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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Analysis of Mount St. Helens ash from optical photoelectric photometry

The optical properties of suspended dust particles from the eruption of Mt. St. Helens on July 23, 1980 are investigated using photoelectric observations of standard stars obtained on the 0.76-m telescope at the University of Washington 48 hours after the eruption. Measurements were made with five broad-band filters centered at 3910, 5085, 5480, 6330, and 8050 A on stars of varying color and over a wide range of air masses. Anomalous extinction effects due to the volcanic ash were detected, and a significant change in the wavelength-dependent extinction parameter during the course of the observations was established by statistical analysis. Mean particle size (a) and column density (N) are estimated using the Mie theory, assuming a log-normal particle-size distribution: a = 0.18 micron throughout; N = 1.02 x 10 to the 9th/sq cm before 7:00 UT and 2.33 x 10 to the 9th/sq cm after 8:30 UT on July 25, 1980. The extinction is attributed to low-level, slowly migrating ash, possibly combined with products of gas-to-particle conversion and coagulation.

Cardelli, J. A.↗
NASA NTRS2014

Real Time Volcanic Cloud Products and Predictions for Aviation Alerts

Volcanic eruptions can inject significant amounts of sulfur dioxide (SO2) and volcanic ash into the atmosphere, posing a substantial risk to aviation safety. Ingesting near-real time and Direct Readout satellite volcanic cloud data is vital for improving reliability of volcanic ash forecasts and mitigating the effects of volcanic eruptions on aviation and the economy. NASA volcanic products from the Ozone Monitoring Insrument (OMI) aboard the Aura satellite have been incorporated into Decision Support Systems of many operational agencies. With the Aura mission approaching its 10th anniversary, there is an urgent need to replace OMI data with those from the next generation operational NASA/NOAA Suomi National Polar Partnership (SNPP) satellite. The data provided from these instruments are being incorporated into forecasting models to provide quantitative ash forecasts for air traffic management. This study demonstrates the feasibility of the volcanic near-real time and Direct Readout data products from the new Ozone Monitoring and Profiling Suite (OMPS) ultraviolet sensor onboard SNPP for monitoring and forecasting volcanic clouds. The transition of NASA data production to our operational partners is outlined. Satellite observations are used to constrain volcanic cloud simulations and improve estimates of eruption parameters, resulting in more accurate forecasts. This is demonstrated for the 2012 eruption of Copahue. Volcanic eruptions are modeled using the Goddard Earth Observing System, Version 5 (GEOS-5) and the Goddard Chemistry Aerosol and Radiation Transport (GOCART) model. A hindcast of the disruptive eruption from Iceland's Eyjafjallajokull is used to estimate aviation re-routing costs using Metron Aviation's ATM Tools.

Volcanic ash↗
NASA NTRS2022

Circular Polarization in Atmospheric Aerosols

Recent technological advances have demonstrated the feasibility of deploying spaceborne optical detectors with full polarimetric capabilities. The measurement of all four Stokes coefficients opens significant new opportunities for atmospheric aerosol studies and applications. While considerable amounts of attention have been dedicated to sensors with sensitivity to the total intensity and linear polarization (represented by Stokes coefficients I, U, Q), there has been less attention to the additional information brought by measuring circular polarization (coefficient V). This report fills this gap in knowledge by providing an overview of aerosol sources of circular polarization in the atmosphere and discusses possible remote sensing signatures. In this manuscript, circularly polarized radiation that results from the interaction of incident unpolarized radiation are considered in three physical settings: optical activity originating in biogenic aerosols, alignment of non-spherical particles in the presence of electrical fields (such as dust, smoke, and volcanic ash) and aerosol multiple scattering effects. Observational and theoretical evidence of, and the settings and conditions for non-zero aerosol circular polarization generated from incident unpolarized radiation are here gathered and discussed. In addition, novel radiative transfer simulations are shown to illustrate notable spectral and other features where circular polarization may provide additional information that is possibly independent from total intensity and linear polarization only observations. Current techniques for detection of aerosol composition (also referred as aerosol type) from space provide limited information. Remote identification of aerosols such as smoke, volcanic ash, and dust particles can only be accomplished with some degree of confidence for moderate to high concentrations. When the same aerosols are found at lower concentrations (but still high enough to be of importance for air quality and cloud formation), these methods often produce ambiguous results. The circular polarization of aerosols is rarely utilized, and we explore its value for improved determination aerosol composition. This study is presented as an overview with a goal to provide a new perspective on an overlooked optical property and to trigger interest in further exploration of this subject.

Aerosol type↗
NASA NTRS1990

Ellipsometric analysis of materials degradation in space

The fundamentals of variable angle spectroscopic ellipsometry (VASE) are reviewed, and its usefulness in studying the effect of atomic oxygen on space coatings such as indium tin oxide (ITO), silicon dioxide, and aluminum oxide is discussed. Monolayer sensitive and nondestructive VASE is found to be an effective technique for monitoring the atomic oxygen diffusion through the aluminum oxide and silicon dioxide protective overcoatings on space reflectors. Ashing of ITO/silicon samples had the net effect of annealing the film inside the plasma. The annealing effect was supported both by structural changes as verified by X-ray diffraction measurements and by increased absorbance in the spectral range below 3 eV as measured by VASE.

Woollam, John A.↗
NASA NTRS2013

Multi-Partner Experiment to Test Volcanic-Ash Ingestion by a Jet Engine

A research team of U.S. Government agencies and engine manufacturers are designing an experiment to test volcanic-ash ingestion by a NASA owned F117 engine that was donated by the U.S. Air Force. The experiment is being conducted under the auspices of NASA s Vehicle Integrated Propulsion Research (VIPR) Program and will take place in early 2014 at Edwards AFB in California as an on-ground, on-wing test. The primary objectives are to determine the effect on the engine of several hours of exposure to low to moderate ash concentrations, currently proposed at 1 and 10 mg/m3 and to evaluate the capability of engine health management technologies for detecting these effects. A natural volcanic ash will be used that is representative of distal ash clouds many 100's to approximately 1000 km from a volcanic source i.e., the ash should be composed of fresh glassy particles a few tens of microns in size. The glassy ash particles are expected to soften and become less viscous when exposed to the high temperatures of the combustion chamber, then stick to the nozzle guide vanes of the high-pressure turbine. Numerous observations and measurements of the engine s performance and degradation will be made during the course of the experiment, including borescope and tear-down inspections. While not intended to be sufficient for rigorous certification of engine performance when ash is ingested, the experiment should provide useful information to aircraft manufacturers, airline operators, and military and civil regulators in their efforts to evaluate the range of risks that ash hazards pose to aviation.

Lekki, John↗
NASA NTRS2009

Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical Applications

The purpose of this study was to determine the effect of atomic oxygen (AO) exposure on the hydrophilicity of nine different polymers for biomedical applications. Atomic oxygen treatment can alter the chemistry and morphology of polymer surfaces, which may increase the adhesion and spreading of cells on Petri dishes and enhance implant growth. Therefore, nine different polymers were exposed to atomic oxygen and water-contact angle, or hydrophilicity, was measured after exposure. To determine whether hydrophilicity remains static after initial atomic oxygen exposure, or changes with higher fluence exposures, the contact angles between the polymer and water droplet placed on the polymer s surface were measured versus AO fluence. The polymers were exposed to atomic oxygen in a 100-W, 13.56-MHz radio frequency (RF) plasma asher, and the treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers. Pristine samples were compared with samples that had been exposed to AO at various fluence levels. Minimum and maximum fluences for the ashing trials were set based on the effective AO erosion of a Kapton witness coupon in the asher. The time intervals for ashing were determined by finding the logarithmic values of the minimum and maximum fluences. The difference of these two values was divided by the desired number of intervals (ideally 10). The initial desired fluence was then multiplied by this result (2.37), as was each subsequent desired fluence. The flux in the asher was determined to be approximately 3.0 x 10(exp 15) atoms/sq cm/sec, and each polymer was exposed to a maximum fluence of 5.16 x 10(exp 20) atoms/sq cm.

deGroh, Kim↗
NASA NTRS1982

Problems in the climatology of the 1980 Mount St. Helens eruptions

A brief review of the effects of climate and weather on the 1980 Mount St. Helens eruptions and the subsequent dispersion of ash and gases and the reciprocal influences of the eruptions on climate and climatology is presented. The effects of mesoscale destruction of snow fields and vegetation, a revised mountain profile, and ash deposits are addressed along with impacts on hemispheric climate and disruption of normal climatological observations, in the areas directly affected by the explosions and ashfall. Environmental and economic consequences are also considered.

Critchfield, H. J.↗
NASA NTRS1974

On the theory of compliant wall drag reduction in turbulent boundary layers

A theoretical model has been developed which can explain how the motion of a compliant wall reduces turbulent skin friction drag. Available experimental evidence at low speeds has been used to infer that a compliant surface selectively removes energy from the upper frequency range of the energy containing eddies and through resulting surface motions can produce locally negative Reynolds stresses at the wall. The theory establishes a preliminary amplitude and frequency criterion as the basis for designing effective drag reducing compliant surfaces.

Ash, R. L.↗
NASA NTRS1983

Experimental design of an interlaboratory study for trace metal analysis of liquid fluids

The accurate determination of trace metals and fuels is an important requirement in much of the research into and development of alternative fuels for aerospace applications. Recognizing the detrimental effects of certain metals on fuel performance and fuel systems at the part per million and in some cases part per billion levels requires improved accuracy in determining these low concentration elements. Accurate analyses are also required to ensure interchangeability of analysis results between vendor, researcher, and end use for purposes of quality control. Previous interlaboratory studies have demonstrated the inability of different laboratories to agree on the results of metal analysis, particularly at low concentration levels, yet typically good precisions are reported within a laboratory. An interlaboratory study was designed to gain statistical information about the sources of variation in the reported concentrations. Five participant laboratories were used on a fee basis and were not informed of the purpose of the analyses. The effects of laboratory, analytical technique, concentration level, and ashing additive were studied in four fuel types for 20 elements of interest. The prescribed sample preparation schemes (variations of dry ashing) were used by all of the laboratories. The analytical data were statistically evaluated using a computer program for the analysis of variance technique.

Greenbauer-Seng, L. A.↗
NASA NTRS1992

Thermal disequilibrium at the top of volcanic clouds and its effect on estimates of the column height

Satellite images of large volcanic explosions reveal that the tops of volcanic eruptions columns are much cooler than the surrounding atmosphere. It is proposed that this effect occurs whenever a mixture of hot volcanic ash and entrained air ascends sufficiently high into a stably stratified atmosphere. Although the mixture is initially very hot, it expands and cools as the ambient pressure decreases. It is shown that cloud-top undercoolings in excess of 20 C may develop in clouds that penetrate the stratosphere, and it is predicted that, for a given cloud-top temperature, variations in the initial temperature of 100-200 C may correspond to variations in the column height of 5-10 km. It is deduced that the present practice of converting satellite-based measurements of the temperature at the top of volcanic eruptions columns to estimates of the column height will produce rather inaccurate results and should therefore be discontinued.

Woods, Andrew W.↗
NASA NTRS1982

Simulation studies of the physical and chemical processes occurring in the stratospheric clouds of the Mount St. Helens eruptions of May and June 1980

The large and diverse set of observational data collected in the high-altitude clouds of May 18, May 25, and June 13, 1980 was organized and analyzed for trends which reveal the processes at work. The data were used to guide and constrain model simulations of the volcanic eruptions. A comprehensive one-dimensional model of stratospheric sulfate aerosols, sulfur precursor gases, and volcanic ash and dust particles is utilized which accounts for homogeneous and heterogeneous chemistry in the clouds, aerosol nucleation and growth, and cloud expansion. Computational results are given for the time histories of the gaseous species concentrations, sulfate aerosol size dispersions, and ash burdens in the eruption clouds. The long-term buildup of stratospheric aerosols in the Northern Hemisphere and the persistent effects of injected chlorine and water vapor on ozone are discussed. It is concluded that SO2, water vapor, and ash are the most important substances injected by the volcano into the stratosphere, with respect to both the widespread effects on composition and the impact on climate. It is found that the volcano probably had little influence on the climate ( 0.05 K global surface cooling) or on stratospheric ozone ( 0.2 percent maximum hemispherical reduction).

Turco, R. P.↗
NASA NTRS1989

Self-limiting physical and chemical effects in volcanic eruption clouds

One-dimensional aerosol microphysical and photochemical models are used to study the chemistry of stratospheric volcanic clouds. The results indicate that the aerosol microphysical processes of condensation and coagulation produce larger particles as the SO2 injection rate is increased. Larger particles have a smaller optical depth per unit mass and settle out of the stratosphere at a faster rate than smaller ones, restricting the total number of particles in the stratosphere. The microphysical processes moderate the impact of volcanic clouds on the earth's radiation budget and climate, suggesting that volcanic effects may be self limiting. It is noted that the injection of HCl into the stratosphere, which could lead to large ozone changes, is limited by a cold trap effect in which HCl and water vapor condense on ash particles in the rising volcanic plume and fall out as ice.

Pinto, Joseph P.↗
NASA NTRS1983

The 1980 eruptions of Mount St. Helens - Physical and chemical processes in the stratospheric clouds

The large and diverse set of observational data collected in the high-altitude plumes of the May 18, May 25, and June 13, 1980 eruptions is organized and analyzed with a view to discerning the processes at work. The data serve to guide and constrain detailed model simulations of the volcanic clouds. For this purpose, use is made of a comprehensive one-dimensional model of stratospheric sulfate aerosols, sulfur precursor gases, and volcanic ash and dust. The model takes into account gas-phase and condensed-phase (heterogeneous) chemistry in the clouds, aerosol nucleation and growth, and cloud expansion. Computational results are presented for the time histories of the gaseous species concentrations, aerosol size distributions, and ash burdens of the eruption clouds. Also investigated are the long-term buildup of stratospheric aerosols in the Northern Hemisphere and the persistent effects of injected chlorine and water vapor on stratospheric ozone. It is concluded that SO2, water vapor, and ash were probably the most important substances injected into the stratosphere by the Mount St. Helens volcano, both with respect to their widespread effects on composition and their effect on climate.

Turco, R. P.↗
NASA NTRS2002

Noachian Martian Volcanics a Water Source

H2O was supplied to the Noachian atmosphere by eruptions, or in association with large impacts. Most water outgassed into an extremely cold atmosphere, and condensate deposits were inevitable. High heat flow could lead to subglacial melting only if ice thicknesses were greater than 500-1000m, which is extremely unlikely. Subareal melting and flow is contingent upon temperatures periodically exceeding 273 K, and retarding evaporative loss of the flow. In still air, evaporation into a dry atmosphere is in the free convection regime, and a stream with 2 cu m/s discharge, flowing 1 m/s could persist for hundreds of days and cover distances greater than any valley reach. The zero-wind-shear condition is considered implausible however. We investigate the possibility that evaporation rates were suppressed because the atmosphere was regionally charged with H2O as it moved over snow/ice fields. Our initial concern is precipitation from volcanic plumes. A Kilauea-style eruption on the martian surface would cover a 10km circular deposit with 10cm of H2O, if all H2O could be precipitated near the vent. The characteristics of the eruption at the vent, (vent size, temperature, H2O content, etc.) are independent of the environmental conditions. The subsequent behavior of the plume, including precipitation of ash and H2O condensate depends strongly on the environment. Hence, the proximal fate of volcanic H2O is amenable to treatment in a model. A simple bulk thermodynamic model of the rise of an H2O plume through a stably stratified CO2 atmosphere, with only adiabatic cooling, produces runaway plume rise. A more complex treatment includes the effects of latent heat release, wind shear along the plume, divergence of ash and H2O, and will yield more realistic estimates of H2O transport in eruptive plumes. Results of these simulations will be presented.

Zent, A. P.↗
NASA NTRS1983

Sputtered coatings for protection of spacecraft polymers

Kapton polyimide oxidizes at significant rates (4.3x10(-24) gram/incident oxygen atom) when exposed in low Earth orbit to the ram atomic oxygen flux. Ion beam sputter deposited thin films of Al2O3 and SiO2 as well as a codeposited mixture of predominantly SiO2 with a small amount of polytetrafluoroethylene were evaluated and found to be effective in protecting Kapton from oxidation in both laboratory plasma ashing tests as well as in space on board shuttle flight STS-8. A protective film of or = 96 percent SiO2 and or = 4 percent polytetrafluoroethylene was found to be very flexible compared to the pure metal oxide coatings and resulted in mass loss rates that were 0.2 percent of that of the unprotected Kapton. The optical properties of Kapton for wavelengths investigated between 0.33 and 2.2 microns were not significantly altered by the presence of the coatings or changed by exposure of the coated Kapton to the low Earth orbital ram environment.

Banks, B. A.↗
NASA NTRS1994

Yield and seed oil content response of dwarf, rapid-cycling Brassica to nitrogen treatments, planting density, and carbon dioxide enrichment

Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to 2093 plants/m2) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, Genome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, including nonsupplemented (ambient) or elevated CO2 concentrations (998 +/- 12 micromoles mol-1). The highest seed yield rate obtained (4.4 g m-2 day-1) occurred with the lowest N level (15 mM) applied at the latest treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by delaying the onset of flowering and senescence and stimulating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g m-2 day-1) occurred with the highest N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latest treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Seed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of N level and time of N increase were consistently significant for most crop responses. Planting density was significant only under elevated CO2 conditions.

Non-NASA Center↗
NASA NTRS1972

Lunar ash flow with heat transfer.

The most important heat-transfer process in the ash flow under consideration is heat convection. Besides the four important nondimensional parameters of isothermal ash flow (Pai et al., 1972), we have three additional important nondimensional parameters: the ratio of the specific heat of the gas, the ratio of the specific heat of the solid particles to that of gas, and the Prandtl number. We reexamine the one dimensional steady ash flow discussed by Pai et al. (1972) by including the effects of heat transfer. Numerical results for the pressure, temperature, density of the gas, velocities of gas and solid particles, and volume fraction of solid particles as function of altitude for various values of the Jeffreys number, initial velocity ratio, and two different gas species (steam and hydrogen) are presented.

Pai, S. I.↗