Echo III - The study of electric and magnetic fields with conjugate echoes from artificial electron beams injected into the auroral zone ionosphere
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Hendrickson, R. A.↗
SEARCH · Engineering Papers
Results for “field study”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Aviation safety research and transportation/hazard avoidance and elimination
Data collected by the Scanning Laser Doppler Velocimeter System (SLDVS) was analyzed to determine the feasibility of the SLDVS for monitoring aircraft wake vortices in an airport environment. Data were collected on atmospheric vortices and analyzed. Over 1600 landings were monitored at Kennedy International Airport and by the end of the test period 95 percent of the runs with large aircraft were producing usable results in real time. The transport was determined in real time and post analysis using algorithms which performed centroids on the highest amplitude in the thresholded spectrum. Making use of other parameters of the spectrum, vortex flow fields were studied along with the time histories of peak velocities and amplitudes. The post analysis of the data was accomplished with a CDC-6700 computer using several programs developed for LDV data analysis.
Sonnenschein, C. M.↗
Measurements on wave propagation characteristics of spiraling electron beams
Dispersion characteristics of cyclotron-harmonic waves propagating on a neutralized spiraling electron beam immersed in a uniform axial magnetic field are studied experimentally. The experimental setup consisted of a vacuum system, an electron-gun corkscrew assembly which produces a 110-eV beam with the desired delta-function velocity distribution, a measurement region where a microwave signal is injected onto the beam to measure wavelengths, and a velocity analyzer for measuring the axial electron velocity. Results of wavelength measurements made at beam currents of 0.15, 1.0, and 2.0 mA are compared with calculated values, and undesirable effects produced by increasing the beam current are discussed. It is concluded that a suitable electron beam for studies of cyclotron-harmonic waves can be generated by the corkscrew device.
Singh, A.↗
Vortices induced in a stagnation region by wakes - Their incipient formation and effects on heat transfer from cylinders
Horseshoe-like vortices, induced by wakes in the stagnation region of bluff bodies, are proposed as an efficient mechanism for augmentation of convective heat transfer. The vortex 'flow module' induced by single or multiple wakes, which had not been observed previously, was first documented and the resulting flow field was studied using various visualization techniques and hot-wire anemometry. In an attempt to understand the driving force behind this flow module, the conditions at which incipient formation of the vortices occurs were investigated. Existence of such a threshold is essential and was hitherto an open question in analytical studies of stability of flow in stagnation region. Finally, effects of the flow module on heat transfer from a cylinder were measured.
Nagib, H. M.↗
Computer solutions for studying correlations between solar magnetic fields and Skylab X-ray observations
A method is described which correlates the NASA-Marshall Space Flight Center (MSFC) Image Data Processing System (IDAPS) and MSFC magnetograph data to X-ray and H-alpha observations from the Skylab mission. Solutions of Laplace's equation in three dimensions, based on the magnetograph data, are convolved with observed X-ray and H-alpha regions. Matched filtering (template matching) provides a best fit of the observed X-ray regions to the computed total magnetic vector magnitude between 10,000 and 15,000 km above the photosphere.
Teuber, D.↗
Reduction of fan noise in an anechoic chamber by reducing chamber wall induced inlet flow disturbances
The difference between the flight and ground static noise of turbofan engines presents a significant problem in engine noise testing. The additional noise for static testing has been attributed to inlet flow disturbances or turbulence interacting with the fan rotor. In an attempt to determine a possible source of inflow disturbances entering fans tested in the Lewis Research Center anechoic chamber, the inflow field was studied using potential flow analysis. These potential flow calculations indicated that there was substantial flow over the wall directly behind the fan inlet that could produce significant inflow disturbances. Fan noise tests were run with various extensions added to the fan inlet to move the inlet away from this backwall and thereby reduce the inlet flow disturbances. Significant noise reductions were observed with increased inlet length. Over 5 db reduction of the blade passage tone sound power level was observed between the shortest and longest inlets at 90% fan speed and the first overtone was reduced 9 db. High frequency broadband noise was also reduced.
Dittmar, J. H.↗
Vibrational excitation of H2 in intense ultraviolet fluxes
The vibrational excitation of H2 in intense ultraviolet radiation fields is studied. The radiative cascade through bound levels of the ground electronic state, following absorption of Lyman- and Werner-band photons, is modified to include effects of 'multiple pumping' and direct photodissociation from the high vibrational levels. Although the column densities in the excited vibrational levels produced by UV pumping appear too low to explain the recently observed Orion quadrupole emission lines, it is suggested that the far-red lines in the (3-0) and (4-0) bands, produced by UV pumping from O stars near dense molecular clouds, may be detectable.
Shull, J. M.↗
Reduction of fan noise in an anechoic chamber by reducing chamber wall induced inlet flow disturbances
The difference between the flight and ground static noise of turbofan engines has been identified as a significant problem in engine noise testing. The additional noise for static testing has been attributed to inlet flow disturbances or turbulence interacting with the fan rotor. In an attempt to determine a possible source of inflow disturbances entering fans tested in the Lewis Research Center anechoic chamber the inflow field was studied using potential flow analysis. These potential flow calculations indicated that there was substantial flow over the wall directly behind the fan inlet that could produce significant inflow disturbances. Fan noise tests were run with various extensions added to the fan inlet to move the inlet away from this backwall and thereby reduce the inlet flow disturbances. Significant noise reductions were observed with increased inlet length. Over 5 dB reduction of the blade passage tone sound power level was observed between the shortest and longest inlets at 90% fan speed and the first overtone was reduced 9 dB. High frequency broadband noise was also reduced.
Dittmar, J. H.↗
A Landsat Agricultural Monitoring Program
The paper discusses the Landsat Agricultural Monitoring Program which was developed to identify, observe, and evaluate alarm conditions influencing Iowa corn production in 1976. Used in conjunction with climatic and field reports, studies were made of crop development, crop alarms (such as heavy rainfall, hail, tornadoes, and drought) and estimated crop yield.
Aaronson, A. C.↗
Comment on 'Search for the magnetic neutral line in the near-earth plasma sheet. II - Systematic study of Imp 6 magnetic field observations' by A. T. Y. Liu, C.-I. Meng, and S.-I. Akasofu
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Caan, M. N.↗
An Experimental Investigation of Forced Mixing of a Turbulent Boundary Layer in an Annular Diffuser
The forced mixing process of a turbulent boundary layer in an axisymmetric annular diffuser using conventional wing-like vortex generators was studied. Flow field measurements were made at four axial locations downstream of the vortex generators. At each axial location, a total of 25 equally spaced profiles were measured behind three consecutive vortex generators which formed two pairs of vortex generators. Hot film anemometry probes measured the boundary layer turbulence structure at the same locations where pressure measurements were made. Both single and cross film probes were used. The diffuser turbulence data was teken only for a nominal inlet Mach number of 0.3. Three vortex generator configurations were tested. The differences between configurations involved changes in size and relative vortex generator positions. All three vortex generator configurations tested provided increases in diffuser performance. Distinct differences in the boundary layer integral properties and skin friction levels were noted between configurations. The axial turbulence intensity and Reynolds stress profiles measured displayed similarities in trends but differences in levels for the three configurations.
Shaw, R. J.↗
Array Automated Assembly Task for the Low Cost Solar Array Project, Phase 2
Using silk screened evaporated and sputtered Al as the metal source, the formation of Al back surface fields was studied. The most satisfactory results were those obtained with the sputtered A1 and in which open circuit voltages (V sub oc) of 0.585 v (12 ohm cm FZ silicon) were achieved. The ultrasonic interconnect process is discussed. The process is shown to be satisfactory, but increased pull-strength may be obtained if some form of sintering is carried out on the metallized contacts. Plasma etching is shown to be feasible as a replacement for wet chemical cleaning prior to diffusion. Initial results on cells prepared by using electroless Pd/Ni plus either electroplated Ag or Cu show slightly poor performance than cells with the baseline evaporated Ti/Pd/Ag system. A mask designed for the 1.6 x 7.0 cm and 2.0 x 7.0 cm cells is described. This mask has a lower area coverage and total lower resistive loss than the previous mask design. It is also shown that the cell width should not exceed 2.0 - 3.0 cm for optimum efficiency.
Campbell, R. B.↗
The split comets - Gravitational interaction between the fragments
The gravitational interaction between two fragments of a split comet nucleus in the sun's gravitational field is studied by means of the n-body computer program of Schubart and Stumpff (1966). Patterns of interactions are found for combinations of the masses, mass ratios and densities of the parent nucleus and the fragment, directions of separation, and regions of separation for nucleus separations occurring at perihelion and at true anomalies of +90 deg and -90 deg. It has been found that solar gravitational effects become noticeable about 0.5 to 1 day after separation at perihelion, and about 1 to 2 days after separation at twice the perihelion distance. Mass ratios and bulk density do not appreciably affect the appearance of the calculated trajectories. The calculated patterns vary from zero to very high inclinations, from a prograde to a retrograde sense of motion, and from escape of the companion to its pursuance of periodic quasi-stable orbits around the principal nucleus, terminated in some cases by collision of the fragments.
Sekanina, Z.↗
Magnetic field directional discontinuities. 2: Characteristics between 0.46 and 1.0 AU
The characteristics of directional discontinuities (DD's) in the interplanetary magnetic field are studied using data from the Mariner 10 primary mission between 1.0 and 0.46 AU. Statistical and visual survey methods for DD identification resulted in a total of 644 events. Two methods were used to estimate the ratio of the number of tangential discontinuities (TD's) to the number of rotational discontinuities (RD's). Both methods show that the ratio of TD's to RD's varied with time and decreased with decreasing radial distance. A decrease in average discontinuity thickness of approx. 40 percent was found between 1.0 and 0.72 AU and approx. 54 percent between 1.0 and 0.46 AU, independent of type (TD or RD). This decrease in thickness for decreasing r is in qualitative agreement with Pioneer 10 observations between 1 and 5 AU. When the individual DD thickness are normalized with respect to the estimated local proton gyroradius (RA sub L), the average thickness at the three locations is nearly constant, 43 + or - 6 R sub L. This also holds true for both RD's and TD's separately. Statistical distributions of other properties, such as normal components and discontinuity plane angles, are presented.
Lepping, R. P.↗
In situ correlative measurements for the ultraviolet differential absorption lidar and the high spectral resolution lidar air quality remote sensors: 1980 PEPE/NEROS program
In situ correlative measurements were obtained with a NASA aircraft in support of two NASA airborne remote sensors participating in the Environmental Protection Agency's 1980persistent elevated pollution episode (PEPE) and Northeast regional oxidant study (NEROS) field program in order to provide data for evaluating the capability of two remote sensors for measuring mixing layer height, and ozone and aerosol concentrations in the troposphere during the 1980 PEPE/NEROS program. The in situ aircraft was instrumented to measure temperature, dewpoint temperature, ozone concentrations, and light scattering coefficient. In situ measurements for ten correlative missions are given and discussed. Each data set is presented in graphical and tabular format aircraft flight plans are included.
Gregory, G. L.↗
Plasma waves in a relativistic, strongly anisotropic plasma propagated along a strong magnetic field
The dispersion properties of plasma waves in a relativistic homogeneous plasma propagated along a strong magnetic field are studied. It is shown that the non-damping plasma waves exist in the frequency range omega sub p or = omega or = omega sub L. The values of omega sub p and omega sub L are calculated for an arbitrary homogeneous relativistic function of the particle distribution. In the case of a power ultrarelativistic distribution, it is shown that, if the ultrarelativistic tail of the distribution drops very rapidly, slightly damping plasma waves are possible with the phase velocity (omega/K)c.
Onishchenko, O. G.↗
Program of Research in Aeronautics
A prospectus of the educational and research opportunities available at the Joint Institute for Advancement of Flight Sciences, operated at NASA Langley Research Center in conjunction with George Washington University's School of Engineering and Applied Sciences is presented. Requirements of admission to various degree programs are given as well as the course offerings in the areas of acoustics, aeronautics, environmental modelling, materials science, and structures and dynamics. Research facilities for each field of study are described. Presentations and publications (including dissertations and theses) generated by each program are listed as well as faculty members visting scientists and engineers.
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A comparative study of nonreflecting far-field boundary condition procedures for unsteady transonic flow computation
Various nonreflecting far-field boundary condition procedures are compared by implementing them in the computer code LTRAN2. This code solves the implicit finite-difference representation of the small-disturbance equations for transonic flows about airfoils. The first- and second-approximate nonreflecting conditions, as proposed by Engquist and Majda, are compared with the condition derived from the full-characteristic equation. The far-field boundary conditions and the description of the algorithm for implementing these conditions in LTRAN2 are discussed. Various cases are computed and compared with results from the older, more conventional procedures. One concludes that the full-characteristic equation produces the most effective results, thus allowing the far-field boundary to be located closer to the airfoil; this decreases the computer time required to obtain the solution because fewer mesh points are required.
Kwak, D.↗