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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

A spectroscopic study of intermediates in the condensation of refractory smokes - Matrix isolation experiments of SiO

The infrared and Raman spectra of N2 matrix-isolated silicon oxides were investigated. The vibrational frequencies of SiO, Si2O2, and Si3O3 were identified and assigned on the basis of normal coordinate analyses. Heating the solid to approximately 50 K (evaporating the matrix) leaves a residue whose infrared spectrum is identical to that of a smoke condensed at ambient temperatures. Further heating of the sample to approximately 500 K leads to significant changes in the band shapes. Investigations of the infrared spectra at several stages of the diffusion process enable a mechanism to be proposed for the transition from molecular properties to those of the residue (bulk) material, which has been characterized as Si2O3.

Khanna, R. K.↗
NASA NTRS1983

Laboratory studies of the condensation and properties of amorphous silicate smokes

The results of experiments intended for defining the vapor phase condensation of refractory materials are reported, and the usefulness of applying laboratory data to astrophysical conditions is assessed. The testing apparatus used produced Mg-SiO smokes by boiling powders in an evaporator. Critical temperatures for the onset of nucleation were measured for SiO-H2 and Mg-SiO-H2 systems. Spectroscopic examination of the grains produced were determined to be similar to the spectra obtained from both carbonaceous chondrites and several stratospheric micrometeorites. The experiments demonstrated that direct nucleation of refractory silicates from the vapor phase yielded amorphous, metastable particles, resembling more circumstellar grains than a chondritic matrix. It is suggested that the formation of SiO(x) may control nucleation in oxygen-rich stars.

Nuth, J. A.↗
NASA NTRS1986

A smoke-wire study of low Reynolds number flow over a NASA LRN(1) - 1007 airfoil section

Smoke-filament visualization photographs are presented for two-dimensional flow over a NASA LRN(1) - 1007 airfoil section designed specifically for high-efficiency operation at low chord Reynolds numbers. Results are included for chord Reynolds numbers of 60,000, 100,000, and 220,000 and for angles of attack ranging from 0 to 16 degrees. Two kinds of laminar separation bubble are found to develop in the flow over the airfoil. The sites and characteristics of formation of these bubbles are described, and their dimensional properties are estimated. The transition-to-turbulence Reynolds numbers, surface pressure coefficient distributions, and lift coefficients deduced from the measured coefficients are compared with those obtained by other authors.

Fisher, S. S.↗
NASA NTRS1988

Method of cold smoke generation for vortex core tagging

Attention is given to the flow-visualization problem posed by the 'dark-core' region of the vortices formed on the upper side of a delta wing; the low particle density in the core region minimizes the density of tracing particles whose presence is essential in LDV measurements. An effort is presently undertaken using TiCl4 smoke in subsonic wind tunnel tests of a 70-deg sweep delta wing model.

Nelson, R. C.↗
NASA NTRS1989

Oxygen isotopic fractionation in the condensation of refractory smokes

This paper reports preliminary measurements of the oxygen isotopic fractionation that occurs during the condensation of refractory metal oxide smokes. Fractionation occurred at temperatures in excess of 500 K during and/or subsequent to reaction of SiH4, Fe(CO)5, Al(CH3)3, and O2 in a H2 carrier gas. Observed isotopic fractionation was as high as -15 per mil/amu. The magnitude of the isotopic fractionation suggests that the process is kinetically controlled since the effect is greatly in excess of that expected for equilibrium isotopic exchange.

Nelson, R.↗
NASA NTRS1990

Climate and smoke - An appraisal of nuclear winter

A reevaluation is presented of the 'nuclear winter' scenario of Turco et al. (1983). New pertinent data have emerged from laboratory studies, field experiments, and numerical models on the smoke-plume, mesoscale, and global scales. A full-scale nuclear exchange's probable soot injections lead, in three-dimensional climate simulations, to midsummer land temperature decreases averaging 10-20 C in northern midlatitudes, with local cooling of as much as 35 C. Anomalous circulation patterns due to solar heating of the soot could stabilize the upper atmosphere against overturning, thereby prolonging the soot's residence time in the atmosphere. Monsoon disruptions and severe ozone layer depletion are also foreseen.

Turco, R. P.↗
NASA NTRS1991

Tridymite and maghemite formation in an Fe-SiO smoke

Grains produced in porous Fe-SiO smoke are analyzed by means of electron microscopy to determine their crystallographical, morphological, and chemical properties. The nucleation of metal oxide condensates takes place as the vapor evolves in a condensation-flow apparatus, initially producing simple crystalline phases. Fe nucleation follows, and the subsequent heterogeneous nucleation of quenched mixed high-Fe silica grains exhibits associated Fe-depletion, eventually producing pure silica grains. The coalescence exhibited by the pure silica grains is compatible with the higher surface energy found in the pure silica phase. During coagulation the grains melt and anneal to a chemically pure mixture of alpha- and beta-tridymite, and the precipitation of amorphous silica material is observed. The settling of grains in evolving solar nebula is theorized to be related to the stickiness of this material, and maghemite is suggested to contribute to the Fe/Si fractionation in solar nebula.

Rietmeijer, F. J. M.↗
NASA NTRS1991

Smoke palls induced by Kuwaiti oilfield fires mapped from Space Shuttle imagery

Consideration is given to initial observations on the Kuwaiti oilfield fires and the spatial and areal extent of these smoke palls as viewed from the Space Shuttle flights during April/May 1991. It is concluded that one of the early lessons learned from Kuwaiti oilfield fires is that the presence of intelligent observers on orbit is of great value for acquiring data and confirm/deny events.

Lulla, Kamlesh P.↗
NASA NTRS1991

Aerosol characterization in smoke plumes from a wetlands fire

Results are presented from airborne measurements of aerosol mass loading, size distribution, and elemental composition obtained in a smoke plume from a fire at a Florida wildlife refuge. It is found that there was a high concentration of carbon-containing aerosols and salt crystals in the 0.1-0.2 micron size range; the composition and morphology of the aerosols differed with size. Aerosol mass concentrations are used in conjunction with those obtained for CO2 in order to calculate ratios of aerosol and CO2. The ratios are noted to be higher for the smoldering phase of the fire than for its flaming phase.

Woods, David C.↗
NASA NTRS1954

Smoke Study of Nozzle Secondary Flows in a Low-speed Turbine

Still and motion pictures were made of boundary-layer and wake secondary-flow phenomena visualized by smoke. Two annular cascades of turbine nozzles were used, both designed for constant discharge angle but differing in blade shape and suction-surface velocity distribution. Flows were similar to those obtained with pressure and angle measurements at near-sonic airspeeds. Boundary-layer cross-channel and trailing-edge radial flows caused vortices and an accumulation of low-momentum air at the hub, which may affect flow in following blade rows. Motion of a downstream rotor blade row produced pulsations in trailing-edge radial flow. The motion-picture supplement may be obtained on loan from NACA Headquarters, Washington, D.C.

Kofskey, Milton G↗
NASA NTRS1953

Smoke Studies of Secondary Flows in Bends, Tandem Cascades, and High-turning Configurations

Flow-visualization studies, using smoke, were made of the secondary flows in rectangular bends, tandem cascades, and high-turning configurations. The roll-up of the wall boundary layer of a rectangular bend forms a passage vortex near the suction surface similar to that previously observed for cascades. The vortex so formed then shifts out into the main stream. Because of leading-edge effects, the boundary-layer flows in bends were found to be sufficiently different from the flows in blade rows to make direct application of bend results to blade rows inadvisable. Passage vortices are shown, in the tandem-cascade study, to resist turning with the main stream through which they pass and to disturb the flow in subsequent blade rows. This disturbance may explain in part the appreciable size of the losses sometimes attributed to secondary flows in turbomachines despite the fact that the energy involvement in vortex formation is slight. Tip-flow studies of high-turning blades with relative motion between blades and end wall indicated that if the relative sizes of the passage vortex forces, the tip clearance forces, and the blade-scraping effects are properly controlled, it may be possible to improve the blade-tip loading characteristics in turbomachine.

CASCADES↗
NASA NTRS1997

Atomic Oxygen Treatment Technique for Removal of Smoke Damage from Paintings

Soot deposits that can accumulate on surfaces of a painting during a fire can be difficult to clean from some types of paintings without damaging the underlying paint layers. A non-contact technique has been developed which can remove the soot by allowing a gas containing atomic oxygen to flow over the surface and chemically react with the soot to form carbon monoxide and carbon dioxide. The reaction is limited to the surface, so the underlying paint is not touched. The process can be controlled so that the cleaning can be stopped once the paint surface is reached. This paper describes the smoke exposure and cleaning of untreated canvas, acrylic gesso, and sections of an oil painting using this technique. The samples were characterized by optical microscopy and reflectance spectroscopy.

Rutledge, S. K.↗
NASA NTRS1960

Experimental Smoke and Electromagnetic Analog Study of Induced Flow Field About a Model Rotor in Steady Flight Within Ground Effect

Hovering and steady low-speed forward-flight tests were run on a 4-foot-diameter rotor at a ground height of 1 rotor radius. The two blades had a 2 to 1 taper ratio and were mounted in a see-saw hub. The solidity ratio was 0.05. Measurements were made of the rotor rpm, collective pitch, and forward-flight velocity. Smoke was introduced into the tip vortex and the resulting vortex pattern was photographed from two positions. Using the data obtained from these photographs, wire models of the tip vortex configurations were constructed and the distribution of the normal component of induced velocity at the blade feathering axis that is associated with these tip vortex configurations was experimentally determined at 450 increments in azimuth position from this electromagnetic analog. Three steady-state conditions were analyzed. The first was hovering flight; the second, a flight velocity just under the wake "tuck under" speed; and the third, a flight velocity just above this speed. These corresponded to advance ratios of 0, 0.022, and 0.030 (or ratios of forward velocity to calculated hovering induced velocity of approximately 0, 0.48, and 0.65), respectively, for the model test rotor. Cross sections of the wake at 450 intervals in azimuth angle as determined from the path of the tip vortex are presented graphically for all three cases. The nondimensional normal component of the induced velocity that is associated with the tip vortex as determined by an electromagnetic analog at 450 increments in azimuth position and at the blade feathering axis is presented graphically. It is shown that the mean value of this component of the induced velocity is appreciably less after tuck-under than before. It is concluded that this method yields results of engineering accuracy and is a very useful means of studying vortex fields.

Gray, Robin B.↗
NASA NTRS1998

Atomic Oxygen Treatment as a Method of Recovering Smoke Damaged Paintings

Smoke damage, as a result of a fire, can be difficult to remove from some types of painting media without causing swelling, leaching or pigment movement or removal. A non-contact technique has been developed which can remove soot from the surface of a painting by use of a gently flowing gas containing atomic oxygen. The atomic oxygen chemically reacts with the soot on the surface creating gasses such as carbon monoxide and carbon dioxide which can be removed through the use of an exhaust system. The reaction is limited to the surface so that the process can be timed to stop when the paint layer is reached. Atomic oxygen is a primary component of the low Earth orbital environment, but can be generated on Earth through various methods. This paper will discuss the results of atomic oxygen treatment of soot exposed acrylic gesso, ink on paper, and a varnished oil painting. Reflectance measurements were used to characterize the surfaces before and after treatment.

Rutledge, Sharon K.↗
NASA NTRS1998

Communication by Fire (and Smoke) Signals in the Kingdom of Judah

This paper examines the use of ancient fire and smoke signals for communication in the Kingdom of Judah. Historical and biblical references are cited that discuss this communication system. The current physical and political landscape of Israel precludes testing of hypotheses using traditional techniques. The use of a GIS is enlisted to overcome these obstacles and predict line-of-sight patterns that are conducive for a fire signal communication system. Final demonstration of this predictive model will incorporate state-of-the-art technology and in-field data acquisition to provide the sufficient accuracy that is required for proof-of-concept. This research will provide insight into the technical capability of the ancient Israelites for communication across a mountainous, desert environment.

Borowski, Oded↗
NASA NTRS2000

Noble Gas Incorporation into Graphitic "Smokes"

Graphitic smokes were condensed in noble gas atmospheres and analyzed for xenon. Results show trapping of amounts greater than found in chondritic carbonaceous residues. Sites saturated at low pressures. No mass-dependent fractionation was observed.

Olson, E. K.↗
NASA NTRS2002

Remote Sensing of Smoke, Land and Clouds from the NASA ER-2 during SAFARI 2000

The NASA ER-2 aircraft was deployed to southern Africa between August 17 and September 25, 2000 as part of the Southern Africa Regional Science Initiative (SAFARI) 2000. This aircraft carried a sophisticated array of multispectral scanners, multiangle spectroradiometers, a monostatic lidar, a gas correlation radiometer, upward and downward spectral flux radiometers, and two metric mapping cameras. These observations were obtained over a 3200 x 2800 km region of savanna, woody savanna, open shrubland, and grassland ecosystems throughout southern Africa, and were quite often coordinated with overflights by NASA's Terra and Landsat 7 satellites. The primary purpose of this sophisticated high altitude observing platform was to obtain independent observations of smoke, clouds, and land surfaces that could be used to check the validity of various remote sensing measurements derived by Earth-orbiting satellites. These include such things as the accuracy of the Moderate Resolution Imaging Spectro-radiometer (MODIS) cloud mask for distinguishing clouds and heavy aerosol from land and ocean surfaces, and Terra analyses of cloud optical and micro-physical properties, aerosol properties, leaf area index, vegetation index, fire occurrence, carbon monoxide, and surface radiation budget. In addition to coordination with Terra and Landsat 7 satellites, numerous flights were conducted over surface AERONET sites, flux towers in South Africa, Botswana, and Zambia, and in situ aircraft from the University of Washington, South Africa, and the United Kingdom.

King, Michael D.↗
NASA NTRS1961

The Smoke-Trail Method for Obtaining Detailed Measurements of the Vertical Wind Profile for Application to Missile-Dynamic-Response Problems

Detailed measurements of the vertical profile of the wind are urgently needed f o r studies of the response of rising missiles, but conventional wind-measuring systems cannot provide the accuracy and detail required over the necessary range of altitudes. A method is presented for obtaining a detailed, accurate profile over a large altitude range. The method utilizes photogrammetric measurement of successive positions of the t rail of an ascending rocket. Construction of a rocketborne smoke generator is discussed and the photography, film reading, and data-reduction procedures are described. The accuracy of the method i s examined and error equations are derived. Finally, some examples of wind profiles measured by this method are shown, and their implications for missile response are indicated.

Henry, Robert M.↗