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  • ASTROPHYSICS  (126)
  • AIRCRAFT DESIGN, TESTING AND PERFORMANCE
  • 2020-2023
  • 1980-1984  (159)
  • 1940-1944
  • 1980  (159)
  • 1
    Publication Date: 2019-06-28
    Description: Nine X-ray outbursts from the LMC have been observed with the HEAO 1 Large-Area Sky Survey Instrument. Some are shown to originate in the recurrent transient A0538-66, confirming the proposed 16 day periodicity and showing that the duration of the events can be as long as 14 days or as short as a few hours. Deviations from precise periodicity can be attributed to phase jitter or to a change in period occurring around the time of an exceptionally long outburst. Other outbursts which are irregular and consistently shorter originate in LMC X-4. A long-term light curve indicates that the LMC X-4 outbursts occur only when the source is in a high state, but are not strongly correlated with the binary phase.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
    Format: text
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  • 2
    Publication Date: 2019-06-27
    Description: The paper presents a 1-10-keV survey of distance class 4, 5, and 6 Abell clusters using the HEAO 1 NRL large area survey experiment. The survey is a little less than 1/30 of the Abell catalog. Eleven clusters are identified with X-ray sources, and X-ray upper limits are provided for 60 others.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 235
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  • 3
    Publication Date: 2019-06-27
    Description: The paper deals with spectrophotometric observations covering the essentially complete wavelength interval between 1.2 and 30.0 microns. The observations confirm the identification of the C3 band at 5.2 microns. They show that if SiC2 is present, the SiC1 absorption band at 5.7 microns would be obscured by C3 at a 1% spectral resolution. Silicon carbide emission at 11.5 microns exists simultaneously with C3 absorption at 5.2 microns, requiring a contribution of both species to the violet opacity of Y CVn.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 235
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  • 4
    Publication Date: 2019-07-13
    Description: The helicopter Microwave Landing System flight-test investigations, conducted by a joint NASA/FAA effort in order to gather statistical data for establishing terminal instrument procedures criteria, and to provide a performance data base for developing advanced MLS guidance concepts, are presented. The specific flight-test objectives were to: (1) develop acceptable angle-only MLS approach profiles; (2) determine tracking errors; (3) determine altitude loss during missed approach; (4) evaluate guidance display sensitivities; and (5) evaluate pilot acceptability. Fourteen pilots flew 140 manual (without stability augmentation) dual-pilot simulated instrument approaches in a UH-1H helicopter. The flight profiles flown included 3-, 6-, and 9-degree glideslope, centerline approaches to decision heights of 50, 100, and 150 ft, respectively. The angular guidance display sensitivities and the data acquisition system are also described. Eight major conclusions are made, and include the following: (1) the use of pitch attitude to control airspeed and collective to control glideslope was the preferred pilot technique for the steep glideslope approaches, and (2) angular guidance deviation indicator sensitivity requirements for helicopter MLS approaches to STOLports and heliports have been found to be significantly different from standard ILS sensitivities.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AHS 80-55 , Annual Forum of the American Helicopter Society; May 13, 1980 - May 15, 1980; Washington, DC
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  • 5
    Publication Date: 2011-08-18
    Description: Spectroscopy and polarimetry of several very red stars, noted on Near Infrared Photographic Sky Survey photographs in the region of NGC 1333, have yielded a 'map' suggesting the extent of polarization arising from a two-cloud structure in the region. Spectral types and color indices of the stars make it possible to infer that grain radii in the clouds exceed typical interstellar medium values and, further, that they increase with optical depth into the cloud. The present observations indicate that the cloud structure is far more extensive than previously realized.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 85; Dec. 198
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  • 6
    Publication Date: 2011-08-17
    Description: A binary star model is used to account for the 16.59-d flaring behavior of the X-ray emission from Circinus X-1. The orbital eccentricity of 0.8 + or - 0.1 is derived from the X-ray light curve by assuming that the sharp X-ray cut-off every 16.59-d is a result of bound-free absorption in the primary star's stellar wind. The shape of the light curve has changed over the last eight years, and this is interpreted as due to orbital precession of the binary system. Simultaneous radio and X-ray observations of the flare from Circinus X-1 on February 1-5, 1978 are reported. These are accounted for within the framework of the model. The radio observations at 5 GHz are used independently to derive a high value of the orbital eccentricity (e = 0.7).
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 86; 3, Ju; July 198
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  • 7
    Publication Date: 2011-08-17
    Description: In response to recent concerns over possibly high ozone levels in the cabins of aircraft flying in the stratosphere, simultaneous measurements of the cabin and ambient ozone levels have been made as part of the NASA Global Atmospheric Sampling Program. Examples of the data taken on commercially operated Boeing 747-100 and 747SP airplanes are given for selected flights, together with summary statistics of over 5600 observations. Cabin ozone levels vary with the ambient level and, for unmodified aircraft, are higher on the 747SP than on the 747-100. Modifications to the ventilation system of the 747SP reduced cabin ozone levels by varying amounts up to a factor of 14.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Aircraft; 17; Apr. 198
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  • 8
    Publication Date: 2016-06-07
    Description: The impact of cruise speed on technology level for certain aircraft components is examined. External-compression inlets were compared with mixed compression, self starting inlets at cruise Mach numbers of 2.0 and 2.3. Inlet engine combinations that provided the greatest aircraft range were identified. Results show that increased transonic to cruise corrected air flow ratio gives decreased range for missions dominated by supersonic cruise. It is also found important that inlets be designed to minimize spillage drag at subsonic cruise, because of the need for efficient performance for overland operations. The external compression inlet emerged as the probable first choice at Mach 2.0, while the self starting inlet was the probable first choice at Mach 2.3. Airframe propulsion system interference effects were significant, and further study is needed to assess the existing design methods and to develop improvements.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Langley Research Center Supersonic Cruise Res., 1979, pt. 1; p 391-411
    Format: application/pdf
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  • 9
    Publication Date: 2019-06-28
    Description: Ultraviolet observations of nearby galaxies with the ANS are used to derive ultraviolet spectra for different galaxy types. These spectra are used with existing visible spectrophotometry to calculate K-corrections, and to predict colors and magnitudes for various galaxy types as a function of redshifts, to z = 2. No evolutionary effects are considered. It appears that the first-ranked cluster galaxies on blue emulsions should be spirals for z greater than or approximately equal to 0.5.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 43; July 198
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  • 10
    Publication Date: 2019-06-28
    Description: New UBVRI photometry of Mrk 421 obtained during periods of X-ray satellite observations are presented. An X-ray light curve for 1977 November from the HEAO A-1 experiment is also given. The decomposition of the UBVR fluxes into a compact nonthermal component and an extended galactic component shows that there are coordinated variations in the optical nonthermal and X-ray emission. The data are consistent with the hypothesis that the mini-BL Lac object is emitting by the synchrontron-self-Compton process. The host galaxy of this composite source has properties like those of a giant elliptical.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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