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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Multi-element spherical shell generation

A nozzle assembly in a multi-element spherical shell generation system includes first and second side-by-side spaced apart nozzles and a web portion extending between and connecting the nozzles. The first nozzle has an inner orifice adapted to discharge a first filler material and an outer annular orifice separated from and defined in concentric relation about the inner orifice and adapted to discharge a first shell material. The second nozzle has an inner orifice adapted to discharge a second filler material and an outer annular orifice separated from and defined in concentric relation about the inner orifice and adapted to discharge a second shell material. A multi-element spherical shell can be formed through employment of the nozzle assembly by merger with one another after discharge from the outer orifices of the nozzles of a pair of adjacent annular streams of liquid or molten shell wall material of different compositions and encapsulation by the mixed shell wall materials of a common encapsulated core fluids also simultaneously discharged by the inner orifices nozzles. On the other hand, the pair of encapsulating streams of shell wall material can be of the same materials which merge together and encapsulate core fluids of different compositions which will merge together after discharge from the nozzles.

Morrison, Andrew D.↗
NASA NTRS1990

A counterrotating core in the merger remnant candidate NGC 3656 (ARP 155)

A study is presented of the internal velocity structure of NGC 3656, a galaxy with several morphological signatures of being in an advanced merger stage. Rotation curves obtained for two slit-position angles show that the inner 1 kpc rotates around an axis roughly perpendicular to the rotation axis in the main body of the galaxy. There are indications that the galaxy is not dynamically relaxed at intermediate radii. The presence of an orthorotating core in a dynamically young galaxy with a dust disk and a shell system provides strong evidence linking kinematically peculiar cores to mergers. However, relating the various merger signatures in this system is not straightforward, as the core and the dust disk rotate around axes perpendicular to each other, which may indicate an independent origin.

Balcells, Marc↗
NASA NTRS1988

The dual nature of the supernova remnant G351.2 + 0.1

The Galactic SNR G351.2 + 0.1 has been imaged at frequencies of 1.4, 5, and 15 GHz. The images reveal a source composed of two distinct components: a broken elongated shell measuring 4 x 6 arcmin and a central core about 15 arcsec in diameter. The two components are spectrally distinct. The shell has a nonthermal spectrum (alpha = -0.4) typical for Galactic SNRs, while the central core has an inverted spectrum (alpha = +0.27). The central core may be an analog of the Crab Nebula (a synchrotron nebula powered by a pulsar), but if so it is not typical of such objects.

Becker, R. H.↗
NASA NTRS1982

On the nature of upsilon Sagittarii

An explanation for the nature and evolution of the extremely hydrogen deficient binary Upsilon Sagittarii which is consistent with all observational and theoretical facts. First, the system goes through a Case B mass exchange in which most of the hydrogen rich envelope of a massive primary (5 to 14 solar masses) is lost. The remaining envelope still contains about 50% hydrogen (by number), but is now of negligible mass, so that the star evolves like a pure helium star. If its mass is between 1 and 2 solar masses the star reaches low surface temperatures and becomes a supergiant before the onset of carbon burning. This star (the original primary) then fills its Roche lobe a second time, spilling its now helium rich envelope over onto the secondary (Case BB mass exchange). It is argued that Upsilon Sagrittarii is in this state at the present time, and that the visible star is an evolved helium star of about 1 solar mass with a degenerate carbon-oxygen core and a helium burning shell which provides the high luminosity.

Schoenberner, D.↗
NASA NTRS1983

On the nature of Upsilon Sagittarii

An explanation for the nature and evolution of the extremely hydrogen deficient binary Upsilon Sagittarii which is consistent with all observational and theoretical facts. First, the system goes through a Case B mass exchange in which most of the hydrogen rich envelope of a massive primary (5 to 14 solar masses) is lost. The remaining envelope still contains about 50 percent hydrogen (by number), but is now of negligible mass, so that the star evolves like a pure helium star. If its mass is between 1 and 2 solar masses the star reaches low surface temperatures and becomes a supergiant before the onset of carbon burning. This star (the original primary) then fills its Roche lobe a second time,spilling its now helium rich envelope over onto the secondary (Case BB mass exchange). It is argued that Upsilon Sagittarii is in this state at the present time, and that the visible star is an evolved helium star of about 1 solar mass with a degenerate carbon-oxygen core and a helium burning shell which provides the high luminosity. Previously announced in Star as N26117

Schoenberner, D.↗
NASA NTRS1984

Platinum group nuggets in deep sea sediments

The existence of iron meteor oblation spheres in deep sea sediments was known for over a century. These spheres generally were believed to be composed of either pure magnetite and wustite or an oxide shell surrounding a NiFe metal core. A large number of 300 micron to 600 micron spheres found were pure oxide spheres, usually containing a solitary 10 micron platinum group nugget (pgn) composed almost entirely of group VIII metals. Twelve PGN's were analyzed and most had chondritic abundances with some depletions that correlate with element volatility. PGN formation by oxidation of a molten metal sphere entering the atmosphere cannot occur if the oxygen abundance in the atmosphere is less than half of its present value. The first appearance of PGN's in the geological record should mark when, in the Earth's history, oxygen rose to this level.

Brownlee, D. E.↗
NASA NTRS1991

The dynamics of dense and dilute clusters of drops evaporating in large, coherent vortices

The behavior of evaporating clusters of drops embedded into large, coherent vortices is described using a formulation which is valid for both dense and dilute clusters. Drops and gas interact both dynamically and thermodynamically. Dynamic coupling occurs through a force on the drops due to drag resulting from a slip velocity between the two phases. The net interaction force on the gas with drops is due to a source thrust from evaporation plus drag on each drop. The drag coefficient accounts for blowing from the drop surface. Thermodynamic coupling is a result of drop heating and evaporation. Limitations due to drop proximity on heating and evaporation are taken into account. The vortical motion of the drops in the cluster results in the formation of a core region devoid of drops at the center of the vortex, and a shell region containing the drops and surrounding the inner core. Results are presented showing the dependence of the evaporation time, the final to initial volume ratio and the final to initial shell thickness ratio upon the initial air/fuel mass ratio and as a function of the initial tangential velocities, upon the initial Stokes number, initial drop radius and initial outer cluster radius. Differences in behavior between and control parameters of dense and dilute clusters are pointed out by these new results. It is found that for dense clusters the final to initial volume ratio and final to initial shell thickness scale with the initial Stokes number, a new result which must be validated experimentally.

Bellan, J.↗
NASA NTRS1988

Interaction between high-velocity pulsar in CTB80 and an infrared emission shell

During a survey of infrared emission detected by IRAS from shock-heated dust associated with Galactic SNRs, a roughly 1 deg diameter supernova remnant shell centered 30 arcmin east of SNR CTB80's core was discovered. The pulsar's projected location inside this infrared emission shell, together with similar distance and age estimates, suggest that both the shell and pulsar were produced by the same supernova event. It is proposed that the interaction between the pulsar's energetic particle emission and the shell's compressed interstellar magnetic field can explain CTB80's remarkable radio structure, and the implications of such pulsar/SNR interactions are discussed.

Fesen, Robert A.↗
NASA NTRS1982

Hydrodynamic performance of an annular liquid jet: Production of spherical shells

An annular jet flow of liquid surrounding a flow of gas at its core is extremely unstable. Axisymmetric oscillations arise spontaneously, and grow with such rapidity along the axial dimension that a pinch-off of the liquid and an encapsulation of the core gas occurs within as few as four jet diameters. The shells which result thereby may be described as thick-wall bubbles, for which van der Waals forces are unimportant. A description is given of the fluid dynamic processes by which the shells are formed, and of means for preserving and promoting the geometrical of the product. The forming of metallic shells is mentioned.

Kendall, J. M.↗
NASA NTRS1988

Macrofossil extinction patterns at Bay of Biscay Cretaceous-Tertiary boundary sections

Researchers examined several K-T boundary cores at Deep Sea Drilling Project (DSDP) core repositories to document biostratigraphic ranges of inoceramid shell fragments and prisms. As in land-based sections, prisms in the deep sea cores disappear well before the K-T boundary. Ammonites show a very different extinction pattern than do the inoceramids. A minimum of seven ammonite species have been collected from the last meter of Cretaceous strata in the Bay of Biscay basin. In three of the sections there is no marked drop in either species numbers or abundance prior to the K-T boundary Cretaceous strata; at the Zumaya section, however, both species richness and abundance drop in the last 20 m of the Cretaceous, with only a single ammonite specimen recovered to date from the uppermost 12 m of Cretaceous strata in this section. Researchers conclude that inoceramid bivalves and ammonites showed two different times and patterns of extinction, at least in the Bay of Biscay region. The inoceramids disappeared gradually during the Early Maestrichtian, and survived only into the earliest Late Maestrichtian. Ammonites, on the other hand, maintained relatively high species richness throughout the Maestrichtian, and then disappeared suddenly, either coincident with, or immediately before the microfossil extinction event marking the very end of the Cretaceous.

Ward, Peter D.↗
NASA NTRS1989

Polar wander of an ice shell on Europa

The present consideration of a hypothesized ice shell around Europa, which is decoupled from the silicate core by a liquid water layer and possesses a spatially varying thermal equilibrium thickness profile, proceeds through the development of equations for variations in the inertia tensor of a body when second-harmonic-degree topography is added to the crustal base. Attention is given to a realistic model in which the shell and ocean are assumed to undergo reorientations as a single entity independently of the core, but subject to viscous dissipation within the shell. Shell friction is in this case noted to preclude polar wander, unless a low conductivity regolith increases the near-surface temperature by a few tens of degrees C; the ice beneath the regolith would then behave viscously on the time-scale of polar wander.

Ojakangas, Gregory W.↗
NASA NTRS1991

Tiltrotor research aircraft composite blade repairs: Lessons learned

The XV-15, N703NA Tiltrotor Research Aircraft located at the NASA Ames Research Center, Moffett Field, California, currently uses a set of composite rotor blades of complex shape known as the advanced technology blades (ATBs). The main structural element of the blades is a D-spar constructed of unidirectional, angled fiberglass/graphite, with the aft fairing portion of the blades constructed of a fiberglass cross-ply skin bonded to a Nomex honeycomb core. The blade tip is a removable laminate shell that fits over the outboard section of the spar structure, which contains a cavity to retain balance weights. Two types of tip shells are used for research. One is highly twisted (more than a conventional helicopter blade) and has a hollow core constructed of a thin Nomex-honeycomb-and-fiberglass-skin sandwich; the other is untwisted with a solid Nomex honeycomb core and a fiberglass cross-ply skin. During initial flight testing of the blades, a number of problems in the composite structure were encountered. These problems included debonding between the fiberglass skin and the honeycomb core, failure of the honeycomb core, failures in fiberglass splices, cracks in fiberglass blocks, misalignment of mated composite parts, and failures of retention of metal fasteners. Substantial time was spent in identifying and repairing these problems. Discussed here are the types of problems encountered, the inspection procedures used to identify each problem, the repairs performed on the damaged or flawed areas, the level of criticality of the problems, and the monitoring of repaired areas. It is hoped that this discussion will help designers, analysts, and experimenters in the future as the use of composites becomes more prevalent.

Espinosa, Paul S.↗
NASA NTRS1992

Tiltrotor Research Aircraft composite blade repairs - Lessons learned

The XV-15, N703NA Tiltrotor Research Aircraft located at the NASA Ames Research Center, Moffett Field, California, currently uses a set of composite rotor blades of complex shape known as the advanced technology blades (ATBs). The main structural element of the blades is a D-spar constructed of unidirectional, angled fiberglass/graphite, with the aft fairing portion of the blades constructed of a fiberglass cross-ply skin bonded to a Nomex honeycomb core. The blade tip is a removable laminate shell that fits over the outboard section of the spar structure, which contains a cavity to retain balance weights. Two types of tip shells are used for research. One is highly twisted (more than a conventional helicopter blade) and has a hollow core constructed of a thin Nomex-honeycomb-and-fiberglass-skin sandwich; the other is untwisted with a solid Nomex honeycomb core and a fiberglass cross-ply skin. During initial flight testing of the blades, a number of problems in the composite structure were encountered. These problems included debonding between the fiberglass skin and the honeycomb core, failure of the honeycomb core, failures in fiberglass splices, cracks in fiberglass blocks, misalignment of mated composite parts, and failures of retention of metal fasteners. Substantial time was spent in identifying and repairing these problems. Discussed here are the types of problems encountered, the inspection procedures used to identify each problem, the repairs performed on the damaged or flawed areas, the level of criticality of the problems, and the monitoring of repaired areas. It is hoped that this discussion will help designers, analysts, and experimenters in the future as the use of composites becomes more prevalent.

Espinosa, Paul S.↗
NASA NTRS1986

Fabrication of cooled radial turbine rotor

A design and fabrication program was conducted to evaluate a unique concept for constructing a cooled, high temperature radial turbine rotor. This concept, called split blade fabrication was developed as an alternative to internal ceramic coring. In this technique, the internal cooling cavity is created without flow dividers or any other detail by a solid (and therefore stronger) ceramic plate which can be more firmly anchored within the casting shell mold than can conventional detailed ceramic cores. Casting is conducted in the conventional manner, except that the finished product, instead of having finished internal cooling passages, is now a split blade. The internal details of the blade are created separately together with a carrier sheet. The inserts are superalloy. Both are produced by essentially the same software such that they are a net fit. The carrier assemblies are loaded into the split blade and the edges sealed by welding. The entire wheel is Hot Isostatic Pressed (HIPed), braze bonding the internal details to the inside of the blades. During this program, two wheels were successfully produced by the split blade fabrication technique.

Hammer, A. N.↗
NASA NTRS1994

Oxgen-burning hydrodynamics. 1: Steady shell burning

With new hydrodynamic techniques, the relatively fast evolutionary stages of a star prior to core collapse may be explicitly computed in two spatial dimensions, with a treatment of the microphysics (e.g., nuclear reactions, equation of state, neutrino cooling) which is comparable to typical one-dimensional simulations. The nature of shell oxygen burning in a massive star, prior to core collapse, is used as a first example; it is of particular interest because it is (1) the region in which Ni-56 will be produced by the supernova shock, (2) the region of the 'mass cut', which will separate the collapsed core from the ejected mantle, (3) the site of much of the explosive nucleosynthesis, and (4) a suggested source of symmetry breaking to drive mixing instabilities which were observed in SN 1987A. The nature of the shell burning affects the size of the core which will collapse. The method is illustrated on this test case, and the character of the convection is examined.

Arnett, David↗
NASA NTRS1976

K I 7699 A emission from the Betelgeuse shell

A map of the circumstellar gas shell around Betelgeuse is presented from observations of the fluorescent emission in the K I 7699 A resonance line. The observations obtained at 3 sec and 5 sec from the star indicate approximate spherical symmetry in the 10 km/s expanding shell responsible for the blueshifted sharp cores seen in strong resonance and low excitation lines. Calculations show that the density of neutral K atoms is approximately constant between 3 sec and 5 sec from the star. The emission profiles in the west show a second, higher velocity, component at 5 sec from the star.

Bernat, A. P.↗