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At least 1,153 records · Page 64

Instrumentation technology

Some of the efforts made in applying technologically new tools to today's propulsion measurement problems are described. They include: (1) a blade-tip clearance system; (2) a pulsed thermocouple system used to measure gas temperature with a thermocouple at temperatures above the melting point of the thermocouple; (3) an optical technique for measuring blade flutter; (4) a probe for dynamic flow and flow angle measurement; and (5) a laser anemometer system for rapidly mapping the flow profiles between the blades of a rotating compressor.

Nieberding, W. C.↗

The shuttle glow: A program to study the ram-induced phenomena

In January 1984, a proposal was submitted to NASA Headquarters entitled The Shuttle Glow: A Program to Determine the Physics of the Ram induced Phenomena. This proposal included the following elements in a shuttlebased experiment: (1) The use of a special flat generating surface 1 x 3 m on which the glow can be produced and observed. This surface will be maneuvered to vary the orientation of ram flow and of projected component of geomagnetic field. (2) Remotely mounted optical instruments to view the glowing layer on the plate. By scanning, the variation of radiance as a function of wavelength and standoff distance from the plate will be observed looking parallel to the plate. (3) The preferred location of the generating plate and in situ diagnostics is on the end of the Remote Manipulator System (RMS) arm.

Anderson, H. R.↗

Optical elements formed by compressed gases: Analysis and potential applications

Spherical, cylindrical, and conical shock waves are optically analogous to gas lenses. The geometrical optics of these shock configurations are analyzed as they pertain to flow visualization instruments, particularly the rainbow schlieren apparatus and single-pass interferometers. It is proposed that a lens or mirror formed by gas compressed between plastic sheets has potential as a fluid visualization test object; as the objective mirror in a very large space-based telescope, communication antenna, or energy collector; as the objective mirror in inexpensive commercial telescopes; and as a component in fluid visualization apparatuses.

Howes, W. L.↗

Optical interferometry in fluid dynamics research

Optical interferometry techniques were applied to the investigation of transonic airfoil flow fields in large wind tunnels. Holographic interferometry techniques were used to study 2 dimensional symmetric NACA 64A010 and Douglas Aircraft Co. DSMA671 supercritical airfoil performance in the NASA Ames 2 x 2 ft transonic wind tunnel. Quantitative data obtained from the interferograms were compared to the surface pressure data. The agreement obtained verified the accuracy of the flow visualization and demonstrated the potential for acquiring quantitative scalar results. Measurements of the inviscid flow speed and the boundary layer and wake velocity profiles were extracted from the interferograms and compared to laser Doppler velocimeter measurements. These results were also in good agreement. A method for acquiring real time interferometric data in large scale facilities was developed. This method, based on the point diffraction interferometer, was successfully tested in the 2 x 2 ft transonic wind tunnel. The holographic and real time interferometry methods were applied to the investigations of circulation control airfoils utilizing the Coanda effect. These results reveals the details of the jet interacting with the trailing edge boundary layer and the other parameters affecting the lift augmentation.

Bachalo, W. D.↗

Turbulent mixing layers in the interstellar and intracluster medium

Cold clouds embedded in hot turbulent gas are often observed in the interstellar medium of galaxies and in the intracluster medium. Mixing layers develop around the clouds by the action of the turbulent gas. It is shown that their column density is limited by cooling and their mean temperature by the momentum flux. Provided that mixing is efficient, the mean temperature is the geometric mean of the hot and cold gas temperatures. EUV radiation from mixing layers around filaments in cluster cooling flows photoionizes the colder gas and may produce the commonly observed optical and UV emission lines. Mixing layers around cold galactic clouds can produce absorption by O VI and similar species with a column density consistent with observations.

Begelman, Mitchell C.↗

Design and fabrication of the All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter

We have designed, analyzed, and are now fabricating an All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter for solar research. This new instrument operates in a narrow bandpass centered at 215.7 A - the neutral hydrogen Ly-alpha line. It is shorter and faster than the telescope which produced solar Ly-alpha images as a part of the MSSTA payload that was launched on May 13, 1991. The Ly-alpha line is produced and linearly polarized in the solar corona by resonance scattering, and the presence of a magnetic field modifies this polarization according to the Hanle effect. The Lyman-alpha Coronagraph/Polarimeter instrument has been designed to measure coronal magnetic fields by interpreting, via the Hanle effect, the measured linear polarization of the coronal Ly-alpha line. Ultrasmooth mirrors, polarizers, and filters are being flow-polished for this instrument from CVD silicon carbide substrates. These optical components will be coated using advanced induced transmission and absorption thin film multilayer coatings to optimize the reflectivity and polarization properties at 1215.7 A. We describe some of the solar imaging results obtained with the MSSTA Lyman-alpha coronagraph. We also discuss the optical design parameters and fabrication plans for the All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter.

Hoover, Richard B.↗

Laser/Spectroscopic Determination Of Mass Flows

Mass flow rates of air and other gases computed from absorption-spectroscopic measurements of light generated by tunable diode lasers. Rates of flow measured nonintrusively. Method implemented with rugged, compact, economical lasers and optical fibers to guide laser light to and from measurement locations.

Hanson, R. K.↗

Hubble Space Telescope imaging of the Seyfert 2 galaxy NGC 2110

Hubble Space Telescope (HST) images of the Seyfert 2 galaxy NGC 2110 in the emission lines of (O III) lambda lambda-4959, 5007 and H-alpha + (N II) lambda lambda-6548, 6584 and the nearby continuum are presented. After deconvolution, the resolution of these images is approximately 0.1 sec, corresponding to a linear scale of approximately 23 pc at the assumed distance (46.8 Mpc) to this galaxy. The dominant line emission is associated with a strongly curved, narrow, 1 sec (230 pc) long feature emanating from the nucleus to the north. The morphology of this feature suggests that it may represent gas flowing outward from the nucleus (perhaps as a 'jet'). While this optical emission-line feature and the jetlike radio emission extend along a similar P.A., their detailed brightness distributions are loosely anticorrelated. In particular, there is no line emission associated with the off-nuclear 6 cm peaks and only weak radio emission along the optical 'jet'. On a larger scale, there is an S-shaped distribution of ionized gas (seen best in H-alpha) extending approximately 4 sec north and south of the nucleus. Ground-based kinematical data suggest this larger scale component represents normally rotating, ambient, interstellar gas photoionized by the central source. A continuum color map derived from HST observations shows evidence for an unresolved region (scale less than 23 pc) of very strong reddening at the location of the optical and radio nucleus. The location and size of the reddened region are consistent with obscuration by a dusty torus, but the observed reddening provides only a lower limit (A(sub V) greater than or equal to 4.6(sub -1.7 sup +1.2) mag) on the amount of obscuration to the nucleus. Nevertheless, this obscuration is sufficient to account for the 'energy deficit' previously reported in this object.

Mulchaey, John S.↗

Design and Fabrication of the All-Reflecting H-Lyman alpha Coronagraph/Polarimeter

We have designed, analyzed, and are now fabricating an All-Reflecting H-Lyman alpha Coronagraph/Polarimeter for solar research. This new instrument operates in a narrow bandpass centered at lambda 1215.7 A-the neutral hydrogen Lyman alpha (Ly-alpha) line. It is shorter and faster than the telescope which produced solar Ly-alpha images as a part of the MSSTA payload that was launched on May 13, 1991. The Ly-alpha line is produced and linearly polarized in the solar corona by resonance scattering, and the presence of a magnetic field modifies this polarization according to the Hanle effect. The Lyman alpha Coronagraph/Polarimeter instrument has been designed to measure coronal magnetic fields by interpreting, via the Hanle effect, the measured linear polarization of the coronal Ly-alpha line. Ultrasmooth mirrors, polarizers, and filters are being flow-polished for this instrument from CVD silicon carbide substrates. These optical components will be coated using advanced induced transmission and absorption thin film multilayer coatings, to optimize the reflectivity and polarization properties at 1215.7 A. We describe some of the solar imaging results obtained with the MSSTA Lyman alpha coronagraph. We also discuss the optical design parameters and fabrication plans for the All-Reflecting H-Lyman alpha Coronagraph/Polarimeter.

Hoover, Richard B.↗

Mixing Dynamics Induced by Traveling Magnetic Fields

Microstructural and compositional homogeneity in metals and alloys can only be achieved if the initial melt is homogeneous prior to the onset of solidification processing. Naturally induced convection may initially facilitate this requirement but upon the onset of solidification significant compositional variations generally arise leading to undesired segregation. Application of alternating magnetic fields to promote a uniform bulk liquid concentration during solidification processing has been suggested. To investigate such possibilities an initial study of using traveling magnetic fields (TMF) to promote melt homogenization is reported in this work. Theoretically, the effect of TMF-induced convection on mixing phenomena is studied in the laminar regime of flow. Experimentally, with and without applied fields, both: mixing dynamics by optically monitoring the spreading of an initially localized dye in transparent fluids and, compositional variations in metal alloys have been investigated.

Grugel, Richard N.↗

Considerations for High-Speed Background-Oriented Schlieren Visualization Capability for Ground Test Facilities

Since its introduction in the year 2000, background-oriented schlieren (BOS) has become a cornerstone technique for visualizing variable-density flows. In this review, we provide a rigorous examination of the optical principles underpinning BOS and related refractive-index-based techniques, complemented by an appendix linking schlieren imaging to Maxwell’s equations. The core sections delve into the practical aspects of BOS, with detailed discussions on image processing algorithms and critical considerations for experimental setups. We then explore recent advancements and innovations, including extensions of BOS with tomography, data assimilation, and event-based imaging. Finally, we present notable applications of BOS in challenging and unconventional environments, showcasing the method’s versatility and offer inspiration for future research directions.

Brett Bathel↗

Feasibility of supersonic diode pumped alkali lasers: Model calculations

The feasibility of supersonic operation of diode pumped alkali lasers (DPALs) is studied for Cs and K atoms applying model calculations, based on a semi-analytical model previously used for studying static and subsonic flow DPALs. The operation of supersonic lasers is compared with that measured and modeled in subsonic lasers. The maximum power of supersonic Cs and K lasers is found to be higher than that of subsonic lasers with the same resonator and alkali density at the laser inlet by 25% and 70%, respectively. These results indicate that for scaling-up the power of DPALs, supersonic expansion should be considered.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

On the Rayleigh–Kuo criterion for the tertiary instability of zonal flows

This study reports the stability conditions for intense zonal flows (ZFs) and the growth rate γ TI of the corresponding “tertiary” instability (TI) within the generalized Hasegawa–Mima plasma model. The analytical calculation extends and revises Kuo's analysis of the mathematically similar barotropic vorticity equation for incompressible neutral fluids on a rotating sphere [H.-L. Kuo, J. Meteor. 6, 105 (1949)]; then, the results are applied to the plasma case. An error in Kuo's original result is pointed out. An explicit analytical formula for γ TI is derived and compared with numerical calculations. It is shown that, within the generalized Hasegawa–Mima model, a sinusoidal ZF is TI-unstable if and only if it satisfies the Rayleigh–Kuo criterion (known from geophysics) and that the ZF wave number exceeds the inverse ion sound radius. For non-sinusoidal ZFs, the results are qualitatively similar. As a corollary, there is no TI in the geometrical-optics limit, i.e., when the perturbation wavelength is small compared to the ZF scale. Finally, this also means that the traditional wave kinetic equation, which is derived under the geometrical-optics assumption, cannot adequately describe the ZF stability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Characterization and testing of 30 kV, 60 kW electron optical column for melting applications

High energy electron beams (30-150 keV) are widely used as intense heat source in welding, melting and evaporation of refractory metals. These operations are mostly carried out in high vacuum (10{sup -4}-10{sup -5} mbar) to aid unimpeded flow of electrons from generation to the point of application. A 30 kV, 60 kW Electron beam optical column (EOC) is designed and developed under the high power beam technology programme. The optical column consists of an electron gun and twin electromagnetic focusing lenses. The heating power of emitter, gun perveance, grid voltage control, beam focusing with the twin electromagnetic lenses and beam spot size measurements are reported in this paper. The results are compared with the design values. Operational issues during the high power melting and the strategy for automation of the electron gun are discussed. (author)

43 PARTICLE ACCELERATORS↗

NASA Tech Briefs, October 2011

Topics covered include: Laser Truss Sensor for Segmented Telescope Phasing; Qualifications of Bonding Process of Temperature Sensors to Deep-Space Missions; Optical Sensors for Monitoring Gamma and Neutron Radiation; Compliant Tactile Sensors; Cytometer on a Chip; Measuring Input Thresholds on an Existing Board; Scanning and Defocusing Properties of Microstrip Reflectarray Antennas; Cable Tester Box; Programmable Oscillator; Fault-Tolerant, Radiation-Hard DSP; Sub-Shot Noise Power Source for Microelectronics; Asynchronous Message Service Reference Implementation; Zero-Copy Objects System; Delay and Disruption Tolerant Networking MACHETE Model; Contact Graph Routing; Parallel Eclipse Project Checkout; Technique for Configuring an Actively Cooled Thermal Shield in a Flight System; Use of Additives to Improve Performance of Methyl Butyrate-Based Lithium-Ion Electrolytes; Li-Ion Cells Employing Electrolytes with Methyl Propionate and Ethyl Butyrate Co-Solvents; Improved Devices for Collecting Sweat for Chemical Analysis; Tissue Photolithography; Method for Impeding Degradation of Porous Silicon Structures; External Cooling Coupled to Reduced Extremity Pressure Device; A Zero-Gravity Cup for Drinking Beverages in Microgravity; Co-Flow Hollow Cathode Technology; Programmable Aperture with MEMS Microshutter Arrays; Polished Panel Optical Receiver for Simultaneous RF/Optical Telemetry with Large DSN Antennas; Adaptive System Modeling for Spacecraft Simulation; Lidar-Based Navigation Algorithm for Safe Lunar Landing; Tracking Object Existence From an Autonomous Patrol Vehicle; Rad-Hard, Miniaturized, Scalable, High-Voltage Switching Module for Power Applications; and Architecture for a 1-GHz Digital RADAR.

Source record↗

Progress on a Rayleigh Scattering Mass Flux Measurement Technique

A Rayleigh scattering diagnostic has been developed to provide mass flux measurements in wind tunnel flows. Spectroscopic molecular Rayleigh scattering is an established flow diagnostic tool that has the ability to provide simultaneous density and velocity measurements in gaseous flows. Rayleigh scattered light from a focused 10 Watt continuous-wave laser beam is collected and fiber-optically transmitted to a solid Fabry-Perot etalon for spectral analysis. The circular interference pattern that contains the spectral information that is needed to determine the flow properties is imaged onto a CCD detector. Baseline measurements of density and velocity in the test section of the 15 cm x 15 cm Supersonic Wind Tunnel at NASA Glenn Research Center are presented as well as velocity measurements within a supersonic combustion ramjet engine isolator model installed in the tunnel test section.

Mielke-Fagan, Amy F.↗

Model scattering envelopes of young stellar objects. II - Infalling envelopes

We present scattered light images for models of young stellar objects surrounded by dusty envelopes. The envelopes are assumed to have finite angular momentum and are falling in steady flow onto a disk. The model envelopes include holes, such as might be created by energetic bipolar flows. We calculate images using the Monte Carlo method to follow the light scattered in the dusty envelope and circumstellar disk, assuming that the photons originate from the central source. Adopting typical interstellar medium dust opacities and expected mass infall rates for protostars of about 10 exp -6 solar mass/yr, we find that detectable amounts of optical radiation can escape from envelopes falling into a disk as small as about 10-100 AU, depending upon the viewing angle and the size of the bipolar flow cavity. We suggest that the extended optical and near-IR light observed around several young stars is scattered by dusty infalling envelopes rather than disks.

Whitney, Barbara A.↗

Convective flow effects on protein crystal growth

The experimental setup for the in-situ high resolution optical monitoring of protein crystal growth/dissolution morphologies was substantially improved. By augmenting the observation system with a temperature-controlled enclosure, laser illumination for the interferometric microscope, and software for pixel by pixel light intensity recording, a height resolution of about two unit cells for lysozyme can now be obtained. The repartitioning of Na(+) and Cl(-) ions between lysozyme solutions and crystals was studied. Quite unexpectedly, it was found that the longer crystals were in contact with their solution, the lower was their ion content. The development of a model for diffusive-convective transport and resulting distribution of the growth rate on facets was completed. Results obtained for a realistic growth cell geometry show interesting differences between 'growth runs' at 1g and 0g. The kinematic viscosity of lysozyme solutions of various supersaturations and salt concentrations was monitored over time. In contrast to the preliminary finding of other authors, no changes in viscosity were found over four days. The experimental setup for light scattering investigations of aggregation and nucleation in protein solutions was completed, and a computer program for the evaluation of multi-angle light scattering data was acquired.

Rosenberger, Franz↗