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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 433 records · Page 24

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NASA NTRS1990

Probabilistic simulation of uncertainties in thermal structures

Development of probabilistic structural analysis methods for hot structures is a major activity at Lewis Research Center. It consists of five program elements: (1) probabilistic loads; (2) probabilistic finite element analysis; (3) probabilistic material behavior; (4) assessment of reliability and risk; and (5) probabilistic structural performance evaluation. Recent progress includes: (1) quantification of the effects of uncertainties for several variables on high pressure fuel turbopump (HPFT) blade temperature, pressure, and torque of the Space Shuttle Main Engine (SSME); (2) the evaluation of the cumulative distribution function for various structural response variables based on assumed uncertainties in primitive structural variables; (3) evaluation of the failure probability; (4) reliability and risk-cost assessment, and (5) an outline of an emerging approach for eventual hot structures certification. Collectively, the results demonstrate that the structural durability/reliability of hot structural components can be effectively evaluated in a formal probabilistic framework. In addition, the approach can be readily extended to computationally simulate certification of hot structures for aerospace environments.

Chamis, Christos C.↗

NASA NTRS1990

Probabilistic simulation of uncertainties in thermal structures

Development of probabilistic structural analysis methods for hot structures is a major activity at NASA-Lewis, and consists of five program elements: (1) probabilistic loads, (2) probabilistic finite element analysis, (3) probabilistic material behavior, (4) assessment of reliability and risk, and (5) probabilistic structural performance evaluation. Attention is given to quantification of the effects of uncertainties for several variables on High Pressure Fuel Turbopump blade temperature, pressure, and torque of the Space Shuttle Main Engine; the evaluation of the cumulative distribution function for various structural response variables based on assumed uncertainties in primitive structural variables; evaluation of the failure probability; reliability and risk-cost assessment; and an outline of an emerging approach for eventual hot structures certification. Collectively, the results demonstrate that the structural durability/reliability of hot structural components can be effectively evaluated in a formal probabilistic framework. In addition, the approach can be readily extended to computationally simulate certification of hot structures for aerospace environments.

Chamis, C. C.↗

NASA NTRS1982

Satellite communications for the Pacific islands. Second year report

Requirements, options and costs for use of communications satellites in underserved areas of the Pacific Basin are described with emphasis on extended utilization of INTELSAT. The economic structures within and among Pacific Basin entities are examined, particularly the relationship between the growth of regional trade and telecommunications potential for the region. Suitable satellite services are recommended and the financial implications for extended utilization of communications satellites in the Pacific Basin are considered.

Young, E.↗

NASA NTRS1994

Raman structural studies of the nickel electrode

The objectives of this investigation have been to define the structures of charged active mass, discharged active mass, and related precursor materials (alpha-phases), with the purpose of better understanding the chemical and electrochemical reactions, including failure mechanisms and cobalt incorporation, so that the nickel electrode may be improved. Although our primary tool has been Raman spectroscopy, the structural conclusions drawn from the Raman data have been supported and augmented by three other analysis methods: infrared spectroscopy, powder X-ray Diffraction (XRD), and x-ray absorption spectroscopy (in particular EXAFS, Extended X-ray Absorption Fine Structure spectroscopy).

Cornilsen, Bahne C.↗

NASA NTRS2008

Estimating Shock Spectra: Extensions beyond GEVS

Shock response spectra (SRS) are the standard description of some vibration environments on spacecraft for equipment qualification. For shock events produced by pyrotechnic devices, SRS can have significant frequency content as high as 10 kHz. It is difficult to construct and analyze finite element models that can resolve dynamic behavior at such high frequencies. GEVS provides simple, empirically based methods for approximating the SRS for a wide variety of shock events. It begins with a base SRS according to the type of pyrotechnic device, and then provides attenuation relations to adjust this SRS according to distance from the shock source, the type of structural frame and the properties of any structural joints between the source and equipment. In our paper we extend GEVS to include more detailed information about the spacecraft structure. To retain the general framework of GEVS, we begin with a base SRS and adjust this SRS using attenuation relations. We use modal and traveling wave concepts to derive the attenuation relations for simple canonical structures. Then we show how these concepts can be used to analyze more complex structures using finite element mode shapes to explicitly calculate the attenuation factors. Since the low- to mid-frequency finite element modal information is extrapolated to obtain the low- to high-frequency attenuation relations, the resulting attenuated SRS is formulated as an upper bound rather than as mean predicted values. We illustrate the extended GEVS approach by analyzing the impact response of composite tubes and the shock response of the STEREO spacecraft.

Igusa, Takeru↗

NASA NTRS1989

Solar X-ray Astronomy Sounding Rocket Program

Several broad objectives were pursued by the development and flight of the High Resolution Soft X-Ray Imaging Sounding Rocket Payload, followed by the analysis of the resulting data and by comparison with both ground based and space based observations from other investigators. The scientific objectives were: to study the thermal equilibrium of active region loop systems by analyzing the X-ray observations to determine electron temperatures, densities, and pressures; by recording the changes in the large scale coronal structures from the maximum and descending phases of Cycle 21 to the ascending phase of Cycle 22; and to extend the study of small scale coronal structures through the minimum of Cycle 21 with new emphasis on correlative observations.

Moses, J. Daniel↗

NASA NTRS1998

Elevated Temperature Crack Growth Behavior in HSCT Structural Materials

Structures in super-sonic aircraft are subjected to conditions of high temperature and cyclic and sustained loading for extended periods of time. The durability of structures fabricated from aluminum and certain titanium alloys in such demanding conditions is of primary concern to the designers and manufacturers of futuristic transport aircraft. Accordingly, the major goal of this project was to evaluate the performance and durability of high temperature aluminum and titanium alloys for use in high speed civil transport (HSCT) structures. Additional goals were to develop time-dependent fracture mechanics methodology and test methods for characterizing and predicting elevated temperature crack growth behavior in creep-brittle materials such as ones being considered for use in HSCT structures and to explore accelerated methods of simulating microstructural degradation during service and measuring degraded properties in these materials.

Saxena, Ashok↗

NASA NTRS1986

Effects of Structural Flexibility on Aircraft-Engine Mounts

Analysis extends technique for design of widely used type of vibration-isolating mounts for aircraft engines, in which rubber mounting pads located in plane behind center of gravity of enginepropeller combination. New analysis treats problem in statics. Results of simple approach useful in providing equations for design of vibrationisolating mounts. Equations applicable in usual situation in which engine-mount structure itself relatively light and placed between large mass of engine and other heavy components of airplane.

Phillips, W. H.↗

NASA NTRS1990

Non-steller light from high-redshift radiogalaxies

With the aid of a new IRCAM image of 3C356, researchers question the common assumption that radiosource-stimulated starbursts are responsible for the extended optical emission aligned with radio structures in high-redshift radiogalaxies. They propose an alternative model in which the radiation from a hidden luminous quasar is beamed along the radio axis and illuminates dense clumps of cool gas to produce both extended narrow emission line regions and, by Thomson scattering, extended optical continua. Simple observational tests of this model are possible and necessary if we are to continue to accept that the color, magnitude and shape evolution of radiogalaxies are controlled by the active evolution of stellar populations.

Rawlings, Steve↗

NASA NTRS1993

Applications of x ray absorption fine structure to the in situ study of the effect of cobalt in nickel hydrous oxide electrodes for fuel cells and rechargeable batteries

Electronic and structural aspects of composite nickel-cobalt hydrous oxides have been examined in alkaline solutions using in situ X-ray absorption fine structure (XAFS). The results obtained have indicated that cobalt in this material is present as cobaltic ions regardless of the oxidation state of nickel in the lattice. Furthermore, careful analysis of the Co K-edge Extended X-ray absorption fine structure data reveals that the co-electrodeposition procedure generates a single phase, mixed metal hydrous oxide, in which cobaltic ions occupy nickel sites in the NiO2 sheet-like layers and not two intermixed phases each consisting of a single metal hydrous oxide.

Kim, Sunghyun↗

NASA NTRS1990

Patterns in simulated turbulent channel flow

The surface stress is a key diagnostic in wall bounded turbulent flows. Large fluctuations in the stress are believed to be associated with intermittent 'bursting' events during which a large proportion of the turbulence production takes place. If this is so, then a detailed investigation of the structure of the surface stress and its spatial relationship to events within the flow could have wide application in drag reduction and other aspects of flow control. The initial phase of this project, therefore, concentrated on the surface stress field. The first objective is to carry out a statistical analysis of the instantaneous surface stress in a simulated turbulent channel flow, including comparison with multipoint experimental data from a zero pressure gradient turbulent boundary layer. The second objective is to apply a simple pattern recognition procedure to educe the characteristic spatial structure of various flow diagnostics. The final objective is to extend the pattern recognition analysis to examine the whole three dimensional structure of the flow.

Stretch, D.↗

NASA NTRS1992

The radio source and bipolar nebulosity in the Seyfert galaxy NGC 3516

Results of radio continuum and optical emission-line observations of the type 1 Seyfert galaxy NGC 3516 are presented. The radio maps reveal an elongated one-sided curved structure, which comprises a series of small-scale 'blobs' and extends up to 4 kpc from the nucleus. This radio structure is aligned and cospatial with one side of the double-sided and highly symmetric Z-shaped emission-line structure. It is argued that these morphological features are associated with a bipolar gaseous outflow from the nucleus of NGC 3516. The radio 'blobs' are elongated roughly perpendicular to the apparent local direction of the outflow, a result which is interpreted in terms of synchrotron emission from outflow-driven shock waves.

Miyaji, Takamitsu↗

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 NTRS1978

Interdisciplinary research and development on the effects of the nature and properties of ceramic materials in the design of advanced structural components

An educational development and supportive research program on ceramic materials established to advance design methodology, improve materials, and develop engineers knowledgable in design with and use of high performance ceramic materials is described. Emphasis is on the structures and related materials problems in a ceramic turbine engine, but applications in coal gasification, solar conversion, and magnetohydrodynamic technologies are considered. Progress of various research projects in the areas of new materials, processing, characterization, and nondestructive testing is reported. Fracture toughness determination, extended X-ray absorption fine structure measurements, and grain boundary effects in beta-alumina are among the topics covered.

Source record↗

NASA NTRS1995

The structure of the distanct geomagnetic tail during long periods of northward IMF

We have used a newly developed, parallelized, global MHD magnetosphere - ionosphere simulation model with a 400 R(sub E) long tail to study the evolution, structure, and dynamics of the distant magnetotail during extended periods of northward interplanetary magnetic field (IMF). We find that the tail evolves to a nearly time stationary structure about one solar wind transit time after the IMF turns northward. Four regions of different magnetic topology can be distinguished which extend at least to the end of the simulation box at 400 R(sub E). Besides lobe field lines and open solar wind field lines tailward of an X-line, there is a broad boundary layer of closed field lines which we call the tail flank boundary layer (TFBL). Just inside the TFBL there is a region of closed field loops. Besides the X-line we find two O-lines which are enclosed by the closed field loops and are roughly aligned with the tail axis. Together they form a U shaped separator between the northward and the southward plasma sheet fields.

Raeder, J.↗

NASA NTRS1979

A concept for dynamic control of RPV information system parameters

A globally adaptive image compression structure has been developed for use in the tactical environment of a remotely piloted vehicle. The control structure is based on an image compression algorithm RM2 but can be easily extended to standard algorithms. It is shown that this structure provides an operator with the flexibility to dynamically maximize the usefulness of a limited and changing bit rate and should significantly improve overall system performance in tactical environments.

Rice, R. F.↗

NASA NTRS1986

Personnel occupied woven envelope robot

The use of nonmetallic or fabric structures for space application is considered. The following structures are suggested: (1) unpressurized space hangars; (2) extendable tunnels for soft docking; and (3) manned habitat for space stations, storage facilities, and work structures. The uses of the tunnel as a passageway: for personnel and equipment, eliminating extravehicular activity, for access to a control cabin on a space crane and between free flyers and the space station are outlined. The personnal occupied woven envelope robot (POWER) device is shown. The woven envelope (tunnel) acts as part of the boom of a crane. Potential applications of POWER are outlined. Several possible deflection mechanisms and design criteria are determined.

Wessling, F. C.↗

NASA NTRS1997

Post-flare loops embedded in a hot coronal fan-like structure

Limb events were demonstrated on the sun in which rising post-flare loops were embedded in hot structures looking in soft X-rays like fans of rays, formed during the flare and extending high into the corona. One of these structures is analyzed and it is suggested that these fans of rays represent temporary ministreamers, along which mass flows into interplanetary space. This suggestion is supported by maps of solar wind density constructed from scintillation measurements.

Svestka, Z.↗