Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ASYMMETRY”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Viscous flow over spinning cones at angle of attack.

A numerical finite-difference method is developed for evaluating the Magnus coefficients on spinning cones in laminar flow. The merged layer, the strong interaction region, and the downstream boundary layer are all considered. The numerical method is a predictor-corrector scheme developed for three-dimensional flows with or without crossflow diffusion. This method is particularly useful in problems in which a symmetry plane does not exist. Several contributions to the Magnus force and moments are considered. These include asymmetries in displacement thickness, centrifugal force and crossflow shear, and the effects of crossflow separation and vortex formation. Comparisons are made with experimental data and other analyses.

Lin, T. C.↗
NASA NTRS1973

Induced magnetosphere of the moon. II - Experimental results from Apollo 12 and Explorer 35.

The asymmetric lunar electromagnetic induction theory of Schubert et al. (1973) is tested by using data from the Apollo 12 Lunar Surface Magnetometer and from the Ames magnetometer on Explorer 35. The comparison of data and theory shows that the moon displays an induction asymmetry due to the flow of the solar wind and the formation of the diamagnetic cavity on the darkside. It is inferred that the induced field forms a magnetospheric-like configuration, with the field confined mostly to the crust of the moon. Although the magnetospheric spectrum is time-dependent for all frequencies examined, the distance traveled by the solar wind is so large that a quasi-static magnetospheric configuration can be assumed. The differential power spectrum of the interplanetary magnetic field that excites the moon is compared with the resulting induction spectrum, which has a linear differential power frequency dependence over the frequency range from .0002 to .02 Hz, falling off on either side of these limits. The integrated power in this band is about 5 gamma squared for the interplanetary field local north-south component and about 12 gamma squared for the induced spectrum of this component on the lunar surface.

Smith, B. F.↗
NASA NTRS1973

High-latitude proton precipitation and light ion density profiles during the magnetic storm initial phase.

Measurements of precipitating protons and light ion densities by experiments on Ogo 4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause, up to latitudes greater than 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3-keV and 23.8-keV protons is less than about 1 deg, compared with a 3.6-deg separation that has been computed by using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons are injected in predawn hours, widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than 7 keV drift eastward, whereas the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

Burch, J. L.↗
NASA NTRS1973

Photoionization from excited states of helium

The cross sections for photoionization from the 2 1S, 2 3S, 2 1P and 2 3P excited states of helium are calculated for photoelectron energies below the n = 2 threshold of He(+) using Hylleraas bound state wave functions and 1s-2s-2p close coupling final state wave functions. The resonant structures associated with the lowest-lying 1S, 1P, 3P, and 1D autoionizing states of helium are found to be characterized by large values of the line profile parameter q. The cross sections and the photoelectron angular distribution asymmetry parameters for the P-states are calculated for various polarization states of the target atom and the incident photon. Experiments which would lead to the separate determinations of the S- and D- wave partial photoionization cross sections are discussed.

Jacobs, V. L.↗
NASA NTRS1973

Quantitative magnetospheric models derived from spacecraft magnetometer data

Quantitative models of the external magnetospheric field were derived by making least-squares fits to magnetic field measurements from four IMP satellites. The data were fit to a power series expansion in the solar magnetic coordinates and the solar wind-dipole tilt angle, and thus the models contain the effects of seasonal north-south asymmetries. The expansions are divergence-free, but unlike the usual scalar potential expansions, the models contain a nonzero curl representing currents distributed within the magnetosphere. Characteristics of four models are presented, representing different degrees of magnetic disturbance as determined by the range of Kp values. The latitude at the earth separating open polar cap field lines from field lines closing on the dayside is about 5 deg lower than that determined by previous theoretically-derived models. At times of high Kp, additional high latitude field lines are drawn back into the tail.

Mead, G. D.↗
NASA NTRS1973

Responses to rotating linear acceleration vectors considered in relation to a model of the otolith organs

Human subjects were exposed to a linear acceleration vector that rotated in the transverse plane of the skull without angular counterrotation. Lateral eye movements showed a sinusoidal change in slow phase velocity and an asymmetry or bias in the same direction as vector rotation. A model is developed that attributes the oculomotor response to otolithic mechanisms. It is suggested that the bias component is the manifestation of torsion of the statoconial plaque relative to the base of the utricular macula and that the sinusoidal component represents the translational oscillation of the statoconia. The model subsumes a hypothetical neural mechanism which allows x- and y-axis accelerations to be resolved. Derivation of equations of motion for the statoconial plaque in torsion and translation, which take into account forces acting in shear and normal to the macula, yield estimates of bias and sinusoidal components that are in qualitative agreement with the diverse experimental findings.

Benson, A. J.↗
NASA NTRS1974

Effect of inertia properties on attitude stability of nonrigid spin-stabilized spacecraft

The phenomenon of energy dissipation in spinning spacecraft is discussed with particular reference to its dependence on spacecraft inertia properties. Specific dissipation mechanisms are identified. The effect of external environmental factors on spin stability is also discussed. Generalized curves are presented relating system stability to the principal inertia ratio for various forms of energy dissipation. Dual-spin systems and the effect of lateral inertia asymmetry are also reviewed.

Lang, W. E.↗
NASA NTRS1973

Sonic boom analysis for high altitude flight at high Mach number

Numerical programs are presented which take into account the nonlinear effects of high Mach number, the entropy change across the shock, the entropy and enthalpy variations in the atmospheric layer and the gravitational effect. Extension of the programs for the axisymmetric problems to handle nonaxisymmetric terms is described. The asymmetry can be caused by the geometry of the body, the lift and also the fact that the variations in the atmospheric layer are two-dimensional. Numerical results demonstrating the influences of these effects and comparison with existing approximate theories are presented.

Ferri, A.↗
NASA NTRS1973

The effect of Fe I absorption on the Mg II emission at 2795 A in alpha Orionis

The Fe I absorption line at 2795.01 A is derived from the observations of Mg II resonance emission in alpha Orionis by Kondo et al (1972). A spectrum is synthesized, including Mg II emission and self-absorption and also Fe I absorption, which accounts for the observed asymmetry in the Mg II 2795.5 line and for the discrepancy between the theoretical and observed intensity ratios of the two Mg II lines. The astrophysical significance of this strong Fe I absorption is discussed.

Modisette, J. L.↗
NASA NTRS1973

Magnetospheric field morphology at magnetically quiet times

Review of the magnetospheric morphology, using the method of the Delta B topology, where Delta B is the difference between the observed and a reference field. It is confirmed that Delta B continuously decreases inward to close distances from the earth at all local times. Extrapolating the statistical relation between Dst at the ground and the equatorial Delta B obtained from OGO-5 near perigee, it is shown that Dst is 54 gammas, when Delta B is zero at approximately 2 to 3 earth radii. Conversely, for a magnetically quiet condition as defined by Dst = 0, the average equatorial Delta B at these distances is -45 gammas. These results demonstrate the significance of the effects of the magnetospheric equatorial current that exists even at quiet times. A preliminary study of inclination shows that the field lines on the dusk side are more stretched out than on the dawn side. A comparison of declination on both sides indicates that the bending of the field lines toward the tail is greater near dusk than near dawn. These results suggest an appreciable dawn-dusk asymmetry in the configuration of the inner magnetospheric field.

Sugiura, M.↗
NASA NTRS1973

High latitude electric fields and the modulations related to interplanetary magnetic field parameters

The meaning and characteristics of basic and average convection (i.e., electric field) patterns are described. The continuous existence of the basic convection pattern argues against treating magnetic field merging mechanisms as the fundamental cause of magnetospheric convection. However, whether related to merging or to some other mechanism, interplanetary magnetic field conditions significantly modulate the distribution, magnitudes, and boundaries of the convection pattern. A previous correlation between azimuthal angles of the interplanetary magnetic field and asymmetries in polar cap electric field distributions as seen by OGO-6 is reviewed. A new approach is taken to reveal correlations with the north-south angle and magnitude of the interplanetary field as well as additional features which correlate with the azimuthal angle. Both significant correlations and conditions which show a lack of correlation are found. Several aspects of the correlations appear to be particularly important.

Heppner, J. P.↗
NASA NTRS1973

A preliminary study of the neutral wind in the auroral E region

Auroral zone E region neutral winds have been derived from simultaneous measurements of ion drift velocities at different altitudes by the incoherent scatter radar facility at Chatanika, Alaska. The wind derived for quiet and moderately disturbed days shows a consistent pattern during the daytime and appears to be that expected from a day-night pressure asymmetry. In the nighttime, however, the winds are much more variable, apparently responding to the momentum transfer and heating effects of ion drag when sizable electric fields and electron densities are present.

Brekke, A.↗
NASA NTRS1973

The flares of August 1972

Observations of the August, 1972 flares at Big Bear and Tel Aviv, involving monochromatic movies, magnetograms, and spectra, are analyzed. The region (McMath 11976) showed inverted polarity from its inception on July 11; the great activity was due to extremely high shear and gradients in the magnetic field, as well as a constant invasion of one polarity into the opposite; observations in lambda 3835 show remarkable fast flashes in the impulsive flare of 18:38 UT on Aug. 2 with lifetimes of 5 sec, which may be due to dumping of particles in the lower chromosphere. Flare loops show evolutionary increases of their tilts to the neutral line in the flares of Aug. 4 and 7. Spectroscopic observations show red asymmetry and red shift of the H alpha emission in the flash phase of the Aug. 7 flare, as well as substantial velocity shear in the photosphere during the flare, somewhat like earthquake movement along a fault. Finally the total H alpha emission of the Aug. 7 flare could be measured accurately as about 2.5 x 10 to the 30th power erg, considerably less than coarser previous estimates for great flares.

Zirin, H.↗
NASA NTRS1974

Gas-rich meteorites - Possible evidence for origin on a regolith

The asymmetry of irradiation features of grains in the Kapoeta and Fayetteville meteorites suggests irradiation on a regolith before meteorite formation. Chondrules and broken grains require approximately 10,000 years of irradiation time between formation or fracturing and compaction into the meteorite. Shock erasure of tracks from irradiated Kapoeta feldspars requires a severe shock event during or after meteorite formation.

Macdougal, D.↗
NASA NTRS1973

Metallic Fe phases in Apollo 16 fines - Their origin and characteristics as revealed by electron spin resonance studies

The intense electron spin resonance (ESR) signals detected in the Apollo 16 fines from three sites (61141,4, Station 1; 64501,22, South Ray Crater; 67601,20, North Ray Crater) are found to be essentially similar in g-value, in lineshape asymmetry and in temperature dependence to those previously observed for the Apollo 11-15 fines. On the basis of these similarities, it is concluded that these ESR signals like those detected in the Apollo 11-15 fines are principally ferromagnetic in nature arising from metallic Fe phases having the body-centered cubic structure, and not from hematite, magnetite, or any other ferric oxides. It is shown that a quantitative correlation exists between the ESR linewidth observed for the Apollo 11-16 fines and their average Ni contents in the metallic Fe phases as determined by other means. A common source of meteoritic origin is indicated for the metallic Fe phases of these samples.

Tsay, F.-D.↗
NASA NTRS1974

Spatial and temporal behavior of atomic oxygen determined by Ogo 6 airglow observations

Maps are produced of the atomic oxygen density near 97 km showing a strong variation in latitude, longitude, universal time, and time of year. These densities are deduced from atomic oxygen green nightglow observations carried out from Ogo 6. Meridional wind patterns needed to support the asymmetries observed in local oxygen production and loss rates are deduced.

Donahue, T. M.↗
NASA NTRS1974

Decomposition-aggregation stability analysis of the spinning Skylab

Stability of an 11-th order linear model of the spinning Skylab is determined by the decomposition-aggregation method based upon the comparison principle and vector Liapunov functions. To reduce the inherent conservativeness of the method an optimization problem is formulated and resolved producing the optimum comparison system. The system provides the best estimate of the stability region of the important structural parameter - asymmetry in the boom settings.

Cuk, S. M.↗
NASA NTRS1974

Observations of neutral winds in the auroral E region during the magnetospheric storm of August 3-9, 1972

Auroral zone E-region neutral winds have been derived from simultaneous measurements of ion drift velocities in different altitudes by the incoherent radar facility at Chatanika, Alaska, on a quiet day before and during the great magnetospheric storm of Aug. 3-9, 1972. The neutral wind expected for a day-night pressure asymmetry appears to be strongly opposed by ion drag and local pressure gradients in the auroral oval.

Brekke, A.↗