Engineering Papers⌕ Search

Engineering topics

Valerie L Wiesner

Publications and source records attributed to Valerie L Wiesner.

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Influence of Cation Species on Thermal Expansion of Y2Si2O7–Gd2Si2O7 Solid Solutions

Mixtures of Y 2 Si 2 O 7 and Gd 2 Si 2 O 7 were synthesized by solid-state reaction at 1600°C and characterized via in situ x-ray diffraction (XRD) to determine their coefficients of thermal expansion (CTE). All solid solutions within the system exhibited the orthorhombic δ-RE 2 Si 2 O 7 (Pna2 1 ) structure. Thermal expansion measurements of Y 2 Si 2 O 7 and Gd 2 Si 2 O 7 correlated well with reported values in literature, and all synthesized solid solutions exhibited CTEs between Y 2 Si 2 O 7 and Gd 2 Si 2 O 7 . Generally, there was a slight decrease in CTE exhibited by the materials with increasing Gd 2 Si 2 O 7 content, with Gd 2 Si 2 O 7 having the lowest CTEs and Y 2 Si 2 O 7 the highest CTEs. The decrease in CTE was attributed to stronger bonds of Gd-O over Y-O, as determined by calculated crystal orbital Hamilton populations using density functional theory. However, such differences were very small and crystal structure was the dominating factor in CTE trends.

rare earth silicates↗
NASA NTRS2022

Thermochemical Degradation of HfSiO4 by Molten CMAS

The thermochemical degradation of hafnium silicate (HfSiO4) was investigated with a molten calcium-magnesium-aluminosilicate (CMAS) glass relevant to gas turbine engine applications. Sintered HfSiO4 coupons were fabricated, within which wells were drilled and filled with CMAS glass powder at a loading of ~35 mg/cm2. Samples were heat treated at1200°C, 1300°C, 1400°C, and 1500°C for 1 hour, 10 hours, and 50 hours. At 1200°C and1300°C, slow formation of a Ca2HfSi4O12 cyclosilicate phase was observed at the HfSiO4-CMASinterface. At 1300°C and higher, rapid infiltration of CMAS into the material along the grain boundaries was observed. Initial conjecture into CMAS degradation mechanisms of HfSiO4 are presented herein.

CMAS↗
NASA NTRSDate not supplied

Assessing Degradation of Advanced Coatings for Carbon/Carbon Composites

Carbon/carbon (C/C) composites are a well-utilized material system for hot structures to enable hypersonic flight. However, C/C materials are susceptible to attack by environmental degradation mechanisms, notably oxidation, which can limit the durability of components resulting in premature failure. Environmental barrier coatings (EBCs) have been developed to mitigate deleterious oxidation. Coating compositions based on silicon carbide (SiC) offer promise as a protective coating material for C/C composites. Under particular hypersonic flight conditions, a passivating silica scale can form at the surface of the EBC, acting as a barrier that can protect the underlying coating and substrate. However, the transition from passive to active oxidation, which varies with temperature and pressure, causes the formation of gaseous SiO that volatilizes leading to detrimental consumption of the SiC coating. In this work, arc-jet testing of SiC-based coatings developed to protect Advanced C/C-6 (ACC-6) was performed under a range of conditions to replicate varying oxidation conditions. In-situ optical emission spectroscopic measurements of the gas-surface interactions were collected and evaluated to render compositional degradation of the coating and underlying composite during arc-jet testing. Specimens were evaluated before, during and after arc-jet testing using destructive and non-destructive materials characterization methods, including optical and scanning electron microscopy and energy dispersive spectroscopy.

Coatings, Hypersonics, Composites↗
NASA NTRSDate not supplied

An Overview of LO-DuSST (Lunar Occupancy Dust Surface Separation Technologies) Objectives

Of the myriad of issues facing lunar exploration and maintaining an extended lunar presence, lunar dust is possibly the most pervasive. These jagged, chemically reactive, electrostatically charged, sometimes magnetic particles can impact every aspect of a lunar surface mission ranging from abrading extra-vehicular activity (EVA) suits to disrupting lunar vehicle thermal management systems to impeding efficacy of excavation equipment to impacting lunar inhabitant health. NASA’s Lunar Occupancy Dust Surface Separation Technologies (LO-DuSST) task, as a part of the broader Lunar Surface Innovation Initiative (LSII) project, seeks to implement synergistic active and passive lunar dust management and mitigation technologies for an array of applications. One such application is protection of power generation capabilities via solar panel arrays. Plasma dust lofting coupled with a piezoelectric-driven vibration technology will be demonstrated on solar panel surfaces contaminated with lunar dust simulant. Intrinsically low adhesion coatings will be applied to these surfaces to enhance dust removal. Electrostatic repulsion in confined geometries and materials to manage high velocity lunar dust wear will also be investigated. Collectively, these active and passive mitigation technologies will facilitate lunar surface operations including occupancy logistics, landing pad operations, power generation, and transportation. Initial results regarding lunar simulant-contaminated solar panel performance experiments, dust lofting using an electron beam, surface interactions of high velocity lunar dust arising from lunar lander plume-surface interactions, and lunar dust simulant-material interaction experiments will be discussed.

Lunar dust↗
NASA NTRSDate not supplied

Bio Inspired Surface Structures to Mitigate Interfacial Particle Adhesion: A Review

Nature has perfected surface chemical and topographical engineering to enable survival in extreme environments. Biomimetics is a rapidly expanding field where biologically inspired design facilitates elegant, yet practical, solutions across many applications. NASA’s ARTEMIS program focused on lunar missions will require unique ways to solve the challenge of highly abrasive, chemically reactive and electrostatically charged lunar dust that adheres strongly to all exposed surfaces and degrades functionality. While seeking solutions to find a surface for mitigating lunar dust adhesion, we looked at natural terrestrial surfaces that successfully minimize dust adhesion and wear for inspiration. Lunar dust is comprised of highly abrasive particles, more than 90% of which are composed of silicate materials. Adapting to somewhat similar particulates in hot and arid deserts of the world, the sandfish lizard has a skin structure that allows it to swim in the sand with minimum friction and adhesion. Special surface adaptations of the tamarisk plant help protect it from severe sandstorms. The desert scorpion has grooves and bumps on its carapace that have been shown to minimize erosion in the sand. Beyond these examples, there are numerous other natural surfaces that have evolved to mitigate particle adhesion and wear. Several efforts have been made by different researchers to replicate these natural surfaces using methods such as laser patterning, 3D printing, chemical vapor deposition and other physical and chemical processes. The resulting bio-inspired patterned surfaces have shown reduction in interfacial particle adhesion, friction, and wear, among other properties. This paper aims to review published research on the subject that might help develop lunar dust adhesion and wear mitigating material surfaces for future lunar applications.

Lunar dust, Lunar surface, Adhesion mitigation, Bi↗
NASA NTRSDate not supplied

Developing Materials and Coating Technologies for Mitigation of Lunar Dust Adhesion and Abrasion

Lunar regolith was first identified as a major issue during the Apollo missions. There are three characteristics of lunar regolith that cause issues: small size, rough surface topology, and particle charge. The lack of a magnetosphere allows solar wind to bombard the lunar surface which results in the regolith becoming charged. These charged particles will adhere to most surfaces and degrade thermal control systems. The lack of atmosphere and surface liquids on the lunar surface results in the regolith’s small particle size, abrasive topology, and chemical reactivity. When the dust adheres to a surface, or the lunar lander exhaust kicks up dust regolith, it can impair instrument or thermal control system function, abrade optical surfaces, diminish range of motion, and mechanically degrade soft-goods such as gloves and astronaut suits. All of these examples were experienced during the Apollo missions. The objective of this study was to select and evaluate abrasion-resistant ceramic materials for application on the lunar landing equipment.

materials↗
NASA NTRSDate not supplied

Passive Dust Mitigation Technologies Being Developed for Demonstration Under Patch Plate Materials Compatibility Analysis Task

With the Artemis program, we are planning longer stays on the surface, with more activities that have the potential to put the astronauts and equipment in contact with greater quantities of lunar dust. The success of these missions will depend on our understanding of material interactions with lunar dust and the development of ways to mitigate dust effects in cases where exposure to dust will lead to failure of components, unacceptable loss of power or thermal control, unacceptable loss of visibility, or health issues. Passive dust mitigation by coating or surface alteration is one method that is being developed and demonstrated under the Space Technology Mission Directorate’s Game Changing Technology, Dust Mitigation Program as part of the Patch Plate Materials Compatibility Assessment Task. The goal of the task is to alter the surfaces of materials in order to passively reduce the adhesion of dust, demonstrate their performance in relevant ground-based tests using lunar simulants, and prepare them for demonstration through experiment on the lunar surface. Optically transparent, sputter deposited, work function matching coatings are being developed to reduce adhesion of dust to windows, lenses and display panels by matching the minimum energy to remove an electron from the surface to that of lunar dust in order to reduce adhesion due to charge transfer. Low surface energy coatings and surfaces for thermal control are also being developed to reduce the bonding of dust with the surface enabling it to be removed more easily. Conductive coatings with the ability to shed dust more easily are being developed for use with the active Electrodynamic Dust Shield technology to help reduce the power needed to remove dust from the surface. Passive dust mitigation surfaces for metals such as aluminum, stainless steel, and titanium are being developed that reduce the area of dust contact with the surfaces through topographical modification using laser ablation patterning to impart hierarchical topographies with nanometer to micrometer length scales in a single step. Topographically modified polymeric materials, both those with extensive space heritage and those with lower technology readiness levels, are also being evaluated. Space suit fabric surfaces that can reduce dust penetration into and through the fabric are also being investigated as well as pristine and topographically modified ceramic materials that exhibit high wear resilience. An overview of the passive dust mitigation surfaces and coatings being developed under this task, ground testing being conducted using lunar simulants, characterization techniques, and materials preparation for flight sample delivery for integration into the Alpha Space Regolith Adherence Characterization experiment going to the lunar surface on a Commercial Lunar Payload Services (CLPS) lander in 2023 will be discussed.

Lunar dust, passive mitigation, lunar simulant, co↗
NASA NTRSDate not supplied

Evaluation of Materials and Surfaces for Lunar Regolith Adherence Characterization (RAC) Payload Samples

As the quest for long term lunar exploration and habitation comes closer to reality, widespread efforts are ongoing to effectively mitigate lunar dust surface contamination and infiltration. This dust is hazardous to humans and tends to adhere tenaciously to all exposed surfaces, causing performance issues and ultimately failure. While several active and passive technologies have been developed to address this challenge, assessing the performance of these technologies in the actual lunar environment is extremely important. The regolith adherence characterization (RAC) experiment payload provides an important opportunity for this evaluation. The RAC payload is designed by Alpha Space for the National Aeronautics and Space Administration (NASA)and scheduled to be flown to the moon in 2023 on the Firefly Aerospace Blue Ghost lander. As there were a limited number of slots available for materials to be chosen for this mission, it was critical to make an informed selection. Two polymers, a carbon fiber reinforced composite and a metal alloy were chosen to be a diverse selection of structural materials from NASA Langley Research Center. Each material was topographically modified using laser ablation patterning. This article briefly describes the selection and testing procedure and some of the results obtained for the passive dust mitigating materials and surfaces selected for this lunar surface experiment.

Lunar Dust↗
NASA NTRSDate not supplied

Laser Ablative Patterning of B4C and MoAlB Ceramics for Hydrophobic Surfaces

Through a novel laser ablative patterning (LAP) process, the present work reports the increase in wetting contact angle of molybdenum aluminum boride (MoAlB) and the reduction of dust adhesion. The LAP technique employed picosecond laser pulses to form a crosshatch pattern with micropillars on ceramic surfaces. The wetting behavior was successfully transitioned from hydrophilic (θ < 90°) to hydrophobic (θ > 90°), which may be related to Wenzel or Cassie-Baxter mechanisms. Parameters such as laser fluence and number of laser scans were varied to study their effects on ceramic surface characteristics. Dust adhesion experiments were performed on these hydrophobic ceramic surfaces, which showed that the adhesion of lunar soil simulant dust particles was significantly reduced in the patterned MoAlB surface. The patterned MoAlB samples were further examined using the surveying lunar dust influence on device efficacy (SLIDE) testbed to evaluate the wear performance.

Bai Cui↗
NASA NTRSDate not supplied

Aligned Boron Nitride Nanotube Reinforced Polyethylene Nanocomposite for Space Radiation Shielding

With NASA’s Artemis program aiming to establish a human presence on the Moon and eventually on Mars, protecting astronauts from radiation is necessary. Flight-heritage materials, like those with high hydrogen content, such as polyethylene (PE), have proven to be effective radiation shields. This is due to hydrogen’s high charge-to-mass ratio, low secondary radiation production, efficient energy absorption, and high cross-section, which increases the probability of particle interactions to slow or stop ionized particles. Boron nitride nanotubes (BNNTs) and other boron-rich materials offer more effective thermal neutron radiation-stopping capabilities due to their high cross-section and neutron absorption properties. BNNTs also enhance the mechanical properties of radiation shielding material due to their high strength-to-weight ratios. However, integrating high volumes of nanotubes in a matrix without defects presents significant manufacturing challenges. To address this, a bulk nanocomposite laminate fabricating technique, involving synthesizing millimeter-long vertically aligned BNNTs, densifying the nanotubes to high-volume fractions, and infusing the nanotubes with PE while applying heat and pressure was utilized to fabricate the BNNT-PE nanocomposite that was tested for its radiation shielding properties at NASA Langley Research Center’s neutron radiation exposure lab. Results from these experiments will be discussed in the presentation.

Palak B Patel↗
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↗