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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Scattering properties of woven fibrous insulations - Effects of interference for normal incidence

This paper examines the scattering properties of woven fibrous materials in order to model the interactions between the scattered radiation from individual fibers. A normally incident plane electromagnetic wave is considered and different representative geometries are analyzed theoretically. Experimental results are presented for specific woven thermal insulation fabrics. Previous studies in the literature have mostly ignored the effect of constructive or destructive addition of scattered waves from individual fibers with the exception of the case of parallel fibers. Whereas the light-scattering characteristics of a single long fiber depend only on the size parameter and on the material optical constants, the additional mechanism of interference between the scattered waves from fibers of parallel or perpendicular orientation introduces an additional dependence on fiber locations. In this study, analytical models are developed for obtaining the radiative scattering characteristics of woven fibrous media taking into account the mechanism of interference. Experimental measurements of forward- and backward-scattered light from a woven silica cloth over a broad range of wavelengths in the infrared are obtained and compared with the predicted results for a system of two orthogonal families of infinite parallel fibers.

Kumar, Sunil↗
NASA NTRS1990

In situ measurements of scattering from contaminated optics in the Vacuum Ultraviolet

NASA's In Situ Contamination Effects Facility has been used to measure the time dependence of the angular reflectance from molecularly contaminated optical surfaces in the vacuum ultraviolet. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using noncoherent VUV sources with the predominant wavelengths being the krypton resonance lines at 1236 and 1600 angstroms. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (bidirectional reflectance distribution function) experiment is described and details of the on-going program to characterize optical materials exposed to the space environment is reported.

Herren, Kenneth A.↗
NASA NTRS1990

The Japanese containerless experiments

There are three sets of Japanese containerless experiments. The first is Drop dynamics research. It consists of acoustic levitation and large amplitude drop oscillation. The second is Optical materials processing in an acoustic levitation furnace. And the third is Electrostatic levitator development by two different Japanese companies.

Azuma, Hisao↗
NASA NTRS1991

Meteoroid/space debris impacts on MSFC LDEF experiments

The numerous meteoroid and space debris impacts found on AO171, AO034, S0069, and other MSFC experiments are examined. Besides those impacts found by the Meteoroid and Debris Special Investigative Group at KSC, numerous impacts of less than 0.5 mm were found and photographed. The flux and size distribution of impacts are presented as well as EDS analysis of impact residue. Emphasis is on morphology of impacts in the various materials, including graphite/epoxy composites, polymeric materials, optical coatings, thin films, and solar cells.

Finckenor, Miria↗
NASA NTRS1991

Nonlinear optical effects on the surface of acridine yellow-doped lead-tin fluorophosphate glass

The second- and third-order nonlinear optical properties of acridine yellow-doped lead-tin fluorophosphate (LTF) glass have been directly studied by measurement of surface enhanced second harmonic generation and third harmonic generation. The three photon excitation fluorescence is also observed. Based on these results, the large nonlinearities of the acridine LTF system which is a new nonlinear optical material are experimentally demonstrated.

He, K. X.↗
NASA NTRS1992

Acousto-Optical Imaging Spectropolarimeter

Imaging spectropolarimeter designed around acousto-optical tunable filter (AOTF) takes polarization-specific spectral images of solid surfaces, aerosols, and absorption and emission phenomena in gas phase, at wavelengths from 500 to 1,000 nm. Produces side-by-side spectral images in two mutually perpendicular polarizations, one corresponding to ordinary, other corresponding to extraordinary waves in acousto-optical material. Offers large aperture, high resolving power, and rapid tunability, with no moving parts.

Saif, Babak↗
NASA NTRS1990

Contamination study

The time dependence of the angular reflectance from molecularly contaminated optical surfaces in the Vacuum Ultraviolet (VUV) is measured. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using non-coherent VUV sources with the predominant wavelengths being the Krypton resonance lines at 1236 and 1600 A. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (Bidirectional Reflectance Distribution Functions) experiment is described and details of the ongoing program to characterize optical materials exposed to the space environment is reported.

Johnson, R. Barry↗
NASA NTRS1990

Ionizing radiation exposure of LDEF

The Long Duration Exposure Facility (LDEF) was launched into orbit by the Space Shuttle 'Challenger' mission 41C on 6 April 1984 and was deployed on 8 April 1984. The original altitude of the circular orbit was 258.5 nautical miles (479 km) with the orbital inclination being 28.5 degrees. The 21,500 lb NASA Langley Research Center satellite, having dimensions of some 30x14 ft was one of the largest payloads ever deployed by the Space Shuttle. LDEF carried 57 major experiments and remained in orbit five years and nine months (completing 32,422 orbits). It was retrieved by the Shuttle 'Columbia' on January 11, 1990. By that time, the LDEF orbit had decayed to the altitude of 175 nm (324 km). The experiments were mounted around the periphery of the LDEF on 86 trays and involved the representation of more than 200 investigators, 33 private companies, 21 universities, seven NASA centers, nine Department of Defense laboratories and eight foreign countries. The experiments covered a wide range of disciplines including basic science, electronics, optics, materials, structures, power and propulsion. The data contained in the LDEF mission represents an invaluable asset and one which is not likely to be duplicated in the foreseeable future. The data and the subsequent knowledge which will evolve from the analysis of the LDEF experiments will have a very important bearing on the design and construction of the Space Station Freedom and indeed on other long-term, near-earth orbital space missions. A list of the LDEF experiments according to experiment category and sponsor is given, as well as a list of experiments containing radiation detectors on LDEF including the LDEF experiment number, the title of the experiment, the principal investigator, and the type of radiation detectors carried by the specific experiment.

Benton, E. V.↗
NASA NTRS1992

Meteoroid/space debris impacts on MSFC LDEF experiments

The many meteoroid and space debris impacts found on A0171, A0034, S1005, and other MSFC experiments are considered. In addition to those impacts found by the meteoroid and debris studies, numerous impacts less than 0.5 mm were found and photographed. The flux and size distribution of impacts is presented as well as EDS analysis of impact residue. Emphasis is on morphology of impacts in the various materials, including graphite/epoxy composites, polymeric materials, optical coatings, thin films, and solar cells.

Finckenor, Miria↗
NASA NTRS1993

Synthesizing Diacetylenes With Nonlinear Optical Properties

Diacetylene compounds being investigated to determine whether they have nonlinear optical properties making them useful for four-wave mixing, generation of third harmonics, phase conjugation, and like. Diacetylene monomers synthesized by sequences of chemical reactions. Monomers polymerized by ultraviolet light, forming potentially useful nonlinear optical materials.

Mcmanus, Samuel P.↗
NASA NTRS1993

The dependence on morphology of the gas content in galactic disks

The classification S0 was introduced by Hubble to serve as a description of galaxies whose morphological characteristics seemed to lie between the disk-dominated spirals and the spheroidal elliptical systems. Since then there has been extensive discussion as to whether this classification sequence is also an evolutionary sequence. Many studies have focussed on a particular feature such as the luminosity profile, the bulge-to-disk ratio, or the nature of the interstellar matter, but the question of the evolution remains contentious. Equally contentious is the question of the classification itself. For systems with well-developed disks there usually is no problem. Many spheroidal systems also are unambiguously classified as ellipticals in most catalogs. However, there are a number of early systems which have been reclassified following review using improved optical material. For example, Eder et al. (AJ, 102, 572, 1991) found that many of the S0 galaxies which are rich in neutral hydrogen have faint spiral features. The confusion about classification propagates into the discussion of the properties of early-type systems. Attempts to put the classification system on a quantitative basis have in general been unsuccessful. Recently Sandage (private communication) has reviewed the classification of early systems and has defined a set of sub-classes for these objects. The S0 galaxies are divided into three groups, depending on the prominence of the disk. There are six subdivisions of Sa galaxies, depending upon the relative prominence of knots and other arm-like characteristics. We have explored the total gas content in these objects to see if there is a dependence on the galaxy morphology, as denoted by these new subclasses.

Hogg, D. E.↗
NASA NTRS1991

Ground based experiments on the growth and characterization of L-Arginine Phosphate (LAP) crystals

L-Arginine Phosphate (LAP) is a new nonlinear optical material with higher efficiency for harmonic generation compared to KDP. Crystals of LAP were grown in the laboratory from supersaturated solutions by temperature lowering technique. Investigations revealed the presence of large dislocation densities inside the crystals which are observed to produce refractive index changes causing damage at high laser powers. This is a result of the convection during crystal growth from supersaturated solutions. It is proposed to grow these crystals in a diffusion controlled growth condition under microgravity environment and compare the crystals grown in space with those grown on ground. Physical properties of the solutions needed for modelling of crystal growth are also presented.

Rao, S. M.↗
NASA NTRS1991

Telescope optical systems program overview

Telescope Optical Systems is a new focused program of technology development that will shape and enable the new 'telescope' missions being studied and planned by NASA. The program structure contains six major elements: systems, optics, materials, structures, controls, and integration and test. Activities in each element will address key technology issues that support a wide range of user needs. Program goals, technology needs, and technology performance objectives are summarized in outline form.

Hirschbein, Murray S.↗
NASA NTRS1990

LDEF Update

This video explores the research being done on the Long Duration Exposure Facility (LDEF), a satellite carrying 57 experiments designed to study the effects of the space environment, which had been in orbit for almost 6 years, and was retrieved and brought back to Earth by the Space Shuttle astronauts. The video shows scenes of the retrieval of LDEF, as well as scenes of ongoing research into the data returned with the satellite from experiments on external coating, contamination of optical materials by thermal control paint, the effects of cosmic rays on different materials, and the effect of the space environment on 12 million tomato seeds that have since been planted.

Source record↗
NASA NTRS1994

Electronic access to ONREUR/ONRAISIA S and T reports

The Office of Naval Research maintains two foreign field offices in London, England and in Tokyo, Japan. These offices survey world-wide findings, trends and achievements in science and technology. These offices maintain liaison between U.S. Navy and foreign scientific research and development organizations conducting programs of naval interest. Expert personnel survey foreign scientific and technical activities, identify new directions and progress of potential interest, and report their findings. Report topics cover a broad range of basic scientific thrusts in mathematics, physics, chemistry, computer science, and oceanography, as well as advances in technologies such as electronics, materials, optics, and robotics. These unclassified reports will be made available via the Internet in 1995, replacing hard-copy publication.

Mccluskey, William↗
NASA NTRS1995

Analysis of systems hardware flown on LDEF: New findings and comparison to other retrieved spacecraft hardware

The Long Duration Exposure Facility (LDEF) was retrieved in 1990 after spending 69 months in low-earth-orbit (LEO). A wide variety of mechanical, electrical, thermal, and optical systems, subsystems, and components were flown on LDEF. The Systems Special Investigation Group (Systems SIG) was formed by NASA to investigate the effects of the 69 month exposure on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. This report is the Systems SIG final report which updates earlier findings and compares LDEF systems findings to results from other retrieved spacecraft hardware such as Hubble Space Telescope. Also included are sections titled (1) Effects of Long Duration Space Exposure on Optical Scatter, (2) Contamination Survey of LDEF, and (3) Degradation of Optical Materials in Space.

Dursch, Harry↗
NASA NTRS1990

Applying CLIPS to control of molecular beam epitaxy processing

A key element of U.S. industrial competitiveness in the 1990's will be the exploitation of advanced technologies which involve low-volume, high-profit manufacturing. The demands of such manufacture limit participation to a few major entities in the U.S. and elsewhere, and offset the lower manufacturing costs of other countries which have, for example, captured much of the consumer electronics market. One such technology is thin-film epitaxy, a technology which encompasses several techniques such as Molecular Beam Epitaxy (MBE), Chemical Beam Epitaxy (CBE), and Vapor-Phase Epitaxy (VPE). Molecular Beam Epitaxy (MBE) is a technology for creating a variety of electronic and electro-optical materials. Compared to standard microelectronic production techniques (including gaseous diffusion, ion implantation, and chemical vapor deposition), MBE is much more exact, though much slower. Although newer than the standard technologies, MBE is the technology of choice for fabrication of ultraprecise materials for cutting-edge microelectronic devices and for research into the properties of new materials.

Rabeau, Arthur A.↗
NASA NTRS1996

Diffusion, Viscosity and Crystal Growth in Microgravity

The diffusivity of TriGlycine Sulfate (TGS), Potassium Dihydrogen Phosphate (KDP), Ammonium Dihydrogen Phosphate (ADF) and other compounds of interest to microgravity crystal growth, in supersaturated solutions as a function of solution concentration, 'age' and 'history was studied experimentally. The factors that affect the growth of crystals from water solutions in microgravity have been examined. Three non-linear optical materials have been studied, potassium dihydrogen phosphate (KDP), ammonium dihydrogen phosphate (ADP) and triglycine sulfate (TGC). The diffusion coefficient and viscosity of supersaturated water solutions were measured. Also theoretical model of diffusivity and viscosity in a metastable state, model of crystal growth from solution including non-linear time dependent diffusivity and viscosity effect and computer simulation of the crystal growth process which allows simulation of the microgravity crystal growth were developed.

Myerson, Allan S.↗