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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Ion temperatures in HIP-1 and SUMMA from charge-exchange neutral optical emission spectra

Ion temperatures were obtained from observations of the H sub alpha, D sub alpha, and He 587.6 nm lines emitted from hydrogen, deuterium, and helium plasmas in the SUMMA and HIP-1 mirror devices at Lewis Research Center. Steady state discharges were formed by applying a radially inward dc electric field between cylindrical or annular anodes and hollow cathodes located at the peaks of the mirrors. The ion temperatures were found from the Doppler broadening of the charge-exchange components of spectral lines. A statistical method was developed for obtaining scaling relations of ion temperature as a function of current, voltage, and magnetic flux density. Derivations are given that take into account triangular monochromator slit functions, loss cones, and superimposed charge-exchange processes. In addition, the Doppler broadening was found to be sensitive to the influence of drift on charge-exchange cross section. The effects of finite ion-cyclotron radius, cascading, and delayed emission are reviewed.

Patch, R. W.↗
NASA NTRS1975

The photoionization spectrum of neutral aluminium, Al I

The absorption spectrum of Al I has been studied for the wavelength range 1160 to 2000 A by the flash pyrolysis technique. Wavelengths and derived energy levels are reported for 70 new lines converging on the 3s3p(3)P(0) limits of Al II. The autoionization parameters of the 3p(2)P(0)-3p(2)(2)S doublet have been measured. Good agreement is obtained with the experiment of Kohl and Parkinson and the recent calculation of Le Dourneuf et al. The relative photoionization cross section has been measured in the wavelength region 1200 A to 2000 A.

Roig, R. A.↗
NASA NTRS1976

Neutral calcium, strontium and barium - Determination of f values of the principal series by the hook method

The hook method is used to measure the absolute gf values of the following lines: the first 13 members of the principal series, the ground-level transition at 2275.46 A, and the intercombination line at 6572.78 A in Ca I; the first 22 members of the principal series, the ground-level transitions at 2428.1 and 2680.08 A, and the intercombination line at 6892.6 A in Sr I; and the members from principal quantum numbers 12 to 21, inclusive, as well as the ground-level transitions at 2432.5, 2444.6, and 2454.06 A in Ba I. The results are compared with those of previous measurements, and the quantum-defect method is applied to plot the oscillator strengths of the discrete transitions in the principal series of Mg I, Ca I, and Sr I in order to obtain estimates of the photoionization cross sections at the first ionization limit. The resulting cross sections are found to be about twice as large as previous values based on vapor-pressure data.

Parkinson, W. H.↗
NASA NTRS1976

Traveling neutral disturbances

The coupling of acoustic-gravity waves in the main atmosphere to acoustic waves characteristic of individual minor species in the atmosphere is postulated. Such coupling would exist as a result of resonances in the response of the minor species, and its likelihood depends on the mass of the atmospheric particle relative to the major species mass, the diffusion of the minor species, and the direction of propagation of the main disturbance. These minor-species disturbances may explain some AE-C measurements in the thermosphere and could possibly play a role in the distribution of minor species and their chemistry in the mesosphere.

Gross, S. H.↗
NASA NTRS1976

Analysis of neutrally stable atmospheric flow over a two-dimensional forward facing step

A mathematical model describing ground-wind induced flow fields around surface obstructions such as buildings, bridges or other man-made structures is presented. The Navier-Stokes equations with a two-equation turbulence model are used to analyze the flow over a two-dimensional forward facing step. A study of the assumed logarithmic approach velocity profile shows that an increase of surface roughness produces a rise to higher turbulence levels in the shear layer originating from the step corner. This rise leads to higher Reynolds stress and to faster reattachment of the separated flow.

Bitte, J.↗
NASA NTRS1976

Neutral hydrogen in the direction of the Small Magellatic Cloud and the limits of an extragalactic soft X-ray flux

Previously reported X-ray data from the vicinity of the Small Magellanic Cloud (SMC) have been reanalyzed using H I data from a more detailed and sensitive 21-cm survey of this region. The results support the previous conclusion: assuming that the interstellar material absorbs according to the cross sections of Brown and Gould (1970), at least 75 per cent of the observed 0.25-keV X-ray flux is of local origin. The corollary problem of placing a cosmologically useful upper limit on the extragalactic flux will be difficult to solve until the behavior of the local component is better understood; but if the local flux is isotropic, a 3-sigma upper limit of 240 photons per (sq cm s sr keV) at 0.25 keV may be placed on a flux originating beyond the SMC. Tables of H I column density are given for an area 30 deg by 30 deg about the SMC. The high-velocity component, presumably associated with the Magellanic Cloud system, and the galactic disk component are tabulated separately.

Mccammon, D.↗
NASA NTRS1976

The absorption spectrum of neutral boron, B I

The absorption spectrum of B I has been studied in the 900-2000 A wavelength range by the flash pyrolysis technique. Transitions were observed from both the 2s(2)2p 2P ground state and the 2s2p2 4P metastable state. Five new quartet terms have been identified, with improved values obtained for two previously identified terms. A method of focusing has been developed, allowing the Ballofet-Romand-Vodar (1961) source to be used as a source of single-shot continuum in the lower wavelengths (300-1200 A) of the normal incidence region.

Roig, R. A.↗
NASA NTRS1977

Research study on neutral thermodynamic atmospheric model

The Global Reference Atmospheric Model is used along with the revised perturbation statistics to evaluate and computer graph various atmospheric statistics along a space shuttle reference mission and abort trajectory. The trajectory plots are height vs. ground range, with height from ground level to 155 km and ground range along the reentry trajectory. Cross sectional plots, height vs. latitude or longitude, are also generated for 80 deg longitude, with heights from 30 km to 90 km and latitude from -90 deg to +90 deg, and for 45 deg latitude, with heights from 30 km to 90 km and longitudes from 180 deg E to 180 deg W. The variables plotted are monthly average pressure, density, temperature, wind components, and wind speed and standard deviations and 99th inter-percentile range for each of these variables.

Hargraves, W. R.↗
NASA NTRS1977

A semiempirical atmosphere for alpha Tauri from neutral iron lines

A semiempirical model photosphere is constructed for the K5 III star Alpha Tau. The technique employed is based on measurements of the central fluxes in a series of lines in multiplets. Observations of four multiplets having a range in excitation potential yield the excitation temperature as a function of the optical depth in a reference line. If the temperature structure of an assumed starting model is changed to force agreement between the observed and predicted line source functions under the assumption that excitation and electron kinetic temperatures are equal, the final semiempirical model is cooler by 150 K in the outer layers and warmer by 150 K in deeper layers than the theoretical model with the parameters adopted for Alpha Tau.

Ramsey, L. W.↗
NASA NTRS1977

Motion of near-neutrally buoyant tracers in vortical flows

An analysis of the motion of particles of arbitrary density and size in solid body and potential vortex flows is presented. The study provides a basis for precise, quantitative reduction of tracer-particle visualization of such flows in water tunnels.

Charwat, A. F.↗