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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 NTRS1992

Optical and radio variability in blazars

An analysis is presented of the optical (0.44 micron) and radio flux density variations (4.8, 8.0, and 14.5 GHz) of the five best observed variable AGN, of which three are BL Lac objects and two are optically violent variable (OVV) quasars. For each object the nature of the variability at individual wavelengths is determined by using a structure function analysis and the autocorrelation function as calculated from the discrete correlation technique. Both techniques yield similar results, showing that the optical variations are similar for all objects and are a combination of flicker and shot noise. The radio variability is distinct, being described by shot noise (less variation at short times), with the two OVVs exhibiting the most extreme behavior. The time lag between the variations at the three radio frequencies and the optical flux is studied with the discrete cross-correlation function and the mean variance methods. It is concluded that the optical and radio emitting regions are physically related, exist on distinct time scales, and excite their synchrotron emitting plasmas differently.

Hufnagel, Beth R.↗
NASA NTRS1992

Motion at the ionization front in the Orion nebula - A kinematic study of the forbidden O I line

The kinematics of the ionization front in H II regions is investigated via a study of the collisionally excited forbidden O I emission at 630 nm. Slit spectra of 5/km s resolution are used to examine the velocities of forbidden O I across the inner few arcminutes of M42. The mean velocity is significantly more positive than for other ions, which confirms the argument that the ionization front is formed against the parent molecular cloud OMC 1. It is inferred that there is acceleration of material in the ionization front at the parent molecular cloud. A new model for M42 based largely on optical emission-line and radio absorption-line studies is presented. A detailed statistical analysis indicates agreement between the structure function and the Kolmogorov theory for turbulence.

O'Dell, C. R.↗
NASA NTRS1992

ICAN/DAMP-integrated composite analyzer with damping analysis capabilities: User's manual

This manual describes the use of the computer code ICAN/DAMP (Integrated Composite Analyzer with Damping Analysis Capabilities) for the prediction of damping in polymer-matrix composites. The code is written in FORTRAN 77 and is a version of the ICAN (Integrated Composite ANalyzer) computer program. The code incorporates a new module for synthesizing the material damping from micromechanics to laminate level. Explicit micromechanics equations based on hysteretic damping are programmed relating the on-axis damping capacities to the fiber and matrix properties and fiber volume ratio. The damping capacities of unidirectional composites subjected to off-axis loading are synthesized from on-axis damping values. The hygrothermal effect on the damping performance of unidirectional composites caused by temperature and moisture variation is modeled along with the damping contributions from interfacial friction between broken fibers and matrix. The temperature rise is continuously vibrating composite plies and composite laminates is also estimated. The ICAN/DAMP user's manual provides descriptions of the damping analysis module's functions, structure, input requirements, output interpretation, and execution requirements. It only addresses the changes required to conduct the damping analysis and is used in conjunction with the 'Second Generation Integrated Composite Analyzer (ICAN) Computer Code' user's manual (NASA TP-3290).

Saravanos, Dimitrious A.↗
NASA NTRS1992

NASA experimental airborne doppler radar and real time processor for wind shear detection

The topics are presented in viewgraph form and include the following: experimental radar system capabilities; an experimental radar system block diagram; wind shear radar signal and data processor (WRSDP); WRSDP hardware architecture; WRSDP system design goals; DSP software development tools; OS-9 software development tools; WRSDP digital signal processing; WRSDP display operational modes; WRSDP division of functions; structure of WRSDP signal and data processing algorithms; and the wind shear radar flight experiment.

Schaffner, Philip H.↗
NASA NTRS1993

An evaluation of satellite-derived humidity and its relationship to convective development

An aircraft prototype of the High-Resolution Interferometer Sounder (HIS) was flown over Tennessee and northern Alabama during summer 1986. The HIS temperature and dewpoint soundings were examined on two flight days to determine their error characteristics and utility in mesoscale analyses. Random errors were calculated from structure functions while total errors were obtained by pairing the HIS soundings with radiosonde-derived profiles. Random temperature errors were found to be less than 1 C at most levels, but random dewpoint errors ranged from 1 to 5 C. Total errors of both parameters were considerably greater, with dewpoint errors especially large on the day having a pronounced subsidence inversion. Cumulus cloud cover on 15 June limited HIS mesoscale analyses on that day. Previously undetected clouds were found in many HIS fields of view, and these probably produced the low-level horizontal temperature and dewpoint variations observed in the retrievals. HIS dewpoints at 300 mb indicated a strong moisture gradient that was confirmed by GOES 6.7-micron imagery. HIS mesoscale analyses on 19 June revealed a tongue of humid air stretching across the study area. The moist region was confirmed by radiosonde data and imagery from the Multispectral Atmospheric Mapping Sensor (MAMS). Convective temperatures derived from HIS retrievals helped explain the cloud formation that occurred after the HIS overflights. Crude estimates of Bowen ratio were obtained from HIS data using a mixing-line approach. Values indicated that areas of large sensible heat flux were the areas of first cloud development. These locations were also suggested by GOES visible and infrared imagery. The HIS retrievals indicated that areas of thunderstorm formation were regions of greatest instability. Local landscape variability and atmospheric temperature and humidity fluctuations were found to be important factors in producing the cumulus clouds on 19 June. HIS soundings were capable of detecting some of this variability. The authors were impressed by HIS's performance on the two study days.

Fuelberg, Henry E.↗
NASA NTRS1992

Pilot interaction with cockpit automation - Operational experiences with the Flight Management System

Results are presented of two studies on the potential effect of cockpit automation on the pilot's performance, which provide data on pilots' difficulties with understanding and operating one of the core systems of cockpit automation, the Flight Management System (FMS). The results of both studies indicate that, although pilots do become proficient in standard FMS operations through ground training and subsequent flight experience, they still have difficulties tracking the FMS status and behavior in certain flight contexts and show gaps in the understanding of the functional structure of the system. The results suggest that design-related factors such as opaque interfaces contribute to these difficulties, which can affect the pilot's situation awareness.

Sarter, Nadine B.↗
NASA NTRS1993

Case-based approach to handling aircraft malfunctions

Reasoning about physical systems in operation is a difficult task, and any attempt to automate the process must overcome the problems of modeling normal behavior, diagnosing faults, and predicting future behavior. This paper describes a prototypical case-based reasoner (CBR) that operates in the domain of in-flight fault diagnosis and prognosis of aviation subsystems, particularly jet engines. The reasoner operates on the observation that the ability of a CBR program to reason about physical systems can be significantly enhanced by the addition to the CBR program of a model of the physical system to describe the system's structural, functional, and causal behavior.

Karamouzis, Stamos T.↗
NASA NTRS1985

Use of wind data in global modelling

The European Centre for Medium Range Weather Forecasts (ECMWF) is producing operational global analyses every 6 hours and operational global forecasts every day from the 12Z analysis. How the wind data are used in the ECMWF golbal analysis is described. For each current wind observing system, its ability to provide initial conditions for the forecast model is discussed as well as its weaknesses. An assessment of the impact of each individual system on the quality of the analysis and the forecast is given each time it is possible. Sometimes the deficiencies which are pointed out are related not only to the observing system itself but also to the optimum interpolation (OI) analysis scheme; then some improvements are generally possible through ad hoc modifications of the analysis scheme and especially tunings of the structure functions. Examples are given. The future observing network over the North Atlantic is examined. Several countries, coordinated by WMO, are working to set up an 'Operational WWW System Evaluation' (OWSE), in order to evaluate the operational aspects of the deployment of new systems (ASDAR, ASAP). Most of the new systems are expected to be deployed before January 1987, and in order to make the best use of the available resources during the deployment phase, some network studies are carried out at the present time, by using simulated data for ASDAR and ASAP systems. They are summarized.

Pailleux, J.↗
NASA NTRS1993

Cognitive engineering in aerospace application: Pilot interaction with cockpit automation

Because of recent incidents involving glass-cockpit aircraft, there is growing concern with cockpit automation and its potential effects on pilot performance. However, little is known about the nature and causes of problems that arise in pilot-automation interaction. The results of two studies that provide converging, complementary data on pilots' difficulties with understanding and operating one of the core systems of cockpit automation, the Flight Management System (FMS) is reported. A survey asking pilots to describe specific incidents with the FMS and observations of pilots undergoing transition training to a glass cockpit aircraft served as vehicles to gather a corpus on the nature and variety of FMS-related problems. The results of both studies indicate that pilots become proficient in standard FMS operations through ground training and subsequent line experience. But even with considerable line experience, they still have difficulties tracking FMS status and behavior in certain flight contexts, and they show gaps in their understanding of the functional structure of the system. The results suggest that design-related factors such as opaque interfaces contribute to these difficulties which can affect pilots' situation awareness. The results of this research are relevant for both the design of cockpit automation and the development of training curricula specifically tailored to the needs of glass cockpits.

Sarter, Nadine R.↗
NASA NTRS1993

Aeroelastic airfoil smart spar

Aircraft wings and rotor-blades are subject to undesirable bending and twisting excursions that arise from unsteady aerodynamic forces during high speed flight, abrupt maneuvers, or hard landings. These bending excursions can range in amplitude from wing-tip flutter to failure. A continuous-filament construction 'smart' laminated composite box-beam spar is described which corrects itself when subject to undesirable bending excursions or flutter. The load-bearing spar is constructed so that any tendency for the wing or rotor-blade to bend from its normal position is met by opposite twisting of the spar to restore the wing to its normal position. Experimental and theoretical characterization of these spars was made to evaluate the torsion-flexure coupling associated with symmetric lay-ups. The materials used were uniweave AS-4 graphite and a matrix comprised of Shell 8132 resin and U-40 hardener. Experimental tests were conducted on five spars to determine spar twist and bend as a function of load for 0, 17, 30, 45 and 60 deg fiber angle lay-ups. Symmetric fiber lay-ups do exhibit torsion-flexure couplings. Predictions of the twist and bend versus load were made for different fiber orientations in laminated spars using a spline function structural analysis. The analytical results were compared with experimental results for validation. Excellent correlation between experimental and analytical values was found.

Greenhalgh, Skott↗
NASA NTRS1993

NASA project 1: Full-body dynamometer

In space, where the body does only a fraction of work it does on earth, muscle atrophy is a major concern. The bones and the muscles will begin to deteriorate after a short stay in weightlessness. Bone decalcification appears to be a major problem with extensive living in microgravity. Resistance exercise is not only essential to prevent muscle atrophy in space, it also helps to keep bone decalcification in check. For a space station, where the astronauts are expected to live for months at a time, exercise is especially important. Experts recommend about an hour and a half to two hours of exercise per day to keep the muscles in good condition in microgravity. The exercises will not only keep the astronauts in excellent physical condition, it will also make it easier for them to readjust to earth's gravity on return. The stationary bicycle and the treadmill have been the astronauts' primary sources of exercise since the 1970's. The major problem with both the stationary bicycle and the treadmill is that while they may keep the leg muscles from deteriorating in microgravity, they do little for muscles in the upper body. The National Aeronautics and Space Administration (NASA) is currently developing a full-body dynamometer (FBD), which will provide the astronauts with a full-body workout. It will also test the astronauts for muscle atrophy and rehabilitate the weakened muscle. The specification and the function structure for the FBD is presented.

Lu, Li-Dai↗
NASA NTRS1993

Concepts and embodiment design of a reentry recumbent seating system for the NASA Space Shuttle

This report deals with the generation of a recumbent seating system which will be used by NASA to shuttle astronauts from the Russian space station Mir. We begin by examining the necessity for designing a special couch for the returning astronauts. Next, we discuss the operating conditions and constraints of the recumbent seating system and provide a detailed function structure. After working through the conceptual design process, we came up with ten alternative designs which are presented in the appendices. These designs were evaluated and weighted to systematically determine the best choice for embodiment design. A detailed discussion of all components of the selected system follows with design calculations for the seat presented in the appendices. The report concludes with an evaluation of the resulting design and recommendations for further development.

Mcmillan, Scott↗
NASA NTRS1994

CONFIG: Integrated engineering of systems and their operation

This article discusses CONFIG 3, a prototype software tool that supports integrated conceptual design evaluation from early in the product life cycle, by supporting isolated or integrated modeling, simulation, and analysis of the function, structure, behavior, failures and operations of system designs. Integration and reuse of models is supported in an object-oriented environment providing capabilities for graph analysis and discrete event simulation. CONFIG supports integration among diverse modeling approaches (component view, configuration or flow path view, and procedure view) and diverse simulation and analysis approaches. CONFIG is designed to support integrated engineering in diverse design domains, including mechanical and electro-mechanical systems, distributed computer systems, and chemical processing and transport systems.

Malin, Jane T.↗
NASA NTRS1992

Measurement of two-dimensional fluid flow by digital correlation of scattered light

Digital correlation is a pattern matching procedure. This procedure has recently been used in two-dimensional fluid flow measurements. Two images of a seeded fluid are taken and the intensity distribution of a small window in the first image is matched in the second image using a statistical correlation method. A series of structure functions have been implemented to improve the accuracy and reliability of the correlation method and new algorithms have been developed to reduce the time required for the correlation computations.

Matthys, Donald R.↗
NASA NTRS1994

Finite element analysis of a composite wheelchair wheel design

The finite element analysis of a composite wheelchair wheel design is presented. The design is the result of a technology utilization request. The designer's intent is to soften the riding feeling by incorporating a mechanism attaching the wheel rim to the spokes that would allow considerable deflection upon compressive loads. A finite element analysis was conducted to verify proper structural function. Displacement and stress results are presented and conclusions are provided.

Ortega, Rene↗
NASA NTRS1994

Proposal for the design of a zero gravity tool storage device

Astronauts frequently use a variety of hand tools during space missions, especially on repair missions. A toolbox is needed to allow storage and retrieval of tools with minimal difficulties. The toolbox must contain tools during launch, landing, and on-orbit operations. The toolbox will be used in the Shuttle Bay and therefore must withstand the hazardous space environment. The three main functions of the toolbox in space are: to protect the tools from the space environment and from damaging one another, to allow for quick, one-handed access to the tools; and to minimize the heat transfer between the astronaut's hand and the tools. This proposal explores the primary design issues associated with the design of the toolbox. Included are the customer and design specifications, global and refined function structures, possible solution principles, concept variants, and finally design recommendations.

Stuckwisch, Sue↗
NASA NTRS1994

Experimental and numerical study of the intermittency exponent mu

After publication of the Kolmogorov refined similarity hypotheses, the small-scale intermittency of the energy dissipation field became a central problem in fully developed turbulence (FDT). This phenomenon has been studied in many different ways, e.g. by searching for corrections to scaling exponents in the inertial range velocity structure functions. A direct measure of this intermittency is, however, available by studying the local rate of energy dissipation, and it may be quantitatively characterized by the intermittency exponent mu. As far as we know, nobody has posed an obvious question: Is the intermittency exponent mu a unique constant, i.e., are the values mu(sub kappa), mu(sub epsilon), mu(sub r), mu(sub b), and mu(sub e) the same at high Reynolds numbers, or do they create a set of different (and perhaps independent) exponents? This paper addresses the above question using the high Reynolds number experiments.

Praskovsky, Alexander↗