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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Impact damage tolerance of thin wall composite struts

An experimental investigation was made to study the impact damage tolerance of thin wall composite struts made of both brittle epoxy and toughened epoxy based composite materials. Damage parameters such as barely visible surface damage and internal damage represented by the ultrasonic C-scan, and residual compressive strengths were evaluated against impact energy for two impactor sizes. From both a damage resistance (internal damage vs. impact energy) and a damage tolerance (residual compressive strength vs. internal damage) point of view, the toughened IM7/977-2 struts exhibited better performance than the brittle epoxy based T50/934 struts. This is attributed to the toughening mechanism in 977-2 which impedes delamination initiation from impact, and delamination growth and subsequent buckling under a compression loading. At barely visible damage thresholds, regardless of the impactor sizes, a maximum strength reduction of 45-55 percent was observed for the T50/934 struts, and approximately 10 percent for IM7/977-2 struts. This is of great interest for developing a damage tolerance design approach and risk assessment methodology in which the design allowable would be defined by the residual strength at the threshold of barely visible damage.

Chen, G.-S.↗
NASA NTRS1992

Static and dynamic strain energy release rates in toughened thermosetting composite laminates

In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high rate, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to strain rate effects for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical strain energy release rate drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of examining rate-dependent behavior for determining the longevity of structures manufactured from composite materials.

Cairns, Douglas S.↗
NASA NTRS2000

A 3-D Model Analysis of The Impact of Asian Anthropogenic Emissions on the Sulfur Cycle Over the Pacific Ocean

The impact of anthropogenic activities on the SO2 and sulfate aerosol levels over the Pacific region is examined in the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. We focus on the analysis of the data from the NASA Pacific Exploratory Missions (PEM) over the western North Pacific and the tropical Pacific. These missions include PEM-West A in September-October 1991, when the Asian outflow was at the minimum but the upper atmosphere was heavily influenced by the Pinatubo volcanic eruption, and PEM-West B in March-April 1994 when the Asian outflow was at the maximum, and PEM-Tropics A in August-September at a region relatively free of direct anthropogenic influences. Specifically, we will examine the relative importance of anthropogenic, volcanic and biogenic sources to the SO2 and sulfate concentrations over the Pacific, and quantify the processes controlling the distributions of SO2 and sulfate in both the boundary layer and the free troposphere. We will also assess the global impact of SO2 emission in Asia on the sulfate aerosol loading.

Chin, Mian↗
NASA NTRS2000

A Brief Summary of the Geomorphic Evidence for an Active Surface Hydrologic Cycle in Mars' Past

Because Mars is just over half the Earth's diameter (about 6800 km), it does not exhibit global tectonism on a scale comparable to Earth and Venus. But because it is still a large body compared to Mercury and the moon, it has had an atmosphere and climate over the history of the solar system. This is why Mars has been able to retain surfaces produced both through volcanic and climatic processes that are intermediate in age between volcanic surfaces on the moon and Mercury and both types of surfaces on Venus and Earth. For the purposes of this discussion, this has important implications about the origins and evolution of topographic depressions that potentially may have contained lakes. Tectonism is probably the most important process on Earth for producing closed depressions on the continents, and is clearly responsible for maintenance of the ocean basins through geologic time. This is probably also true for depressions in the highland terrains and lowland plains of Venus. On Mars, however, tectonism appears limited to relatively small amounts of regional extension, compression, and vertical motion largely due to crustal loading of the two major volcanic provinces - Tharsis and Elysium Impact craters and large impact basins (including all or parts of the northern plains) are clearly more important sites for potential lake basins on Mars, though they were likely more important on Earth, and Venus as well, during the period of heavy meteorite bombardment throughout the solar system prior to 3.5 Ga. Comparisons of the relative importance of other formative processes on Mars with those on Earth are less obvious, and some may be quite speculative, since our understanding of the early Martian environment is still rather limited. Additional information is contained in the original extended abstract.

Parker, T. J.↗
NASA NTRS2006

Structural Health Monitoring and Impact Detection Using Neural Networks for Damage Characterization

Detection of damage due to foreign object impact is an important factor in the development of new aerospace vehicles. Acoustic waves generated on impact can be detected using a set of piezoelectric transducers, and the location of impact can be determined by triangulation based on the differences in the arrival time of the waves at each of the sensors. These sensors generate electrical signals in response to mechanical motion resulting from the impact as well as from natural vibrations. Due to electrical noise and mechanical vibration, accurately determining these time differentials can be challenging, and even small measurement inaccuracies can lead to significant errors in the computed damage location. Wavelet transforms are used to analyze the signals at multiple levels of detail, allowing the signals resulting from the impact to be isolated from ambient electromechanical noise. Data extracted from these transformed signals are input to an artificial neural network to aid in identifying the moment of impact from the transformed signals. By distinguishing which of the signal components are resultant from the impact and which are characteristic of noise and normal aerodynamic loads, the time differentials as well as the location of damage can be accurately assessed. The combination of wavelet transformations and neural network processing results in an efficient and accurate approach for passive in-flight detection of foreign object damage.

Ross, Richard W.↗
NASA NTRS2010

Functional Mobility Testing: Quantification of Functionally Utilized Mobility Among Unsuited and Suited Subjects

A novel approach was used in this test for the creation of mobility requirements to be fed into the Human-Systems Integration Requirements and Engineering Requirements Documents. Existing suits may not provide adequate mobility to perform all functional tasks required in future missions. Looking solely at maximum unsuited mobility could be unrealistic and unnecessary to design into a suit. The new approach focused instead on functional range of motion. Setting design requirements based on the mobility necessary to perform a broad spectrum of functional tasks should save resources while still providing a suit capable of performing all tasks that a suited crewmember is likely to encounter. Unsuited functional mobility testing revealed some interesting nuances of human movement including variances in mobility utilized when completing functional tasks as well as the impact of compound joint motions and the influence of joint loading on range of motion. Suited requirements must reflect the fact that altered movement strategies are utilized while wearing a space suit. Improved methods for the creation of space suit design requirements should lead to improved suit performance while maintaining crewmember safety and reducing overall costs.

Scott A. England↗
NASA NTRS2018

Use of Shuttle Heritage Hardware in Space Launch System (SLS) Application-Structural Assessment

NASA is moving forward with the development of the next generation system of human spaceflight to meet the Nation's goals of human space exploration. To meet these goals, NASA is aggressively pursuing the development of an integrated architecture and capabilities for safe crewed and cargo missions beyond low-Earth orbit. Two important tenets critical to the achievement of NASA's strategic objectives are Affordability and Safety. The Space Launch System (SLS) is a heavy-lift launch vehicle being designed/developed to meet these goals. The SLS Block 1 configuration (Figure 1) will be used for the first Exploration Mission (EM-1). It utilizes existing hardware from the Space Shuttle inventory, as much as possible, to save cost and expedite the schedule. SLS Block 1 Elements include the Core Stage, "Heritage" Boosters, Heritage Engines, and the Integrated Spacecraft and Payload Element (ISPE) consisting of the Launch Vehicle Stage Adapter (LVSA), the Multi-Purpose Crew Vehicle (MPCV) Stage Adapter (MSA), and an Interim Cryogenic Propulsion Stage (ICPS) for Earth orbit escape and beyond-Earth orbit in-space propulsive maneuvers. When heritage hardware is used in a new application, it requires a systematic evaluation of its qualification. In addition, there are previously-documented Lessons Learned (Table -1) in this area cautioning the need of a rigorous evaluation in any new application. This paper will exemplify the systematic qualification/assessment efforts made to qualify the application of Heritage Solid Rocket Booster (SRB) hardware in SLS. This paper describes the testing and structural assessment performed to ensure the application is acceptable for intended use without having any adverse impact to Safety. It will further address elements such as Loads, Material Properties and Manufacturing, Testing, Analysis, Failure Criterion and Factor of Safety (FS) considerations made to reach the conclusion and recommendation.

Aggarwal, Pravin↗
NASA NTRSDate not supplied

Effect of Barely Visible Impact Damage on Thermoplastic Welded Structure

Spirit Aerosystems recently conducted screening tests on thermoplastic skin/stringer panels manufactured with Automated Fiber Placement (AFP) and stamp forming which were joined using Spirit’s Co-Fusion process. Skin and stringer gauge were both set to 0.168 cm. The resulting panel design is 48 cm tall, 49 cm wide, and has 3 stringers welded at a 21.5 cm pitch. Barely Visible Impact Damage (BVID) and Residual Compressive Strength were chosen to conduct a damage tolerance study. Zee stringers, made with IM8/PEKK-FC material, were Co-Fusion welded to a T1100/TC1225 skin. Out of these 5 panels, 1 was chosen to be a BVID survey panel, 1 for pristine compressive strength determination, and 3 to be impacted to create BVID followed by testing for residual compressive strength. On the survey panel, impacts ranged in energy from 40J – 65J and dent depth measurements were conducted at 24 hours, 48 hours, and two weeks after impacting. The residual compressive strength panel failed near the predicted load of 214 MPa. For the residual compressive strength panels, BVID was created at two different mid-bay locations: 1) striking the OML coincident with the stringer and 2) striking the skin IML 2.5 cm away from the stringer flange. Pulse Echo Ultrasonic Testing was used to inspect the panels before and after creating BVID.

HiCAM↗
DOE OSTI2023

Computational Fluid Dynamics Study of a Cross-Flow Marine Hydrokinetic Turbine and the Combined Influence of Struts and Helical Blades: Preprint

A computational fluid dynamics study was performed for a cross-flow marine hydro-kinetic turbine. The analysis was done in three dimensions and used the unsteady Reynolds averaged Navier-Stokes solver in the commercial code STAR-CCM+. The base turbine configuration is the RivGen® Turbine, designed by the Ocean Renewable Power Company (ORPC). A convergence and uncertainty analysis was performed for both the spatial and temporal discretization; this was done using the base configuration which features support struts and helical foils. The proposed study aims to compare the impact of the struts on both power performance and blade loading for helical and straight blades.

CFD↗
DOE OSTI2023

1:70-Scale Model Testing of the Reference OpenSource Controller (ROSCO) on the IEA-Wind 15MW Reference Wind Turbine Including Floating Feedback: Preprint

This paper presents results from the Floating Offshore-wind Controls Advanced Laboratory (FOCAL) Experimental campaign performed at the University of Maine's (UMaine's) Harold Alfond Wind/Wave Ocean Engineering Laboratory (W2). The project involves four Froude-scaled test campaigns considering the International Energy Agency (IEA) Wind 15MW Reference Wind Turbine deployed on the VolturnUS-S semi-submersible platform with tuned-mass damper (TMD) elements in the hull. The turbine employs real-time rotor torque and blade pitch control through the Reference OpenSource Controller (ROSCO), including the additional control strategies of ROSCO's thrust peak shaving and a floating feedback control loop. Results with the floating feedback control are considered in this paper and show a significant reduction in platform pitch motion and loads around the platform pitch natural frequency with minimal negative impact of rotor power quality.

controls↗
NASA NTRSDate not supplied

Planning for Validation of Optical Property Degradation Predictions Using On-Orbit Telemetry

NASA’s Gateway Power and Propulsion Element (PPE) will employ high power Xenon Hall thrusters to transit from Earth orbit to a lunar near-rectilinear halo orbit (NRHO). Due to the extended duration of this transit phase and a high thruster duty cycle, there is expected to be significant material erosion caused by the ion plume and subsequent redeposition onto the main spacecraft radiators. While plume modeling and tests of redeposition have attempted to quantify the resulting impact to radiator optical properties, significant uncertainties remain. The flight of PPE presents an opportunity to validate some of the assumptions in this analytical chain, but there will be no specialized hardware that can directly characterize the property changes. However, the planned mission includes periods with significant solar flux to the radiators both early and late in the transit inducing differential heat loads on the vehicle. This presentation will explore options for analyzing possible impacts of various levels of redeposition and whether the severity can be accurately characterized via existing planned telemetry during a nominal mission.

PPE↗
NASA NTRSDate not supplied

Impacts of Cold Ionospheric Ions in Magnetic Reconnection at the Earth’s Magnetopause and Magnetotail

The Earth’s magnetosphere is filled by particles from two sources: the solar wind and the ionosphere. Ionospheric ions are initially cold and contain He+ and O+, in addition to to H+. Depending on their initial magnetic latitude and local time, and the state of the magnetosphere, they may contribute to the plasmasphere, the plasma sheet, the ring current, the warm plasma cloak etc. Depending on which path they follow in the magnetosphere, some of these ionospheric ions remain cold when they reach the two key reconnection regions: the Earth’s magnetopause and the plasma sheet in the tail. In this presentation, we will first review previous statistical works that quantify the number of cold/ionospheric ions near these two regions. Several works have attempted to quantify these populations, but they are inherently difficult to characterize due to their low energy, often below the spacecraft potential. We will also discuss the impacts they have on the magnetic reconnection process. Ionospheric ions mass-load the regions where reconnection takes place and change the characteristic Alfven speed, resulting in a smaller reconnection electric field. They also take a portion of the energy that is imparted to particles, affecting the energy budget of magnetic reconnection. Finally, they introduce new length and time scales, associated to their gyroradius and gyroperiod. We will discuss what are the implications of these impacts for the evolution of the magnetosphere – solar wind interactions.

Sergio Toledo Redondo↗
DOE OSTI2022

A Fast and Scalable Genetic Algorithm-Based Approach for Planning of Microgrids in Distribution Networks: Preprint

As a result of climate change, extreme weather events are occurring more frequently and with increasing impact. This trend poses a significant challenge for distribution utilities and system operators to ensure that there is uninterrupted power supply to critical loads in their networks; thus, the level of proactive preparation of the distribution system to be able to handle severe impacts of extreme weather events represents the system's resilience. One method that distribution systems use to prepare for extreme events is to form multiple microgrids and thereby isolate themselves from the grid supply by using local generation as much as possible to supply critical loads. But partitioning an existing system into multiple feasible islands capable of supporting critical loads is still challenging for distribution systems - first, because of the size of the graph partitioning problem and, second, because of the difficulty in properly formulating the desired attributes of such islands or microgrids. Therefore, this paper presents a genetic algorithmbased approach that facilitates incorporating multiple objectives for grid partitioning by formulating two types of problems - node allocation and edge elimination - and it considers multiple topological and resilience-enhancing objectives. The performance of the proposed genetic algorithm-based approach is numerically evaluated on multiple test systems as well as on a real distribution feeder in Colorado, USA.

edge elimination↗
DOE OSTI2019

In situ visualization of loading-dependent water effects in a stable metal-organic framework

Competitive water adsorption can have a significant impact on metal-organic framework performance properties, ranging from occupying active sites in catalytic reactions to co-adsorbing at the most favourable adsorption sites in gas separation and storage applications. Here, we investigate, for a metal-organic framework that is stable after moisture exposure, what are the reversible, loading-dependent structural changes that occur during water adsorption. Herein, a combination of in situ synchrotron powder and single-crystal diffraction, infrared spectroscopy and molecular modelling analysis was used to understand the important role of loading-dependent water effects in a water stable metal-organic framework. Through this analysis, insights into changes in crystallographic lattice parameters, water siting information and water-induced defect structure as a response to water loading were obtained. This work shows that, even in stable metal-organic frameworks that maintain their porosity and crystallinity after moisture exposure, important molecular-level structural changes can still occur during water adsorption due to guest-host interactions such as water-induced bond rearrangements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

On the Impact of High-Order Harmonic Generation in Electrical Distribution Systems

The modern power grid has seen a rise in the integration of non-linear loads, presenting a significant concern for operators. These loads introduce unwanted harmonics, leading to potential issues such as overheating and improper functioning of circuit breakers. In pursuing a more sustainable grid, the adoption of electric vehicles (EVs) and photovoltaic (PV) systems in residential networks has increased. Understanding and examining the effects of high-order harmonic frequencies beyond $1.5$ kHz is crucial to understanding their impact on the operation and planning of electrical distribution systems under varying nonlinear loading conditions. This study investigates a diverse set of critical power electronic loads within a household modeled using PSCAD/EMTdc, analyzing their unique harmonic spectra. This information is utilized to run the time-series harmonic analysis program in OpenDSS on a modified IEEE 34 bus test system model. The impact of high-order harmonics is quantified using metrics that evaluate total harmonic distortion (THD), transformer harmonic-driven eddy current loss component, and propagation of harmonics from the source to the substation transformer.

Peerzada, Aaqib A. [BATTELLE (PACIFIC NW LAB)]↗
NASA NTRS1990

Compression behavior of graphite-epoxy and graphite-thermoplastic panels with circular holes or impact damage

An experimental investigation of the compression behavior of laminated specimens made from graphite-epoxy tape (AS4-3502), graphite-thermoplastic tape (AS4-PEEK), and graphite-thermoplastic fabric (AS4-PEEK) was conducted. Specimens with five different stacking sequences were loaded to failure in uniaxial compression. Some of the specimens had central circular holes with diameters up to 65 percent of the specimen width. Other specimens were subjected to low speed impact with impact energy up to 30 J prior to compressive loading. This investigation indicates that graphite-thermoplastic specimens with holes have up to 15 percent lower failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and hole size. However, graphite-thermoplastic specimens subjected to low speed impact have up to 15 percent higher failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and impact energy. Compression tests of graphite-thermoplastic specimens constructed of unidirectional tape and of fabric indicate that the material form has little effect on failure strains in specimens with holes or low speed impact damage.

Jegley, Dawn C.↗
NASA NTRS2004

Multi-Terrain Impact Testing and Simulation of a Composite Energy Absorbing Fuselage Section

Comparisons of the impact performance of a 5-ft diameter crashworthy composite fuselage section were investigated for hard surface, soft soil, and water impacts. The fuselage concept, which was originally designed for impacts onto a hard surface only, consisted of a stiff upper cabin, load bearing floor, and an energy absorbing subfloor. Vertical drop tests were performed at 25-ft/s onto concrete, soft-soil, and water at NASA Langley Research Center. Comparisons of the peak acceleration values, pulse durations, and onset rates were evaluated for each test at specific locations on the fuselage. In addition to comparisons of the experimental results, dynamic finite element models were developed to simulate each impact condition. Once validated, these models can be used to evaluate the dynamic behavior of subfloor components for improved crash protection for hard surface, soft soil, and water impacts.

Fasanella, Edwin L.↗