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  • 1
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    Diffusion bonding of IN 718 to VM 350 grade maraging steel (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Diffusion bonding studies have been conducted on IN 718, VM 350 and the dissimilar alloy couple, IN 718 to maraging steel. The experimental processing parameters critical to obtaining consistently good diffusion bonds between IN 718 and VM 350 were determined. Interrelationships between temperature, pressure and surface preparation were explored for short bending intervals under vacuum conditions. Successful joining was achieved for a range of bonding cycle temperatures, pressures and surface preparations. The strength of the weaker parent material was used as a criterion for a successful tensile test of the heat treated bond. Studies of VM-350/VM-350 couples in the as-bonded condition showed a greater yielding and failure outside the bond region.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA. Langley Res. Center Proc. of the Symp. on Welding, Bonding, and Fastening; 27 p
    Format: application/pdf
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  • 2
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    Advanced Prop-fan Engine Technology (APET) single- and counter-rotation gearbox/pitch change mechanism (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The preliminary design of advanced technology (1992) turboprop engines for single-rotation prop-fans and conceptual designs of pitch change mechanisms for single- and counter-rotation prop-fan application are discussed. The single-rotation gearbox is a split path, in-line configuration. The counter-rotation gearbox is an in-line, differential planetary design. The pitch change mechanisms for both the single- and counter-rotation arrangements are rotary/hydraulic. The advanced technology single-rotation gearbox yields a 2.4 percent improvement in aircraft fuel burn and a one percent improvement in operating cost relative to a current technology gearbox. The 1992 counter-rotation gearbox is 15 percent lighter, 15 percent more reliable, 5 percent lower in cost, and 45 percent lower in maintenance cost than the 1992 single-rotation gearbox. The pitch controls are modular, accessible, and external.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-168114-VOL-2 , NAS 1.26:168114-VOL-2 , PWA-5869-88-VOL-2
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  • 3
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    Advanced Prop-fan Engine Technology (APET) single- and counter-rotation gearbox/pitch change mechanism (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The preliminary design of advanced technology (1992) prop-fan engines for single-rotation prop-fans, the conceptual design of the entire propulsion system, and an aircraft evaluation of the resultant designs are discussed. Four engine configurations were examined. A two-spool engine with all axial compressors and a three-spool engine with axial/centrifugal compressors were selected. Integrated propulsion systems were designed in conjunction with airframe manufacturers. The design efforts resulted in 12,000 shaft horsepower engines installed in over the installations with in-line and offset gearboxes. The prop-fan powered aircraft used 21 percent less fuel and cost 10 percent less to operate than a similar aircraft powered by turbofan engines with comparable technology.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-168114-VOL-1 , NAS 1.26:168114-VOL-1 , PWA-5869-88-VOL-1
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  • 4
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    Scheduling language and algorithm development study. Volume 3, phase 2: As-built specifications for the prototype language and module library (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Detailed specifications of the prototype language and module library are presented. The user guide to the translator writing system is included.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-144530 , MCR-75-390-VOL-3
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  • 5
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    Scheduling language and algorithm development study. Volume 1, phase 2: Design considerations for a scheduling and resource allocation system (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Data and analyses related to a variety of algorithms for solving typical large-scale scheduling and resource allocation problems are presented. The capabilities and deficiencies of various alternative problem solving strategies are discussed from the viewpoint of computer system design.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-144528 , MCR-75-390-VOL-1
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  • 6
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    The Milli-Arc-Second Structure Imager, MASSIM: A New Concept for a High Angular Resolution X-ray Telescope (2008)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: MASSIM, the Milli-Arc-Second Structure Imager, is a mission that has been proposed for study within the context of NASA's "Astrophysics Strategic Mission Concept Studies" program. It uses a set of achromatic diffractive-refractive Fresnel lenses on an optics spacecraft to focus 5-11 keV X-rays onto detectors on a second spacecraft flying in formation 1000 km away. It will have a point-source sensitivity comparable with that of the current generation of major X-ray observatories (Chandra, XMM-Newton) but an angular resolution some three orders of magnitude better. MASSIM is optimized for the study of jets and other phenomena that occur in the immediate vicinity of black holes and neutron stars. It can also be used for studying other astrophysical phenomena on the milli-arc-second scale, such as those involving proto-stars, the surfaces and surroundings of nearby active stars and interacting winds. After introducing the principle of diffractive imaging in the x-ray/gamma-ray regime, the MASSIM mission concept and baseline design will be described along with a discussion of the options and trade-offs within the X-ray optics design.
    Keywords: Astrophysics
    Type: SPIE Conference; Jun 23, 2008 - Jun 28, 2008; Marseille; France
    Format: text
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  • 7
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    An Extended Multi-Zone Model for the MCG-6-30-15 Warm Absorber (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The variable warm absorber seen with ASCA in the X-ray spectrum of MCG 6-30-15 shows complex time behaviour in which the optical depth of O VIII anticorrelates with the flux whereas that of O VII is unchanging. The explanation in terms of a two zone absorber has since been challenged by BeppoSAX observations. These present a more complicated behaviour for the O VII edge. The explanation we offer for both ASCA and BeppoSAX observations requires a very simple photoionization model together with the presence of a third, intermediate, zone and a period of very low luminosity. In practice warm absorbers are likely to be extended, multi-zone regions of which only part causes directly observable absorption edges at any given time depending on the value of the luminosity.
    Keywords: Astrophysics
    Type: Astrophysical Plasmas: Codes, Models, and Observations; 9; 334-335
    Format: text
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  • 8
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    An Extreme X-ray Disk Wind in the Black Hole Candidate IGR J17091-3624 (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Chandra spectroscopy of transient stellar-mass black holes in outburst has clearly revealed accretion disk winds in soft, disk-dominated states, in apparent anti-correlation with relativistic jets in low/hard states. These disk winds are observed to be highly ionized. dense. and to have typical velocities of approx 1000 km/s or less projected along our line of sight. Here. we present an analysis of two Chandra High Energy Transmission Grating spectra of the Galactic black hole candidate IGR J17091-3624 and contemporaneous EVLA radio observations. obtained in 2011. The second Chandra observation reveals an absorption line at 6.91+/-0.01 keV; associating this line with He-like Fe XXV requires a blue-shift of 9300(+500/-400) km/ s (0.03c. or the escape velocity at 1000 R(sub schw)). This projected outflow velocity is an order of magnitude higher than has previously been observed in stellar-mass black holes, and is broadly consistent with some of the fastest winds detected in active galactic nuclei. A potential feature at 7.32 keV, if due to Fe XXVI, would imply a velocity of approx 14600 km/s (0.05c), but this putative feature is marginal. Photoionization modeling suggests that the accretion disk wind in IGR J17091-3624 may originate within 43,300 Schwarzschild radii of the black hole, and may be expelling more gas than accretes. The contemporaneous EVLA observations strongly indicate that jet activity was indeed quenched at the time of our Chandra observations. We discuss the results in the context of disk winds, jets, and basic accretion disk physics in accreting black hole systems
    Keywords: Astrophysics
    Type: GSFC.JA.6983.2012
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  • 9
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    On the Determination of the Spin of the Black Hole in Cyg X-1 from X-Ray Reflection Spectra (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The spin of Cygnus X-I is measured by fitting reflection models to Suzaku data covering the energy band 0.9-400 keY. The inner radius of the accretion disc is found to lie within 2 gravitational radii (rg = GM/c(exp 2)) and a value for the dimensionless black hole spin is obtained of 0.97(sup .0.14) (sup -0.02). This agrees with recent measurements using the continuum fitting method by Gou et al. and of the broad iron line by Duro et al. The disc inclination is measured at 23.7(sup +6.7) (sup -5.4) deg. which is consistent with the recent optical measurement of the binary system inclination by Orosz et al of 27+/- 0.8 deg. We pay special attention to the emissivity profile caused by irradiation of the inner disc by the hard power-law source. 1be X-ray observations and simulations show that the index q of that profile deviates from the commonly used, Newtonian, value of 3 within 3r(sub g), steepening considerably within 2r(sub g). as expected in the strong gravity regime.
    Keywords: Astronomy
    Type: GSFC.JA.00374.2012
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  • 10
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    X-ray Reflected Spectra from Accretion Disk Models. III. A Complete Grid of Ionized Reflection Calculations (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: We present a new and complete library of synthetic spectra for modeling the component of emission that is reflected from an illuminated accretion disk. The spectra were computed using an updated version of our code xillver that incorporates new routines and a richer atomic data base. We offer in the form of a table model an extensive grid of reflection models that cover a wide range of parameters. Each individual model is characterized by the photon index Gamma of the illuminating radiation, the ionization parameter zeta at the surface of the disk (i.e., the ratio of the X-ray flux to the gas density), and the iron abundance A(sub Fe) relative to the solar value. The ranges of the parameters covered are: 1.2 〈= Gamma 〈= 3.4, 1 〈= zeta 〈= 104, and 0.5 〈= A(sub Fe) 〈= 10. These ranges capture the physical conditions typically inferred from observations of active galactic nuclei, and also stellar-mass black holes in the hard state. This library is intended for use when the thermal disk flux is faint compared to the incident power-law flux. The models are expected to provide an accurate description of the Fe K emission line, which is the crucial spectral feature used to measure black hole spin. A total of 720 reflection spectra are provided in a single FITS file suitable for the analysis of X-ray observations via the atable model in xspec. Detailed comparisons with previous reflection models illustrate the improvements incorporated in this version of xillver.
    Keywords: Astronomy
    Type: GSFC-E-DAA-TN9645
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