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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 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Irradiation stratigraphy in the Apollo 16 deep drill section 60002

Particle track density frequency distributions, abundance of track rich grains and minimum track densities are reported for the upper 20 cm of the 60002 section of the Apollo 16 deep drill core. The principal stratigraphic feature is a boundary approximately 7 cm from the top of the section. Experimental evidence does not conclusively determine whether this contact is an ancient regolith surface or is simply a depositional boundary. If it is an ancient surface, it has a model exposure age of 3 to 7 million years and a reworking depth of about 0.5 cm. However, because track density frequency distributions indicate the mixing of soils of different maturities, we favor interpreting this contact as a depositional boundary. There may be a second depositional boundary approximately 19 cm below the top of 60002.

Blanford, G. E.↗
NASA NTRS1979

The reaction Mg/n, alpha/Ne at 14.1 and 14.7 MeV - Cross sections and implications for meteorites

Mass spectroscopic analysis of neutron-irradiated targets of natural magnesium yields cross sections of 59 + or - 14, 160 + or - 8, and 11.0 + or - 3.3 mb for Ne-20, Ne-21 and Ne-22, respectively, at 14.1 MeV and of 94 + or - 8, 152 or - 12, and 13.0 + or - 2.0 mb at 14.7 Mev. Using these cross sections, calculations modeling cosmic ray interactions in stony meteoroids of radii 20 and 26 cm predict that between the surface and the center the Ne-22/Ne-21 ratio falls more than 10% while the Ne-21 production rate rises about 30%. Calculations are compared with published neon measurements for the Keyes and St. Severin meteorites.

Reedy, R. C.↗
NASA NTRS1979

Internal-external flow integration for a thin ejector-flapped wing section

Thin airfoil theories of an ejector flapped wing section are reviewed. The global matching of the external airfoil flow with the ejector internal flow and the overall ejector flapped wing section aerodynamic performance are examined. Mathematical models of the external and internal flows are presented. The delineation of the suction flow coefficient characteristics are discussed. The idealized lift performance of an ejector flapped wing relative to a jet augmented flapped wing are compared.

Woolard, H. W.↗
NASA NTRS1979

Shuttle orbiter radar cross-sectional analysis

Theoretical and model simulation studies on signal to noise levels and shuttle radar cross section are described. Pre-mission system calibrations, system configuration, and postmission system calibration of the tracking radars are described. Conversion of target range, azimuth, and elevation into radar centered east north vertical position coordinates are evaluated. The location of the impinging rf energy with respect to the target vehicles body axis triad is calculated. Cross section correlation between the two radars is presented.

Cooper, D. W.↗
NASA NTRS1980

A comparison of calculated and experimental lift and pressure distributions for several helicopter rotor sections

The use of computational techniques in predicting lift coefficients and pressure distributions of two dimenstional airfoil sections was studied. The computer code FL06/IBL was used to solve the compressible, two dimensional flow about four different airfoil sections. The lift coefficients of the airfoils were calculated at various angles of attack at subsonic Mach numbers and compared with experimental data.

Conlon, J.↗
NASA NTRS1980

An experimental evaluation of a helicopter rotor section designed by numerical optimization

The wind tunnel performance of a 10-percent thick helicopter rotor section design by numerical optimization is presented. The model was tested at Mach number from 0.2 to 0.84 with Reynolds number ranging from 1,900,000 at Mach 0.2 to 4,000,000 at Mach numbers above 0.5. The airfoil section exhibited maximum lift coefficients greater than 1.3 at Mach numbers below 0.45 and a drag divergence Mach number of 0.82 for lift coefficients near 0. A moderate 'drag creep' is observed at low lift coefficients for Mach numbers greater than 0.6.

Hicks, R. M.↗
NASA NTRS1979

Critical mass flux through short Borda type inlets of various cross sections

Mass flux measurements associated with choked flows through four Borda-type inlet geometries: circular, square, triangular, and rectangular (two-dimensional) and two sharp-edged geometries are discussed for a wide range of inlet stagnation conditions. The results obtained indicate that the mass flux is independent of the inlet cross-section geometry, while it is dependent on the inlet stagnation conditions. The results also suggest that parallel surfaces as found in seals, dampers, bearings, and heat exchanger tubes of rectangular cross section with Borda-type inlet configurations are subject to large forces. It is noted that the reduced mass flux is independent of working fluid.

Hendricks, R. C.↗
NASA NTRS1979

Photoabsorption cross sections of CH3F, CHF3, CH3Cl, and CF2Cl2 from 175 to 760 A

The study of fluorinated and chlorinated hydrocarbons is of great interest because of their suspected effect on the ozone layer in the atmosphere. Using synchrotron radiation as a continuum background, the present study measures photoelectrically the photoabsorption cross sections of CH3F, CHF3, CH3Cl, and CF2Cl2 in the 175-760 A (70.8-16.3 eV) region, using a double ionization chamber. The absolute absorption cross sections and a tentative interpretation of the observed discrete structures are presented.

Wu, C. Y. R.↗
NASA NTRS1982

Boron/Aluminum-Titanium Hat-Section Stiffener

B/Ai-Ti hat-section stiffener is formed from laminated boron/ aluminum and titanium foils. Double layers of titanium at end of a section offer additional strength and protection. Advanced composite structural element combines stiffness, light weight and durability.

Maikish, C. R.↗
NASA NTRS1981

A procedure for designing forebodies with constraints on cross-section shape and axial area distribution

A method is described for designing a forebody with cross sections which vary smoothly from an initial prescribed nose shape to a different prescribed base shape in such a way that the cross-section areas conform to a preassigned axial area distribution. It is shown that these conditions can be satisfied with a remaining degree of freedon, which can be used to accomplish a modest amount of geometric or pressure tailoring of the forebody. An example is provided which involves modifying the pressure distribution along a given meridian line of the forebody.

Barger, R. L.↗
NASA NTRS1980

Some important geometrical features of conic-section-generated offset reflector antennas

Geometrical characteristics of conic-section-generated offset reflectors are studied in a unified fashion. Some unique geometrical features of the reflector rim constructed from the intersection of the reflector surface and a cone or cylinder are explored in detail. It is found that the intersection curve (rim) of the rotationally generated conic-section reflector surface and a circular cone with its tip at the focal point is always a planar curve and has a circular projection on the focal plane only for the offset parabolic reflector. Furthermore, in this case, the line going through the center of the circle, parallel to the focal axis, and the central axis of the cone do not intersect the reflector surface at the same point. Numerical results are presented to demonstrate some unique features of offset parabolic reflectors.

Jamnejad-Dailami, V.↗
NASA NTRS1981

Study of sulfur-containing molecules in the EUV region. I - Photoabsorption cross section of SO2

Using synchrotron radiation as a continuum background, the absorption cross sections of SO2 have been measured using a double ionization chamber. The cross sections range from 10 to a maximum value of 56 Mb in the 175-760 A region. A possible window resonance series was observed and tentatively assigned to a Ryberg series converging to the (6a sub 1) to the -1st ion state. From the fluorescence excitation function the vibrational progressions of the SO2(+) ion states have been measured and found in good agreement with those observed from photoelectron spectroscopy. The same correspondence between peaks in the fragment fluorescence excitation function and the photoelectron spectrum suggests that these ion states of SO2 are dissociative in nature.

Wu, C. Y. R.↗
NASA NTRS1981

Cross section for Ly-alpha emission by electron impact on methane

Utilizing Lyman-alpha emission cross sections for H2 as secondary standards, absolute values of Lyman-alpha emission cross sections for CH4 have been obtained for electron impact energies varying from threshold to 100 eV. A crossed electron beam-molecular beam geometry was employed and the Lyman-alpha radiation was detected at 90 deg and 45 deg with respect to the incident electron beam by a solar blind photomultiplier in tandem with an oxygen filter. The results are compared with previous measurements. Appreciable differences among the various experimental data are found.

Orient, O. J.↗
NASA NTRS1981

Experimental SF6/-//SF6 and Cl/-//CFC13 electron-attachment cross sections in the energy range 0-200 meV

Experimental cross sections for the electron-attachment processes for SF6(-)/SF6 and Cl(-)/CFl3 are reported in the energy range 0-200 meV by normalizing each attachment line shape to measurement of a thermal rate coefficient. When the same ion states are detected, good agreement is found between present values, for which a monoenergetic electron source is used, and swarm-unfolded results. The present data constitute a new limit for cross sections reported at high resolution at the lowest electron energy.

Chutjian, A.↗
NASA NTRS1981

Temperature dependent UV absorption cross sections for carbonyl sulfide

The ultraviolet absorption spectrum of carbonyl sulfide is investigated in order to assess the importance of the photolytic sink for OCS in the troposphere. Absorption cross sections were measured at wavelengths between 185 and 300 nm in a double-beam spectrometer at temperatures of 295 and 225 K. The results are found to be in good agreement with previous reports in the short wavelength region, but significantly lower than the value of 2 x 10 to the 22nd sq cm/molecule proposed by Rudolf and Inn (1981) between 280 and 300 nm, which may be attributed to trace contaminants or dimerization. A marked temperature effect is noted at wavelengths greater than 240 nm and below 190 nm. As no evidence of absorption at wavelengths greater than 270 nm was found, estimates of the solar photodissociation rate of tropospheric OCS based on the present cross sections yield a value of about 2 x 10 to the -9th/sec, corresponding to a tropospheric lifetime of about 20 years. It is therefore concluded that solar photolysis represents a negligible sink for OCS.

Molina, L. T.↗
NASA NTRS1982

An analytical procedure for computing smooth transitions between two specified cross sections with applications to blended wing body configuration

An analytical procedure is described for designing smooth transition surfaces for blended wing-body configurations. Starting from two specified cross section shapes, the procedure generates a gradual transition from one cross section shape to the other as an analytic blend of the two shapes. The method utilizes a conformal mapping, with subsequent translation and scaling, to transform the specified and shapes to curves that can be combined more smoothly. A sample calculation is applied to a blended wing-body missile type configuration with a top mounted inlet.

Barger, R. L.↗
NASA NTRS1982

The Apollo 15 regolith - Comparative petrology of drive tube 15010/15011 and drill core section 15003

Two Apollo 15 regolith cores - double drive-tube 15010/15011 and deep drill core section 15003 - were compared. The drive tube was taken from near the edge of Hadley Rille within the mare region and the drill core was taken from the landing site, approximately the same distance as the drive tube from the Apennine Front. Optical modes were done on the two cores, each of which was divided into three stratigraphic units defined by minor differences in grain size and modal abundances. Electron microprobe data were collected on the mineral and glass fragments within each unit. Fused-soil-free bulk chemistries were calculated for each unit by modal recombination, using our modal data and average compositional and density data for soil components. It is found that the drive tube and drill core section are fairly homogeneous units both chemically and modally. Both soils are submature to immature. There are, however, significant differences between the cores. The drill core shows significant enrichments of highland lithic-fragments and highland-derived minerals and glasses relative to the drive tube. These differences are attributed to the fresh nature of the drive tube soil whose major source material is mare basalt ejecta from the shallow bedrock.

Walker, R. J.↗
NASA NTRS1982

Radiation and chemistry in the stratosphere - Sensitivity to O2 absorption cross sections in the Herzberg continuum

It is suggested that the discrepancies between observed and modeled vertical profiles of such halocarbons as CFCl3, as well as the problem of simultaneously fitting N2O, CH4, CF2Cl2 and CFCl3 profiles with a single eddy diffusion model, are due to an overestimation of the molecular oxygen absorption cross sections in the 200-220 nm spectral region. The replacement of current O2 cross sections in this range with values that are in better agreement with results for the compounds cited leads to N2O, CF2Cl2 and CFCl3 concentration reductions of factors 0.70, 0.62 and 0.19, respectively. Profiles of CH4, H2 and CO remain unchanged, and the predicted concentration of HNO3 above 30 km is reduced by about 50% for yet another improved fit with observations. It is noted that the correction proposed produces a 30% ozone increase near the 20-25 km peak.

Froidevaux, L.↗

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