Effect of acceleration on the burning rate of composite propellants.
Metallized and nonmetallized composite solid propellant burning rates, analyzing effects of acceleration, noting agglomeration and nonnormal conditions
GAS DYNAMICS↗
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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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The Sharps chondrite - New evidence on the origin of chondrules and chondrites.
Sharps chondrite chemical, petrographic and mineralogical studies suggesting formation from complex and repetitious high temperature events and agglomeration processes
Fredriksson, K.↗
Mechanism of operation of the TFE-bonded gas-diffusion electrode
Mathematical analytical model predicts the performance of an electrode as a function of certain measurable physical characteristics. Concept assumes the catalyst particles form porous electrically conductive agglomerates which are completely flooded with electrolyte.
Giner, J.↗
The structure of hydrophobic gas diffusion electrodes
Teflon-bonded gas diffusion electrode flooded agglomerate model, determining porosity, surface area, IR drop, etc
Giner, J.↗
Photographic study of solid propellants burning in an acceleration environment
Photographic study of acceleration and pressure effects on Al agglomerates and combustion processes on solid propellant surface, describing pit growth by combustion model
Baker, K. L.↗
Plasma calcining of pigment particles for thermal control coatings
Method utilizes an RF excited plasma to surface deactivate thermally stable powders at high temperatures. Utilization of this plasma heat treatment at high temperatures can be carried out without grain growth, calcination, or agglomeration.
Farley, E. P.↗
A study of the dry heat resistance of naturally occurring organisms widely dispersed on a surface
Although Bacillus subtilis var. niger is the standard test organism for NASA planetary quarantine sterilization studies, it was found that some naturally occurring soil organisms are more heat resistant. The separation of these organisms from soil particles is described. Experiments are discussed which were designed to show that the heat resistance is a natural characteristic of the organisms, rather than a condition induced by the clumping effect of agglomerated particles and organisms.
Garst, D. M.↗
Volcanic petrology and geologic history of Northeast Bank, Southern California Borderland.
Basaltic rocks, hyaloclastites, and fossil fragments incorporated in volcanic material, dredged from the flanks of Northeast Bank on the Southern California Borderland, show trace element abundances typical of eastern Pacific basin alkali basalts but enriched (880 ppm) Ba. The fossil fragments, incorporated in breccia, hyaloclastite, and agglomerate, include a fauna which lived in less than 50 m of water, as well as forms from the intertidal zone. Bathymetry of the bank and the depth range of the dredged zone indicate that there has been at least 300 or as much as 500 m subsidence since the volcanism which incorporated the fauna in volcanic material. Isostatic adjustments due to crustal load of the bank can account for this subsidence.
Hawkins, J. W.↗
Parent-body models for the formation of iron meteorites.
The iron meteorites appear to have formed by both igneous and non-igneous processes in asteroid-sized parent bodies. Evidence regarding the IIIA-IIIB irons (the most common iron meteorite group) favors their having originated as a central core, which experienced fractional crystallization during solidification. A reevaluation of available data does not confirm earlier reports of variable cooling rates within group IIIA. Members of group IA-IB contain chondritic silicates, have short I-Xe formation intervals and do not show evidence of fractional crystallization. They appear to have formed nonigneously by inhomogeneous agglomeration and accretion of solar nebular condensates.
Wasson, J. T.↗
The comet-meteor stream complex.
The genetic relationship between short-period comets and meteor streams is investigated. It is shown that mechanisms exist for the radial and the longitudinal focussing of particles in meteor streams with characteristic time scales of agglomeration significantly smaller than those of any of the known dispersive processes. Consequently, it is claimed that meteor streams may not merely form a sink for short-period comets but may also form a source. A likely origin for the volatiles observed in such comets is suggested. It is finally stressed that this reciprocity in the genetic relationship between short-period comets and meteor streams should form an important consideration in any attempt at accounting for the observed population of short-period comets.
Mendis, D. A.↗
Characterization of fines from the Apollo 16 site
We describe the characteristics of Apollo 16 fines samples 61281,8; 65701,13; 66031,6; 67701,26; and 67712,16 observed microscopically during the course of size and magnetic separations. Sample 67712,16 is unique in that almost all grains are rounded and no glass welded aggregates are present. All samples except 67712,16 contained about 0.5 wt.% of metal fragments 45 microns or more in diameter including occasional spheres and large single crystals. Some of this metal showed rust spots. Moessbauer spectra showed all the samples to be high in olivine compared to samples from other Apollo sites and to vary significantly in modal composition from each other. The fine grained Fe metal content and the excess absorption area near zero velocity in the Moessbauer spectra both vary with particle size and regolith maturity in the way one would predict from our model of Fe metal reduction and agglomeration during glass aggregate formation.
Housley, R. M.↗
Comets and the formation of planets
Morphological study of the physical and dynamical processes of planet formation, with emphasis on the role of comet nuclei. A consistent model proposes the formation of comets and planets in preplanetary rings of the residual solar nebula, with subsequent ejection, chiefly by Jupiter, of the comets to Oort's (1950) sphere. Physically, dynamically, or statistically evaluated items include: (1) the total number and mass of comets in Oort's cloud; (2) reevaluation of the diameters and masses of comet nuclei; (3) the processes of nucleation from gravitational and 'Boltzmann' instabilities of gaseous media to agglomerations of particulate matter; and (4) the statistical-dynamical conditions and time scales of orbital interaction of comets with the planets and the consequences of disintegration.
Opik, E. J.↗
Variations in the infrared brightness temperature of Saturn's rings
After adjusting for the decreased Sun-Saturn distance and adjusting all measurements to B ring values only, it is shown that the temperature variations are not as large as was thought. Various models of the multilayer agglomerate of particles of Saturn's rings are evaluated. It is recommended that the difference between the 11 and 20 micron brightness temperatures should be explained by a satisfactory model.
Murphy, R. E.↗
Thermal conductivity of comets
The thermal conductivity of two comet models is calculated. Both models assume the comets to be heterogeneous in composition. One model considers the comet to have a nucleus of water-ice mixed with basaltic and meteoritic material in the form of dust and agglomerated particles surrounded by a layer of water-frost. The second model assumes the frost and water-ice layers have sublimated, leaving a porous structure to some depth composed of solid basaltic and meteoritic material with residual gases. K values are calculated as a function of depth, density, temperature and porosity.
Kumar, G. N.↗
Aerosols at 20 kilometers altitude
Stratospheric aerosols were collected at the 20 km altitude zone by direct impaction on 0.2mm palladium wires in view of the previously observed minimum in particle size frequency distribution between 0.1 and 0.2 microns. Since no minimum in size distribution around 0.2 microns was found, it is concluded that previous equipment was inefficient in collection in this range. Concentration results suggest that low particle concentrations result from small particles agglomerating to form larger ones. Since no indentations were found on the wires used in this experiment, and since there were no differences in the number of particles found on oil-coated surfaces vs uncoated surfaces, the particles in the stratosphere must be liquid, liquid coated, or a slurry.
Ferry, G. V.↗
On the origin of comets
Physico-chemical processes leading to the dynamic formation and physical evolution of comets are reviewed in relationship to the various theories that propose solar origins, protoplanetary origins, planetary origins and interstellar origins. Evidence points to the origins of comets by the growth and agglomeration of small particles from gas and dust at very low temperatures at undetermined regions in space.
Mendis, A.↗
Calcium-aluminum-rich inclusions in the Allende meteorite - Evidence for a liquid origin
We have made a detailed examination of the mineralogy, textures, and assemblages of six calcium-aluminum-rich inclusions (CAI) in the Allende meteorite. They can be classified into four types - hibonite-bearing, fassaite- and olivine-bearing, feldspathoid-bearing and fassaite-bearing CAI that are hibonite and olivine free. Examples of each type appear to have crystallized from a liquid rather than by agglomeration of solid nebular condensates. Some lines of evidence for a liquid origin are the presence of spherical and ovoid shapes and rims containing minerals that are more refractory than minerals inside the inclusion. Thermodynamic calculations and comparisons with liquidus phase diagrams indicate that the CAI could have been produced by direct condensation to metastable subcooled liquids that subsequently crystallized or by remelting of an equilibrium high-temperature condensate by impact. The diopside rims in some hibonite-bearing CAI and the paucity of metal in fassaite-olivine-bearing CAI are more consistent with direct condensation of a liquid.
Blander, M.↗
Nebular condensation of moderately volatile elements and their abundances in ordinary chondrites
Two models accounting for the concentrations of moderately volatile elements in ordinary chondrites are discussed. The first relies on an apparent correlation between ordinary chondrite/type-I carbonaceous chondrite abundance ratios and ideal solution-condensation temperatures of such elements as Sn, Cu, Li, Na, and Mn to construct a model in which volatiles are lost as gases before nebular condensation or as finely-divided solids that are incompletely agglomerated, and the condensation/agglomeration efficiency declines as a function of time. The second theory largely discounts this gas-dust diffraction effect and instead proposed condensation on matrix and volatization from chondules and coarse metal grains as mechanisms explaining the apparent existence of three distinct classes of volatile-element abundance in ordinary chondrites.
Wai, C. M.↗