Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Fragmentation”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Rotor burst protection program: Statistics on aircraft gas turbine engine rotor failures that occurred in US commercial aviation during 1975

Statistics on gas turbine rotor failures that have occurred in U.S. commercial aviation during 1975 are presented. The compiled data were analyzed to establish: (1) The incidence of rotor failures and the number of contained and uncontained rotor bursts; (2) The distribution of rotor bursts with respect to engine rotor component; i.e., fan, compressor or turbine; (3) The type of rotor fragment (disk, rim or blade) typically generated at burst; (4) The cause of failure; (5) The type of engines involved; and (6) The flight condition at the time of failure.

Delucia, R. A.↗
NASA NTRS1978

What is the fate of interplanetary dust

The following general picture of the interplanetary dust is presented: (1) size distribution; (2) spatial distribution; (3) composition; (4) dynamics; and (5) origin. The solar probe mission provides a unique opportunity to study the evolution of the interplanetary dust and its eventual destruction near the sun. Two destructive processes (fragmentation and vaporization) of interplanetary dust are discussed.

Hanner, M. S.↗
NASA NTRS1977

The Viking X ray fluorescence experiment - Analytical methods and early results

Ten samples of the Martian regolith have been analyzed by the Viking lander X ray fluorescence spectrometers. Because of high-stability electronics, inclusion of calibration targets, and special data encoding within the instruments the quality of the analyses performed on Mars is closely equivalent to that attainable with the same instruments operated in the laboratory. Determination of absolute elemental concentrations requires gain drift adjustments, subtraction of background components, and use of a mathematical response model with adjustable parameters set by prelaunch measurements on selected rock standards. Bulk fines at both Viking landing sites are quite similar in composition, implying that a chemically and mineralogically homogeneous regolith covers much of the surface of the planet. Important differences between samples include a higher sulfur content in what appear to be duricrust fragments than in fines and a lower iron content in fines taken from beneath large rocks than those taken from unprotected surface material. Further extensive reduction of these data will allow more precise and more accurate analytical numbers to be determined and thus a more comprehensive understanding of elemental trends between samples.

Clark, B. C., III↗
NASA NTRS1977

Dissociative excitation of H2, HD, and D2 by electron impact

Time-of-flight techniques have been used to investigate the electron-impact dissociation of H2, HD, and D2 in order to determine the effect of isotopic mass variation in the target molecule on the dissociative excitation process. At incident electron energies near 100 eV, the time-of-flight spectrum produced from each molecule consists of atoms in the metastable 2s state and in high-lying long-lived Rydberg levels. The individual time-of-flight distributions, kinetic-energy spectra, and relative differential cross sections for these two species resulting from each molecule have been measured. The kinetic-energy spectrum of the Rydberg atoms produced from dissociative excitation of H2 was notably dissimilar in shape from the corresponding distributions produced from HD and D2. Also the 2s and Rydberg production cross sections differed between the three molecules. In the dissociation of the heteronuclear HD molecule, the ratio of fast H(2s) atoms to D(2s) atoms was about 1 to 1, while the same ratio comparing the Rydberg atoms was nearly 2 to 1. These differences indicate the influence of the mass variation on the position of the Franck-Condon region in the production of 2s atoms and on the competition between autoionization and dissociation in the formation of Rydberg fragments.

Carnahan, B. L.↗
NASA NTRS1977

Why is a minor planet minor

A hypothesis based on the accretion model of planet formation is proposed which can explain why minor planets could not grow into full-sized planets. Temperature and impact-velocity conditions for bouncing, accumulation, and fragmentation of planetesimals are evaluated for silicate and iron planetesimals at the heliocentric distances of Mercury, Venus, earth, Mars, and the asteroid belt. The results indicate that the low-temperature environment of the asteroids very likely hampered their growth into ironlike planetesimals, which in turn inhibited the accumulation of silicate planetesimals. It is concluded that the brittleness of iron at temperatures below 200 to 250 K is the primary reason why minor planets are 'minor' and could not grow to full size.

Matsui, T.↗
NASA NTRS1976

The protostellar origin of interstellar grains

A semiquantitative description of the origin of interstellar grains in a protostellar environment is given. Grains grow in the protostellar collapse phase and can be expelled by radiation pressure from stars of at least about 5 solar masses. A convective shell of grains forms in which shattering produces a power-law spectrum of fragments. A bimodal distribution of grain sizes, peaking at approximately 0.1 and 0.01 micron results. The effects of protostellar winds and rotation are considered.

Silk, J.↗
NASA NTRS1977

Simulation and display of macromolecular complexes

In association with an investigation of the interaction of proteins with DNA and RNA, an interactive computer program for building, manipulating, and displaying macromolecular complexes has been designed. The system provides perspective, planar, and stereoscopic views on the computer terminal display, as well as views for standard and nonstandard observer locations. The molecule or its parts may be rotated and/or translated in any direction; bond connections may be added or removed by the viewer. Molecular fragments may be juxtaposed in such a way that given bonds are aligned, and given planes and points coincide. Another subroutine provides for the duplication of a given unit such as a DNA or amino-acid base.

Nir, S.↗
NASA NTRS1977

Photodecomposition of chloromethanes adsorbed on silica surfaces

Irradiation of CCl4, CFCl3, and CF2Cl2 in the presence of C2H6 in vessels containing silica sand or fused quartz tubing results in the formation of chlorine-containing products. The formation of these compounds occurs at wavelengths extending up to approximately 400 nm, that is, at wavelengths well beyond the absorption threshold of the chloromethanes in the gas phase. It is suggested that CCl4 adsorbed on silica surfaces photodissociates to yield CCl3 and CCl2 species. The poor material balance obtained in these experiments indicates that several of the chlorine-containing fragments are strongly adsorbed on the surface. At a CCl4 pressure of 13 Pa (0.1 torr), photolysis with 366 nm light in the presence of sand results in the decomposition of one molecule for every 10,000 photons striking the surface. Under otherwise identical conditions, the photon-induced breadkdown of CFCl3 and CF2Cl2 is respectively only 10% or 3% as efficient.

Ausloos, P.↗
NASA NTRS1978

The cosmic ray record in the San Juan Capistrano meteorite

Measurements of cosmic ray track densities, rare gas concentrations, and radioisotope activities on the same sample of the San Juan Capistrano (SJC) meteorite (March 15, 1973) were combined in order to obtain a consistent picture of the irradiation history of the meteorite. The latter was recovered in two fragments weighing 50.5 and 5.5 g, respectively, which were then sampled according to the objectives set forward. The preatmospheric size of SJC and the depth occupied by the sample in the preatmospheric body were determined within narrow limits. In addition, the study compared estimates of the cosmic ray exposure age as determined by various techniques and evaluated the amount of ablation undergone when SJC penetrated the earth's atmosphere.

Finkel, R. C.↗
NASA NTRS1977

Basalts from Mare Crisium

The stratified core sample returned from Mare Crisium by the Luna 24 unmanned space probe is composed primarily of a variety of subophitic to ophitic basalt with very low contents of TiO2 and MgO. This consists of clinopyroxene, calcic plagioclase, olivine, and minor amounts of silica, chromite, ulvoespinel, ilmenite, troilite, apatite, and Fe-metal. Granular metabasalts have the same bulk composition, but mineral phases exhibit less compositional variation. Fine-grained impact melts have similar compositions and are apparently derived from these basalts. It is concluded that the basalts, which are chemically distinct from the very-low-titanium basalts found elsewhere on the moon, represent the local surface flows of Mare Crisium. Sparse fragments of an olivine vitrophyre that is low in TiO2 but high in MgO and approaches the composition of the Apollo 15 green glasses may be derived from patches of dark mantling materials 20 km from the landing site.

Ryder, G.↗
NASA NTRS1977

Some opportunities in teleoperated mining

Processes involved in remote control mining (fragmentation, material handling, ground and environmental control) are discussed with reference to longwall shear mining, the method which affords the greatest potential for the use of teleoperated systems. The breakup and haulage procedures are outlined, with attention to environmental control subsystems, i.e., noise and dust abatement. A description of a four-legged chock, attached to a section of a face conveyor and operated remotely, is presented.

Palowitch, E. R.↗
NASA NTRS1977

Origin of asteroids and the missing planet

Consideration is given to Ovenden's (1972) theory concerning the existence of a planet of 90 earth masses which existed from the beginning of the solar system and then disappeared 16 million years ago, leaving only asteroids. His model for secular perturbations is reviewed along with the principle of least interaction action (1972, 1973, 1975) on which the model is based. It is suggested that the structure of the asteroid belt and the origin of meteorites are associated with the vanished planet. A figure of 0.001 earth masses is proposed as a close estimate of the mass of the asteroidal belt. The hypothesis that the planet was removed through an explosion is discussed, noting the possible origin of asteroids in such a manner. Various effects of the explosion are postulated, including the direct impact of fragments on the earth, their impact on the sun and its decreased radiation, and the direct radiation of the explosion. A model for the disappearance of the planet by ejection in a gravitational encounter with a passing mass is also described.

Opik, E. J.↗
NASA NTRS1978

Enriched gas in clusters and the dynamics of galaxies and clusters Implications for theories of galaxy formation

Recent observations of the rotation of elliptical galaxies and of X-ray clusters are cited in developing a simple model for the formation of elliptical and spiral galaxies; the model provides for continuous galaxy formation from redshift values of about 100 onwards. In particular, it is argued that a fundamental alteration in the manner in which cosmic material fragmented to form stellar objects took place at a redshift value of approximately five. This change of regime may be employed to explain the formation of Population I disks, the origin of hot intracluster gas, the galaxy luminosity function, and the mass-to-light ratio stratification of galaxies.

Binney, J.↗
NASA NTRS1978

On the detection of newly created CN radicals in comets

A description is presented of laboratory measurements concerning the amount and the distribution of energy released into newly formed radicals by the photodissociation process. The experimental method used involved flash photolysis of the parent compound followed by laser induced fluorescence detection of the CN fragment. This method allowed the detection of individual rotational lines and, thereby, a monitoring of the relative populations of the vibrational-rotational levels of the CN ground state. The results obtained in the investigation suggest the possibility of observing emission lines in cometary spectra from newly formed CN radicals. Calculations show that it is feasible with present observational techniques to detect photochemically excited lines in the 0-0 band of the violet system.

Donn, B.↗
NASA NTRS1978

Physics of the primitive solar accretion disk

The theory of viscous accretion disks developed by Lynden-Bell and Pringle (1974) has been applied to the evolution of the primitive solar nebula. The additional physical input needed to determine the structure of the disk is described. A series of calculations was carried out using a steady flow approximation to explore the effects on the disk properties of variations in such parameters as the angular momentum and accretion rate of the infalling material from a collapsing interstellar cloud fragment. The more detailed evolutionary calculations involved five cases with various combinations of parameters. It was concluded that the late stages of evolution of the disks would be dominated by the effects of mass loss from the expansion of a hot disk corona into space, and the effects of this were included in the evolutionary calculations. A new theory of comet formation is formulated upon these results. The most important result is the conclusion that the primitive solar accretion disk was repeatedly unstable against axisymmetric perturbations, in which rings would form and collapse upon themselves, with the subsequent formation of giant gaseous protoplanets.

Cameron, A. G. W.↗
NASA NTRS1978

Possible fossil H2O liquid-ice interfaces in the Martian crust

The extensive chaotic and fretted terrains in the equatorial regions of Mars are explained on the basis of the vertical distribution of H2O liquid and ice which once existed in the crust. This account assumes that below the permafrost containing water ice, there was a second zone in which liquid water resided for at least a time. Diagenetic alteration and cementation characterized the material in the subpermafrost zone; above, pristine fragmented material with various ice concentrations was found. Later, the ice-laden zone was stripped away by a number of erosional processes, exposing the former ice-liquid water interface.

Soderblom, L. A.↗
NASA NTRS1978

Petrogenesis of melt rocks, Manicouagan impact structure, Quebec

It is suggested, on the basis of previous theoretical studies of shock waves, that the Manicouagan melt formed in 1 or 2 s in a 5-km-radius hemisphere near the point of impact. The melt and the less shocked debris surrounding it flowed downward and outward for a few minutes until the melt formed a lining of a 5- to 8-km deep, 15- to 22-km-radius cavity. Extremely turbulent flow thoroughly homogenized the melt and promoted the incorporation and progressive digestion of debris that had been finely fragmented (but not melted) to grain sizes of less than one mm by the passage of the shock waves. The equilibration of clasts and melt, plagioclase nucleation, and readjustment of the crater floor are discussed.

Simonds, C. H.↗
NASA NTRS1978

The lunar highland melt-rock suite

Size can be used as a criterion to select 18 large (larger than 1 cm) samples from among 148 melt-rock fragments of all sizes. This selection provides a suite of large samples which represent the important chemical variants among highland melt rocks; each large sample has enough material for a number of sample-destructive studies, as well as for future reference. Cluster analysis of the total data base of 148 highland melt rocks shows six distinct groups: anorthosite, gabbroic anorthosite, anorthositic gabbro ('highland basalt'), low K Fra Mauro, intermediate-K Fra Mauro, and high-K. Large samples are available for four of the melt-rock groups (gabbroic anorthosite, anorthositic gabbro, low-K Fra Mauro, and intermediate-K Fra Mauro). This sample selection reveals two subgroups of anorthositic gabbro (one anorthite-poor with negative Eu anomaly and one anorthite-rich without Eu anomaly). There is a sharp distinction between those Apollo 16 melt rocks and glasses which have both been classified as 'gabbroic anorthosite'.

Vaniman, D. T.↗