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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A perspective on technical needs in computational structures technology

The wide spectrum of needs and applications are demonstrated of computational structural mechanics. The spectrum ranges from micro structural mechanics to the optimization of the performance of aerovehicles. Critical high leveraged technologies will require engineering process modernization and automation, affordable structures and materials, and advanced computational technology. Recent advances at Rockwell International in computational structural mechanics addressed these issues and improve the ability to achieve advanced aircraft objectives.

Abdi, Frank F.↗
NASA NTRS1992

Study of turbulence structure through numerical simulations: The perspective of drag and reduction

The first part of this note concerns organized structures in the near-wall region of a turbulent boundary layer. A particular emphasis is given to those organized motions believed to be responsible for the turbulence production process in the wall region, and hence, indirectly responsible for the viscous drag. Examples are selected to illustrate how the analyses of numerically generated databases have contributed to improve our understanding of the organized structures of turbulent boundary layers. In the second part, results from an exploratory study based on the direct numerical simulation of the concepts for active control of turbulent boundary layers are presented. A significant drag reduction is achieved when the surface boundary condition is modified such that it could suppress the organized motion in the wall region. This drag reduction is accompanied by a significant reduction in the intensity of the organized structures and in the magnitude of Reynolds stresses throughout the flow.

Kim, J. J.↗
NASA NTRS1991

Inspection of aging aircraft: A manufacturer's perspective

Douglas, in conjunction with operators and regulators, has established interrelated programs to identify and address issues regarding inspection of aging aircraft. These inspection programs consist of the following: Supplemental Inspection Documents; Corrosion Prevention and Control Documents; Repair Assessment Documents; and Service Bulletin Compliance Documents. In addition, airframe manufacturers perform extended airframe fatigue tests to deal with potential problems before they can develop in the fleet. Lastly, nondestructive inspection (NDI) plays a role in all these programs through the detection of cracks, corrosion, and disbonds. However, improved and more cost effective NDI methods are needed. Some methods such as magneto-optic imaging, electronic shearography, Diffractor-Sight, and multi-parameter eddy current testing appear viable for near-term improvements in NDI of aging aircraft.

Aging Aircraft↗
NASA NTRS1990

Statistically based material properties: A military handbook-17 perspective

This paper describes statistical procedures and their importance in obtaining composite material property values in designing structures for aircraft and military combat systems. The property value is such that the strength exceeds this value with a prescribed probability with 95% confidence in the assertion. The survival probabilities are the 99th percentile and 90th percentile for the A and B basis values respectively. The basis values for strain to failure measurements are defined in a similar manner. The B value is the primary concern of this paper.

Donald M. Neal↗
NASA NTRS1992

Nuclear Thermal Rocket by 2000: a DOE Perspective

It is asserted that a Nuclear Propulsion Space Transportation System is required for the Manned Mars Mission. Additionally, it is felt that a Nuclear Propulsion Space Transportation System can support a wide variety of future space missions, including lunar base implementation and support. The Rover/NERVA program demonstrated that a safe, reliable Nuclear Thermal Rocket (NTR) can be developed and operated for sufficient run times, at desirable temperatures, and with multiple restarts. The discussion is presented in viewgraph form.

Howe, Steven D.↗
NASA NTRS1992

Perspectives on hypersonic viscous and nonequilibrium flow research

An attempt is made to reflect on current focuses in certain areas of hypersonic flow research by examining recent works and their issues. Aspects of viscous interaction, flow instability, and nonequilibrium aerothermodynamics pertaining to theoretical interest are focused upon. The field is a diverse one, and many exciting works may have either escaped the writer's notice or been abandoned for the sake of space. Students of hypersonic viscous flow must face the transition problems towards the two opposite ends of the Reynolds or Knudsen number range, which represents two regimes where unresolved fluid/gas dynamic problems abound. Central to the hypersonic flow studies is high-temperature physical gas dynamics; here, a number of issues on modelling the intermolecular potentials and inelastic collisions remain the obstacles to quantitative predictions. Research in combustion and scramjet propulsion will certainly be benefitted by advances in turbulent mixing and new computational fluid dynamics (CFD) strategies on multi-scaled complex reactions. Even for the sake of theoretical development, the lack of pertinent experimental data in the right energy and density ranges is believed to be among the major obstacles to progress in aerothermodynamic research for hypersonic flight. To enable laboratory simulation of nonequilibrium effects anticipated for transatmospheric flight, facilities capable of generating high enthalpy flow at density levels higher than in existing laboratories are needed (Hornung 1988). A new free-piston shock tunnel capable of realizing a test-section stagnation temperature of 10(exp 5) at Reynolds number 50 x 10(exp 6)/cm is being completed and preliminary tests has begun (H. Hornung et al. 1992). Another laboratory study worthy of note as well as theoretical support is the nonequilibrium flow experiment of iodine vapor which has low activation energies for vibrational excitation and dissociation, and can be studied in a laboratory with modest resources (Pham-Van-Diep et al. 1992).

Cheng, H. K.↗
NASA NTRS1991

Operational perspectives for performing microgravity science in orbit

The combination of automation and operator-based technologies is discussed with respect to orbital microgravity experiments in order to optimize the performance and results. A list of five design objectives is presented, and each item is examined in terms of on-orbit flight history to identify relevant examples. It is suggested that human factors be considered in hardware design and that in-flight maintenance operations be considered an integral part of a program. The operational design can produce more effective results when it is established for 'failures' and mission success operations. The design must also be approached in terms of both the limitations and advantages of microgravity. The overarching theme of the investigation is that the mix of automation and operator interaction should be optimized by automating routine tasks and using the operator for critical assessments.

Dunbar, Bonnie J.↗
NASA NTRS1992

History of water on Mars - A biological perspective

A general scenario is developed for the history of liquid water on the surface of Mars, according to which the history of water on Mars can be divided into four epochs based on the fundamental temperature and pressure characteristics. In Epoch I, the mean annual temperature is assumed to have been above freezing and the pressure to have been above 1 atm; liquid water was widespread and life could have arisen and become abundant. In Epoch II, the mean annual temperature fell below freezing, but peak temperatures were above freezing; In Epoch II ice-covered lakes could have provided a habitat for life. In Epoch III, both the mean and the peak temperatures were below freezing, and only transient liquid water would be possible; under these conditions, microbial ecosystems living in endolithic rock 'greenhouses' could have continued to survive. Finally, in Epoch IV, the pressure dropped to near the triple point pressure of water; at this stage, life on the surface of Mars would have become extinct.

Mckay, Christopher P.↗
NASA NTRS1992

Information processing in the primate visual system - An integrated systems perspective

The primate visual system contains dozens of distinct areas in the cerebral cortex and several major subcortical structures. These subdivisions are extensively interconnected in a distributed hierarchical network that contains several intertwined processing streams. A number of strategies are used for efficient information processing within this hierarchy. These include linear and nonlinear filtering, passage through information bottlenecks, and coordinated use of multiple types of information. In addition, dynamic regulation of information flow within and between visual areas may provide the computational flexibility needed for the visual system to perform a broad spectrum of tasks accurately and at high resolution.

Van Essen, David C.↗
NASA NTRS1992

Future experimental needs to support applied aerodynamics - A transonic perspective

Advancements in facilities, test techniques, and instrumentation are needed to provide data required for the development of advanced aircraft and to verify computational methods. An industry survey of major users of wind tunnel facilities at Langley Research Center (LaRC) was recently carried out to determine future facility requirements, test techniques, and instrumentation requirements; results from this survey are reflected in this paper. In addition, areas related to transonic testing at LaRC which are either currently being developed or are recognized as needing improvements are discussed.

Gloss, Blair B.↗
NASA NTRS1992

The NASA airborne astronomy program - A perspective on its contributions to science, technology, and education

The publication records from NASA's airborne observatories are examined to evaluate the contribution of the airborne astronomy program to technological development and scientific/educational progress. The breadth and continuity of program is detailed with reference to its publication history, discipline representation, literature citations, and to the ability of such a program to address nonrecurring and unexpected astronomical phenomena. Community involvement in the airborne-observation program is described in terms of the number of participants, institutional affiliation, and geographic distribution. The program utilizes instruments including heterodyne and grating spectrometers, high-speed photometers, and Fabry-Perot spectrometers with wide total spectral ranges, resolutions, and numbers of channels. The potential of the program for both astronomical training and further scientific, theoretical, and applied development is underscored.

Larson, Harold P.↗
NASA NTRS1992

The tracking and data relay satellite system - An historical perspective

The Tracking and Data Relay Satellite System (TDRSS), NASA's primary communications link between near-earth orbiting spacecraft and the ground, is addressed. The TDRSS supporting elements and their roles are described along with the different phases of the TDRSS life cycle. Users of TDRSS and the extent of support given to them are shown. TDRSS performance is evaluated in terms of availability and service proficiency.

Elwell, Daniel W.↗
NASA NTRS1991

Mission to Planet Earth - The ecological perspective

The components of Mission to Planet Earth, the coordinated international plan to provide satellite platforms, instruments, data and information systems, and related scientific research to the International Geosphere-Biosphere Program (IGBP) are described. Emphasis is given to those aspects of direct relevance to ecology. An attempt is made to discriminate between those applications of remote sensing that are known to be possible and those that are believed to be possible.

Wickland, Diane E.↗
NASA NTRS1992

The early evolution of eukaryotes - A geological perspective

This paper examines the goodness of fit between patterns of biological and environmental history implied by molecular phylogenies of eukaryotic organisms and the geological records of early eukaryote evolution. It was found that Precambrian geological records show evidence that episodic increases in biological diversity roughly coincided with episodic environmental changes and by sharp increases in atmospheric oxygen concentrations which significantly changed the earth surface environments. Although the goodness of fit among physical and biological changes is gratifyingly high, the records of these changes do not always coincide in time. The additional information in these fields that is needed for complete integration of geological and phylogenic records is suggested.

Knoll, Andrew H.↗
NASA NTRS1992

Reducing the complexity of software systems - A strategic software perspective

The results of a combined management and technical initiative aimed at reducing the size and complexity associated with developing operations planning, scheduling, and resource management software systems are presented. The initiative has produced operations concepts, functional requirements, system architectures, a comprehensive lexicon, and software tools to revolutionize the traditional software technology and development practices for planning, scheduling, and resource management systems used in space operations control centers. Examples of technology and practices to reduce complexity include a method for projecting design consequences from an operations concept, a universal architecture for heuristic algorithms, an object-oriented framework for describing large classes of problems that parametrically adapt to all domain peculiarities, the identification of general approaches which respond to changes with minimum impact on systems implementations, and a management structure for prototyping to minimize the risks of ill-conceived designs.

Hornstein, Rhoda S.↗
NASA NTRS1991

Information management for commercial aviation - A research perspective

The problem of flight deck information management (IM), defined as processing, controlling, and directing information, for commercial flight decks, and a research effort underway to address this problem, are discussed. The premises provided are utilized to lay the groundwork required for such research by providing a framework to describe IM problems and an avenue to follow when investigating solution concepts. The research issues presented serve to identify specific questions necessary to achieve a better understanding of the IM problem, and to provide assessments of the relative merit of various solution concepts.

Ricks, Wendell R.↗
NASA NTRS1991

Diverter - Perspectives on the integration and display of flight critical information using an expert system and menu-driven displays

An expert system prototype, called Diverter, was developed which evaluates, integrates, and displays flight plan recommendations to the pilot during the planning of an inflight diversion. The system integrates information from many sources to provide a comprehensive description of the flight planning alternatives available to the pilot. Diverter evaluates all applicable constraints to arrive at a flight plan to make efficient use of manpower, fuel, and time. The use of an expert system automates much of the integration and evaluation of variables impacting the flight. The use of hierarchical menu-driven displays and direct manipulation interface techniques may reduce workload.

Rudolph, Frederick M.↗