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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Current collection in a magnetoplasma

The authors present a survey of a very incomplete subject, current collection in a magnetoplasma. The best-developed and simplest theories for current collection are steady-state collisionless theories, and these must be understood before departures from them can be analyzed usefully. Thus, the authors begin with a review of them. The authors include some recent numerical results which indicate that steady-state collisionless Laplace-limit currents remain substantially below the Parker-Murphy (1967) canonical upper bound out to very large electrode potentials, and approach it as a limit only very slowly if at all. Attempts to correct this theory for space-charge effects lead to potential disturbances which extend to infinite distance along the electrode's magnetic shadow, unless collisional effects are also taken into account. However, even a small amount of relative plasma drift motion, such as that involved in a typical rocket experiment, can change this conclusion fundamentally. It is widely believed that time-averaged current collection may be increased by effects of plasma turbulence, and the authors review the available evidence for and against this contention. Steady-state collisionless particle dynamics predicts the existence of a toroidal region of trapped orbits which surrounds the electrode. Light emissions from this region have been photographed, indicating that collisional ionization may also occur there, and this, and/or scattering by collisions or possibly turbulent fluctuations in this region, may also increase current collection by the electrode. The authors also discuss effects on particle motions near the electrode, associated with breakdown of magnetic insulation in the region of large electric fields near it.

Laframboise, Jim G.↗
NASA NTRS1993

Visible photoluminescence of porous Si(1-x)Ge(x) obtained by stain etching

We have investigated visible photoluminescence (PL) from thin porous Si(1-x)Ge(x) alloy layers prepared by stain etching of molecular-beam-epitaxy-grown material. Seven samples with nominal Ge fraction x varying from 0.04 to 0.41 were studied at room temperature and 80 K. Samples of bulk stain etched Si and Ge were also investigated. The composition of the porous material was determined using X-ray photoemission spectroscopy and Rutherford backscattering techniques to be considerably more Ge-rich than the starting epitaxial layers. While the luminescence intensity drops significantly with the increasing Ge fraction, we observe no significant variation in the PL wavelength at room temperature. This is clearly in contradiction to the popular model based on quantum confinement in crystalline silicon which predicts that the PL energy should follow the bandgap variation of the starting material. However, our data are consistent with small active units containing only a few Si atoms that are responsible for the light emission. Such units are present in many compounds proposed in the literature as the cause of the visible PL in porous Si.

Ksendzov, A.↗
NASA NTRS1994

Electron precipitation and mass motion in the 1991 June 9 white-light flare

We use H alpha line profiles as a diagnostic of mass motion and nonthermal electron precipitation in the white-light flare (WLF) of 1991 June 9 01:34 UT. We find only weak downflow velocities (approximately equals 10km/s) at the site of white-light emission, and comparable velocities elsewhere. We also find that electron precipitation is strongest at the WLF site. We conclude that continuum emission in this flare was probably caused by nonthermal electrons and not by dynamical energy transport via a chromospheric condensation.

Dela Beaujardiere, J. -F.↗
NASA NTRS1994

Nondestructive time-of-capture, location and velocity sensing in intact capture

Velocity sensing of hypervelocity particles was a significant field of interest from the 1960s to 1970s. Generically, velocity sensing has been approached by either of two methods: first, detecting direct plasma or light emissions onto a solid surface, or second, performing time-of-flight by film penetration, or by detecting charged particles passing a static electric field. Impact plasma techniques required the destruction of the particles. Multiple-film penetrations were also destructive, especially for small particles. There is a need for an integrated, reliable, and simple location and velocity sensor compatible to our intact capture underdense medium without contributing additional damage to the captured particle. Since cometary dust, like cosmic dust, is essentially randomly distributed, knowing the time of the dust capture and the location of the capture on the collector permits the identification of the specific dust particle captured. Velocity information helps to determine the trajectory of the dust particle. Our discovery of a very suitable acoustic sensor and fruitful experimental results have led to the realization of a flight velocity sensor with intact capture underdense media.

Tsou, Peter↗
NASA NTRS1992

JTEC panel on display technologies in Japan

This report is one in a series of reports that describes research and development efforts in Japan in the area of display technologies. The following are included in this report: flat panel displays (technical findings, liquid crystal display development and production, large flat panel displays (FPD's), electroluminescent displays and plasma panels, infrastructure in Japan's FPD industry, market and projected sales, and new a-Si active matrix liquid crystal display (AMLCD) factory); materials for flat panel displays (liquid crystal materials, and light-emissive display materials); manufacturing and infrastructure of active matrix liquid crystal displays (manufacturing logistics and equipment); passive matrix liquid crystal displays (LCD basics, twisted nematics LCD's, supertwisted nematic LCD's, ferroelectric LCD's, and a comparison of passive matrix LCD technology); active matrix technology (basic active matrix technology, investment environment, amorphous silicon, polysilicon, and commercial products and prototypes); and projection displays (comparison of Japanese and U.S. display research, and technical evaluation of work).

Tannas, Lawrence E., Jr.↗
NASA NTRS1996

The Onset of Resonance-Controlled Instability in Spherical Bubble Oscillations

Single bubble dynamics are investigated using acoustic techniques for isolation and manipulation. The goal of the investigations is to understand the dynamic origin of the various phenomena that bubbles exhibit: light emission, enhanced mass transport, chaotic and quasiperiodic oscillations, and translations. Once understood, acoustically manipulated bubbles can serve as platforms for materials effects on free surfaces, using surfactants to alter surface rheology and observing how that affects both dynamics and also mass transport. The effects of gravity on the problem will be shown to be significant. The first set of observations from 1g experimentation are presented. These observations are of the onset conditions for instability of the spherical shape of the bubble. For the size range 55-90 microns in diameter we observe instability governed by resonant mode coupling, which is significantly affected by the buoyant force and its effects.

Holt, R. Glynn↗
NASA NTRS1996

Inferences on Coronal Magnetic Fields from SOHO UVCS Observations

The characteristics of the magnetic field ubiquitously permeating the coronal plasma are still largely unknown. In this paper we analyze some aspects of coronal physics, related to the magnetic field behavior, which forthcoming SOHO UVCS observations can help better understand. To this end, three coronal structures will be examined: streamers, coronal mass ejections (CME's) and coronal holes. As to streamers and CME's, we show, via simulations of the Ly-alpha and white light emission from these objects, calculated on the basis of recent theoretical models, how new data from SOHO can help advancing our knowledge of the streamer/CME magnetic configuration. Our discussion highlights also those observational signatures which might offer clues on reconnection processes in streamers' current sheets. Coronal holes (CH's) are discussed in the last section of the paper. Little is known about CH flux tube geometry, which is closely related to the behavior of the solar wind at small heliocentric distances. Indirect evidence for the flux tube spreading factors, within a few solar radii, is here examined.

Poletto, G.↗
NASA NTRS1999

The Design of a Remote Sensing Data Acquisition Campaign for Precision Agriculture and Some Early Results

In the 1970s NASA and the Department of Agriculture attempted to use the new Landsat MSS system for agricultural purposes. The program had relatively little success. With the advent of differential GPS, yield monitors on harvest equipment and higher spatial resolution remote sensing systems it seemed likely the situation should be reexamined. Therefore, a campaign of data acquisition involving remote sensing and other modalities with dependent research was assembled and funded by the Space Grant Consortia in Alabama and Georgia. The design of the remote sensing data acquisition was driven by the biology and physics of the crop system and limited by the available sensor platforms. Major parameters included crop stage, spatial resolution, seasonal and daily weather conditions, and which portion of the EM spectrum would actually capture the most discriminating information. Joint visible and Near IR with Thermal IR would permit use of existing indices, such as greenness, as well as phenomena driven by the plant' s evapotranspiration. Spatial resolution in the 2-5 meter range was chosen, avoiding many complexities caused by aliasing crop row spacing at, higher resolutions yet finer than the harvester's tightest recording rate. This dictates use of an airborne system. Use of an airborne system also makes scheduling around weather much simpler than use of satellite data. Active video calibration was recognized as essential if quantitative measures were ever to be obtained or reproduced. The system would also have to have onboard geoOF1 Based on these elements 3 data acquisitions have been flown. Seven flight lines were flown twice in 1998 and 16 lines flown in 1999. Total raw data is several GBytes. All of the data has now been geometrically corrected and some preliminary analysis accomplished. The thermal bands have an extremely high correlation with yield. For one@test case with corn, correlation in excess of 0.86 was obtained from a data acquisition two months prior to harvest! Soil images show significant within field variation in clay, soil brightness and emissivity. Light wind has been found to effect the reflectance and temperature of broad leaf crops, including soybeans, cotton and peanuts. Clearly, this work has already demonstrated some very important results. With continued development of the remote sensing technology there is good reason to believe this research will soon be able to help the individual farmer.

Rickmanl, D.↗
NASA NTRS2000

Charge Generation and Propagation in Igneous Rocks

Resistivity changes, ground potentials, electromagnetic (EM) and luminous signals prior to or during earthquakes have been reported, in addition to ground uplift and tilt, and to changes in the seismic wave propagation parameters. However, no physical model exists that ties these diverse phenomena together. Through time-resolved impacts experiments it has been observed that, when igneous rocks (gabbro, diorite, granite) are impacted at low velocities (approx. 100 m/sec), highly mobile electronic charge carriers are generated, spreading from a small volume near the impact point, causing electric potentials, EM and light emission. The rock becomes momentarily conductive. When impacted at higher velocities (approx. 1.5 km/sec), the propagation of the P and S waves is registered through the transient piezoelectric response of quartz. At the same time, the rock volume is filled with mobile charge carriers, and a positive surface potential is registered. During the next 1-2 msec the surface potential oscillates, due to electron injection from ground. These observations are consistent with positive holes, e.g. defect electrons in the O(2-) sublattice, that can travel via the O 2p-dominated valence band of the silicate minerals at the speed of a phonon-mediated charge transfer. Before activation, the positive hole charge carriers lay dormant in form of positive hole pairs, PHP, electrically inactive, chemically equivalent to peroxy links in the structures of constituent minerals. PHPs are introduced by way of hydroxyl (O3Si-OH) incorporated into nominally anhydrous minerals when they crystallize in water-laden environments. Given that sound waves of even relatively low intensity appear to cause PHPs dissociation, thus generating mobile positive holes, it is proposed that microfracturing during rock deformation cause PHP dissociation. Depending on where and how much the rock volume is stressed, the positive holes are expected to form fluctuating charge clouds in the earthquake source region that may account for earthquake-related electrical phenomena and the reported low frequency EM signals.

Freund, Friedemann↗
NASA NTRS2002

Image Dis-Integration for Improved Plasmasphere Visualization

Traditionally, study of the plasmasphere has involved terrestrial observation of local characteristics. Global modeling of the plasmasphere in such an observation regime made use of an ensemble of (sparse) local measurements. Recently, sensors aboard the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite (in particular, the EUV (Extreme Ultra Violet) Imager) have created the potential for truly global study of the plasmasphere. IMAGE was launched in spring of 2000 in an orbit with apogee altitude 7.2 R E (Earth radii) and perigee altitude 1000 km. IMAGE's EUV sensor allows an external view of the distribution of cold plasma in the plasmasphere to be acquired. EUV is designed to image light emission at 30.4 nanometers, which is the emission wavelength of the He + ion in the presence of solar radiation. He + makes up approximately 15-20% of the plasma in the plasmasphere, thus imaging of He + enables determination of plasma distribution. The EUV instrument provides a 90° by 84° field of view which is imaged as an equally spaced 150x140 pixel array on a spherical imaging surface. The EUV produces an image approximately every 10 minutes when the sensor is operating. Since EUV images contain line-of-sight integrations of plasma distributions, they do not directly express equatorial plane density (which would enable comparison of observed plasma distributions with predictions from models). Furthermore, the plasma density at any point in three-space is not known. The goal of our work was development of a technique that can enable plasma density to be determined throughout three-space. Our approach to creation of a three-space representation of the plasma distribution involves disintegrating the EUV lines of sight to form a volumetric map of plasma densities.

Timothy S. Newman↗
NASA NTRS1981

Gem Analysis

World Gem Laboratory, Inc.'s cathodoluminoscope is an instrument that magnifies a specimen and produces heat-generated light emissions that bring out features important in gemological analysis. It can indicate whether a stone can be successfully cut, useful in the study of growth and strain patterns in diamonds, detection of dyes in jade, and analysis of the growth and structure of rubies and sapphires. In combination with other tests these analyses can separate synthetic from natural gems.

Source record↗
NASA NTRS2003

Deposition of Nanostructured Thin Film from Size-Classified Nanoparticles

Materials comprising nanometer-sized grains (approximately 1_50 nm) exhibit properties dramatically different from those of their homogeneous and uniform counterparts. These properties vary with size, shape, and composition of nanoscale grains. Thus, nanoparticles may be used as building blocks to engineer tailor-made artificial materials with desired properties, such as non-linear optical absorption, tunable light emission, charge-storage behavior, selective catalytic activity, and countless other characteristics. This bottom-up engineering approach requires exquisite control over nanoparticle size, shape, and composition. We describe the design and characterization of an aerosol system conceived for the deposition of size classified nanoparticles whose performance is consistent with these strict demands. A nanoparticle aerosol is generated by laser ablation and sorted according to size using a differential mobility analyzer. Nanoparticles within a chosen window of sizes (e.g., (8.0 plus or minus 0.6) nm) are deposited electrostatically on a surface forming a film of the desired material. The system allows the assembly and engineering of thin films using size-classified nanoparticles as building blocks.

Camata, Renato P.↗
NASA NTRS2005

Development of Ionic Liquid Monopropellants for In-Space Propulsion

A family of new, low toxicity, high energy monopropellants is currently being evaluated at NASA Marshall Space Flight Center for in-space rocket engine applications such as reaction control engines. These ionic liquid monopropellants, developed in recent years by the Air Force Research Laboratory, could offer system simplification, less in-flight thermal management, and reduced handling precautions, while increasing propellant energy density as compared to traditional storable in-space propellants such as hydrazine and nitrogen tetroxide. However, challenges exist in identifying ignition schemes for these ionic liquid monopropellants, which are known to burn at much hotter combustion temperatures compared to traditional monopropellants such as hydrazine. The high temperature combustion of these new monopropellants make the use of typical ignition catalyst beds prohibitive since the catalyst cannot withstand the elevated temperatures. Current research efforts are focused on monopropellant ignition and burn rate characterization, parameters that are important in the fundamental understanding of the monopropellant behavior and the eventual design of a thruster. Laboratory studies will be conducted using alternative ignition techniques such as laser-induced spark ignition and hot wire ignition. Ignition delay, defined as the time between the introduction of the ignition source and the first sign of light emission from a developing flame kernel, will be measured using Schlieren visualization. An optically-accessible liquid monopropellant burner, shown schematically in Figure 1 and similar in design to apparatuses used by other researchers to study solid and liquid monopropellants, will be used to determine propellant burn rate as a function of pressure and initial propellant temperature. The burn rate will be measured via high speed imaging through the chamber s windows.

Blevins, John A.↗
NASA NTRS2005

Development of Ionic Liquid Monopropellants for In-Space Propulsion

A family of new, low toxicity, high energy monopropellants is currently being evaluated at NASA Marshall Space Flight Center for in-space rocket engine applications such as reaction control engines. These ionic liquid monopropellants, developed in recent years by the Air Force Research Laboratory, could offer system simplification, less in-flight thermal management, and reduced handling precautions, while increasing propellant energy density as compared to traditional storable in-space propellants such as hydrazine and nitrogen tetroxide. However, challenges exist in identifying ignition schemes for these ionic liquid monopropellants, which are known to burn at much hotter combustion temperatures compared to traditional monopropellants such as hydrazine. The high temperature combustion of these new monopropellants make the use of typical ignition catalyst beds prohibitive since the catalyst cannot withstand the elevated temperatures. Current research efforts are focused on monopropellant ignition and burn rate characterization, parameters that are important in the fundamental understanding of the monopropellant behavior and the eventual design of a thruster. Laboratory studies will be conducted using alternative ignition techniques such as laser-induced spark ignition and hot wire ignition. Ignition delay, defined as the time between the introduction of the ignition source and the first sign of light emission from a developing flame kernel, will be measured using Schlieren visualization. An optically-accessible liquid monopropellant burner will be used to determine propellant burn rate as a function of pressure and initial propellant temperature. The burn rate will be measured via high speed imaging through the chamber s windows.

Blevins, John A.↗
NASA NTRS2003

Midinfrared Temperature Measurement Technique Developed

Infrared thermography is the measuring of the temperature of an object by examining the spectral quantities of light emission. The microgravity combustion experiment Solid Inflammability Boundary at Low-Speeds (SIBAL) calls for full-field temperature measurements of a thin sheet of cellulosic fuel as a flame front moves across the fuel, and infrared thermography is the only technique that can accomplish this task. The thermography is accomplished by imaging the fuel with a midinfrared camera that is sensitive in the 3.0- to 5.0-microns wavelength region in conjunction with a 3.7 - to 4.1-microns bandpass filter to eliminate unwanted infrared radiation from components other than the fuel.

Santosuosso, George R.↗
NASA NTRS2005

Mechanical Impact Testing: A Statistical Measurement

In the decades since the 1950s, when NASA first developed mechanical impact testing of materials, researchers have continued efforts to gain a better understanding of the chemical, mechanical, and thermodynamic nature of the phenomenon. The impact mechanism is a real combustion ignition mechanism that needs understanding in the design of an oxygen system. The use of test data from this test method has been questioned due to lack of a clear method of application of the data and variability found between tests, material batches, and facilities. This effort explores a large database that has accumulated over a number of years and explores its overall nature. Moreover, testing was performed to determine the statistical nature of the test procedure to help establish sample size guidelines for material characterization. The current method of determining a pass/fail criterion based on either light emission or sound report or material charring is questioned.

Engel, Carl D.↗
NASA NTRS2004

Effect of anharmonicity of interatomic potential on strain distribution in semiconductor nanostructures

Experiments and theory have shown that the energy spectrum of nanostructures is extremely sensitive to the built-in strain. Knowledge of the strain distribution is therefore Experiments and theory have shown that the energy spectrum of nanostructures is extremely sensitive to the built-in strain. Knowledge of the strain distribution is therefore of utmost importance for the design of optical devices with prescribed light emission spectrum.

nanostructures↗
NASA NTRS2008

Operational Characteristics and Plasma Measurements in a Low-Energy FARAD Thruster

Pulsed inductive plasma accelerators are spacecraft propulsion devices in which energy is stored in a capacitor and then discharged through an inductive coil. The device is electrodeless, inducing a plasma current sheet in propellant located near the face of the coil. The propellant is accelerated and expelled at a high exhaust velocity (order of 10 km/s) through the interaction of the plasma current with an induced magnetic field. The Faraday Accelerator with RF-Assisted Discharge (FARAD) thruster is a type of pulsed inductive plasma accelerator in which the plasma is preionized by a mechanism separate from that used to form the current sheet and accelerate the gas. Employing a separate preionization mechanism in this manner allows for the formation of an inductive current sheet at much lower discharge energies and voltages than those found in previous pulsed inductive accelerators like the Pulsed Inductive Thruster (PIT). In this paper, we present measurements aimed at quantifying the thruster's overall operational characteristics and providing additional insight into the nature of operation. Measurements of the terminal current and voltage characteristics during the pulse help quantify the output of the pulsed power train driving the acceleration coil. A fast ionization gauge is used to measure the evolution of the neutral gas distribution in the accelerator prior to a pulse. The preionization process is diagnosed by monitoring light emission from the gas using a photodiode, and a time-resolved global view of the evolving, accelerating current sheet is obtained using a fast-framing camera. Local plasma and field measurements are obtained using an array of intrusive probes. The local induced magnetic field and azimuthal current density are measured using B-dot probes and mini-Rogowski coils, respectively. Direct probing of the number density and electron temperature is performed using a triple probe.

Polzin, K. A.↗