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  • Other Sources  (15)
  • 2010-2014  (6)
  • 1985-1989  (9)
  • 1
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    Forbidden coronal iron-like emission in the Puppis A shock front - The effect of inhomogeneities (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: CCD images of the shock front at the eastern rim of Pup A, obtained in the forbidden lines of Fe X (6374 A) and Fe XIV (5303 A), are reported and compared to Einstein high-resolution-image soft X-ray data. The observed part of the remnant is complex, containing density irregularities. Optical and X-ray data are consistent in showing a nearly flat gradient of ionization temperature behind the shock. To determine conditions in the shock, scans of surface brightness across it in the optical lines were compared to surface brightnesses predicted by idealized Sedov models. It was not possible to match both the red and green line scans by a simple, single-component model, and the failure is ascribed to the presence of the density inhomogeneities. This result has important implications for the determination of SNR shock-front models by fitting X-ray data with Sedov models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 318; 370-378
    Format: text
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  • 2
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    Design of a dual fault tolerant space shuttle payload deployment actuator (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: As the Shuttle Transportation System (STS) becomes operational, the number and variety of payloads will increase. The need to deploy these cargo elements will require a variety of unique actuator designs, all of which will have to conform with STS safety policy. For those missions where payload operations extend beyond the payload bay door envelope, this policy deems the prevention of door closure as a catastrophic hazard. As such, it must be controlled by independent, primary and backup methods. The combination of these methods must be two fault tolerant. The design of such an actuator is described. The device consists of a single linear ballscrew with two ballnuts, each bellnut forming an independent actuator using the common ballscrew. The design requirements, concept development, hardware configuration, and fault tolerance rationale are highlighted.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Ames Research Center 19th Aerospace Mech. Symp.; p 305-313
    Format: application/pdf
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  • 3
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    A new methodology for free wake analysis using curved vortex elements (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A method using curved vortex elements was developed for helicopter rotor free wake calculations. The Basic Curve Vortex Element (BCVE) is derived from the approximate Biot-Savart integration for a parabolic arc filament. When used in conjunction with a scheme to fit the elements along a vortex filament contour, this method has a significant advantage in overall accuracy and efficiency when compared to the traditional straight-line element approach. A theoretical and numerical analysis shows that free wake flows involving close interactions between filaments should utilize curved vortex elements in order to guarantee a consistent level of accuracy. The curved element method was implemented into a forward flight free wake analysis, featuring an adaptive far wake model that utilizes free wake information to extend the vortex filaments beyond the free wake regions. The curved vortex element free wake, coupled with this far wake model, exhibited rapid convergence, even in regions where the free wake and far wake turns are interlaced. Sample calculations are presented for tip vortex motion at various advance ratios for single and multiple blade rotors. Cross-flow plots reveal that the overall downstream wake flow resembles a trailing vortex pair. A preliminary assessment shows that the rotor downwash field is insensitive to element size, even for relatively large curved elements.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3958 , NAS 1.26:3958 , CDI-84-6
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  • 4
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    Feasibility of an onboard wake vortex avoidance system (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It was determined that an onboard vortex wake detection system using existing, proven instrumentation is technically feasible. This system might be incorporated into existing onboard systems such as a wind shear detection system, and might provide the pilot with the location of a vortex wake, as well as an evasive maneuver so that the landing separations may be reduced. It is suggested that this system might be introduced into our nation's commuter aircraft fleet and major air carrier fleet and permit a reduction of current landing separation standards, thereby reducing takeoff and departure delays.
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: NASA-CR-187521 , NAS 1.26:187521 , CDI-87-02
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  • 5
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    Forbidden coronal iron line emission in the Puppis A shock front: The effect of inhomogeneities (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We have obtained CCD images of the shock front at the eastern rim of Puppis A in (Fe X) lambda 6374 and (Fe XIV) lambda 5303 and have compared the optical data to Einstein HRI soft X-ray data. The observed part of the remnant is complex, containing density irregularities. Optical and X-ray data are consistent in showing a nearly flat gradient of ionization behind the shock. To determine conditions in the shock, scans of surface brightness across it in the optical lines were compared to surface brightnesses predicted by idealized Sedov models. We were unable to match both the red and green line scans by a simple, single-component model, and have ascribed the failure to the presence of the density inhomogeneities. Our result has important implications for the determination of SNR shock front models by means of fitting X-ray data with Sedov models.
    Keywords: ASTRONOMY
    Type: NASA-TM-89284 , NAS 1.15:89284
    Format: application/pdf
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  • 6
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    Observational study of ion-electron equilibration and of cloud evaporation in supernova remnants under the HEAO-2 guest investigator program (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Observations of three selected supernovae remnants (Cygnus Loop, IC 443, and Puppis A) were made in the forbidden coronal iron lines (Fe X) lambda 6374 and (Fe XIV) lambda 5303. The resulting data was compared quantitatively with Einstein images of the same objects, and an attempt was made to determine (a) the process by which ion and electron energies are equilibrated behind the shock front in the ISM and (b) whether cloud evaporation occurs within the hot remnant interiors. Spatially-resolved X ray emission were modeled for Sedov-Taylor blast wave models of supernovae remnants (SNR) under conditions of non-equlibrium ionization. The computations are intended to provide results that can be directly compared with Einstein high resolution image (HRI) and imaging proportional counter (IPS) data. The computer program for predicting the spatial distribution of HRI and IPS counting rates was completed, and final testing of it had begun.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-179922 , NAS 1.26:179922
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  • 7
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    Influence of the equilibration process in supernova remnant shocks on their X-ray and coronal iron surface brightnesses (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: SNR model computation results have been obtained which indicate that the radial distribution of soft X-ray and forbidden coronal Fe surface brightnesses in adiabatic, middle-aged SNRs can be used as a basis of discrimination for whether the equilibration time is short or long, by comparison with the ionization time-scale. These models are based on a grid of Sedov-Taylor models with time-dependent, nonequilibrium collisional ionization of 13 chemical elements; the two extreme equilibration conditions assumed are T(ion) = T(e) and a Coulomb equilibration of ion and electron temperatures. The models are compared with data taken from X-ray images of the Cygnus Loop and Puppis A.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 66; 99-123
    Format: text
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  • 8
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    Forbidden coronal iron line images of Puppis A - Cloud evaporation or shocked cloud? (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Calibrated CCD images of the eastern X-ray knot in Puppis A, made in the forbidden red and green coronal Fe lines, are discussed. They show the high-temperature gas to have a rich morphology, with the scale of some features approaching the 2.6 arcsec resolution of the data. The pictures have been compared with an Einstein HRI soft X-ray image; there is close correspondence in the position and size of structures seen in the optical forbidden lines and in the X-rays. Located near the shock front a cloud of about 0.4 pc x 0.9 pc dimension shines brilliantly in the 5303 A line. To test the hypothesis that the cloud might be evaporating into the remnant interior, the 5303 A and 6374 A intensity distributions expected for a steady state, one-fluid evaporatig model have been computed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 314; 673-689
    Format: text
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  • 9
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    Predicting Aircraft Spray Patterns on Crops (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Agricultural Dispersion Prediction (AGDISP) system developed to predict deposition of agricultural material released from rotary- and fixed-wing aircraft. AGDISP computes ensemble average mean motion resulting from turbulent fluid fluctuations. Used to examine ways of making dispersal process more efficient by insuring uniformity, reducing waste, and saving money. Programs in AGDISP system written in FORTRAN IV for interactive execution.
    Keywords: MECHANICS
    Type: LAR-13432 , NASA Tech Briefs (ISSN 0145-319X); 10; 3; P. 78
    Format: text
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  • 10
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    Galex and Optical Observations of GW Librae during the Long Decline from Superoutburst (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-08-24
    Description: The prototype of accreting, pulsating white dwarfs (GW Lib) underwent a large amplitude dwarf nova outburst in 2007. We used ultraviolet data from Galaxy Evolution Explorer and ground-based optical photometry and spectroscopy to follow GW Lib for three years following this outburst. Several variations are apparent during this interval. The optical shows a superhump modulation in the months following outburst, while a 19 minute quasi-periodic modulation lasting for several months is apparent in the year after outburst. A long timescale (about 4 hr) modulation first appears in the UV a year after outburst and increases in amplitude in the following years. This variation also appears in the optical two years after outburst but is not in phase with the UV. The pre-outburst pulsations are not yet visible after three years, likely indicating the white dwarf has not returned to its quiescent state.
    Keywords: Astronomy
    Type: AD-A538731
    Format: text
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