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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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NASA NTRS1978

The Martian satellites - 100 years on

Studies of Phobos and Deimos, the two satellites of Mars, may provide the best observations yet of the material populating the asteroid belt. Viking observations of Phobos showing crater chains and striations are analyzed, and Mariner-9 photometry exhibiting the albedo of the satellite is discussed. A mass determination for Phobos results in a value of 1.1 times 10 to the 19th power g; the mean density of the satellite is set at about 2 g per cu cm, a value suggesting formation of the satellite from material in the asteroid belt.

Hunt, G. E.↗
NASA NTRS1978

Interdisciplinary investigations of comparative planetology

Research supported wholly or in part by NASA's Planetary Programs Office is summarized. Topics covered include: the evaporation of ice in planetary atmospheres: ice-covered rivers on Mars; reducing greenhouses and the temperature history of Earth and Mars; particle motion on Mars inferred from the Viking Lander cameras; the nature and visibility of crater-associated streaks on Mars; the equilibrium figure of Phobos and other small bodies; striations on Phobos; radiation pressure and Poynting-Robertson drag for small spherical particles; direct imaging of extra-solar planets with stationary occultations; the relation between planetology and conventional astrophysics; remote spectral studies and in situ X-ray fluorescence analysis of the Martian surface; small channels on Mars; junction angles of Martian channels; constraints on Aeolian phenomena on Mars; the geology of Mars; and the flow of erosional debris on the Martian terrain.

Sagan, C.↗
NASA NTRS1979

System and method for obtaining wide screen Schlieren photographs

A system for use in Schlieren photography includes (1) a viewing screen adjacently related to a large grating; (2) a small grating disposed in spaced relation with the large grating; (3) a transparent retainer for confining a transparent medium between the gratings; and (4) optics for imaging the small grating on the large grating. A light source and optically aligned lens are used to project a beam of light along axes extending through the small grating and strike the large grating, subsequent to passing through the medium. A Schlieren image of striations resulting from distortions of light rays proposed by the medium are formed on the screen. A camera is used to photograph the Schlieren image projected on the large screen.

Parthasarathy, S. P.↗
NASA NTRS1979

High performance N2O4/amine elements blowapart

An experimental and analytical program was conducted to develop an understanding of the mechanisms controlling hypergolic propellant reactive stream separation (RSS). RSS is a combustion induced phenomenon that results in striation of hypergolic propellant oxidizer and fuel sprays fans. This reduced intraelement mixing can influence thrust chamber performance, heat transfer, and stability. The program and product were the development of design criteria for coping with RSS to allow the design of high performance, stable injectors.

Lawver, B. R.↗
NASA NTRS1979

Photographic combustion characterization of LOX/hydrocarbon type propellants

Single element injectors and two fuels were tested with the aim of photographically characterizing observed combustion phenomena. The three injectors tested were the O-F-O triplet, the transverse like on like (TLOL), and the rectangular unlike doublet (RUD). The fuels tested were RP-1 and propane. The hot firings were conducted in a specifically constructed chamber fitted with quartz windows for photographically viewing the impingement spray field. All LOX/HC testing demonstrated coking with the RP-1 fuel leaving far more soot than the propane fuel. No fuel freezing or popping was experienced under the test conditions evaluated. Carbon particle emission and combustion light brilliance increased with Pc for both fuels although RP-1 was far more energetic in this respect. The RSS phenomena appear to be present in the high Pc tests as evidenced by striations in the spray pattern and by separate fuel rich and oxidizer rich areas. The RUD element was also tested as a fuel rich gas generator element by switching the propellant circuits. Excessive sooting occurred at this low mixture ratio (0.55), precluding photographic data.

Judd, D. C.↗
NASA NTRS1980

Problems with state-of-the-art float zone silicon

An application in which CCD optical imaging arrays with 250,000 elements are fabricated from the best commercially available float zone Si is described. Two image defects are described which appear to be related to the starting material. The striation effect appears to be caused by resistivity and recombination center variations. Up to 30 percent variations in resistivity was measured across a sample.

Jastrzebski, L.↗
NASA NTRS1982

Microstructural effects on the room and elevated temperature low cycle fatigue behavior of Waspaloy

Longitudinal specimens of Waspaloy containing either coarse grains with small gamma or fine grains with large gamma were tested in air at a frequency of 0.33 Hz or 0.50 Hz. The coarse grained structures exhibited planar slip on (III) planes and precipitate shearing at all temperatures. Cracks initiated by a Stage 1 mechanism and propagated by a striation forming mechanism. At 700 C and 800 C, cleavage and intergranular cracking were observed. Testing at 500 C, 700 C, and 800 C caused precipitation of grain boundary carbides. At 700 C, carbides precipitated on slip bands. The fine grained structures exhibited planar slip on (111) planes. Dislocations looped the large gamma precipitates. This structure led to stress saturation and propagation was observed. Increasing temperatures resulted in increased specimen oxidation for both heat treatments. Slip band and grain boundary oxidation were observed. At 800 C, oxidized grain boundaries were cracked by intersecting slip bands which resulted in intergranular failure. The fine specimens had crack initiation later in the fatigue life, but with more rapid propagation crack propagation.

Lerch, B. A.↗
NASA NTRS1981

Radiographic evidence of disuse osteoporosis in the monkey /M. nemestrina/

Radiological techniques were utilized for monitoring progressive changes in compact bone in the tibia of monkeys during experimentally induced osteopenia. Bone mass loss in the tibia during restraint was evaluated from radiographs, from bone mineral analysis, and from images reconstructed from gamma ray computerized tomography. The losses during 6 months of restraint tended to occur predominantly in the proximal tibia and were characterized by subperiosteal bone loss, intracortical striations, and scalloped endosteal surfaces. Bone mineral content in the cross section of the tibia declined 17-21%. In 6 months of recovery, the mineral content of the proximal tibia remained depressed.

Young, D. R.↗
NASA NTRS1981

Crack tip deformation and fatigue crack growth

Recent research on fatigue crack growth is summarized. Topics discussed include the use of the differential stress intensity factor to characterize crack tip deformation, the use of the unzipping model to study the growth of microcracks and the fatigue crack growth in a ferritic-martensitic steel, and the development of a model of fatige crack growth threshold. It is shown that in the case of small yielding, the differential stress intensity factor provides an adequate description of cyclic plastic deformation at the crack tip and correlates well with the crack growth rate. The unzipping model based on crack tip shear decohesion process is found to be in good agreement with the measured crack growth and striation spacing measurements. The proposed model of crack growth threshold gives correct predictions of the crack growth behavior in the near-threshold region.

Liu, H.-W.↗
NASA NTRS1982

Bidirectional reflectance distribution function of the Infrared Astronomical Satellite solar-shield material

The Infrared Astronomical Satellite (IRAS) telescope has an outer shield on it which is used to reduce the amount of thermal radiation that enters the telescope. The shield forms the first part of the baffle structure which reduces the photon incidence on the focal plane. It was, therefore, necessary to model this structure for scattering, and a required input for such modeling is the scattering characteristic of this surface. Attention is given to the measurement of the bidirectional reflectance distribution function (BRDF), the reflected radiance divided by the incident irradiance at 10.6 micrometers, 118 micrometers, and at several angles of incidence. Visual observation of the gold sample shows that there are striations which line up in a single direction. The data were, therefore, taken with the sample oriented in each of two directions.

Hubbs, J. E.↗
NASA NTRS1983

The shape of cooling filaments in old supernova remnants

The evolution of a filament in an old supernova remnant is investigated in two dimensions using analytical methods to determine its structure and stability and to show whether it collapses into a sheet or a cylinder. All parameters are assumed constant along the length of the feature. The cross section of the filament is found to flatten as it cools, and to degenerate into a thin sheet which is unstable to asymmetric warping disturbances. This probably leads to a number of parallel striations as the filament splits up, consistent with observations in the Cygnus Loop. The ratio of depth to width is typically 10:1, and so the feature may appear to be tubelike or a sheet, depending on perspective. The application to Vela and Puppis, IC 443, S 147, and CTB 1 is pointed out.

Smith, M. D.↗
NASA NTRS1984

Differential rotation in a solar-driven quasi-axisymmetric circulation

The concept of a quasi-axisymmetric circulation is used to explore the global scale dynamics of planetary atmospheres. A numerical circulation model applicable to Jupiter is presented, and an analytical study is performed elucidating the conditions leading to differential rotation in an atmosphere which is convectively unstable. A linear system forced by solar differential heating is considered, with nonlinear effects arising from advection being represented in the form of eddy diffusion. An empirical, latitudinal spectrum of the observed zonal wind field on Jupiter is discussed. Numerical solutions are presented which reveal banded wind fields with alternating and equatorial zonal jets and a multicellular Ferrel-Thomson meridional circulation consistent with the observed cloud striations on Jupiter. The vertical derivatives are parameterized to construct a simplified one-layer model.

Mayr, H. G.↗
NASA NTRS1984

On the use of marker loads and replicas for measuring growth rates for small cracks

The initiation and growth of small cracks (5-500 microns) from edge notches in 2024-T3 aluminum alloy sheets were studied under constant-amplitude loading. Two methods were used to measure crack shape and size. In the first method, striation marker bands were periodically formed along the crack front by interrupting the constant-amplitude loading by either an elevated R-ratio load sequence, or by an overload sequence. In each case the marker loading was selected so as to have minimal influence on the growth rate under the primary loading. In the second method, the surface crack length was monitored by taking surface replicas at regular intervals. The marker band techniques did not provide reliable crack length and crack shape information for cracks smaller than 2 mm. The replica technique provided accurate information for surface crack length at all crack lengths, and fracture tests on specimens with small cracks provided crack-shape information.

Swain, M. H.↗
NASA NTRS1984

On the use of marker loads and replicas for measuring growth rates for small cracks

The initiation and growth of small cracks (5-500 microns m) from edge notches in 2024-T3 aluminum alloy sheets were studied under constant amplitude loading. Two methods were used to measure crack shape and size. In the first method, striation marker bands were periodically formed along the crack front by interrupting the constant amplitude loading by either an elevated R-ratio load sequence, or by an overload sequence. In the second method, the surface crack length was monitored by taking surface replicas at regular intervals. The marker band techniques did not provide reliable crack length and crack shape information for cracks smaller than 2 mm. The replica technique provided accurate information for surface crack length at all crack lengths, and fracture tests on specimens with small cracks provided crack-shape information. Crack growth rates were plotted against the stress intensity factor ranges. The results exhibited the small crack effect, in that the small cracks grew faster than large cracks at the same stress-intensity factor range. A crack closure model was also used to analyze the growth of small cracks from small (inclusion) defects at the notch surface.

Swain, M. H.↗
NASA NTRS1984

NASA research on viscous drag reduction II

An assessment is made of determinations from NASA research on viscous drag reduction for aircraft, which extends to both laminar flow control and turbulent drag reduction methods. Attention is given to achievements in natural and suction-induced laminar flow control, hybrid systems incorporating both principles, turbulent drag reduction by means of low momentum fluid injection from discrete tangential slots, large eddy breakup devices, and an 'ion wind' system that functions on an inversion of the corona wind phenomenon. Surface-based drag reduction effects under study involve 'riblets', or small longitudinal surface striations, convex curvatures, and rigid, wavy walls.

Bushnell, D. M.↗
NASA NTRS1985

Mapping of electric field structures from the equatorial F region to the underlying E region

The theories of electrostatic fields in the equatorial ionosphere attributed to Farley (1960) and Spreiter and Briggs (1961) are reviewed, and a hybrid of these theories is applied to investigate how spread F irrregularities map down to the underlying E region. It is found that structures larger than 1 km map easily through the E region, while smaller structures do not. This implies that in general, subkilometer F region irregularities cannot directly generate image striations in the underlying E region, a result which affects previous investigations of the role of images in equatorial spread F.

Labelle, J.↗
NASA NTRS1985

Observations of E and F region Mg(+) from Spacelab 1

Images of airglow at 2800 A were taken on the Spacelab 1 Shuttle mission and have been interpreted to be solar resonant emission of magnesium ions. On two orbital passes, observations were made near the magnetic equator while observing in the 2800-A channel. The observations were made near the sunset terminator (approximately 1800 LT), in winter (1983, day 335). Three separate emission clouds were observed, all of which extended well into the F region. The location of the clouds in horizontal space is shown. The processed images have been pseudocolored to highlight the intensity distribution in the clouds. Observations included clouds with apparent magnetic-field aligned striations. Bright emissions were observed at the magnetic equator, at 12-deg north magnetic latitude, and at 12-deg south magnentic latitude. Cloud-center brightnesses varied between 680 rayleighs and 1700 rayleighs.

Mende, S. B.↗
NASA NTRS1986

Combined Devices for Turbulent-Drag Reduction

Aircraft skin-friction drag reduced as much as 15 percent. One effective drag-reduction technique involves use of riblets. Riblets are longitudinal striations or grooves machined on originally smooth surface. Grooves alined with flow. Grooves have depths and spacings on order of turbulent wallstreak and burst dimensions and designed to change near-wall structure of turbulent boundary layer. Another approach, using large-eddy-breakup (LEBU) devices, or turbulence manipulators or ribbons also demonstrated reductions in local skin friction and net drag in air. LEBU device consists of thin, ribbonlike strips or airfoils suspended parallel to test surface and positioned within turbulent boundary layer. Technique potentially reduce net skin-friction drag by at least 15 percent on turbulent boundary layer of aircraft, representing possible annual savings in fuel costs of $300 to $400 million for U.S. commercial fleet. Also applicable to frictionloss reduction inside pipes and ducts, contributing to increased efficiency of pumps, heat exchangers, air conditioners, and other devices involving fluid flow.

Walsh, M. J.↗