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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Evidence from coupled (Sm-147)-(Nd-143) and (Sm-146)-(Nd-142) systematics for very early (4.5-Gyr) differentiation of the earth's mantle

Evidence for early differentiation of the earth's mantle is presented based on measurements of Nd-143/Nd-144 and Nd-142/Nd-144 ratios in an approximately 3.8 Gyr-old supracrustal rock from Isua, West Greenland. Coupled (Sm-146,147)-(Nd-142,143) systematics suggest that the fractionation of Sm/Nd took place 4.44-4.54 Gyr ago, due to extraction of a light rare earth element-enriched primordial crust.

Harper, Charles L., Jr.↗
NASA NTRS1927

Systematic investigation of Joukowsky wing sections

Ackeret began systematic polar measurements on Joukowsky wing sections, which were occasionally conducted in the wind tunnel. Under these conditions a considerable number of wing sections were tested during the last four years and the tests are now more or less concluded.

AIRFOILS - JOUKOWSKY - CHAR↗
NASA NTRS1926

Model tests with a systematic series of 27 wing sections at full Reynolds number

A systematic series of 27 wing sections, characterized by a small travel of the center or pressure, have been investigated at 20 atmospheres pressure in the variable density wind tunnel of the National Advisory Committee for Aeronautics. The results are consistent with each other, and indicate that for such "stable" sections a small effective camber, a small effective S-shape and a thickness of 8 to 12 per cent lead to good aerodynamic properties.

Munk, Max M↗
NASA NTRS1939

Free-Spinning Wind-Tunnel Tests of a Low-Wing Monoplane with Systematic Changes in Wings and Tails IV : Effect of Center-of-Gravity Location

Eight wings and three tails, covering a wide range of aerodynamic characteristics, were independently ballasted so as to be interchangeable with no change in mass distribution. For each of the 24 resulting wing-tail combinations, observations were made of the steady spin for four control settings and of recoveries for five control manipulations. The results are presented in the form of charts comparing the spin characteristics. The tests are part of a general investigation being made in the NACA free-spinning tunnel to determine the effects of systematic changes in wing and tail arrangement upon the steady-spin and the recovery characteristics of a conventional low-wing monoplane for various load distributions.

Seidman, Oscar↗
NASA NTRS1949

Investigation of a Systematic Group of NACA 1-Series Cowlings with and Without Spinners

Report presents the results of an investigation conducted in the Langley propeller research tunnel to study cowling-spinner combinations based on the NACA 1-series nose inlets and to obtain systematic design data for one family of approximately ellipsoidal spinners. In the main part of the investigation, 11 of the related spinners were tested in various combinations with 9 NACA open-nose cowlings, which were also tested without spinners. The effects of location and shape of the spinner, shape of the inner surface of the cowling lip, and operation of a propeller having approximately oval shanks were investigated briefly. In addition, a study was conducted to determine the correct procedure for extrapolating design conditions determined from the low-speed test data to the design conditions at the actual flight Mach number.

Nichols, Mark R↗
NASA NTRS1951

Systematic Two-Dimensional Cascade Tests of NACA 65-Series Compressor Blades at Low Speeds

The performance of NACA 65-series compressor blade section in cascade has been investigated systematically in a low-speed cascade tunnel. Porous test-section side walls and for high-pressure-rise conditions, porous flexible end walls were employed to establish conditions closely simulating two-dimensional flow. Blade sections of design lift coefficients from 0 to 2.7 were tested over the usable angle-of-attack range for various combinations of inlet-flow angle. A sufficient number of combinations were tested to permit interpolation and extrapolation of the data to all conditions within the usual range of application. The results of this investigation indicate a continuous variation of blade-section performance as the major cascade parameters, blade camber, inlet angle, and solidity were varied over the test range. Summary curves of the results have been prepared to enable compressor designers to select the proper blade camber and angle of attack when the compressor velocity diagram and desired solidity have been determined.

Herrig, L. Joseph↗
NASA NTRS1938

Systematic Airfoil Tests in the Large Wind Tunnel of the DVL

The present report is a description of systematic tests at maximum lift on airfoils with and without split flap and of profile drag at low lift. In order to obtain an opinion as to the suitability of the airfoils with flaps, the maximum-lift measurements were repeated on airfoils with split flaps. The profile drag at low lift was arrived at by direct weighing and momentum measurements and, since the profiles were of unusual depth, extended to large Reynolds numbers.

Doetsch, H↗
NASA NTRS1993

Rhenium-osmium isotope systematics of Group 2A and Group 4A iron meteorites

We are investigating the Re-Os isotope systematics of two groups of magmatic iron meteorites (2A, 4A) in an attempt to establish precise 'total rock' isochrons by the Re-Os system. The Re-187/Os-187 isotope system is recognized as a method by which the ages of iron meteorites can be directly determined and that can provide information on the timing of FeNi segregation and core formation in planetesimals. The Re-Os isotope system permits the direct absolute dating of the metal phase in iron meteorites. Indirect dating of iron meteorites has been achieved in the past through the Rb-Sr, K-Ar, and most recently, Sm-Nd for silicate inclusions, where present. Relative dating has been obtained directly by extensive studies of the short-lived system Pd-107/Ag-107 for the metal and sulfide phases and indirectly using I-129/Xe-129 in silicate and sulfide inclusions.

Creaser, R. A.↗
NASA NTRS1993

Constraints on the differentiation of the Earth from the coupled Sm-146,147-Nd-142,143 systematics

The coupled Sm-Nd systematics are a powerful (albeit analytically challenging) tool for investigating the geodynamic history of the Earth. We have previously reported evidence for a 33 ppm difference of an Isua sample relative to our terrestrial standard. Interpretation yields a formation age range for the depleted mantle (DM) source reservoir of 4.45-4.55 Ga. This is consistent with an epoch of LREE-enriched melt extraction from the mantle (proto-crust formation), soon after magma ocean freeze-up following the putative Moon forming giant impact.

Jacobsen, S. B.↗
NASA NTRS1993

Orthopyroxenes as recorders of diogenite petrogenesis: Major and minor element systematics

As a part of our research to better understand magmatic processes in the Eucrite Parent Body, we have initiated an ambitious program of study of major, minor and trace elements in orthopyroxene from diogenites. This paper reports preliminary results for major and minor elements in orthopyroxenes for a suite of 13 diogenites: Aioun El Atrouss, ALH 84001, ALH A 77256, EET 87530, Ellemeet, Garland, Ibbenburen, Johnstown, Manegoan, peckelsheim, Roda, Shalka, and Tatahouine. A companion paper by Shearer et al. reports new trace element data for ALH 84001, ALH A 77256, Ibbenburen, and Tatahouine. We have presently collected over 800 high quality pyroxene microprobe analyses for Si, Al, Ca, Na, Mn, Fe, Mg, Cr, and Ti. The chemical systematics observed for these orthopyroxenes reflect original magmatic mineral/melt partitioning plus later trapped liquid/mineral equilibration, subsolids, exsolution, and mineral/mineral metamorphic reactions. We have therefore avoided, at this point, any attempt to use statistical analysis to group (e.g. factor or cluster analysis) these orthopyroxenes chemically.

Papike, J. J.↗
NASA NTRS1993

U-Pb isotopic systematics of ferroan anorthosite 60025

Preliminary U-Pb isotopic data from separates of ferroan anorthosite 60025 confirm its antiquity at approximately 4.42 Ga. Three Pb-Pb isochron ages involving different sets of mineral separates vary by only 20 million years, but indicate derivation of the sets from isotopically distinct magma sources. If this anorthosite was a monomict cumulate product formed during the Moon's early primary differentiation stage, then residual liquids of crystallizing magmas were evolving isotopically, even at the cm-scale, over the duration of the crystallization period. Another explanation is that this sample is simply a polymict breccia and that the Pb isotopic results are a result of subsequent mechanical mixing of mineral assemblages from various cumulate piles formed coevally at approximately 4.42 Ga from isotopically distinct magma sources. In our ongoing search for early lunar Pb isotopic compositions, we have analyzed Apollo 16 anorthosites 67075 and 62337 and Apollo 17 high-Mg suite cumulates (troctolite 76535, norite 78235, and dunite 72415). The U-Pb isotopic systematics have been better behaved in the high-Mg suite rocks than in the anorthosites that have shown evidence of mineral assemblages of mixed parentage. Our aim in analyzing anorthosite 60025 was to avoid or minimize this problem as it had been considered essentially monomict, although recent work has shown that not only is 60025 polymict, but shows textual evidence of at least two episodes of deformation. Of five splits studied by James, Lindstrom and McGee, the four mineral splits appeared monomict, whereas the whole-rock split was considered polymict. Previous isotopic work indicate that this anorthosite was quite primitive, a claim that was apparently confirmed by the U-Pb isotopic age of 4.51 +/- .01 Ga on three plagioclase separates. However, a Sm-Nd internal isochron age of 4.44 +/- 0.02 Ga was determined using plagioclase, olivine, and mafic mineral separates, creating some doubt about the anorthosite's true age. It was pointed out that the use of slightly evolved initial Pb values (corresponding to a source-micron value of approximately 35) to correct the U-Pb data can result in an U-Pb age of 4.44 Ga. The need to resolve the age and isotopic nature of this anorthosite is paramount to furthering our understanding of processes of ferroan anorthosite formation as well as the magmatic history of the early Moon.

Premo, W. R.↗
NASA NTRS1992

Systematic Propulsion Optimization Tools (SPOT)

This paper describes a computer program written by senior-level Mechanical Engineering students at the University of Alabama in Huntsville which is capable of optimizing user-defined delivery systems for carrying payloads into orbit. The custom propulsion system is designed by the user through the input of configuration, payload, and orbital parameters. The primary advantages of the software, called Systematic Propulsion Optimization Tools (SPOT), are a user-friendly interface and a modular FORTRAN 77 code designed for ease of modification. The optimization of variables in an orbital delivery system is of critical concern in the propulsion environment. The mass of the overall system must be minimized within the maximum stress, force, and pressure constraints. SPOT utilizes the Design Optimization Tools (DOT) program for the optimization techniques. The SPOT program is divided into a main program and five modules: aerodynamic losses, orbital parameters, liquid engines, solid engines, and nozzles. The program is designed to be upgraded easily and expanded to meet specific user needs. A user's manual and a programmer's manual are currently being developed to facilitate implementation and modification.

Bower, Mark↗
NASA NTRS1994

Systematic comparison between the ground based automated Dobson of the Observatory of Haute-Provence and TOMS since 1983

The total ozone quantity has been obtained since September 1983 at O.H.P. using the conventional AD wavelength technique. An average of 180 measurements per year is obtained with the Dobson n deg 85. Each of these daily total quantities is in fact an average of at least 5 measurements. The preliminary comparison with TOMS data show good agreement. We discuss systematic daily and monthly comparisons.

Merienne, Marie-France↗
NASA NTRS1994

Mn-Cr isotopic systematics of Chainpur chondrules and bulk ordinary chondrites

We report on ongoing study of the Mn-Cr systematics of individual Chainpur (LL3.4) chondrules and compare the results to those for bulk ordinary chondrites. Twenty-eight chondrules were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by INAA. Twelve were chosen for SEM/EDX and high-precision Cr-isotopic studies on the basis of LL-chondrite-normalized Mn(LL), Sc(LL), (Mn/Fe)(LL), and (Sc/Fe)(LL) as well as their Mn/Cr ratios. Classification into textural types follows from SEM/EDX examination of interior surfaces.

Nyquist, L.↗
NASA NTRS1994

Rare gases systematics and mantle structure

The following points are emphasized: one of the most important ones is certainly the first set of experimental data on the solubility of noble gases in metal phases at intermediate pressures, since the core was certainly not formed at ultra high pressures, as emphasized by Ahrens and confirmed by trace elements systematics Wanke. The experimental data clearly show that the core can not be a major reservoir for terrestrial rare gases; the second point is a more elaborate reconsideration of the (40)K-(40)Ar budget of the Earth. This shows that (40)Ar contained in continental crust plus upper mantle plus atmosphere is at maximum half of the (40)Ar inventory of the whole earth. This implies the existence of a two layered mantle; the third point is the discovery by the Australian noble gases group of the existence of high (20)Ne/(22)Ne and low (21)Ne/(22)Ne isotopic ratios in Loihi seamount samples. This results which are different to the MORB ratios confirm the idea of a two layered model, but suggest the existence of a primordial solar type Ne reservoir. Several possibilities about the origin of this (20)Ne excess in the mantle will be discussed; The high (40)Ar/(36)Ar, (129)Xe/(130)Xe and (134) Xe/(130)Xe, (136)Xe/(130)Xe are confirmed by new data. The corresponding ratios for the lower mantle will be discussed. (40)Ar/(36)Ar ratios up to 6000 can be accepted and will not modify the general model of the mantle. They confirm the atmosphere chronology, about 85 percent of the atmosphere was formed in the first 50 My and 15 percent later on.

Allegre, C. J.↗
NASA NTRS1995

Systematic effects of randomness in radiative transfer

In this paper, the authors show how the variability of the water content in individual clouds, the complexity of individual cloud structure, and the lateral and vertical heterogeneity of the distribution of individual clouds can produce systematic effects in the inversion of intensity distributions and the inference of source functions and the vertical temperature profile. This is possibly very significant, even in simple applications of radiative transfer theory where multiple scattering is not very important, in light of the randomness in the water vapor content and geometry associated with the microphysics of clouds. A practical procedure is provided to quantify this effect and to obtain, in certain circumstances, an improved estimate of the vertical temperature profile.

Newman, William I.↗
NASA NTRS1996

A Systematic Solution Approach for Neutron Transport Problems in Diffuse Regimes

A systematic solution approach for the neutron transport equation, based on a least-squares finite-element discretization, is presented. This approach includes the theory for the existence and uniqueness of the analytical as well as of the discrete solution, bounds for the discretization error, and guidance for the development of an efficient multigrid solver for the resulting discrete problem. To guarantee the accuracy of the discrete solution for diffusive regimes, a scaling transformation is applied to the transport operator prior to the discretization. The key result is the proof of the V-ellipticity and continuity of the scaled least-squares bilinear form with constants that are independent of the total cross section and the absorption cross section. For a variety of least-squares finite-element discretizations this leads to error bounds that remain valid in diffusive regimes. Moreover, for problems in slab geometry a full multigrid solver is presented with V(1, 1)-cycle convergence rates approximately equal to 0.1, independent of the size of the total cross section and the absorption cross section.

Manteuffel, T. A.↗