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  • Other Sources  (118)
  • AERODYNAMICS  (70)
  • INSTRUMENTATION AND PHOTOGRAPHY  (48)
  • Humans
  • 1985-1989  (118)
  • 1988  (118)
  • 1
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    Advanced altimetry (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The radar altimeter being developed for the Ocean Topography Experiment (TOPEX) will have an inherent instrument precision of 2 to 3 cm. While some minor refinements may be possible in the future, major geophysical advances could be made if altimetric measurements over a wide swath of the Earth's surface were possible. The NASA Headquarters Oceanic Processes Branch is supporting a 3-year investigation of the technological issues inherent in the precision measurement of topography from spaceborne platforms at angles off-nadir. To explore the off-nadir measurement of topography, a flexible, airborne radar instrument system is being developed. Its hardware design is now complete, and it is made up of several subsystems. The antenna selected is a dielectric lens of .894 m diameter. The RF subsystem uses phase-locked oscillators, FET solid-state amplifiers, and times four frequency multipliers to develop a transmit signal at a frequency of 36.0 GHz and a local oscillator signal at a frequency of 35.4 GHz. Lecroy 6880 digitizers under computer control digitize the five receiver outputs. The digital subsystem consists of six single-board Heurikon processors. At this time, the instrument construction continues with final system integration planned for November 1988.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Laboratory for Oceans; p 45-47
    Format: application/pdf
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  • 2
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    Flutter analysis of highly swept delta wings by conventional methods (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The flutter boundaries of six thin highly-swept delta-platform wings have been calculated. Comparisons are made between experimental data and results using several aerodynamic methods. The aerodynamic methods used include a subsonic and supersonic kernel function, second order piston theory, and a transonic small disturbance code. The dynamic equations of motion are solved using analytically calculated mode shapes and frequencies.
    Keywords: AERODYNAMICS
    Type: NASA-TM-101530 , NAS 1.15:101530
    Format: application/pdf
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  • 3
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    Two-mirrored galvanometer laser light sheet generator (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Light sheets generated with either laser or noncoherent sources have found widespread application to flow visualization. Previous light sheet generating systems were usually dedicated to a specific viewing geometry. The technique with the most flexibility is the galvanometer mirror based laser light sheet system. A two-mirrored system was designed and developed to provide flexibility and adaptability to a wide range of applications. The design includes the capability to control the size and location of the laser light sheet in real time, to generate horizontal or vertical sheets, to sweep the sheet repeatedly through a volume, to generate multiple sheets with controllable separation and to rotate single or multiple laser light sheets. The system is capable of producing up to 12 sheets of laser light at an angular divergence of + or - 20 degrees. Maximum scan rate of any one line is 500 Hertz. This system has proven to be uniquely versatile and a patent has been applied for.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 88-4680
    Format: text
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  • 4
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    Radiation heat transfer in the wake of a hypersonic vehicle (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Radiation heat transfer (RHT) from the wake of a hypersonic vehicle to its afterbody is evaluated from Gnoffo and Greene's (1987) calculated wake flowfield and the radiative properties of ionized high-temperature air with the calculated nonequilibrium composition. The 4.2-m aeroassisted flight experiment at an altitude of 75 km and velocity of 8900 m/s causes a 0.1-m-thick layer initially at T = 10,000 K and P = 1 kN/sq m to separate from the shoulder of the forebody heat shield and spread aft to form a wake at approximately T = 5000 K and P = 20 N/sq m. Gas in the separated flow region at approximately T = 3000 K and P = 10 N/sq m, recirculates about the afterbody. It is shown that the radiating layer, recirculating gases, and wake are optically thin for purposes of making engineering RHT calculations. Directional, spectral, and spatial variations of the radiation incident upon the afterbody are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2634
    Format: text
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  • 5
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    Direct and interferometric imaging approaches for detecting earth-like extrasolar planets (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper discusses functional requirements of space-based observational systems with sufficient sensitivity, resolution, and dynamic range to image earth-like extrasolar planets within a search radius of 10 parsecs from the sun. Both direct and interferometric systems operating at visible and infrared wavelengths are evaluated, and the methods used to establish the system tolerances are presented. Due to the more favorable star/planet contrast ratio in the infrared, optical tolerance requirements are less stringent than in the visible. However, reduction of thermal radiation from the telescope requires cooling of the primary optics. Other tradeoffs between various approaches are enumerated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 88-0553
    Format: text
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  • 6
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    Experimental comparison of two hot-wire techniques for resolution of turbulent mass flux and local stagnation temperature in supersonic flow (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The performance of two constant-temperature normal hot-wire techniques in a supersonic flow is examined. The first technique uses a single-wire and rapid scanning of multiple overheat ratios. Time averages of the signals at all overheats are used to separate the mean and rms mass flux, stagnation temperature and their cross-correlation. The second technique uses a dual-wire probe with each wire operating at different overheat ratios, giving instantaneous mass flux and stagnation temperature. Preliminary results indicate that the separation distance (0.18 mm) between the two hot wires in the dual-wire probe does not introduce significant error. However, the rms mass flux inferred from the dual-wire technique is a factor of two higher than that from the single-wire technique.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 88-0422
    Format: text
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  • 7
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    Unsteady shock-induced turbulent separation in Mach 5 cylinder interactions (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Wall pressure fluctuations have been determined under the unsteady separation shock in interactions generated by unswept circular cylinders, using a nominal freestream Mach number of 5 and a freestream unit Reynolds number of 53 x 10 to the 6th/m. The distributions of shock frequency and period were calculated using a conditional sampling algorithm. The shock frequency distributions were all found to be broadband, with frequencies being typically 1-2 kHz. The results support the previous suggestion that pressure fluctuations in the separated flow drive the shock motion.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0305
    Format: text
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  • 8
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    The NASA Langley Laminar-Flow-Control (LFC) experiment on a swept, supercritical airfoil: Design overview (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A large-chord, swept, supercritical, laminar-flow-control (LFC) airfoil was designed and constructed and is currently undergoing tests in the Langley 8 ft Transonic Pressure Tunnel. The experiment was directed toward evaluating the compatibility of LFC and supercritical airfoils, validating prediction techniques, and generating a data base for future transport airfoil design as part of NASA's ongoing research program to significantly reduce drag and increase aircraft efficiency. Unique features of the airfoil included a high design Mach number with shock free flow and boundary layer control by suction. Special requirements for the experiment included modifications to the wind tunnel to achieve the necessary flow quality and contouring of the test section walls to simulate free air flow about a swept model at transonic speeds. Design of the airfoil with a slotted suction surface, the suction system, and modifications to the tunnel to meet test requirements are discussed.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2809 , L-16324 , NAS 1.60:2809
    Format: application/pdf
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  • 9
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    Navier-Stokes calculations using Cartesian grids. I - Laminar flows (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A finite-volume formulation for the Navier-Stokes equations using Cartesian grids is used to study flows past airfoils. In addition to the solution of the complete equations, solutions for two simplified versions of the governing equations were obtained and compared with those using body-fitted grids. Results are presented for two airfoil sections, NACA 0012 and RAE 2822, for a range of Mach numbers, angles of attack, and Reynolds numbers. It is shown that the results are highly dependent on the smoothness of the surface grid. Without such smoothness, the skin friction and pressure converge to nonuniform distributions. On the other hand, when surface cells with smoothly varying areas are used, the results compared favorably with calculations employing body-fitted grids.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 26; 1181-118
    Format: text
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  • 10
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    Computational validation of a parabolized Navier-Stokes solver on a sharp-nose cone at hypersonic speeds (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Perfect gas computational results from a newly-developed upwind, parabolized Navier-Stokes (PNS) solver are compared with an existing set of experimental laminar results for a 10-deg half-angle circular cone at freestream Mach number of 7.95. Comparisons were performed with surface pressure and heat transfer data, as well as with flowfield pitot measurements. The PNS code predicted the surface quantities accurately up through 20-deg angle-of-attack, including crossflow separation, and correctly defined the location of the bow shock and the edge of the boundary layer. The importance of cell Reynolds number, grid density, and thermal boundary conditions to the accurate prediction of the flowfield are examined through numerical emamples.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2566 , AIAA Applied Aerodynamics Conference; Jun 06, 1988 - Jun 08, 1988; Williamsburg, VA; United States
    Format: text
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