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  • 1
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    The early ultraviolet spectral evolution of Nova Cygni 1992 (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We report on the high resolution ultraviolet line profile evolution of Nova Cygni 1992 using the International Ultraviolet Explorer (IUE) satellite and the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). Our observations cover the period from discovery in 1992 February through 1993 April. The initial expansion velocity, derived from P Cyg profiles on Mg II and other resonance lines, was about 4500 km/s. All resonance transitions displayed P Cyg profiles around the time of UV maximum. We first discuss the spectral development as the initially optically thick atomic absorption curtain became optically thin. We then present the interpretation of the nebular spectral stage. The high resolution line profiles show that the shell rapidly developed nearly symmetric knots, or filaments, of emission. The optically thin transitions show an emission weighted expansion velocity of about 1800 km/s, consistent with the velocity inferred from the radio and infrared data. The emission lines display a symmetric set of filaments that appeared as soon as the line profiles became optically thin. The GHRS observations demonstrate that the filaments were located in the inner, slower moving parts of the ejecta. These probably record an initial low wave number instability imposed on the ejecta at the time of outburst. We suggest that the likely cause is a Rayleigh-Taylor instability. The emission at later stages is dominated by the filaments and, since this phenomenon is seen in virtually all novae, nebular line formation codes will have to account for the density inhomgeneities in order to adequately determine abundances for nove ejecta.
    Keywords: ASTRONOMY
    Type: The Astronomical Journal (ISSN 0004-6256); 106; 6; p. 2408-2428
    Format: text
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  • 2
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    Green Propulsion Technologies for Advanced Air Transports (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Air transportation is critical to U.S. and Global economic vitality. However, energy and climate issues challenge aviations ability to be sustainable in the long term. Aviation must dramatically reduce fuel use and related emissions. Energy costs to U.S. airlines nearly tripled between 1995 and 2011, and continue to be the highest percentage of operating costs. The NASA Advanced Air Transports Technology Project addresses the comprehensive challenge of enabling revolutionary energy efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advanced technologies and the development of unconventional aircraft systems offer the potential to achieve these improvements. The presentation will highlight the NASA vision of revolutionary systems and propulsion technologies needed to achieve these challenging goals. Specifically, the primary focus is on the N+3 generation; that is, vehicles that are three generations beyond the current state of the art, requiring mature technology solutions in the 2025-30 timeframe, which are envisioned as being powered by Hybrid Electric Propulsion Systems.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN23468 , AIAA Distinguished Lectureship; May 12, 2015; Cleveland, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Electrified Aircraft Propulsion Development (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The benefits of electrified aircraft propulsion improves aircrafts like single aisle transports, enables new configurations of vertical take-off landing aircrafts and revitalizes the economic case for small short-range aircraft services. Future strategies and markets for supersonic and commercial transport are proposed.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN58749 , AIAA Propulsion & Energy Forum; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Green Propulsion Technologies for Advanced Air Transports (2015)
    In:  CASI
    Details
    Publication Date: 2019-09-20
    Description: Air transportation is critical to U.S. and Global economic vitality. However, energy and climate issues challenge aviation's ability to be sustainable in the long term. Aviation must dramatically reduce fuel use and related emissions. Energy costs to U.S. airlines nearly tripled between 1995 and 2011, and continue to be the highest percentage of operating costs. The NASA Advanced Air Transports Technology Project addresses the comprehensive challenge of enabling revolutionary energy efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advanced technologies and the development of unconventional aircraft systems offer the potential to achieve these improvements. The presentation will highlight the NASA vision of revolutionary systems and propulsion technologies needed to achieve these challenging goals. Specifically, the primary focus is on the N+3 generation; that is, vehicles that are three generations beyond the current state of the art, requiring mature technology solutions in the 2025-30 timeframe.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN20707 , OSU Aerospace Graduate Student Seminar; Jan 30, 2015; Columbus, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    NASA Green Propulsion Technologies Pushing Aviation to New Heights (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Center Director Free is providing the Keynote at the Disruptive Propulsion Conference, sponsored by Cranfield University, Cranfield, Bedfordshire, England in November. Director Free will be presenting a PowerPoint presentation titled, NASA Green Propulsion Technologies Pushing Aviation to New Heights at both the conference and a meeting at the Royal Aeronautical Society.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN18619 , Disruptive Green Propulsion Technologies-Beyond the Competitive Horizon; Nov 17, 2014 - Nov 18, 2014; London; United Kingdom
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Propulsion Technologies for Future Commercial Aircraft (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Aircraft Propulsion and Power
    Type: E-663270 , AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit; Jul 30, 2012 - Aug 01, 2012; Atlanta, GA; United States
    Format: application/pdf
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  • 7
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    Advanced Concepts for Aircraft LTO NOx Reduction: A NASA Perspective (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Aircraft Propulsion and Power
    Type: E-663266 , Aircraft Noise and Emissions Reduction Symposium (ANERS); Oct 25, 2011 - Oct 27, 2011; Marseille; France
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Propulsion Technologies for Future Aircraft Generations: Clean, Lean, Quiet, and Green (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Aircraft Propulsion and Power
    Type: E-663265 , ISABE Conference; Sep 12, 2011 - Sep 16, 2011; Gothenberg; Sweden
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    The early spectral evolution of Nova Cassiopeiae 1993 (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: In this paper we describe the evolution of Nova Cas 1993 over the first two months of its outburst. We present an ultraviolet light curve that covers the period from announcement to just after dust began forming in the ejecta (1994 Feb. 15) and International Ultraviolet Explorer (IUE) spacecraft constraints forced us to halt our observations. We have used spherical, expanding, Non-local Thermodynamic Equilibrium (NLTE) stellar atmospheres to compute synthetic spectra and have compared the results to combined ultraviolet (low-resolution 1200-3400 A and high-resolution 2400-3300 A) spectra. Our fits show that the effective temperature of the ejecta increased from approx. 8000 to about approx. 16 000 K between 1993 Dec. 12 and 1993 Dec. 26. The temperature then increased more slowly to approx. 24 000 on 1994 Jan. 28. A preliminary abundance analysis shows evidence for hydrogen depletion, as we also found for Nova V1974 Cygni; however we find a larger enhancement of carbon, nitrogen, and oxygen. We also show that the principal mechanism for mass ejection in this nova is a radiation pressure driven wind and that mechanical driving is not necessary.
    Keywords: ASTRONOMY
    Type: The Astronomical Journal (ISSN 0004-6256); 108; 3; p. 1008-1015
    Format: text
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  • 10
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    Next Generation Aircraft Electrical Power Systems and Hybrid/All Electric Aircraft (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Presentation to Aerospace Electrical Systems Expo, providing an overview of NASA's work on hybrid electric and all electric propulsion and projecting technology needs.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN23587 , Aerospace Electrical Systems Expo 2015; May 19, 2015 - May 21, 2015; Long Beach, CA; United States
    Format: application/pdf
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