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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Impact Forces From Artificial and Real Birds on a Large Diameter Hopkinson Bar

Forces were measured from normal impacts with two different artificial bird recipes and two species of real birds on a very rigid flat surface. The tests were conducted by launching the soft body projectiles axially into a Hopkinson bar in accordance with the SAE AS6940 test standard at three different nominal impact conditions: (a) a 1 kg projectile at an impact velocity of 49 m/sec; (b) a 1.8 kg projectile at an impact velocity of 110 m/sec; and (c) a 1.8 kg projectile at an impact velocity of 310 m/sec. At each condition two artificial birds and one real bird projectile were tested with at least three test repeats. Simulations were conducted to assess the effects of projectile orientation and velocity on predicted forces. The Hopkinson bar consisted of an Aluminum 6061 solid cylindrical bar with a diameter of 305 mm and a length of 7.31 m, made up of two 3.66 m long sections that were in axial contact with each other. The bar was instrumented for strain measurement at two locations, 457.2 mm and 609.6 mm (1.5 and 2 diameters) from the impacted face. Forces were calculated from the measured strain. In addition, digital image correlation (DIC) was used to measure the velocity of the free end of the bar. The real bird projectiles were 1 kg Mallard ducks and 1.8 kg Golden Comet chickens that were prepared per ASTM F330-21. Prior to testing, the real birds were placed in muslin bags to minimize tumbling during flight. Two artificial bird formulations were tested, one produced by the University of Dayton Research Institute (UDRI) and the other by the German Aerospace Center, DLR. The UDRI projectile was a homogeneous, relatively soft solid, formulated with a mixture of water, gelatin and phenolic micro-balloons to achieve a nominal density of 0.95 g/cc. The DLR projectile consisted of a printed plastic shell with internal plastic ribs and filled with a gel material. The projectiles were designed such that the overall average density was the desired value of 0.95 g/cc. Initial testing showed that contact between the two Hopkinson bar segments was not sufficient to allow full transmission of the waves through the interface. For the 49 m/sec and 110 m/sec tests this resulted in reflections returning to the strain measurement site prior to the end of the impact. For these tests only a portion of the force pulse could be accurately measured. For the highest velocity tests at 310 m/sec the force pulse was complete by the time reflected waves interfered with the response. Despite this limitation, useful force data were obtained for all velocities. Impact forces were very sensitive to the impact orientation and velocity. The force history generally consisted of an initial region with varying amplitude followed by a relatively constant amplitude response. The steady state region was similar among all projectiles and similar to what would be predicted for an inviscid fluid with a density of 0.95 g/cc. The initial part of the force response exhibited varying degrees of test-to-test repeatability associated with each projectile type. Forces calculated from DIC velocity measurements of the free end of the bar compared favorably those from the strain measurements. In general, the artificial projectile impact forces were quite repeatable from test to test, with some exceptions which could be explained by issues associated with either the projectile itself or with how the projectile exited the gun barrel. For all impact velocities the initial portion of the impact force from the bird projectiles exhibited large test-to-test variability. In this paper, impact forces for three types of projectiles at three impact velocities will be presented with an emphasis on the test-to-test repeatability of the results. Based on test and simulation results a proposed method for normalizing the impact force to minimize effects of differences in projectile orientation, impact velocity and density will also be discussed.

Bird strike↗
NASA NTRS1994

Interlaminar shear test method development for long term durability testing of composites

The high speed civil transport is a commercial aircraft that is expected to carry 300 passengers at Mach 2.4 over a range of more than 6000 nautical miles. With the existing commercial structural material technology (i.e., aluminum) the performance characteristics of the high speed civil transport would not be realized. Therefore there has been a concerted effort in the development of light weight materials capable of withstanding elevated temperatures for long duration. Thermoplastic composite materials are such candidate materials and the understanding of how these materials perform over the long term under harsh environments is essential to safe and effective design. The matrix dominated properties of thermoplastic composites are most affected by both time and temperature. There is currently an effort to perform short term testing to predict long term behavior of in-plane mechanical properties E22 (transverse modulus of elasticity) and G12 (shear modulus). Out-of-plane properties such as E33, G13, and G23 are inherently more difficult to characterize. This is especially true for the out-of-plane shear modulus G23 and hence there is no existing acceptable standard test method. Since G23 is the most matrix dominated property, it is essential that a test method be developed. A shear test methodology is developed to do just that. The test method, called the double notched specimen, along with the previously developed shear gage was tested at room temperature. Mechanical testing confirmed the attributes of the methodology. A finite element parametric study was conducted for specimen optimization. Moire interferometry, a high sensitivity laser optical method, was used for full-field analysis of the specimen. From this work, material parameters will be determined and thus enable the prediction of long term material behavior of laminates subjected to general loading states.

Ifju, Peter G.↗
DOE OSTI2024

Prioritizing Off-gas Metrics

Off-gas research within the Material Recovery and Waste Form Development (MRWFD) team is dispersed among four national laboratories and multiple universities and small businesses. Ensuring research is conducted consistently and in a manner conducive to direct comparison is a nontrivial task. The team assembled to realign goals and expectations by identifying distinct R&D phases, prioritizing crucial metrics, and outlining standardized tests specifically associated with Kr, Xe, and I capture.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2015

International Space Station (ISS) 3D Printer Performance and Material Characterization Methodology

In order for human exploration of the Solar System to be sustainable, manufacturing of necessary items on-demand in space or on planetary surfaces will be a requirement. As a first step towards this goal, the 3D Printing In Zero-G (3D Print) technology demonstration made the first items fabricated in space on the International Space Station. From those items, and comparable prints made on the ground, information about the microgravity effects on the printing process can be determined. Lessons learned from this technology demonstration will be applicable to other in-space manufacturing technologies, and may affect the terrestrial manufacturing industry as well. The flight samples were received at the George C. Marshall Space Flight Center on 6 April 2015. These samples will undergo a series of tests designed to not only thoroughly characterize the samples, but to identify microgravity effects manifested during printing by comparing their results to those of samples printed on the ground. Samples will be visually inspected, photographed, scanned with structured light, and analyzed with scanning electron microscopy. Selected samples will be analyzed with computed tomography; some will be assessed using ASTM standard tests. These tests will provide the information required to determine the effects of microgravity on 3D printing in microgravity.

Bean, Q. A.↗
NASA NTRS1997

Adhesion Performance of Solid Film Lubricants on Substrates Cleaned With Environmentally Compliant Cleaners

Solid film adhesion testing was used to determine the effect different environmentally compliant cleaners have on the adhesion properties of solid film lubricants used for several NASA programs. In an action to remove ozone depleting chemicals from aerospace processes, a replacement cleaner must be identified that does not affect the adhesion of solid film lubricants used on flight critical NASA hardware. ASTM D251083 Standard Test Method for Adhesion of Solid Film Lubricants was used to evaluate the cleaners. Two different lubricants - Inlox 88 and Boosterlube - were tested using various commercially available cleaners. Inlox 88 is produced by E/M Corporation and is a liquid oxygen compatible lubricant used in the Space Shuttle Main Engine, and Boosterlube is a new lubricant being implemented for use on the Space Shuttle Solid Rocket Booster. These lubricants were selected because of their specific use on flight critical NASA components. Results of this testing are presented in the paper.

Hall, P. B.↗
DOE OSTI2022

Potential-induced degradation of Cu(In,Ga)Se 2 can occur by shunting the front i-ZnO and by damaging the p-n junction

In this work we test field-relevant potential-induced degradation (PID) behavior by encapsulating laboratory Cu(In,Ga)Se 2 (CIGS) solar cells and applying +1000 V uniformly on the face of the front glass. In this configuration, we find that K-rich borosilicate glass reduces the extent of PID relative to Na-rich soda-lime glass. We also find that the standard testing protocol of stressing cells at short-circuit leads to faster PID than stressing cells at open-circuit. We characterize two types of CIGS PID: The first, front shunting PID, is driven by front-glass stress and occurs when alkali metal cations accumulate in the i-ZnO buffer, where they increase shunt conductance to reduce fill factor. The second, p-n junction PID, results from back-glass stress as alkali metal cations pile up near the CIGS surface/CdS buffer, where they reduce charge carrier concentration, open-circuit voltage, and fill factor to degrade efficiency ~160 times faster than front shunting PID.

14 SOLAR ENERGY↗
NASA NTRS2014

Enabling Technologies for Entrepreneurial Opportunities in 3D printing of SmallSats

A consortium of innovative experts in additive manufacturing (AM) comprising Northrup Grumman Technical Services, University of Texas at El Paso (UTEP), Configurable Space Microsystems Innovations & Applications Center (COSMIAC), NASA Glenn Research Center (GRC), and Youngstown State University, have made significant breakthroughs in the goal of creating the first complete 3D printed small satellite. Since AM machines are relatively inexpensive, this should lead to many entrepreneurial opportunities for the small satellite community. Our technology advancements are focused on the challenges of embedding key components within the structure of the article. We have demonstrated, using advanced fused deposition modeling techniques, complex geometric shapes which optimize the spacecraft design. The UTEP Keck Center has developed a method that interrupts the printing process to insert components into specific cavities, resulting in a spacecraft that has minimal internal space allocated for what traditionally were functional purposes. This allows us to increase experiment and instrument capability by provided added volume in a confined small satellite space. Leveraging initial progress made on a NASA contract, the team investigated the potential of new materials that exploit the AM process, producing candidate compositions that exceed the capabilities of traditional materials. These "new materials" being produced and tested include some that have improved radiation shielding, increased permeability, enhanced thermal properties, better conductive properties, and increased structural performance. The team also investigated materials that were previously not possible to be made. Our testing included standard mechanical tests such as vibration, tensile, thermal cycling, and impact resistance as well as radiation and electromagnetic tests. The initial results of these products and their performance will be presented and compared with standard properties. The new materials with the highest probability to disrupt the future of small satellite systems by driving down costs will be highlighted, in conjunction with the electronic embedding process.

Communications↗
DOE OSTI2025

Polarization-type potential-induced degradation in bifacial PERC modules in the field

This study examines the susceptibility of bifacial glass/glass passivated emitter and rear cell (PERC) modules to potential-induced degradation-polarization (PID-p) in the field. While there are several studies showing PID-p occurring on both front and back faces of bifacial PERC in accelerated tests, we address the yet unclarified behavior in fielded modules. We examine the effects of mounting configuration; specifically, comparing modules mounted near ground and in elevated ground rack configurations. Modules with the cell circuit in -1500 V system voltage configuration, whether mounted on racks about 30 cm above the ground or elevated 2 m high showed mean degradation of 4.5% to 6% in power under standard test conditions over about 2.5 weeks as measured from the front side of the module. This extent of degradation remained sustained for a duration of about 6 months analyzed. Average daytime temperatures of modules in the various mounting configurations were similar and therefore judged to be insufficient to be a primary influence for the modest PID-p rate differences that we observed among mounting configurations. Increased leakage current in the morning suggests morning dew was sustained longer on modules near the ground measured over six months which would be expected to increase the PID-p rate over the long term. However, the main difference seen between the modules on the various mountings during the initial period with up to 6% mean degradation by PID-p was the approximately two times the irradiance from albedo on the rear of modules mounted in elevated ground rack compared to those on the near ground rack. This difference in incident albedo led to a modestly reduced rate of the development of PID-p of the modules on the elevated ground rack. The difference is attributed to the dissipation of PID-p-causing electrical charge by the albedo incident on the module rear. The behavior could be modeled by a sigmoidal equation with consideration of the differences in the insolation on the module rear.

14 SOLAR ENERGY↗
NASA NTRS2014

Repeatability Modeling for Wind-Tunnel Measurements: Results for Three Langley Facilities

Data from extensive check standard tests of seven measurement processes in three NASA Langley Research Center wind tunnels are statistically analyzed to test a simple model previously presented in 2000 for characterizing short-term, within-test and across-test repeatability. The analysis is intended to support process improvement and development of uncertainty models for the measurements. The analysis suggests that the repeatability can be estimated adequately as a function of only the test section dynamic pressure over a two-orders- of-magnitude dynamic pressure range. As expected for low instrument loading, short-term coefficient repeatability is determined by the resolution of the instrument alone (air off). However, as previously pointed out, for the highest dynamic pressure range the coefficient repeatability appears to be independent of dynamic pressure, thus presenting a lower floor for the standard deviation for all three time frames. The simple repeatability model is shown to be adequate for all of the cases presented and for all three time frames.

Hemsch, Michael J.↗
NASA NTRS2010

A Singular Perturbation Approach for Time-Domain Assessment of Phase Margin

This paper considers the problem of time-domain assessment of the Phase Margin (PM) of a Single Input Single Output (SISO) Linear Time-Invariant (LTI) system using a singular perturbation approach, where a SISO LTI fast loop system, whose phase lag increases monotonically with frequency, is introduced into the loop as a singular perturbation with a singular perturbation (time-scale separation) parameter Epsilon. First, a bijective relationship between the Singular Perturbation Margin (SPM) max and the PM of the nominal (slow) system is established with an approximation error on the order of Epsilon(exp 2). In proving this result, relationships between the singular perturbation parameter Epsilon, PM of the perturbed system, PM and SPM of the nominal system, and the (monotonically increasing) phase of the fast system are also revealed. These results make it possible to assess the PM of the nominal system in the time-domain for SISO LTI systems using the SPM with a standardized testing system called "PM-gauge," as demonstrated by examples. PM is a widely used stability margin for LTI control system design and certification. Unfortunately, it is not applicable to Linear Time-Varying (LTV) and Nonlinear Time-Varying (NLTV) systems. The approach developed here can be used to establish a theoretical as well as practical metric of stability margin for LTV and NLTV systems using a standardized SPM that is backward compatible with PM.

Zhu, J. Jim↗
NASA NTRS2011

Astronaut Medical Selection and Flight Medicine Care During the Shuttle ERA 1981 to 2011

The NASA Shuttle Program began with congressional budget approval in January 5, 1972 and the launch of STS-1 on April 12, 1981 and recently concluded with the landing of STS-135 on July 21, 2011. The evolution of the medical standards and care of the Shuttle Era Astronauts began in 1959 with the first Astronaut selection. The first set of NASA minimal medical standards were documented in 1977 and based on Air Force, Navy, Department of Defense, and the Federal Aviation Administration standards. Many milestones were achieved over the 30 years from 1977 to 2007 and the subsequent 13 Astronaut selections and 4 major expert panel reviews performed by the NASA Flight Medicine Clinic, Aerospace Medicine Board, and Medical Policy Board. These milestones of aerospace medicine standards, evaluations, and clinical care encompassed the disciplines of preventive, occupational, and primary care medicine and will be presented. The screening and retention standards, testing, and specialist evaluations evolved through periodic expert reviews, evidence based medicine, and Astronaut medical care experience. The last decade of the Shuttle Program saw the development of the International Space Station (ISS) with further Space medicine collaboration and knowledge gained from our International Partners (IP) from Russia, Canada, Japan, and the European Space Agencies. The Shuttle Program contribution to the development and implementation of NASA and IP standards and waiver guide documents, longitudinal data collection, and occupational surveillance models will be presented along with lessons learned and recommendations for future vehicles and missions.

Johnston, S.↗
NASA NTRS1982

Report of the subpanel on resampling functions

The state of the art and anticipated requirements for resampling in applications of remote sensing are examined. It is noted that the wide range of potential applications and expanded needs for resampling versatility in new imaging sensors leads to a concern for creating standardized test data sets and ground training sites. Several research areas are defined including the development of (1) a theory for defining an input psf of an instrument such that upon resampling of the processed data into the desired output grid the radiometric and geometric properties are a best estimate of the true upwelling radiances; (2) algorithms for estimating missing data or for ignoring missing data; (3) optimal resampling functions; (4) standard data sets; and (5) merit functions for assessing resampling techniques.

Source record↗
NASA NTRSDate not supplied

Analysis of Handling Qualities and Power Consumption for Urban Air Mobility (UAM) eVTOL Quadrotors with Degraded Heave Disturbance Rejection and Control Response

A piloted handling qualities study of urban air mobility (UAM) electric vertical take-off and landing (eVTOL) quadrotors was performed utilizing the Vertical Motion Simulator (VMS) facility at NASA Ames Research Center. Rotor speed and variable pitch-controlled variants of a six-passenger conceptual design vehicle were assessed with different levels of degradation to control response and disturbance rejection bandwidth (DRB) in the heave axis. In previous work, preliminary trends across several handling quality rating categories reflected the effects of these degradations. Additionally, the impact of using different test standards and turbulence on the ratings were discussed. This paper elaborates on those results, but also provides insight into unexpected trends observed during the study including: a disharmony in attitude response, subpar ratings for the baseline Level 1 performance vehicle, and excessive drift and yaw couplings observed in a lateral reposition maneuver. Moreover, shortcomings of the handling quality scales and comparisons of power consumption among the vehicles in the various test conditions are presented.

Handling Qualities↗
DOE OSTI2021

BeeSwarm: Enabling Parallel Scaling Performance Measurement in Continuous Integration for HPC Applications

Testing is one of the most important steps in software development–it ensures the quality of software. Continuous Integration (CI) is a widely used testing standard that can report software quality to the developer in a timely manner during development progress. Performance, especially scalability, is another key factor for High Performance Computing (HPC) applications. There are many existing profiling and performance tools for HPC applications, but none of these are integrated into CI tools. In this work, we propose BeeSwarm, an HPC container based parallel scaling performance system that can be easily applied to the current CI test environments. BeeSwarm is mainly designed for HPC application developers who need to monitor how their applications can scale on different compute resources. We demonstrate BeeSwarm using a multi-physics HPC application with Travis CI, GitLab CI and GitHub Actions while using ChameleonCloud and Google Compute Engine as the compute backends. Finally, our results show that BeeSwarm can be used for scalability and performance testing of HPC applications.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS2011

Selected Parametric Effects on Materials Flammability Limits

NASA-STD-(I)-6001B Test 1 is currently used to evaluate the flammability of materials intended for use in habitable environments of U.S. spacecraft. The method is a pass/fail upward flame propagation test conducted in the worst case configuration, which is defined as a combination of a material s thickness, test pressure, oxygen concentration, and temperature that make the material most flammable. Although simple parametric effects may be intuitive (such as increasing oxygen concentrations resulting in increased flammability), combinations of multi-parameter effects could be more complex. In addition, there are a variety of material configurations used in spacecraft. Such configurations could include, for example, exposed free edges where fire propagation may be different when compared to configurations commonly employed in standard testing. Studies involving combined oxygen concentration, pressure, and temperature on flammability limits have been conducted and are summarized in this paper. Additional effects on flammability limits of a material s thickness, mode of ignition, burn-length criteria, and exposed edges are presented. The information obtained will allow proper selection of ground flammability test conditions, support further studies comparing flammability in 1-g with microgravity and reduced gravity environments, and contribute to persuasive scientific cases for rigorous space system fire risk assessments.

Hirsch, David B.↗
NASA NTRS2010

Promoted Combustion Test Data Re-Examined

Promoted combustion testing of metallic materials has been performed by NASA since the mid-1980s to determine the burn resistance of materials in oxygen-enriched environments. As the technolo gy has advanced, the method of interpreting, presenting, and applying the promoted combustion data has advanced as well. Recently NASA changed the bum criterion from 15 cm (6 in.) to 3 cm (1.2 in.). This new burn criterion was adopted for ASTM G 124, Standard Test Method for Determining the Combustion Behavior- of Metallic Materials in Oxygen-Enriched Atmospheres. Its effect on the test data and the latest method to display the test data will be discussed. Two specific examples that illustrate how this new criterion affects the burn/no-bum thresholds of metal alloys will also be presented.

Lewis, Michelle↗
DOE OSTI2022

Application of New Los Alamos OPLIB Opacities in Solar Modeling Using the Mesa Code

The Sun provides the only local laboratory to test our understanding of stellar physics. The production, then, of valid dynamical models of the Sun is critical to how we think about other stars. Despite improvements in modeling methodologies and abundance measurements, solar models continue to reproduce errors in convection zone depth and surface helium abundance compared to helioseismic observations. Using the 1D stellar evolution code MESAstar, this work first evaluates the effect of changes to timestep resolution and mixing length theory on model outputs. A standard test case is then constructed with both GS98 and AGSS09 abundances using OP and OPAL opacities before implementing the new Los Alamos OPLIB opacities. It is shown that, when using GS98 abundances, OPLIB opacities improve agreement with helioseismic inference of the convection zone base radius, R czb , by 1.68-σ and 1.19-σ compared to OP and OPAL, respectively, while worsening agreement with the inferred envelope helium mass fraction, Y surf , by 0.63-σ and 0.98-σ for OP and OPAL.

14 SOLAR ENERGY↗
DOE OSTI2020

Impact of undoped substrates on high performance silicon solar cells

Today's highest-efficiency silicon solar cells typically operate near the threshold between low-level and high-level injection. It is not well understood if pushing further into a regime in which the cell operating point is solidly in high-level injection at all times of the day has further benefits for the solar cell performance. From a reliability perspective, cells fabricated on lower doped silicon have a larger breakdown voltage. This advantage can affect the design of modules allowing higher voltages and a relaxation of the number of bypass diodes needed. In this project, we present a comprehensive assessment, both experimental and using simulation, of how bulk resistivity, light intensity, and operation temperature impact the performance of the silicon solar cell. This work incorporates a comprehensive device physics analysis assisted by numerical simulation. The source code is now available under General Public License (GPL3), and to further leverage the findings of this project and outreach people outside of the scientific community, we are working with www.pveducation.org (which receives >1 million visitors a year) to create interactive content using our simulation results. The simulation results indicate that high bulk resistivity wafers (>>10 Ωcm) require bulk Shockley-Read-Hall (SRH) lifetimes in the millisecond range to outperform wafers with standard bulk resistivities (<10 Ωcm). Additionally, above bulk resistivities of 10 Ωcm (the exact value depends on the bulk characteristics of the wafer), the cell efficiency is weakly dependent on the bulk resistivity. As a result, ingot manufactures may have an opportunity to further reduce wafer cost by growing higher resistivity ingots that are more tolerant to resistivity variations. This project is particularly relevant today, as solar cell architectures with improved surface passivation and milliseconds lifetimes wafers are commercially available, leveraging potential benefits of using higher bulk resistivities. Outside of interdigitated back contact (IBC) cell, reported studies on high resistivity silicon (>100 Ωcm) are very limited. To the best of our knowledge, this project provides for the first-time experimental insight on solar cells fabricated on wafers with bulk resistivities up to several thousand Ωcm, delivering a comprehensive vision of their performance under real-world temperature and light intensity operation conditions. We manufactured and characterized solar cells with bulk resistivities in the range of 1 Ωcm to >15k Ωcm. Under standard testing conditions (STC), we measured solar cells efficiencies over 20% over the entire range of bulk resistivities, using our baseline cell processing. To evaluate the cell performance in real-world operation conditions, the solar cells were measured at different temperatures (25-80°C) and at different light intensities (0.1-1 suns). The measurements show that the bulk resistivity does not impact the solar cell response to temperature and light intensity. Similar thermal coefficients (TC) were measured for standard and high bulk resistivities, and they are comparable with the TC values reported in the literature for standard bulk resistivities <10 Ωcm. After light soaking, the solar cell didn’t show signs of light-induced degradation (LID). This result was expected since n-type float zone (FZ) wafers were used in this work, i.e. low traces of boron and low concentration of oxygen (oxygen is typically found in the seed end of Czochralski (CZ) ingots). We measured for high bulk resistivities (>10 Ωcm) extremely high breakdown voltages (>1000V). In conclusion, the insight provided by this project can positively impact the levelized cost of energy (LCOE) of the photovoltaic systems through its effect on cell and ingot manufacturing yield, silicon cell power output, and module reliability.

14 SOLAR ENERGY↗