environment as understood through an initial environment file (Section 4) •Compare the calculated risk due to the SP-8013 and LMEEM models (Section 5)

Bumper↗
NASA NTRSDate not supplied

Engineering the Interface: Advanced Surface Technologies for Lunar Dust Management and Equipment Longevity

Through the Artemis program, NASA intends to develop a sustainable human foothold on the Moon, ultimately paving the way for crewed exploration of Mars. The Moon's hostile environment poses numerous obstacles, including exposure to radiation, temperature extremes, micrometeoroid threats, and particularly the persistent problem of lunar dust. Lunar dust impacts nearly every aspect of surface operations through adhesion and abrasion mechanisms, with contamination from anthropogenic activities (landing, rovers) far outweighing natural phenomena. Multiple adhesion pathways contribute to surface contamination in the lunar environment, including van der Waals forces, electrostatic forces, chemical reaction, and magnetic forces from elemental iron deposits. Sharp asperities from micrometeoroid bombardment and atmospheric absence increase interaction potential and enable mechanical interlocking. Low cohesion between dust particles exacerbates these challenges, as minimal interaction potential between dust and nearby surfaces overcomes particle cohesion, causing contamination. Lunar dust adhesion mitigation technologies can be categorized as either active, requiring external energy, or passive, relying on intrinsic material properties. Ultrasonic and electrodynamic technologies have been developed to the highest technology readiness level for active approaches. Passive strategies primarily focus on surface chemistry and topography modifications. At NASA Langley Research Center, approaches include surface migration agents to reduce surface energy, topographical modification using laser ablation patterning, and tailored surface conductivity to reduce intrinsic adhesion force. Performance has been evaluated using custom-built ultrasonic and centrifuge instruments. Plume-surface interactions from lunar landers can propel micrometer-sized particles at velocities up to 1000 m s-1.8 These particles pose risks to landers, habitats and infrastructure, leading to erosion, degradation, and reduced component lifespan. A panel recovered from Surveyor III was determined to have been severely abraded because of lunar dust displaced from the Apollo 12 lunar module that landed 160 m away. The performance of metallic surfaces has been evaluated via high velocity single particle impact using the laser-induced project impact test (LIPIT) facility at the University of Utah. Peridynamics modeling, a form of continuum mechanics that uses a nonlocal approach enabling greater simulation capabilities of crack initiation and fracture, has also been utilized to gain greater insight into material response during impact events. Lunar dust contamination challenges extend to power generation systems and moving equipment. Cables, rotation stages, and other mechanisms may experience limited range of motion and reduced lifetime due to dust infiltration. NASA Langley Research Center has evaluated traditional aerospace alloys, softgoods, wear resistant ceramics, and several polymer and polymer composite materials. Test methods have included traditional techniques like Taber abrasion testing, as well as designed test configurations developed in the DUSTE (dust, ultraviolet radiation, and space thermal environmental) chamber that reproduce mechanism functions in operational environment. Beyond laboratory experiments, several flight experiments have been conducted. Materials were exposed to the low Earth orbit environment on the Materials International Space Station Experiment (MISSE) and to the lunar surface environment through the Aegis Aerospace Regolith Adherence Characterization (RAC) payload and the Honeybee Robotics PlanetVac payload. Determining lunar dust's impact on surface exploration and habitation requires comprehensive experimental and computational capabilities combined with lessons learned from initial lunar activities. Identifying the greatest environmental challenges and developing mitigation technologies provides the clearest path toward successfully, expeditiously, and efficaciously completing NASA's mission. This presentation will discuss ongoing efforts at NASA Langley Research Center and collaborator contributions to these critical objectives.

Surface Engineering↗
NASA NTRS1964

Pressurized-cell experiment

Explorer XIII satellite - pressurized-cell detectors for measurement of micrometeoroid puncture hazard

EXPLORER XIII SATELLITE↗
NASA NTRS1966

Some doubts about the Earth's dust cloud.

Inconclusiveness of satellite measurements of micrometeoroid fluxes using piezoelectric microphone detectors in supporting hypothesis of cloud of dust surrounding Earth

MICROMETEOROID↗