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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Noise generation by a lifting wing/flap combination at Reynolds numbers to 2.8 x 10 to the 6th

Measurements relating to the noise source location and intensity within various frequency bands were made for an 0.75 m-chord wing/flap model installed in the Ames 7 x 10-foot wind tunnel. A directional microphone system, located outside the open-wall tunnel was scanned in a two-dimensional array of aiming points about the positive-pressure side of the model to determine the principal locations of noise production, and the intensity of each of these. It was found for the case of the flaps being differentially deflected (0 deg, 35 deg) at the half-span station that noise production was concentrated in the immediate region of the resultant surface discontinuity. For equal deflection of the halves (0 deg, 0 deg or 35 deg, 35 deg), noise was produced uniformly along the length of the gap between the wing and the flap. Simulated flap-mounting brackets generated considerable noise in certain cases, but reduced the noise in others. Trailing edge noise did not appear to be important in comparison with other sources.

Kendall, J. M.↗
NASA NTRS1988

Development and applications of optical interferometric micrometrology in the angstrom and subangstrom range

The recent development of the scanning electron tunneling microscope and the atomic force microscope requires absolute standards for measurements in the angstrom and subangstrom range. Optical interferometry with lasers and multiple mode laser resonances can provide absolute measurements as the laser wavelengths are very accurately known. A key feature of such measurements is the use of piezoelectric crystals as translators of the highest accuracy for very small disturbances. However, the dimensional changes of these crystals resulting from electrical potential changes depend on many variables, among them the method of mounting, so that accurate calibrations are necessary. Starting from advances in optical metrology made by physicists trying to find gravity waves, advances which led to measurements down to 10 to the -5 A, the author designed and built a much simpler system for the angstrom range. The major limiting factors were mechanical vibrations, air currents, thermal changes and laser instabilities.

Lauer, James L.↗
NASA NTRS1993

Nested Fullerenes on Graphite

A novel method of forming nested fullerenes by irradiation of carbon soot using the high energy beam in a 300-kV electron microscope.

fullerenes↗
NASA NTRS2012

Wind Tunnel Testing of a One-Dimensional Laser Beam Scanning and Laser Sheet Approach to Shock Sensing

A 15- by 15-cm supersonic wind tunnel application of a one-dimensional laser beam scanning approach to shock sensing is presented. The measurement system design allowed easy switching between a focused beam and a laser sheet mode for comparison purposes. The scanning results were compared to images from the tunnel Schlieren imaging system. The tests revealed detectable changes in the laser beam in the presence of shocks. The results lend support to the use of the one-dimensional scanning beam approach for detecting and locating shocks in a flow, but some issues must be addressed in regards to noise and other limitations of the system.

Tokars, Roger↗
DOE OSTI2025

Strong-coupling quantum dot microscope

Here, we report the development and fabrication of a novel cryogenic instrument, a scanning quantum dot microscope (SQDM), capable of positioning a quantum dot to within tunneling range of a sample surface. The microscope is strong-coupling in the sense that electron wavefunctions in the quantum dot can directly overlap with electron wavefunctions in the sample, in contrast to probes based on electric-field coupling. The SQDM consists of a sharp glass probe with two asymmetric electrodes leading to an aluminum quantum dot at the apex. One electrode is capacitively coupled to the quantum dot, while the other lead is connected to the dot via a tunneling junction. A charge sensing circuit constructed from a high-electron-mobility transistor is attached to the capacitance lead to measure the charge state of the dot. The last key feature of the design is a tilted-apex geometry. This design feature, in conjunction with the capacitive sensing scheme, results in a robust quantum-dot probe capable of operating within angstrom distances of the sample surface while protecting the single tunnel junction responsible for electron transport onto the quantum dot. We demonstrate that our instrument can detect single-electron tunneling events and can also be operated as a standard scanning tunneling microscope capable of nanometer-scale resolution of the surface topography.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1992

Lunar resources: Oxygen from rocks and soil

The first set of hydrogen reduction experiments to use actual lunar material was recently completed. The sample, 70035, is a coarse-grained vesicular basalt containing 18.46 wt. percent FeO and 12.97 wt. percent TiO2. The mineralogy includes pyroxene, ilmenite, plagioclase, and minor olivine. The sample was crushed to a grain size of less than 500 microns. The crushed basalt was reduced with hydrogen in seven tests at temperatures of 900-1050 C and pressures of 1-10 atm for 30-60 minutes. A capacitance probe, measuring the dew point of the gas stream, was used to follow reaction progress. Experiments were also conducted using a terrestrial basalt similar to some lunar mare samples. Minnesota Lunar Simulant (MLS-1) contains 13.29 wt. percent FeO, 2.96 wt. percent Fe2O3, and 6.56 wt. percent TiO2. The major minerals include plagioclase, pyroxene, olivine, ilmenite, and magnetite. The rock was ground and seived, and experiments were run on the less than 74- and 500-1168-micron fractions. Experiments were also conducted on less than 74-micron powders of olivine, pyroxene, synthetic ilmenite, and TiO2. The terrestrial rock and mineral samples were reduced with flowing hydrogen at 1100 C in a microbalance furnace, with reaction progress monitored by weight loss. Experiments were run at atmospheric pressure for durations of 3-4 hr. Solid samples from both sets of experiments were analyzed by Mossbauer spectroscopy, petrographic microscopy, scanning electron microscopy, tunneling electron microscopy, and x-ray diffraction. Apollo 17 soil 78221 was examined for evidence of natural reduction in the lunar environment. This sample was chosen based on its high maturity level (I sub s/FeO = 93.0). The FeO content is 11.68 wt. percent and the TiO2 content is 3.84 wt. percent. A polished thin section of the 90-150 micron size fraction was analyzed by petrographic microscopy and scanning electron microscopy.

Allen, C. C.↗
NASA NTRS1993

Application of a neural network as a potential aid in predicting NTF pump failure

The National Transonic Facility has three centrifugal multi-stage pumps to supply liquid nitrogen to the wind tunnel. Pump reliability is critical to facility operation and test capability. A highly desirable goal is to be able to detect a pump rotating component problem as early as possible during normal operation and avoid serious damage to other pump components. If a problem is detected before serious damage occurs, the repair cost and downtime could be reduced significantly. A neural network-based tool was developed for monitoring pump performance and aiding in predicting pump failure. Once trained, neural networks can rapidly process many combinations of input values other than those used for training to approximate previously unknown output values. This neural network was applied to establish relationships among the critical frequencies and aid in predicting failures. Training pairs were developed from frequency scans from typical tunnel operations. After training, various combinations of critical pump frequencies were propagated through the neural network. The approximated output was used to create a contour plot depicting the relationships of the input frequencies to the output pump frequency.

Rogers, James L.↗
NASA NTRS1978

Measurements of noise produced by flow past lifting surfaces

Wind tunnel studies have been conducted to determine the specific locations of aerodynamic noise production within the flow field about various lifting-surface configurations. The models tested included low aspect ratio shapes intended to represent aircraft flaps, a finite aspect ratio NACA 0012 wing, and a multi-element wing section consisting of a main section, a leading edge flap, and dual trailing edge flaps. Turbulence was induced on the models by surface roughness. Lift and drag were measured for the flap models. Hot-wire anemometry was used for study of the flap-model vortex roll-up. Apparent noise source distributions were measured by use of a directional microphone system, located outside the tunnel, which was scanned about the flow region to be analyzed under computer control. These distributions exhibited a diversity of pattern, suggesting that several flow processes are important to lifting-surface noise production. Speculation concerning these processes is offered.

Kendall, J. M.↗
NASA NTRS2016

A New High Channel-Count, High Scan-Rate, Data Acquisition System for the NASA Langley Transonic Dynamics Tunnel

A data acquisition system upgrade project, known as AB-DAS, is underway at the NASA Langley Transonic Dynamics Tunnel. AB-DAS will soon serve as the primary data system and will substantially increase the scan-rate capabilities and analog channel count while maintaining other unique aeroelastic and dynamic test capabilities required of the facility. AB-DAS is configurable, adaptable, and enables buffet and aeroacoustic tests by synchronously scanning all analog channels and recording the high scan-rate time history values for each data quantity. AB-DAS is currently available for use as a stand-alone data system with limited capabilities while development continues. This paper describes AB-DAS, the design methodology, and the current features and capabilities. It also outlines the future work and projected capabilities following completion of the data system upgrade project.

Ivanco, Thomas G.↗
DOE OSTI2024

Magnetochiral tunneling in paramagnetic Co 1/3 NbS 2

Electric currents have the intriguing ability to induce magnetization in nonmagnetic crystals with sufficiently low crystallographic symmetry. Some associated phenomena include the non-linear anomalous Hall effect in polar crystals and the nonreciprocal directional dichroism in chiral crystals when magnetic fields are applied. In this work, we demonstrate that the same underlying physics is also manifested in the electronic tunneling process between the surface of a nonmagnetic chiral material and a magnetized scanning probe. In the paramagnetic but chiral metallic compound Co 1/3 NbS 2 , the magnetization induced by the tunneling current is shown to become detectable by its coupling to the magnetization of the tip itself. This results in a contrast across different chiral domains, achieving atomic-scale spatial resolution of structural chirality. To support the proposed mechanism, we used first-principles theory to compute the chirality-dependent current-induced magnetization and Berry curvature in the bulk of the material. Our demonstration of this magnetochiral tunneling effect opens up an avenue for investigating atomic-scale variations in the local crystallographic symmetry and electronic structure across the structural domain boundaries of low-symmetry nonmagnetic crystals.

36 MATERIALS SCIENCE↗
NASA NTRS1973

Laser Doppler velocimeter investigation of trailing vortices behind a semi-span swept wing in a landing configuration

Measured axial and tangential velocity profiles in the near wake vortices of a semi-span model of the Convair 990 wing in the NASA-Ames 7- by 10-foot wind tunnel are presented. A scanning laser Doppler velocimeter was used to obtain data at two different downstream stations (0.49 and 1.25 wing spans) at various angles of attack and configurations from wing alone to wing plus nacelles, anti-shock bodies, and flaps deflected 27 deg (landing configuration). It is shown that the velocity distributions within the wake are quite sensitive to span loading. Specifically, it is illustrated that an aircraft flying at given lift coefficient (C SUB L), can substantially reduce its trailing vortex upset potential by deploying its flaps and altering its flight attitude to maintain the same C SUB L. This might be taken into consideration along with performance and noise considerations in the selection of aircraft approach lift over drag.

Ciffone, D. L.↗
NASA NTRS1990

Adaptation of electronically scanned pressure measurement technology at Langley Research Center

The use of pressure-measurement devices based on electronic scanning in wind-tunnel and other settings with harsh conditions is discussed in terms of adaptations required to protect the integrity of the devices and output data. The applications considered include thermal extremes, long cable lengths, very low pressure, high-line pressure, and variable-reference calibrations. Some of the adaptation techniques are thermal enclosures, remote power supplies, low-pressure standards, and biasing regulators.

Mitchell, Michael↗
NASA NTRS2000

Wind Tunnel Management and Resource Optimization: A Systems Modeling Approach

Time, money, and, personnel are becoming increasingly scarce resources within government agencies due to a reduction in funding and the desire to demonstrate responsible economic efficiency. The ability of an organization to plan and schedule resources effectively can provide the necessary leverage to improve productivity, provide continuous support to all projects, and insure flexibility in a rapidly changing environment. Without adequate internal controls the organization is forced to rely on external support, waste precious resources, and risk an inefficient response to change. Management systems must be developed and applied that strive to maximize the utility of existing resources in order to achieve the goal of "faster, cheaper, better". An area of concern within NASA Langley Research Center was the scheduling, planning, and resource management of the Wind Tunnel Enterprise operations. Nine wind tunnels make up the Enterprise. Prior to this research, these wind tunnel groups did not employ a rigorous or standardized management planning system. In addition, each wind tunnel unit operated from a position of autonomy, with little coordination of clients, resources, or project control. For operating and planning purposes, each wind tunnel operating unit must balance inputs from a variety of sources. Although each unit is managed by individual Facility Operations groups, other stakeholders influence wind tunnel operations. These groups include, for example, the various researchers and clients who use the facility, the Facility System Engineering Division (FSED) tasked with wind tunnel repair and upgrade, the Langley Research Center (LaRC) Fabrication (FAB) group which fabricates repair parts and provides test model upkeep, the NASA and LARC Strategic Plans, and unscheduled use of the facilities by important clients. Expanding these influences horizontally through nine wind tunnel operations and vertically along the NASA management structure greatly increases the complexity of developing a model that can be used for successfully implementing a standardized management planning tool. The objective of this study was to implement an Integrated Wind Tunnel Planning System to improve the operations within the aeronautics testing and research group, in particular Wind Tunnel Enterprise. The study included following steps: Conducted literature search and expert discussions (NASA and Old Dominion University faculty), Performed environmental scan of NASA Langley wind tunnel operations as foundation for problem definition. Established operation requirements and evaluation methodologies. Examined windtunnel operations to map out the common characteristics, critical components, and system structure. Reviewed and evaluated various project scheduling and management systems for implementation, Evaluated and implemented "Theory of Constraints (TOC)" project scheduling methodology at NASA Langley wind tunnel operations together with NASA staff.

Jacobs, Derya, A.↗
NASA NTRS2021

High-speed wide-angle interleaved scanning technique for a 3D imaging lidar

In this paper, we describe a novel interleaved scanner for an eye-safe 3D scanning lidar system to measure aerodynamic phenomena in a wind tunnel using elastic backscatter from seeding particles. The scanner assembly consists of a rotating polygon scanner for line scanning along the fast axis, a galvanometer (galvo) scanner for scanning along the slow axis, angular position sensors and motor controllers. The polygon scanner sweeps the lidar beam at up to 10,000 lines/s across a 27 deg angular field-of-regard in the fast axis, while the galvo scanner covers an angular range of 20 deg in the slow axis. Using this scanner, the lidar can perform non-intrusive flow visualization, velocimetry, and hard target mapping at mmscale spatial resolution to a standoff range of 5 m at an update rate of 50 Hz for the full field-of-regard. An interleaved scanning methodology for the acquisition of two snapshots of 3D lidar intensity data with a 100 μs time offset is discussed. The design of the control and data acquisition electronics is described. The effects of rapid scanning on the response of a narrow field-of-view lidar are addressed. The design of the scanner is scalable and can be tailored to meet the requirements of other applications by increasing or decreasing the standoff range, angular field-of-regard and scan rate.

3D Imaging Lidar↗