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  • AERODYNAMICS  (4)
  • GEOPHYSICS  (2)
  • 2000-2004
  • 1975-1979  (6)
  • 1979  (2)
  • 1978  (4)
  • 1
    Publication Date: 2019-06-27
    Description: A new device was proposed for alleviating high angle-of-attack side force on slender, pointed forebodies. A symmetrical pair of separation strips in the form of helical ridges are applied to the forebody to disrupt the primary lee-side vortices and thereby avoid the instability that produces vortex asymmetry. Preliminary wind tunnel tests at Mach 0.3 and Reynolds no. 5,250,000 on a variety of forebody configurations and on a wing-body combination at angles of attack up to 56 degrees, demonstrated the effectiveness of the device.
    Keywords: AERODYNAMICS
    Type: NASA-CR-145361
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: The paper deals with equatorial ATS-6 measurements of the shape factor, F, interpreted in terms of the shape of the electron density profile along the ray path. The observed rapid increase in F at sunrise is attributed to EUV production of ionization in the E and F regions. The evening decrease is seen to result from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak, or plateau, is caused by gradual decrease of the electron density profile.
    Keywords: GEOPHYSICS
    Type: Symposium on Beacon Satellite Measurements of Plasmaspheric and Ionospheric Properties; May 22, 1978 - May 25, 1978; Florence; Italy
    Format: text
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  • 3
    Publication Date: 2019-07-13
    Description: In August 1975 the ATS6 was repositioned at 35 deg E. Radio beacon measurements of time delay, Faraday rotation and signal amplitude, made at Ootacamund, India in October 1975, are discussed with emphasis on the problem of determining the Faraday content under essentially transverse propagation conditions. It is shown that at the low geomagnetic latitude of Ootacamund the use of a fixed conversion coefficient gives an unreliable Faraday content. It is shown also that corrections to the measured Faraday rotation are important because of pitch and yaw of the satellite, particularly at night when the rotation on 140 MHz can be of the order of 10 to 20 deg. The shape factor shows a low predawn minimum indicating the nearly complete erosion of the F2 layer peak. Amplitude scintillation usually decreases with increase of radio frequency but exceptions are discussed.
    Keywords: GEOPHYSICS
    Type: Symposium on Beacon Satellite Measurements of Plasmaspheric and Ionospheric Properties; May 22, 1978 - May 25, 1978; Florence; Italy
    Format: text
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  • 4
    Publication Date: 2019-06-27
    Description: The configuration consisted of a 30 deg -swept, untapered, untwisted wing utilizing a low-moment cambered airfoil of 20 percent streamwise thickness designed for low wave drag at M = 0.6, C sub L = 0.4. The tests covered a range of Mach numbers 0.3 to 0.725 and chord Reynolds number 1,100,000 to 2,040,000, angles of attack up to model buffet and sideslip angles + or - 4 deg. Configuration build up, wing pod filleting, airfoil modification and trailing edge control deflection effects were briefly investigated. Three wing tip vertical tail designs were also tested. Wing body filleting and a simple airfoil modification both produced increments to maximum lift/drag ratio. Addition of pods eliminated pitch instability of the basic wing. While the magnitude of these benefits probably was Reynolds number sensitive, they underline the potential for improving the aerodynamics of the present configuration. The cruise parameter (product of Mach number and lift/drag ratio) attained a maximum close to the airfoil design point. The configuration was found to be positively stable with normal control effectiveness about all three axes in the Mach number and C sub L range of interest.
    Keywords: AERODYNAMICS
    Type: NASA-TM-78767
    Format: application/pdf
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  • 5
    Publication Date: 2019-06-27
    Description: Exploratory wind tunnel tests are reported on a 74 deg. delta wing model. The potential of a vortex flap concept in reducing the subsonic lift dependent drag of highly swept, slender wings is examined. The suction effect of coiled vortices generated through controlled separation over leading edge flap surfaces to produce a thrust component is discussed. A series of vortex-flap configurations were investigated to explore the effect of some primary geometric variables.
    Keywords: AERODYNAMICS
    Type: NASA-CR-159161
    Format: application/pdf
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  • 6
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    In:  CASI
    Publication Date: 2019-06-27
    Description: An analysis and a numerical lifting surface method are developed for predicting the unsteady airloads on two-dimensional circulation control airfoils in incompressible flow. The analysis and the computer program are validated by correlating the computed unsteady airloads with test data and also with other theoretical solutions. Additionally, a mathematical model for predicting the bending-torsion flutter of a two-dimensional airfoil (a reference section of a wing or rotor blade) and a computer program using an iterative scheme are developed. The flutter program has a provision for using the CC airfoil airloads program or the Theodorsen hard flap solution to compute the unsteady lift and moment used in the flutter equations. The adopted mathematical model and the iterative scheme are used to perform a flutter analysis of a typical CC rotor blade reference section. The program seems to work well within the basic assumption of the incompressible flow.
    Keywords: AERODYNAMICS
    Type: NASA-CR-152301
    Format: application/pdf
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