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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1948

Surface-pressure Distributions on a Systematic Group of NACA 1-series Cowlings with and Without Spinners

A method for calculating the flow fields of axially symmetric bodies from their pressure distributions is reported in NACA RM No. L8I17. In order to facilitate application of this method to the important case of the cowling-spinner combination, for use in the design of propellers, the present paper presents static-pressure distributions on the tops of 79 high-critical-speed NACA 1-series cowling-spinner combinations over wide ranges of inlet-velocity ratio at angles of attack of 0 degrees, 2 degrees, 4 degrees, and 6 degrees. Static-pressure distributions around the nose sections of several cowlings are given in greater detail to aid in estimating the pressures near the stagnation points and to show the effect of changes in the internal lip shape. The effects of the operation of a typical propeller on the surface pressures on the cowling are shown for one configuration. The pressure distributions over the nine NACA 1-series nose inlets used as the basic components of these combinations are also presented ro supplement the existing open-nose-cowling data of NACA ACR No. L5F30a which are applicable to the case of the rotating cowling.

Boswinkle, Robert W JR↗
NASA NTRS1994

Program For Systematic Documentation Of Tasks

Task Analysis Report Generation Tool (TARGET) computer program is graphical-interface software tool used to capture procedural knowledge and translate knowledge into hierarchical report. Designed to help programmer document expert's task, enabling programmer to build expert-system computer program that helps others perform task. Flexibility key element of design and of knowledge-acquisition session. Easy to use and tailored to accommodate users ranging from novice to experienced builder of expert systems. Written in C language.

Ortiz, Christopher John↗
NASA NTRS1993

Systematic chemical variations in large 3AB iron meteorites: Clues to core crystallization

Analysis of numerous individual iron meteorites have shown that fractional crystallization of iron cores result in variations in chemical concentration of the solid core which span several orders of magnitude. The magnitude and direction of the resulting spatial gradients in the core can provide clues to the physical nature of the core crystallization process. We have analyzed suites of samples from three large 3AB irons (Cape York, 58t; Chupaderos, 24t; Morito, 10t) in order to estimate local chemical gradients. Initial results for the concentrations of Ge, Pd, Pt (Massey group), Ir, Au, As, Co, Os, and Rh (Dalhouse group), and P (Arizona group) show significant ranges among the Cape York and Chupaderos samples and marginally significant ranges among the Morito samples. Measurements of Au, Ir, Co, Ni, Cu, Ga, As, W, Re (from UCLA) and Ni and Co (Arizona group) are in progress. We find a spatial Ir gradient in Chupaderos with a magnitude similar to the one reported for Agpalilik (Cape York iron) by Esbensen et al.

Haack, H.↗
NASA NTRS1993

Orthopyroxenes as recorders of diogenite petrogenesis: Trace element systematics

Eucrite, howardite, and diogenite members of the achondrites are considered, by many, to be genetically related. Therefore, each provide a piece of the puzzle for reconstructing magmatic processes on the eucrite parent body (EPB). The relationship between eucrites and diogenites can be viewed within the context of two distinctly different models: (1) fractional crystallization; and (2) partial melting. In fractional crystallization models, eucrites and diogenites represent a complementary continuum of planetary fractional crystallization products in which the diogenites represent crystal accumulations during the crystallization of eucritic magmas at shallow to deep levels in the EPB. Alternatively, experimental studies may be interpreted as indicating eucrites represent peritectic partial melts of a primitive, chondritic EPB mantle. Within this type of model, the diogenites are also generally considered to be cumulates; however, their petrogenetic relationship to the eucrites is less clear. Sack et al. proposed that the olivine diogenites represent residua from the partial melting events that produced eucritic liquids. Initial trace element studies of orthopyroxene (OPX) are consistent with this model. However, this trace element modeling of the olivine diogenites is nonunique. As a further test of these models, we did the following three things: (1) analyzed OPX from cumulate diogenites to compare with the olibine diogenite data; (2) improved ion microprobe analytical techniques for the analysis of elements critical to our interpretations; and (3) selected more relevant Kd's for OPX-eucritic melt.

Shearer, C. K.↗
NASA NTRS1993

The Sm-Nd systematics of silicate inclusions in iron meteorites: Results from Caddo (IAB)

The timing of events leading to the formation of silicate-rich and metal-rich regions in planetesimals remains an important problem in the study of planetary formation and differentiation in the early solar system. The IAB irons are especially important as they are considered to represent a magmatic differentiation series. Iron meteorites present a particular challenge for chronological studies, due to the relative paucity of phases serving as hosts for radioactive parent-daughter nuclides. Recent work using the Re-Os system, following on the pioneering work by Herr et al. and Luck and Allegre, appears promising, but investigators up to now have concentrated on whole rock isochrons. Silicate clasts enclosed within iron meteorites can provide information about the chronology and thermal history of irons. Extensive work on Rb-Sr, K-Ar, and I-Xe has been reported on silicate inclusions in iron meteorites. We report the initial results from our Sm-Nd study of an inclusion with the Caddo IAB iron, the first Sm-Nd isotopic study of a silicate clast embedded within an iron meteorite. Our results include measurements of the standard long-lived Sm-147/Nd-143 (tau = 152 AE) system, as well as the shorter-lived SM-146/Nd-142 (tau = 0.149 AE) system, which has been shown to be very useful in deciphering the history of the early solar system. The Caddo silicate clast was described by Palme et al., who kindly provided us with a major part of the inclusion. The inclusion is coarse-grained consisting predominantly of olivine, clinopyroxene, and plagioclase, with lesser amounts of orthopyroxene, Fe-Ni metal, sulfide, and phosphate. The relatively large grain size (up to 3 mm) and 120 degree grain boundaries suggest extensive metamorphism at high temperatures. Based on study of a thin section, there is evidence for metal invading along grain boundaries in some regions of the inclusion, suggesting that the Fe-Ni metal was molten when the silicate clast was incorporated. Metamorphic recrystallization may have occurred during this event.

Stewart, Brian W.↗
NASA NTRS1993

The U-Th-Pb, Sm-Nd, and Ar-Ar isotopic systematics of lunar meteorite Yamato-793169

U-Th-Pb, Sm-Nd, and (Ar-40)-(Ar-39) isotopic studies were performed on Yamato (Y)-793169, an unbrecciated diabasic lunar meteorite whose chemical composition is close to low Ti(LT) and very low-Ti (VLT) mare basalts. The isotopic data indicate that the meteorite was formed earlier than 3.9 Ga from a source with low U/Pb and high Sm/Nd and was distributed by a thermal event at 751 Ma. due to the small sample size (104 mg), a plagioclase crystal and glass grains were handpicked for Ar analysis, leaving four fractions for the U-Th-Pb and Sm-Nd studies; a fine-grained fraction (less than 63 microns; Fine) and three medium-grained fractions (63-150 microns). Medium-grained fractions were divided by density; a heavy fraction (rho greater than 3.3) consisting mainly of pyroxene (PX1), a lighter fraction (rho less than 2.8) consisting of plagioclase (PL), and a middle density fraction (predominantly pyroxene; PX2). The fractions were washed with acetone and alcohol, and then leached in 0.01 HBr and 0.1N HBr in order to remove any terrestrial Pb contamination. Analysis of the HBr leaches revealed that this meteorite was heavily contaminated with terrestrial Pb during its residence in Antarctic ice.

Torigoye, Noriko↗
NASA NTRS1993

Rhenium-osmium isotope systematics of ordinary chondrites and iron meteorites

Using negative thermal ionization mass spectrometry, Re and Os abundances were determined by isotope dilution and Os-187/Os-186 measured in 11 ordinary chondrites, and also in 1 IIB and 3 IIIB irons. In addition, Os-186/Os-188 and Os-189/Os-188 ratios were precisely determined for 3 unspiked ordinary chondrites as a means of constraining the intensity of any neutron irradiation these meteorites may have experienced.

Walker, R. J.↗
NASA NTRS1994

Systematic stratospheric observations on the Antarctic continent at Dumont d'Urville

Results of different routine measurements performed in Dumont d'Urville (66 deg S, 140 deg E) since 1988 are presented. They include the seasonal variation of total ozone and NO2 as measured by a SAOZ UV-Visible spectrometer, Polar Stratospheric Cloud observations by a backscatter lidar and more recently, vertical ozone profiles by ECC sondes and ozone and aerosols stratospheric profiles by a DIAL lidar. The particular results of 1991 in relation with the volcanic events of Mount Pinatubo and Mount Hudson, and the position of the polar vortex over Dumont d'Urville are discussed.

Godin, S.↗
NASA NTRS1994

Mn-Cr isotopic systematics of individual Chainpur chondrules

Twenty-eight chondrules separated from Chainpur (LL3.4) were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by Instrumental Neutron Activation Analysis (INAA). Six, weighting 0.6-1.5 mg each, were chosen for Scanning Electron Microscopy (SEM)/Energy Dispersive X-ray (EDX) and high-precision Ce-isotopic studies. LL-chondrite-normalized (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) were found to be useful in categorizing them. Five chondrules (CH-16, -17, -18, -23, and -28) were in the range 0.5 less than (Mn/Fe)(sub LL) less than 1. 4 and 0.5 less than (Sc/Fe)(sub LL) less than 1.4. The sixth (CH-25) had (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) ratios of 0.40 and 8.1, respectively, and was enriched in the refractory lithophile elements Sc and Hf and the refractory siderophile element Ir by 2.7 and 4.4x LL abundances respectively. SEM/EDX of exterior surfaces of the chondrules showed they consisted of varying proportions of low- and high-Ca pyroxenes, olivine, glass, kamacite/taenite, and Fe-sulfides. Chromium-53/chromium-52 for the six chondrules and bulk Chainpur (WR) are presented. Chromium-54/chromium-52 is close to terrestrial and does not correlate with Mn/Cr. We provisionally ignore the possibility of initial Cr isotopic heterogeneities among the chondrules. Omitting both the CH-25 and WR data, a linear regression gives initial (Mn-53/Mn-55)(sub I) = 8 +/- 4 x 10(exp -6), corresponding to chondrule formation at Delta(t)(sub LEW) = -9 +/- 4 Ma prior to igneous crystallization of the LEW 86010 angrite. If initial (Mn-53/Mn-55)(sub 0) in the solar system were as high as approximately 4.4 x 10(exp -5) when Allende CAI formed, our data suggest Chainpur chondrules formed approximately 9 Ma later, in qualitative agreement with 'late' I-Xe formation ages for most Chainpur chondrules.

Nyquist, L.↗
NASA NTRS1994

The Pasamonte unequilibrated eucrite: Pyroxene REE systematic and major-, minor-, and trace-element zoning

We are evaluating the trace-element concentrations in the pyroxenes of Pasamonte. Pasamonte is a characteristic member of the main group eucrites, and has recently been redescribed as a polymict eucrite. Our Pasamonte sample contained eucritic clasts with textures ranging from subophitic to moderately coarse-grained. This study concentrates on pyroxenes from an unequilibrated, coarse-grained eucrite clast. Major-, minor-, and trace-element analyses were measured for zoned pyroxenes in the eucritic clast of Pasamonte. The major- and minor-element zoning traverses were measured using the JEOL 733 electron probe with an Oxford-Link imaging/analysis system. Complemenatry trace elements were then measured for the core and rim of each of the grains by SIMS. The trace elements analyzed consisted of eight REE, Sr, Y, and Zr. These analyses were performed on a Cameca 4f ion probe. The results of the CI chondrite normalized (average CI trace-element analyses for several grains and the major- and minor-element zoning patterns from a single pyroxene grain are given. The Eu abundance in the cores of the pyroxenes represents the detection limit and therefore the (-Eu) anomaly is a minimum. Major- and minor-element patterns are typical for igneous zoning. Pyroxene cores are Mg enriched, whereas the rims are enriched in Fe and Ca. Also, Ti and Mn are found to increase, while Cr and Al generally decrease in core-to-rim traverses. The cores of the pyroxenes are more depleted in the Rare Earth Elements (REE) than the rims. Using the minor- and trace-element concentrations of bulk Pasamonte and the minor- and trace-element concentrations from the cores of the pyroxenes in Pasamonte measured in this study, we calculated partition coefficients between pyroxene and melt. This calculation assumes that bulk Pasamonte is representative of a melt composition.

Pun, A.↗
NASA NTRS1995

An atlas of H-alpha-emitting regions in M33: A systematic search for SS433 star candidates

We report finding charts and accurate positions for 432 compact H-alpha emitting regions in the Local Group galaxy M 33 (NGC 598), in an effort to isolate candidates for an SS433-like stellar system. The objects were extracted from narrow band images, centered in the rest-frame H-alpha (lambda 6563 A) and in the red continuum at 6100 A. The atlas is complete down to V approximately equal to 20 and includes 279 compact HII regions and 153 line emitting point-like sources. The point-like sources undoubtedly include a variety of objects: very small HII regions, early type stars with intense stellar winds, and Wolf-Rayet stars, but should also contain objects with the characteristics of SS433. This extensive survey of compact H-alpha regions in M 33 is a first step towards the identification of peculiar stellar systems like SS433 in external galaxies.

Calzetti, Daniela↗
NASA NTRS1997

A Systematic Study of Explosions in Core Collapse Supernovae

This report covers the research conducted from September 1996 to August 1997 (eighteen months into the three year grant). We have obtained a number of significant findings based on the on the work that we have conducted under this grant during the past year. As we stated in our original proposal the work has focused on multi-dimensional models of the convective epoch in core collapse supernovae. During the past year we have developed a large number of models of the convective epoch in 2-D under two levels of neutrino transport approximation and we are currently working on 3-D models. In the following pages will endeavor to give brief descriptions of our results.

Swesty, F. Douglas↗
NASA NTRS1996

Systematic Underestimation of Earthquake Magnitudes from Large Intracontinental Reverse Faults: Historical Ruptures Break Across Segment Boundaries

Because most large-magnitude earthquakes along reverse faults have such irregular and complicated rupture patterns, reverse-fault segments defined on the basis of geometry alone may not be very useful for estimating sizes of future seismic sources. Most modern large ruptures of historical earthquakes generated by intracontinental reverse faults have involved geometrically complex rupture patterns. Ruptures across surficial discontinuities and complexities such as stepovers and cross-faults are common. Specifically, segment boundaries defined on the basis of discontinuities in surficial fault traces, pronounced changes in the geomorphology along strike, or the intersection of active faults commonly have not proven to be major impediments to rupture. Assuming that the seismic rupture will initiate and terminate at adjacent major geometric irregularities will commonly lead to underestimation of magnitudes of future large earthquakes.

Rubin, C. M.↗
NASA NTRS1959

A Systematic Kernel Function Procedure for Determining Aerodynamic Forces on Oscillating or Steady Finite Wings at Subsonic Speeds

Details are given of a numerical solution of the integral equation which relates oscillatory or steady lift and downwash distributions in subsonic flow. The procedure has been programmed for the IBM 704 electronic data processing machine and yields the pressure distribution and some of its integrated properties for a given Mach number and frequency and for several modes of oscillation in from 3 to 4 minutes, results of several applications are presented.

Watkins, Charles E.↗
NASA NTRS1959

Basic Pressure Measurements at Transonic Speeds on a Thin 45 deg Sweptback Highly Tapered Wing With Systematic Spanwise Twist Variations

Pressure distributions obtained in the Langley 8-foot transonic pressure tunnel on a thin, highly tapered, twisted, 45 deg sweptback wing in combination with a body are presented. The wing has a linear span-wise twist variation from 0 deg at 10 percent of the semispan to 6 deg at the tip. The tip is at a lower angle of attack than the root. Tests were made at stagnation pressures of 1.0 and 0.5 atmosphere, at Mach numbers from 0.800 to 1.200, and at angles of attack from -4 to 12 deg.

Mugler, John P., Jr.↗
NASA NTRS1959

Basic Pressure Measurements at Transonic Speeds on a Thin 45 deg Sweptback Highly Tapered Wing with Systematic Spanwise Twist Variations

Pressure distributions obtained in the Langley 8-foot transonic pressure tunnel on a thin, highly tapered, twisted, 450 sweptback wing in combination with a body are presented. The wing has a cubic spanwise twist variation from 0 deg. at 10 percent of the semispan to 60 at the tip. The tip is at a lower angle of attack than the root. Tests were made at stagnation pressures of 1.0 and 0.5 atmosphere, at Mach numbers from 0 0.800 to 1.200, and at angles of attack from -4 deg. to 20 deg.

Mugler, John P., Jr.↗
NASA NTRS1959

Basic Pressure Measurements at Transonic Speeds on a Thin 45 deg Sweptback highly Tapered Wing With Systematic Spanwise Twist Variations

Pressure distributions obtained in the Langley 8-foot transonic pressure tunnel on a thin highly tapered twisted 45 deg sweptback wing-body combination are presented. The wing has a quadratic spanwise twist variation from 0 deg at 10 percent of the semispan to 6 deg at the tip. The tip is at a lower angle of attack than the root. Tests were made at stagnation pressures of both 0.5 and 1.0 atmosphere at Mach numbers from 0.800 to 1.200 through an angle-of-attack range from -4 deg to 20 deg.

Mugler, John P., Jr.↗
NASA NTRS1958

Basic Pressure Measurements at Transonic Speeds on a Thin 45 deg Sweptback Highly Tapered Wing with Systematic Spanwise Twist Variations

Pressure distributions are presented for a thin highly tapered untwisted 45 deg sweptback wing in combination with a body. These tests were made in the Langley 8-foot transonic pressure tunnel at both 1.0 and 0.5 atmosphere stagnation pressures at Mach numbers from 0.800 to 1.200 through an angle-of-attack range of -4 deg to 12 deg.

Mugler, John P., Jr.↗