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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Optical-data-processing properties of a liquid-crystal television spatial light modulator

The potential of an extremely inexpensive liquid-crystal television (LCTV) as a two-dimensional spatial light modulator has been investigated. The LCTV modulates the transmission of coherent or incoherent light and can either be electronically addressed through a microcomputer or optically addressed with a TV camera. The transmission characteristics of the device have been measured, its diffraction pattern is examined, and its use as an input device for an optical correlator is tested. It is discovered that, with proper modifications, it has potential for optical-data-processing applications.

Liu, H.-K.↗
NASA NTRS1993

HiRES - High Resolution Extreme Ultraviolet Spectroheliometer toroidal diffraction grating performance evaluation

The ray-tracing results presented characterize the theoretically achievable EUV performance of the HiRES instrument. The effects of optical system misalignment on spectrograph images, and the laboratory results for two f/15 toroidal diffraction gratings that employ a multianode microchannel array, are also presented. Interferometric studies of toroidal figure accuracy, as well as optical and electron microscopy investigations of surface quality, are discussed. While the current toroidal gratings are noted to furnish good imaging across a wide wavelength range, they exhibit excessive EUV scatter, as well as spectral ghosting.

Berger, Thomas E.↗
NASA NTRS2001

Stitching-error reduction in gratings by shot-shifted electron-beam lithography

Calculations of the grating spatial-frequency spectrum and the filtering properties of multiple-pass electron-beam writing demonstrate a tradeoff between stitching-error suppression and minimum pitch separation. High-resolution measurements of optical-diffraction patterns show a 25-dB reduction in stitching-error side modes.

Integrated optics semiconductor lasersgratings↗
NASA NTRS1982

Spheres of the metallic glass Au55 Pb22.5 Sb22.5 and their surface characteristics

Spheres of the metallic glass Au55 Pb22.5 Sb22.5 have been formed up to a size of approximately 1.5 mm in diameter. X-ray diffraction was used to establish the glassy nature of the samples and to provide evidence of two phase-separated glass regions. Scanning electron microscopy provided a direct visual observation of the two-phase amorphous network on the surface of the sphere. The physical dimensions of the phase-separated regions were observed to be cooling-rate sensitive. Energy dispersive spectroscopy indicated that the compositions of these two glassy phases were Au-rich and Pb-rich, respectively, confirming the results of Kim and Johnson (1981). In addition, the spheres exhibited an unusual surface smoothness of better than + or - 250 A

Lee, M. C.↗
NASA NTRS1989

Rapid solidification of high-conductivity copper alloys

The main objective was to develop improved copper alloys of high strength and high thermal and electric conductivity. Chill block melt spinning was used to produce binary alloys of Cu-Cr and Cu-Zr, and ternary alloys of Cu-Cr-Ag. By quenching from the liquid state, up to 5 atomic percent of Cr and Zr were retained in metastable extended solid solution during the rapid solidification process. Eutectic solidification was avoided and the full strengthening benefits of the large volume fraction of precipitates were realized by subsequent aging treatment. The very low solid solubility of Cr and Zr in Cu result in a high conductivity Cu matrix strengthened by second phase precipitates. Tensile properties on as-cast and aged ribbons were measured at room and elevated temperatures. Precipitate coarsening of Cr in Cu was studied by changes in electrical resistance during aging. X-ray diffraction was used to measure the lattice parameter and the degree of supersaturation of the matrix. The microstructures were characterized by optical and electron microscopy.

Bloom, Theodore Atlas↗
NASA NTRS1992

Study of optical techniques for the Ames unitary wind tunnels. Part 1: Schlieren

Alignment procedures and conceptual designs for the rapid alignment of the Ames Unitary Wind Tunnel schlieren systems were devised. The schlieren systems can be aligned by translating the light source, the mirrors, and the knife edge equal distances. One design for rapid alignment consists of a manual pin locking scheme. The other is a motorized electronic position scheme. A study of two optical concepts which can be used with the schlieren system was made. These are the 'point diffraction interferometers' and the 'focus schlieren'. Effects of vibrations were studied.

Lee, George↗
NASA NTRS1990

Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

Advanced oxide thermal barrier coatings have been developed by incorporating multi- component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma- sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia-yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging fiom 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

Zhu, Dongming↗
NASA NTRS2013

Enhanced TiO2 Photocatalytic Processing of Organic Wastes for Green Space Exploration

The effect of transition metal co-catalysts on the photocatalytic properties of TiO2 was investigated. Ruthenium (Ru), palladium, platinum, copper, silver, and gold, were loaded onto TiO2 powders (anatase and mixed-phase P25) and screened for the decomposition of rhodamine B (RhB) under broad-band irradiation. The morphology and estimated chemical composition of photocatalysts were determined by scanning electron microscopy and energy dispersive spectroscopy, respectively. Brunhauer, Emmett and Teller (BET) analysis measured mass-specific surface area(s). X-ray diffraction analysis was performed to confirm the identity of titania phase(s) present. The BET surface area of anatase TiO2/Ru 1% (9.2 sq m/gm) was one of the highest measured of all photocatalysts prepared in our laboratory. Photolyses conducted under air-saturated and nitrogen-saturated conditions revealed photodegradation efficiencies of 85 and 2 percent, respectively, after 60 min compared to 58 percent with no catalyst. The cause of low photocatalytic activity under an inert atmosphere is discussed. TiO2/Ru 1% showed a superior photocatalytic activity relative to P25-TiO2 under broad-band irradiation. A potential deployment of photocatalytic technologies on a mission could be a reactor with modest enhancement in solar intensity brought about by a trough-style reactor, with reactants and catalyst flowing along the axis of the trough and therefore being illuminated for a controlled duration based on the flow rate.

Udom, I.↗
NASA NTRS2019

Arcus: The Soft X-ray Grating Explorer

Arcus provides high-resolution soft X-ray spectroscopy in the 12-50 Å bandpass with unprecedented sensitivity, including spectral resolution > 2500 and effective area > 250 cm2. The three top science goals for Arcus are (1) to measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, (2) to trace the propagation of outflowing mass, energy, and momentum from the vicinity of the black hole to extragalactic scales as a measure of their feedback, and (3) to explore how stars form and evolve. Arcus uses the same 12 m focal length grazing-incidence Silicon Pore X-ray Optics (SPOs) that ESA has developed for the Athena mission; the focal length is achieved on orbit via an extendable optical bench. The focused X-rays from these optics are diffracted by high-efficiency Critical-Angle Transmission (CAT) gratings, and the results are imaged with flight-proven CCD detectors and electronics. Combined with the high-heritage NGIS LEOStar-2 spacecraft and launched into 4:1 lunar resonant orbit, Arcus provides high sensitivity and high efficiency observing of a wide range of astrophysical sources.

Randall K Smith↗
NASA NTRS1976

Computer synthesis of high resolution electron micrographs

Specimen damage, spherical aberration, low contrast and noisy sensors combine to prevent direct atomic viewing in a conventional electron microscope. The paper describes two methods for obtaining ultra-high resolution in biological specimens under the electron microscope. The first method assumes the physical limits of the electron objective lens and uses a series of dark field images of biological crystals to obtain direct information on the phases of the Fourier diffraction maxima; this information is used in an appropriate computer to synthesize a large aperture lens for a 1-A resolution. The second method assumes there is sufficient amplitude scatter from images recorded in focus which can be utilized with a sensitive densitometer and computer contrast stretching to yield fine structure image details. Cancer virus characterization is discussed as an illustrative example. Numerous photographs supplement the text.

Nathan, R.↗
NASA NTRS1995

Computer Analysis of Electromagnetic Field Exposure Hazard for Space Station Astronauts during Extravehicular Activity

In order to estimate the RF radiation hazards to astronauts and electronics equipment due to various Space Station transmitters, the electric fields around the various Space Station antennas are computed using the rigorous Computational Electromagnetics (CEM) techniques. The Method of Moments (MoM) was applied to the UHF and S-band low gain antennas. The Aperture Integration (AI) method and the Geometrical Theory of Diffraction (GTD) method were used to compute the electric field intensities for the S- and Ku-band high gain antennas. As a result of this study, The regions in which the electric fields exceed the specified exposure levels for the Extravehicular Mobility Unit (EMU) electronics equipment and Extravehicular Activity (EVA) astronaut are identified for various Space Station transmitters.

Hwu, Shian U.↗
NASA NTRS1977

Wear studies on aircraft brake materials

An investigation of both worn surfaces of friction pads and steel rotors which are being applied in current aircraft brakes has been carried out by employing an X-ray diffraction technique. It consists of the analysis of chemical element distribution in the surface layers. The wear particles were also examined by using the scanning electron microscope. The initiation and growth of surface cracks and the oxidation were emphasized in this investigation. A wear model was proposed for the current aircraft brake materials. Essentially this model proposed that cracks are formed in the surface layer of the brake material due to the normal and frictional stresses. It is primarily surface temperature dependent.

Ho, T. L.↗
NASA NTRS1990

Phillips CO-oxidation catalyts for long-lived CO2 lasers: Activity and initial characterization studies

Four different catalysts have been developed specifically for use in sealed carbon dioxide lasers. The catalysts have been designed to be low dusting, stable to shock and vibration, have high activity at low temperatures and have long active lifetimes. Measured global CO oxidation rates range from 1.4 to 2.2 cc CO converted per minute per gram of catalyst at ambient temperature. The catalysts also retain substantial activity at temperatures as low as -35 C. The Phillips laser catalysts are prepared in a variety of different shapes to meet the different pressure drop and gas flow profiles present in the many different styles of lasers. Each catalyst has been tested in sealed TEA lasers and has been shown to substantially increase the sealed life of the laser. Activity measurements made on the precious metal catalysts which were prepared with and without activity promoters showed that the promoter materials increase catalyst CO oxidation activity at least an order of magnitude at ambient temperature. Initial studies using H2 and CO chemisorption, X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS) have shown that the activity promoters do not significantly affect the precious metal crystallite size or the electronic structure around the precious metal. In addition, the formation or lack of formation of solid solutions between the precious metal and promoters has also been shown not to affect the activity of the promoted catalyst.

Kolts, J. H.↗
NASA NTRS1991

Protein crystal growth in microgravity

A series of protein-crystal growth experiments were performed on Space Shuttle flight STS-26 in September 1988 and STS-29 in March 1989. These proteins had been studied extensively in crystal-growth experiments on earth prior to the microgravity experiments. For those proteins which produced crystals of adequate size, 3D intensity data sets with electronic area detector systems were collected. Comparisons show that the microgravity-grown crystals of these proteins are larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions. Analyses of the 3D data sets indicate that the space-grown crystals are more highly ordered at the molecular level than their earth-grown counterparts.

Snyder, Robert↗
NASA NTRS1972

Electron petrography of Apollo sample 14310.

Thin sections prepared from Apollo sample 14310 have been examined with 100-kV transmission electron microscopy. The sample is composed principally of anorthite and pyroxene. The anorthites fall into two categories. The transitional anorthites that show the characteristic 'c' type diffraction maxima are characterized by very fine antiphase domain structures and some fine twinning. The body-centered anorthites that show no 'c' reflections are characterized by an absence of fine twinning and a less well-defined antiphase domain structure. Although both orthopyroxene and clinopyroxenes are reported in sample 14310, only clinopyroxenes were observed in this study and all show exsolution structures. The augite exsolved in pigeonite commonly is along lamellae parallel to (100), although (001) lamellae are also present. This unusual orientation was verified by diffraction patterns. The pigeonite commonly shows antiphase domains, attributed to stacking errors when the sample inverted from its high-temperature disordered form. In augite as the host phase, the pigeonite lamellae contain very complex structures including antiphase domains.

Smith, D. K.↗
NASA NTRS1979

Viking radio occultation measurements of the atmosphere and topography of Mars - Data acquired during 1 Martian year of tracking

The results of one Martian year of radio occultation measurements of the atmosphere and topography of Mars obtained using the Viking Orbiters are briefly summarized. Determinations of the vertical distribution of tropospheric gas refractivity and ionospheric electron density obtained from atmospheric Doppler frequency perturbations of the S and X band radio tracking frequencies indicate large meteorological variations, with near-surface temperatures ranging from 150 to 250 K, 5-km atmospheric pressure ranging from 3.5 to 4.8 mbar, inversion layers over the polar caps and dust storms, and seasonal pressure variations. Double- and single-layered upper atmospheric electron density profiles were observed on the sunlit and dark sides of the planet, respectively. A topographic map of the Martian surface, obtained from the limb diffraction effects observed at ingress and egress, is found to agree well with the elevation contours of US Geological survey map M 25M 3 RMC, with the exception of the south polar and Alba Patera regions.

Lindal, G. F.↗
NASA NTRS1973

Remote analysis of planetary soils: X-ray diffractometer development

A system is described suitable for remote low power mineralogical analysis of lunar, planetary, or asteroid soils. It includes an X-ray diffractometer, fluorescence spectrometer, and sample preparation system. A one Curie Fe-55 source provides a monochromatic X-ray beam of 5.9 keV. Seeman-Bohlin or focusing geometry is employed in the camera, allowing peak detection to proceed simultaneously at all angles and obviating the need for moving parts. The detector system is an array of 500-600 proportional counters with a wire-spacing of 1 mm. An electronics unit comprising preamplifier, postamplifier, window discriminators, and storage flipflops requiring only 3.5 milliwatts was designed and tested. Total instrument power is less than 5 watts. Powder diffraction patterns using a flat breadboard multiwire counter were recorded.

Gregory, J. C.↗
NASA NTRS1973

A laboratory simulation of a single-axis dual-level precision pointing system

The laboratory simulation of a scaled single-axis dual-level control system for a large space telescope is demonstrated. The dual-level control system consists of a coarse-body-pointing system and a fine-pointing system, which uses an image motion compensator, an image dissector tube, and digital electronics. The results of the simulation indicate that the dual-level system can be used to provide tracking capability within one-tenth of a diffraction-limited image diameter of a 3-meter f/100 telescope for stars up to a +12.3 visual magnitude.

Bullock, G. F.↗