Photometry and Surface Structure of the Icy Galilean Satellites
Observations of the icy Galilean satellites from both spacecraft and groundbased telescopes have
Galilean↗
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Long-range surface plasmons in electrode structures
Surface polaritons guided by symmetric double metal film structures are analyzed, with particular attention given to the attenuation of the two long-range modes that occur. It is found that long-range surface plasmon polariton modes do exist for double electrode structures over a limited range of material parameters. Guided by thin metal electrodes, surface plasmon polaritons can achieve millimeter plus propagation distances in the near infrared. It is pointed out that if the slab is electrooptic, then very low voltages will be needed to manipulate the waves. The fact that long-range modes exist simultaneously with junction tunnel plasmons may be of use in providing directional radiation from light-emitting junctions or the inverse process of light to electrical energy conversion.
Stegeman, G. I.↗
The X-37 Hot Structure Control Surface Testing
Thermal-structural testing of three hot structure control surface subcomponent test articles (STA) designed for the X-37 (Boeing Phantom Works, Huntington Beach, California) Orbital Vehicle (OV) has been completed. The test articles were subcomponents of the X-37 OV bodyflap and flaperon control surfaces.
Hudson, Larry D.↗
Structure of surfaces and their interactions
Structure of solid surfaces and their interactions
Gatos, H. C.↗
Assessment of Near-Angle Scatter on Exo-Earth Coronagraphy
Near-Angle Scatter (NAS) of the host star’s light into the coronagraph dark hole may limit the ability of a potential Habitable Worlds Observatory (HWO) to detect and characterize an Earth-like planet around a Sun-like star. This paper summarizes a 5-year investigation of the impact of NAS on high-contrast coronagraphy. Science requirements were flowed down to a draft flux ratio noise ratio (FRN) error budget with allocations for NAS. The modeled sources of NAS include correlated (low and mid-spatial) surface structure, uncorrelated surface microroughness and coating structure, particulate contamination, micrometeoroid impacts and polarization leakage. The paper develops specifications for these sources of scattered light that meet their FRN error budget allocations, distinguishing between scatter that can and cannot be modulated. The development process utilizes an analytical expression that predicts scatter throughput into the dark hole based on BRDF/BSDF. Using this relationship, Photon Engineering performed a FRED® straylight analysis of the HWO EAC-1 (Exploratory Analytical Case #1) coronagraph to parametrically study predicted scattered light contrast in the dark hole. The model revealed that primary mirror microroughness or contamination is not a significant source of scattered light; the most critical surfaces are the smallest and those located closest to the coronagraph focal plane mask. The assessment found that uncorrelated microstructure, contamination, and micrometeoroid impacts require more investigation and potential significant sources of unmodulated scattered light, and highlights that slow thermal wavefront drift is an order of magnitude more impactful than fast mechanical jitter.
coronagraphy↗
Surface topography of single crystals of face-centered-cubic, body-centered-cubic, sodium chloride, diamond, and zinc-blende structures
Surface topography of single crystals of face- centered-cubic, body-centered-cubic, sodium chloride, diamond, and zinc blende structures
SODIUM CHLORIDE↗
Electronic materials high-T(sub c) superconductivity polymers and composites structural materials surface science and catalysts industry participation
The fifth year of the Center for Advanced Materials was marked primarily by the significant scientific accomplishments of the research programs. The Electronics Materials program continued its work on the growth and characterization of gallium arsenide crystals, and the development of theories to understand the nature and distribution of defects in the crystals. The High Tc Superconductivity Program continued to make significant contributions to the field in theoretical and experimental work on both bulk materials and thin films and devices. The Ceramic Processing group developed a new technique for cladding YBCO superconductors for high current applications in work with the Electric Power Research Institute. The Polymers and Composites program published a number of important studies involving atomistic simulations of polymer surfaces with excellent correlations to experimental results. The new Enzymatic Synthesis of Materials project produced its first fluorinated polymers and successfully began engineering enzymes designed for materials synthesis. The structural Materials Program continued work on novel alloys, development of processing methods for advanced ceramics, and characterization of mechanical properties of these materials, including the newly documented characterization of cyclic fatigue crack propagation behavior in toughened ceramics. Finally, the Surface Science and Catalysis program made significant contributions to the understanding of microporous catalysts and the nature of surface structures and interface compounds.
Source record↗
Limitations of spectral measures and observations of the group structure of surface waves
Wave-group structure, which plays a significant role in flux processes and the mechanics of the transfer of wave energy and momentum to the mean current field, is studied. The origin of wave groups, in particular sideband instabilities, the effects of amplitude variations on wave frequency and of wave damping on isolated groups, and flow separation over waves, is discussed. The mechanisms that cause the group formation are compared to the dynamics that result in wave propagation. The bifurcation and shift in wave modulations, and the possible existence of a unique asymptotic statistical state for the wave-modulation field are examined.
Mollo-Christensen, Erik↗
HIGHLY UNDEREXPANDED EXHAUST JETS AGAINST ADJACENT SURFACES
Structural damage and stability problems due to exhaust jet impingement on nearby rocket vehicle surfaces
STRUCTURAL FATIGUE↗
Engineering, construction, and operations in space II; Proceedings of Space 90, the Second International Conference, Albuquerque, NM, Apr. 22-26, 1990. Vols. 1 & 2
Attention is given to such topics as the processing of lunar soils, the automated processing of extraterrestrial materials, lunar excavation and mining, lunar oxygen, lunar base development, lunar surface structures, planetary surface transportation, and Mars missions. Papers are also presented on the Space Station, space debris, robotics and automated processing, structures and structural response, Mission to Planet Earth, life support systems, space power, human factors, artificial gravity, and education.
Johnson, Stewart W.↗
Structure and properties of solid surfaces
Difficulties in experimental studies of crystalline surfaces are related to the fact that surface atoms have an intrinsic tendency to react with their environment. A second problem is connected with the effective thickness of surfaces, which ranges from one to several atom layers. The phenomenology of surface interactions with gases are considered, taking into account physical adsorption, chemisorption, and the oxidation of surfaces. Studies of the surface structure are discussed, giving attention to field emission microscopy, field-ion microscopy, electron diffraction techniques, Auger spectroscopy, scanning electron microscopy, electron probe microanalysis, ion microprobe methods, and low-energy backscattering spectroscopy. Investigations of semiconductor surfaces are also described.
Gatos, H. C.↗
Study of the Brazil and Falkland currents using their images of Nimbus 5 and oceanographic data in 1972 - 1973
The Western Edge of the Sub-tropical Convergence of the South-western Atlantic Ocean, called the Front, which is a thermal discontinuity between the Brazil and Falkland Currents, was studied utilizing the Temperature Humidity Infrared Radiometer (THIR) of Nimbus V in the 10.5 to 12.5 micrometers channel and historical oceanographic data. Some important results obtained are: the oceanographic Front could be detected from Nimbus THIR data; oceanographic charts showed that the transition zone where the Brazil and the Falkland Currents meet was the Front detected from satellite data; ocean current speeds calculated with THIR data were of the same order of magnitude as those calculated oceanographically; fisheries statistics for Pargo Roseo showed that the maximum catches were in September of 1973, in the period when the Front was observed most distinctly and clearly. The results showed the great potentiality of satellite data to study surface thermal structures, surface currents and oceanic fisheries.
Tseng, Y. C.↗
Adhesion and wear resistance of materials
Recent studies into the nature of bonding at the interface between two solids in contact or a solid and deposited film have provided a better understanding of those properties important to the adhesive wear resistance of materials. Analytical and experimental progress are reviewed. For simple metal systems the adhesive bond forces are related to electronic wave function overlap. With metals in contact with nonmetals, molecular-orbital energy, and density of states, respectively can provide insight into adhesion and wear. Experimental results are presented which correlate adhesive forces measured between solids and the electronic surface structures. Orientation, surface reconstruction, surface segregation, adsorption are all shown to influence adhesive interfacial strength. The interrelationship between adhesion and the wear of the various materials as well as the life of coatings applied to substrates are discussed. Metallic systems addressed include simple metals and alloys and these materials in contact with themselves, both oxide and nonoxide ceramics, diamond, polymers, and inorganic coating compounds, h as diamondlike carbon.
Buckley, D. H.↗
Observations of the properties of the water surface roughness structure under the action of wind and waves
The statistical properties of a water surface roughness structure subjected to wind and waves are analyzed in a laboratory wind wave channel. The surface slope is derived using elevation measurements and the pitot tube is employed to measure wind speed. The transient responses of the surface slope to a calm condition and low, medium, and high wind conditions are studied. Two methods for determining a critical wind speed range are described.
Long, Steven R.↗
Work Functions for Models of Scandate Surfaces
The electronic structure, surface dipole properties, and work functions of scandate surfaces have been investigated using the fully relativistic scattered-wave cluster approach. Three different types of model surfaces are considered: (1) a monolayer of Ba-Sc-O on W(100), (2) Ba or BaO adsorbed on Sc2O3 + W, and (3) BaO on SC2O3 + WO3. Changes in the work function due to Ba or BaO adsorption on the different surfaces are calculated by employing the depolarization model of interacting surface dipoles. The largest work function change and the lowest work function of 1.54 eV are obtained for Ba adsorbed on the Sc-O monolayer on W(100). The adsorption of Ba on Sc2O3 + W does not lead to a low work function, but the adsorption of BaO results in a work function of about 1.6-1.9 eV. BaO adsorbed on Sc2O3 + WO3, or scandium tungstates, may also lead to low work functions.
Mueller, Wolfgang↗
Dynamic Response of X-37 Hot Structure Control Surfaces Exposed to Controlled Reverberant Acoustic Excitation
This document represents a compilation of three informal reports from reverberant acoustic tests performed on X-37 hot structure control surfaces in the NASA Langley Research Center Structural Acoustics Loads and Transmission (SALT) facility. The first test was performed on a carbon-silicone carbide flaperon subcomponent on February 24, 2004. The second test was performed on a carbon-carbon ruddervator subcomponent on May 27, 2004. The third test was performed on a carbon-carbon flaperon subcomponent on June 30, 2004.
Grosveld, Ferdinand W.↗
Possible structure of lunar surface layer
Lunar surface layer structure determination based on effective thermal conductivity coefficient
LUNAR SURFACE↗
Ion beam sputter etching of orthopedic implanted alloy MP35N and resulting effects on fatigue
The effects of two types of argon ion sputter etched surface structures on the tensile stress fatigue properties of orthopedic implant alloy MP35N were investigated. One surface structure was a natural texture resulting from direct bombardment by 1 keV argon ions. The other structure was a pattern of square holes milled into the surface by a 1 keV argon ion beam through a Ni screen mask. The etched surfaces were subjected to tensile stress only in fatigue tests designed to simulate the cyclic load conditions experienced by the stems of artificial hip joint implants. Both types of sputter etched surface structures were found to reduce the fatigue strength below that of smooth surface MP35N.
Wintucky, E. G.↗