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  • Other Sources  (20)
  • 2005-2009
  • 1990-1994  (20)
  • 1980-1984
  • 1965-1969
  • 1930-1934
  • 1990  (20)
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  • 2005-2009
  • 1990-1994  (20)
  • 1980-1984
  • 1965-1969
  • 1930-1934
Year
  • 1
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    Wide-angle astrometry with the Mark III stellar interferometer (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Astrometric measurements made with the Mark III stellar interferometer on five nights in August-September 1988 yielded average formal 1-sigma errors for 12 FK5 stars of 6 mas in declination and 10 mas in right ascension. This improvement in precision over previously reported measurements with this instrument made in 1986 is attributable to several factors: a second 12 m baseline; oriented E-S, was added to the instrument to improve the determination of right ascension; two-color analysis was included in the data-reduction process, along with a new central-fringe identification algorithm using three spectral channels, in order to reduce atmospheric errors; thermal control was greatly improved; and changes were made to observational procedures and hardware to monitor variations in the delay offset due to residual thermal drifts. Approximately half of the new positions are within 50 mas of their FK5 positions. However, an extended series of measurements are needed to ascertain the accuracy that can be achieved by interferometry.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 100; 1701-171
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    World-wide interactive access to scientific databases via satellite and terrestrial data network (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: In order to demonstrate the possibilities for scientific networking and data transfer, a first temporary satellite network link was installed between Czecholovakia and the European space operations center in Darmstadt, during the meeting of the inter-agency consultative group for space science in Prague. Several experiments to show interactive nature of the facility and the capability of the system were carried out, and it was proven that, despite the temporary nature of the installation, the planned demonstrations could be conducted in real time. Demonstrations included electronic mail message, orbit prediction and solar X-ray data. The results of the experiment provided insight into possibilities of data exchange.
    Keywords: DOCUMENTATION AND INFORMATION SCIENCE
    Type: ESA Bulletin (ISSN 0376-4265); 61, Fe; 63-69
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    NASA TECHNICAL REPORTS
  • 3
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    CLEAR: Automating control centers with expert system technology (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Communications Link Expert Assistance Resource (CLEAR) is a fault-isolation expert system to be utilized in the operational environment of the Cosmic Background Explorer (COBE) Mission Operations Room (MOR). CLEAR will assist the COBE Flight Operations Team (FOT) during periods of real-time data acquisition by isolating faults in the spacecraft communication link with the Tracking and Data Relay Satellite (TDRS), providing advice on how to correct them, and logging the events for post-pass evaluation. After a brief introduction to the problem domain, the system requirements, tool selection, development approach, system operation and lessons learned during the transformation of the system from the prototype to the delivered, operation system are described.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA, Lyndon B. Johnson Space Center, Third Annual Workshop on Space Operations Automation and Robotics (SOAR 1989); p 289-293
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Space Shuttle Flight Support Motor no. 1 (FSM-1) (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Space Shuttle Flight Support Motor No. 1 (FSM-1) was static test fired on 15 Aug. 1990 at the Thiokol Corporation Static Test Bay T-24. FSM-1 was a full-scale, full-duration static test fire of a redesigned solid rocket motor. FSM-1 was the first of seven flight support motors which will be static test fired. The Flight Support Motor program validates components, materials, and manufacturing processes. In addition, FSM-1 was the full-scale motor for qualification of Western Electrochemical Corporation ammonium perchlorate. This motor was subjected to all controls and documentation requirements CTP-0171, Revision A. Inspection and instrumentation data indicate that the FSM-1 static test firing was successful. The ambient temperature during the test was 87 F and the propellant mean bulk temperature was 82 F. Ballistics performance values were within the specified requirements. The overall performance of the FSM-1 components and test equipment was nominal.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-184078 , NAS 1.26:184078 , TWR-50068 , PUBL-910801
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    A parametric shell analysis of the shuttle 51-L SRB AFT field joint (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Following the Shuttle 51-L accident, an investigation was conducted to determine the cause of the failure. Investigators at the Langley Research Center focused attention on the structural behavior of the field joints with O-ring seals in the steel solid rocket booster (SRB) cases. The shell-of-revolution computer program BOSOR4 was used to model the aft field joint of the solid rocket booster case. The shell model consisted of the SRB wall and joint geometry present during the Shuttle 51-L flight. A parametric study of the joint was performed on the geometry, including joint clearances, contact between the joint components, and on the loads, induced and applied. In addition combinations of geometry and loads were evaluated. The analytical results from the parametric study showed that contact between the joint components was a primary contributor to allowing hot gases to blow by the O-rings. Based upon understanding the original joint behavior, various proposed joint modifications are shown and analyzed in order to provide additional insight and information. Finally, experimental results from a hydro-static pressurization of a test rocket booster case to study joint motion are presented and verified analytically.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-102748 , NAS 1.15:102748
    Format: application/pdf
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  • 6
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    Spectral determinations for discrete sources with EGRET (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The ability of the EGRET (Energetic Gamma-Ray Experimental Telescope) to determine the spectral parameters of point sources in 14-day exposures, as planned for the initial survey phase of the GRO (Gamma Ray Observatory) mission, is explored by numerical simulation. Results are given for both galactic and extragalactic objects as a function of source strength and for representative levels of diffuse background emission.
    Keywords: ASTRONOMY
    Type: NASA, Goddard Space Flight Center, The Energetic Gamma-Ray Experiment Telescope (EGRET) Science Symposium; p 201-213
    Format: application/pdf
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  • 7
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    Aeroacoustic effects of reduced aft tip speed at constant thrust for a model counterrotation turboprop at takeoff conditions (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A model high-speed, advanced counterrotation propeller, F7/A7, was tested in the NASA Lewis Research Center's 9- by 15-foot anechoic wind tunnel at simulated takeoff and approach conditions of Mach 0.2. The propeller was operated in a baseline configuration with the forward and aft rotor blade setting angles (36.2deg and 35.4 deg) and forward and aft rotational speeds essentially equal. Two additional configurations were tested with the aft rotor at increased blade setting angles and the rotational speed reduced to achieve overall performance similar to that of the baseline configuration. The aft rotor blade angles were adjusted such that the thrust and power absorption for each rotor remained the same as for the baseline configuration. Acoustic data were taken with an axially translating microphone probe that was attached to the tunnel floor. Concurrent aerodynamic data were taken to define propeller operating conditions. The aft rotor fundamental tone was about 6 dB lower with the 36.2 deg and 38.4 deg blade setting angles, and about 9 dB lower with the 36.2 and 41.4 deg blade setting angles. Predicted noise reductions based on tip speed considerations were 5 and 9.5 dB, respectively, for the two altered blade setting angles.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 90-3933
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    A new twist to the solar cycle (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Recent numerical simulations of magnetic buoyancy instabilities suggest a new mechanism for the variation with the solar cycle in the scale and structure of surface magnetic flux. The nonlinear evolution of a predominantly toroidal field is found to depend crucially on the distribution of the weaker poloidal ingredient. For certain field configurations large, helical magnetic fragments are produced; for others the escaping field is small-scale and untwisted. We propose that the observed structural variations in flux may be accounted for by small changes in the twist of a deep-seated field. The large fragments will appear at the surface as active regions, which dominate at solar maximum, while the small-scale field will emerge as ephemeral regions which constitute practically all of the flux at solar minimum.
    Keywords: SOLAR PHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); p. 6P-9P.
    Format: text
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  • 9
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    Lunar occultations for gamma-ray source measurements (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The unambiguous association of discrete gamma-ray sources with objects radiating at other wavelengths, the separation of discrete sources from the extended emission within the Galaxy, the mapping of gamma-ray emission from nearby galaxies and the measurement of structure within a discrete source cannot presently be accomplished at gamma-ray energies. In the past, the detection processes used in high-energy gamma-ray astronomy have not allowed for good angular resolution. This problem can be overcome by placing gamma-ray detectors on the moon and using the horizon as an occulting edge to achieve arcsec resolution. For purposes of discussion, this concept is examined for gamma rays above 100 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.
    Keywords: ASTRONOMY
    Type: Astrophysics from the Moon; Feb 05, 1990 - Feb 07, 1990; Annapolis, MD; United States
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  • 10
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    Arcsec source location measurements in gamma-ray astronomy from a lunar observatory (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The physical processes typically used in the detection of high energy gamma-rays do not permit good angular resolution, which makes difficult the unambiguous association of discrete gamma-ray sources with objects emitting at other wavelengths. This problem can be overcome by placing gamma-ray detectors on the moon and using the horizon as an occulting edge to achieve arcsec resolution. For the purpose of discussion, this concept is examined for gamma rays above about 20 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.
    Keywords: ASTRONOMY
    Type: NASA Workshop; May 19, 1989 - May 20, 1989; Stanford, CA; United States
    Format: text
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