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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Method and apparatus for testing surface characteristics of a material

A method, apparatus and system for testing characteristics of a material sample is provided. The system includes an apparatus configured to house the material test sample while defining a sealed volume against a surface of the material test sample. A source of pressurized fluid is in communication with, and configured to pressurize, the sealed volume. A load applying apparatus is configured to apply a defined load to the material sample while the sealed volume is monitored for leakage of the pressurized fluid. Thus, the inducement of surface defects such as microcracking and crazing may be detected and their effects analyzed for a given material. The material test samples may include laminar structures formed of, for example, carbon cloth phenolic, glass cloth phenolic, silica cloth phenolic materials or carbon-carbon materials. In one embodiment the system may be configured to analyze the material test sample while an across-ply loading is applied thereto.

Johnson, David L.↗
NASA NTRS1987

Fault Detection and Isolation for Hydraulic Control

Pressure sensors and isolation valves act to shut down defective servochannel. Redundant hydraulic system indirectly senses failure in any of its electrical control channels and mechanically isolates hydraulic channel controlled by faulty electrical channel so flat it cannot participate in operating system. With failure-detection and isolation technique, system can sustains two failed channels and still functions at full performance levels. Scheme useful on aircraft or other systems with hydraulic servovalves where failure cannot be tolerated.

Source record↗
NASA NTRS1977

Applications of thermal infrared imagery for energy conservation and environmental surveys

The survey procedures, developed during the winter and summer of 1976, employ color and color infrared aerial photography, thermal infrared imagery, and a handheld infrared imaging device. The resulting imagery was used to detect building heat losses, deteriorated insulation in built-up type building roofs, and defective underground steam lines. The handheld thermal infrared device, used in conjunction with the aerial thermal infrared imagery, provided a method for detecting and locating those roof areas that were underlain with wet insulation. In addition, the handheld infrared device was employed to conduct a survey of a U.S. Army installation's electrical distribution system under full operating loads. This survey proved to be cost effective procedure for detecting faulty electrical insulators and connections that if allowed to persist could have resulted in both safety hazards and loss in production.

Carney, J. R.↗
NASA NTRS2001

Phase sensitive x-ray diffraction imaging of defects in biological macromolecular crystals

Conventional x-ray diffraction topography is currently used to map defects in the bulk of protein crystals, but the lack of sufficient contrast is frequently a limiting factor. We experimentally demonstrate that this barrier can be circumvented using a method that combines phase sensitive and diffraction imaging principles. Details of defects revealed in tetragonal lysozyme and cubic ferritin crystals are presented and discussed. The approach enabling the detection of the phase changes of diffracted x rays should prove to be useful in the study of defect structures in a broad range of biological macromolecular crystals.

Muramidase/chemistry↗
NASA NTRS1973

Electron-beam studies of Schottky-barrier detector surfaces

Review of the surface anomalies occurring in Schottky-barrier particle detectors identifiable by means of an electron beam technique employed by Czaja (1965) for analyzing defects in diode structures. The technique is shown to make possible the detection and identification of the following anomalies: (1) chemical contamination of the detector surface; (2) mechanical damage of the wafer substrates; (3) damage introduced in semiconductor surface preparation; (4) radiation damage; and (5) defective surface metallization.

Peckerar, M. C.↗
NASA NTRS1990

Milder Etchant For Penetrant Inspection

New etching solution for chemical penetrant inspection of Inconel(R) 718 castings and weldments. Etchant does not introduce artifacts mistaken for defects. Applied by swabbing or by immersion. Used to detect unwanted residues of Nioro(R) (or equivalent) gold brazing alloy on type 347 stainless steel.

O'Tousa, Joseph E.↗
NASA NTRS1990

Dissociation and recombination of positive holes in minerals

The formation mechanisms are described of positive holes - electronic defects in the O2 sublattice - with attention given to detecting the positive surface charge of minerals with these holes. Charge distribution analysis (CDA) is presented which measures dielectric polarization in an inhomogeneous field. CDA can be applied to the detection of the peroxide/superoxide functionality caused by positive holes on the surface. It is demonstrated with obsidian that the measurements provide data on O(-) mobility as a function of surface-charge carrier density and on O(-) generation as a function of temperature.

Freund, Friedemann↗
NASA NTRS2002

Towards Comprehensive Variation Models for Designing Vehicle Monitoring Systems

When designing vehicle vibration monitoring systems for aerospace devices, it is common to use well-established models of vibration features to determine whether failures or defects exist. Most of the algorithms used for failure detection rely on these models to detect significant changes in a flight environment. In actual practice, however, most vehicle vibration monitoring systems are corrupted by high rates of false alarms and missed detections. This crucial roadblock makes their implementation in real vehicles (e.g., helicopter transmissions and aircraft engines) difficult, making their operation costly and unreliable. Research conducted at the NASA Ames Research Center has determined that a major reason for the high rates of false alarms and missed detections is the numerous sources of statistical variations that are not taken into account in the modeling assumptions. In this paper, we address one such source of variations, namely, those caused during the design and manufacturing of rotating machinery components that make up aerospace systems. We present a novel way of modeling the vibration response by including design variations via probabilistic methods. Using such models, we develop a methodology to account for design and manufacturing variations, and explore the changes in the vibration response to determine its stochastic nature. We explore the potential of the methodology using a nonlinear cam-follower model, where the spring stiffness values are assumed to follow a normal distribution. The results demonstrate initial feasibility of the method, showing great promise in developing a general methodology for designing more accurate aerospace vehicle monitoring systems.

McAdams, Daniel A.↗
NASA NTRS2001

Toward Failure Modeling In Complex Dynamic Systems: Impact of Design and Manufacturing Variations

When designing vehicle vibration monitoring systems for aerospace devices, it is common to use well-established models of vibration features to determine whether failures or defects exist. Most of the algorithms used for failure detection rely on these models to detect significant changes during a flight environment. In actual practice, however, most vehicle vibration monitoring systems are corrupted by high rates of false alarms and missed detections. Research conducted at the NASA Ames Research Center has determined that a major reason for the high rates of false alarms and missed detections is the numerous sources of statistical variations that are not taken into account in the. modeling assumptions. In this paper, we address one such source of variations, namely, those caused during the design and manufacturing of rotating machinery components that make up aerospace systems. We present a novel way of modeling the vibration response by including design variations via probabilistic methods. The results demonstrate initial feasibility of the method, showing great promise in developing a general methodology for designing more accurate aerospace vehicle vibration monitoring systems.

Tumer, Irem Y.↗
NASA NTRS2002

Functional Characterization of G12, a Gene Required for Mitotic Progression during Gastrulation in Zebrafish

In a differential RNA display screen we have isolated a zebrafish gene, G12, for which homologs can only be found in DNA databases for vertebrates, but not invertebrates. This suggests that this is a gene required specifically in vertebrates. G12 expression is upregulated at mid-blastula transition (MBT). Morpholino inactivation of this gene by injection into 1-cell embryos results in mitotic defects and apoptosis shortly after MBT. Nuclei in morpholino treated embryos also display segregation defects. We have characterized the localization of this gene as a GFP fusion in live and fixed embryos. Overexpression of G12-GFP is non-toxic. Animals retain GFP expression for at least 7 days with no developmental defects, Interestingly in these animals G12-GFP is never detectable in blood cells though blood is present. In the deep cells of early embryos, G 12GFP is localized to nuclei and cytoskeletal elements in interphase and to the centrosome and spindle apparatus during mitosis. In the EVL, G12-GFP shows additional localization to the cell periphery, especially in mitosis. In the yolk syncytium, G12-GFP again localizes to nuclei and strongly to cytoplasmic microtubules of migrating nuclei at the YSL margin. Morpholinc, injection specifically into the YSL after cellularization blocks epiboly and nuclei of the YSL show mitotic defects while deep cells show no mitotic defects and continue to divide. Rescue experiments in which morpholino and G12-GFP RNA are co-injected indicate partial rescue by the G12-GFP. The rescue is cell autonomous; that is, regions of the embryo with higher G12-GFP expression show fewer mitotic defects. Spot 14, the human bomolog of G12, has been shown to be amplified in aggressive breast tumors. This finding, along with our functional and morphological data suggest that G12 and spot 14 are vertebrate-specific and may function either as mitotic checkpoints or as structural components of the spindle apparatus.

Reinsch, Sigrid↗
NASA NTRS2003

Fatigue Crack and Porosity Measurement in Composite Materials by Thermographic and Ultrasonic Methods

Contents include the following: 1. Purpose. Detect thermo-mechanically induced intra-ply fatigue microcracking and manufactured porosity in unlined composite pressure vessels. 2. Defect descriptions. Porosity, microcracking. 3. Thermography. Overview of technique. Strengths and Weaknesses. Examples of its use for porosity detection. 4. Resonant ultrasound spectroscopy. Overview of technique. Strengths and Weaknesses. Examples of its use for microcracking detection. Conclusions.

Walker, James L.↗
NASA NTRS1976

Apollo experience report: Detection and minimization of ignition hazards from water/glycol contamination of silver-clad electrical circuitry

The potential flammability hazard when a water/glycol solution contacts defectively insulated silver-clad copper circuitry or electrical components carrying a direct current is described. The chemical reactions and means for detecting them are explained. Methods for detecting and cleaning contaminated areas and the use of inhibitors to arrest chemical reactivity are also explained. Preventive measures to minimize hazards are given. Photomicrographs of the chemical reactions occurring on silver clad wires are also included.

Downs, W. R.↗
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 NTRS1971

Behavior of lithium in irradiated solar cells.

The current state of the art in radiation resistant lithium-doped silicon solar cells is reviewed. Fabrication techniques are reviewed. Characteristics of lithium-doped cells are discussed. Behavior of lithium-doped cells during 1 MeV electron irradiation are studied for various types of cells. Effects of variations in lithium and oxygen concentration are shown and discussed. Capacitance measurements at various voltages, frequencies and temperatures are used to detect charges in lithium donor concentration and the formation of defects during irradiation. Physical models to explain the observed effects are presented.

Carter, J. R., Jr.↗
NASA NTRS2012

Thermography Inspection for Early Detection of Composite Damage in Structures During Fatigue Loading

Advanced composite structures are commonly tested under controlled loading. Understanding the initiation and progression of composite damage under load is critical for validating design concepts and structural analysis tools. Thermal nondestructive evaluation (NDE) is used to detect and characterize damage in composite structures during fatigue loading. A difference image processing algorithm is demonstrated to enhance damage detection and characterization by removing thermal variations not associated with defects. In addition, a one-dimensional multilayered thermal model is used to characterize damage. Lastly, the thermography results are compared to other inspections such as non-immersion ultrasonic inspections and computed tomography X-ray.

Zalameda, Joseph N.↗
NASA NTRS2024

Substrate Matters: Ionic Silver Alters Lettuce Growth, Nutrient Uptake, and Root Microbiome in a Hydroponics System

Ionic silver (Ag+) is being investigated as a residual biocide for use in NASA spacecraft potable water systems on future crewed missions. This water will be used to irrigate future spaceflight crop production systems. We have evaluated the impact of three concentrations (31 ppb, 125 ppb, and 500 ppb) of ionic silver biocide solutions on lettuce in an arcillite (calcinated clay particle substrate) and hydroponic (substrate-less) growth setup after 28 days. Lettuce plant growth was reduced in the hydroponic samples treated with 31 ppb silver and severely stunted for samples treated at 125 ppb and 500 ppb silver. No growth defects were observed in arcillite-grown lettuce. Silver was detectable in the hydroponic-grown lettuce leaves at each concentration but was not detected in the arcillite-grown lettuce leaves. Specifically, when 125 ppb silver water was applied to a hydroponics tray, Ag+ was detected at an average amount of 7 μg/g (dry weight) in lettuce leaves. The increase in Ag+ corresponded with a decrease in several essential elements in the lettuce tissue (Ca, K, P, S). In the arcillite growth setup, silver did not impact the plant root zone microbiome in terms of alpha diversity and relative abundance between treatments and control. However, with increasing silver concentration, the alpha diversity increased in lettuce root samples and in the water from the hydroponics tray samples. The genera in the hydroponic root and water samples were similar across the silver concentrations but displayed different relative abundances. This suggests that ionic silver was acting as a selective pressure for the microbes that colonize the hydroponic water. The surviving microbes likely utilized exudates from the stunted plant roots as a carbon source. Analysis of the root-associated microbiomes in response to silver showed enrichment of metagenomic pathways associated with alternate carbon source utilization, fatty-acid synthesis, and the ppGpp (guanosine 3′-diphosphate 5′-diphosphate) stringent response global regulatory system that operates under conditions of environmental stress. Nutrient solutions containing Ag+ in concentrations greater than 31 ppb in hydroponic systems lacking cation-exchange capacity can severely impact crop production due to stunting of plant growth.

lettuce↗
NASA NTRS2014

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

dielectric polarization↗