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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 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Composites for Increased Wear Resistance: Current Achievements and Future Prospects

The various ways in which reductions in wear and/or friction can be achieved by the use of composite materials are reviewed. Reinforced plastics are emphasized and it is shown that fillers and fibers reduce wear via several mechanisms additional to their role of increasing overall mechanical strength, preferential transfer, counter face abrasion, preferential load support, or third-body formation on either the composite or its counterface. Examples are given from recent work on thin layer composites of the type widely used as dry bearings in aircraft flight control mechanisms. Developments in metal based composites and carbon-carbon composites for high energy brakes are discussed. The aspects which could benefit by increased fundamental understanding identified and the types of composites which appear to have greatest potential for further growth are indicated.

Lancaster, J. K.↗
NASA NTRS1984

DSS 13 Microprocessor Antenna Controller

A microprocessor based antenna controller system developed as part of the unattended station project for DSS 13 is described. Both the hardware and software top level designs are presented and the major problems encounted are discussed. Developments useful to related projects include a JPL standard 15 line interface using a single board computer, a general purpose parser, a fast floating point to ASCII conversion technique, and experience gained in using off board floating point processors with the 8080 CPU.

Gosline, R. M.↗
NASA NTRS1981

Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Wing planform study and final configuration selection

This report summarizes the Wing Planform Study Task and Final Configuration Selection of the Integrated Application of Active Controls (IAAC) Technology Project within the Energy Efficient Transport Program. Application of Active Controls Technology (ACT) in combination with increased wing span resulted in significant improvements over the Conventional Baseline Configuration (Baseline) and the Initial ACT Configuration previously established. The configurations use the same levels of technology (except for ACT), takeoff gross weight, and payload as the Baseline. The Final ACT Configuration (Model 768-107) incorporates pitch-augmented stability (which enabled an approximately 10% aft shift in cruise center of gravity and a 45% reduction in horizontal tail sizes), lateral/directional-augmented stability, an angle-of-attack limiter, and wing-load alleviation. Flutter-mode control was not beneficial for this configuration. This resulted in an 890 kg (1960 lb) reduction in airplane takeoff gross weight and a 9.8% improvement in cruise lift/drag. At the Baseline mission range (3590 km) (1938 nmi), this amounts to 10% block fuel reduction. Good takeoff performance at high-altitude airports on a hot day was also achieved. Results of this task strongly indicate that the IAAC Project should proceed with the Final ACT evaluation and begin the required control system development and testing.

Source record↗
NASA NTRS1983

Environmental, health and safety assessment of photovoltaics

The environmental, health, and safety (E, H and S) concerns associated with the fabrication, deployment, and decommissioning of photovoltaic (PV) systems in terrestial applications are identified and assessed. Discussion is limited to crystalline silicon technologies. The primary E, H, and S concerns that arise during collector fabrication are associated with occupational exposure to materials of undetermined toxicity or to materials that are known to be hazardous, but for which process control technology may be inadequate. Stricter exposure standards are anticipated for some materials and may indicate a need for further control technology development. Minimizing electric shock hazards is a significant concern during system construction, operation and maintenance, and decommissioning.

Rose, E. C.↗
NASA NTRS1985

Design evolution of the orbiter reaction control subsystem

The challenges of space shuttle orbiter reaction control subsystem development began with selection of the propellant for the subsystem. Various concepts were evaluated before the current Earth storable, bipropellant combination was selected. Once that task was accomplished, additional challenges of designing the system to satisfy the wide range of requirements dictated by operating environments, reusability, and long life were met. Verification of system adequacy was achieved by means of a combination of analysis and test. The studies, the design efforts, and the test and analysis techniques employed in meeting the challenges are described.

Taeber, R. J.↗
NASA NTRS1985

Lithologic and Structural Control on Slope Morphology in the Valles Marineris

Throughout the Valles Marineris scarp morphology varies as a function of lithology, structure and scarp height. In addition lithology is an important control on permeability and the relative importance of spring sapping processes. Geomorphic mapping of distinct subareas can be used to define the characteristic scarp forms. Distinct morphologic zones defined on the basis of regional variations in lithology are described. Lithology and tectonic history are shown to be the two most important factors controlling slope development. Regional variation in scarp morphology can be correlated with the orientation and density of fracture systems; scarp height and the presence of rejuvenated fault scarps; and the thickness and degree of exposure of presumably less competent, more permeable, water saturated crated plateau material in the chasmata scarps.

Patton, P. C.↗
NASA NTRS1983

Operational results for the experimental DOE/NASA Mod-OA wind turbine project

The Mod-OA wind turbine project which was to gain early experience in the operation of large wind turbines in a utility environment is discussed. The Mod-OA wind turbines were a first generation design, and even though not cost effective, the operating experience and performance characteristics had a significant effect on the design and development of the second and third generation machines. The Mod-OA machines were modified as a result of the operational experience, particularly the blade development and control system strategy. The results of study to investigate the interaction of a Mod-OA wind turbine with an isolated diesel generation system are discussed. The machine configuration, its advantages and disadvantages and the machine performance and availability are discussed.

Shaltens, R. K.↗
NASA NTRS1985

A three-dimensional turbulent boundary layer undergoing transverse strain and streamwise pressure gradient

Results from an experimental investigation designed to provide data on both mean and turbulence quantities in the axisymmetric, swirling boundary layer (with and without pressure gradient) flowing over a stationary cylinder downstreams of a spinning cylindrical section are presented. The pressure gradient was introduced into the flow field by a 25.4 mm-high, forward-facing, circular step mounted on the stationary cylinder, the step height being nearly equal to the thickness of the approaching boundary layer. All the measurements were made at a nominal upstream reference Reynolds number of 2.4 x 10 to the 6th power/m (corresponding to an upstream reference velocity of 36 to 37 m/sec) with the rotation of the spinner set to make its peripheral speed equal the reference velocity. The data reported included measurements of surface pressure and the mean surface shear-stress vector taken with a miniature, directional, surface-fence gage. These measurements were supplemented by oil-flow visualization studies of the stationary cylinder. The data indicates that the streamwise pressure gradient controls the development of the streamwise component of wall shear, but leaves the peripheral component of wall shear practically unaffected.

Hebbar, S. K.↗
NASA NTRS1985

Integratable propulsion systems for the Space Station

Oxygen/hydrogen propulsion system options for space station orbit maintenance and attitude control were developed and evaluated relative to monopropellant and storable bipropellant propulsion systems. Space station propulsion requirements were analyzed with reference to such considerations as station size, altitude, power, crew size, and orbit transfer vehicle and orbital maneuvering vehicle servicing requirements. The evolutionary growth of oxygen/hydrogen bipropellant propulsion as an integral part of several interrelated space station functions, e.g., life support, power, and thermal management was considered. Propellant resupply evolves from resupply based on transport of liquid oxygen and liquid hydrogen to water. The advantages of the operation of the space station based on an oxygen/hydrogen economy are presented and discussed.

Rosenberg, S. D.↗
NASA NTRS1984

Atmosphere behavior in gas-closed mouse-algal systems - An experimental and modelling study

A NASA-sponsored research program initiated using mathematical modelling and laboratory experimentation aimed at examining the gas-exchange characteristics of artificial animal/plant systems closed to the ambient atmosphere is studied. The development of control techniques and management strategies for maintaining the atmospheric levels of carbon dioxide and oxygen at physiological levels is considered. A mathematical model simulating the behavior of a gas-closed mouse-algal system under varying environmental conditions is described. To verify and validate the model simulations, an analytical system with which algal growth and gas exchange characteristics can be manipulated and measured is designed, fabricated, and tested. The preliminary results are presented.

Averner, M. M.↗
NASA NTRS1984

Space Station active thermal control technical considerations

A description of recent and planned thermal control technology developments at the Johnson Space Center and the other NASA Centers in support of Space Stations is presented. The program is centered around satisfying the needs of the users. Preliminary results of proof-of-concept high capacity heat pipes and two-phase devices are included which indicate that large amounts of energy (100 kW) can be transported long distances (50 m) with very small temperature differences. The presentation summarizes preparations for an 'evolutionary test bed' for advanced development of thermal technology which will provide data on components and systems for incorporation into the Space Station designs in the late 1980s. The results of the recently flown Heat Pipe Experiment aboard STS-8 are presented.

Ellis, W. E.↗
NASA NTRS1985

An experimental investigation of a swirling, axisymmetric, turbulent boundary layer with pressure gradient

The results of an experimental investigation designed to document data on both mean and turbulence quantities in the axisymmetric, swirling boundary layer (with and without a pressure gradient) flowing over a stationary cylinder downstream of a spinning cylindrical section are discussed. The pressure gradient was introduced into the flow field by a 25.4-mm-high, forward-facing circular step mounted on the stationary cylinder, the step height being nearly equal to the approaching boundary-layer thickness. All the measurements were made at upstream reference velocity of 36-37 m/sec, with the rotation of the spinner set to make its peripheral speed equal to the reference velocity. The data reported include measurements of surface pressure and the mean surface-shear-stress vector (using a miniature directional surface-fence gage) and oil-flow visualization studies of the stationary cylinder. The data indicate that the streamwise pressure gradient controls the development of the streamwise component of wall shear but leaves the peripheral component of wall shear practically unaffected.

Hebbar, S. K.↗
NASA NTRS1986

Fast Remote Kilovolt-Power Controller

High power turned off rapidly in case of overload. Remote power controller (RPC) developed with power-handling capability of 25 A at 1,000 Vdc. RPC has programmable characteristic that trip open to clear fault within 3 microseconds.

Hower, P.↗
NASA NTRS1986

CELSS science needs

Questions and areas of study that need to be persued in order to develope a Controlled Ecological Life Support System are posed. Research topics needing attention are grouped under various leadings: ecology, genetics, plant pathology, cybernetics, chemistry, computer science, fluid dynamics, optics, and solid-state physics.

Rummel, J. D.↗
NASA NTRS1986

Decoupling control synthesis for an oblique-wing aircraft

Interest in oblique-wing aircraft has surfaced periodically since the 1940's. This concept offers some substantial aerodynamic performance advantages but also has significant aerodynamic and inertial cross-coupling between the aircraft longitudinal and lateral-directional axes. This paper presents a technique for synthesizing a decoupling controller while providing the desired stability augmentation. The proposed synthesis procedure uses the concept of a real model-following control system. Feedforward gains are selected on the assumption that perfect model-following conditions are satisfied. The feedback gains are obtained by using eigensystem assignment, and the aircraft is stabilized by using partial state feedback. The effectiveness of the control laws developed in achieving the desired decoupling is illustrated by application to linearized equations of motion of an oblique-wing aircraft for a given flight condition.

Alag, G. S.↗
NASA NTRS1986

Model-following control for an oblique-wing aircraft

A variable-skew oblique wing offers a substantial aerodynamic performance advantage for aircraft missions that require both high efficiency in subsonic flight and supersonic dash or cruise. The most obvious characteristic of the oblique-wing concept is the asymmetry associated with wing-skew angle which results in significant aerodynamic and inertial cross-coupling between the aircraft longitudinal and lateral-directional axes. A technique for synthesizing a decoupling controller while providing the desired stability augmentation. The proposed synthesis procedure uses the cncept of explicit model following. Linear quadratic optimization techniques are used to design the linear feedback system. The effectiveness of the control laws developed in achieving the desired decoupling is illustrated for a given flight condition by application to linearized equations of motion, and also to the nonlinear equations of six degrees of freedom of motion with nonlinear aerodynamic data.

Alag, G. S.↗
NASA NTRS1986

NASA and general aviation

General aviation remains the single most misunderstood sector of aeronautics in the United States. A detailed look at how general aviation functions and how NASA helps keep it on the cutting edge of technology in airfoils, airframes, commuter travel, environmental concerns, engines, propellers, air traffic control, agricultural development, electronics, and safety is given.

Ethell, J. L.↗
NASA NTRS1985

A discrete control model of PLANT

A model of the PLANT system using the discrete control modeling techniques developed by Miller is described. Discrete control models attempt to represent in a mathematical form how a human operator might decompose a complex system into simpler parts and how the control actions and system configuration are coordinated so that acceptable overall system performance is achieved. Basic questions include knowledge representation, information flow, and decision making in complex systems. The structure of the model is a general hierarchical/heterarchical scheme which structurally accounts for coordination and dynamic focus of attention. Mathematically, the discrete control model is defined in terms of a network of finite state systems. Specifically, the discrete control model accounts for how specific control actions are selected from information about the controlled system, the environment, and the context of the situation. The objective is to provide a plausible and empirically testable accounting and, if possible, explanation of control behavior.

Mitchell, C. M.↗