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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Volatiles in interplanetary dust particles and aerogels

Volatiles measured in 25 interplanetary dust particles (IDPs) are a mixture of both indigenous materials and contaminants associated with the collection and processing of the ODPs prior to analysis. Most IDPs have been collected in the stratosphere using a silicone oil/freon mixture (20:1 ratio) coated on collector plates. Studies have shown that silicone oil, freon and hexane residues remain with the ODPs, despite attempts to clean the IDPs. Analysis of the IDPs with the LMMS-technique produces spectra with a mixture of indigeneous and contaminants components. The contamination signal can be identified and removed; however, the contamination signal may obscure some of the indigeneous component's signal. Employing spectra stripping techniques, the indigenous volatile constituents associated with the IDPs can be identified. Volatiles are similar to those measured in CI or CM carbonaceous chondrites. Collection of IDPs in low-Earth orbit utilizing a Cosmic Dust Collection Facility attached to Space Station Freedom has been proposed. The low-density material aerogel has been proposed as a collection substrate for IDPs. Our studies have concentrated on identifying volatile contaminants that are associated with aerogel. We have found that solvents used for the preparation of aerogel remain in aerogel and methods must be developed for removing the entrapped solvents before aerogels can be used for an IDP collection substrate.

Gibson, E. K., Jr.↗
NASA NTRS1993

Role of grain size and particle velocity distribution in secondary electron emission in space plasmas

By virtue of being generally immersed in a plasma environment, cosmic dust is necessarily electrically charged. The fact that secondary emission plays an important role in determining the equilibrium grain potential has long been recognized, but the fact that the grain size plays a crucial role in this equilibrium potential, when secondary emission is important, has not been widely appreciated. Using both conducting and insulating spherical grains of various sizes and also both Maxwellian and generalized Lorentzian plasmas (which are believed to represent certain space plasmas), we have made a detailed study of this problem. In general, we find that the secondary emission yield delta increases with decreasing size and becomes very large for grains whose dimensions are comparable to the primary electron penetration depth, such as in the case of the very small grains observed at comet Halley and inferred in the interstellar medium. Moreover, we observed that delta is larger for insulators and equilibrium potentials are generally more positive when the plasma has a broad non-Maxwellian tail. Interestingly, we find that for thermal energies that are expected in several cosmic regions, grains of different sizes can have opposite charge, the smaller ones being positive while the larger ones are negative. This may have important consequences for grain accretion in polydisperse dusty space plasmas.

Chow, V. W.↗
NASA NTRS1994

A proposition for the classification of carbonaceous chondritic micrometeorites

Classification of interplanetary dust particles (IDP's) should be unambiguous and, if possible, provide an opportunity to interrelate these ultrafine IDP's with the matrices of undifferentiated meteorites. I prefer a scheme of chemical groupings and petrologic classes that is based on primary IDP properties that can be determined without prejudice by individual investigators. For IDP's of 2-50 microns these properties are bulk elemental chemistry, morphology, shape, and optical properties. The two major chemical groups are readily determined by energy dispersive spectroscopic analysis using the scanning or analytical electron microscope. Refinement of chondritic IDP classification is possible using the dominant mineral species, e.g. olivine, pyroxene, and layer silicates, and is readily inferred from FTIR, and automated chemical analysis. Petrographic analysis of phyllosilicate-rich IDP's will identify smectite-rich and serpentine-rich particles. Chondritic IDP's are also classified according to morphology, viz., CP and CF IDP's are aggregate particles that differ significantly in porosity, while the dense CS IDP's have a smooth surface. The CP IDP's are characterized by an anhydrous silicate mineralogy, but small amounts of layer silicates may be present. Distinction between the CP and CF IDP's is somewhat ambiguous, but the unique CP IDP's are fluffy, or porous, ultrafine-grained aggregates. The CP IDP's, which may contain silicate whiskers, are the most carbon-rich extraterrestrial material presently known. The CF IDP's are much less porous that CP IDP's. Using particle type definitions, CP IDP's in the NASA JSC Cosmic Dust Catalogs are approx. 15 percent of all IDP's that include nonchondritic spheres. Most aggregate particles are of the CF type.

Rietmeijer, Frans J. M.↗
NASA NTRS1963

INTERPLANETARY DUST

Interplanetary dust studies are summarized, noting ground-based and space experimental results concerning particle concentration and influx rate

EXTRATERRESTRIAL MATTER↗
NASA NTRS1960

Explorer Satellite Electronics

A discussion is presented of the design restrictions and the philosophy which enabled the Explorer satellites to be first during the IGY to reveal the presence of a belt of intense cosmic radiation encircling the earth's equator. In addition, an indication of the amount and momentum of cosmic dust in the solar system was obtained from the Explorers. Methods used to obtain reliability in the transducing and communications system are described, together with interpretations of space-environment information as deduced from the narrow-band telemetry.

Eyraud, J. P.↗
NASA NTRS1966

Mariner-Mars science subsystem

Mariner-Mars science subsystem - cosmic ray telescope, cosmic dust detector, trapped radiation detector, ionization chamber, plasma probe, magnetometer, and data processing

MARINER IV SPACE PROBE↗
NASA NTRS1968

Lunar Explorer 35

Lunar Explorer 35 measurements of solar wind, interplanetary and lunar magnetic fields, cosmic dust, energetic particles, and electromagnetic properties of lunar surface

Ness, N. F.↗
NASA NTRS1972

Analysis of microsize particulates

Unique methods for analyzing individual particles ranging in size from 0.01 to 1000 micrometers have been developed for investigation of nature of cosmic dust. Methods are applicable to particulate aerosols and contaminants characteristically encountered in studies of air pollution and in experiments designed to abate pollution.

Blanchard, M. B.↗
NASA NTRS1971

Methods of analyzing microsize particulate aerosols and contaminants.

Methods for analyzing atmospheric aerosols and particulate contaminants from natural and industrial sources are briefly described. Their development was spurred by interest in cosmic dust investigations. These methods make it possible to analyze individual particles ranging in size from 0.01 to 1000 microns for elemental and mineralogical content. The described methods include transmission electron microscopy, scanning electron microscopy, electron probe microanalysis, X-ray diffraction, optical mineralogy, and density measurement.

Blanchard, M. B.↗
NASA NTRS1973

Noctilucent cloud sampling by a multi-experiment payload.

Two multi-experiment payloads were launched into noctilucent cloud displays above Kiruna, Sweden, on the nights of July 31 and Aug. 1, 1971. The payloads were part of the continuing Pandora II cosmic dust collection series and included: (1) Pandora 2 dust collection with in-flight shadowing photoelectric polarimeters to measure scattered light at 4100 and 5400 A, a plasma detector and an ion probe, and piezoelectric microphones. These payloads attempted to investigate noctilucent clouds by four simultaneous and independent techniques. The photometric data indicate that the first payload passed through a cloud, while the second payload did not. These results are confirmed by the particle collection experiment which indicates a higher collection on the first payload. Analysis of the chemical composition of the collected particles indicates an unusual amount of high atomic number elements.

Hallgren, D. S.↗
NASA NTRS1973

Note on the 1972 Giacobinid meteor shower.

It is shown that the 1972 Giacobinid meteor shower was extremely weak with a peak activity of two to three visual meteors per hour. Only two meteor spectra were obtained from the 17 slitless spectrograph systems operated by the Langley Research Center. The largely unexpected, essentially null results of the 1972 Giacobinid meteor shower observations are indicative of the present limited understanding and predictability of cosmic dust storms.

Harvey, G. A.↗
NASA NTRS1975

A composition analyzer for microparticles using a spark ion source

Iron microparticles were fired onto a capacitor-type microparticle detector which responded to an impact with a spark discharge. Ion currents were extracted from the spark and analyzed in a time-of-flight mass spectrometer. The mass spectra showed the element of both detector and particle materials. The total extracted ion currents was typically 10A within a period of 100ns, indicating very efficient vaporization of the particle and ionization of the vapor. Potential applications include research on cosmic dust, atmospheric aerosols and cloud droplets, particles ejected by rocket or jet engines, by machining processes, or by nuclear bomb explosions.

Auer, S. O.↗
NASA NTRS1975

Composition analyzer for microparticles using a spark ion source

Iron microparticles were fired onto a capacitor-type microparticle detector which responded to an impact with a spark discharge. Ion currents were extracted from the spark and analyzed in a time-of-flight mass spectrometer. The mass spectra showed the elements of both detector and particle materials. The total extracted ion current was typically 10 A within a period of 100 nsec, indicating very efficient vaporization of the particle and ionization of the vapor. Potential applications include research on cosmic dust, atmospheric aerosols and cloud droplets, particles ejected by rocket or jet engines, by machining processes or by nuclear bomb explosions.

Auer, S.↗
NASA NTRS1975

Micrometeorites and solar flare particles in and out of the ecliptic

Using crystals grown into vugs from oriented lunar rocks as directional detectors of cosmic dust particles and solar flare nuclei, I have measured the angular distribution of the flux of micrometeoroids of mass 30 attograms to 80 femtograms. Hypervelocity impact craters of diameter 500 A to 10 microns and tracks from solar flare nuclei of energy 100 keV/amu to 20 MeV/amu were observed in crystals from rock 71055 facing lunar south and in crystals from rock 74255 facing lunar east. I have found that dust grains both in ecliptic orbits and in orbits inclined to the ecliptic have virtually identical mass-frequency distributions and similar shapes. I have evaluated the micrometeoroid fluxes after determining the exposure ages of the individual vug crystals by measuring the solar flare track density gradients in each crystal. The flux of particles of mass greater than 4 femtograms confined to the ecliptic is in good agreement with satellite measurements, suggesting that the micrometeoroid flux has been relatively constant over the past 35,000 yr. The flux of particles producing microcraters on a lunar surface facing south is lower than the ecliptic flux by a factor of about 7.

Hutcheon, I. D.↗
NASA NTRS1976

Hollow lunar spherules and microcratering

Craters were generated by micrometer-size, thin-walled hollow glass spheres impacting glass and stainless steel targets to determine morphological features distinguishing craters formed by hollow spheres from those formed by solid projectiles. The craters formed in both targets differed from those formed by solid spherical projectiles in that the central pit is an annular rather than a cup-shaped depression. The existence of an annular crater morphology on a surface exposed to cosmic dust would indicate the presence of thin-walled hollow spherules. Penetrations of thin-walled hollow glass beads by high velocity, solid, micrometer-size spheres are characterized by inward and outward flowing lips showing asymmetries dependent on the angle of impact.

Vedder, J. F.↗