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  • 1
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    Optimum horizontal guidance techniques for aircraft (1978)
    In:  CASI
    Details
    Publication Date: 2006-03-02
    Description: Some problems of automatic guidance of an aircraft in the horizontal plane are described. The horizontal guidance tasks, which such a flight control system should be capable of performing, were identified as being of three types: guiding the aircraft from any initial location and initial heading to (1) any final location and heading; (2) intercept and fly along a line of specified direction; and (3) a final location with arbitrary final heading. Guidance problems such as capturing an ILS beam at a specified point on the beam, intercepting a VOR radial, and point-to-point navigation can be formulated in terms of these problems. The guidance laws minimize the arc distance to fly between initial and final conditions subject to constraints on the minimum turning radius.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: NASA, Washington Fourth Inter-Center Control Systems Conf.; p 175-184
    Format: text
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  • 2
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    An assessment of thermal design procedures for Shuttle payloads (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: A review of the thermal design options for unmanned Shuttle payloads is presented. Because many future Shuttle payloads will have budgets and less time available for the definition of their thermal subsystems, simplified design procedures will be the most cost-effective. The thermal interface between an individual payload and the Orbiter is discussed. A simplified, modular thermal control system that will reduce the cost of providing thermal protection by minimizing both the initial procurement cost of any specialized hardware and the need for a detailed thermal interface analysis is described.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: ESA Spacecraft Thermal and Environ. Control Systems; p 481-486
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  • 3
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    Discontinuous transitions in a current-carrying plasma (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The properties of 'discontinuous' transitions in a current-carrying plasma are investigated by adopting an approach based on the two-fluid equations for a plasma. Braginskii's (1965) transport equations for a two-fluid plasma carrying a current are presented, and allowance is made for collisions with a background neutral gas as well as for effects of reflected particles. The speed of sound in a current-carrying plasma is derived so that the Mach number can be defined correctly as the ratio of the flow speed to the wave phase velocity in such a plasma. The various types of discontinuities permitted by the relevant jump relations in the absence of reflected particles are classified, the effect of reflected particles on such discontinuities is examined, and it is shown that the degree of indeterminacy of a discontinuity can be changed by the presence of reflected particles. Consideration of shocks containing a population of reflected particles and adiabatic transitions indicates that the pressure of reflected particles alone can give rise to both weak and strong transitions. The construction of discontinuous periodic flow solutions is also discussed.
    Keywords: PLASMA PHYSICS
    Type: Astrophysics and Space Science; 51; 1, Se; Sept
    Format: text
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  • 4
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    NASTRAN thermal analyzer status, experience, and new developments (1975)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The unique finite element based NASTRAN Thermal Analyzer originally developed as a general purpose heat transfer analysis incorporated into the NASTRAN system is described. The current status, experiences from field applications, and new developments are included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: User's Experiences; p 523-528
    Format: application/pdf
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  • 5
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    The GSFC NASTRAN thermal analyzer new capabilities (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An overview of four analysis capabilities, which developed and integrated into the NASTRAN Thermal Analyzer, is given. To broaden the scope of applications, these additions provide the NTA users with the following capabilities: (1) simulating a thermal louver as a means of the passive thermal control, (2) simulating a fluid loop for transporting energy as a means of the active thermal control, (3) condensing a large sized finite element model for an efficient transient thermal analysis, and (4) entering multiple boundary condition sets in a single submission for execution in steady state thermal analyses.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: User's Experiences; p 119-126
    Format: application/pdf
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  • 6
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    On modeling and the use of the NASTRAN thermal analyzer (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Eight alternative modeling techniques to specify prescribed temperature at grid or scalar points for transient thermal analyses are presented. Four cases are for constant temperatures, and the others are time varying temperature functions. Theoretical explications and detailed listing of input data cards used for illustrating different modelings are given. It is shown that the NTA is exploited to extend beyond its normal capabilities through innovative modeling techniques. In addition, the effect of node valency on the energy distribution grid points is illustrated and discussed. Guidelines to delineate this effect are given.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: User's Experiences; p 3-20
    Format: application/pdf
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  • 7
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    Theory of molecular rate processes in the presence of intense laser radiation (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The present paper deals with the influence of intense laser radiation on gas-phase molecular rate processes. Representations of the radiation field, the particle system, and the interaction involving these two entities are discussed from a general rather than abstract point of view. The theoretical methods applied are outlined, and the formalism employed is illustrated by application to a variety of specific processes. Quantum mechanical and semiclassical treatments of representative atom-atom and atom-diatom collision processes in the presence of a field are examined, and examples of bound-continuum processes and heterogeneous catalysis are discussed within the framework of both quantum-mechanical and semiclassical theories.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Format: text
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  • 8
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    Characteristics of constrained optimum trajectories with specified range (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Necessary conditions of optimality are derived for trajectories whose structure is limited to climb, steady cruise, and descent segments. The performance function consists of the sum of fuel and time costs, referred to as direct operating cost (DOC). The state variable is range to go and the independent variable is energy. In this formulation a cruise segment always occurs at the optimum cruise energy for sufficiently large range. At short ranges (500 n. mi. and less) a cruise segment may also occur below the optimum cruise energy. The existence of such a cruise segment depends primarily on the fuel flow vs thrust characteristics and on thrust constraints. If thrust is a free control variable along with airspeed, it is shown that such cruise segments will not generally occur. If thrust is constrained to some maximum value in climb and to some minimum in descent, such cruise segments generally will occur. Computer calculations of typical short-range trajectories obtained about a 1% cost penalty for constraining the thrust.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: NASA-TM-78519 , A-7592
    Format: application/pdf
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  • 9
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    Finite-element numerical modeling of atmospheric turbulent boundary layer (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A dynamic turbulent boundary-layer model in the neutral atmosphere is constructed, using a dynamic turbulent equation of the eddy viscosity coefficient for momentum derived from the relationship among the turbulent dissipation rate, the turbulent kinetic energy and the eddy viscosity coefficient, with aid of the turbulent second-order closure scheme. A finite-element technique was used for the numerical integration. In preliminary results, the behavior of the neutral planetary boundary layer agrees well with the available data and with the existing elaborate turbulent models, using a finite-difference scheme. The proposed dynamic formulation of the eddy viscosity coefficient for momentum is particularly attractive and can provide a viable alternative approach to study atmospheric turbulence, diffusion and air pollution.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology; 18; Oct. 197
    Format: text
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  • 10
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    Molecular collisions in a laser field - Effect of the laser linewidth (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The effect of the laser linewidth on molecular collision processes taking place in a laser field is studied, using an approximation scheme that replaces the actual frequency distribution of the field by a finite number of frequencies and weights. The choice of the frequencies and weights is conveniently accomplished by the method of Gaussian quadrature. Close-coupling calculations are performed on model systems, and the results indicate that the neglect of the laser linewidth may be justified in most collision processes in a laser field.
    Keywords: LASERS AND MASERS
    Type: Journal of Chemical Physics; 69; Sept. 15
    Format: text
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