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  • 1
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    Advanced Propfan Engine Technology (APET) definition study, single and counter-rotation gearbox/pitch change mechanism design (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Single-rotation propfan-powered regional transport aircraft were studied to identify key technology development issues and programs. The need for improved thrust specific fuel consumption to reduce fuel burned and aircraft direct operating cost is the dominant factor. Typical cycle trends for minimizing fuel consumption are reviewed, and two 10,000 shp class engine configurations for propfan propulsion systems for the 1990's are presented. Recommended engine configurations are both three-spool design with dual spool compressors and free power turbines. The benefits of these new propulsion system concepts were evaluated using an advanced airframe, and results are compared for single-rotation propfan and turbofan advanced technology propulsion systems. The single-rotation gearbox is compared to a similar design with current technology to establish the benefits of the advanced gearbox technology. The conceptual design of the advanced pitch change mechanism identified a high pressure hydraulic system that is superior to the other contenders and completely external to the gearboxes.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-168115 , NAS 1.26:168115 , EDR-11283
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Advanced propfan engine characteristics and technology needs (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A comparative study is presented for two of the advanced gas turbine engine designs developed in the course of a proprietary research effort for the NASA Advanced Propfan Engine Technology research program. In these engines, a cycle pressure ratio of 32.5:1 and a 2500 F maximum turbine temperature provide fuel efficient operation in the 32,000-ft altitude, Mach 0.72 cruise speed regime stipulated. Both of the engine configurations incorporate three spools, of which the compressors are dual-spool and the power turbines are free. A major design challenge for axial compressors in the 10,000-shp class was the maintenance of adequate blade heights in the later stages.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 83-1155
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Whistler mode wave propagation in the solar wind near the bow shock (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The presence of whistler mode waves in, and upstream from, the bow shock has been well established by observation. Theoretical descriptions of the mode under solar wind conditions have been relatively meagre, however, and it may not be generally appreciated how readily whistler waves generated in the shock could occupy most of the region ahead of the shock most of the time. Graphic descriptions of phase and group velocities and group velocity directions for typical solar wind parameters are presented by using the cold plasma approximation over all appropriate frequencies and directions with respect to the IMF. The relations of whistler phase and group velocities to observations of a quasi-perpendicular shock crossing by ISEE are illustrated.
    Keywords: SPACE RADIATION
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Plasma waves associated with energetic particles streaming into the solar wind from the earth's bow shock (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Plasma wave and plasma data from ISEE 1 and 2 are examined. In the upstream solar wind, three dominant types of plasma waves are observed which are associated with energetic particle streams coming from the bow shock: ion acoustic waves, electron plasma oscillations, and whistler mode waves. The ion acoustic waves occur simultaneously with either ion beams or a dispersed ion population in the energy range from 0.5 to greater than 45 keV. The electron plasma oscillations are long-wavelength, nearly monochromatic electrostatic waves which are closely correlated with the flux of low-energy electrons, especially in the 0.2-1.5 keV range. Electromagnetic waves with frequencies below 200 Hz are observed when either ion beams or dispersed ion distributions are present; for these waves the refractive index determined from the wave B to E ratio is consistent with whistler mode radiation.
    Keywords: SPACE RADIATION
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Far-ultraviolet studies. V - Rocket observation of the diffuse cosmic background (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A far-ultraviolet spectrometer and several far-ultraviolet photometers have been carried to an altitude of 347 km to measure the spectrum of three regions at high galactic latitudes. After correction for O I airglow and for stars in the field of view, a nearly uniform residual intensity of 285 plus or minus 32 photons per (sq cm s sr A) is found over the spectral range 1230-1680 A, along with some evidence for a sharp rise in intensity longward of 1680 A. It is argued that the signal is not likely to be due to light scattering from interstellar dust. The flat spectrum could represent the integrated light of distance galaxies. The sharp rise must be due to some other phenomenon.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 234
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    The spectrum of the diffuse cosmic ultraviolet background (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A far-ultraviolet spectrometer and several far-ultraviolet photometers were carried to an altitude of 347 km and used to measure the spectrum of three regions at high galactic latitudes. After correction for O I airglow and for stars in the field of view, a nearly uniform residual intensity of 285 + or - 32 photons (per sq cm s sr A) over the spectral range 1230-1680 A is found, along with some evidence for a sharp rise in intensity longward of 1680 A. It is believed that the signal is not likely to be due to light scattering from interstellar dust. The flat spectrum is perhaps the integrated light of distant galaxies. The sharp rise must be due to some other phenomenon.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 233
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    The significance of VLF transmitters in the precipitation of inner belt electrons (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The launch of the P78-1 low-altitude satellite containing a high-resolution electron spectrometer and the ISEE spacecraft with a plasma wave experiment have made it possible to perform simultaneous measurements of the waves, the plasma densities, and the precipitating electrons. It was found that nearly monochromatic waves in the range from 10 kHz to 25 kHz were frequently present in the near equatorial regions, their frequencies, narrow bandwidth, and geographic locations being consistent with various ground-based VLF transmitters as the sources. In the energy spectra of the precipitating electrons observed at low altitudes, narrow and at times multiple peaks often appear with central energies that decrease with increasing L shell. The narrow widths suggest that the interactions take place within a restricted range of latitudes which, based on other considerations, are likely equatorial.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 86; Dec. 1
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Advanced propfan drive system characteristics and technology needs (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Characteristics of a single-rotation drive system for an advanced turboprop engine are described. The gearbox is designed for a 10,000 shp three-spool, free-turbine engine and is installed in a wing-mounted nacelle. An offset gearbox from an earlier APET study provided the background for the preliminary design and benefit analysis for a 1990s advanced technology versus 1980s state-of-the-art gearbox. High efficiencies were achieved for both designs with inherently high life goals. Increases in design allowables for gears, bearings, and lubricants resulted in improvements for the 1990s design.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 84-1194
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Pollution Reduction Technology Program, Turboprop Engines, Phase 1 (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Exhaust pollutant emissions were measured from a 501-D22A turboprop engine combustor and three low emission combustor types -- reverse flow, prechamber, and staged fuel, operating over a fuel-air ratio range of .0096 to .020. The EPAP LTO cycle data were obtained for a total of nineteen configurations. Hydrocarbon emissions were reduced from 15.0 to .3 lb/1000 Hp-Hr/cycle, CO from 31.5 to 4.6 lb/1000 Hp-Hr/cycle with an increase in NOx of 17 percent, which is still 25% below the program goal. The smoke number was reduced from 59 to 17. Emissions given here are for the reverse flow Mod. IV combustor which is the best candidate for further development into eventual use with the 501-D22A turboprop engine. Even lower emissions were obtained with the advanced technology combustors.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-135040 , EDR-8708
    Format: application/pdf
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  • 10
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    Two-Dimensional Imaging of OH in a Lean Burning High Pressure Combustor (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Planar laser-induced fluorescence (PLIF) images of OH have been obtained from an optically accessible, lean burning high pressure combustor burning Jet-A fuel. These images were obtained using various laser excitation lines of the OH A (reverse arrow) X (1,0) band for several fuel injector configurations with pressures ranging from 1013 kPa (10 atm) to 1419 kPa (14 atm). Non-uniformities in the combusting flow, attributed to differences in fuel injector configuration, are revealed by these images. Contributions attributable to fluorescent aromatic hydrocarbons and complex fuel chemistries are also not evident.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-106854 , E-9444 , NAS 1.15:106854 , AIAA PAPER 95-0173 , Aerospace Sciences Meeting and Exhibit; Jan 09, 1995 - Jan 12, 1995; Reno, NV; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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