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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Direct numerical simulation of turbulent plane Couette flow

Turbulent plane Couette flow was numerically simulated at a Reynolds number (U(sub w)h/nu) of 6000, where U(sub w) is the relative wall speed and h is half the channel-height. Unlike in Poiseuille flow, where the mean shear rate changes its sign at the centerline, the sign of mean shear rate in plane Couette flow remains the same across the whole channel. This difference is expected to yield several differences between the two flows, especially in the core region. The most significant and dramatic difference observed was the existence of large-scale structures in the core region of the plane Couette flow. The large eddies are extremely long in the flow direction and fill the entire channel (i.e., their vertical extent is 2h). The large-scale structures have the largest contribution from the wavenumber (k(sub x)h,k(sub z)h) = (0, plus or minus 1.5), corresponding to a wavelength lambda(sub z)/h is approximately equal to 4. The secondary motion associated with the k(sub x)h = 0 mode consists of the large-scale vortices. The large eddies contribute about 30 percent of turbulent kinetic energy.

Lee, Moon Joo↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Impacts: Observations and Experiments

The title in this section include: 1) Impactites of the Haughton Impact Structure, Devon Island, Nunavut, Canada; 2) Geochemical Characteristics of Impactites from the Yaxcopoil-1 ICDP Drill Core, Chicxulub Impact Structure, Mexico; 3) Investigation of the Ries Impact Crater Based upon Old and New Geophysical Data and Numerical Modeling; 4) Potential of Radar Imaging and Sounding Methods in Mapping Heavily Eroded Impact Craters: Mapping Some Structural Elements of the Hico Crater, TX; 5) From Simple to Complex Craters: The Mechanics of Late-time Crater Adjustments; 6) Impact Structures: What Does Crater Diameter Mean? 7) Early-Time Temperature Evolution of the Impact Flash and Beyond; 8) Probing Impact-Generated Vapor Plumes; 9) Non-Ballistic Vapor-Driven Ejecta; 10) Depth and Diameter of Transient Craters; 11) A Plausibility of Z-Model; 12) Experiments with Explosives and Ordnance Disposal Devices for the Simulation of Specific Processes During Shallow-Marine Impacts; 13) Collisional Fragmentation of Rotating Bodies.

Source record↗
NASA NTRS1983

Progress in propulsion system/airframe structural integration

Attention is given to the improvements in mathematical modeling, and the emerging role of computer-related technology, in airframe structural technology advancements related to the engine/airframe integration requirements of such recent designs as the 747 airliner's JT9D turbofan engine nacelle. Also noted are investigation results concerning propulsion system flight loads and their influence on thrust-specific fuel consumption deterioration, which has been addressed through the development of the novel structural concept of the 'load-carrying core cowl' engine nacelle structure. Analytical studies on integrated system vibration include low frequency, nonsynchronous vibration analyses of large, high bypass turbofan engines that have been conducted by means of three-dimensional integrated finite element models.

White, J. L.↗
NASA NTRS1986

Electronic/Hydraulic Level Gage

System for checking levelness of machines and structures requires less time and labor than conventional optical systems. Measures differences in elevation to within 0.002 in. (0.05 mm). Floats at opposite ends of structure determine positions of cores in linear variable-differential transformers. Outputs of LVDT's carried by cables to control console, where displayed to operator as difference in core levels and therfore of ends of structure.

Hanninen, B.↗
NASA NTRS1991

Probing the core of Cepheus A - Millimeter and submillimeter observations

Moderate and high angular resolution (40-7 arcsec) maps are presented of the core of the Cepheus A star-forming region using CS J = 3-2 and J = 7-6 emission, which traces the dense gas component of the cloud core, and using far-infrared (450 and 800 microns) continuum emission tracing the warm dust component. Three regimes in the core are traced by these observations: (1) a small (about 0.14 pc), nearly circular central core of high density (1-10 x 10 to the 6th/cu cm) and temperature (30-100 K) containing at least 25 percent of the mass and which contains the active early-type star formation; (2) an extended (0.5 x 0.25 pc), NE-SW oriented core of mass 200-300 solar masses, temperature 30-40 K, and average density nH2 of about 10 to the 5th/cu cm and which, together with the central core, contains 60-80 percent of the total core mass; and (3) an extended core envelope of dimensions 0.5 x 0.85 pc oriented primarily north-south, and a lower density. The velocity structure of the core suggests that it is being disrupted by the high-velocity winds driving the molecular outflow and is not due to a rotating circumstellar disk.

Moriarty-Schieven, G. H.↗
NASA NTRS1993

Sequence and structural implications of a bovine corneal keratan sulfate proteoglycan core protein. Protein 37B represents bovine lumican and proteins 37A and 25 are unique

Amino acid sequence from tryptic peptides of three different bovine corneal keratan sulfate proteoglycan (KSPG) core proteins (designated 37A, 37B, and 25) showed similarities to the sequence of a chicken KSPG core protein lumican. Bovine lumican cDNA was isolated from a bovine corneal expression library by screening with chicken lumican cDNA. The bovine cDNA codes for a 342-amino acid protein, M(r) 38,712, containing amino acid sequences identified in the 37B KSPG core protein. The bovine lumican is 68% identical to chicken lumican, with an 83% identity excluding the N-terminal 40 amino acids. Location of 6 cysteine and 4 consensus N-glycosylation sites in the bovine sequence were identical to those in chicken lumican. Bovine lumican had about 50% identity to bovine fibromodulin and 20% identity to bovine decorin and biglycan. About two-thirds of the lumican protein consists of a series of 10 amino acid leucine-rich repeats that occur in regions of calculated high beta-hydrophobic moment, suggesting that the leucine-rich repeats contribute to beta-sheet formation in these proteins. Sequences obtained from 37A and 25 core proteins were absent in bovine lumican, thus predicting a unique primary structure and separate mRNA for each of the three bovine KSPG core proteins.

NASA Discipline Cell Biology↗
NASA NTRS1985

Observation of a coronal transient from 1.2 to 6 solar radii

The paper describes in detail the eruptive prominence associated coronal mas ejection of August 5, 1980, as seen in both the Solar Maximum Mission (SMM) coronagraph polarimeter and the Mauna Loa Observatory (MLO) K coronameter and prominence monitor. This event gives the first detailed look at the propagation of a 'depletion' transient into the outer corona. The event begins in the MLO K coronameter as a rising depletion of material, but appears later in the SMM coronograph as an ordinary coronal mass ejection with a three-part structure: a bright core within a dark lunette surrounded by a bright featureles 'loop'. A joint time-height plot of the major structures of the eruption seen by both instruments suggests that the three-part structure in the outer corona can be associated with features in the low corona (prominence, prominence cavity, outer bright front). It is argued from its observed mass that the leading loop in the SMM field of view is probably material that was in the background corona before the event. It is suggested that this material has been displaced and set into motion by the rising 'cavity.'

Illing, R. M. E.↗
NASA NTRS2021

Damage Tolerance of Candidate Sandwich Structure for the Space Launch System (SLS) Payload Adapter Fitting (PAF)

This Technical Memorandum presents results from a damage tolerance study undertaken in support of the payload adapter fitting (PAF) for the Space Launch System (SLS) program at NASA’s Marshall Space Flight Center (MSFC). The study consisted of determining the compression-after-impact (CAI) strength of candidate carbon/epoxy face sheet sandwich structure that has been identified for potential use to manufacture the PAF hardware. Two types of core material that have been considered for use on the PAF structure were used in this study. One was an aluminum honeycomb and the other was a Rohacell foam. Levels of barely visible impact damage (BVID) were determined for the types of sandwich structure tested in this study and this level of damage was used for CAI strength testing. It was found that the honeycomb core sandwich structure failed by face sheet failure and the foam core sandwich structure failed by core shear failure. CAI strength values were normalized by weight of the sandwich structure since lower mass is desirable for this structure.

sandwich structure↗
NASA NTRS1986

Cometary memory of interstellar aluminum

It is shown that the distribution of refractory metals in a comet-nucleus drill core carries a chemical memory quite distinct from that of volatiles. Using aluminum as an example, it is demonstrated that very refractory structures, either grain cores or refractory aggregates of cores, must be much older than the volatile component. It is argued that isotopic anomalies are specifically associated with aluminum. An evolutionary model capable of rationalizing the interstellar gas depletions of Al and Mg is advocated. The distribution of Al in comets is shown to be crucial to understanding the origin of comets and of the solar system.

Clayton, Donald D.↗
NASA NTRS2001

Determination of the Hyperfine Structure of N2D(+)

We present new high spectral resolution observations of the N2D+ J = 2 yields 1 and J = 3 yields 2 as well as N2H+ J = 3 yields 2 lines, towards dense molecular cores. The hyperfine structure of the N2H+ and N2D+ transitions is clearly resolved in these sources, in excellent agreement with quantum mechanical calculations. Optical depths are determined from the observed spectra, leading to D/H values of the order of 10 - 30% for the N2D+/N2H+ system. There are a large number of hyperfine components and in addition to providing satellites they contribute to the broadening and asymmetric shapes of the N2H+ and N2D+ line profiles. It is therefore important to take into account the detailed hyperfine structure of the transitions when deducing astrophysical parameters from observed data.

Gerin, Maryvonne↗
NASA NTRS1996

X-Ray Properties of Radio Jets

ROSAT observations of the atmospheres of a number of radio galaxies containing prominent jets are described. The imaging and spectroscopic results obtained by the PSPC are used to obtain fluxes for the non-thermal core sources and structures for the atmospheres of the host galaxies or their groups. The implications for the environments of the radio jets and for the radio cores are discussed.

Birkinshaw, M.↗
NASA NTRS1992

Structural review of the Vredefort dome

The structure of the older-than-3.2-Ga Archean basement and Archean-to-Precambrian sedimentary/volcanic rocks (3.07 to ca. 2.2 Ga) in the center of the Witwatersrand Basin to the southwest of Johannesburg (South Africa) is dominated by the ca. 2.0-Ga megascopic Vredefort 'Dome' structure. The effect of the 'Vredefort event' is demonstrably large and is evident within a northerly arc of about 100 km radius around the granitic core of the structure. Northerly asymmetric overturning of the strata is observed within the first 17 km (strata is horizontal in the south), followed by a 40-km-wide rim synclinorium. Fold and fault structures (normal, reverse, and strike-slip) are locally as well as regionally concentrically arranged with respect to the northern and western sides of the structure. The unusual category of brittle deformation, the so-called 'shock deformation', observed in the collar strata has attracted worldwide attention over the past two decades. These deformation phenomena include the presence of coesite and stishovite, mylonites, and pseudotachylites, cataclasis at a microscopic scale, and the ubiquitous development of multiply striated joint surfaces (which include shatter cones, orthogonal, curviplanar, and conjugate fractures). The macroscopic to microscopic deformation features have led to the formulation of various hypotheses to account for the origin of the Vredefort structure: (1) tectonic hypotheses--deep crustal shear model, doming and N-directed thrust fault model, fold interference model, and diapir model; (2) the exogenous bolide impact hypothesis; and (3) the endogenous cryptoexplosion model.

Colliston, W. P.↗
NASA NTRS1985

Result of Monte-Carlo simulation of electron-photon cascades in lead and layers of lead-scintillator

Results of Monte-Carlo simulation of electromagnetic cascade development in lead and lead-scintillator sandwiches are analyzed. It is demonstrated that the structure function for core approximation is not applicable in the case in which the primary energy is higher than 100 GeV. The simulation data has shown that introducing an inhomogeneous chamber structure results in subsequent reduction of secondary particles.

Wasilewski, A.↗
NASA NTRS1980

Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core

Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

Ko, W. L.↗
NASA NTRS1972

Excitation, response, and fatigue life estimation methods for the structural design of externally blown flaps

Means for predicting the fluctuating pressures acting on externally blown flap surfaces are developed on the basis of generalizations derived from non-dimensionalized empirical data. Approaches for estimation of the fatigue lives of skin-stringer and honeycomb-core sandwich flap structures are derived from vibration response analyses and panel fatigue data. Approximate expressions for fluctuating pressures, structural response, and fatigue life are combined to reveal the important parametric dependences. The two-dimensional equations of motion of multi-element flap systems are derived in general form, so that they can be specialized readily for any particular system. An introduction is presented of an approach to characterizing the excitation pressures and structural responses which makes use of space-time spectral concepts and promises to provide useful insights, as well as experimental and analytical savings.

Ungar, E. E.↗
NASA NTRS1992

Radio and optical observations of 0218+357 - The smallest Einstein ring?

VLA radio observations and optical imaging and spectroscopy of the Einstein radio ring 0218+357 are presented. The ring is detected at 22.4 GHz and shows a basically similar structure at 5, 15, and 22.4 GHz. The B component has varied and was about 15 percent brighter in the 8.4 GHz data than in the data of Patnaik et al. (1992). The ring is highly polarized. A weak jetlike feature extending out roughly 2 arcsec to the southeast of component A is detected at 6 cm. The source has amorphous radio structure extending out to about 11 arcsec from the core. For an adopted redshift of 0.68, the extended radio emission is very powerful. The optical spectrum is rather red and shows no strong features. A redshift of about 0.68 is obtained. The identification is a faint compact m(r) about 20 galaxy which extends to about 4.5 arcsec (about 27 kpc). As much as 50 percent of the total light may be due to a central AGN. The observed double core and ring may be produced by an off-center radio core with extended radio structure.

O'Dea, Christopher P.↗