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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

The behavior of a convergent plate boundary - Crustal deformation in the South Kanto district, Japan

The northwesternmost part of the Sagami trough, a part of the Philippine Sea-Eurasian plate boundary, was ruptured during the great South Kanto earthquake in 1923. Very extensive and frequent geodetic measurements of crustal deformation have been made in the South Kanto district since the 1890's, and these constitute the most complete data set on crustal movements in the world. These data were reanalyzed and interpreted and according to our interpretation indicate the following sequence of events. The coseismic movements were due to oblique thrust and right lateral slip of about 8 m on a fault outcropping at the base of the Sagami trough. This was followed by postseismic deformation resulting from reversed afterslip of 20-60 cm that occurred at an exponentially decaying rate in time. The interseismic deformation is produced by steady subduction at a rate of about 1.8 cm/yr. During subduction the top 10-15 km of the plate boundary is apparently locked, while deeper parts slip aseismically at an irregular rate. No significant precursory deformation was observed. The recurrence time for 1923 type earthquakes is 200-300 years. The Boso and Miura peninsulas are broken into a series of fault-bound blocks that move semi-independently of the surrounding region. The subduction zone itself, where it is exposed on land, is shown to be a wide zone encompassing several faults that are active at different times.

Scholz, C. H.↗
NASA NTRS1978

The cosmic-ray isotopes

Aspects and implications of isotopic abundance measurements are discussed, taking into account the elemental abundance distribution of the cosmic radiation and the solar system abundances normalized to C. An interesting outcome of observations on cosmic ray isotopes is the determination of the span of time that elapses between nucleosynthesis and acceleration of the particles. This has an immediate bearing on the question whether explosive nucleosynthesis and particle acceleration occur simultaneously, or whether these two phases in the production of cosmic rays are separate. The absence of Co-57, Ti-44, and Ni-59 with K-capture decay rates of approximately 1 yr, 50 yr, and 100,000 yr respectively in the cosmic ray flux would indicate that the time between nucleosynthesis and acceleration would be greater than 1, 50, or 100,000 yr, respectively.

Meyer, P.↗
NASA NTRS1979

Characteristics of the wake of a lightly loaded compressor or fan rotor

An experimental investigation was carried out to evaluate the properties of the rotor fan or compressor wake in order to understand the structure of the wake. This included a study of profile shape, decay characteristics, effects of rotation, and effects of varying blade loading on the wake. Rotating tri-axial hot-wire probe measurements were reported which represent the first systematic data in the near wake region of the rotor wake using this technique. It is found that the radial, tangential, and axial components of mean velocities and turbulence intensities decay very rapidly near the rotor blade trailing edge, and that increased blade loading reduces the decay rates of axial and tangential mean velocity defects and radial velocities in the wake. In particular, the presence of an almost constant wake width region for increasing axial distance shows the effects of three-dimensionality on the rotor wake flow. Other conclusions are also given.

Reynolds, B. D.↗
NASA NTRS1979

Mean velocity and decay characteristics of the guidevane and stator blade wake of an axial flow compressor

Pure tone noise, blade row vibrations, and aerodynamic losses are phenomena which are influenced by stator and IGV (inlet guide vane) blade wake production, decay, and interaction in an axial-flow compressor. The objective of this investigation is to develop a better understanding of the nature of stator and IGV blade wakes that are influenced by the presence of centrifugal forces due to flow curvature. A single sensor hot wire probe was employed to determine the three mean velocity components of stator and IGV wakes of a single stage compressor. These wake profiles indicated a varying decay rate of the tangential and axial wake velocity components and a wake profile similarity. An analysis, which predicts this trend, has been developed. The radial velocities are found to be appreciable in both IGV and the stator wakes.

Lakshminarayana, B.↗
NASA NTRS1979

Characteristics of lightly loaded fan rotor blade wakes

Low subsonic and incompressible wake flow downstream of lightly loaded rotor was studied. Measurements of mean velocity, turbulence intensity, Reynolds stress, and static variations across the rotor wake at various axial and radial locations were investigated. Wakes were measured at various rotor blade incidences to discern the effect of blade loading on the rotor wake. Mean velocity and turbulence measurements were carried out with a triaxial hot wire probe both rotating with the rotor and stationary behind the rotor. Results indicate that increased loading slows the decay rates of axial and tangential mean velocity defects and radial velocities in the wake. The presence of large radial velocities in the rotor wake indicate the extent of the interactions between one radius and another. Appreciable static pressure variations across the rotor wake were found in the near wake region. Similarity in the profile shape was found for the axial and tangential components of the mean velocity and in the outer layer for axial, tangential, and radial turbulence intensities.

Reynolds, B.↗
NASA NTRS1980

Combustion stability with baffles, absorbers and velocity sensitive combustion

Analytical and computational techniques were developed to predict the stability behavior of liquid propellant rocket combustors using damping devices such as acoustic liners, slot absorbers, and injector face baffles. Models were developed to determine the frequency and decay rate of combustor oscillations, the spatial and temporal pressure waveforms, and the stability limits in terms of combustion response model parameters.

Mitchell, C. E.↗
NASA NTRS1979

Assessment of shuttle payloads gaseous environment contamination and its control

A prediction is given of the in-orbit gaseous environment and the contamination it could produce on cryogenic and room temperature surfaces of payloads in the shuttle bay. The time varying environment was obtained by the superposition of the calculated shuttle environment for a discrete time and payload induced environments measured in large space chambers. Representative contaminant surface accretions were calculated for flights 1 week and 1 month long for payloads having the largest source of outgassing and an orbit of 200 km. A number of calculations were based on the magnitude of the sources, the molecular natures, the decay rate with time, the sticking coefficients, the view factors, and the temperatures of the surfaces being contaminated. Significant results are reported.

Scialdone, J. J.↗
NASA NTRS1980

Atomic data and level populations of highly ionized Ti for tokamak plasmas

The paper presents calculations of electron impact collision strengths and spontaneous radiative decay rates for titanium ions of the LiI through FI isoelectronic sequences for transitions between levels of the 2S(2)2p(k), 2s2p(k+1), and 2p(k+2) configurations. From these atomic data, excitation-rate coefficients are calculated along with level populations for these three configurations. The calculations of level populations include the effects of proton excitation, and are carried out at electron temperatures and densities typical of tokamak plasmas. Wavelengths of forbidden and intersystem lines are given, and a synthetic spectrum is presented for a typical temperature and density.

Bhatia, A. K.↗
NASA NTRS1980

Mechanisms of wave transformation in finite-depth water

Mechanisms of wave transformation in finite-depth water are investigated. The linear mechanisms examined are percolation, bottom motion, shoaling, and refraction. The nonlinear mechanisms examined are wave-wave interaction and bottom friction. New exact computations of the nonlinear transfer for finite-depth waves are presented for some directional wave spectra. These mechanisms are found to explain satisfactorily wave decay observations obtained at several sites with different bottom sediment properties. The decay rates at these sites are found to be dominated by different mechanisms which are determined by the bottom conditions. As an example, detailed calculations are presented for data obtained at the Jonswap site.

Shemdin, O. H.↗
NASA NTRS1980

An X-ray survey of nine historical novae

The Einstein Observatory imaging proportional counter was used to search for X-ray emission from nine nearby historical novae. Six of the novae were detected with estimated X-ray intensities between .1 to 4 keV of 10 to the -13th power to 10 to the -11th power ergs/sq cm-s, comparable to the intensities of previously detected cataclysmic variables. The X-ray intensity of one of the novae, V603 Aql, varies over times of several hundred seconds. The data suggest a correlation between the decay rate of the historical outburst and the current X-ray luminosity. Alternatively, the X-ray luminosity may be related to the inclination of the binary system.

Becker, R. H.↗
NASA NTRS1981

An X-ray survey of nine historical novae

The Einstein Observatory Imaging Proportional Counter has been used to search for X-ray emission from nine nearby historical novae. Six of the novae have been detected with estimated X-ray intensities between 0.1 and 4 keV of 10 to the -13th to 10 to the -11th erg/sq cm-sec, comparable to the intensities of previously detected cataclysmic variables. The X-ray intensity of one of the novae, V603 Aql, varies over times of several hundred seconds. The data suggest a correlation between the decay rate of the historical outburst and the current X-ray luminosity. Alternatively, the X-ray luminosity may be related to the inclination of the binary system.

Becker, R. H.↗
NASA NTRS1981

Effects of rotation and blade incidence on the properties of turbomachinery rotor wake

An experimental investigation of the effects of the speed of rotation on a turbomachinery rotor blade wake was conducted using a fan rotor in incompressible flow. Measurements were made at two different rotational speeds (1753 and 1010 rpm) but keeping the same blade loading. This was achieved by maintaining the same incidence angle to the rotor blades in both sets of measurements. The blade incidence angle was also varied to discern the effect of blade loading. A tri-axial hot wire probe mounted in a stationary frame of reference was used for the measurements made at several radial and axial stations in the near- and far-wake regions. The three dimensional mean velocity and turbulence profiles, the wake defect, wake decay rate, turbulence intensities and turbulence stresses are appreciably altered when the speed of rotation and the blade loading are changed. The wake defect is substantially reduced and the radial velocity increased when the rotational speed is increased.

Lakshminarayana, B.↗
NASA NTRS1981

Solar observations and atomic data for the 3s2 1s0-3s3p 3P1 transition in S v

High resolution solar observations of the S v intersystem line at 1199.18 A are available from Skylab. This line is potentially useful as a density diagnostic for high density plasmas expected in solar flares. S v lines are also prominent in solar spectra at wavelengths below 1000 A. Collision strengths and radiative decay rates are calculated for levels of the configurations 3 s2, 3s3p, 3p2, and 3s3d. Level populations for the five lowest energy levels have been calculated as a function of electron density. These calculations are carried out assuming the temperature at which S v is most abundant in solar plasmas. The calculated population of the 3s3p 3P1 level reaches a pseudo-Boltzmann equilibrium at a density which is about five times higher than is derived from solar spectra and previous density determinations. It is believed that the discrepancy is due to a significant contribution from resonances to the 3s2-3s3p 3P excitation rate coefficient. It is suggested that the contribution of the resonances to the S v excitation rate coefficient can be estimated from a comparison of the experimental results and the theoretical calculations.

Feldman, U.↗
NASA NTRS1982

The UOSAT magnetometer experiment

The magnetometer aboard the University of Surrey satellite (UOSAT) and its associated electronics are described. The basic fluxgate magnetometer employed has a dynamic range of plus or minus 8000 nT with outputs digitized by a 12-bit successive approximation A-D converter having a resolution of plus or minus 2 nT. Noise in the 3-13 Hz bandwidth is less than 1 nT. A bias field generator extends the dynamic range to plus or minus 64,000 nT with quantization steps of 8000 nT. The magnetometer experiment is expected to provide information on the secular variation of the geomagnetic field, and the decay rate of the dipole term. Special emphasis will be placed on the acquisition of real time and memory data over the poles which can be correlated with that from Magsat.

Acuna, M. H.↗
NASA NTRS1982

Precursor gases of aerosols in the Mount St. Helens eruption plumes at stratospheric altitudes

Nineteen stratospheric samples from the eruption plumes of Mount St. Helens were collected in five flight experiments. The plume samples were collected at various altitudes from 13.1 to 20.7 km by using the Ames cryogenic sampling system on board the NASA U-2 aircraft. The enriched, cryogenically collected samples were analyzed by chromatography. The concentrations of aerosols precursor gases (OCS, SO2, and CS2), CH3Cl, N2O, CF2Cl2, and CFCl3 were measured by gas chromatography. Large enhancement of the mixing ratio of SO2 and moderate enhancement of CS2 and OCS were found in the plume samples compared with similar measurement under pre-volcanic conditions. A fast decay rate of the SO2 mixing ratio in the plume was observed. Measurement of Cl(-), SO2(2-), and NO3(-) by ion chromatography was also carried out on water solutions prepared from the plume samples. The results obtained with this technique imply large mixing ratios of HCl, (NO + NO2 + HNO3), and SO2, in which these constituents are the respective sources of the anions. Measurement of the Rn222 concentration in the plume was made. Other stratospheric constituents in the plume samples, such as H2O, CO2, CH4, and CO, were also observed.

Inn, E. C. Y.↗
NASA NTRS1983

Design for prevention of acoustic fatigue

It is pointed out that new noise prediction methods and acoustic life estimation methods have matured to the point where they can be combined into a unified engineering procedure. "Life derivatives" can be extracted from parametric charts to furnish design data for preventing acoustic fatigue. The acoustic fatigue life is shown to be sensitive to the damping ratio through the use of life derivatives. The localized nature of propeller noise can be quantified with an "isodecibel" contour diagram.Even though the peak sound pressure level may be high, the directional derivatives show the noise decay rates with distance. Acoustic fatigue design is discussed from the overall design methodology and is shown to be similar to other structural design problems. While nonlinearities present a formidable design engineering problem, they are manageable by proven semi-empirical techniques. For new design problems, it is imperative to determine whether the data base completely spans the design variables.

Smith, H. W.↗
NASA NTRS1983

Short wavelength laser calculations for electron pumping in neon-like krypton (Kr XXVII)

Calculations of electron impact collision strengths and spontaneous radiative decay rates are made for neon-like krypton (Kr XXVII) for the 2s2 2p6, 2s2 2p5 3s, 2s2 2p5 3p, and 2s2 2p5 3d configurations. From these atomic data, the level populations as a function of the electron density are calculated at two temperatures, 1 x 10 to the 7th K and 3 x 10 to the 7th K. An analysis of level populations reveals that a volume of krypton in which a significant number of the ions are in the Kr XXVII degree of ionization can produce a significant gain in transition between the 2s2 2p5 3s and 2s2 2p5 3p configurations. At an electron density of 1 x 10 to the 19th/cu cm the plasma length has to be of the order of 1 m; at a density of 1 x 10 to the 21st/cu cm the length is reduced to approximately 0.5 cm; and at an electron density of 1 x 10 to the 22nd/cu cm the length of the plasma is further reduced to approximately 1 mm.

Feldman, U.↗