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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 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Solar wind rare gas analysis: Trapped solar wind helium and neon in Surveyor 3 material

The He-4 and Ne-20 contents in sections of the Surveyor 3 support strut samples were determined by optical and scanning electron microscopy and are compared to the results of the Apollo solar wind composition (SWC) experiments. The He-4/Ne-20 ratio in the samples from the sunlit side of the strut was approximately 300; the ratios determined in Apollo 12 lunar fines and SWC foil were below 100. The He-4/He-3 ratios were also determined, and the ratio obtained from Surveyor 3 material is higher than those found with Apollo 11 and 12 SWC experiments. The effects of spallation by cosmic rays or solar protons, stripping by cosmic ray or energetic solar alpha particles, recycling of solar wind He and radiogenic Ne, He from terrestrial atmosphere, mass discrimination near the moon, mass dependence of trapping probability, diffusion, and contamination by lunar dust are considered.

Buehler, F.↗
NASA NTRS1972

Elastic and inelastic scattering of positrons in gases and solids

Three apparatuses were designed and built: The first, which is now operative, was designed to study the details of positron thermalization in solids and the subsequent emission of the low energy positrons from moderating foils; The second apparatus now under test is a positron bottle similar in design to an electron trap. It was built to store positrons at a fixed energy and to look at the number of stored positrons (storage time) as a function of a scattering gas in the vacuum chamber. The third apparatus is a crossed beam apparatus where positron-, alkali scattering will be studied. Much of the apparatus is now under test with electrons.

Mcgowan, J. W.↗
NASA NTRS1972

Design, fabrication and calibration of alpha particle densitometers for measuring planetary atmospheric density

An alpha particle densitometer was developed for possible application to measurement of the atmospheric density-altitude profile on Martian entry. The device uses an Am-241 radioactive-foil source, which emits a distributed energy spectrum, located about 25 to 75 cm from a semiconductor detector. System response - defined as the number of alphas per second reaching the detector with energy above a fixed threshold - is given for Ar and CO2. The altitude profile of density measurement accuracy is given for a pure CO2 atmosphere with 5 mb surface pressure. The entire unit, including dc-dc converters, requires less than 350 milliwatts of power from +28 volts, weighs about 0.85 lb and occupies less than 15 cubic inches volume.

Sellers, B.↗
NASA NTRS1971

High temperature insulation for reradiative TPS.

This paper presents the results of a program to evaluate thermal insulations for use under the radiative TPS of a shuttle orbiter vehicle. Evaluations were made for survival under the multimission requirements of shuttle acoustic/vibration loads and thermal profiles. During the first year of the program a total of 1100 specimen-cycles were completed using metal foil packaged refractory fiber insulations.

Hughes, T. A.↗
NASA NTRS1971

Energy levels and mean lives of Cl II to Cl VII.

Investigation of the spectra of chlorine between 500 and 2800 A using the beam-foil technique. Over 200 multiplets have been observed, many of which had not been reported earlier. A number of such transitions could be classified, and several new term values are proposed for Cl IV, Cl V, Cl VI , and Cl VII. Mean lives of various excited levels were measured for Cl II to Cl VII. The results are compared with theoretical calculations and other measurements in appropriate isoelectronic systems.

Bashkin, S.↗
NASA NTRS1971

Powder-metallurgy superalloy strengthened by a secondary gamma phase.

Description of experiments in which prealloyed powders of superalloy compositions were consolidated by extrusion after the strengthening by precipitation of a body-centered tetragonal gamma secondary Ni3 Ta phase. Thin foil electron microscopy showed that the mechanical properties of the resultant powder-metallurgy product were correlated with its microstructure. The product exhibited high strength at 1200 F without loss of ductility, after thermomechanical treatment and aging.

Kotval, P. S.↗
NASA NTRS1972

Fe I oscillator strengths determined from anomalous dispersion of shock-heated gases.

Determination of Fe I oscillator strengths by the hook method on shock-heated gases. Within the given errors these values agree with oscillator strengths obtained by other methods, including wall-stabilized arc and shock-tube emission, the beam-foil technique, and delayed-coincidence measurements, except that the data reported in the present article tend to be somewhat higher. If it is assumed that no change occurs in atmospheric models, the authors' f-value scale would suggest a solar abundance at the lower limit of the recently published values - namely, log (A sub Fe/A sub H) + 12 = 7.4. This study demonstrates the effectiveness of the hook method for quantitative spectroscopy on shock-heated gases and points up its usefulness for gas diagnostics on optically thick lines.

Huber, M. C. E.↗
NASA NTRS1972

Design of the particles experiment subsystem of the Apollo lunar subsatellite.

In August 1971 an eighty pound subsatellite was ejected from Apollo 15 into lunar orbit. The subsatellite is expected to remain in lunar orbit for at least one year. The Particles Experiment Subsystem of the subsatellite was designed to implement the Particle Shadows/Boundary Layer Experiment. The objective of the experiment is to obtain data for the study of the formation and the dynamics of the earth's magnetosphere, the interaction of plasmas with the moon, and the physics of solar flares. The design of the particle detector telescopes is considered together with details of collimator design, silicon detectors, the absorber foil, and the power subsystems. The instrument performance in lunar orbit is discussed.

Baum, J. J.↗
NASA NTRS1972

Investigation of a possible solar-wind darkening of the lunar surface by photoelectron spectroscopy.

Detailed sequential study by photoelectron spectroscopy of the change in valence states of iron in Fe2O3, Fe3O4, FeO, and Fe foil samples, showing that chemical reduction does take place on the sample surface when argon ion bombardment occurs. These spectra give evidence that, after prolonged ion bombardment, the surface of all four samples consisted predominantly of iron in the metallic state. Argon ion sputtering of 15 silicate and oxide samples under similar experimental conditions produced surface darkening only in samples containing iron. Monitoring of the photoelectron peak of carbon during the experiment indicates that ion-bombardment darkening is not due to the buildup of hydrocarbon surface contaminants in the oil-free high-vacuum system used by the authors. On the basis of these studies, it is concluded that solar-wind bombardment should be included as one of the possible mechanisms for producing darkening of the lunar surface.

Yin, L. I.↗
NASA NTRS1971

Interaction of high-intensity laser radiation with metals.

The interaction is characterized by the production of plasma, within which the primary absorption occurs. Absorption of laser radiation by a plasma may occur by several processes. The absorption process called 'inverse bremsstrahlung' is discussed. The interaction of a laser beam with the plasma produced from a thick metal target was studied. The results of the measurements of the ion kinetic energies are presented in a graph. In addition to measurements with thick targets, information was also obtained with a thin foil of gold.

Linlor, W. I.↗
NASA NTRS1972

Quantum beats in transitions from levels subject to optical cascades.

Discussion of the g values of weakly aligned O II and O III multiplet levels subject to strong optical cascades, obtained by means of a beam-foil quantum beat method. Within the measurement precision limits of nearly plus or minus 1%, the effects of the optical cascades on the measured g values are shown to be negligible.

Liu, C. J.↗
NASA NTRS1972

Thin film fuel cell electrodes.

Earlier work shows that fuel cell electrodes prepared by sputtering thin films of platinum on porous vycor substrates avoid diffusion limitations even at high current densities. The presented study shows that the specific activity of sputtered platinum is not unusually high. Performance limitations are found to be controlled by physical processes, even at low loadings. Catalyst activity is strongly influenced by platinum sputtering parameters, which seemingly change the surface area of the catalyst layer. The use of porous nickel as a substrate shows that pore size of the substrate is an important parameter. It is noted that electrode performance increases with increasing loading for catalyst layers up to two microns thick, thus showing the physical properties of the sputtered layer to be different from platinum foil. Electrode performance is also sensitive to changing differential pressure across the electrode. The application of sputtered catalyst layers to fuel cell matrices for the purpose of obtaining thin total cells appears feasible.

Asher, W. J.↗
NASA NTRS1972

Determination of Burgers vectors in close-packed metals using g.b = 2 contrast.

Reexamination of dislocation images giving double contrast in the electron microscope for g.b = 2 as a possible means for Burgers vector determinations. In fcc foils which have been cut parallel to an active slip plane, the g.b = 2 criterion provides a quick positive Burgers vector analysis which can be carried out during observation. The method is also applicable to basal dislocations in hcp. A comparison between calculated two-beam profiles and experimental images in aluminum is discussed, and several commonly observed characteristics of g.b = 2 contrast are described.

Kestenbach, H.-J.↗
NASA NTRS1972

Static and dynamic fatigue behavior of glass filament-wound pressure vessels at ambient and cryogenic temperatures.

Investigation of the pressure load carrying capacity and fatigue strength of filament-wound glass-reinforced plastic pressure vessels subjected to static and cyclic loading at ambient and cryogenic (liquid nitrogen) temperature environments. The results indicate that the static fatigue problem is not critical at cryogenic temperatures. Under static loading at liquid nitrogen temperature, a reinforced plastic cylinder sustained pressurization for 88 days without failure at about 90% of the single cycle burst strength. At ambient temperature, the static life at 90% of the burst strength was about 7 min. Under cyclic loading in liquid nitrogen, no failure resulted after 1509 cycles at 55% of the single cycle burst strength. Under the same cyclic loading at ambient temperature, the test results would predict failure in the reinforced plastic. The results of similar tests upon adhesively bonded polyimide aluminum-foil lined cylinders are also reviewed.-

Hanson, M. P.↗
NASA NTRS1972

Asymmetries in gamma scattering by Fe-57.

Experiments were conducted with a setup in which a Co-57 single-line source was driven by a constant-acceleration motor. The 14.4-keV gamma rays emitted from the iron foil scatterer were detected by a proportional counter filled with krypton and carbon dioxide. The interference for individual Zeeman hyperfine transitions in a magnetic field was calculated. It was found that beside the cos phi angular dependence of line shape asymmetry, there exists a sin phi intensity dependence for some of the hyperfine transitions.

Lee, L. Y.↗
NASA NTRS1972

Diffusion bonded columbium panels for the shuttle heat shield.

Work at North American Rockwell in the development of a satisfactory panel diffusion bonding method for Nb shuttle orbiter heat shield panel designs is reviewed. The topics include the diffusion bonding process, panel fabrication and quality control. A practicable Nb alloy diffusion bonding method, using a Ti foil interleaf, is described and is characterized as one providing a production basis at competitive cost.

Korb, L. J.↗
NASA NTRS1964

Fuel Retention Improvement at High Temperatures in Tungsten-Uranium Dioxide Dispersion Fuel Elements by Plasma-Spray Cladding

An investigation was undertaken to determine the feasibility of depositing integrally bonded plasma-sprayed tungsten coatings onto 80-volume-percent tungsten - 20-volume-percent uranium dioxide composites. These composites were face clad with thin tungsten foil to inhibit uranium dioxide loss at elevated temperatures, but loss at the unclad edges was still significant. By preheating the composite substrates to approximately 3700 degrees F in a nitrogen environment, metallurgically bonded tungsten coatings could be obtained directly by plasma spraying. Furthermore, even though these coatings were thin and somewhat porous, they greatly inhibited the loss of uranium dioxide. For example, a specimen that was face clad but had no edge cladding lost 5.8 percent uranium dioxide after 2 hours at 4750 dgrees F in flowing hydrogen. A similar specimen with plasma-spray-coated edges, however, lost only 0.75 percent uranium dioxide under the same testing conditions.

Grisaffe, Salvatore J.↗
NASA NTRS1973

Manufacture of large, lightweight parabolic antennas

Antenna was produced in segments. Parabole sections were built up as aluminum foil sandwich with core bonded by film adhesive; whole structure was oven-cured after assembly. Structure was assembled with special tool for splice-bonding segments into complete dish, and inflatable bladder to apply pressure at joints during cure.

Hooper, S. W.↗