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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Resin Systems and Chemistry-Degradation Mechanisms and Durability in Long-Term Durability of Polymeric Matrix Composites

In choosing a polymer-matrix composite material for a particular application, a number of factors need to be weighed. Among these are mechanical requirements, fabrication method (e.g. press-molding, resin infusion, filament winding, tape layup), and use conditions. Primary among the environmental exposures encountered in aerospace structures are moisture and elevated temperatures, but certain applications may require resistance to other fluids and solvents, alkaline agents, thermal cycling, radiation, or rapid, localized heating (for example, lightning strike). In this chapter, the main classes of polymer resin systems found in aerospace composites will be discussed. Within each class, their responses to environmental factors and the associated degradation mechanisms will be reviewed.

Hinkley, Jeffrey A.↗
NASA NTRS2013

Calcium-Magnesium-Aluminosilicate (CMAS) Reactions and Degradation Mechanisms of Advanced Environmental Barrier Coatings

The thermochemical reactions between calcium-magnesium-aluminosilicate- (CMAS-) based road sand and several advanced turbine engine environmental barrier coating (EBC) materials were studied. The phase stability, reaction kinetics and degradation mechanisms of rare earth (RE)-silicates Yb2SiO5, Y2Si2O7, and RE-oxide doped HfO2 and ZrO2 under the CMAS infiltration condition at 1500 C were investigated, and the microstructure and phase characteristics of CMAS-EBC specimens were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Experimental results showed that the CMAS dissolved RE-silicates to form crystalline, highly non-stoichiometric apatite phases, and in particular attacking the silicate grain boundaries. Cross-section images show that the CMAS reacted with specimens and deeply penetrated into the EBC grain boundaries and formed extensive low-melting eutectic phases, causing grain boundary recession with increasing testing time in the silicate materials. The preliminary results also showed that CMAS reactions also formed low melting grain boundary phases in the higher concentration RE-oxide doped HfO2 systems. The effect of the test temperature on CMAS reactions of the EBC materials will also be discussed. The faster diffusion exhibited by apatite and RE-doped oxide phases and the formation of extensive grain boundary low-melting phases may limit the CMAS resistance of some of the environmental barrier coatings at high temperatures.

Ahlborg, Nadia L.↗
NASA NTRS2014

NASA's Advanced Environmental Barrier Coatings Development for SiC/SiC Ceramic Matrix Composites: Understanding Calcium Magnesium Alumino-Silicate (CMAS) Degradations and Resistance

Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is essential to the viability and reliability of the envisioned CMC engine component applications, ensuring integrated EBC-CMC system durability and designs are achievable for successful applications of the game-changing component technologies and lifing methodologies.This paper will emphasize recent NASA environmental barrier coating developments for SiCSiC turbine airfoil components, utilizing advanced coating compositions, state-of-the-art processing methods, and combined mechanical and environment testing and durability evaluations. The coating-CMC degradations in the engine fatigue-creep and operating environments are particularly complex; one of the important coating development aspects is to better understand engine environmental interactions and coating life debits, and we have particularly addressed the effect of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the durability of the environmental barrier coating systems, and how the temperature capability, stability and cyclic life of the candidate rare earth oxide and silicate coating systems will be impacted in the presence of the CMAS at high temperatures and under simulated heat flux conditions. Advanced environmental barrier coating systems, including HfO2-Si with rare earth dopant based bond coat systems, will be discussed for the performance improvements to achieve better temperature capability and CMAS resistance for future engine operating conditions.

Environmental barrier coatings↗
NASA NTRS2015

Degradation of Endeavour Crater, Mars

The Opportunity rover has traversed portions of two western rim segments of Endeavour, a 22 km-diameter crater in Meridiani Planum, for the past three years. The resultant data enables the evaluation of the geologic expression and degradation state of the crater. Endeavour is Noa-chian-aged, complex in morphology, and originally may have appeared broadly similar to the more pristine 20.5 km-diameter Santa Fe complex crater in Lunae Palus (19.5degN, 312.0degE). By contrast, Endeavour is considerably subdued and largely buried by younger sulfate-rich plains. Exposed rim segments dubbed Cape York (CY) and Solander Point/Murray Ridge/Pillinger Point (MR) located approximately1500 m to the south reveal breccias interpreted as remnants of the ejecta deposit, dubbed the Shoemaker Formation. At CY, the Shoemaker Formation overlies the pre-impact rocks, dubbed the Matijevic Formation.

Grant, J. A.↗
NASA NTRS2016

A Consistent AVHRR Visible Calibration Record Based on Multiple Methods Applicable for the NOAA Degrading Orbits: Validation - Part 2

Consistent cross-sensor Advanced Very High Resolution Radiometer (AVHRR) calibration coefficients are determined using desert, polar ice, and deep convective cloud (DCC) invariant Earth targets. The greatest AVHRR calibration challenge is the slow orbit degradation of the host satellite, which precesses toward a terminator orbit. This issue is solved by characterizing the invariant targets with NOAA-16 AVHRR observed radiances that have been referenced to the Aqua Moderate Resolution Imaging Spectrometer (MODIS) calibration using simultaneous nadir overpass (SNO) observations. Another benefit of the NOAA-16 invariant target-modeled reflectance method is that, because of the similarities among the AVHRR spectral response functions, a smaller spectral band adjustment factor is required than when establishing calibrations relative to a non-AVHRR reference instrument. The sensor- and band-specific calibration uncertainties, with respect to the calibration reference, are, on average, 2 percent and 3 percent for channels 1 and 2, respectively. The uncertainties are smaller for sensors that are in afternoon orbits, have longer records, and spend less time in terminator conditions. The multiple invariant targets referenced to Aqua MODIS (MITRAM) AVHRR calibration coefficients are evaluated for individual target consistency, compared against Aqua MODIS/AVHRR SNOs, and selected published calibration gains. The MITRAM and SNO relative calibration biases mostly agree to within 1 percent for channels 1 and 2, respectively. The individual invariant target and MITRAM sensor relative calibration biases are mostly consistent to within 1 percent and 2 percent for channels 1 and 2, respectively. The differences between the MITRAM and other published calibrations are mostly attributed to the reference instrument calibration differences.

Doelling, David R.↗
NASA NTRS2017

Acoustic Detection of Faults and Degradation in a High-Bypass Turbofan Engine during VIPR Phase III Testing

The Vehicle Integrated Propulsion Research (VIPR) Phase III project was executed at Edwards Air Force Base, California, by the National Aeronautics and Space Administration and several industry, academic, and government partners in the summer of 2015. One of the research objectives was to use external radial acoustic microphone arrays to detect changes in the noise characteristics produced by the research engine during volcanic ash ingestion and seeded fault insertion scenarios involving bleed air valves. Preliminary results indicate the successful acoustic detection of suspected degradation as a result of cumulative exposure to volcanic ash. This detection is shown through progressive changes, particularly in the high-frequency content, as a function of exposure to greater cumulative quantities of ash. Additionally, detection of the simulated failure of the 14th stage stability bleed valve and, to a lesser extent, the station 2.5 stability bleed valve, to their fully-open fail-safe positions was achieved by means of spectral comparisons between nominal (normal valve operation) and seeded fault scenarios.

noise spectra↗
NASA NTRS2017

Materials Degradation in the Jovian Radiation Environment

The radiation environment of Jupiter represents a significant hazard for Europa Lander deorbit stage components, and presents a significant potential mission risk. The radiolytic degradation of ammonium perchlorate (AP) oxidizer in solid propellants may affect its properties and performance. The Monte Carlo code MONSOL was used for modeling of laboratory experiments on the electron irradiation of propellant samples. An approach for flattening dose profiles along the depth of irradiated samples is proposed. Depth-dose distributions produced by Jovian electrons in multi-layer slabs of materials are calculated. It is found that the absorbed dose in a particular slab is significantly affected by backscattered electrons and photons from neighboring slabs. The dose and radiolytic decomposition of AP crystals are investigated and radiation-induced chemical yields and weight percent of radical products are reported.

Miloshevsky, Gennady↗
NASA NTRS2019

Effect of Environments on Parametric Degradation in Polymer Tantalum Capacitors

Chip polymer tantalum capacitors (CPTCs) are more sensitive to environments compared to conventional, MnO2 cathode capacitors. Contrary to MnO2 capacitors, CPTCs can degrade with time of storage even in dry conditions, that might limit their use for space applications. Performance of CPTCs depends on the amount of moisture in the slug, and varies with time of storage after manufacturing. For this reason, characteristics of the parts and qualification testing should be carried out after preconditioning to stabilize moisture content. This work analyzes kinetics of moisture sorption and desorption in different types of CPTCs from three manufacturers. Variations of capacitance, dissipation factor, ESR, and leakage currents caused by exposure to humid, dry, and radiation environments are discussed. Examples of the effects of long-term exposure to vacuum and humid environments at 85%RH are presented. Temperature dependencies of the characteristic times of moisture diffusion allow for assessments of the bake-out times that are necessary to avoid pop-corning failures after soldering and to precondition parts before qualification testing.

Teverovsky, Alexander↗
NASA NTRS2017

A Study of the Degradation of Electronic Speed Controllers for Brushless DC Motors

Brushless DC motors are frequently used in electric aircraft and other direct drive applications. As these motors are notactually direct current machines but synchronous alternating current machines; they are electronically commutated by a power inverter. The power inverter for brushless DC motors typically used in small scale UAVs is a semiconductor base delectronic commutator that is external to the motor and is referred to as an electronic speed control (ESC). This paper examines the performance changes of a UAV electric propulsion system resulting from ESC degradation. ESC performance is evaluated in simulation and on a new developed test bed featuring propulsion components from a reference UAV. An increase in the rise fall times of the switched voltages is expected to cause timing issues at high motor speeds. This study paves the way for further development of diagnostic and prognostic methods for inverter circuits which are part of the overall electric UAV system.

Gorospe, George E., Jr.↗
NASA NTRS1997

Degradation of Precision Reference Devices in Space Environments

This paper presents radiation test results for several different precision voltage devices. Their degradation is compared to that expected for the basic bandgap reference circuit, which is used as a theoretical benchmark, and uses only npn transistorss.

Precision↗
NASA NTRSDate not supplied

Urine Concentration of Cartilage Degradation Marker CTX-II is Sensitive to Microgravity

Mechanical and gravitation load are both important regulators of articular cartilage metabolism. Immobilization and the absence of gravity likely change tissue characteristics that can result in atrophy and softening of cartilage. Type II collagen is the most abundant cartilage matrix protein. Assessing urinary excretion of crosslinked C-telopeptide (uCTX-II) provides an index of total type II collagen degradation. We hypothesized that reduced mechanical and gravitational loading during a 4 – 6 months International Space Station (ISS) mission will result in increased uCTX-II levels.

Anna-maria Liphardt↗
NASA NTRSDate not supplied

Response of Ablative Thermal Protection Materials to Degradation in Low Earth Orbit –Characterization of Specimens from MISSE-13

The environment of low Earth orbit presents unique material interactions due to the presence of atomic oxygen and solar spectrum UV. A variety of degradation mechanisms can occur depending, inlarge part, on the specific material system involved. This talk will review the characterization of two ablative materials, PICA-D and HEEET, as well as relevant adhesive joints and coatings. PICA-D is a variant of the phenolic impregnated carbon ablator (PICA) and is the baseline thermal protection system (TPS) on Dragonfly and the lander for Mars Sample Return (MSR). HEEET is a 3D woven system from which MSR’s Earth entry TPS is derived. The samples for these materials were flown in orbit during the Materials International Space Station Experiment-13 (MISSE-13) which launched on March 6, 2020 and returned to Earth on January 13, 2021. Changes to surface microstructure and reflectivity will be presented along with tomographic analysis. The effect of differential erosion rates on the composites and the impacts of the orbit environment on coating performances will be discussed in the context of TPS performance and mission design aspects.

MISSE↗
NASA NTRSDate not supplied

Response of Ablative Thermal Protection Materials to Degradation in Low Earth Orbit – Characterization of Specimens from MISSE-13

The environment of low Earth orbit presents unique material interactions due to the presence of atomic oxygen and solar spectrum UV. A variety of degradation mechanisms can occur depending, in large part, on the specific material system involved. This talk will review the characterization of two ablative materials, PICA-D and HEEET, as well as relevant adhesive joints and coatings. PICA-D is a variant of the phenolic impregnated carbon ablator (PICA) and is the baseline thermal protection system (TPS) on Dragonfly and the lander for Mars Sample Return (MSR). HEEET is a 3D woven system from which MSR’s Earth entry TPS is derived. The samples for these materials were flown in orbit during the Materials International Space Station Experiment-13 (MISSE-13) which launched on March 6, 2020 and returned to Earth on January 13, 2021. Changes to surface microstructure and reflectivity will be presented along with tomographic analysis. The effect of differential erosion rates on the composites and the impacts of the orbit environment on coating performances will be discussed in the context of TPS performance and mission design aspects.

MISSE↗
NASA NTRS2023

Unalakleet Climate: Analyzing Permafrost Degradation and Drainage Networks in Unalakleet, Alaska

The coastal community of Unalakleet is currently the 8th most at-risk community in Alaska due to the adverse effects of climate change that include permafrost degradation, severe coastal erosion, and sea-level rise-induced flood inundation caused by increasingly frequent storm surges. In response, the community has started a managed relocation with support from the Native Village of Unalakleet (NVU) and the National Renewable Energy Lab (NREL)’s Alaska campus in Fairbanks. The Unalakleet Climate NASA DEVELOP team partnered with NREL to provide remote sensing support and analysis for resilience planning in Unalakleet, supporting their ongoing relocation efforts and guiding future expansion. The team utilized Sentinel-1 C-Synthetic Aperture Radar (SAR), WorldView-2, and WorldView-3 datasets from 2017 – 2023 to analyze seasonal summer subsidence and utilized a 2014 Ancillary USGS 5 m Alaska DEM to conduct drainage network analyses that included watershed delineation and Height Above Nearest Drainage (HAND) analysis. The team also used high-resolution WorldView images to locate stable reference points that served as quality control for the team’s analyses. The team’s end products included maps containing subsidence and drainage zones information at and surrounding the relocation site. The team’s products provide NREL with valuable data that enables them to better assist Unalakleet’s managed relocation and assists Unalakleet with adapting to the catastrophic effects of climate change and build resilience in a community on the front lines of climate change.

Ian Lee↗
NASA NTRSDate not supplied

Experimental Characterization of Non-Associative Plasticity Flow Rule Coefficients and Post-Peak Stress Degradation for the LS-DYNA MAT213 Model

This project is focused on developing an experimental framework for characterizing non-associative plasticity flow rule coefficients through coupon-scale tests for the LS-DYNA MAT213 model. The main objective is to characterize these coefficients based on the multi-scale (i.e., both microscopic and macroscopic) full-field measurement of the evolution of strain and stress fields. This paper focuses on presenting the experimental work on characterizing the full-scale stress-strain curves of T700/LM-PAEK composites under tension, compression, and shear loads. The experimental data set was intended to build a deformation sub-model in the MAT213 model for the material. The strain data were collected using both microscopic and macroscopic digital image correlation techniques. The microscopic technique was particularly useful for fracture cases under small strains. A preliminary simulation result obtained from the MAT213 model is also presented in the paper. The experimental framework herein will be extended to characterize post-peak stress degradation in the composite material and to develop a damage sub-model for the material. This project will contribute to developing a simulation tool based on the MAT213 model for simulating the rate-dependent impact damage in composites under multi-axial loading.

MAT213↗
NASA NTRS2024

The Effect of Impingement Angle on Bipropellant Thruster Plume Degradation of Spacecraft Materials

Unburned and partially combusted liquid propellant present in bipropellant thruster plumes can contaminate and damage external spacecraft materials. Microscopic impact features due to high-speed droplet impacts have been observed on space shuttle flight experiments and International Space Station (ISS) returned flight hardware. Analytical results have shown that particle impingement angle greatly affects surface damage, with normal impacts being the most severe and highly oblique impacts being more benign. The effect of thruster plume impingement angle on material degradation has now been further studied following a bipropellant thruster plume test performed at the high-vacuum plume test facility for chemical thrusters at DLR Göttingen, STG-CT. Several spacecraft material samples were exposed to the freely expanding pulsed thruster plume at a range of impingement angles (from 0 to 75 deg). Results of post-test evaluations and potential spaceflight applications are summarized.

Gateway↗