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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Note on the eigensolution of a homogeneous equation with semi-infinite domain

The 'variation-iteration' method using Green's functions to find the eigenvalues and the corresponding eigenfunctions of a homogeneous Fredholm integral equation is employed for the stability analysis of fluid hydromechanics problems with a semiinfinite (infinite) domain of application. The objective of the study is to develop a suitable numerical approach to the solution of such equations in order to better understand the full set of equations for 'real-world' flow models. The study involves a search for a suitable value of the length of the domain which is a fair finite approximation to infinity, which makes the eigensolution an approximation dependent on the length of the interval chosen. In the examples investigated y = 1 = a seems to be the best approximation of infinity; for y greater than unity this method fails due to the polynomial nature of Green's functions.

Wadia, A. R.↗
NASA NTRS1981

A new trajectory concept for exploring the earth's geomagnetic tail

An innovative trajectory technique for a magnetotail mapping mission is described which can control the apsidal rotation of an elliptical earth orbit and keep its apogee segment inside the tail region. The required apsidal rotation rate of approximately 1 deg/day is achieved by using the moon to carry out a prescribed sequence of gravity-assist maneuvers. Apogee distances are alternately raised and lowered by the lunar-swingby maneuvers; several categories of the 'sun-synchronous' swingby trajectories are identified. The strength and flexibility of the new trajectory concept is demonstrated by using real-world simulations showing that a large variety of trajectory shapes can be used to explore the earth's geomagnetic tail between 60 and 250 R sub E.

Farquhar, R. W.↗
NASA NTRS1982

A system safety model for developmental aircraft programs

Basic tenets of safety as applied to developmental aircraft programs are presented. The integration of safety into the project management aspects of planning, organizing, directing and controlling is illustrated by examples. The basis for project management use of safety and the relationship of these management functions to 'real-world' situations is presented. The rationale which led to the safety-related project decision and the lessons learned as they may apply to future projects are presented.

Amberboy, E. J.↗
NASA NTRS1981

Survey of residential and intermediate photovoltaic applications

The construction and operation of residential and intermediate size photovoltaic power systems as performed by the DOE Photovoltaics Program are reviewed. The program is directed toward the development of economically competitive, commercially available, photovoltaic power systems to provide safe and reliable energy for a wide range of applications. Systems which are currently operational or in construction range in size from 5 kWp to 225 kWp, and real-world testing is being pursued with residential, industrial, institutional, and commercial systems to establish their feasibility and readiness for commercialization.

Hesse, J. L.↗
NASA NTRS1981

University/industry collaboration in remote sensing education

A graduate level course covering the development and structure of geographical information systems and the acquisition and processing of LANDSAT data for input to these systems is described. A portion of the course was devoted to hands-on classification of LANDSAT digital tapes utilizing both university and private industry processing systems. This industry/university collaboration was extremely successful and resulted in a high quality course. It gave the students an excellent experience in working in a real-world client/consultant relationship undertaken to accomplish a specific task. There were two key factors in the success of the collaboration. First, there was a very careful product definition and advance meetings between the University faculty and the company personnel to be involved. Second, the students were not taken into the industrial facility until late in the course, after they had a reasonable knowledge of the physical bases of remote sensing, the concept of spectral signatures, and the fundamentals of pattern analysis.

Ragan, R. M.↗
NASA NTRS1983

Crater ejecta scaling laws - Fundamental forms based on dimensional analysis

Self-consistent scaling laws are developed for meteoroid impact crater ejecta. Attention is given to the ejection velocity of material as a function of the impact point, the volume of ejecta with a threshold velocity, and the thickness of ejecta deposit in terms of the distance from the impact. Use is made of recently developed equations for energy and momentum coupling in cratering events. Consideration is given to scaling of laboratory trials up to real-world events and formulations are developed for calculating the ejection velocities and ejecta blanket profiles in the gravity and strength regimes of crater formation. It is concluded that, in the gravity regime, the thickness of an ejecta blanket is the same in all directions if the thickness and range are expressed in terms of the crater radius. In the strength regime, however, the ejecta velocities are independent of crater size, thereby allowing for asymmetric ejecta blankets. Controlled experiments are recommended for the gravity/strength transition.

Housen, K. R.↗
NASA NTRS1984

The National Transonic Facility - A research perspective

The capabilities of the National Transonic Facility (NTF) at NASA-Langley and its impact on aerodynamics investigations are surveyed. The fan-driven, closed-circuit transonic wind tunnel has an 8.2 sq ft slotted test section. Trials can be run from Mach 0.2-1.2, pressures of 1-8.9 atm, and temperatures of -320 to 150 F using nitrogen as the working gas. Instrumentation has been developed for monitoring force, pressure, attitude, deformation, temperature, skin friction, flow transition, and flow velocity as well as visualizing flows around the models. Pressures of 15-130 psi are available, as are Re up to 120 million at Mach 1. Correlations are being made with flight data from the Shuttle, 767, X-29A, and TACT aircraft for real-world extrapolations. The NTF, when combined with computational fluid dynamics techniques, will permit testing of aerodynamically sophisticated shapes while narrowing the design goals for each model during basic research in fluid mechanics, transport, and aerodynamic phenomena.

Campbell, J. F.↗
NASA NTRS1986

Universal Noiseless Coding Subroutines

Software package consists of FORTRAN subroutines that perform universal noiseless coding and decoding of integer and binary data strings. Purpose of this type of coding to achieve data compression in sense that coded data represents original data perfectly (noiselessly) while taking fewer bits to do so. Routines universal because they apply to virtually any "real-world" data source.

Schlutsmeyer, A. P.↗
NASA NTRS1986

Levels of Information Processing in a Fitts law task (LIPFitts)

State-of-the-art flight technology has restructured the task of human operators, decreasing the need for physical and sensory resources, and increasing the quantity of cognitive effort required, changing it qualitatively. Recent technological advances have the most potential for impacting a pilot in two areas: performance and mental workload. In an environment in which timing is critical, additional cognitive processing can cause performance decrements, and increase a pilot's perception of the mental workload involved. The effects of stimulus processing demands on motor response performance and subjective mental workload are examined, using different combinations of response selection and target acquisition tasks. The information processing demands of the response selection were varied (e.g., Sternberg memory set tasks, math equations, pattern matching), as was the difficulty of the response execution. Response latency as well as subjective workload ratings varied in accordance with the cognitive complexity of the task. Movement times varied according to the difficulty of the response execution task. Implications in terms of real-world flight situations are discussed.

Mosier, K. L.↗
NASA NTRS1985

Simulation studies of the impact of future observing systems on weather prediction

The features and preliminary results from a simulation system being implemented to develop realistic estimates of the impacts future data acquisition systems will have on large-scale numerical weather simulation are described. The new instruments may include advanced passive IR and microwave satellite sensors, as well as active scatterometer and lidar sounders. A main goal of the impact study is to identify those sensor systems which will provide the most benefit. The realism of the study is being enhanced by assimilating as much real-world data as possible and generating global weather maps for comparison with maps generated on the bases on the projected new, higher resolution data. Early results have indicated a preference for higher resolution wind data than for temperature data for making 1-5 day forecasts. The prime instrument candidate for collecting the data is lidar, provided the sensor resolution design goals are met.

Atlas, R.↗
NASA NTRS1985

Physical processes in prediction of explosive maritime cyclogenesis

Explosive maritime cyclogenetic events are usually aligned with the warm currents off the east coasts of Japan and the U.S. One such event occurred during FGGE in an area which featured good instrumented ship and aircraft coverage. The UCLA 4th order GMC was employed to generate predictions of the event for comparisons with the real-world data. FGGE III-b data were used to initialize the model calculations. Attention was directed to the physical processes causing the onset of the cyclogenesis, particularly the heat budgets of the fluxes involved. The diabatic heating was observed to be equivalent to the horizontal temperature advection. The main source of energy around the cyclone center was identified as the conversion of energy from static energy to kinetic energy. Further analyses of similar events are required if the present results are to be validated.

Liou, C.-S.↗
NASA NTRS1986

An additional source of uncertainty and bias in digital spectral estimates near the Nyquist frequency

An additional source of bias and uncertainty in digital spectral estimates near the Nyquist frequency is discovered which is produced by the fact that the finite width main lobe of the spectral window is periodic with period of 2(omega sub c), equal to 4pi times the Nyquist frequency. For estimates near omega sub c, contributions from frequencies near -(omega sub c) are found to appear even for a sufficiently sampled bandlimited time history. In real-world applications, this source should be significant if the number of data points is small, and it should be of even more importance if the signal is not strictly bandlimited.

Hardin, J. C.↗
NASA NTRS1986

Artificial intelligence planning applications for space exploration and space robotics

Mission sequencing involves the plan for actuation of the experiments to be conducted aboard a spacecraft; automation is under study by NASA as a means to reduce time and manpower costs in mission planning and in robotic implementation. The development of a mission sequence is conditioned by the limited duration of advantageous spacecraft encounters with objects of study, more research requests than can be satisfied, and requested changes in objectives. Autonomous robot development is hampered by the absence of task-level programming languages, the existence of anomalies in real-world interactions, and a lack of required capabilities in current sensor technology.

Rokey, Mark↗
NASA NTRS1988

Event-related brain potentials as indices of mental workload and attentional allocation

Over the past decade considerable strides were made in explicating the antecedant conditions necessary for the elicitation, and the modulation of the amplitude and latency, of a number of components of the event-related brain potential (ERP). The focus of this report is on P300. The degree to which the psychophysiological measures contribute to issues in two real-world domains (communication devices for the motor impaired and the assessment of mental workload of aircraft pilots) are examined.

Arthur F Krainer↗
NASA NTRS1988

A simple, analytic 3-dimensional downburst model based on boundary layer stagnation flow

A simple downburst model is developed for use in batch and real-time piloted simulation studies of guidance strategies for terminal area transport aircraft operations in wind shear conditions. The model represents an axisymmetric stagnation point flow, based on velocity profiles from the Terminal Area Simulation System (TASS) model developed by Proctor and satisfies the mass continuity equation in cylindrical coordinates. Altitude dependence, including boundary layer effects near the ground, closely matches real-world measurements, as do the increase, peak, and decay of outflow and downflow with increasing distance from the downburst center. Equations for horizontal and vertical winds were derived, and found to be infinitely differentiable, with no singular points existent in the flow field. In addition, a simple relationship exists among the ratio of maximum horizontal to vertical velocities, the downdraft radius, depth of outflow, and altitude of maximum outflow. In use, a microburst can be modeled by specifying four characteristic parameters, velocity components in the x, y and z directions, and the corresponding nine partial derivatives are obtained easily from the velocity equations.

Oseguera, Rosa M.↗
NASA NTRS1986

Assessment of pilot workload - Converging measures from performance based, subjective and psychophysiological techniques

This study explores the relationship between the P300 component of the event-related brain potential (ERP) and the processing demands of a complex real-world task. Seven male volunteers enrolled in an Instrument Flight Rule (IFR) aviation course flew a series of missions in a single engine fixed-based simulator. In dual task conditions subjects were also required to discriminate between two tones differing in frequency. ERPs time-locked to the tones, subjective effort ratings and overt performance measures were collected during two 45 min flights differing in difficulty (manipulated by varying both atmospheric conditions and instrument reliability). The more difficult flight was associated with poorer performance, increased subjective effort ratings, and smaller secondary task P300s. Within each flight, P300 amplitude was negatively correlated with deviations from command headings indicating that P300 amplitude was a sensitive workload metric both between and within the flight missions.

Kramer, Arthur F.↗
NASA NTRS1987

Real-time operational planning for the U.S. air traffic system

This paper describes an integrated planning model for the U.S. air traffic system. The approach incorporates the dual objectives of monitoring collision risk while minimizing transportation costs. Specialized solution algorithms exploit the underlying structure of the model - especially for large-scale examples. The proposed formulation is tested with real-world data for the Indianapolis control sector. Additional experiments with a CRAY X-MP/24 supercomputer show that a full-scale model can be solved under real time conditions. Despite these advances, additional work is required in developing a practical system. Suggestions are made for combining advances in computer graphics and mathematical modeling.

Mulvey, John M.↗
NASA NTRS1988

Optical pseudocolor image enhancement with real-time large screen display

A real-time broadband pseudocolor image enhancement technique using a liquid crystal television spatial light modulator (LCTV SLM) is described. Three different schemes to modulate the gray-scale disribution of an input scene by an LCTV SLM through varying the orientations of its analyzer are presented. These schemes are incorporated into a compact white light optical projection system that is able to display, on a large screen, broadband pseudocolor images of real-world input scenes. Experimental results demonstrating the feasibility of the technique are reported.

Chao, Tien-Hsin↗