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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 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Analytic structure of cosmic radio jets - A preliminary investigation

The structure of the steady radio jet is discussed by analyzing the relativistic Euler equation in the case where surfaces of constant angular momentum coincide with surfaces of constant angular velocities. A closed analytic expression for the potential and other physical quantities is derived in a general stationary background geometry. The effect of the angular momentum component and the radial momentum component on the structure of the jet is studied in detail for Schwarzschild geometry. The jets are found to be pressure-confined and angular momentum-supported. The possibility of obtaining arbitrarily well-collimated jets very near to a black hole is discussed.

Chakrabarti, S. K.↗
NASA NTRS1983

Stimulated Raman up-conversion of electromagnetic waves by a gyrating electron beam

A gyrating electron beam supports negative energy modes near the harmonics of electron-cyclotron frequency. An electromagnetic wave passing through such a beam parametrically up-converts into high-frequency electromagnetic modes separated from the pump frequency by the electron-cyclotron harmonics. The growth rate for this process varies directly as the oscillatory velocity of beam electrons caused by the pump and as square root of the beam density. It has a maximum at values of scattering angle close to 180 deg and is also implicitly dependent on the beam veocity and the cyclotron frequency of electrons. The effect of a cold electron component is to reduce the growth rate.

Sharma, O. P.↗
NASA NTRS1985

New results on the generation of broadband electrostatic waves in the magnetotail

The theory of the generation of broadband electrostatic noise (BEN) in the magnetotail is extended through numerical solution of the dispersion relation under conditions that exist in the plasma sheet boundary layer. It is found that the low-frequency portion of the spectrum has a broad angular spectrum but a fairly sharp peak near 75 deg with respect to the magnetic field, while the high-frequency portion has a narrower angular spectrum that is strongly concentrated along the magnetic field line. These results are in excellent agreement with observations of the broadband wave spectrum and a recent measurement of the propagation direction. The effect of a second cold component of electrons is analyzed, and it is found that it can increase the upper cutoff frequency of BEN to the observed value at about the plasma frequency.

Grabbe, C. L.↗
NASA NTRS1987

Weibull Distribution From Interval Inspection Data

Most likely failure sequence assumed. Memorandum discusses application of Weibull distribution to statistics of failures of turbopump blades. Is generalization of well known exponential random probability distribution and useful in describing component-failure modes including aging effects. Parameters found from experimental data by method of maximum likelihood.

Rheinfurth, Mario H.↗
NASA NTRS1987

An application of artificial intelligence theory to reconfigurable flight control

Artificial intelligence techniques were used along with statistical hpyothesis testing and modern control theory, to help the pilot cope with the issues of information, knowledge, and capability in the event of a failure. An intelligent flight control system is being developed which utilizes knowledge of cause and effect relationships between all aircraft components. It will screen the information available to the pilots, supplement his knowledge, and most importantly, utilize the remaining flight capability of the aircraft following a failure. The list of failure types the control system will accommodate includes sensor failures, actuator failures, and structural failures.

Handelman, David A.↗
NASA NTRS1988

Pressure distributions from subsonic tests of an advanced laminar-flow-control wing with leading- and trailing-edge flaps

An unswept, semispan wing model equipped with full-span leading- and trailing-edge flaps was tested in the Langley 14- by 22-Foot Subsonic Tunnel to determine the effect of high-lift components on the aerodynamics of an advanced laminar-flow-control (LFC) airfoil section. Chordwise pressure distributions near the midsemispan were measured for four configurations: cruise, trailing-edge flap only, and trailing-edge flap with a leading edge Kreuger flap of either 0.10 or 0.12 chord. Part 1 of this report presents a representative sample of the plotted pressure distribution data for each configuration tested. Part 2 (under separate cover) presents the entire set of plotted and tabulated pressure distribution data. The data are presented without analysis.

Applin, Zachary T.↗
NASA NTRS1988

Pressure distributions from subsonic tests of an advanced laminar-flow-control wing with leading- and trailing-edge flaps

An unswept, semispan wing model equipped with full-span leading- and trailing-edge flaps was tested in the Langley 14- by 22-Foot Subsonic Tunnel to determine the effect of high-lift components on the aerodynamics of an advanced laminar-flow-control (LFC) airfoil section. Chordwise pressure distributions near the midsemispan were measured for four configurations: cruise, trailing-edge flap only, and trailing-edge flap with a leading-edge Krueger flap of either 0.10 or 0.12 chord. Part 1 of this report (under separate cover) presents a representative sample of the plotted pressure distribution data for each configuration tested. Part 2 presents the entire set of plotted and tabulated pressure distribution data. The data are presented without analysis.

Applin, Zachary T.↗
NASA NTRS1987

The opportunities for space biology research on the Space Station

The goals of space biology research to be conducted aboard the Space Station in 1990s include long-term studies of reproduction, development, growth, physiology, behavior, and aging in both animals and plants. They also include studies of the mechanisms by which gravitational stimuli are sensed, processed, and transmitted to a responsive site, and of the effect of microgravity on each component. The Space Station configuration will include a life sciences research facility, where experiment cyles will be on a 90-day basis (since the Space Station missions planned for the 1990s call for 90-day intervals). A modular approach is taken to accomodate animal habitats, plant growth chambers, and other specimen holding facilities; the modular habitats would be transportable between the launch systems, habitat racks, a workbench, and a variable-gravity centrifuge (included for providing artificial gravity and accurately controlled acceleration levels aboard Space Station).

Ballard, Rodney W.↗
NASA NTRS1988

Space Station - A focus for the development of structural dynamics scale model technology for large flexible space structures

The paper discusses the scale model technology being developed at the NASA Langley Research Center in support of the development of structural dynamic prediction methods for large flexible space structures. Space Station is used as a focus. The Dynamic Scale Model Technology (DSMT) Program is described; results of the effect of scaling Space Station components are presented; and supporting scale model technology development activities are described and results presented. The conceptual design of a hybrid-scale Pathfinder model for developing test techniques and suspension methods is also discussed, and a summary of the broad application of the scale model technology being developed is presented.

Letchworth, Robert↗
NASA NTRS1988

Reliability Model Generator for fault-tolerant systems

This paper discusses an analysis tool, the Reliability Model Generator, that reasons from structural and functional system design specifications to generate a reliability model for the system under investigation. The resultant model defines a system state space sufficient to characterize the effects of single and multiple component failures. This model may then be examined by the analyst or used as input to an existing reliability evaluation tool, the Semi-Markov Unreliability Range Evaluator (SURE), to compute numeric bounds for system reliability (i.e., safety, mission success, availability, etc.). In defining the input to the Reliability Model Generator, a separation of the component function from structural specification is proposed to allow easy modification for analysis of alternative architectures. A hierarchical system description paradigm promotes multiple abstractions, thereby enabling analysis at all phases of the design process. The work described in this paper has been supported under NASA contract NAS1-10899, Integrated Airframe/Propulsion Control System Architecture (IAPSA II). IAPSA II promotes a system engineering methodology and supporting analytical tools to evaluate flight control architecture configuration alternatives during early phases of the design cycle when the cost and schedule impact of design revisions is minimal. Emphasis is placed on traceability to ensure that the requirements drive the resulting design.

Catherine M McCann↗
NASA NTRS1989

NASA's program on icing research and technology

NASA's program in aircraft icing research and technology is reviewed. The program relies heavily on computer codes and modern applied physics technology in seeking icing solutions on a finer scale than those offered in earlier programs. Three major goals of this program are to offer new approaches to ice protection, to improve our ability to model the response of an aircraft to an icing encounter, and to provide improved techniques and facilities for ground and flight testing. This paper reviews the following program elements: (1) new approaches to ice protection; (2) numerical codes for deicer analysis; (3) measurement and prediction of ice accretion and its effect on aircraft and aircraft components; (4) special wind tunnel test techniques for rotorcraft icing; (5) improvements of icing wind tunnels and research aircraft; (6) ground de-icing fluids used in winter operation; (7) fundamental studies in icing; and (8) droplet sizing instruments for icing clouds.

Reinmann, John J.↗
NASA NTRS1989

NASA's program on icing research and technology

NASA's program in aircraft icing research and technology is reviewed. The program relies heavily on computer codes and modern applied physics technology in seeking icing solutions on a finer scale than those offered in earlier programs. Three major goals of this program are to offer new approaches to ice protection, to improve the ability to model the response of an aircraft to an icing encounter, and to provide improved techniques and facilities for ground and flight testing. The following program elements are reviewed: (1) new approaches to ice protection; (2) numerical codes for deicer analysis; (3) measurement and prediction of ice accretion and its effect on aircraft and aircraft components; (4) special wind tunnel test techniques for rotorcraft icing; (5) improvements of icing wind tunnels and research aircraft; (6) ground de-icing fluids used in winter operation; (7) fundamental studies in icing; and (8) droplet sizing instruments for icing clouds.

Reinmann, John J.↗
NASA NTRS1990

Two-dimensional Euler and Navier-Stokes Time accurate simulations of fan rotor flows

Two numerical methods are presented which describe the unsteady flow field in the blade-to-blade plane of an axial fan rotor. These methods solve the compressible, time-dependent, Euler and the compressible, turbulent, time-dependent, Navier-Stokes conservation equations for mass, momentum, and energy. The Navier-Stokes equations are written in Favre-averaged form and are closed with an approximate two-equation turbulence model with low Reynolds number and compressibility effects included. The unsteady aerodynamic component is obtained by superposing inflow or outflow unsteadiness to the steady conditions through time-dependent boundary conditions. The integration in space is performed by using a finite volume scheme, and the integration in time is performed by using k-stage Runge-Kutta schemes, k = 2,5. The numerical integration algorithm allows the reduction of the computational cost of an unsteady simulation involving high frequency disturbances in both CPU time and memory requirements. Less than 200 sec of CPU time are required to advance the Euler equations in a computational grid made up of about 2000 grid during 10,000 time steps on a CRAY Y-MP computer, with a required memory of less than 0.3 megawords.

Boretti, A. A.↗
NASA NTRS1991

Reliability and risk assessment of structures

Development of reliability and risk assessment of structural components and 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) the evaluation of the various uncertainties in terms of cumulative distribution functions for various structural response variables based on known or assumed uncertainties in primitive structural variables; (2) evaluation of the failure probability; (3) reliability and risk-cost assessment; and (4) an outline of an emerging approach for eventual certification of man-rated structures by computational methods. Collectively, the results demonstrate that the structural durability/reliability of man-rated structural components and structures can be effectively evaluated by using formal probabilistic methods.

Chamis, C. C.↗
NASA NTRS1991

An overview of the first results on the solar array passive LDEF experiment (sample), AO171

Space environmental effects were visibly obvious on components of experiment AO171 which contained solar cells, composites, polymeric thin films, solar reflectors, protective coatings, metals, paints , and elastomers. Micrometeoroid/space debris impacts were observed on all experiment elements. Luminescence of polyimide, silicone, and polyurethane materials occurred under black light examination. Outgassing of RTV511 occurred mainly as a result of insufficient thermal vacuum bakeout. Solar cell degradation was predominantly below 10 percent. Elastomers lost mass and discolored; composites showed evidence of atomic oxygen attack, and unprotected thin polymer films eroded away.

Whitaker, Ann F.↗
NASA NTRS1987

Rapidly solidified nickel aluminide of improved stoichiometry and ductilization

It has been found that tri-nickel aluminide compositions are quite sensitive to the ratio of nickel to aluminum in their ability to receive boron as a dopant and that compositions which are relatively poor in the aluminum component can be doped more effectively with boron. Further, it has been found for the nickel aluminides which have lower concentrations of aluminum that the percentage of boron which can be added to the composition to effectively increase the strength of the alloys is . favored by the lower aluminum ratio so that higher concentrations of boron are addable. The compositions which result have significant strength properties based on tensile tests of the compositions.

Alan I Taub↗
NASA NTRS1990

Novel approaches for fabrication of thin film layers for solid oxide electrolyte fuel cells

The main objectives of the SOFC (solid oxide fuel cell) project are to (1) identify viable and cost-effective techniques to prepare cell components for stable MSOFCs (monolithic SOFCs); (2) fabricate half and single cells; and (3) evaluate their performances. The approach used to fabricate stable MSOFCs is as follows: (1) the electrolyte layer is prepared in the form of a honeycomb structure by alloy oxidation and other cell components are deposited on it; (2) the electrolyte and anode layers are deposited on the cathode layer, which has a porous, honeycomb structure; and (3) the electrolyte and cathode layers are deposited on the anode layer. The current status of the project is reported.

Murugesamoorthi, K. A.↗
NASA NTRS1992

Rotary Apparatus Concentrates And Separates Micro-Organisms

Apparatus concentrates and separates swimming micro-organisms of different species into concentric rings in fluid. Fluid containing high concentration of desired species removed by use of small scoop placed into fluid at radius of one of rings formed by that species. Micro-organisms concentrated into concentric rings by combined dynamic effects of upward and horizontal components of swimming, rotation of dish, gravitation, and viscosity.

Noever, David A.↗