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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Anti-gravity device

An educational toy useful in demonstrating fundamental concepts regarding the laws of gravity is described. The device comprises a sphere 10 of radius r resting on top of sphere 12 of radius R. The center of gravity of sphere 10 is displaced from its geometrical center by distance D. The dimensions are so related that D((R+r)/r) is greater than r. With the center of gravity of sphere 10 lying on a vertical line, the device is in equilibrium. When sphere 10 is rolled on the surface of sphere 12 it will return to its equilibrium position upon release. This creates an illusion that sphere 10 is defying the laws of gravity. In reality, due to the above noted relationship of D, R, and r, the center of gravity of sphere 10 rises from its equilibrium position as it rolls a short distance up or down the surface of sphere 12.

Palsingh, S.↗
NASA NTRS2010

Satellite (Timed, Aura, Aqua) and In Situ (Meteorological Rockets, Balloons) Measurement Comparability

Measurements using the inflatable falling sphere often are requested to provide density data in support of special sounding rocket launchings into the mesosphere and thermosphere. To insure density measurements within narrow time frames and close in space, the inflatable falling sphere is launched within minutes of the major test. Sphere measurements are reliable for the most part, however, availability of these rocket systems has become more difficult and, in fact, these instruments no longer are manufactured resulting in a reduction of the meager stockpile of instruments. Sphere measurements also are used to validate remotely measured temperatures and have the advantage of measuring small-scale atmospheric features. Even so, with the dearth of remaining falling spheres perhaps it is time to consider whether the remote measurements are mature enough to stand alone. Presented are two field studies, one in 2003 from Northern Sweden and one in 2010 from the vicinity of Kwajalein Atoll that compare temperature retrievals between satellite and in situ failing spheres. The major satellite instruments employed are SABER, MLS, and AIRS. The comparisons indicate that remotely measured temperatures mimic the sphere temperature measurements quite well. The data also confirm that satellite retrievals, while not always at the exact location required for individual studies, are adaptable enough and highly useful. Although the falling sphere will provide a measurement at a specific location and time, satellites only pass a given location daily or less often. This report reveals that averaged satellite measurements can provide temperatures and densities comparable to the falling sphere.

Schmidlin, F. J.↗
NASA NTRS1972

Development and fabrication of insulator seals for thermionic diodes

Eight different types of cermet seals for thermionic diodes were investigated: (1) 1 micron Al2O3 with Nb spheres; (2) 200 A Al2O3 with Nb spheres; (3) 1 micron Al2O3 with Nb 1% Zr spheres; (4) 200 A Al2O3 with Nb 1% Zr spheres; (5) Pure Y2O3 with Nb 1% Zr spheres; (6) Y2O3 3% ZrO2 with Nb 1% Zr spheres; (7) Y2O3 10% ZrO2 with Nb 1% Zr spheres; and (8) ZrO2 12% Y2O3 with Nb 1% Zr spheres. Investigations were made to determine the most favorable fabrication techniques and the effect of the bonding cycle, (length of bonding time and shutdown sequences). The analysis of the seals included tensile test, vacuum test, electrical test and metallurgical examination. At the conclusion of the development phase, 36 seals were fabricated for delivery for evaluation.

Poirier, V. L.↗
NASA NTRS1994

Temporal study of the current collected by a Langmuir probe biased to high voltages in the wake behind a conducting body

The temporal evolution of the voltage-current characteristic of a spherical Langmuir probe in the near-wake region of a conducting body is investigated in a pulsed plasma device. Measurements of the current collected by a sphere placed on axis behind a conducting disk are presented as a function of the bias voltage and time. The bias voltage on the collecting sphere is large enough, ranging from +500 to -3000 V, to attract ions or electrons across the wake region. In addition, plasma potential profiles as a function of sphere bias voltage and time throughout the nearwake and midwake region are presented. It is found that for a negative sphere bias a threshold voltage exists for current collection. This threshold voltage decreases during the formation of the wake behind the conducting disk. Potential measurements indicate that the sheath region around the negatively biased sphere contracts as the wake region establishes itself. This contraction of the sheath region increases the electric field attracting ions to the sphere and decreases the threshold voltage for current collection. For positive sphere bias voltage the current collected by the sphere does not exhibit a threshold voltage but is monotonically increasing.

Meassick, S.↗
NASA NTRS1999

Radiometric Measurement Comparisons Using Transfer Radiometers in Support of the Calibration of NASA's Earth Observing System (EOS) Sensors

EOS satellite instruments operating in the visible through the shortwave infrared wavelength regions (from 0.4 micrometers to 2.5 micrometers) are calibrated prior to flight for radiance response using integrating spheres at a number of instrument builder facilities. The traceability of the radiance produced by these spheres with respect to international standards is the responsibility of the instrument builder, and different calibration techniques are employed by those builders. The National Aeronautics and Space Administration's (NASA's) Earth Observing System (EOS) Project Science Office, realizing the importance of preflight calibration and cross-calibration, has sponsored a number of radiometric measurement comparisons, the main purpose of which is to validate the radiometric scale assigned to the integrating spheres by the instrument builders. This paper describes the radiometric measurement comparisons, the use of stable transfer radiometers to perform the measurements, and the measurement approaches and protocols used to validate integrating sphere radiances. Stable transfer radiometers from the National Institute of Standards and Technology, the University of Arizona Optical Sciences Center Remote Sensing Group, NASA's Goddard Space Flight Center, and the National Research Laboratory of Metrology in Japan, have participated in these comparisons. The approaches used in the comparisons include the measurement of multiple integrating sphere lamp levels, repeat measurements of select lamp levels, the use of the stable radiometers as external sphere monitors, and the rapid reporting of measurement results. Results from several comparisons are presented. The absolute radiometric calibration standard uncertainties required by the EOS satellite instruments are typically in the +/- 3% to +/- 5% range. Preliminary results reported during eleven radiometric measurement comparisons held between February 1995 and May 1998 have shown the radiance of integrating spheres agreed to within +/- 2.5% from the average at blue wavelengths and to within +/- 1.7% from the average at red and near infrared wavelengths. This level of agreement lends confidence in the use of the transfer radiometers in validating the radiance scales assigned by EOS instrument calibration facilities to their integrating sphere sources.

Butler, James J.↗
NASA NTRS2009

Synchronized Position Hold, Engage, Reorient, Experimental Satellites

Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) are bowling-ball sized spherical satellites. They will be used inside the space station to test a set of well-defined instructions for spacecraft performing autonomous rendezvous and docking maneuvers. Three free-flying spheres will fly within the cabin of the station, performing flight formations. Each satellite is self-contained with power, propulsion, computers and navigation equipment. The results are important for satellite servicing, vehicle assembly and formation flying spacecraft configurations. SPHERES is a testbed for formation flying by satellites, the theories and calculations that coordinate the motion of multiple bodies maneuvering in microgravity. To achieve this inside the ISS cabin, bowling-ball-sized spheres perform various maneuvers (or protocols), with one to three spheres operating simultaneously . The Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) experiment will test relative attitude control and station-keeping between satellites, re-targeting and image plane filling maneuvers, collision avoidance and fuel balancing algorithms, and an array of geometry estimators used in various missions. SPHERES consists of three self-contained satellites, which are 18 sided polyhedrons that are 0.2 meter in diameter and weigh 3.5 kilograms. Each satellite contains an internal propulsion system, power, avionics, software, communications, and metrology subsystems. The propulsion system uses CO2, which is expelled through the thrusters. SPHERES satellites are powered by AA batteries. The metrology subsystem provides real-time position and attitude information. To simulate ground station-keeping, a laptop will be used to transmit navigational data and formation flying algorithms. Once these data are uploaded, the satellites will perform autonomously and hold the formation until a new command is given.

Miller, David W.↗
NASA NTRS2012

Comparison of Temperature Measurements in the Middle Atmosphere by Satellite with Profiles Obtained by Meteorological Rockets

Measurements using the inflatable falling sphere technique have occasionally been used to obtain temperature results from density data and thereby provide comparison with temperature profiles obtained by satellite sounders in the mesosphere and stratosphere. To insure density measurements within narrow time frames and close in space, the inflatable falling sphere is launched within seconds of the nearly overhead satellite pass. Sphere measurements can be used to validate remotely measured temperatures but also have the advantage of measuring small-scale atmospheric features. Even so, with the dearth of remaining falling spheres available (the manufacture of these systems has been discontinued), it may be time to consider whether the remote measurements are mature enough to stand alone. Three field studies are considered, one in 2003 from Northern Sweden, and two in 2010 from the vicinity of Kwajalein Atoll in the South Pacific and from Barking Sands, Hawaii. All three sites are used to compare temperature retrievals between satellite and in situ falling spheres. The major satellite instruments employed are SABER, MLS, and AIRS. The comparisons indicate that remotely measured temperatures mimic the sphere temperature measurements quite well. The data also confirm that satellite retrievals, while not always at the exact location required for detailed studies in space and time, compare sufficiently well to be highly useful. Although the falling sphere will provide a measurement at a specific location and time, satellites only pass a given location daily or less frequently. This report reveals that averaged satellite measurements can provide temperatures and densities comparable to those obtained from the falling sphere, thereby providing a reliable measure of global temperature

Goldberg, Richard A.↗
NASA NTRS1993

Growth of Si spherical crystals and the surface oxidation (M-9)

Nearly 90 percent of semiconductor devices are produced with Si single crystals as the starting materials. For instance, the integrated circuits (IC), which are used in almost all electronic equipments such as TV, tape recorders, audio amplifiers, etc., are made after various processings of Si single crystal wafers. In these wafers, the same controlled amounts of impurities are added and the uniformities in their distributions are extremely important. Growth under microgravity makes it possible to eliminate the buoyancy-driven convection in the melt, which is one of the main origins of convections which results in non-uniformity of the impurity. Another source of convection is known as Marangoni convection which is driven on the free surface when a temperature gradient occurs. One of the merits of microgravity experimentation is that the detailed study of this convection becomes possible. Another important advantage of microgravity is that growth of crystals without a crucible is possible. This makes it possible to study melt growth without the strain which is usually introduced on the ground. Nevertheless, we should repeat and analyze many growth experiments in space to get reliable results. However, since in the FMPT, the time for the experiment is limited, we plan to carry out two kinds of very simple and basic experiments as the first step for the semiconductor growth experiment. In the first experiment, we use single crystal Si sphere as the starting material and as shown, this sphere is heated in the furnace at a slightly higher temperature than the melting point. After the melting front moves nearly half way to its center, the temperature is decreased to stop the melting and to start the growth from the seed for which we use the unmelted solid party of the sphere. The sphere is centered by quartz protuberances inside of the quartz crucible. There exists the possibility of temperature fluctuations being introduced when the molten sphere occasionally touches the protuberances. The total time needed for the melting and the growth processes is estimated to be 30 minutes. Infrared emission from the sphere is monitored in order to prevent the accidental loss of the central solid core. The schematical illustration of the second experient is shown. A single crystal, Si rod is used as the starting material. In the first stage, the rod is melted from one end to obtain a liquid sphere. In the second stage, the single crystal is grown by decreasing the temperature from the unmelted part of the rod which is used as the seed. The second experient somewhat resembles the Czochralski method used on the ground; however, in the space experiment, no crucible is employed and the temperature uniformity is much superior. In both experiments, phosphorous is doped to allow observation of the change in the shape of the liquid solid interface during crystal growth and the impurity striations, if any.

Nishinaga, Tatau↗
NASA NTRS2000

Recognizing Leonid Meteoroids Among The Collected Startospheric Dust

Three chemical groups of primary "silicate" spheres <30 micron in diameter of cometary origin were collected in the lower stratosphere between 1981 May and 1994 July. The "silicate" sphere abundances represent an annual background from contributions by sporadic meteor and weak annual meteor shower activities. During two collection periods, from 06/22 until 08/18, 1983 (U2015), and from 09/15-12/15, 1981 (W7027/7029), a higher number of spheres was collected compared to other periods of the year represented by the other collectors studied here. This study links two different data sets, viz. the NASA/JSC Cosmic Dust Catalogs and peak activities of annual meteor showers, and identified high-velocity cometary sources for collected stratospheric "silicate" spheres. The majority of spheres on flag U2015 may originate from comet P/Swift-Tuttle (Perseids), while the majority of spheres on flags W7027/7029 could be from comet P/Halley (Orionids) or comet P/Tempel-Tuttle (Leonids). Variations in relative proportions of the Mg,Si,Ca +/- Al, Mg,Si +/- Fe and Al,Si,Ca spheres may offer a hint of chemical differences among high-velocity comets. Proof for the findings reported here might be obtained by targeted cosmic dust collections in the lower stratosphere including periods of meteor shower and storm activity.

Rietmeijer, Frans J. M.↗
NASA NTRS2005

Multipurpose Fiber Injected-micro-spherical LIDAR System

A technological revolution is occurring in the field of fiber lasers. Over the past two years, the level of power has increased from approx. 100 watts to nearly 1 kilowatt. We are developing a novel fiber laser system, which is a satellite-based LIDAR transmitter of multi-lines. The system is made of a hollow fiber filled with micro-spheres doped with lasing materials. Each sphere has its inherent optical cavity, which makes the system a cavity free and in the same time, emits multi-laser lines for simultaneous multi-task operations. The system is also rugged, compact, lightweight, and durable. Our earlier studies on micro-spheres doped with different laser dyes demonstrated the emission of extremely fine laser lines of less than 3 A line-width, which are of interest for spectroscopic applications, sensing, imaging, and optical communications. Individual dye-doped micro-spheres demonstrated a lasing resonance peaks phenomenon in their fluorescence spectra of linear and nonlinear features that do not exist in the bulk dye solutions. Each individual micro-sphere acts as a laser system with inherent cavity, where the fluorescence line suffers multiple internal reflections within the micro-sphere and gains enough energy to become a laser line. Such resonance peaks are dependent on the sphere's morphology, size, shape, and its refractive index. These resonance peaks are named structural resonance, whispering modes or whispering gallery modes, creeping waves, circumferential waves, surfaces modes, and virtual modes. All of these names refer to the same phenomenon of morphology dependent resonance (MDR), which has already been described and predicted precisely by electromagnetic theory and Lorentz-Mie theory since 1908. The resonance peaks become more obvious when the particle size approaches and exceeds the wavelength of the laser used and the relative index of the particle is greater than that of the surrounding medium. Additional information is included in the original extended abstract.

Abdelayem, Hossin↗
NASA NTRS1978

Silicate spherules from deep-sea sediments - Confirmation of extraterrestrial origin

Silicate spherules larger than 100 microns were extracted from 100 kg of box core samples of Pacific red clay taken in the mid-Pacific at a depth of 5 km, and the concentration of nonvolatile trace elements was determined for three spheres. One of the spheres shows excellent resemblance to C1 chondrite nonvolatile trace-element abundance patterns, and the relative abundances of the other two spheres are also very similar to those of C1 chondrites. One of these two spheres is depleted in Ir and Ru, while the other is depleted for Ni and Cr; possible explanations for the depletions are considered. Since the elemental abundances of the third sphere match the abundances of C1 chondrites, it is suggested that this sphere must be of extraterrestrial origin.

Ganapathy, R.↗
NASA NTRS1997

Crystalline Colloidal Arrays in Polymer Matrices

Crystalline Colloidal Arrays (CCA, also known as colloidal crystals), composed of aqueous or nonaqueous dispersions of self-assembled nanosized polymer colloidal spheres, are emerging toward the development of advanced optical devices for technological applications. The spontaneous self assembly of polymer spheres in a dielectric medium results from the electrostatic repulsive interaction between particles of uniform size and charge distribution. In a way similar to atomic crystals that diffract X-rays, CCA dispersions in thin quartz cells selectively and efficiently Bragg diffract the incident visible light. The reason for this diffraction is because the lattice (body or face centered cubic) spacing is on the order of the wavelength of visible light. Unlike the atomic crystals that diffract a fixed wavelength, colloidal crystals in principle, depending on the particle size, particle number and charge density, can diffract W, Vis or IR light. Therefore, the CCA dispersions can be used as laser filters. Besides, the diffraction intensity depends on the refractive index mismatch between polymer spheres and dielectric medium; therefore, it is possible to modulate incident light intensities by manipulating the index of either the spheres or the medium. Our interest in CCA is in the fabrication of all-optical devices such as optical switches, limiters, and spatial light modulators for optical signal processing. The two major requirements from a materials standpoint are the incorporation of suitable nonlinear optical materials (NLO) into polymer spheres which will allow us to alter the refractive index of the spheres by intense laser radiation, and preparation of solid CCA filters which can resist laser damage. The fabrication of solid composite filters not only has the advantage that the films are easier to handle, but also the arrays in solid films are more robust than in liquid media. In this paper, we report the photopolymerization process used to trap CCA in polymer matrices, the factors which affect the optical diffraction qualities of resulting polymer films, and methods to improve the efficiencies of solid optical filters. Before this, we also present the experimental demonstration, of controlling the optical diffraction intensities from aqueous CCA dispersions by varying the temperature, which establishes the feasibility of fabricating all-optical switching devices with nonlinear periodic array structures.

Sunkara, Hari B.↗
NASA NTRS2005

Surface Collisions Involving Particles and Moisture (SCIP'M)

Experiments were performed on the collision of a solid sphere with a nearly horizontal flat surface covered with a thin layer of viscous liquid. High-speed collisions were obtained by dropping the ball onto the surface from various heights, using gravitational acceleration. Low-speed collisions were obtained using pendulums with long strings or by launching the balls at low velocities in the reduced-gravity environment of parabolic flight. The sphere bounces only when the impact velocity exceeds a critical value. The coefficient of restitution (ratio of rebound velocity to impact velocity) increases with increasing impact velocity above the critical value, indicating the increasing relative importance of elastic deformation to viscous dissipation. The critical impact velocity increases, and the coefficient of restitution decreases, with increasing viscosity or thickness of the liquid layer and with decreasing density or size of the sphere. The ratio of the wet and dry coefficients is expressed as a function of the Stokes number (ratio of particle inertia and viscous forces), showing good agreement between theory and experiment. Similar experiments were performed with the flat surface inclined at various angles to the approaching sphere. A modified Stokes number, which is a measure of the ratio of inertia of the sphere in the normal direction to the viscous forces exerted by the fluid layer, was used for the analysis of oblique collisions. Even for these oblique collisions, it was found that no rebound of the ball was observed below a certain critical Stokes number. The coefficient of normal restitution, defined as a ratio of normal rebound velocity to normal approach velocity, was found to increase beyond the critical Stokes number and even out as it approaches the value for dry restitution at high Stokes numbers. It was also found that, for smooth spheres like steel, the normal restitution at the same modified Stokes number is independent of the angle of impact. The tangential coefficient of restitution, defined as the ratio of tangential rebound velocity to tangential approach velocity, is found to be nearly unity, except for very low approach velocities. Thus, as a first approximation, the theories that predict the coefficient of restitution for head-on wet collisions can be extended to predict the coefficient of normal restitution for oblique wet collisions. Additional experiments were performed with soft surfaces in which a porous cloth or sponge layer was placed over the hard, flat surface. In these experiments, the coefficient of restitution was found to decrease with increasing impact velocity, due to inelastic losses in the soft material. A model combining inelastic deformation and flow through porous media was developed to describe these findings.

Davis, Robert H.↗
NASA NTRS2002

Higher Order, Hybrid BEM/FEM Methods Applied to Antenna Modeling

In this presentation, the authors address topics relevant to higher order modeling using hybrid BEM/FEM formulations. The first of these is the limitation on convergence rates imposed by geometric modeling errors in the analysis of scattering by a dielectric sphere. The second topic is the application of an Incomplete LU Threshold (ILUT) preconditioner to solve the linear system resulting from the BEM/FEM formulation. The final tOpic is the application of the higher order BEM/FEM formulation to antenna modeling problems. The authors have previously presented work on the benefits of higher order modeling. To achieve these benefits, special attention is required in the integration of singular and near-singular terms arising in the surface integral equation. Several methods for handling these terms have been presented. It is also well known that achieving ~he high rates of convergence afforded by higher order bases may als'o require the employment of higher order geometry models. A number of publications have described the use of quadratic elements to model curved surfaces. The authors have shown in an EFIE formulation, applied to scattering by a PEC .sphere, that quadratic order elements may be insufficient to prevent the domination of modeling errors. In fact, on a PEC sphere with radius r = 0.58 Lambda(sub 0), a quartic order geometry representation was required to obtain a convergence benefi.t from quadratic bases when compared to the convergence rate achieved with linear bases. Initial trials indicate that, for a dielectric sphere of the same radius, - requirements on the geometry model are not as severe as for the PEC sphere. The authors will present convergence results for higher order bases as a function of the geometry model order in the hybrid BEM/FEM formulation applied to dielectric spheres. It is well known that the system matrix resulting from the hybrid BEM/FEM formulation is ill -conditioned. For many real applications, a good preconditioner is required to obtain usable convergence from an iterative solver. The authors have examined the use of an Incomplete LU Threshold (ILUT) preconditioner . to solver linear systems stemming from higher order BEM/FEM formulations in 2D scattering problems. Although the resulting preconditioner provided aD excellent approximation to the system inverse, its size in terms of non-zero entries represented only a modest improvement when compared with the fill-in associated with a sparse direct solver. Furthermore, the fill-in of the preconditioner could not be substantially reduced without the occurrence of instabilities. In addition to the results for these 2D problems, the authors will present iterative solution data from the application of the ILUT preconditioner to 3D problems.

Fink, P. W.↗
NASA NTRS1973

Chemistry and surface morphology of soil particles from Luna 20 LRL sample 22003.

Optical and scanning electron microscopy, scanning electron microprobes and energy dispersion techniques were applied in an analysis of six siliceous glass spheres, five siliceous glass-bonded agglutinates and one breccia fragment from Luna 20 sample 22003. It is theorized that local meteor impact processes might have been responsible for the formation of most of the glass spheres and that the impacts of relatively high velocity particles might have been responsible for the craters observed on the surfaces of the spheres. The concentrations of iron spherules on the surfaces of the glass spheres were generally lower than in similar Apollo 11 and 12 glass spheres.

Carter, J. L.↗
NASA NTRS1984

Quenched magnetite in cretaceous-tertiary boundary microtekite-like spheroid

The magnetite containing spheres collected from a kt boundary localities in Italy were analyzed. It was found that these spheres contain relatively high concentrations of Ir. The spheres were analyzed for siderophile elements Ir, Pt, Au, Pd, Os, and Re. Elements Ir, Pt, Pd, and Au were found in high concentrations in magnetic spheres and their concentrations are similar to those in most meteorites. It is suggested that the magnetite spheres do not contain a meteorite component which may be a relic of the kt event.

Smit, J.↗
NASA NTRS1984

Melting, ablation, and vapor phase condensation during atmospheric passage of the Bjurbole meteorite

A detailed study of the Bjurbole fusion crust using scanning electron microscopy (SEM) and energy dispersive analysis (EDS) shows that filamentary crystals and ablation spheres may form on the meteoroid surface. Filamentary crystals, hollow spheres, and porous regions of the surface point to a period of intense vapor phase activity during atmospheric passage. Filamentary crystals can be divided into three categories on the basis of bulk composition and morphology. Two types of filamentary crystals are vapor phase condensation products formed during atmospheric entry of the meteoroid. The other type forms by the interaction of seawater with the fusion surface. The density and composition of ablation spheres varies with the flight orientation of the meteorite. The size range and composition of iron-nickel spheres on the surface of Bjurbole are similar to spheres collected in the stratosphere. A comparison of stratospheric dust collections with meteorite surfaces may provide further insight into the mechanisms of meteoroid entry into planetary atmospheres.

Rietmeijer, F. J. M.↗
NASA NTRS1984

Platinum group nuggets in deep sea sediments

The existence of iron meteor oblation spheres in deep sea sediments was known for over a century. These spheres generally were believed to be composed of either pure magnetite and wustite or an oxide shell surrounding a NiFe metal core. A large number of 300 micron to 600 micron spheres found were pure oxide spheres, usually containing a solitary 10 micron platinum group nugget (pgn) composed almost entirely of group VIII metals. Twelve PGN's were analyzed and most had chondritic abundances with some depletions that correlate with element volatility. PGN formation by oxidation of a molten metal sphere entering the atmosphere cannot occur if the oxygen abundance in the atmosphere is less than half of its present value. The first appearance of PGN's in the geological record should mark when, in the Earth's history, oxygen rose to this level.

Brownlee, D. E.↗