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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Radiant energy absorption enhancement in optical imaging systems

Reimaging system efficiently uses incident light and overcomes previous imaging detector problems. Optical system collects reflected and focal plane transmitted light and redirects it so it again impinges on focal plane in register with original image. Reimaging unabsorbed light increases light absorption and detector use probability.

Brown, R. M.↗
NASA NTRS1971

Microorganism sample device

Device, based on gel-impingement technique, collects microorganism specimens from circulating air streams. Device is useful to air pollution studies involving the collection of airborne microbial specimens.

Reed, L. L.↗
NASA NTRS1971

Experimental investigation of the performance of vortex generators mounted in the supersonic portion of a mixed-compression inlet

Vortex generators were investigated as a means of controlling the throat boundary layer in a Mach 2.5 mixed-compression inlet. With or without throat bleed, the generators were unable to produce the inlet peak recoveries available with good performance bleed. Generators placed on the unbled inlet centerbody ahead of the cowl shock impingement point degraded inlet performance. Generators placed further aft on the unbled centerbody, but ahead of the throat, improved inlet performance at conditions where the terminal shock could cause boundary layer separation. Adding generators to the inlet with throat bleed reduced performance. Bleed aft of the generators degraded the vortex flow field.

Michell, G. A.↗
NASA NTRS1971

Formation of giant H II regions following supernova explosions

The principal optical properties of type I supernovae are summarized. These include the light curve and the spectrum. The spectra consist of broad bands with very little continuum. According to the theory presented, the observed light is principally fluorescence, excited in the medium surrounding the supernova by ultraviolet radiation originating from the explosion. It is proposed that the spectrum that impinges on the fluorescent medium while emission is taking place must fall abruptly across the Lyman edge of He II. Such a filtering action is plausibly provided by a much denser internal region, rich in helium, immediately surrounding the exploding object. This will form a Stromgren sphere during the time the intense UV pulse is passing through it. The dense region also slows down the photons below the edge by Thomson scattering, thereby spreading out the UV pulse in time. Various proposed mechanisms for the production of ionization in the Gum nebula are discussed.

Sartori, L.↗
NASA NTRS1971

A study of the round jet/plane wall flow field

Impingement angles, between the axisymmetric jet axis and the plane wall, from zero to 15 degrees have been examined for nozzle heights of 0.75, 1.0, 1.5 and 2.0 diameters and for: (1) a fully developed pipe flow, and (2) a relatively uniform exit velocity condition. Velocity measurements have been used to define isotach contours and to determine mass, momentum and energy flux values for the near field (within five diameters) of the jet. Surface pressure measurements have been used to define surface pressure forces and jet centerline trajectories. The geometric and flow conditions examined and the interpretation of the results have been motivated by the externally blown flap STOL aircraft application.

Foss, J. F.↗
NASA NTRS1971

Ethiopian Tertiary dike swarms

Mapping of the Ethiopian rift and Afar margins revealed the existence of Tertiary dike swarms. The structural relations of these swarms and the fed lava pile to monoclinal warping of the margins partly reflect a style of continental margin tectonics found in other parts of the world. In Ethiopia, however, conjugate dike trends appear to be unusually strongly developed. Relation of dikes to subsequent margin faulting is ambiguous, and there are instances where the two phenomena are spatially separate and of differing trends. There is no evidence for lateral migration with time of dike injection toward the rift zone. No separate impingement of Red Sea, Gulf of Aden, and African rift system stress fields on the Ethiopian region can be demonstrated from the Tertiary dike swarms. Rather, a single, regional paleostress field existed, suggestive of a focus beneath the central Ethiopian plateau. This stress field was dominated by tension: there is no cogent evidence for shearing along the rift margins. A gentle compression along the rift floor is indicated. A peculiar sympathy of dike hade directions at given localities is evident.

Mohr, P. A.↗
NASA NTRS1971

Performance of a neutralizer for electron bombardment thruster

Results of the SERT II flight indicate that the hollow cathode neutralizer not only represents a power and propellant weight penalty but can be a contributing cause to accelerator grid erosion. Tests with a 30-cm diameter thruster show that a neutralizer position of approximately 9 cm axially downstream of the accelerator grid and approximately 9 cm radially away from the outer edge of the accelerator grid and pointing parallel to the thruster axis provides the best overall performance. The estimated grid wear rate was less than 0.08 mm in 10,000 hours. The coupling voltage was approximately 17 volts at a neutralizer flow rate of 22 equivalent milliamperes of mercury and a beam current of 1.5 amperes. Neutralizer power was 31 watts and the effect of neutralizer flow on overall propellant utilization efficiency is a 1.2 percentage point reduction at a thruster utilization efficiency of 90 percent. The neutralizer position defined in tests with a 30 cm thruster was tested with a 15 cm SERT II thruster. When the neutralizer was relocated further downstream with this different orientation, accelerator impingement current due to neutralizer operation was reduced by approximately a factor of seven and was nearly independent of neutralizer operation.

Bechtel, R. T.↗