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  • 1
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    On the disappearance of O I in some high-luminosity cool stars (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Far UV spectra and flux measurements of cool giant and supergiant stars, focusing on the O I (UV 2) and S I/Si II fluxes and their dependence on stellar parameters are presented. The de-reddened O I surface fluxes vary by factors of several hundred over the 11 stars in the sample and, at a given luminosity, decrease with decreasing effective temperature. No flux at all is detected in the three M supergiants observed to date. In contrast, the S I/Si II blend near 1810 angstrom is clearly detected in all the stars. Its strength generally increases with luminosity, but has little effective temperature dependence. Possible explanations for the behavior of O I include changes in the intensities of Lyman alpha and beta which excite the lines of S I and O I, respectively, as well as scattering and/or absorption of the O I flux in a dense, circumstellar gas shell.
    Keywords: ASTROPHYSICS
    Type: ESA, Evolution in Astrophysics: IUE Astronomy in the Era of New Space Missions; p 307-310
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  • 2
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    Performance effects of plan-based displays in commercial aviation (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The experiment reported here examines the performance consequences of alignment between display formats and the methods used during descent. Twelve commercial pilots flew one of nine Standard Terminal Arrival Routes on a stand-alone flight simulator run on a Sparc II workstation. Three different methods for descent (Manual Control, Autopilot and Spoilers) were crossed with three methods according to scope, resolution, and bandwidth properties in the display of critical information. Performance variability in speed control supports our claim that the effectiveness of a display is not an independent property of the display itself, but rather, a function of the interaction of the display and the particular methods used for achieving task goals.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: ; fe sciences and spac
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    NASA TECHNICAL REPORTS
  • 3
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    Investigation of potential anti-radiation and anti-neoplastic compounds related to plant growth regulators second quarterly progress report, 1 oct. 1964 - 1 jan. 1965 (1965)
    In:  CASI
    Details
    Publication Date: 2019-05-23
    Description: Antiradiation and antineoplastic compounds related to plant growth regulators - cytotoxic effects and radiation protection
    Keywords: BIOSCIENCES
    Type: NASA-CR-62133 , SID-65-79-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Active control of tiltrotor blade in-plane loads during maneuvers (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The origin of one/rev rotor aerodynamic loads which arise in tiltrotor aircraft during airplane-mode high speed pull-up and push-over maneuvers is examined using a coupled rotor/fuselage dynamic simulation. A modified eigenstructure assignment technique is used to design a controller which alleviates the in-plane loads during high pitch rate maneuvers. The controller utilizes rotor cyclic pitch inputs to restructure the aircraft short period and phugoid responses in order to achieve the coupling between pitch rate and rotor flapping responses which minimizes the rotor aerodynamic loading. Realistic time delays in the feedback path are considered during the controller design. Stability robustness in the presence of high frequency modeling errors is ensured through the use of singular value analysis.
    Keywords: AIRCRAFT STABILITY AND CONTROL
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  • 5
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    Helicopter individual-blade-control research at MIT 1977-1985 (1986)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: A new advanced system for active control of helicopters and its application to the solution of rotor aerodynamic and aeroelastic problems is described. Each blade is individually controlled in the rotating frame over a wide range of frequencies. Application of the system to gust alleviation, attitude stabilization, vibration alleviation, blade lag damping augmentation, stall flutter suppression, blade flapping stabilization, stall alleviation, and performance enhancement is outlined. The effectiveness of the system in achieving most of these applications is demonstrated by experimental results from wind tunnel tests of a model helicopter rotor with individual blade control. The feasibility of achieving many or all of the applications of individual blade control using the conventional helicopter swash plate is demonstrated, and the necessary control laws are presented.
    Keywords: AIRCRAFT STABILITY AND CONTROL
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  • 6
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    An Investigation of the Control Effectiveness of Tip Ailerons and Spoilers on a Low-aspect-ratio Trapezoidal-wing Airplane Model at Mach Numbers from 1.55 to 2.35 (1957)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Type: NACA-RM-A57I26a
    Format: application/pdf
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  • 7
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    Methods and principles for determining task dependent interface content (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Computer generated information displays provide a promising technology for offsetting the increasing complexity of the National Airspace System. To realize this promise, however, we must extend and adapt the domain-dependent knowledge that informally guides the design of traditional dedicated displays. In our view, the successful exploitation of computer generated displays revolves around the idea of information management, that is, the identification, organization, and presentation of relevant and timely information in a complex task environment. The program of research that is described leads to methods and principles for information management in the domain of commercial aviation. The multi-year objective of the proposed program of research is to develop methods and principles for determining task dependent interface content.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: NASA-CR-190837 , NAS 1.26:190837
    Format: application/pdf
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  • 8
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    Research on measurement and control of helicopter rotor response using blade-mounted accelerometers 1990-91 (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Wind tunnel testing of the full-size Model 412/IBC rotor performed at the NASA Ames Research Center is described. The use of blade-mounted accelerometers is found to be feasible for estimating or measuring blade flapping, lagging, and bending accelerations, rates, and displacements. Application of the imaginary swash plate concept to IBC systems leads to useful filtering of the blade accelerometer signals while permitting the control of a four-bladed rotor using measurements from any three blades. Rotor state measurements in the rotating system can be transformed to the corresponding nonrotating rotor states using the IBC algorithm with its associated filtering properties.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Format: text
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  • 9
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    The measurement and control of helicopter blade modal response using blade-mounted accelerometers (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The measurement of helicopter blade flapping, bending, and lag modal acceleration and displacement response using blade-mounted accelerometers is described. It is shown that knowledge of the blade mode shapes is sufficient to permit separation of the modal contributions to the accelerometer signals using matrix inversion. The application of the Mckillip (1985) filter to the identification of modal rate response is described. Finally, the design of flapping, bending, and lag mode controllers utilizing the conventional mesh plate is presented. The measurement technique is illustrated using flight test results obtained using a Black Hawk helicopter.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Format: text
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  • 10
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    Application of transonic slender body theory to bodies of varying complexity (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Transonic flows over several bodies of varying complexity including a simple wing-body combination and the Shuttle Orbiter have been modeled with the use of slender body theory. Flows with various angles of attack have been considered. Also some off-body flow calculations were conducted. For attached flows, the calculations predicted the pressure results with good accuracy.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0005
    Format: text
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