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  • AERODYNAMICS  (307)
  • ASTRONOMY  (214)
  • 2020-2024
  • 1985-1989  (510)
  • 1955-1959  (11)
  • 1
    Publication Date: 2013-08-31
    Description: The Langley Research Center has a concentrated and directed effort under way to develop both conventional and non-intrusive diagnostic instrumentation. These instruments are being developed to operate over large Mach number, total temperature, and total pressure ranges. Efforts are being made to evaluate the measurements made by the various instruments to determine the most accurate and reliable instrument to be used under a given flow environment. Although only one flow visualization technique was described, there are many different types presently being used at Langley Research Center.
    Keywords: AERODYNAMICS
    Type: Langley Symposium on Aerodynamics, Volume 1; p 279-310
    Format: application/pdf
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  • 2
    Publication Date: 2019-06-28
    Description: Tollmien-Schlichting (TS) and cross-flow (CF) instability growth characteristics were studied in three dimensions, for the case of a Mach 2.4 SST with double-delta planform whose inboard leading-edge is subsonic and outboard leading-edge is supersonic. Attention is given to the requirements for supersonic speed laminarization of both highly swept, rounded leading-edge wings and moderately-swept, sharp leading-edge wings. Suction requirements for the control of both TS and CF instabilities are calculated; it is found that while mild suction and surface cooling are effective in TS-instability damping, the CF influence of such techniques is rather weak. CF instability control must be via pressure-distribution tailoring and suction.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0036
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  • 3
    Publication Date: 2006-02-14
    Description: It is well recognized and accepted that the interpretation and analysis of any type of remote planetary spectroscopic observation requires that basic molecular parameters be available. Furthermore, the newly developed capabilities of air, ground, and space borne spectrometers trained on bodies in the solar system are producing results which are extremely difficult to understand on the basis of available data. This is particularly true in the case of spectral features arising from gases and volatiles condensed as ices. With the objective to continue to extend the understanding of spectroscopic observations of solar system objects (including comets) , laboratory studies of both gas phase molecules and ices and dusts are proposed.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 167-168
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  • 4
    Publication Date: 2006-02-14
    Description: Some 34 radio observatories in 18 countries are participating in the Radio Science Net of the International Halley Watch. Approximately 100 radio astronomers are contributing to this effort, which has included observations of comets P/Crommelin and P/Giacobini-Zinner as well as P/Halley. It is clear that the record of data for the 18 cm OH ground state lambda doublet, which provides fundamental information on the gas production rate, kinematics, and potentially the magnetic field in the coma, will be vastly more complete and of higher accuracy than has even been obtained on any previous comet. The coverage by a number of radio observatories will enable short period variations to be studied and correlated with simultaneous data obtained at other wavelengths. Likewise, the first definitive detection of the important parent molecule hydrogen cyanide in a comet was obtained and is being studied by groups in the United States, Sweden, and France. The first detection of the comet with the Very Large Array telescope operated by NRAO was achieved and has produced exciting results for the distribution of emission at high angular resolution from the OH radical. At this writing data are still being obtained and being processed, and there are still strong indications that exciting information will be obtained from radar studies of P/Halley and from searches for additional parent molecules.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 177-178
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  • 5
    Publication Date: 2011-08-19
    Description: A comparison of the available sample of lightcurves for 26 Trojan and Hilda asteroids with belt asteroid lightcurves shows the former to be distinguished by a higher incidence of high amplitudes rgan belt asteroids of comparable size, suggesting more elongated shapes; they currently have, moreover, only a few percent of the main-belt asteroids' collision frequency. A more modest collisional evolution that may have affected the relative degree of fragmentation of these bodies, and thus their shapes, is inferred.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 487-498
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  • 6
    Publication Date: 2011-08-19
    Description: Studies being undertaken in order to interconnect the three principal celestial coordinate systens are reviewed. These systems are the optical frame (FK4/FK5) based on positions of Galactic stars, the planetary/lunar ephemeris frame based on the major celestial bodies of the solar system, and the radio frame constructed from observations of quasars. The optical frame is being connected to the radio frame by VLBI observations of radio-emitting stars, and the radio frame is being tied to the ephemeris frame in several ways; for example, differential VLBI measurements between quasars and planet-orbiting spacecraft. Prospects for future interconnection studies are briefly discussed.
    Keywords: ASTRONOMY
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  • 7
    Publication Date: 2011-08-19
    Description: The results from the X-ray observations of two BL Lacertae objects, H2155-304 and PKS0548-322, are presented. The observations were carried out with the HEAO-1 A2 Low Energy Detectors, the High Resolution Imager, and the Monitor Proportional Counter aboard the Einstein Observatory. Correlated X-ray intensity variations of about 20 percent in the 0.15-3.5 keV energy band and about 40 percent in the 1.5-10 keV energy band are observed in H2155-304 over a period of about 8 hr. A factor of two change in the intensity of PKS0548-322 in the 3.5-10 keV energy interval is also detected over a time interval of 1 hr. Variations in the X-ray intensity over a timescale of months and the hardening of the spectrum with increasing intensity are seen in the HEAO-1 A2 data on H2155-304. The shortest observed timescale for the variability is used to derive an upper limit on the mass of the central accreting source in the two BL Lac objects studied here.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 227; 525-534
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  • 8
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 22; 756-762
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  • 9
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 22; 193-199
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  • 10
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    In:  Other Sources
    Publication Date: 2011-08-19
    Description: A computational method for designing shock-free, quasi-three-dimensional, transonic, turbomachinery blades is described. Shock-free designs are found by implementing Sobieczky's fictitious gas principle in the analysis of a baseline shape, resulting in an elliptic solution that is incorrect in the supersonic domain. Shock-free designs are obtained by combining the subsonic portion of this solution with a characteristic calculation of the correct supersonic flow using the sonic line data from the fictitious elliptic solution. This provides a new, shock-free blade design. Examples presented include the removal of shocks from two blades in quasi-three-dimensional flow and the development of a series of shock-free two-dimensional stators. The new designs all include modifications to the upper surface of an experimental stator blade developed at NASA Lewis Research Center. While the designs presented here are for inviscid flow, the same concepts have been successfully applied to the shock-free design of airfoils and three-dimensional wings with viscous effects. The extension of the present method to viscous flows is straightforward given a suitable analysis algorithm for the flow.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 249-253
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