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  • 1
    Publication Date: 2011-10-14
    Description: The test capabilities of the Stability Wind Tunnel of the Virginia Polytechnic Institute and State University are described, and calibrations for curved and rolling flow techniques are given. Oscillatory snaking tests to determine pure yawing derivatives are considered. Representative aerodynamic data obtained for a current fighter configuration using the curved and rolling flow techniques are presented. The application of dynamic derivatives obtained in such tests to the analysis of airplane motions in general, and to high angle of attack flight conditions in particular, is discussed.
    Keywords: AERODYNAMICS
    Type: AGARD Dyn. Stability Parameters; 13 p
    Format: text
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  • 2
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    In:  Other Sources
    Publication Date: 2011-08-18
    Description: Maneuvers available to a spacecraft having sufficient propellant to escape an antisatellite satellite (ASAT) attack are examined. The ASAT and the evading spacecraft are regarded as being in circular orbits, and equations of motion are developed for the ASAT to commence a two-impulse maneuver sequence. The ASAT employs thrust impulses which yield a minimum-time-to-rendezvous, considering available fuel. Optimal evasion is shown to involve only in-plane maneuvers, and begins as soon as the ASAT launch information is gathered and thrust activation can be initiated. A closest approach, along with a maximum evasion by the target spacecraft, is calculated to be 14,400 ft. Further research to account for ASATs in parking orbit and for generalization of a continuous control-modeled differential game is indicated.
    Keywords: ASTRODYNAMICS
    Type: Journal of the Astronautical Sciences; 29; July-Sep
    Format: text
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  • 3
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    In:  CASI
    Publication Date: 2016-06-07
    Description: Methods are reported for reducing the aircraft drag coefficient for a given aircraft lift coefficient, or speed. The emphasis is placed in determining the load distribution between the wing-body combination and the tail which reduces overall drag coefficient. Furthermore, a technique is presented which allows the determination of various aerodynamic and geometric parameters to permit the best location to satisfy inherent stability requirements. Included in the method is the calculation of sensitivity coefficients which indicate the importance of various parameters in achieving specified goals. Preliminary results indicate that such an approach is feasible.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Kansas Univ. Proc. of the NASA, Ind., Univ., Gen. Aviation Drag Reduction Workshop; p 307-318
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: Current departure prediction indicators for both open and closed loop flight are developed using the same rigorous analytical approach applied to a linear version of the aircraft model. Emphasis on the assumptions made and terms omitted indicate why the results are somewhat limited. A second approach is presented which is shown to lead to the same results as the first, but is more applicable to the nonlinear problem. Some ideas concerning the application of the linear methods to the nonlinear problem are presented.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 93-3650 , In: AIAA Atmospheric Flight Mechanics Conference, Monterey, CA, Aug. 9-11, 1993, Technical Papers (A93-48301 20-08); p. 324-331.
    Format: text
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  • 5
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: The poststall gyrations of a high-performance aircraft are investigated by approximating the equations of motion with a linear mathematical model. Equilibrium poststall spin conditions are determined, which are not limited to small angles or spin rates and are used as reference conditions about which the linear model is developed. As a result, complete coupling between lateral and longitudinal motions is retained. Three aerodynamic models are evaluated using this linear analysis. These models include pure rotary derivatives obtained from VPI&SU stability tunnel, forced-oscillation data obtained from NASA tests, and a combination of the two which separates the unsteady and pure rotary derivatives. Results indicate that this last model gives better predictions of aircraft motion during poststall gyrations at high angles of attack and large sideslip angles. Comparisons are made with full-scale flight test results.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: Journal of Aircraft; 17; Oct. 198
    Format: text
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  • 6
    Publication Date: 2019-07-13
    Description: The technique of using a curved and rolling flow wind tunnel to extract pure rotary stability derivatives is presented. Descriptions of the curved flow and the rolling flow test sections of the Virginia Tech Stability Wind Tunnel are given including methods for obtaining the proper velocity profiles and correcting the data acquired. Results of testing current fighter configurations in this facility are presented with particular attention given to comparing pure rotary derivatives with combined rotary and unsteady derivatives obtained by standard oscillation tests. Also the effect of curved and rolling flow on lateral static stability derivatives is examined.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 80-0309 , Aerospace Sciences Meeting; Jan 14, 1980 - Jan 16, 1980; Pasadena, CA
    Format: text
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  • 7
    Publication Date: 2019-06-28
    Description: (Previously cited in issue 21, p. 3636, Accession no. A81-44084)
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Format: text
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  • 8
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    In:  CASI
    Publication Date: 2019-06-28
    Description: The curved flow capability of a stability wind tunnel was used to investigate the lateral directional characteristics of an F-18 aircraft. The model is described and the procedures used to obtain and correct the data and a graphical presentation of the results are presented. The results include graphs of lateral directional derivatives versus sideslip or static plots, the lateral directional static stability derivatives versus angle of attack, and finally the lateral directional derivatives versus nondimensional yaw rate for different angles of attack and sideslip. Results are presented for several configurations including complete, complete without vertical tails, complete without horizontal tails, fuselage wing and fuselage alone. Each of these were tested with and without wing leading edge extensions.
    Keywords: AERODYNAMICS
    Type: NASA-CR-169345 , NAS 1.26:169345 , VPI-AERO-108
    Format: application/pdf
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  • 9
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    In:  CASI
    Publication Date: 2019-06-28
    Description: The lateral directional characteristics of an F-18 aircraft was investigated. Aerodynamic derivatives associated with pure roll rate, or the 'p' derivatives were obtained. The model is described and the procedures used to obtain and correct the data, and a graphical presentation of the results are presented. These results include graphs of the lateral directional static stability derivatives versus angle of attack, and the lateral directional force and moment coefficients versus nondimensional roll rate. Results are presented for several configurations including complete, complete without vertical tails, complete without horizontal tails, fuselage wing and fuselage alone. Each of these configuations was tested with and without wing leading edge extensions. The basic control surfaces were deflected and the results were investigated.
    Keywords: AERODYNAMICS
    Type: NASA-CR-169344 , NAS 1.26:169344
    Format: application/pdf
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  • 10
    Publication Date: 2019-07-13
    Description: The terminal guidance problem for a fixed-trim re-entry body is formulated with the objective of synthesizing a closed-loop steering law. A transformation of variables and subsequent linearization of the motion, with the sight-line to the target as a reference, reduces the order of the state system for the guidance problem. The reduced order system, although nonlinear and time-varying, is simple enough to lend itself to synthesis of a class of guidance laws. A generalization of the feedforward device of classical control theory is successfully employed for compensation of roll autopilot lags. The proposed steering law exhibits superior miss-distance performance in a computational comparison with existing fixed-trim guidance laws.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AIAA PAPER 81-1754 , Guidance and Control Conference; Aug 19, 1981 - Aug 21, 1981; Albuquerque, NM
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