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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Upper-ocean velocity structure of Gulf Stream warm-core ring 82B

Acoustic-Doppler current profiling of warm-core ring (WCR) 82B revealed changes in the velocity structure over much of the ring's 7-month lifespan. As ring diameter decreased, peak speeds in the high-velocity region decreased from 0.8 m/s in April 1982 to 0.5 m/s in August 1982. Azimuthally averaged velocities revealed the core of WCR 82B to be in near solid-body rotation, with little measurable horizontal divergence at 100 m. In addition, potential vorticity was conserved in the ring core despite interactions with the Gulf Stream and large changes in ring size. Deviations from symmetry in WCR 82B were caused by superposition with the shelf-slope front, small cyclonic eddies, and upper-layer mean flow.

Joyce, T. M.↗
NASA NTRS2014

Aircraft Engine Exhaust Nozzle System for Jet Noise Reduction

The aircraft exhaust engine nozzle system includes a fan nozzle to receive a fan flow from a fan disposed adjacent to an engine disposed above an airframe surface of the aircraft, a core nozzle disposed within the fan nozzle and receiving an engine core flow, and a pylon structure connected to the core nozzle and structurally attached with the airframe surface to secure the engine to the aircraft.

Thomas, Russell H.↗
NASA NTRS2012

Photogrammetric Verification of Fiber Optic Shape Sensors on Flexible Aerospace Structures

Multi-core fiber (MCF) optic shape sensing offers the possibility of providing in-flight shape measurements of highly flexible aerospace structures and control surfaces for such purposes as gust load alleviation, flutter suppression, general flight control and structural health monitoring. Photogrammetric measurements of surface mounted MCF shape sensing cable can be used to quantify the MCF installation path and verify measurement methods.

Moore, Jason P.↗
NASA NTRS2000

Sandwich Composite, Syntactic Foam Core Based, Application for Space Structures

The current Solid Rocket Booster (SRB) launch vehicle has several metal based components that require a Thermal Protective System (TPS) be applied to the exterior surface to ensure its structural integrity and to protect the interior hardware from aerodynamic heating. TPS materials have distinct disadvantages associated with their use. One disadvantage to the application of TPS is that it can act as a debris source to the Space Shuttle Orbiter during flight and it also adds weight to the system without directly contributing any structural strength. One of the specific areas examined under this program was to replace a metal/TPS system with polymer based composites. A polymer matrix based sandwich composite was developed which had both structural and insulative properties to meet the high aerodynamic structural and heating load survival requirements. The SRB Nose Cap was selected as a candidate for this application. The sandwich system being qualified for this application is a carbon/epoxy outer and inner skin with a high strength-low thermal conductivity syntactic foam core.

Hodge, Andrew J.↗
NASA NTRS2011

The Invasive Species Forecasting System

The Invasive Species Forecasting System (ISFS) provides computational support for the generic work processes found in many regional-scale ecosystem modeling applications. Decision support tools built using ISFS allow a user to load point occurrence field sample data for a plant species of interest and quickly generate habitat suitability maps for geographic regions of management concern, such as a national park, monument, forest, or refuge. This type of decision product helps resource managers plan invasive species protection, monitoring, and control strategies for the lands they manage. Until now, scientists and resource managers have lacked the data-assembly and computing capabilities to produce these maps quickly and cost efficiently. ISFS focuses on regional-scale habitat suitability modeling for invasive terrestrial plants. ISFS s component architecture emphasizes simplicity and adaptability. Its core services can be easily adapted to produce model-based decision support tools tailored to particular parks, monuments, forests, refuges, and related management units. ISFS can be used to build standalone run-time tools that require no connection to the Internet, as well as fully Internet-based decision support applications. ISFS provides the core data structures, operating system interfaces, network interfaces, and inter-component constraints comprising the canonical workflow for habitat suitability modeling. The predictors, analysis methods, and geographic extents involved in any particular model run are elements of the user space and arbitrarily configurable by the user. ISFS provides small, lightweight, readily hardened core components of general utility. These components can be adapted to unanticipated uses, are tailorable, and require at most a loosely coupled, nonproprietary connection to the Web. Users can invoke capabilities from a command line; programmers can integrate ISFS's core components into more complex systems and services. Taken together, these features enable a degree of decentralization and distributed ownership that have helped other types of scientific information services succeed in recent years.

Schnase, John↗
NASA NTRS2020

DGEN Aeropropulsion Research Turbofan Source-Diagnostic Test: Experimental Setup and Acoustic-Data Structure

The experimental setup of, and available data from a recent core/combustor-noise source-diagnostic test utilizing a small turbofan engine are described. The 2019 test campaign continued the investigation of the core/combustor-noise component of aircraft-propulsor noise begun in an earlier baseline test, but with a more extensive acoustic-instrumentation layout. The purpose of both tests was to better understand the impact on civilian-transport airport-community noise from turbofan-combustor sources and thereby to lay the foundation for improved noise-prediction methods and noise-mitigation techniques. Simultaneous high-data-rate acoustic measurements were obtained using a circumferential sensor array at the core nozzle exit in conjunction with sideline and farfield microphone arrays. The test matrix contained engine operational points from engine idle to maximum power and was repeated for different circumferential and sideline array configurations, as well as for redundancy. The extensive data set (up to 93 channels of data and various configurations) allows the application of advanced source-separation and phased-array methods to elucidate not only the core-noise structure, but also the propagation characteristics of other propulsion noise sources. The present report provides a detailed description of the different test points, their associated instrumentation layouts, and the structure of the acquired data set. Results from various data analyses are reported separately.

Aeroacoustics↗
NASA NTRS1999

Microflaring in Low-Lying Core Fields and Extended Coronal Heating in the Quiet Sun

We have previously reported analyses of Yohkoh SXT data examining the relationship between the heating of extended coronal loops (both within and stemming from active regions) and microflaring in core fields lying along neutral lines near their footpoints (J. G. Porter, D. A. Falconer, and R. L. Moore 1998, in Solar Jets and Coronal Plumes, ed. T. Guyenne, ESA SP-421, and references therein). We found a surprisingly poor correlation of intensity variations in the extended loops with individual microflares in the compact heated areas at their feet, despite considerable circumstancial evidence linking the heating processes in these regions. Now, a study of Fe XII image sequences from SOHO EIT show that similar associations of core field structures with the footpoints of very extended coronal features can be found in the quiet Sun. The morphology is consistent with the finding of Wang et al. (1997, ApJ 484, L75) that polar plumes are rooted at sites of mixed polarity in the magnetic network. We find that the upstairs/downstairs intensity variations often follow the trend, identified in the active region observations, of a weak correspondence. Apparently much of the coronal heating in the extended loops is driven by a type of core field magnetic activity that is "cooler" than the events having the coronal signature of microflares, i.e., activity that results in little heating within the core fields themselves. This work was funded by the Solar Physics Branch of NASA's Office of Space Science through the SR&T Program and the SEC Guest Investigator Program.

Porter, Jason G.↗
NASA NTRS2003

Investigation of the Surface Stress in SiC and Diamond Nanocrystals by In-situ High Pressure Powder Diffraction Technique

The real atomic structure of nanocrystals determines key properties of the materials. For such materials the serious experimental problem lies in obtaining sufficiently accurate measurements of the structural parameters of the crystals, since very small crystals constitute rather a two-phase than a uniform crystallographic phase system. As a result, elastic properties of nanograins may be expected to reflect a dual nature of their structure, with a corresponding set of different elastic property parameters. We studied those properties by in-situ high-pressure powder diffraction technique. For nanocrystalline, even one-phase materials such measurements are particularly difficult to make since determination of the lattice parameters of very small crystals presents a challenge due to inherent limitations of standard elaboration of powder diffractograms. In this investigation we used our methodology of the structural analysis, the 'apparent lattice parameter' (alp) concept. The methodology allowed us to avoid the traps (if applied to nanocrystals) of standard powder diffraction evaluation techniques. The experiments were performed for nanocrystalline Sic and GaN powders using synchrotron sources. We applied both hydrostatic and isostatic pressures in the range of up to 40 GPa. Elastic properties of the samples were examined based on the measurements of a change of the lattice parameters with pressure. The results show a dual nature of the mechanical properties (compressibilities) of the materials, indicating a complex, core-shell structure of the grains.

Palosz, B.↗
NASA NTRS1985

Dual polarization VLBI observations of stellar binary systems at 5 GHz

The binary systems Sigma CrB, SZ Psc, HR 1099, UX Ari, HR 5110, Algol, and Cyg X-1 are characterized in terms of marcsec-scale radio structure on the basis of dual-polarization observations at 4.969-4.997 GHz, obtained with an international VLBI array comprising the 100-m Effelsberg, 36-m Haystack, 42-m Green Bank, 26-m Fort Davis, 130-m-equivalent VLA, and 40-m Owens Valley telescopes (system temperatures 40-70 K) at 22-14 h UT on July 26-27, 1983. The data are presented in graphs and tables and discussed in detail. Single Gaussian brightness distributions with theta(FWHM) = 0.5-2.0 marcsec and brightness temperatures (2-200) x 10 to the 8th K are determined for four sources; core-halo structures are found for UX Ari and Algol; and an upper limit of 50 microarcsec is established for the angular separation of the regions of left and right circular polarization. The gross features seen in RS CVn systems are explained in terms of a simple expanding-coronal-loop model of flare events.

Mutel, R. L.↗
NASA NTRS1993

Strontium and oxygen isotope study of M-1, M-3 and M-4 drill core samples from the Manson impact structure, Iowa: Comparison with Haitian K-T impact glasses

Strontium and oxygen isotope analyses were performed on 8 samples from the M-1, M-3, and M-4 cores recently drilled at the Manson impact structure. The samples were three elastic sedimentary rocks (of probable Cretaceous age) which occurred as clasts within the sedimentary clast breccia, two samples of crystalline rock breccia matrix, and three samples of dolomite and limestone. The Sr-87/Sr-86 (corrected to 65 Ma) ratios were much higher than those in impact glasses from the Haitian Cretaceous-Tertiary (K-T) boundary. Isotope mixing calculations demonstrate that neither the silicate or carbonate rocks analyzed from the Manson crater, or mixtures of these rocks are appropriate source materials for the Haitian impact glasses. However, the Sr-87/Sr-86 (65Ma) ratio and delta O-18 value of the Ca-rich Haitian glasses are well reproduced by mixtures of Si-rich Haitian glass with platform carbonate of K-T age.

Blum, Joel D.↗
NASA NTRS1994

Ellipticals with kinematically distinct cores : HST imaging of the nuclear structure of IC 1459

The elliptical galaxy IC 1459 has one of the strongest counter-rotating core components of any observed elliptical. Here we present Hubble Space Telescope (HST) Planetary Camera images of the center of IC 1459. Before deconvolution, our V band images reveal a bright point source at the galaxy nucleus, and dust near the nucleus. After removal of the central point source, deconvolution and model fitting, we show that the central starlight profile is better fit by a 'cusp' model than an isothermal core model. The photometric properties of the stellar light are comparable to those of other ellipticals without counter-rotating core components. There is an indication of a central stellar disk, although its detection is complicated by the extensive dust. Although the velocity field of the emission-line gas is ordered, the dust distribution is very irregular, and indicates nonequilibrium motions. The irregular dust distribution suggests that material is currently infalling and may be fueling the active nucleus. There is no direct evidence which relates the dust and gas to the peculiar stellar kinematics.

Forbes, Duncan A.↗
NASA NTRS1981

Summary of the workshop on active galaxies and quasars

The paper reports highlights of discussions carried out at the Tenth Texas Symposium on Relativistic Astrophysics concerning BL Lacertae objects and quasars and their relationship to active galactic nuclei. The discussions considered X-ray, optical and radio observations of active galaxies and quasars showing features which may be interpreted as jets or beams, and X-ray and VLBI observations of core-jet structures exhibiting apparent supraluminal expansion. Attention was also given to the properties of the energy source in the center of the active galaxies and quasars, the nature of quasar emission line regions, the production of the continuum in quasars and active galactic nuclei, and evidence for the association of quasars and BL Lac objects with galaxies.

Weistrop, D.↗
NASA NTRS1982

VLBI observations of the nucleus and jet of M87

The nucleus and jet of M87 was mapped with an eight-station very long baseline interferometric array at 18 cm wavelength with high dynamic range. It was found that the nucleus of M87 consists of a core-jet structure with a peak brightness temperature greater than 10 to the 10th K. Emission is shown to extend for more than 50 milli-arcsec with a brightness temperature exceeding 10 to the 8th K along a position angle of 288 degrees, which precisely matches the position angle of the 20'' radio/optical/X-ray jet. In addition, the nucleus contains a significant structure of lower brightness at approximately the same position angle, although no counterjet is observed. By invoking relativistic beaming in order to enhance the jet and diminish the counterjet, it is shown that the jet must be aligned within about 60 degrees to our line of sight, and its flow velocity must exceed about 60% of the speed of light. The knots embedded in the 20'' jet contain no bright compact structures, and the sizes of the innermost knot (knot D) is between 0.1-0.3''.

Reid, M. J.↗
NASA NTRS1983

VLBI maps of 3C 273 and 3C 345 at 2.3 GHz

Maps of the quasars 3C 273 and 3C 345 made at 2.3 GHz with an eight station VLBI array are presented. Five compact components spanning 45 milli-arcsec are seen in 3C 273, and four are seen in 3C 345. Comparisons with maps at higher and lower frequencies show that in both sources the core, which dominates the high-frequency 'core-jet' structure, is strongly self-absorbed at 2.3 GHz and below. The jet components have flat spectra, peaking between 2 and 5 GHz. In both sources the VLBI jet curves toward the direction of the arcsecond-scale outer jet.

Cohen, M. H.↗
NASA NTRS1984

Discovery of solar system-size halos around young stars

Near-infrared speckle interferometric observations of five pre-main-sequence stars reveal a core-halo structure around two of these stars: HL Tau and R Mon. The halo light distribution is shown to arise from scattered light from small circumstellar particles. Halo sizes of 320 x 200 AU (alpha x delta FWHM) and 1300 x 1300 AU are deduced for HL Tau and R Mon, respectively, and the halo light is substantially bluer than the stellar light. The minimum mass of small particles in the scattering regions is comparable to the earth's mass in HL Tau and ten times greater in R Mon. Mass loss from the stars is almost certainly insufficient to produce the halo matter. The halos probably consist of relatively slowly moving matter bound gravitationally to the stars. From the size and mass of the circumstellar matter, it appears likely that these halos are in the early stage in the formation of planet-forming disks around the young stars.

Beckwith, S.↗
NASA NTRS1985

High-resolution surface photometry of elliptical galaxies

High-resolution CCD surface photometry profiles have been obtained for a sample of 42 nearby elliptical and SO galaxies as a first step in a program to investigate their central structure and core properties. A comparison of the present profiles to those of other observers shows that the accuracy of the central surface brightnesses is to better than 0.02 mag rms. Central resolution is limited by the atmospheric seeing PSF which is measured for each profile. A hybrid Fourier deconvolution procedure has been developed to correct the surface photometry for seeing in a model-independent way. Tests of the procedure on simulated galaxy images show that intrinsic core radii equal to the seeing FWHM or larger can be recovered from the observations. Application of the deconvolution procedure to the observed galaxies yields surface photometry profiles of slightly sub-arc second resolution.

Lauer, T. R.↗
NASA NTRS1985

Application of Gr/PMR-15 to commercial aircraft

Following from early experience with polyimides on the SST program and Shuttle aft flap studies the Boeing Company is now working on collaborative programs with its principal nacelle suppliers to pursue the development of Gr/PMR-15 nacelle components. Two programs are currently in effect. The first program is directed specifically towards the flight test and service evaluation at the earliest possible date of a 747 nacelle core cowl structure. The second program seeks to firmly establish the producibility and cost of a 757 thrust reverser C duct in a production environment. The near term objectives of these programs include: (1) the comparison of estimated cost and weight of Gr/PMR-15 versus metal structure, (2) the engine test of representative composite structure, (3) the preliminary design and analysis of the C duct structure, and (4) the preparation of cost data and time schedules for the development and producibility program. In addition to powerplant structure, the propulsion ducting system has shown to be a strong candidate for Gr/PMR-15 application. Currently, the Boeing 747 Organization is evaluating the use of PMR-15 matrix composites to replace nearly 800 lbs of titanium ducting per airplane.

Postlewaite, J.↗