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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Cytogenetic studies of blood, experiment M111

Analysis of the chromosome patterns of Skylab crewmen preflight and postflight recorded two types of defects: minor structural defects including chromatid breaks, chromosome breaks, deletions, and fragments were not significantly increased; structural rearrangements including dicentrics, exchange figures, inversions, and translocations occured more frequently. Data indicate that the flight itself in Skylab missions was not a contributing factor to these abberrations.

Lockhart, L. H.↗
NASA NTRS1979

AXAF optical technology analysis

A grazing incidence telescope with six nested subsystems is investigated through the effects of misalignment and surface deformations on it's image quality. The axial rms-spot size serves as measure for the image quality. The surface deformations are simulated by ellipsoidal and sinusoidal deviation elements. Each type of defect is analyzed in the single two-element system. The full nested system is then analyzed in the presence of all possible defects on all twelve elements, whereby the magnitude of the defects is randomized within a given upper limit.

Korsch, D.↗
NASA NTRS1980

Simultaneous radiation damage and annealing of GaAs solar cells

In this report, concepts and equations are developed to describe the simultaneous radiation damage and annealing of solar cells. The annealing characteristics of three types of defects are employed to study three examples of continuous irradiation and annealing. One example shows that the effective damage could be reduced by a factor of fifty. The difficulty of a laboratory experiment properly simulating the effects in space are discussed. Potential advantages of continuous annealing such as reduction of stable defect formation and omission of radiation cover glasses are presented.

Heinbockel, J. H.↗
NASA NTRS1991

Annealing characteristics of irradiated hydrogenated amorphous silicon solar cells

It was shown that 1 MeV proton irradiation with fluences of 1.25E14 and 1.25E15/sq cm reduces the normalized I(sub SC) of a-Si:H solar cell. Solar cells recently fabricated showed superior radiation tolerance compared with cells fabricated four years ago; the improvement is probably due to the fact that the new cells are thinner and fabricated from improved materials. Room temperature annealing was observed for the first time in both new and old cells. New cells anneal at a faster rate than old cells for the same fluence. From the annealing work it is apparent that there are at least two types of defects and/or annealing mechanisms. One cell had improved I-V characteristics following irradiation as compared to the virgin cell. The work shows that the photothermal deflection spectroscopy (PDS) and annealing measurements may be used to predict the qualitative behavior of a-Si:H solar cells. It was anticipated that the modeling work will quantitatively link thin film measurements with solar cell properties. Quantitative predictions of the operation of a-Si:H solar cells in a space environment will require a knowledge of the defect creation mechanisms, defect structures, role of defects on degradation, and defect passivation and annealing mechanisms. The engineering data and knowledge base for justifying space flight testing of a-Si:H alloy based solar cells is being developed.

Payson, J. S.↗
NASA NTRS2004

X-ray Microscopic Characterization of Protein Crystals

The microscopic mapping of the variation in degree of perfection and in type of defects in entire protein crystals by x-rays may well be a prerequisite for better understanding causes of lattice imperfections, the growth history, and properties of protein crystals. However, x-ray microscopic characterization of bulk protein crystals, in the as-grown state, is frequently more challenging than that of small molecular crystals due to the experimental difficulties arising largely from the unique features possessed by protein crystals. In this presentation, we will illustrate ssme recent activities in employing coherence-based phase contrast x-ray imaging and high-angular-resolution diffraction techniques for mapping microdefects and the degree of perfection of protein crystals, and demonstrate a correlation between crystal perfection, diffraction phenomena., and crystallization conditions. The observed features and phenomena will be discussed in context to gain insight into the nature of defects, nucleation and growth, and the properties of protein crystals.

Hu, Z. W.↗
NASA NTRS2004

"GSFC FSB Application of Perspective-Based Inspections"

The scope of work described in our proposal consisted of developing inspection standards targeted to Branch-specific types of defects (gained from analysis of Branch project defect histories), and including Branch-relevant perspectives and questions to guide defect detection. The tailored inspection guidelines were to be applied on real Branch projects with support as needed from the technology infusion team. This still accurately describes the scope of work performed. It was originally proposed that the Perspective-Based inspection standard would be applied on three projects within the Branch: GPM, JWST, and SDO. Rather than apply the proposed standard to all three, we inserted a new step, in which the standard was instead applied on a single pilot project, cFE (described above). This decision was a good match for the Branch goals since, due to the "design for reuse" nature of cFE, inspections played an even more crucial than usual role in that development process. Also, since cFE is being designed to provide general-purpose functionality, key representatives fiom our target projects were involved in inspections of cFE to provide perspectives from different missions. In this way, they could get some exposure to and the chance to provide feedback on the proposed standards before applying them on their own projects. The Branch-baselined standards will still be applied on GPM, JWST, and SDO, although outside the time frame of this funding. Finally, we originally proposed using the analysis of Branch defect sources to indicate in which phases Perspective-Based inspections could provide the best potential for future improvement, although experience on previous Branch projects suggested that our efforts would likely be focused on requirements and code inspections. In the actual work, we focused exclusively on requirements inspections, as this was the highest-priority work currently being done on our cFE pilot project.

Shell, Elaine↗
NASA NTRS2006

Nondestructive Evaluation of Foam Insulation on the Space Shuttle External Tank

Foam loss on the External Tank (ET) during launch can be caused by a number of factors. Voids are the best understood mechanism of foam loss, although it is known that delaminations, cracks and crushed foam can also lead to liberation of foam. Shortly after the Columbia accident, work began on non-destructive evaluation of foam targeted at finding voids and delaminations. After several months of searching for candidate methods capable of inspecting ET foam, the five most promising techniques were taken through a blind test and narrowed down to two methods to develop and use for inspection of the ET. These methods were backscatter radiography and terahertz imaging. The backscatter radiography system measures a test part by detecting Compton backscattered x-ray energy generated by a collimated beam of x-rays directed at the test subject. This collimated beam is scanned across the subject, recording scatter intensity data one pixel at a time until the area of interest is covered. The resulting data can be used to generate an image similar to a radiograph. Some depth information can be gathered utilizing apertures or collimation on the detectors. The detectors are located around the collimated source, making this a single sided inspection. The void detection limit with the currently utilized system is around 0.5 inches in diameter by 0.2 inches high. The terahertz imaging system inspects a test part by utilizing a transceiver to emit a pulse focused at the aluminum skin of the ET, which reflects it back to the transceiver where it is analyzed. The transceiver is scanned across the area of interest until a measurement has been taken at every location. Amplitude, time delay and frequency content are examined to note any discontinuities which may be the result of a void or other type of defect. The pulse currently utilized is in the millimeter wave regime. The void detection limit with this system is around 0.5 inches in diameter by 0.2 inches high. With increased interest in other causes of foam loss following the flight of Discovery in July 2005, laser shearography was added to the techniques used for inspecting ET foam. The shearography method records a sheared image of a laser speckle pattern projected on a test part before And after some sort of excitation. The resultant fringe pattern allows the slope of the out of plane displacement to be measured. For crushed and delaminated foam applications, a non-contact air coupled acoustic force is used to excite the surface of the foam. Regions without defects tend to respond differently to the sound energy than do regions with defects, generating a map of the foam integrity. Foam crushed to a depth of about 0.1 inches is detectable with shearography even after it has relaxed to its original shape.

Richter, Joel↗
NASA NTRS2011

Software Testing and Verification in Climate Model Development

Over the past 30 years most climate models have grown from relatively simple representations of a few atmospheric processes to a complex multi-disciplinary system. Computer infrastructure over that period has gone from punch card mainframes to modem parallel clusters. Model implementations have become complex, brittle, and increasingly difficult to extend and maintain. Existing verification processes for model implementations rely almost exclusively upon some combination of detailed analysis of output from full climate simulations and system-level regression tests. In additional to being quite costly in terms of developer time and computing resources, these testing methodologies are limited in terms of the types of defects that can be detected, isolated and diagnosed. Mitigating these weaknesses of coarse-grained testing with finer-grained "unit" tests has been perceived as cumbersome and counter-productive. In the commercial software sector, recent advances in tools and methodology have led to a renaissance for systematic fine-grained testing. We discuss the availability of analogous tools for scientific software and examine benefits that similar testing methodologies could bring to climate modeling software. We describe the unique challenges faced when testing complex numerical algorithms and suggest techniques to minimize and/or eliminate the difficulties.

Clune, Thomas L.↗
NASA NTRS2004

Fracture Analysis of Semi-Elliptical Surface Cracks in Ductile Materials

Accurate life assessment of structural components may require advanced life prediction criteria and methodologies. Structural components often exhibit several different types of defects, among the most prevalent being surface cracks. A semi-elliptical surface crack subjected to monotonic loading will exhibit stable crack growth until the crack has reached a critical size, at which the crack loses stability and fracture ensues (Newman, 2000). The shape and geometry of the flaw are among the most influential factors. When considering simpler crack configurations, such as a through-the-thickness crack, a three-dimensional (3D) geometry may be modeled under the approximation of two-dimensional (2D) plane stress or plane strain. The more complex surface crack is typically modeled numerically with the Finite Element Method (FEM). A semi-elliptical surface crack is illustrated in Figure 1-1.

Daniewicz, S. R.↗
DOE OSTI2025

Cluster Dynamics Modeling Needs for the Advanced Materials and Manufacturing Technologies Program

This milestone report aims to identify and assess the cluster dynamics (CD) modeling requirements within the Department of Energy's Office of Nuclear Energy (DOE-NE) Advanced Materials and Manufacturing Technologies (AMMT) program and to communicate these needs to the DOE-NE Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. The goal is to ensure NEAMS is well-informed about the CD modeling requirements to support AMMT's mission of accelerating the development, qualification, demonstration, and deployment of advanced structural materials and manufacturing for nuclear energy applications. CD modeling is an essential tool for predicting the degradation of structural materials under irradiation, which is a key component of AMMT's accelerated qualification process. The AMMT program focuses on both additively manufactured and wrought structural alloys, such as laser powder-bed fusion 316H austenitic stainless steel, alloy 709, Haynes 244, and alloy 617. These materials require a generalized CD modeling framework to facilitate rapid model development and computational simulation. A flexible, generalized CD software, similar to the Multiphysics Object-Oriented Simulation Environment (MOOSE) finite element framework, would enable modeling of various cluster types, including defect clusters, defect-solute clusters, and multicomponent clusters, incorporating thermodynamics and kinetics parameters. Radiation effects, microstructural feature evolution, and multi-dimensional modeling are critical considerations for the CD model. The usability of the CD code should allow for easy modification and coupling with MOOSE-based simulations. Additionally, the software should adhere to Nuclear Quality Assurance-1 standards, include a testing suite for verification and validation, and be version-controlled within a national laboratory-managed Git repository. Benchmark problems are needed to assess code predictions and performance.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2015

Detection of CFRP Composite Manufacturing Defects Using a Guided Wave Approach

NASA Langley Research Center is investigating a guided-wave based defect detection technique for as-fabricated carbon fiber reinforced polymer (CFRP) composites. This technique will be extended to perform in-process cure monitoring, defect detection and size determination, and ultimately a closed-loop process control to maximize composite part quality and consistency. The overall objective of this work is to determine the capability and limitations of the proposed defect detection technique, as well as the number and types of sensors needed to identify the size, type, and location of the predominant types of manufacturing defects associated with laminate layup and cure. This includes, porosity, gaps, overlaps, through-the-thickness fiber waviness, and in-plane fiber waviness. The present study focuses on detection of the porosity formed from variations in the matrix curing process, and on local overlaps intentionally introduced during layup of the prepreg. By terminating the cycle prematurely, three 24-ply unidirectional composite panels were manufactured such that each subsequent panel had a higher final degree of cure, and lower level of porosity. It was demonstrated that the group velocity, normal to the fiber direction, of a guided wave mode increased by 5.52 percent from the first panel to the second panel and 1.26 percent from the second panel to the third panel. Therefore, group velocity was utilized as a metric for degree of cure and porosity measurements. A fully non-contact guided wave hybrid system composed of an air-coupled transducer and a laser Doppler vibrometer (LDV) was used for the detection and size determination of an overlap By transforming the plate response from the time-space domain to the frequency-wavenumber domain, the total wavefield was then separated into the incident and backscatter waves. The overlap region was accurately imaged by using a zero-lag cross-correlation (ZLCC) imaging condition, implying the incident and backscattered waves are in phase over the overlap boundaries.

Hudson, Tyler B.↗
DOE OSTI2025

Toward Quality Control in Perovskite Solar Cell Fabrication: Spot-Like Processing Defects Disrupt Charge Transport Layers and Promote Ag Metal Electrode Intrusion

Metal halide perovskite (MHP) photovoltaics provide high efficiencies with less stringent processing requirements than traditional photovoltaic materials. However, processing related defects must be suppressed as they can lead to decreases in initial device efficiency and potentially compromise long-term device operation. In this work we investigate morphological defects in MHP devices using luminescence imaging followed by in-depth structural and composition analysis using electron microscopy-based methods. We identify several different classes of spot-like processing-related defects and observe that a single device structure may contain multiple types of these defects. The presence of these defects in devices with different layer structures and absorber chemistries makes them relevant to the perovskite photovoltaic community as a whole. The defects are associated with voids in the perovskite layer, inclusions (glass, migrated Ag, dust), thickness variations, hole transport layer disruption with anomalous crystal growth, and electron transport layer disruptions that could allow Ag intrusion and lead to local shunts. As perovskite photovoltaic technology matures, mitigation of such defects is critical to improving not only initial performance but also the long-term stability required for industrial applications.

14 SOLAR ENERGY↗
NASA NTRS1997

Lithium-ion drifting: Application to the study of point defects in floating-zone silicon

The use of lithium-ion (Li(+)) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li(+) drift technique is used to detect the presence of vacancy-related defects (D defects) in certain p-type FZ silicon crystals. SUPREM-IV modeling suggests that the silicon point defect diffusivities are considerably higher than those commonly accepted, but are in reasonable agreement with values recently proposed. These results demonstrate the utility of Li(+) drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li(+) compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.

Silicon↗
DOE OSTI2025

Near-Infrared Emission from Sulfur Heteroatom Defects in Single-Walled Carbon Nanotubes

Quantum defects introduced into single-walled carbon nanotubes (SWCNTs) that support near-infrared emission are promising candidates for many applications. Here, we present a type of quantum defect in which sulfur atoms are incorporated into the crystal lattice of SWCNTs through their reactions with a mild reducing agent, sodium dithionite. When radical anions generated by sodium dithionites react with (6,5)-SWCNTs, two new emission features emerge at 1120 and 1250 nm. Comparing these spectral features with density functional theory calculation results, we attribute them to defects with episulfide or thioether structures. Here, by investigating the influences of reaction conditions including reactant concentration, light irradiation, and solvent type, we identify the reaction mechanism between SWCNTs and sodium dithionite and achieve good control over defect densities. Due to the intrinsic reactivity of sulfur species, the sulfur-containing quantum defects discovered here may facilitate the introduction of more complex and functionally diverse moieties into SWCNTs.

Anions↗
NASA NTRS1981

Flaw criticality of circular disbond defects in compressive laminates

The compressive behavior of T300/5208 graphite-epoxy laminates containing circular delaminations was studied to determine the flaw criticality of two types of implanted defect, Kapton bag and Teflon film, on several laminate configurations. Defect size was varied. Results, presented in the form of residual strength curves, indicate that the Teflon film defect reduced strength more than the Kapton bad defect in 12-ply samples, but that two laminates (+ or - 45) sub 2s and (90/+ or - 45) sub s were insensitive to any implanted defect. A clear thickness effect was shown to exist for the (o/+ pr 45) sub ns laminate and was attributed to failure mode transition. The analytically predicted buckling loads show excellent agreement with experimental results and are useful in predicting failure mode transition.

Webster, J. D.↗