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  • Other Sources  (653)
  • NASA Technical Reports  (653)
  • FLUID MECHANICS AND HEAT TRANSFER  (233)
  • INSTRUMENTATION AND PHOTOGRAPHY  (226)
  • MECHANICAL ENGINEERING  (194)
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  • NASA Technical Reports  (653)
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  • 1
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Surface-Tension Gradient Induced Flows at Reduced Gravity; 24 p
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  • 2
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Surface-Tension Gradient Induced Flows at Reduced Gravity; 21 p
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  • 3
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    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 240-241
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  • 4
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 236-237
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  • 5
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 238-239
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  • 6
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 234-235
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  • 7
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 231
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  • 8
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 229-230
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  • 9
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 232-233
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  • 10
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 227-228
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  • 11
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 221-223
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  • 12
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 148
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  • 13
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    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 130-131
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  • 14
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    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 16
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  • 15
    Publication Date: 2011-08-18
    Description: The chemiluminescent rocket ozonesonde utilizing rhodamine-B as a detector and self-pumping for air sampling has been improved. The instrument employs standard meteorological sounding systems and is the only technique available for routine nighttime ozone measurements above balloon altitudes. The chemiluminescent detector, when properly calibrated, is shown to be specific to ozone, stable, and of sufficient sensitivity for accurate measurements of ozone from about 65-20 km. An error analysis indicates that the measured ozone profiles have an absolute accuracy of about + or - 12% and a precision of about + or - 6%. Approximately 20 flights have been conducted for geophysical investigations, while additional flights were conducted with other rocket and satellite ozone soundings for comparisons. In general, these comparisons showed good agreement.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 51; Oct. 198
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  • 16
    Publication Date: 2011-08-17
    Description: A circular-scan streak tube designed for use in a laser ranging system is described. Electrostatic focusing is used between the photocathode and a microchannel plate, and electrons from the microchannel plate are proximity focused onto an output phosphor screen. Electron beam deflection is achieved by driving two orthogonal sets of deflection plate assemblies in phase quadrature at a frequency of 200 MHz. The light intensity in the output beam trace is measured by using a circular Reticon array of 720 photodiodes, which is fiber-optically coupled to the output phosphor screen of the tube. Sample measurements of frequency-doubled Nd:YAG laser-pulse waveforms are given. Also the output beamwidth has been measured at the 200-MHz deflection frequency. The results suggest a limiting resolution of 33 psec for the circular-scan streak tube used for these tests.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; Oct. 15
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  • 17
    Publication Date: 2011-08-17
    Description: The use of laser-induced water Raman backscatter for remote thin oil film detection and thickness measurement is reported here for the first time. A 337.1-nm nitrogen laser was used to excite the 3400-cm-1 OH stretch band of natural ocean water beneath the oil slick from an altitude of 150 m. The signal strength of the 381-nm water Raman backscatter was always observed to depress when the oil was encountered and then return to its original undepressed value after complete aircraft traversal of the floating slick. After removal of background and oil fluorescence contributions, the ratio of the depressed-to-undepressed airborne water Raman signal intensities, together with laboratory measured oil extinction coefficients, is used to calculate the oil film thickness.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; Oct. 1
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  • 18
    Publication Date: 2011-08-17
    Description: In the present paper, a simple numerical model is used to study the warming of the mixed layer during the early summer. It is shown that the springtime temperature increase in the layer below the mixed layer (for example, in the cold pool on a continental shelf) has a maximum value which occurs for a limiting value of the surface heat flux. This is a result of the positive feedback at large Richardson numbers between stability and vertical diffusion of heat. The springtime temperature increase in the mixed layer increases nonlinearly with surface heat flux, because of the same positive feedback. The effects of interseasonal fluctuations of the surface heat flux on the spring and summer mixed layer and deeper temperature increases can be as great as the effect of interseasonal fluctuations of the average heat flux.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Geophysical Research; 85; Sept. 20
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  • 19
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    Publication Date: 2011-08-17
    Description: Research, development, and application of atmospheric laser Doppler velocimetry are overviewed. Consideration is given to operation principles of CO2 heterodyne systems. Global wind, pollution, V/STOL flow, and true airspeed measurements are outlined. Wind energy, dust devils, water spouts, tornadoes, and aircraft wake vortices are covered.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering; 19; July-Aug
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  • 20
    Publication Date: 2011-08-17
    Description: A pulsed infrared lidar system designed for application to the remote sensing of atmospheric trace gases from an airborne platform is described. The system is also capable of measuring the infrared backscatter characteristics of the ocean surface, terrain, cloud, and aerosol targets. The lidar employed is based on dual wavelength pulse energy measurements in the 9-11 micrometer wavelength region.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering; 19; July-Aug
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  • 21
    Publication Date: 2011-08-17
    Description: A simple device is described that is capable of providing real-time 3-D viewing of extended X-ray and gamma-ray objects. The visible-light images produced by the device are not merely stereoscopic, i.e., one perspective, but possess both horizontal and vertical parallax with a reasonably large field of view.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; Sept. 1
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  • 22
    Publication Date: 2011-08-17
    Description: Infrared grid polarizers consisting of copper lines with a 3.6-micron grid constant on a 4-micron-thick Mylar polyester substrate have been prepared by the techniques of photolithography and sputter-etching. Their polarization properties have been measured and found to be suitable for use at infrared frequencies below 700/cm. The polarizers have been used to extend the useful frequency range of a Martin-Puplett polarizing interferometer designed for Fourier transform spectroscopy. The efficiency of the interferometer has been measured over a frequency range from 50 to 700/cm and compared to that of a conventional Michelson interferometer. The results are shown to be consistent with the measured properties of the polarizers. Methods are suggested for improving the efficiency of a Martin-Puplett interferometer which employs these polarizers.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Infrared Physics; 20; July 198
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  • 23
    Publication Date: 2011-08-17
    Description: A tunable diode laser spectrometer with several unique features has been developed for use in the middle IR. The all-reflective optical system has a dual-beam configuration before the dispersive mode selector to eliminate transit-angle errors at the calibration etalon. By maintaining separated beams through the mode selector, beam combiner losses are avoided. Averaging successive sweeps of the current-modulated laser permits stable reproducible spectral integrations, eliminating etalon thermal errors and producing high photometric sensitivity. Line strengths have been measured using this instrument for eleven transitions in nu4 of (C-12)H4. These include R0 and R1 and nine P-branch transitions in the 1202-1263-per cm range. Techniques for measuring strengths with a diode laser are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; Aug. 15
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  • 24
    Publication Date: 2011-08-17
    Description: Aerosols containing solid, spherical stearic acid particles with a mean diameter of 0.8 micron and a geometric standard deviation of 1.28 were sampled with small bore front-facing aspirating probes in near-sonic and supersonic unheated free jets. The results are compared to compute the sampling error associated with a high-speed jet sample.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Air Pollution Control Association; vol. 30
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  • 25
    Publication Date: 2011-08-17
    Description: In order to relate the measured fringe shift of an interferometer to the density of a medium, the relation between density and refractive index, which is expressed by the specific refractivity, must be known. In the present paper, the specific refractivities of the wind tunnel test gases CF4 and C2F6 are determined in order to verify estimations based on the atomic refractivities of carbon and fluorine. A Twyman-Green two-beam interferometer with a 633-nm He-Ne laser light source was used to measure the specific refractivity as a function of fringe shift as the density of the gas was changed. Values of 0.122 and 0.131 cu cm/g were obtained for CF4 and C2F6 respectively at a temperature of 300 K, which are within 1% of the values computed from the atomic refractivities.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Chemical Physics; 73; July 15
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  • 26
    Publication Date: 2011-08-17
    Description: Shapes and stability of surface-tension-endowed drops rotating rigidly at fixed angular momentum are calculated by finite-element analysis. A new family of asymmetric two-lobed drop shapes is discovered that branches from, and rejoins, the Pik-Pichak family of symmetric two-lobed shapes. The computations are verified for axisymmetric and symmetric two-lobed drop shape by comparison with previous approximations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physical Review Letters; 45; July 21
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  • 27
    Publication Date: 2011-08-17
    Description: The paper presents an instrument that directly measures multispectral absorption coefficient of turbid natural water. Attention is given to the design, which is shown to incorporate methods for the compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in the background light level. In addition, when used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Finally, it is reported that systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; May 15
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  • 28
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    Publication Date: 2011-08-17
    Description: The present work deals with the fundamentals of gas lubrication theory, which forms the foundation of all analytical design tools for gas bearings. Most of the hard lessons learned in the past are outlined with reference to dry contact, debris ingestion, sliding speed, and chemical stability of lubricant. The mathematical theory of gas lubrication is described for scaling rules in thin-film viscous flow, momentum conservation, mass conservation, energy conservation, isothermal gas bearing theory, coupling effects, and global bearing characteristics. Particular attention is given to the governing differential equations for common bearing configurations. Also discussed are representative solutions of self-acting gas bearings, externally pressurized bearings, and time-dependent effects.
    Keywords: MECHANICAL ENGINEERING
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  • 29
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    Publication Date: 2011-08-17
    Description: The influences of memory effects, coupling between velocity and temperature fluctuations and tensorial transport properties on momentum and heat transfers in turbulent flow which do not follow the Boussinesq relation are examined. It is shown that the memory effect, represented by the Lagrangian of the velocity gradients, can account for the decoupling between the flux and the gradient, while the tensorial properties of the transport coefficients allow a normal Boussinesq-type transfer with memory and anomalous counter-gradient or gradient-less transport.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 30
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    Publication Date: 2011-08-17
    Description: An experimental work is discussed whose objective was to obtain data that show the effect of temperature and temperature fluctuations on surface noise. This was accomplished experimentally by immersing a small chord airfoil in the turbulent airstream of a hot jet. The theory and experiment reported by Olsen (1976) provided a guide for designing and validating the hot jet experiment and for interpreting the data. It is shown that increased temperature causes a small decrease in the sound levels; at the same time it causes a shift in the spectra that is smaller but similar to the shift observed with subsonic hot jet noise.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal; 18; Mar. 198
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  • 31
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    Publication Date: 2011-08-18
    Description: A model is proposed for the study of the growth and shrinkage of gas bubbles in systems containing many gas bubbles. The key feature of this model is the replacement of the bubbles by point sources of gas concentration. Calculations are performed in the simple case of an initial uniform array of bubbles of equal radii.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Chemical Engineering Science; 35; 1980
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  • 32
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    Publication Date: 2011-08-18
    Description: Recent progress in the development of vortex methods and their applications to the numerical simulation of incompressible fluid flows are reviewed. Emphasis is on recent results concerning the accuracy of these methods, improvements in computational efficiency, and the development of three-dimensional methods. Simulations of several example flows which display some of the strengths and weaknesses of vortex methods are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics; 37; Oct. 198
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  • 33
    Publication Date: 2011-08-18
    Description: A scaling correlator optical pattern recognition system is described in which a lensless matched spatial filter (with the second Fourier transform lens and the matched spatial filter recorded on the same plate) is used with a first Fourier transform lens that is also an holographic optical element. The matched spatial filter is recorded at one wavelength and correlation is obtained at a second wavelength. Experimental demonstration and output correlation SNR data are reported, together with a comparison of the system's noise level using conventional optics and holographic elements.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optics Communications; 34; Sept
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  • 34
    Publication Date: 2011-08-17
    Description: Photographic images enhanced by the method of Thiourea-S35 autoradiography are evaluated in terms of signal-to-noise ratio, detective quantum efficiency (DQE), and Wiener spectrum analysis using digitized images. It is determined that the original signal-to-noise ratio is not degraded by the intensification process which allows an increase in the practical working DQE as a function of density. These results apply at all spatial frequencies that were tested. The advantage given by autoradiography is the ability to produce usable images from emulsions originally exposed to the low densities corresponding to maximum DQE and movement of faint image densities above the level of the threshold for detection.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Astronomical Society of the Pacific; vol. 92
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  • 35
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    Publication Date: 2011-08-17
    Description: The quality of image reconstructions from discrete data suffers not only from the blurring of spatial detail caused by limitations in the spatial frequency response of electrooptical systems, but also from the aliasing generated if spatial detail has been undersampled. Previous studies have observed that reasonable spot intensity profiles and photosensor aperture shapes of equivalent size result in about equal blurring but that some profiles and shapes suppress aliasing better than others. This paper presents quantitative results of the magnitude of aliasing and blurring as a function of random radiance fields typical for natural scenes and of spatial responses and sampling intervals typical for TV cameras and optical-mechanical scanners. These results indicate that aliasing may often be a larger source of degradation than either blurring or electronic noise.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; July 1
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  • 36
    Publication Date: 2011-08-17
    Description: An apparatus is described in which hydrogen atoms were trapped at temperatures down to 1.1 K in the 11 T field of a large volume superconducting magnet. A high sensitivity thermal detector was used to study trapping and recombination of atoms on the detector surface. The apparatus permits the application of extremely high steady state magnetic fields to study the potential effects of electron spin polarization on the stabilization of hydrogen atoms.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 51; May 1980
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  • 37
    Publication Date: 2011-08-17
    Description: A coaxial dual-channel laser system has been developed for the measurement of extinction coefficients of highly absorbing liquids. An empty wedge-shaped sample cell is first translated laterally through a He-Ne laser beam to measure the differential thickness using interference fringes in reflection. The wedge cell is carefully filled with the oil sample and translated through the coaxially positioned dye laser beam for the differential attenuation or extinction measurement. Optional use of the instrumentation as a single-channel extinction measurement system and also as a refractometer is detailed. The system and calibration techniques were applied to the measurement of two crude oils whose extinction values were required to complete the analysis of airborne laser data gathered over four controlled spills.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; Apr. 1
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  • 38
    Publication Date: 2011-08-17
    Description: The paper covers the studies presented on nuclear science and nuclear power systems symposiums. The studies deal with nuclear radiation detectors, nuclear circuits and systems, space and medical instrumentation, as well as with environmental and reactor instrumentation. Data preprocessing and acquisition are discussed. Emphasis is placed on the engineered safety features of nuclear systems.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 39
    Publication Date: 2011-08-17
    Description: This note describes some details of recent (successful) attempts of wall proximity corrections for hot-wire measurements performed in a three-dimensional incompressible turbulent boundary layer. A simple and quite satisfactory method of estimating wall proximity effects on hot-wire readings is suggested.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: DISA Information; Feb. 198
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  • 40
    Publication Date: 2011-08-18
    Description: The dielectric properties of polluted waters are measured with a reflection-type resonant cavity at 1.43 GHz. Very small water samples in quartz tubes of known volume are placed in the center of the maximum electric field. Measurement of the resonance-frequency variation and a change of the cavity's quality factor are used to determine the dielectric properties. The microwave emissivity of the polluted water is then calculated via the Fresnel equation and applied to data reductions of microwave radiometer measurements.
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  • 41
    Publication Date: 2011-08-17
    Description: Limits to low noise equivalent power (NEP) operation of a lithium niobate upconverter are investigated. Upconversion is achieved inside the optical cavity of an Ar-ion laser. Limits to NEP are imposed by limits to conversion efficiency and by noise present in the upconversion process. Conversion efficiency is limited by thermal effects in the lithium niobate. Thermally induced wedging, focusing, and aberrations are caused by the lithium niobate absorption at the 514.5-nm argon pump wavelength. The primary component of noise in the upconverter is due to upconversion of thermal radiation from the lithium niobate crystal. The lowest NEP, at a wavelength of 3.4 microns, achieved in this study was 8.9 x 10 to the -14th W/(Hz to the 1/2 power).
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  • 42
    Publication Date: 2011-08-18
    Description: An investigation was conducted to examine the adhesion and friction of single-crystal diamond in contact with various transition metals and the nature of metal transfer to diamond. Sliding friction experiments were conducted with diamond in sliding contact with the metals yttrium, titanium, zirconium, vanadium, iron, cobalt, nickel, tungsten, platinum, rhenium and rhodium. All experiments were conducted with loads of 0.05 to 0.3 N, at a sliding velocity of 0.003 m per minute, in a vacuum of 10 to the -8th Pa, at room temperature, and on the (111) plane of diamond with sliding in the 110 line type direction. The results of the investigation indicate that the coefficient of friction for diamond in contact with various metals is related to the relative chemical activity of the metals in high vacuum. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to the surface of diamond in sliding.
    Keywords: MECHANICAL ENGINEERING
    Type: Applications of Surface Science; 6; 1980
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  • 43
    Publication Date: 2011-08-17
    Description: Four types of sensors were used to make both dynamic and time-averaged flow measurements in a cold turbine rig to determine the magnitude of errors in time-averaged total-pressure measurement at a station 5 1/2 blade cords downstream from the rotor. The errors turned out to be negligible. The sensors and their intended use are discussed.
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  • 44
    Publication Date: 2011-08-17
    Description: New techniques in nonlinear optical processing are explored, based on the operation of intensity level selection as performed by a Fabry-Perot interferometer containing a phase object. The image being processed is recorded on a medium between the mirrors as a spatially varying phase shift less than pi. The interferometer only transmits light through those portions of the object that corresponds to a single value of the phase and hence to a single intensity level in the input. More complicated operations such as thresholding and analog-to-digital conversion are performed by modulating the light source as the different levels are selected. Photoresist and lithium niobate have been used as phase objects, and experimental data for both are presented. Three kinds of Fabry-Perot interferometers have been used to demonstrate nonlinear processing using coherent and incoherent light. Color images have been produced with black and white inputs and white light illumination.
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  • 45
    Publication Date: 2011-08-17
    Description: The digital recording acquisition subsystem (DRAS) is a wideband digital recording system that can accommodate data sample rates from 0.125 to 8 MHz in binary increments. The implementation of the DRAS for radio interferometry applications in support of the Crustal Dynamics Project is described. The functional and performance characteristics of the equipment and the key aspects of the implementation plan are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: The Telecommun. and Data Acquisition Rept.; p 9-14
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  • 46
    Publication Date: 2011-08-18
    Description: A laser beam manifold and particle photography system has been developed for use in fluid velocity measurements. The laser manifold is a device which transforms a single laser beam into several uniform parallel beams. By orienting two manifolds mutually perpendicular, an optical grid can be formed which acts as a reference for fluid velocity measurements. This optical grid is for all practical purposes totally nonperturbing to the flow. Tracer particles moving in the plane of the grid are then photographed to yield fluid velocities that can be measured relative to the optical grid. System construction and theory are presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 51; Nov. 198
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  • 47
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    Publication Date: 2011-08-18
    Description: This paper examines the Magsat precision vector magnetometer which is designed to measure projections of the ambient field in three orthogonal directions. The system contains a highly stable and linear triaxial fluxgate magnetometer with a dynamic range of + or - 2000 nT (1 nT = 10 to the -9 weber per sq m). The magnetometer electronics, analog-to-digital converter, and digitally controlled current sources are implemented with redundant designs to avoid a loss of data in case of failures. Measurements are carried out with an accuracy of + or - 1 part in 64,000 in magnitude and 5 arcsec in orientation (1 arcsec = 0.00028 deg).
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Johns Hopkins APL Technical Digest; 1; July-Sep
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  • 48
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    Publication Date: 2011-08-18
    Description: The Magsat scalar magnetometer is derived from optical pumping magnetometers flown on the orbiting geophysical observatories. The basic sensor, a cross-coupled arrangement of absorption cells, photodiodes, and amplifiers, oscillates at the Larmor frequency of atomic moments precessing about the ambient field direction. The Larmor frequency output is accumulated digitally and stored for transfer to the spacecraft telemetry stream. In orbit the instrument has met its principal objective of calibrating the vector magnetometer and providing scalar field data.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Johns Hopkins APL Technical Digest; 1; July-Sep
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  • 49
    Publication Date: 2011-08-18
    Description: A simple and direct method is obtained for assessing the distortion of a Doppler line by a Gaussian instrument function. It is suggested that a close approximation to the width of a Gaussian instrument function, or an almost Gaussian function, may be obtained by measuring a line with a Doppler absorption coefficient. The method is applicable to diode laser measurements, and may be used whenever a Gaussian instrument function is a reasonable approximation to real conditions
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Molecular Spectroscopy; 81; 1980
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  • 50
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    Publication Date: 2011-08-18
    Description: The point vortex and vortex blob methods for two dimensional flows are presented. Several results are discussed concerning the numerical analysis of the latter scheme, e.g., the preservation of globally conserved quantities and the analysis of the spatial discretization error resulting from the convection of fixed blobs of vorticity. An application to the two dimensional mixing layer is briefly described. The contour dynamics method is also discussed. The simulation of three dimensional flows with vortex methods is discussed. A natural way to represent the vorticity is in the form of closed tubes of filaments of vorticity, although other schemes are examined. Applications to aircraft trailing vortices and to a turbulent spot in a laminar boundary layer are presented. Hybrid schemes that use an Eulerian mesh to solve the Poisson equation for the velocity field are discussed. The goal of these schemes is to avoid the high cost of the Biot-Savart integration if many vortex elements are used while enjoying most of the advantages of pure Lagrangian schemes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Von Karman Inst. for Fluid Dyn. Computational Fluid Dyn., Vol. 2; 52 p
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  • 51
    Publication Date: 2011-08-18
    Description: The exchange of stabilities is demonstrated for a system with harmonic boundary conditions. The motion of fluid in the presence of temperatures gradients is described. It is shown that this principle holds under free, but not rigid or semirigid, boundary conditions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 17 p
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  • 52
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    Publication Date: 2011-08-18
    Description: The power distribution of an electron seam is analyzed. Digital computer techniques are used to evaluate the radial distribution of power detected by a wire probe circulating through the beam. Results are reported.
    Keywords: MECHANICAL ENGINEERING
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 31 p
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  • 53
    Publication Date: 2011-08-18
    Description: A microcomputer-video system was used to measure both spatial and temporal variations of two dimensional fluid flow velocity fields. The system utilizes two methods: the first method is the traditional one in which tracers are introduced into the fluid and their position compared at two closely spaced times; and the second method involves scattering coherent light in the fluid and obtaining motion by analyzing the multiple exposed speckle pattern recorded on photographic film.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 6 p
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  • 54
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    Publication Date: 2011-08-18
    Description: The linear stability analysis for the stratified flow between two rotating circular cylinders is formulated. Two approaches for the stability analysis are presented. The first approach results in an algebraic eigenvalue problem, while the second results in an initial value problem for the perturbation function. The advantages and disadvantages of both approaches are discussed and a preferable numerical solution technique is outlined.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 13 p
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  • 55
    Publication Date: 2011-08-18
    Description: The details of the flow on the bladed side of a centrifugal type dynamic shaft seal utilized to contain liquid oxygen in the Space Shuttle Main Engine high pressure oxidizer turbopump were clarified. The governing equations are solved to predict the pressure and temperature gradients and to aid in investigating the nature of the liquid-vapor interface. Recommendations for design improvements are discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 22 p
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  • 56
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    Publication Date: 2011-08-18
    Description: Two methods were investigated for retrieving the ball bearing signals buried by the overall signature of an operating large engine such as the main space shuttle engine. The signal averaging method averages n** signals over a time duration equaling the known period of the ball bearing defect frequency. With this method, the desired ball bearing defect signal will be enhanced over the noise by a factor of the square root of n. A second method is to perform a further frequency analysis on the logarithmic spectrum in order to detect and separate different families of harmonics and sidebands, thereby giving information about modulating frequencies. These two alternate IFD methods were carried out with a Norland 3001 waveform and data system. The obtained results are then compared with the power spectral density (PSD) of the overall machine signals and conclusions are made accordingly.
    Keywords: MECHANICAL ENGINEERING
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 24 p
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  • 57
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    Publication Date: 2011-08-18
    Description: The spherical modeling of geophysical fluid flow is examined. In particular the extension of some previous work done in spherical geometry to the specific case of interest in the Spacelab atmospheric circulation experiment is discussed. This involves changing the boundary conditions under which the basic equations are to be solved. For simplicity the linear, axially symmetric steady state solution is sought.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 17 p
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  • 58
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    Publication Date: 2011-08-17
    Description: The astrometric application of the Wide Field Camera and the Planetary Camera is reviewed. It is shown that the digital image centering algorithms can yield a positional accuracy of 0.1 milli-arcsecond. Deconvolution of CCD's sensitivity, non-flatness of the filters, and crinkling of the CCD surface may limit the positional accuracy of 1 milli-arcsecond.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 59
    Publication Date: 2011-08-17
    Description: The results of measuring profiles of temporally determined velocities and Reynolds tension, wall shear stresses and pressure distribution in a three dimensional, turbulent boundary layer with pressure gradients in both tangential directions are reported. For determining the velocities X wire probes were used whose cooling was gauged according to magnitude and direction of the flow and was described with an effective cooling speed. In the evaluation consideration is given to the directional sensitivity of the hot wire. The ratio of the turbulence viscosities is calculated for both tangential directions and is found to be approximately N equals 1.2. Further, the profiles of the mixing path lengths for the flow direction are found to vary only slightly with increasing X-coordinates, while the boundary layer thickness increases substantially. The relationships of turbulent shear stress to turbulent, kinetic fluctuation energy is approximately constant over a large part of the boundary layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 60
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    Publication Date: 2011-08-17
    Description: Equilibrium shapes and stability of rotating drops held together by surface tension are found by computer-aided analysis that uses expansions in finite-element basis functions. Shapes are calculated as extrema of appropriate energies. Stability and relative stability are determined from curvatures of the energy surface in the neighborhood of the extremum. Families of axisymmetric, two-, three-, and four-lobed drop shapes are traced systematically. Bifurcation and turning points are located and the principle of exchange of stabilities is tested. The axisymmetric shapes are stable at low rotation rates but lose stability at the bifurcation to two-lobed shapes. Two-lobed drops isolated with constant angular momentum are stable. The results bear on experiments designed to further those of Plateau (1863).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 61
    Publication Date: 2011-08-17
    Description: The thermal response of the fused silica dome filter in an earth radiation budget WFOV shortwave channel conceptual design and the impact of that response on the channel measurement, is described. Attention is given to results from design definition and performance analysis studies. Consideration is given to problems associated with achieving the desired levels of confidence in a high accuracy filtered earth radiation budget WFOV radiometer. Finally, design approaches, ground calibration, and data reduction techniques that minimize measurement uncertainties are covered.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; June 1
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  • 62
    Publication Date: 2011-08-17
    Description: A group-velocity criterion for vortex breakdown implied by wave trapping theory is applied to vortex flows in a slightly divergent duct that exhibits breakdown. The group velocities for both symmetric (n = 0) and nonsymmetric (n = plus or - 1) modes of wave propagation are calculated for the experimental data. It is found that the flow ahead of the breakdown region is always supercritical and stable to these modes of disturbances. However, the flow field behind the breakdown region may be either supercritical or subcritical to the modes n = 0 and n = 1, and always supercritical to mode n = -1. The flow field behind this breakdown region is unstable to the asymmetric mode disturbance (n = 1) for a finite range of wavenumbers. The calculated frequencies of the unstable disturbances are in good agreement with the frequencies obtained from the experimental measurements.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids; 23; May 1980
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  • 63
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    Publication Date: 2011-08-17
    Description: The paper discusses the Thematic Mapper (TM), a multispectral earth resources sensor that will be launched on the Landsat-D satellite. The TM will operate in a circular, near-polar orbit of 750-km altitude and will scan a swath of earth 185 km wide. One TM mirror is a moving scan mirror, active during the forward and reverse scans; the final design of this component incorporates a mirror which has the required linearity and is not influenced by structural vibration. Another TM component that presented a design difficulty was the optical metering structure which has to be thermally stable across the temperature range in the instrument's orbital environment and duty cycle.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Geoscience and Remote Sensing; GE-18; Apr. 198
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  • 64
    Publication Date: 2011-08-17
    Description: A new method of ultrasonic frequency analysis is introduced which employs frequency-tracked gated RF drive pulses rather than shock-excited broadband spikes to generate the ultrasonic waveform. The new technique, a variation of the sampled-continuous wave technique, eliminates problems associated with finite pulse widths of conventional methods. It is shown to yield correct ultrasonic wave velocity measurements of the sample irrespective of receiver gate width or position provided any portions of two successive echoes are gated simultaneously into the spectrum analyzer. The experimental observations are substantiated by a theoretical model based on the time-frequency domain formulation of ultrasonic frequency analysis.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Acoustical Society of America; vol. 67
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  • 65
    Publication Date: 2011-08-17
    Description: An inherent numerical problem associated with the fully explicit pseudospectral numerical simulation of the incompressible Navier-Stokes equation for viscous flows with no-slip walls is described. A semi-implicit scheme which circumvents this numerical difficulty is presented. In this algorithm the equation of continuity rather than the Poisson equation for pressure is solved directly. Pseudospectral formulation of the channel flow problem using Fourier series and Chebyshev polynomials expansions is given for this scheme. An example demonstrating the applicability of the method is given.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics; 35; May 1980
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  • 66
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    Publication Date: 2011-08-17
    Description: In contrast to hydrodynamic bearings, which depend for low-friction characteristics on a fluid film between the journal and the bearing surfaces, roller-element bearings employ a number of balls or rollers that roll in an annular space. The paper briefly outlines the advantages and disadvantages of roller-element bearings as compared to hydrodynamic bearings. The discussion covers bearing types, rolling friction, friction losses in rolling bearings, contact stresses, deformations, kinematics (normal and high speeds), bearing dynamics including elastohydrodynamics, load distribution, lubrication (grease, solid oil, oil-air mist), specific dynamic capacity and life, specific static capacity, and fatigue or wearout (elastohydrodynamics, wear). Rolling bearing wear factor as a function of operating environment is plotted and discussed.
    Keywords: MECHANICAL ENGINEERING
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  • 67
    Publication Date: 2011-08-17
    Description: The magnitudes of real-gas effects on flat-plate turbulent boundary layer simulations in a cryogenic nitrogen wind tunnel are investigated in order to determine the validity of the method used by Inger (1979) to estimate real-gas effects. Boundary layer solutions for real gases, ideal gases with a specific heat ratio of 1.6 and ideal diatomic gases (specific heat ratio 1.4) were obtained for the worst case conditions of maximum stagnation pressure (9 atm), minimum stagnation temperature (120 K) and Mach number of 1.2. Calculated boundary layer parameters such as friction coefficient and displacement thickness are shown to agree closely for the real gas and the ideal diatomic gas (specific heat ratio 1.4), while the ideal gas solution used by Inger is shown to differ from the real-gas values considerably. Results indicate that real-gas effects on a flat-plate turbulent boundary layer simulation in a cryogenic nitrogen tunnel are insignificant, and suggest the unlikelihood of the large real-gas effects reported by Inger for turbulent boundary layer shock interactions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Aircraft; 17; Apr. 198
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  • 68
    Publication Date: 2011-08-17
    Description: A review of various types of seal locations in a gas turbine engine and the significance of wear for each type are presented. Material selection guidelines and the PV (contact pressure times sliding velocity) criteria for seal materials are discussed, and examples of wear mechanisms in positive contact seals are given. It is suggested that improved wear, erosion, and oxidation resistant materials will be required for improved seal durability; finally, a correlation is proposed between wear characteristics and a factor that includes material strength, ductility, specific heat and hot-working temperature to attain low porosity metallic gas path seal materials.
    Keywords: MECHANICAL ENGINEERING
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  • 69
    Publication Date: 2011-08-17
    Description: The paper presents the water depth measurement using an airborne pulsed neon laser system. The results of initial base-line field test results of NASA airborne oceanographic lidar in the bathymetry mode are given, with water-truth measurements of depth and beam attenuation coefficients by boat taken at the same time as overflights to aid in determining the system's operational performance. The nadir-angle tests and field-of-view data are presented; this laser bathymetry system is an improvement over prior models in that (1) the surface-to-bottom pulse waveform is digitally recorded on magnetic tape, and (2) wide-swath mapping data may be routinely acquired using a 30 deg full-angle conical scanner.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 19; Mar. 15
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  • 70
    Publication Date: 2017-10-02
    Description: The use of inviscid-viscous interaction methods for the case of radial or mixed-flow cascade diffusers is discussed. A literature review of investigations considering cascade flow-field prediction by inviscid-viscous iterative computation is given. Cascade aerodynamics in the third blade row of a multiple-row radial cascade diffuser are specifically investigated.
    Keywords: MECHANICAL ENGINEERING
    Type: AGARD Centrifugal Compressors, Flow Phenomena and Performance; 11 p
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  • 71
    Publication Date: 2017-10-02
    Description: The capabilities of large eddy simulation in the prediction and analyses of wall-bounded turbulent shear flows are demonstrated. The dynamical equations for large scale field motions are derived. The computational grid network is described and its relation to the observed physical length scales in the flow are discussed. Some aspects of the mechanics and structure of the flow are examined both in the vicinity of the wall and in regions away from the wall. An attempt is made to correlate numerical results with laboratory observations. Other significant observations and conclusions are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AGARD Turbulent Boundary Layers; 18 p
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  • 72
    Publication Date: 2017-10-02
    Description: Two methods of turbulence computation are discussed in terms of their basic simularities. It is shown that the two methods are interrelated and that each can gain from advances in the other. The degree of success of a pair of increasingly complex Reynolds stress models to broaden their range of applicability is examined through comparison with experimental data for a variety of flow conditions. An example of a large eddy simulation is presented, compared with experimental results, and used to evaluate the models for pressure rate of strain correlation and dissipation in the Reynolds averaged equations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AGARD Turbulent Boundary Layers; 23 p
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  • 73
    Publication Date: 2017-10-02
    Description: A computer code for the evaluation and/or optimization of the predicative potential of second order turbulent closure models in simple two dimensional flow configurations is discussed. A procedure for the numerical solution of the steady constant property Navier-Stokes equations are described together with algebraic, one dimensional and two dimensional equations of turbulence closure models. Four turbulence models are compared with several sets of experimental data. The effects of initial conditions and boundary conditions are also described. The effects of purely numerical parameters, such as mesh size, boundary locations, and convergence criteria are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AGARD Turbulence Boundary Layers; 16 p
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  • 74
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    Publication Date: 2016-03-09
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Surface-Tension Gradient Induced Flows at Reduced Gravity; 19 p
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  • 75
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The DSN noise adding radiometer (NAR) measurement accuracy is analyzed. The NAR capability is part of the precision power monitor function recently introduced in the DSN. The potential system noise temperature measurement accuracy is estimated to be about 1.5% with the 1 kelvin noise diode. Performance verification requires comparison noise temperature measurements with the manual Y factor method and routine monitoring of critical elements in the NAR system such as system linearity and noise diode calibration. A technique is presented to calibrate and reduce the effects of the receiving system nonlinearity. Unsatisfactory performance or degradation of these critical NAR elements would require appropriate system upgrading.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: The Telecommun. and Data Acquisition Rept.; p 98-106
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  • 76
    Publication Date: 2016-06-07
    Description: Rotor support systems interaction with parametric excitation is considered for both unequal principal shaft stiffness (generators) and offset disc rotors (ventilators). Instability regions and types of instability are computed in the first case, and parametric resonances in the second case. Computed and experimental results are compared for laboratory machine models. A field case study of parametric vibrations in industrial ventilators is reported. Computed parametric resonances are confirmed in field measurements, and some industrial failures are explained. Also the dynamic influence and gyroscopic effect of supporting structures are shown and computed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 383-400
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  • 77
    Publication Date: 2016-06-07
    Description: Fluid forces on a centrifugal impeller, whose rotating axis whirls with a constant speed, were calculated by using unsteady potential theory. Calculations were performed for various values of whirl speed, number of impeller blades and angle of blades. Specific examples as well as significant results are given.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 317-328
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  • 78
    Publication Date: 2016-06-07
    Description: The role of fluid forces acting on the blades of an axial turborotor with regards to whirling was analyzed. The dynamic equations were formulated for the coning mode of an overhung rotor. The exciting forces due to the motion were defined through a set of rotor stability derivatives, and analytical expressions of the aerodynamic contributions were found for the case of small mean stream deflection, high solidity and equivalent flat plate cascade. For a typical case, only backward whirl was indicated when the phase shifting of the rotor wake effect was ignored. A parametric study of the dynamic stability boundary reveals that a reduction in blade stagger angle, mass flow rate, fluid density and an increase in stiffness and external damping are all inductive for improved stability.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 267-284
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  • 79
    Publication Date: 2016-06-07
    Description: A simple two dimensional model for calculating the rotordynamic effects of the impeller force in centrifugal compressors and pumps is presented. It is based on potential flow theory with singularities. Equivalent stiffness and damping coefficients are calculated for a machine with a vaneless volute formed as a logarithmic spiral. It is shown that for certain operating conditions, the impeller force has a destablizing effect on the rotor.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 249-265
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  • 80
    Publication Date: 2016-06-07
    Description: The system components, performance, and calibration of two element radio interferometer operating at 8.33 mm wavelength are discussed. The interferometer employs a 5.5 m and a 3 m diameter antenna on an east-west baseline of 60 or 120 m, yielding fringe spacings at transit of 28 or 14 in. respectively. The broad intermediate frequency bandpass of 100 to 350 MHz and the system noise temperature of 500 K provide high sensitivity for the measurement of continuum sources. The interferometer has been used for high resolution studies of the planets and the Sun, and it is currently being adapted to study solar flare emissions at high spatial and time resolution.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: The Telecommun. and Data Acquisition Rept.; p 1-8
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  • 81
    Publication Date: 2016-06-07
    Description: The effect of working fluid on the dynamics of an impeller with radial vanes was investigated. The impeller was supported vertically from a very flexible quill shaft in order to produce a low critical speed, and to allow the fluid dynamic effects on the impeller to predominate. The shaft was supported from ball bearings, so that there was no possibility of oil whip from fluid film bearings as a destabilizing influence. The impeller was run both in the atmosphere, and submerged in working fluids contained in a cylindrical housing, open at the top. Variable speed was obtained with a dc gearmotor drive unit. The speed was measured with a proximity probe pulse tachometer and electronic digital counter.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 361-367
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  • 82
    Publication Date: 2016-06-07
    Description: A symmetric 3 mass rotor supported on hydrodynamic bearings is described. An approximate method of representing finite bearings is used to calculate bearing forces. As the method sums forces from a number of independent circular lobes lemon 3 and 4 lobe bearings are taken into account. The calculations are based on an axial groove bearing. Linear analysis precedes nonlinear simulation of some unstable conditions. The demonstration of small limit cycles suggests that necessarily flexible rotors e.g., helicopter tail rotors, may be practical without either tilt pad bearings or external dampers.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 331-343
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  • 83
    Publication Date: 2016-06-07
    Description: An unstable asynchronous vibration problem in a high pressure centrifugal compressor and the remedial actions against it are described. Asynchronous vibration of the compressor took place when the discharge pressure (Pd) was increased, after the rotor was already at full speed. The typical spectral data of the shaft vibration indicate that as the pressure Pd increases, pre-unstable vibration appears and becomes larger, and large unstable asynchronous vibration occurs suddenly (Pd = 5.49MPa). A computer program was used which calculated the logarithmic decrement and the damped natural frequency of the rotor bearing systems. The analysis of the log-decrement is concluded to be effective in preventing unstable vibration in both the design stage and remedial actions.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 109-118
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  • 84
    Publication Date: 2016-06-07
    Description: The summary of a complete analytical design evaluation of an existing parallel flow compressor is presented and a field vibration problem that manifested itself as a subsynchronous vibration that tracked at approximately 2/3 of compressor speed is reviewed. The comparison of predicted and observed peak response speeds, frequency spectrum content, and the performance of the bearing-seal systems are presented as the events of the field problem are reviewed. Conclusions and recommendations are made as to the degree of accuracy of the analytical techniques used to evaluate the compressor design.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 45-63
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  • 85
    Publication Date: 2016-06-07
    Description: Basic design criteria are given for an ion mass spectrometer for use in studying magnetospheric ion populations. The proposed instrument is composed of an electrostatic analyzer followed by a magnetic spectrometer and simultaneously measures the energy per unit and mass per unit charge of the ion species. An electromagnet is used for momentum analysis to extend the operational energy range over a much wider domain than is possible with the permanent magnets used in previous flights. The energetic ion source regions, ion energization mechanisms, field line tracing, coordinated investigations, and orbit considerations are discussed and operations of the momentum analyzer and of the electrostatic energy analyzer are examined.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Marshall Space Flight Center Space Plasma Phys. Active Expt.; p 91-106
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  • 86
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    Publication Date: 2016-06-07
    Description: The high frequency part of the waves in space plasmas system, WISP/HF, is a flexible shuttle Spacelab instrument for transmitting, receiving, and processing signals in the 0.3 to 30 MHz range. It permits a wide range of plasma wave experiments in the ionosphere including studies of the transmitting antenna, fundamentals of electromagnetic (EM) and electrostatic (ES) waves in magnetoplasmas, instabilities and nonlinearities, and remote sounding of ionospheric structure. Collaborative investigations involving other WISP equipment (e.g., antenna and propagation studies with the WISP/VLF system) or other Spacelab facilities (e.g., beam plasma interactions using charged particle guns) are envisaged. A few specific examples illustrate the relevance of WISP/HF to current scientific interest. The overall goal is to help build a comprehensive understanding of plasmaspheric wave physics through group studies.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Marshall Flight Center Space Plasma Phys. Active Expt.; p 173-184
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  • 87
    Publication Date: 2016-06-07
    Description: Analytical modeling efforts and clear-air ground test results of a transportation-cooled nosetips (TCNT) design are presented. The discrete water injection platelet TCNT described was conceived and created to achieve the performance requirements for severe reentry vehicle trajectories. Thermal performance computer modeling techniques, combing both local heat blockage and boundary layer recovery enthalpy reduction are outlined.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Johnson Space Center The 11th Space Simulation Conf.; p 331-346
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  • 88
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The need for clean, oil free space simulation systems has demanded the development of large, clean pumping systems. The assurance of optically dense liquid nitrogen baffles over diffusion pumps prevents backstreaming to a large extent, but does not preclude contamination from accidents or a control failure. Turbomolecular pumps or ion pumps achieve oil free systems but are only practical for relatively small chambers. Large cryopumps were developed and checked out which do achieve clean pumping of very large chambers. These pumps can be used as the original pumping system or can be retrofitted as a replacement for existing diffusion pumps.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Johnson Space Center The 11th Space Simulation Conf.; p 71-78
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  • 89
    Publication Date: 2016-06-07
    Description: The occurrence of oil whirl instability in rigid and flexible rotor systems was investigated. The effect of various bearing parameters on the oil whirl frequency and amplitude of rigid and flexible shafts supported on fluid film bearings was also studied.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 345-357
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  • 90
    Publication Date: 2016-06-07
    Description: The quasisteady computer analysis of the perturbated centrifugal impeller passage flow was reviewed. A total of 115 stage calculations were used to define the fluid damping coefficient, delta sub fluid. Results indicate that the average total damping coefficient per stage needed for stability is delta sub total 1.85.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery p285-302 (SEE N80-29706 20-37)
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  • 91
    Publication Date: 2016-06-07
    Description: The hydraulic forces caused by annular pressure seals were investigated. The measured inlet and exit loss coefficients of the flow through the seals were much smaller than the conventional values. The results indicate that the damping coefficient and the inertia coefficient of the fluid film in the seal are not affected much by the rotational speed or the eccentricity of the rotor, though the stiffness coefficient seemed to be influenced by the eccentricity.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery p213-225 (SEE N80-29706 20-37)
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  • 92
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2016-06-07
    Description: An analysis is presented to calculate damping in ring seals for a compressible fluid. Results show that damping in tapered ring seals (optimized for stiffness) is less than that in straight bore ring seals for the same minimum clearance. Damping in ring seals can promote fractional frequency whirl and can, thus, be detrimental. Thus, tapered seals can benefit rotor and seal stability by having lower damping as well as higher stiffness. Use of incompressible results leads to large errors.
    Keywords: MECHANICAL ENGINEERING
    Type: Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 169-188
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  • 93
    Publication Date: 2016-06-07
    Description: Lateral and torsional vibration data obtained on a centrifugal compressor train which had shaft instabilities and gear failures is examined. The field data verifies that the stability of centrifugal compressors can be adversely affected by coincidence of torsional natural frequencies with lateral instability frequencies. The data also indicates that excitation energy from gear boxes can reduce stability margins if energy is transmitted either laterally or torsionally to the compressors. The lateral and torsional coupling mechanisms of shaft systems is discussed. The coupling mechanisms in a large industrial compressor train are documented and the potential effect on rotor stability is demonstrated. Guidelines are set forth to eliminate these potential problems by minimizing the interaction of torsional and lateral responses and their effect on rotor stability.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 15-34
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  • 94
    Publication Date: 2016-06-07
    Description: A system capable of making measurements of fluctuating atmospheric density is described. Spatial scales required in assessing the quality of coherent radiation propagation are discussed. The special sensors, aircraft installation, data reduction procedures, and other special requirements necessary to obtain meaningful atmospheric turbulence data are also described. The spectral distribution of density fluctuation are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Ames Res. Center Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation from Aircraft; p 493-514
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  • 95
    Publication Date: 2016-06-07
    Description: Optical degradations of aircraft turbulent boundary layers with shear layers generated by aerodynamic fences are analyzed. A collimated 2.5 cm diameter helium-neon laser (0.63 microns) traversed the approximate 5 cm thick natural aircraft boundary layer in double pass via a reflective airfoil. In addition, several flights examined shear layer-induced optical degradation. Flight altitudes ranged from 1.5 to 12 km, while Mach numbers were varied from 0.3 to 0.8. Average line spread function (LSF) and Modulation Transfer Function (MTF) data were obtained by averaging a large number of tilt-removed curves. Fourier transforming the resulting average MTF yields an LSF, thus affording a direct comparison of the two optical measurements. Agreement was good for the aerodynamic fence arrangement, but only fair in the case of a turbulent boundary layer. Values of phase variance inferred from the LSF instrument for a single pass through the random flow and corrected for a large aperture ranged from 0.08 to 0.11 waves (lambda = .63 microns) for the boundary layer. Corresponding values for the fence vary from 0.08 to 0.16 waves. Extrapolation of these values to 10.6 microns suggests negligible degradation for a CO2 laser transmitted through a 5 cm thick, subsonic turbulent boundary layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Ames Res. Center Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation from Aircraft; p 397-414
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  • 96
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2016-06-07
    Description: A chronological overview of aero-optics test flights is presented highlighting the objectives and conclusions from the tests. Flight tests performed in coordination with the PRESS reentry observation missions and the ALL Cycle 2 laser propagation and tracking demonstrations are described addressing the identification and quantification of distortion phenomena. Finally, current aero-optics flight investigations of an atmospheric turbulence probe are briefly discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Ames Res. Center Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation from Aircraft; p 363-395
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  • 97
    Publication Date: 2016-06-07
    Description: Analytical models for optical phase distortion due to compressible flow over a laser turret are developed. Phase distortion is calculated for both blunt and small perturbation turrets. For the blunt turret, the Janzen-Rayleigh technique is used to determine the flow field. Phase distortions of 2.2 wavelengths at 3.8 microns are calculated for the blunt turret. For small perturbation turrets, a versatile analytical model is developed for a turret on a fuselage with circular cross section. With a two dimensional Fourier series representation of the turret, any shape can be considered. Both subsonic and supersonic flows can be calculated. Phase distortions of 1.2 wavelengths at 3.8 microns are calculated for one turret at high subsonic Mach number. In addition to being of value for laser turrets, the methods are applicable to reconnaissance aircraft using photographic equipment and cruise missiles using celestial navigation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Ames Res. Center Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation from Aircraft; p 287-325
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  • 98
    Publication Date: 2016-06-07
    Description: The aero-optical distortions due to invisid flow effects over airborne laser turrets is investigated. Optical path differences across laser turret apertures are estimated from two data sources. The first is a theoretical study of main flow effects for a spherical turret assembly for a Mach number (M) of 0.6. The second source is an actual wind tunnel density field measurement on a 0.3 scale laser turret/fairing assembly, with M = 0.75. A range of azimuthal angles from 0 to 90 deg was considered, while the elevation angle was always 0 deg (i.e., in the plane of the flow). The calculated optical path differences for these two markedly different geometries are of the same order. Scaling of results to sea level conditions and an aperture diameter of 50 cm indicated up to 0.0007 cm of phase variation across the aperture for certain forward look angles and a focal length of F = -11.1 km. These values are second order for a 10.6 micron system.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Ames Res. Center Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation Aircraft (SEE N80-25588 16-34)
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  • 99
    Publication Date: 2016-06-07
    Description: The design requirements of the polarimeter were established by the scientific optical objectives of the experiment to be launched aboard the Solar Max Mission which will study active solar regions. The polarization of the light is accomplished by a rotating magnesium fluoride quarter wave plate. The quarter wave plates are rotated in 22 1/2 degree steps about an axis coincidental with the light beam. As the light beam passes through the wave plate, the transformation that occurs can be expressed by mathematical equations. By having the wave plates calibrated, the data obtained from solar flares can be analyzed and meaningful information provided to the investigators. The polarimeter has two wave plates with different optical characteristics to provide both redundancy and versatility. A four mirror polarizer was added behind one wave plate to provide additional polarization. The mechanical design, testing, and operation of the polarimeter for the high resolution ultraviolet spectrometer/polarimeter are described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Langley Res. Center Proc. of the 14th Aerospace Mech. Symp.; p 303-310
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  • 100
    Publication Date: 2016-06-07
    Description: A concept in manipulator development to overcome the 'weak wrist syndrome', a triple-axis common-pivot arm wrist (TACPAW), is presented. It contains torque motors for actuation, tachometers for measuring rate, and resolvers for position measurements. Furthermore, it provides three degrees of freedom, i.e., pitch, yaw, and roll, in a single manipulator joint. The advantages of this development are increased strength, compactness, and simplification of controls. Designed to be compatible with the protoflight manipulator arm, the joints of TACPAW are back-driveable with + or - 45 deg rotation in pitch, + or - 45 deg in yaw and continuous roll in either direction while delivering 20.5 N-m (15 ft-lb) torque in each of the three movements.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Langley Res. Center Proc. of the 14th Aerospace Mech. Symp.; p 111-124
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