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  • AERODYNAMICS  (843)
  • COMMUNICATIONS AND RADAR
  • 2000-2004
  • 1995-1999
  • 1980-1984
  • 1975-1979  (1,246)
  • 1970-1974
  • 1977  (620)
  • 1976  (626)
Collection
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  • 2000-2004
  • 1995-1999
  • 1980-1984
  • 1975-1979  (1,246)
  • 1970-1974
Year
  • 1
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    Economy of flight at supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: Prandtl's theory is used to determine the airflow over bodies and wings adapted to supersonic flight. By making use of these results, and by incorporating in them an allowance for the probable skin friction, some estimates of expected lift-drag ratios are made for various flight speeds with the best configuration. At each speed a slender body and wings having the best angle of sweepback are considered. For the range of supersonic speeds shown an airplane of normal density and loading would be required to operate at an altitude of the order of 60,000 feet. The limiting value of 1-1/2 times the speed of sound corresponds to a flight speed of 1000 miles per hour. At this speed about 1.5 miles per gallon of fuel are expected. It is interesting to note that this value corresponds to a value of more than 15 miles per gallon when the weight is reduced to correspond to that of an ordinary automobile.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 499-514
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  • 2
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    Aeroelastic characteristics of an oblique wing (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: In theory, the most efficient wing shape for transonic and low supersonic speeds is simply a long narrow straight subsonic wing turned at an oblique angle to the flight direction. This theory has been verified by tests at Mach numbers from .6 to 1.4 in supersonic wind tunnel and by comparative studies of transonic transport designs.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 867-883
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  • 3
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    Aerodynamic design for supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: Recent theoretical and experimental work in supersonic aerodynamics is reviewed with its practical application in mind. Several arrangements of supporting surfaces and bodies are discussed and in some cases comparisons of theory and experiment are made. Finally, certain phenomena connected with lift and drag in a rarefied medium are considered briefly.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 625-644
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  • 4
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    Theoretical determination of the minimum drag of airfoils at supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: A method is reported for determining mathematically the combined disturbance field, and in certain cases the minimum drag, of wings at supersonic speeds. The simplest analytic example is provided by the wing of elliptic planform, which achieves its minimum drag when the lift is distributed uniformly over the surface. With a symmetrical distribution of thickness, the requirement of minimum drag for a given total volume is found to lead to profiles of constant curvature.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 567-578
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  • 5
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    The minimum drag of thin wings in frictionless flow (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: The assumptions of the thin airfoil theory are found to provide certain necessary conditions for the minimum drag of airfoils having a given total lift, a given maximum thickness, or a given volume. The conditions are applicable to steady or unsteady motions and to subsonic or supersonic speeds without restriction on the planform. The computation of drag and the statement of the conditions for minimum drag depend on the consideration of a combined flow field, which is obtained by superimposing the disturbance velocities in forward and reversed motions. If the planform of the airfoil and its total lift are given, it is found that, for minimum drag, the lift must be distributed in such a way that the downwash in the combined field is constant over the entire planform. If the planform is given and the thickness of the airfoil is required to contain a specified volume, then the thickness must be distributed over the planform in such a way that the pressure gradient of the combined field in the direction of flight is constant at all points of the wing.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 557-565
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  • 6
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    Calculation of the motion of an airplane under the influence of irregular disturbances (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: The application of mathematical advances made in electricity and other branches to problems of airplane dynamics is demonstrated. The Heaviside-Bromwich methods of solution of linear differential equations are described and it is shown how these methods avoid the consideration of boundary conditions and of particular or complementary integrals. It is pointed out that if the solution of the differential equation is obtained for the case of a unit disturbance, the effect of varying disturbances may be found therefrom by Carson's theorem. A graphical solution of Carson's integral for irregular disturbances is given. The procedure of obtaining unit solutions of the equations is then taken up and the analogy between Heaviside's symbolic series solution and a physical procedure of approximation is shown. It is suggested that a fictitious impulsive disturbance be used in the treatment of initial motions.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 21-29
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  • 7
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    Three-dimensional wings of minimum pressure drag (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: In linearized flow theory, certain very interesting extremal properties of wings can be derived under rather broad conditions without the use of a complicated mathematical apparatus. The present chapter reviews certain results of this theory and indicates some rather obvious extensions to incorporate various auxiliary conditions. Several examples illustrating the relation between the geometrical features of the wing and the lift distribution for minimum drag are given.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Collected Works of Robert T. Jones; p 645-656
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  • 8
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    Some recent developments in the aerodynamics of wings for high speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: The items discussed are: (1) a recently proposed correction formula for the effect of compressibility in two dimensional subsonic flow; (2) the equivalence rule and the area rule for transonic speeds; (3) reciprocal relations in linearized wing theory; and (4) some general results connected with the problem of minimum wave resistance. The paper concludes with an example showing indentation of the fuselage to obtain favorable interference with the wing at supersonic speeds.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 601-608
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  • 9
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    Theoretical correction for the lift of elliptic wings (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: In the wing section theory the magnitude of the circulation, and hence of the lift, is determined by the velocity that would be induced near the trailing edge of the section in a non-lifting potential flow. In three dimensional flow the problem is complicated by the presence of the wake and no simple basic solution has been found. Treatment of the problem of a wing of finite span is reported on the basis of the two dimensional theory, corrected for the effect of the wake.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 245-249
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  • 10
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    Reduction of wave drag by antisymmetric arrangement of wings and bodies (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: In theory, antisymmetric arrangements of wings and bodies can have smaller wave drag than corresponding mirror-symmetric arrangements. Thus, a long narrow oblique wing which presents the same aspect for two opposite directions of flight is potentially more efficient than corresponding (i.e., structurally equivalent) swept wing. The single continuous wing panel also adapts itself more readily to varying angles of obliquity, and hence, to varying flight speeds. Previous work on the aerodynamics and flight stability of oblique wing combinations is reviewed and a possible mode of application to transport aircraft operating at moderate supersonic speeds is suggested.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 657-664
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  • 11
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    The compressibility rule for drag of airfoil noses (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: It is shown that the drag of any semi-infinite airfoil section in purely subsonic inviscid flow follows precisely the Prandtl-Glauert compressibility rule. The result for the parabola has application to leading edge corrections in thin airfoil theory.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 619-623
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  • 12
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    Possibilities of efficient high-speed transport airplanes (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: Comparisons of wing-body combinations may not disclose the full effect of a loss in aerodynamic efficiency. If the thrust needs to be increased at a given altitude then more or larger engines will have to be used and the possibility of concealing them becomes less. In this process the lift drag ratio of the complete airplane may become still more unfavorable than indicated by the comparison. Primarily aerodynamic and structural considerations point toward the development of turbojet engines specifically adapted to operation in an atmosphere of one tenth normal density. In addition to the numerous other technological problems associated with operation at these high altitudes, the problems of safe descent and effective limitation to low speeds at low altitudes seem important.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 579-592
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  • 13
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    Leading-edge singularities in thin-airfoil theory (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: If the thin airfoil theory is applied to an airfoil having a rounded leading edge, a certain error will arise in the determination of the pressure distribution around the nose. It is shown that the evaluation of the drag of such a blunt nosed airfoil by the thin airfoil theory requires the addition of a leading edge force, analogous to the leading edge thrust of the lifting airfoil. The method of calculation is illustrated by application to: (1) The Joukowski airfoil in subsonic flow; and (2) the thin elliptic cone in supersonic flow. A general formula for the edge force is provided which is applicable to a variety of wing forms.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 533-538
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  • 14
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    The use of conical and cylindrical fields in supersonic wing theory (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: Some of the recent advances in the theory of thin airfoils are presented with particular reference to extensions of the theory to three dimensional flows and to supersonic speeds. The problem discussed herein is the calculation of the small disturbance velocities u, v, and w in the external field produced by the flight velocity V of the airfoil.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 483-497
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  • 15
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    Transonic/supersonic inlet R and D past, present, and future (1977)
    In:  CASI
    Details
    Publication Date: 2004-10-07
    Keywords: AERODYNAMICS
    Type: NASA Lewis Research Center Inlet Workshop; p 427-480
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  • 16
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    Comments on wind-tunnel-flight correlations for the F-8 supercritical wing configurations (1977)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Keywords: AERODYNAMICS
    Type: Supercritical Wing Technol.: A Report on Flight Evaluation; p 111-120
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  • 17
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    Aircraft (1977)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The physical principles of flight, and the consideration of atmospheric composition and aerodynamic forces in the design and construction of various types of aircraft are discussed. Flight characteristics are described for helicopters, rotary-wing aircraft, short and vertical takeoff aircraft, and tailess or variable geometry wing aircraft. Flow characteristics at various speeds are also discussed.
    Keywords: AERODYNAMICS
    Type: Soviet Aircraft and Rockets (NASA-TT-F-770); p 24-80
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  • 18
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    The lateral flying qualities of the Bell XP-77 airplane as estimated from full-scale tunnel tests, 16 June 1944 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Results are presented for tests made of the full scale model of the airplane in the NACA full scale tunnel. These tests were planned so as to cover as completely as possible the lateral flying quality requirements for pursuit-type airplanes contracted for by the United States Army Air Forces.
    Keywords: AERODYNAMICS
    Type: Collected Works of Charles J. Donlan; 23 p
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  • 19
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    Three dimensional boundary layer separation in supersonic flow (1976)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: An account is given of a detailed experimental investigation of three dimensional boundary layer separation in supersonic flow. In investigating three dimensional effects on supersonic separation, models were chosen which exhibited departures from two dimensional flow in the simplest way. The plane compression corner was replaced by a plate attached to a swept back wedge formed by two obliquely intersecting planes. Maintaining a constant tunnel Mach number of 2.5, surface pressure measurements were made on these models at static orifices spaced along the centerline and along three parallel lines. The flow parameters in the boundary layer and separated regions adjacent to the model surface were measured by traversing hot wire and pitot probes. The traverses were taken across the boundary layer and reversed flow regions in a direction normal to the body surface; they were made in several vertical planes, including the plane of symmetry.
    Keywords: AERODYNAMICS
    Type: AGARD Flow Separation; 13 p
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  • 20
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    Numerical solution of the steady-state Navier-Stokes equations for hypersonic flow about blunt axisymmetric bodies (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The steady-state Navier-Stokes equations are solved for hypersonic flow about blunt axisymmetric bodies. The equations of motion are solved by successive approximations using an implicit finite-difference scheme. The results are compared with viscous shock-layer theory, experimental data, and time-dependent solutions of the Navier-Stokes equations. It is demonstrated that viscous shock-layer theory is sufficiently accurate for the range of flight conditions normally encountered by entry vehicles.
    Keywords: AERODYNAMICS
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  • 21
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    A radio lens in the ionosphere (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Using a modified version of the classical Cornu spiral, fading patterns in agreement with observations of radio signals on 140 and 360 MHz from the geostationary satellite ATS6, have been obtained. The particular fading patterns chosen show modulated quasi-periodic fading before and after a deep central minimum. It is shown that a cylindrical lens in the ionosphere required to produce this is only about 100 m across (an order of magnitude smaller than the size of the pattern on the ground) and if it were circular in cross-section would have a maximum plasma frequency of over 40 MHz. This suggests the reason why calculations based on a transparent phase screen did not give the observed fading pattern for 40 MHz signals. It was not possible to deduce the height of the lens above the ground, though we would incline to an E-region origin.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Journal of Atmospheric and Terrestrial Physics; 39; Mar. 197
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  • 22
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    Limitations on oceanographic use of beam-limited target-referenced radars (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A general development is undertaken to determine the limitations on the use of beam-limited target-referenced radars in the measurement of ocean wave height. This class of radars is concerned only with the range extent of the target, not the range to the target. The nonzero range extent of a flat waveless sea and the compounding effect of pointing errors due to radar platform instability cause difficulty in measuring low wave heights and impose a maximum operating altitude on such systems. It is seen that it is impractical to obtain accurate measurements for wave heights of interest at altitudes above those used by commercial aircraft (10,000 m). Additionally, the typical ratio of dominant wavelength to significant wave height (SWH) of 30 for wind-driven gravity waves imposes an upper limit on the SWH measurable for a given altitude and beamwidth.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; May 1977
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  • 23
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    Tracking performance of symbol synchronizers for Manchester coded data (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The implementation and tracking performance of symbol synchronizers for Manchester coded data is presented with motivation provided by maximum a posteriori (MAP) estimation theory. Certain physically relizable closed-loop structures, readily implemented in practice, are suggested by the theory for uncoded data symbols with arbitrary data transition probabilities. The tracking performance of these loops is optimized and comparisons are made among the various configurations over a wide range of system parameters. Although not the major intent of the paper, the acquisition problem is briefly addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Apr. 197
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  • 24
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    Numerical solution for subcritical flows by a transonic integral equation method (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The method presented makes use of a division of the region of integration into closed rectangular elements. The velocity is taken to be constant in each element. The integral equation is reduced to a matrix equation which can be solved by an appropriate iteration approach. The derivation and solution of the matrix equation are discussed and the matrix elements are considered. The described concepts were implemented for a nonlifting parabolic-arc airfoil.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; Mar. 197
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  • 25
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    An antenna for limited scan in one plane - Design criteria and numerical simulation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Aperture illumination is synthesized through the use of overlapping subarrays with independently controlled excitations. Detailed analysis and design criteria are provided for a specific limited-scan antenna configuration scanning in one plane. The number of phase shifts is the theoretical minimum corresponding to specified aperture size and field of view. Beam pointing and width are approximately constant for moderate frequency variation, and ultralow sidelobes outside the field of view can be produced at the cost of a slight loss of illumination efficiency. Accurate aperture illumination control makes for excellent independently specified sum and difference patterns in beamforming.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; Mar. 197
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  • 26
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    Optimum performance of suppressed carrier receivers with Costas loop tracking (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The performance of suppressed carrier receivers with Costas loop tracking is optimized by proper choice of loop arm filter bandwidth. In particular, it is shown that for a variety of passive arm filter types, there exists, for a given data rate and data signal-to-noise ratio, an optimum filter bandwidth in the sense of minimizing the loop's squaring loss. For the linear theory case, this is equivalent to minimizing the loop's tracking jitter. When symbol synchronization is known, it is shown that by replacing the passive arm filters with active filters, i.e., integrate-and-dump circuits, one can achieve an improvement in carrier-to-noise ratio of as much as 4 to 6 dB depending on the passive arm filter type used for comparison and the value of data signal-to-noise ratio.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Feb. 197
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  • 27
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    Derivation of an integral equation for transonic flows (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It is noted that the nonlinear partial differential equation for the perturbation velocity potential and boundary conditions describing steady inviscid compressible transonic flow past a thin two-dimensional airfoil can be transformed into a singular integrodifferential equation and that differentiation of the latter yields an integral equation. Two forms of this integral equation currently exist: one for the singularity that is enclosed in an infinitely long strip of vanishing thickness and the other for the singularity that is enclosed in a vanishing circle. In the present article, a more general integral equation is derived by enclosing the singularity in a vanishing rectangular cavity of arbitrary aspect ratio. The two existing forms of this equation are deduced as special cases distinguished by the respective values for the aspect ratio (infinity for the first form and unity for the second).
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; Feb. 197
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  • 28
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    Aerodynamic heat transfer to a hypersonic research aircraft model /X-24C/ at Mach 6 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper reports on results of heat-transfer tests conducted on a 1/29-scale model of the X-24C-12I hypersonic research aircraft configuration in a Mach 6 tunnel at a Reynolds number of thirteen million using the phase-change heat transfer technique. Sequences of phase-change heat transfer pattern photographs are presented showing windward side and leeward side heating processes. Theoretical predictions of dimensionless heat transfer coefficients along a data line on lower fuselage and on fuselage side bracket the experimental values. A turbulent heating theory gives good agreement with data when shifted to a new virtual origin.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 13; Dec. 197
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  • 29
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    Skin friction on a flat perforated acoustic liner (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The report concerns the measurement of friction coefficients of a typical perforated acoustic liner installed in the side of a wind tunnel. The results are compared with measured friction coefficients of a smooth hard wall for the same mean flow velocities in a wind tunnel. At a velocity of 61 m/sec, an increase in the local skin coefficient of only a few percent was observed, but at the highest velocity of 213 m/sec an increase of about 20% was obtained. This velocity is a realistic velocity for turbo-machinery components utilizing such liners, so a loss in performance is to be expected. Some tests were also performed to see if changes in the mean boundary layer induced by imposed noise would result in friction increase, but only at low velocity levels was such an increase in friction noted.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 14; Nov. 197
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  • 30
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    Steady supersonic flowfields with embedded subsonic regions (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Supersonic flow past a blunt body is considered, where the flow contains an embedded subsonic region which lies between the shock wave and the body surface and is bounded by sonic lines from the body to the shock. A numerical approach is taken, which uses a basic finite difference scheme that solves the unsteady fluid dynamic equations in integral form. The unsteady equations are everywhere hyperbolic in time so no distinction need be made between subsonic and supersonic regions. Solutions to the mixed elliptic and hyperbolic steady flow equations are approached asymptotically in time. The method is illustrated for two-dimensional flows.
    Keywords: AERODYNAMICS
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  • 31
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    Flow characteristics in an expansion tunnel as inferred from velocity measurements (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A photoionization technique was used to study flow characteristics in an expansion tunnel. Vertical surveys of the axial component of flow velocity just downstream from the nozzle exit were obtained, and estimates of freestream density were inferred from the velocity measurement technique. The pitot pressure was measured and compared to the average axial component of velocity as a function of time for the two cases when air and CO2 were used as test gases. Vertical velocity and static density profiles at the nozzle exit are presented for the case when CO2 was used as test gas. Experimental results were used to determine the diameter and uniformity of the test core at the nozzle exit and the duration of the quasi-steady flow period. These data are relevant to evaluation of the suitability of operating an expansion tube as an expansion tunnel. The expansion tunnel is an expansion tube with a conical nozzle positioned at the exit of the acceleration section, so that nozzle entrance flow conditions are hypersonic and characterized by hypervelocity.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; Sept
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  • 32
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    Optimum design and performance of Costas receivers containing soft bandpass limiters (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: This paper investigates several key questions concerning the mechanization and design of a Costas receiver for reconstruction of a carrier from a suppressed carrier signal. For baseband NRZ encoded data symbols and a soft bandpass limiter preceding the loop, several design issues which are considered herein and which affect acquisition and tracking performance are: (1) The choice of an IF bandwidth. (2) The optimum choice of the Costas arm filter bandwidths as well as the spectral roll-off characteristics. (3) The optimum choice of loop bandwidth to data rate ratio for a given signal-to-noise ratio. (4) The signal suppression factor and the combined limiter-squaring loss. (5) The variations in loop bandwidth and damping with signal level. (6) The choice of the limiter transfer characteristic. (7) Performance degradation due to the presence of a limiter. Various new results in system design are presented and typical numerical results are given and graphically demonstrated in SNR regions of practical interest. The theory is applicable to the design of carrier reconstruction loops required in the implementation of spread spectrum communication receivers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Aug. 197
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  • 33
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    Polarization loss of a satellite - Data collection sensor link (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It is noted that the stringent economy of data-collection systems consisting of several widely dispersed satellite-monitored sensor platforms can be partially achieved by using an inexpensive linearly polarized antenna on each platform and that due to Faraday rotation of the ionosphere, the satellite antenna must be circularly polarized to avoid a prohibitive polarization loss. The cumulative probability distribution of polarization loss between a linearly polarized platform antenna and an elliptically polarized satellite antenna is computed for satellite-antenna axial ratios of 3 and 4 dB. The results indicate that a polarization loss of 4.5 dB must be expected for a reliability of 85% and an axial ratio of 3 dB. It is suggested that the conventional assignment of a 3-dB polarization loss to the communication link considered may not insure the required link reliability.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-13; July 197
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  • 34
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    Low Reynolds number flow past a blunt axisymmetric body at angle of attack (1977)
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    Publication Date: 2011-08-17
    Description: Low Reynolds number flow of an ideal gas over a blunt axisymmetric body of large half-angle at small angles of attack is investigated, for the case of laminar hypersonic flow. Time-varying viscous shock layer equations describing the flowfield are obtained from the full Navier-Stokes system by keeping terms to second order in the inverse square root of Re in both viscous and inviscid regions; the equations are valid for moderate to high Re. Drag, skin friction, and heating rates were obtained at small (or zero) angles of attack. Conditions experienced by planetary entry probes during the high-altitude (early) legs of an atmospheric entry trajectory are pertinent to the problem.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; Aug. 197
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  • 35
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    Evaluation of flight spoilers for vortex alleviation (1977)
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    Publication Date: 2011-08-17
    Description: The paper describes the facilities and test procedures used in a series of wind-tunnel and full-scale flight investigations of the effectiveness of flight spoilers currently existing on wide-bodied transport jet aircraft when used as trailing vortex hazard alleviation devices. Examples of the results of such studies include the variation of trailing wing rolling-moment coefficient with downstream distance behind a B-747 airplane model with various segments of its flight spoilers deflected 45 deg, and comparisons with models without spoilers deflected. It is concluded that the existing flight spoilers on the B-747 are effective as trailing vortex attenuators.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 14; Aug. 197
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  • 36
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    The effect of ablation injection on radiative and convective heating (1977)
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    Publication Date: 2011-08-17
    Description: A viscous shock-layer analysis for calculating high energy equilibrium flow fields about blunt axisymmetric bodies is applied to the problem of massive ablation injection with radiation transport. A nongray radiation model is used that accounts for both line and continuum radiation. The solution method is direct and provides both stagnation and downstream solutions. Results for shock heated air show that phenolic-nylon injection is substantially more effective in reducing the wall radiant flux than air injection. Also, for large included body angles, the wall radiative flux and the coupled phenolic-nylon injection rate do not continue to decrease with increasing distance downstream.
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  • 37
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    Comment on 'Drag coefficient of spheres in continuum and rarefied flows' (1977)
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    Publication Date: 2011-08-17
    Description: A paper by Henderson (1976) provides a method of predicting experimental sphere drag data. This approach uses two equations for the drag coefficient, one for relative Mach number less than one, one for relative Mach number greater than 1.75. For relative Mach numbers between these limits a linear interpolation procedure is followed. In a comment on this paper, it is claimed, on the basis of comparing predictions with experimental results, that a method proposed by Walsh (1975) gives better predictions of the drag coefficient for relative Mach numbers less than 1.75, provided that a modification of the procedure is made for relative Mach numbers less than 0.1. For values over 1.75, both methods are considered equally accurate. In a reply to this comment, it is agreed that the Walsh method is more accurate when Reynolds numbers are within a range between 20 and 200, and Mach numbers are between 0.5 and 1.25. Presumed errors and possible limitations in the Walsh procedure for predicting drag coefficients are discussed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; June 197
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  • 38
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    The Communications Technology Satellite /CTS/ Program (1976)
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    Publication Date: 2011-08-17
    Description: The purposes of the joint Canadian-U.S. Communications Technology Satellite (CTS) Program are (1) to conduct satellite communication systems experiments using the 12- and 14-GHz bands and low-cost transportable ground terminals, (2) to develop and flight test a power amplifier tube having a greater than 50% efficiency with a saturated power output of 200 W at 12 GHz, (3) to develop and flight test a lightweight extendible solar array with an initial power output greater than 1 kW, and (4) to develop and flight test a 3-axis stabilization system to maintain accurate antenna boresight positioning on a spacecraft with flexible appendages. Brief descriptions of these experiments and of the ground facilities are provided.
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  • 39
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    Improved interactive calculation procedure for supersonic flows (1976)
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    Publication Date: 2011-08-17
    Description: An interactive numerical procedure has been developed for supersonic viscous flows (either two-dimensional or axisymmetric configurations). The flow field is divided into two regions: (1) an inner region which is highly viscous and mostly subsonic, and (2) an outer region where the flow is supersonic and in which viscous effects are small, but not negligible. This paper presents a detailed description of: I. Outer Region - numerical solution obtained by applying the method of characteristics to a system of equations which includes viscous and conduction transport terms only normal to the streamlines; II. Inner Region - treated by a system of equations of the boundary-layer type that includes higher order effects, such as longitudinal and transverse curvature and normal pressure gradients (equations are coupled and solved simultaneously in physical coordinates, using an implicit finite-difference scheme); III. Interactive Procedure - in the interaction mode, the two regions are coupled iteratively along a matching line, where the Mach number is of the order of 1.2.
    Keywords: AERODYNAMICS
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  • 40
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    Analysis of a discrete spectrum analyzer for the detection of radio frequency interference (1977)
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    Publication Date: 2011-08-17
    Description: As the radio frequency spectrum becomes increasingly overcrowded, interference with mission-critical DSN operations is rising at an alarming rate. To alleviate this problem the DSN is developing a wideband surveillance system for on-site detection and identification of potential sources of radio frequency interference (RFI), which will complement the existing frequency coordination activities. The RFI monitoring system is based on a wideband, multi-look discrete spectrum analyzer operating on fast Fourier transform principles. An extensive general statistical analysis is presented of such spectrum analyzers and derives threshold detection performance formulas for signals of interest. These results are then applied to the design of the RFI spectrum analyzer under development.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 83-98
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  • 41
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    Walsh transforms and signal detection (1977)
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    Publication Date: 2011-08-17
    Description: The detection of signals using Walsh power spectral estimates is analyzed. In addition, a generalization of this method of estimation is evaluated. The conclusion is that Walsh transforms are not suitable tools for the detection of weak signals in noise.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 127-131
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  • 42
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    Radio frequency interference from near-earth satellites (1977)
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    Publication Date: 2011-08-17
    Description: A pessimistic statistical model was developed for predicting the extent of radio frequency interference (RF1). Based on the assumptions underlying the model, DSN S-band operations can expect one RF1 interruption every 4.1 days, with the average incident lasting 24 s. This implies that 52 or more such satellites, with uncorrelated orbital trajectories, will cause in excess of 5 min of RF1 per day at a DSN station.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 69-77
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  • 43
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    Television applications of interline-transfer CCD arrays (1976)
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    Publication Date: 2011-08-17
    Description: The design features and characteristics of interline transfer (ILT) CCD arrays with 190 x 244 and 380 x 488 image elements are reviewed, with emphasis on optional operating modes and system application considerations. It was shown that the observed horizontal resolution for a TV system using an ILT image sensor can approach the aperture response limit determined by photosensor site width, resulting in enhanced resolution for moving images. Preferred camera configurations and read out clocking modes for maximum resolution and low light sensitivity are discussed, including a very low light level intensifier CCD concept. Several camera designs utilizing ILT-CCD arrays are described. These cameras demonstrate feasibility in applications where small size, low-power/low-voltage operation, high sensitivity and extreme ruggedness are either desired or mandatory system requirements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 152-156
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  • 44
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    Television cameras employing solid-state imaging sensors for manned spacecraft applications (1976)
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    Publication Date: 2011-08-17
    Description: The Space Shuttle television system incorporates a versatile complement of TV equipment which allows the positioning, quantity, and performance capabilities of the multiple TV cameras to vary as dictated by the particular mission. However, current TV camera technology employing glass enclosed, vacuum processed image sensors results in a bulky device that restricts its location and versatility. Problems and potential solutions that can be achieved through the employment of solid-state image sensors for both monochrome and color applications are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 126-128
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  • 45
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    Command detector SNR estimator and lock status monitor circuitry (1976)
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    Publication Date: 2011-08-17
    Description: A breadboard of the command detector signal-to-noise-ratio estimator and lock status monitor was built on a wire-wrap card. The breadboard was integrated with the standard command detector, and its performance was measured. The design, design constraints, and construction of the breadboard are described. The performance is shown to agree with the theoretical model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 42-51
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  • 46
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    Influence of nonconservative differencing on transonic streamline shapes (1976)
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    Publication Date: 2011-08-16
    Description: A computer program recently developed by South and Brandt (1976) which contained the Murman (1973) conservative finite-difference scheme is easily modified to use the Garabedian and Korn (1971) nonconservative finite difference scheme. This program solves the transonic small disturbance equation for only symmetric flow, but incorporates several iterative solution techniques. Results are presented for the case where the equally spaced computational grid extended to infinity in both the streamwise and normal directions. Streamline shapes are obtained along several grid lines by a streamwise integration of the normal component of the perturbation velocity. Comparison cases are run for a 10% thick parabolic arc airfoil at zero incidence for freestream Mach numbers of 0, 0.70, 0.84, and 0.95. It is shown that the use of a nonconservative finite-difference scheme in transonic flow calculations destroys the global mass balance when shocks are present. This lack of mass balance may prove to be more crucial in the case of an unconfined external flow.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 14; Aug. 197
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  • 47
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    Vortex lattice prediction of subsonic aerodynamics of hypersonic vehicle concepts (1977)
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    Publication Date: 2011-08-17
    Description: The vortex lattice method introduced by Lamar and Gloss (1975) was applied to the prediction of subsonic aerodynamic characteristics of hypersonic body-wing configurations. The reliability of the method was assessed through comparison of the calculated and observed aerodynamic performances of two National Hypersonic Flight Research Facility craft at Mach 0.2. The investigation indicated that a vortex lattice model involving 120 or more panel elements can give good results for the lift and induced drag coefficients of the craft, as well as for the pitching moment at angles of attack below 10 to 15 deg. Automated processes for calculating the local slopes of mean-camber surfaces may also render the method suitable for use in preliminary design phases.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 14; Oct. 197
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  • 48
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    Cooling effectiveness of slot injection into a turbulent boundary layer (1977)
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    Publication Date: 2011-08-17
    Description: The cooling effectiveness of injection through multiple flush slots at an angle of 10 deg was studied experimentally in a wind tunnel. Air was injected from one to four slots into a turbulent Mach 6 boundary layer. The slot mass flow ratio is defined, and data which describe the dependence of the cooling effectiveness on the slot mass flow ratio are presented. Experimental values are indicated graphically for various cases of single and multiple slot injection, where the total mass injection (i.e., the sum of flow rates from each slot) is the same for each case. The results show that, for a given coolant mass flow rate, thermal protection over the maximum surface area can be accomplished best by injecting the coolant flow through multiple slots.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; Sept
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  • 49
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    The scattering of obliquely incident plane waves from a corrugated conducting surface (1976)
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    Publication Date: 2011-08-17
    Description: A physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface. This solution is used to compute the radar cross section of the surface in the case of backscatter from irregular (i.e., stochastic) corrugations. An interesting feature of the solution is the occurrence of singularities in the scattered fields. These singularities appear to be a manifestation of focusing by the surface at its 'stationary' points. Whether or not the singularities occur in the solution depends on the manner in which one restricts the analysis to the far-field.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Nov. 197
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  • 50
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    Modification of the DSN radio frequency angular tropospheric refraction model (1977)
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    Publication Date: 2011-08-17
    Description: The previously derived DSN Radio Frequency Angular Tropospheric Refraction Model contained an assumption which was subsequently seen to be at a variance with the theoretical basis of angular refraction. The modification necessary to correct the model is minor in that the value of a constant is changed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 184-186
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  • 51
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    Synchronization strategies for RFI channels (1977)
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    Publication Date: 2011-08-17
    Description: An RFI channel to be a multiple-access channel is defined in which no sender can know when any other starts, and the problem of determining the relative phases of the senders at the receiver is studied. A new result is proved about binary DEBruijn sequences.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 103-108
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  • 52
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    Proportionality between Doppler noise and integrated signal path electron density validated by differenced S-X range (1977)
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    Publication Date: 2011-08-17
    Description: Observations of Viking differenced S-band/X-band (S-X) range are shown to correlate strongly with Viking Doppler noise. A ratio of proportionality between downlink S-band plasma-induced range error and two-way Doppler noise is calculated. A new parameter (similar to the parameter epsilon which defines the ratio of local electron density fluctuations to mean electron density) is defined as a function of observed data sample interval (Tau) where the time-scale of the observations is 15 Tau. This parameter is interpreted to yield the ratio of net observed phase (or electron density) fluctuations to integrated electron density (in RMS meters/meter). Using this parameter and the thin phase-changing screen approximation, a value for the scale size L is calculated. To be consistent with Doppler noise observations, it is seen necessary for L to be proportional to closest approach distance a, and a strong function of the observed data sample interval, and hence the time-scale of the observations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 172-183
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  • 53
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    The Deep Space Network-Mariner Jupiter/Saturn 1977 flight project telecommunications compatibility (1977)
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    Publication Date: 2011-08-17
    Description: The DSN-Mariner Jupiter/Saturn 1977 telecommunications compatibility tests conducted during the periods 15-20 November 1976, 7-16 December 1976 and 5 January 1977, are an ongoing series of engineering level tests to determine the flight-ground interface compatibility and performance characteristics between these two systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 16-37
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  • 54
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    Radio frequency boresight analysis of the low cost 64-meter antenna (1976)
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    Publication Date: 2011-08-17
    Description: Configurations (two) of the reflector-only assemblies, using different width backup cones, are analyzed for RF boresight direction changes and wind distortions. The wider backup cone is best for minimum weight; however, there is an optimum weight which minimizes the RF boresight errors for a wind load that produces the maximum pitching moment of both configurations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 128-135
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  • 55
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    Magnitude of 64-m elevation axis movements due to alidade temperature changes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In projected very-long baseline interferometry (VLBI) work a reference point for 64-m antennas is the intersection of the elevation and azimuth axes. A minimum-level effort at DSS 14 to determine the magnitude of the effect of diurnal changes in the temperature of the alidade legs on the height of the elevation axis is described. The thermal expansion between the lowest recorded temperature -3 C (27 F) and the highest, 36 C (97 F), over the period covered was 8.9 mm (0.35 in.).
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 41-44
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  • 56
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    Remote intensity fluctuation measurements with a laser Doppler radar (1976)
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    Publication Date: 2011-08-16
    Description: A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Applied Optics; 15; Sept
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  • 57
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    Vortex shedding from a blunt trailing edge with equal and unequal external mean velocities (1976)
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    Publication Date: 2011-08-16
    Description: A flow-visualization study has shown that strong Karman vortices develop behind the blunt trailing edge of a plate when the free-stream velocities over both surfaces are equal and that the vortices tend to disappear when the surface velocities are unequal. This observation provides an explanation for the occurence and disappearance of certain discrete tones often found to be present in the noise spectra of coaxial jets. Both the vortex formation and the tones occur at a Strouhal number based on the lip thickness and the average of the external steady-state velocities of about 0.2. Results from theoretical calculations of the vortex formation, based on an inviscid incompressible analysis of the motion of point vortices, were in good agreement with the experimental observations.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 75; June 25
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  • 58
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    New sidelobe envelopes for small aperture earth stations (1976)
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    Publication Date: 2011-08-16
    Description: The advent of domestic satellite systems and technological improvements in both space and ground equipment makes the use of small aperture earth stations economically feasible and attractive for broadcast satellite applications. With increasing use of the orbit spectrum, there is some concern that broadcast satellite systems may not be able to obtain satisfactory allocations of this orbit-spectrum resource because of interference considerations. Specifically, interference calculations based on the present envelope result in comparatively large orbit spacings for broadcast satellites. Theoretical and experimental investigations of simple sidelobe suppression techniques, plus an analysis of experimental data on small aperture antennas, indicate that much better sidelobe performance can be obtained with a very small cost or performance penalty.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Broadcasting; BC-22; June 197
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  • 59
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    The input admittance of the rectangular cavity-backed slot antenna (1976)
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    Publication Date: 2011-08-16
    Description: The input admittance of the rectangular cavity-backed slot antenna is investigated. The slot is assumed narrow so that the voltage distribution in its aperture is sinusoidal. Equations which represent the input admittance of this slot, backed by a rectangular cavity in which a single propagating wave is assumed to exist, are given. Calculations based on these representations are compared to available measured data. As the depth of the cavity increased the resonant frequency decreased and the bandwidth became narrower. Input admittance curves as a function of electrical slot length are also presented for several size cavities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; May 1976
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  • 60
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    Selectable polarization at X-band (1977)
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    Publication Date: 2011-08-17
    Description: The X-band feeds in the Deep Space Network were upgraded to include selectable polarization in time for the Voyager missions to the outer planets. The modified antenna feed has the following major items added: two circular waveguide rotary joints, drive motor and gear reducer, gear assembly, two microswitches, and a polarization control junction box. The overall length of the feed remains the same because circular waveguide spacing sections were designed into the original feed to readily permit such modifications. There is no significant increase in antenna noise temperature compared to the original feed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 177-180
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  • 61
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    DSS 13 automated antenna pointing subsystem phase 1 hardware (1977)
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    Publication Date: 2011-08-17
    Description: An automated antenna pointing subsystem (APS) is being installed at DSS 13 as part of the unattended station project. The function of the APS is to track an instructed position with the 26 meter antenna and to monitor the antenna servo system and meteorological conditions to ensure a proper operational environment. This article discusses the now-completed first phase of the digital hardware portion of the APS development.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 100-109
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  • 62
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    X-band antenna gain and system noise temperature of 64-meter deep space stations (1977)
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    Publication Date: 2011-08-17
    Description: A set of measured data on the X-band performance of the three 64-meter deep space stations was obtained for use in future mission telecommunication design and predictions. The test configuration and measurement procedure is described. A method of modelling attenuation due to the atmosphere is given. Radio source brightness temperature and flux density are reviewed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 76-99
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  • 63
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    Investigation of package sealing using organic adhesives (1977)
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    Publication Date: 2011-08-17
    Description: A systematic study was performed to evaluate the suitability of adhesives for sealing hybrid packages. Selected adhesives were screened on the basis of their ability to seal gold-plated Kovar butterfly-type packages that retain their seal integrity after individual exposures to increasingly severe temperature-humidity environments. Tests were also run using thermal shock, temperature cycling, mechanical shock and temperature aging. The four best adhesives were determined and further tested in a 60 C/98% RH environment and continuously monitored in regard to moisture content. Results are given, however, none of the tested adhesives passed all the tests.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Proc. of the 1977 NASA(ISHM Microelectronics Conf.; p 77-94
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    The 26-meter S-X Conversion Project (1977)
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    Publication Date: 2011-08-17
    Description: The 26-meter S-X conversion project provides for the conversion of an existing 26-meter S-band subnet to a 34-meter S- and X-band subnet. The subnet chosen for conversion consists of the following stations: DSS 12 near Barstow, DSS 44 in Australia, and DSS 62 in Spain. The main subsystems effected by this project are the antenna mechanical, antenna microwave, and receiver-exciter. In addition to these, there are many project-related electronic equipments that have been added to the existing station equipment. The major subsystems are essentially through the design stage with the antenna mechanical subsystem completed through detail design with procurement in process.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 157-167
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  • 65
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    Minimum-weight codewords in the (128,64) BCH (1977)
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    Details
    Publication Date: 2011-08-17
    Description: Techniques of combinational algebra and computer simulation are combined to determine the number of weight 22 codewords in the (128,64) BCH code which is being studied for use on future deep-space missions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network p92-94 (SEE N78-24161 15-12)
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    Complex mixer system modifications (1977)
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    Publication Date: 2011-08-17
    Description: Modifications of the complex mixer system to increase bandwidth and number of channels were made. Three modified complex mixers were installed at DSS 14 and were used to process planetary radar signals in March and April of 1977.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 88-91
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  • 67
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    Viking extended mission support (1977)
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    Publication Date: 2011-08-17
    Description: The period from 1 July through 31 August 1977 is covered and included is the remainder of post DSN Mark 3 Data Subsystem Implementation Project Viking-related testing at DSS14. Also included are reports on the Viking DSN Discrepancy Reporting System, Viking command support, tracking support, and periodic tests conducted with the Viking spacecraft.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 28-33
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  • 68
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    Voyager flight project: DSN Telecommunications Compatibility Test Program (1977)
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    Publication Date: 2011-08-17
    Description: The Voyager Flight Project - DSN Telecommunications Compatibility Test Program consisted of three phases: Subsystem Design, System Design, and System Verification Tests. Subsystem Design Tests were performed during mid 1976. System Design Tests were performed during late 1976 and early 1977. System Verification Tests were performed during the spring and summer of 1977. This article describes the System Design Tests and test results that provided the basis for establishment of telecommunications design between the DSN and the Voyager Flight Project.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 13-27
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  • 69
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    DSN radio science system description and requirements (1977)
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    Publication Date: 2011-08-17
    Description: The data system created to collect the functions performed by the Deep Space Network in support of spacecraft radio science experiments is described. Some of the major functional requirements presently being considered for the system are delineated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 119-129
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  • 70
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    EMI survey for maritime satellite 1535-1645-MHz shipboard terminal (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A 15,690-ton commercial container ship was selected as lead ship for an onboard electromagnetic-interference (EMI) survey prior to installation of 1535-1645-MHz (L-Band) shipboard terminals for communication via a maritime satellite. In general, the EMI survey revealed tolerable interference levels on board ship. Radiometer measurements indicate antenna-noise temperatures less than 70 K at elevation angles of 5 deg and greater at 1559 MHz at the output terminals of the 1.2-m diameter parabolic-dish antenna for the L-band shipboard terminal. Other EMI measurements include field intensity from 3-cm and 10-cm wavelength pulse radars, and conducted-emission tests of primary power lines to both onboard radars.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-19; Nov. 197
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  • 71
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    Wall cooling effects on hypersonic transitional/turbulent boundary layers at high Reynolds numbers (1977)
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    Publication Date: 2011-08-17
    Description: The characteristics of a thick hypersonic boundary layer turbulent for a length of 175 cm on a 4 deg sharp wedge were measured. The resulting boundary layer was free from transverse curvature effects and only mildly affected by upstream history effects caused by pressure and wall temperature gradients. Heat-transfer distributions were used to locate regions of laminar, transitional, and turbulent flow at an edge unit Reynolds number of 470,000 cm at wall-to-total temperature ratios from about 0.3 to 1. Wall cooling had little effect on the location of the transition region. Pitot and total temperature profiles and skin-friction measurements were obtained at several locations along the model longitudinal centerline. Mixing length and turbulent Prandtl number distributions were derived from the fully turbulent mean profiles.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; Oct. 197
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  • 72
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    Power conservation for reflector antennas with truncated feed patterns (1976)
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    Publication Date: 2011-08-16
    Description: Reflector-antenna calculations using idealised truncated feed patterns can lead to incorrect values of total secondary radiated power. It is demonstrated that this discrepancy is due to the presence of higher-order spherical modes incident on the reflector. When a proper spherical-wave expansion of the incident field is used, in conjunction with the physical-optics technique, to determine the scattered field, the total power of the scattered field will equal the power radiated by the feed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Electronics Letters; 12; Mar. 18
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  • 73
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    Satellite communications at the Goddard Space Flight Center (1976)
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    Publication Date: 2011-08-16
    Description: Starting with the 1960 Delta launch of the first Echo satellite, NASA's Goddard Space Flight Center (GSFC) became one of the pioneers in satellite communications. Attention is given to the project Syncom, the Applications Technology Satellite (ATS) program, the ATS-6 project, and current GSFC efforts. After the decision announced in January of 1973 that NASA would phase out of communications satellite programs, the communications effort at GSFC concentrates on the operation of ATS spacecraft in orbit, experiments in the 12- to 14 GHz frequency band, and advanced communications research.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Signal; 30; Mar. 197
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  • 74
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    Atmospheric entry into Jupiter's atmosphere in view of recent flyby results (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper examines the heating levels experienced by a probe entering Kliore's (1974) model of Jupiter's atmosphere and compares the results with those of the Jupiter model atmospheres given elsewhere (NASA SP-8069, 1971), with the heating levels of Tauber (1969) and Tauber and Wakefield (1971). The computations are made using a point-mass atmospheric entry trajectory program, i.e., the Allen-Eggers (1958) analysis and simple correlations of heating. Results of heating calculations are compared and discussed. It is found that the warm temperature bulge exists at a level too low in the atmosphere to affect any heating and that the nominal atmosphere fits Kliore's model atmosphere best insofar as heating is concerned. Previous estimates of the heating levels to be expected for a probe entering Jupiter's atmosphere are therefore unaffected by Kliore's postulated atmospheres.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets; 13; Feb. 197
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  • 75
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    Roughness induced transition criteria for space shuttle-type vehicles (1976)
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    Publication Date: 2011-08-16
    Description: Tripping effectiveness of surface roughness on a delta wing shuttle orbiter model at 20 deg angle of attack is compared to that on plane and axisymmetrical bodies with and without longitudinal pressure gradients. The experimental data presented are compared on the basis of effective roughness Reynolds number since this parameter is not sensitive to flow conditions downstream of the roughness. The discussion covers the effective roughness Reynolds number as a function of roughness position Reynolds number, effective size ratio as a function of pressure gradient and distance from vehicle nose, and effect of spanwise roughness position on roughness effectiveness. It is shown that conventional criteria for sizing roughness elements which promote transition in two-dimensional zero-pressure gradient flows are insufficient for high-pressure gradient flows and three-dimensional flows. Roughness much smaller than that given by conventional criteria can cause transition and significantly increase the heating load.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets; 13; Feb. 197
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  • 76
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    Real-time video compression algorithm for Hadamard transform processing (1976)
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    Publication Date: 2011-08-16
    Description: A real-time digital video processor using Hadamard transform techniques to reduce video bandwidth is described. The processor can be programmed with different parameters to investigate various algorithms for bandwidth compression. The processor is also adaptive in that it can select different parameter sets to tradeoff spatial resolution for temporal resolution in the regions of the picture that are moving. Algorithms used in programming the system are described along with results achieved at various levels of compression. The algorithms relate to spatial compression, temporal compression, and the adaptive selection of parameter sets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-18; Feb. 197
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  • 77
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    A complete second-order theory for the unsteady flow about an airfoil due to a periodic gust (1976)
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    Publication Date: 2011-08-16
    Description: A uniformly valid second-order theory is developed for calculating the unsteady incompressible flow that occurs when an airfoil is subjected to a convected sinusoidal gust. Explicit formulas for the airfoil response functions (i.e., fluctuating lift) are given. The theory accounts for the effect of the distortion of the gust by the steady-state potential flow around the airfoil, and this effect is found to have an important influence on the response functions. A number of results relevant to the general theory of the scattering of vorticity waves by solid objects are also presented.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 74; Apr. 22
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  • 78
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    A technique for accelerating iterative convergence in numerical integration, with application in transonic aerodynamics (1976)
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    Publication Date: 2011-08-16
    Description: A technique is described for the efficient numerical solution of nonlinear partial differential equations by rapid iteration. In particular, a special approach is described for applying the Aitken acceleration formula (a simple Pade approximant) for accelerating the iterative convergence. The method finds the most appropriate successive approximations, which are in a most nearly geometric sequence, for use in the Aitken formula. Simple examples are given to illustrate the use of the method. The method is then applied to the mixed elliptic-hyperbolic problem of steady, inviscid, transonic flow over an airfoil in a subsonic free stream.
    Keywords: AERODYNAMICS
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  • 79
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    Inlets for high angles of attack (1976)
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    Publication Date: 2011-08-16
    Description: Different inlet designs for high angle of attack STOL and VTOL applications were tested in a subsonic wind tunnel. Three removable entry lips having contraction ratios of 1.30, 1.34 and 1.38 were tested with a single diffuser. The internal contour of each entry lip was an ellipse with a major to minor axis of 2.0. Each lip and diffuser assembly was tested to determine its tolerance to angle of attack, first with a conventional centerbody and then with an extended centerbody. Results indicate that a large improvement in separation angle (determined as a function of lip contraction ratio and inlet flow) was obtained for the extended centerbody for all contraction ratios. Improved inlet tolerance to angle of attack was obtained by reducing the adverse pressure gradient downstream of the throat.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 13; Apr. 197
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  • 80
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    VLBI (Very Long Baseline Interferometry) instrumental effects, part 1 (1977)
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    Publication Date: 2011-08-17
    Description: Very Long Baseline Interferometry (VLBI) is a method for observation of extragalactic radio sources which appears to have potential for precise long-distance earth surveying, clock synchronization and spacecraft navigation. Many researchers have been working to establish the accuracy of VLBI observations. The intent of the work reported here is to review the principal components of the VLBI instrument in order to estimate and/or bound the systematic error contributions. In this first of a series of articles, the definitions and tools which are needed in order to apply filter transfer-function analysis to the VLBI receiver are established and they are used to estimate the sensitivity of the VLBI receiver to plausible filter variations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 54-80
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  • 81
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    Statistical assessment of speech system performance (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Methods for the normalization of performance tests results of speech recognition systems are presented. Technological accomplishments in speech recognition systems, as well as planned research activities are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 265-284
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  • 82
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    The Army word recognition system (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The application of speech recognition technology in the Army command and control area is presented. The problems associated with this program are described as well as as its relevance in terms of the man/machine interactions, voice inflexions, and the amount of training needed to interact with and utilize the automated system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 207-215
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  • 83
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    Speech systems research at Texas Instruments (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: An assessment of automatic speech processing technology is presented. Fundamental problems in the development and the deployment of automatic speech processing systems are defined and a technology forecast for speech systems is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 289-299
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  • 84
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    Automatic speech recognition research at NASA-Ames Research Center (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A trainable acoustic pattern recognizer manufactured by Scope Electronics is presented. The voice command system VCS encodes speech by sampling 16 bandpass filters with center frequencies in the range from 200 to 5000 Hz. Variations in speaking rate are compensated for by a compression algorithm that subdivides each utterance into eight subintervals in such a way that the amount of spectral change within each subinterval is the same. The recorded filter values within each subinterval are then reduced to a 15-bit representation, giving a 120-bit encoding for each utterance. The VCS incorporates a simple recognition algorithm that utilizes five training samples of each word in a vocabulary of up to 24 words. The recognition rate of approximately 85 percent correct for untrained speakers and 94 percent correct for trained speakers was not considered adequate for flight systems use. Therefore, the built-in recognition algorithm was disabled, and the VCS was modified to transmit 120-bit encodings to an external computer for recognition.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 143-170
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  • 85
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    Multi-user real time word recognition system (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Technological accomplishments in speech recognition systems are presented. A discrete word recognition system which contains an audio spectrum analyzer is described in detail.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 301-304
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  • 86
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    Practical applications of interactive voice technologies: Some accomplishments and prospects (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A technology assessment of the application of computers and electronics to complex systems is presented. Three existing systems which utilize voice technology (speech recognition and speech generation) are described. Future directions in voice technology are also described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 217-234
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  • 87
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    Automatic speech recognition technology development at ITT Defense Communications Division (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: An assessment of the applications of automatic speech recognition to defense communication systems is presented. Future research efforts include investigations into the following areas: (1) dynamic programming; (2) recognition of speech degraded by noise; (3) speaker independent recognition; (4) large vocabulary recognition; (5) word spotting and continuous speech recognition; and (6) isolated word recognition.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 305-316
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  • 88
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    Application of the method of integral relations to laminar boundary layers in three dimensions (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The method of integral relations is extended to general three-dimensional compressible laminar boundary layer flows. The transformation employed to transform the basic three-dimensional compressible boundary layer equations into quasi-incompressible form is an extension of the Howarth transformation. The resulting system of differential equations is integrated numerically by the method of integral relations as proposed by Dorodnitsyn. To demonstrate the accuracy of the method, it is applied to calculation of the parabolic flow over a flat plate and the boundary flow over an infinite yawed cylinder, for which solutions are known. It is then applied to the flow over a flat plate disturbed by a cylinder normal to the plate, for which a finite-difference solution is available for comparison. It is finally applied to calculating the crossflow velocity variation for supersonic flow over a swept wedge.
    Keywords: AERODYNAMICS
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  • 89
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    Frequencies above 10 GHz (1976)
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    Publication Date: 2011-08-17
    Description: The paper discusses some of the problems associated with extending the frequencies used by satellite communication services above 10 GHz. The principal propagation limitation above 10 GHz occurs when precipitation intercepts the earth-space propagation path and causes attenuation and depolarization of the transmitted signal. World attenuation statistics at 12 GHz for earth-space paths are discussed, revealing the effect of climate on attenuation properties. Space diversity is discussed as an effective means of overcoming precipitation-caused attenuation problems.
    Keywords: COMMUNICATIONS AND RADAR
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  • 90
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    A novel concept for subsonic inlet boundary-layer control (1977)
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    Publication Date: 2011-08-17
    Description: A self-bleeding method for boundary layer control is described and tested for a subsonic inlet designed to operate in the flowfield generated by high angles of attack. Naturally occurring surface static pressure gradients are used to remove the boundary layer from a separation-prone region of the inlet and to reinject it at a less critical location with a net performance gain. The results suggest that this self-bleeding method for boundary-layer control might be successfully applied to other inlets operating at extreme aerodynamic conditions.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 14; Apr. 197
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  • 91
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    Mach 6 flowfield survey at the engine inlet of a research airplane (1977)
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    Publication Date: 2011-08-17
    Description: A flowfield survey was conducted to better define the nature of vehicle forebody flowfield at the inlet location of an airframe-integrated scramjet engine mounted on the lower surface of a high-speed research airplane to be air launched from a B-52 and rocket boosted to Mach 6. The tests were conducted on a 1/30-scale brass model in a Mach-6 20-in. wind tunnel at Reynolds number of 11,200,000 based on distance to engine inlet. Boundary layer profiles at five spanwise locations indicate that the boundary layer in the area of the forebody centerline is more than twice as thick as the boundary layer at three outboard stations. It is shown that the cold streak found in heating contours on the centerline of the forebody is caused by a thickening of the boundary layer on the centerline, and that this thickening decreases with angle of attack.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 14; Apr. 197
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  • 92
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    Comparison of numerical and experimental 'conical' flow fields in supersonic corners with compression and/or expansion (1977)
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    Publication Date: 2011-08-17
    Description: The flow field produced by the intersection of two plane solid surfaces in a supersonic stream is a complex interference flow. These flows can be fully compressive, fully expansive, or of mixed compression-expansion nature. This paper presents a comparison of the experimentally obtained flow-field structure in an axial corner with that predicted numerically by using a shock-capturing finite-difference method. The effect of sweep and surface deflection are evaluated, and the general influence of each is presented for the three classes of corner flow. The results show that the numerical method is a valuable aid in understanding the flow structure for simple configurations. In addition, confidence in the numerical method is gained for use in solving more general three-dimensional configurations where the flow is nonconical and several wave interaction may be presented.
    Keywords: AERODYNAMICS
    Type: British Aircraft Corp.
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  • 93
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    Unsteady flow in a supersonic cascade with strong in-passage shocks (1977)
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    Publication Date: 2011-08-17
    Description: Linearized theory is used to study the unsteady flow in a supersonic cascade with in-passage shock waves. We use the Wiener-Hopf technique to obtain a closed-form analytical solution for the supersonic region. To obtain a solution for the rotational flow in the subsonic region we must solve an infinite set of linear algebraic equations. The analysis shows that it is possible to correlate quantitatively the oscillatory shock motion with the Kutta condition at the trailing edges of the blades. This feature allows us to account for the effect of shock motion on the stability of the cascade. Unlike the theory for a completely supersonic flow, the present study predicts the occurrence of supersonic bending flutter. It therefore provides a possible explanation for the bending flutter that has recently been detected in aircraft-engine compressors at higher blade loadings.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 83; Dec. 5
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  • 94
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    Correlation of turbulent shear layer attachment peak heating near Mach 6 (1977)
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    Publication Date: 2011-08-17
    Description: A correlation of new turbulent two-dimensional data and peak heating data for attaching free shear layers is presented for a 2.54-cm and 5.08-cm diam cylindrical leading-edge slab 25.4 cm long, and 7.62 and 10.16 cm wide. A 30.48 x 25.4 cm sharp leading-edge flat plate set at 15 and 20 deg is used to generate plane impinging shocks. The freestream Mach number is 6 and the freestream Reynolds number varies from 3,300,000 to 25,600,000/m. Peak heating is measured on silica-based epoxy models with a phase change coating technique. A comparison of the free shear layer data with the transition data of Birch and Keyes (1972) reveals that the shear layer data are turbulent at attachment. The trend of the data shows that peak heating is strongly affected by the state of development at attachment. As the free shear layers become more fully developed, the data approach the two-dimensional correlation. Persistence of transitional flow structures for supersonic free shear flows is pointed out.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 15; Dec. 197
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  • 95
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    Calculated heating on the afterbody nozzle of a hypersonic aircraft concept (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The present analysis was carried out to estimate the heating levels of the external nozzle of a scramjet/airframe-integrated research aircraft. A parametric examination of the effects of Mach number, reference length, and wall temperature showed that the heating rate distributions are independent of reference length and wall temperature. The initial heating rates obtained for a Mach 6 flight are in the (3 to 8) x 10 to the 5th power W/sq m range. Underlying the entire study is the question of nozzle boundary layer formation and growth, as well as the question of the reference length value that should be used in the computations. It is shown that the reference length is not the dominant factor setting the heating levels; an attempt to bound the actual length was made. A more detailed calculation of the rates requires further work to gain a better understanding of the combustor exit boundary layer.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 14; Dec. 197
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  • 96
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    An analysis technique for microstrip antennas (1977)
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    Publication Date: 2011-08-17
    Description: The paper presents a combined numerical and empirical approach to the analysis of microstrip antennas over a wide range of frequencies. The method involves representing the antenna by a fine wire grid immersed in a dielectric medium and then using Richmond's reaction formulation (1974) to evaluate the piecewise sinusoidal currents on the grid segments. The calculated results are then modified to account for the finite dielectric discontinuity. The method is applied to round and square microstrip antennas.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; Nov. 197
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  • 97
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    S-X conversion for the block 3 receiver--exciter (1977)
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    Publication Date: 2011-08-17
    Description: An S-X conversion modification was designed for the Block 3 receiver-exciter to be used in the 26 meter S-X Conversion Project. The description, design, specifications, and data are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 141-148
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    CCIR papers on telecommunications for deep space research (1977)
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    Publication Date: 2011-08-17
    Description: A brief description is given of United States participation in the process of developing the technical basis for international allocation and regulation of the radio frequency spectrum. The telecommunication requirements for deep space research are considered. Topics include functional requirements, methods and techniques, and equipment characteristics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 162-183
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    Dual coupler configuration at DSS 14 for the Voyager era (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A description is given of the dual coupler configuration which was installed at DSS 14 for station delay calibrations during the Voyager era. The Z correction values determined for these new and previous configurations are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 184-192
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    Analysis of the radiation patterns of reflector antennas (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The development and application of a numerical technique for rapid calculation of the far-field radiation patterns of a reflector antenna from either a measured or computed feed pattern are reported. The reflector is defined by the intersection of a cone with any surface of revolution or an offset sector of any surface of revolution. The feed is assumed to be linearly polarized and can have an arbitrary location. Both the copolarized and the cross-polarized reflector radiation patterns are computed. Calculations using the technique compare closely with measured radiation patterns of a waveguide-fed offset parabolic reflector. Unique features of this technique are freedom from restrictive feed assumptions and the numerical methods used in preparing the aperture-plane electric-field data for integration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Jan. 197
    Format: text
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