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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Large-scale reflection and absorption of solar radiation by clouds as influencing earth radiation budgets - New aircraft measurements.

Discussion of the first results of extensive recent aircraft measurements, in the short wavelengths, of the reflection and absorption properties of clouds and their impact on radiation budget studies. From the data obtained, the albedo of typical cloud types was determined integrally and spectrally. Some preliminary results are also offered for short-wave absorption and the apparent transmission of clouds. The effect of the atmospheric pathlength between sensor and target, exhibited through molecular scattering and aerosol scattering and absorption, is included in the data analysis. Results are also presented on vertical (short-wave) radiative flux profiles, within specific wavelength intervals, from near sea level to altitudes of about 40,000 ft over relatively short time intervals.

Drummond, A. J.↗
NASA NTRS1973

The calculation of proportional counter energy-deposition spectra from experimental data.

The experimental approach considered requires the measurement of energy-absorption distributions for a set of pathlengths which define a biological volume. A suitable folding procedure is necessary to produce composite energy-absorption distributions. The investigation is concerned with the quality of the prediction of energy-deposition distributions, taking into account distributions measured with a proportional counter.

Steigerwalt, J. E.↗
NASA NTRS1972

Temperature measurements behind reflected shock waves in air

A radiometric method for the measurement of gas temperature in self-absorbing gases has been applied in the study of shock tube generated flows. This method involves making two absolute intensity measurements at identical wavelengths, but for two different pathlengths in the same gas sample. Experimental results are presented for reflected shock waves in air at conditions corresponding to incident shock velocities from 7 to 10 km/s and an initial driven tube pressure of 1 torr. These results indicate that, with this technique, temperature measurements with an accuracy of + or - 5 percent can be carried out. The results also suggest certain facility related problems.

Bader, J. B.↗
NASA NTRS1975

Ultrasonic displacement system

An acoustic instrument system is described as a feasible tool for remote measurement of structural velocities. The system involves measurement of the Doppler shift of ultrasonic sound as it is reflected from an oscillating plate. Measurements were performed in air with an ultrasonic frequency source of 42.5 kilohertz. The surface under investigation was a plexiglass plate oscillating sinusoidally at 10, 13, and 15 Hz. Data are presented to show that, in such a system, the measurement of the Doppler shift is dependent upon the acoustic pathlength between the sensing device and the oscillating surface, with the distance between maximum shifts being half the wavelength of the ultrasonic source.

Faulcon, N. D.↗
NASA NTRS1975

Status of the evidence for a magnetic monopole

The experimental evidence supporting the detection of a moving magnetic monopole, using a balloon-borne array of track detectors, was presented. Although the results cannot be proved to have been produced by a monopole, they do not seem to have been produced by any nucleus. The very high, roughly constant ionization rate inferred from track etch rate measurements in a stack of Lexan detectors implies passage of a minimum-ionizing particle more highly charged than any known nucleus, yet the Cerenkov film detectors indicated a velocity less than about 0.68 times the speed of light and the size of the track in the nuclear emulsion indicated a velocity approximately equal to 0.5 times the speed of light. At this velocity the ionization rate of a highly electrically charged particle would have changed dramatically with pathlength unless its mass to charge ratio were far greater than that of a nucleus.

Price, P. B.↗
NASA NTRS1975

The isotopic composition of galactic cosmic ray Li, Be, and B

New measurements are reported of the isotopes of cosmic-ray Li, Be, and B and of the elements C, N, and O, with cosmic ray telescopes on board the IMP-7 and IMP-8 satellites during 1973-74 in the energy range 35-210 MeV/nucleon. High mass resolution and stability together with a set of data more extensive than in previous experiments lead to a clear isotopic separation. The measured isotopic and chemical abundances provide a stringent test for models of interstellar propagation and solar modulation. We find not only that for a steady state propagation and solar modulation model all light isotopes and medium element abundances are explained by 5 g/sq cm average pathlengths, as was earlier found from element analysis, but that also these results, taken along with our Be-10 measurements, indicate a longer lifetime for cosmic rays than predicted by the usual assumption of an average interstellar density of 1 to 3 atoms/cu cm.

Garcia-Munoz, M.↗
NASA NTRS1977

Antenna bias rigging for performance objective

An optimum bias rigging for a paraboloidal antenna can be used to minimize the expected average mean-square half-pathlength surface deviations. Statistics of deep space planetary missions are employed to develop weighting factors for antenna elevation angles during these missions. A procedure is shown to compute the optimum rigging angle from these weights.

Levy, R.↗
NASA NTRS1980

Calculation of the spectral transmission of the earth's atmosphere in the region of the NO gamma bands

Realistic long path, high resolution transmission spectra of the atmosphere have been calculated in the regions of the (0,0) and (1,0) NO gamma bands for zenith angles between 40 and 70 deg and for pathlengths between 28.5 and 120 km. The transmission spectra have been compared with Harvard solar rocket spectra to provide spectral irradiances at 28.5 km which is a typical balloon float altitude. Such data have immediate application to the remote sensing of atmospheric NO from balloons and satellites.

Freedman, R.↗
NASA NTRS1980

The elemental abundances of hydrogen through nickel in the low energy cosmic rays

The relative abundances of the elements H through Ni in the galactic cosmic rays have been measured in the energy range 70-280 MeV/nucleon with the University of Chicago cosmic ray telescope on board the satellite IMP-8 from January 1973 to September 1978. Cosmic ray source abundances have been derived by extrapolating the measured composition back to the source. A key factor in the propagation calculation is the use of a pathlength distribution and a solar modulation level shown to be consistent with the secondary to primary ratios and their energy dependence below about 1 GeV/n.

Garcia-Munoz, M.↗
NASA NTRS1980

The energy dependence of the ratios of secondary to primary elements in the cosmic radiation

The secondary to primary ratios B/C, N/O and (Sc-Mn)/Fe in the galactic cosmic rays have been measured in the overall energy interval 30-180 MeV/n with the University of Chicago cosmic ray telescope on board the satellite IMP-8 during the period 1974-1978. These results, together with the values of the same ratios measured at higher energies, have been compared to the results of cosmic ray propagation calculations using different pathlength distributions (PLD) and different levels of solar modulation, in order to select a single set of parameters consistent with all the measured ratios.

Garcia-Munoz, M.↗
NASA NTRS1982

The source abundances of galactic cosmic rays

The galactic cosmic ray source abundances have been determined from two complete datasets, one at low and the other at high energy. For both exponential and truncated exponential pathlength distributions (PLD), the two sets of source abundances show significant differences for the primary elements, i.e., the Fe/O ratio. An energy dependent PLD reduces but does not eliminate the discrepancy, and this may indicate an energy dependence in the source composition. New source abundances for Na, P, Cl, Ca, and Mn are derived.

Dwyer, R. D.↗
NASA NTRS1982

Source abundances and propagation of relativistic cosmic rays up to Z equals 30 - HEAO 3 results

Results from the cosmic ray isotope experiment on board the HEAO 3 satellite are reviewed, noting their impact on astrophysics. The gamma ray telescope comprised 5 Cerenkov detectors and a flash tube hodoscope with 4 trays, and collected data on 7 million events in the energy range 0.7-20 GeV/nucleon during the 1.6 yr mission duration. Three ranges of momentum were detected, and it was found that the ratios of secondary to primary species decreased steeply with increasing energy. A progressive steepening of the energy dependence of abundance ratios from Al/Si and K/Fe was observed, which has been interpreted as a progressive decrease of the amount of primary component from Al to Na and K. The secondary to primary ratios are accounted for with an exponential pathlength distribution from Fe down to Na and N. Comparisons are made of elemental abundances in cosmic ray sources, the local galactic environment, and the solar energetic particle composition. The data is noted to be compatible with a model of an injection of cosmic ray particles by stellar flares in a two-stage acceleration process.

Koch-Miramond, L.↗
NASA NTRS1982

Image degradation in Langley 0.3-meter transonic cryogenic tunnel

The optical quality of gas in a cryogenic wind tunnel was determined by observing Sayce targets through different pathlengths of the medium. The data were used to determine the square wave response of the test gas. At conditions corresponding to 15 times ambient density, considerable decrease in response to higher spatial frequencies was noted even in the absence of flow. Under flow conditions, vibrations further degraded the response. The results are interpreted in terms of possible photogrammetric approaches to measure model deformation in large cryogenic facilities such as the National Transonic Facility.

Snow, W. L.↗
NASA NTRS1982

Visible signatures of the multi-step transition to a beam-plasma-dicharge

Observations are presented of the beam-plasma-discharge (BPD) at pressures below 4 x 10 to the -6th Torr, which show that there are three abrupt transitions in the beam-plasma interactions. The low-current A1 state (the basic beam with its noded configuration), is dominated by direct collisional ionization of the background gas. In the A2 state (the noded beam surounded by a weak halo), the ionization is supplemented by another mechanism which perhaps involves cyclotron interactions. The B and C states are distinctly separate forms of the BPD which involve a convective redistribution of beam energy as indicated by the changes in the beam nodes. The B and C states are also found to involve enhancements of between 20-100 in the power dissipation by ionization. Thus, in a 20 m pathlength, it is found that approximately 1-4 percent of the beam power is dissipated by the ionization associated with the BPD.

Hallinan, T. J.↗
NASA NTRS1983

Deformable subreflector computed by geometric optics

Using a Cassegrainian geometry, the 64-meter antenna with its distorted paraboloidal reflecting surface is forced to produce a uniform phase wavefront by a pathlength-compensating subreflector. First, the computed distortion vectors at the joints or nodes of the main reflector structure supporting the surface panels are best fitted to a paraboloid. Second, the resulting residual distortion errors are used to determine a compensating subreflector surface by ray tracing using geometric optics principles. Third, the totally corrected subreflector surface is defined by the normal directions and distances to the surface of the original symmetric hyperboloid for the purpose of evaluation. Finally, contour maps of distortions of the paraboloid reflector and the compensating subreflector are presented. A field-measured check of the subreflector in focused position as computed by the described methodology is also presented for the antenna position at horizon look with the geometry at 45 degrees elevation.

Katow, M. S.↗
NASA NTRS1983

Optical measurements of a large-scale laboratory Beam Plasma Discharge (BPD)

Optical emission measurements provided information on the spatial distribution of energetic (primary and suprathermal) electrons producing the emissions; power dissipation during beam transit of the system; and modifications of the primary beam velocity distribution. The measurements were carried out for BPD's produced in a very large vacuum chamber using a 391.4 nm scanning photometer and total light (red sensitive) TV systems. Results for conditions Eb 500 to 2000 V, injection pitch angle 0 to 75 deg, and neutral density are presented. The typical power loss in ionization in transit of the 20 m pathlength during BPD is from 3 to 10% of the input power, an order of magnitude greater than attributable to collisional ionization alone. Differences between rocket observations and the laboratory results are noted.

Bernstein, W.↗
NASA NTRS1984

Optimization of Antenna Structure Design

Optimality criteria design is applied for large antenna structures with multiple constraints on microwave performance. The constraints are on accuracy of the structure: restrictions on the microwave pathlength error, and the antenna pointing error. The examples given show convergence to low-weight feasible designs that satisfy the constraints. Truss-member sizes are automatically selected from tables of commercially available structural shapes, and approximations results from the method of selection are found moderate. The multiple constraint design is shown to be more effective in meeting constraints than the old envelop method. For practical structures, the new design method can be performed within reasonable core size and computation time.

Levy, R.↗
NASA NTRS1983

Interstellar absorption lines in the spectrum of 3C 273

Absorption lines near the rest wavelengths of the Si IV doublet (wavelengths 1393.76, 1402.77) with equivalent widths 533 and 235 mA are reported in the spectrum of QSO 3C 273. The profiles show the nature of hot gas along a high-latitude (b = 64 deg) line of sight through our entire halo. The lines have full width at half-maxima of 100 km/s, compared to an instrumental resolution of 35 km/s, are centered at zero velocity, and show no evidence for components with equivalent widths greater than 50 mA at an absolute value of v greater than 75 km/s. The absence of high peculiar velocities is consistent with published spectra of halo gas over shorter pathlengths. The implications of this result are discussed, with particular reference to the possible connection between galactic halos and QSO absorption lines, for which C IV and Si IV usually have a broader velocity range.

York, D. G.↗