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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Subcritical transition to turbulence in plane channel flows

A linear three dimensional mechanism for the transition of plane Poiseuille flows to turbulence is presented which provides good agreement with experimental observations. The mechanism is based on the evolution of states within a band of quasi-equilibria which slowly approach the stable upper branch solutions for the evolution of flow energy but which are strongly unstable to infinitesimal three-dimensional disturbances. Numerical simulation has shown that if two-dimensional flow persists long enough for the three-dimensional perturbations to attain finite amplitude, the resulting three dimensional flow quickly develops a turbulent character with nonperiodic behavior, and thus transition can be predicted from knowledge of the initial two- and three-dimensional energies and time scales. The mechanism predicts transition to turbulence at Reynolds numbers greater than 1000, as observed in experiments, and implies higher threshold three-dimensional energies in plane Couette flow.

Orszag, S. A.↗
NASA NTRS1980

Studying internal and external magnetic fields in Japan using MAGSAT data

Examination of the total intensity data of CHRONIT on a few paths over Japan and its neighboring sea shows MAGSAT is extremely useful for studying the local magnetic anomaly. In high latitudes, the signatures of field aligned currents are clearly recognized. These include (1) the persistent basic pattern of current flow; (2) the more intense currents in the summer hemisphere than in the winter hemisphere; (3) more fluctuations in current intensities in summer dawn hours; and (4) apparent dawn-dusk asymmetry in the field-aligned current intensity between the north and south polar regions.

Fukushima, N.↗
NASA NTRS1980

The combined effects of ionizing radiation and weightlessness on calcium and phosphorus content in the mineral fraction of the calcified tissues in the rat skeleton

Phosphorus and calcium content in the ash from skeletal bones (ribs, scapula, vertebra, and crus) of 30 rats exposed to ionizing radiation (800 rads) on the flight of the Kosmos 690 biosatellite was studied. A 10 percent decrease in ash content coefficient and 29 percent decrease in phosphorus content was found immediately after the flight, and a 9 percent decrease in phosphorus content persisted after 26 days of readaptation to terrestrial conditions.

Prokhonchukov, A. A.↗
NASA NTRS1981

Oceanographic influences on the sea ice cover in the Sea of Okhotsk

Sea ice conditions in the Sea of Okhotsk, as determined by satellite images from the electrically scanning microwave radiometer on board Nimbus 5, were analyzed in conjunction with the known oceanography. In particular, the sea ice coverage was compared with the bottom bathymetry and the surface currents, water temperatures, and salinity. It is found that ice forms first in cold, shallow, low salinity waters. Once formed, the ice seems to drift in a direction approximating the Okhotsk-Kuril current system. Two basic patterns of ice edge positioning which persist for significant periods were identified as a rectangular structure and a wedge structure. Each of these is strongly correlated with the bathymetry of the region and with the known current system, suggesting that convective depth and ocean currents play an important role in determining ice patterns.

Gratz, A. J.↗
NASA NTRS1981

Elemental composition of solar energetic particles

The Low Energy Telescopes on the Voyager spacecraft are used to measure the elemental composition (2 or = Z or = 28) and energy spectra (5 to 15 MeV/nucleon) of solar energetic particles (SEPs) in seven large flare events. Four flare events are selected which have SEP abundance ratios approximately independent of energy/nucleon. The abundances for these events are compared from flare to flare and are compared to solar abundances from other sources: spectroscopy of the photosphere and corona, and solar wind measurements. The four flare average SEP composition is significantly different from the solar composition determined by photospheric spectroscopy. The average SEP composition is in agreement with solar wind abundance results and with a number of recent coronal abundance measurements. The evidence for a common depletion of oxygen in SEPs, the corona and the solar wind relative to the photosphere suggest that the SEPs originate in the corona and that both the SEPs and solar wind sample a coronal composition which is significantly and persistently different from that of the photosphere.

Cook, W. R., III↗
NASA NTRS1978

Space fabrication demonstration system

The lower right aluminum beam cap roll forming mill was delivered and installed in the beam builder. The beam was brought to full operational status and beams of one to six bay lengths were produced to demonstrate full system capability. Although the cap flange waviness problem persists, work is progressing within cost and schedule.

Source record↗
NASA NTRS1981

Insulators for Pb(1-x)Sn(x)Te

Thin films of LaF3 were e-gun and thermally deposited on several substrates. The e-gun deposited films are fluorine deficient, have high ionic conductivities that persist to 77 K, and high effective dielectric constants. The thermally deposited material tends to be closer to stoichiometric, and have higher effective breakdown field strengths. Thermally deposited LaF3 films with resistivities in excess of 10 to the 12th power ohms - cm were deposited on metal coated glass substrates. The LaF3 films were shown to adhere well to PbSnTe, surviving repeated cycles between room temperature and 77 K. The LaF3 films on GaAs were also studied.

Tsuo, Y. H.↗
NASA NTRS1980

Assessment of zero gravity effects on space worker health and safety

One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the references Solar Power Satellites (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers either immediate or delayed due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiency in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five year career period. The proposed 90 day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five year career.

Source record↗
NASA NTRS1981

Anomalous ionization seen in the spectra of B supergiants

An IUE survey of B supergiants has been conducted to study the persistence with spectral type of the ultraviolet resonance lines of N V, C IV and Si IV. N V is seen as late as B2.5Ia, C IV until B6Ia and Si IV throughout the range from B1.5 to B9. This is in fairly good agreement with the Auger ionization model of Cassinelli and Olson (1979). The terminal velocities are derived for the 20 stars in the sample and it is found that the ratio v(T)/v(esc) decreases monotonically with spectral type from the value of 3.0 that it has in the O spectral range to the value 1.0 at B9Ia.

Cassinelli, J. P.↗
NASA NTRS1981

UV chromospheric and circumstellar diagnostic features among F supergiant stars

A survey of F supergiant stars to evaluate the extension of chromospheric and circumstellar characteristics commonly observed in the slightly cooler G, K, and M supergiant is discussed. An ultraviolet survey was elected since UV features of Mg II and Fe II might persist in revealing outer atmosphere phenomena even among F supergiants. The encompassed spectral types F0 to G0, and luminosity classes Ib, Ia, and Ia-0. In addition, the usefulness of the emission line width-to-luminosity correlation for the G-M stars in both the Ca II and Mg II lines is examined.

Stencel, R. E.↗
NASA NTRS1980

Possible influence of solar rotation on tropospheric circulation

A large-scale structure observed in the photospheric magnetic field is carried out into the heliosphere by the solar wind. At Earth the resulting interplanetary magnetic field has polarity away from the Sun for several consecutive days followed by an abrupt reversal and several days with field polarity toward the Sun. Low-pressure troughs near the Gulf of Alaska appear to have significantly larger area when the interplanetary field is away from the Sun than when it is toward the Sun. This relation persisted during most of the winters of 1951 to 1973. Surface pressures around the Gulf of Alaska during some winters were in anti-phase for interplanetary field toward and away from the Sun. During the two days after a polarity reversal, the accuracy of the best weather forecasts for the continental United States appears to be significantly lower than at other times. Polarity reversals that are accompanied by energetic interplanetary conditions appear to be associated with a larger decrease in the area of the low pressure troughs.

Wilcox, J. M.↗
NASA NTRS1980

Radiation damping of long, finite-amplitude internal waves

Numerical solutions of a damped, nonlinear wave equation are presented. The equation describes the propagation of waves in a narrow thermocline or inversion which lose energy by exciting internal waves in the weakly stratified ambient environment. The results provide estimates for the persistence of finite-amplitude internal waves propagating in a thermoclinic waveguide.

Pereira, N. R.↗
NASA NTRS1980

Time-resolved imaging and spectral studies of an X-ray burst from the globular cluster Terzan

The first image of an X-ray burst was recorded with the HRI detector at the Einstein Observatory while observing the globular cluster Terzan 2. The burst was coincident with a persistent X-ray source located near the center of the cluster (thus confirming an earlier suggested identification) and reached a peak luminosity exceeding 5 x 10 to the 38th (d/10 kpc) squared. After a rapid rise to peak luminosity, a double-peaked spectral variation was observed over the next approximately 20 s with anticorrelated changes in the apparent emission region radius and temperature derived from blackbody (and modified blackbody) spectral fits. A shell or disk geometry, which undergoes adiabatic expansion and contraction, may be implied for the burst emission region. Alternatively, Comptonization is required. It is also shown that the peak burst luminosity must exceed the Eddington limit.

Grindlay, J. E.↗
NASA NTRS1980

Long nonlinear waves in stratified shear flows

The propagation of finite-amplitude internal waves in a shear flow is considered for wavelengths that are long compared to the shear-layer thickness. Both singular and regular modes are investigated, and the equation governing the amplitude evolution is derived. The theory is generalized to allow for a radiation condition when the region outside the stratified shear layer is unbounded and weakly stratified. In this case, the evolution equation contains a damping term describing energy loss by radiation which can be used to estimate the persistence of solitary waves or nonlinear wave packets in realistic environments. A continuous three-layer model is studied in detail and closed-form expressions are obtained for the phase speed and the coefficients of the nonlinear and dispersive terms in the amplitude equation as a function of Richardson number.

Maslowe, S. A.↗
NASA NTRS1981

Bi-directional streaming of solar wind electrons greater than 80 eV - ISEE evidence for a closed-field structure within the driver gas of an interplanetary shock

In near time coincidence with the arrival of helium enriched plasma driving the shock wave disturbance of November 12-13, 1978, strong bi-directional streaming of solar wind electrons greater than about 80 eV was observed with Los Alamos instrumentation on ISEE 3. The streaming persisted for many hours simultaneously parallel and anti-parallel to the interplanetary magnetic field which was directed roughly perpendicular to the sun-satellite line. This example of bidirectional streaming cannot be explained by field line connection to the earth's bow shock or the outward propagating interplanetary shock which passed ISEE 3 approximately 16 hours earlier. The event is explained if the local interplanetary field was a part of a magnetic bottle rooted at the sun or a disconnected loop propagating outward.

Bame, S. J.↗
NASA NTRS1981

Time and duration of lunar highlands crust formation

Due to remaining uncertainties in model parameters and assumptions in the calculation of model ages, it is not yet possible to resolve the precise dating and duration of lunar crust-mantle differentiation phenomena. Norites 78236 and 73255,27,45 were examined utilizing the Sm-Nd radiometric system. The systematics of 78236 show post-crystallization disturbance but indicate a crystallization date 4.34 AE ago. An isochron is defined by the 73255,27,45 data, with a crystallization date of 4.23 AE. The initial Nd isotopic composition of both norites is within uncertainty limits for a 'chondritic' reference reservoir at the time of their respective crystallizations. The implications for lunar crustal formation persisting over a time span of nearly 350 million years are discussed.

Carlson, R. W.↗
NASA NTRS1980

Modification in drag of turbulent boundary layers resulting from manipulation of large-scale structures

The effects of placing a parallel-plate turbulence manipulator in a boundary layer are investigated by means of flow visualization and hot-wire measurements. The manipulator was found to be effective in inhibiting the intermittent large scale structure of the boundary layer, and the effect persists for at least 70 boundary-layer thicknesses downstream of the manipulator. With the removal of the large scale, there was an observed reduction in the streamwise turbulence intensity levels near the wall. The downstream distribution of the skin friction coefficient, determined from the stream wise change in fluid momentum, was also altered by the introduction of the manipulator. The data from both the visualization and hot wire studies are provided.

Corke, T. C.↗
NASA NTRS1980

Ultraviolet contrasts and the absorbers near the Venus cloud tops

The UV measurements of the Venus atmosphere absorbers constrain the location, altitude, and identity near the Venus cloud tops. The spin-scan images observed by the Pioneer Venus orbiter spectrometer (UVS) and the cloud photopolarimeter measure contrasts in the 1990-3650 A range and at phase angles between 33 and 130 deg; the planet is darkest at the location where the UVS line of sight penetrates in the direction perpendicular to the cloud tops. SO2 absorption accounts for the contrast from 2000 to 3200 A; the persistence of contrast at longer wavelengths requires another absorber at about 75-mbar altitude. The correlation between the planetary differences and polarization does not need large-scale clearing or major vertical motions of the cloud tops as the main cause of the observed variations.

Esposito, L. W.↗