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  • Acoustics  (11)
  • Aerodynamics  (5)
  • ASTROPHYSICS  (2)
  • STRUCTURAL MECHANICS  (2)
  • 1
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    First detection of line emission from the hot interstellar medium with solid state detectors (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Previously reported enhanced soft X-ray emission from the North-Galactic Polar region supports the theory of a hot interstellar component. This paper reports the first detection of line emission from the hot interstellar component in the North-Galactic-Polar region. Measurements were made with solid state Si(Li) detectors aboard a spin-stabilized rocket launched from the White Sands Missile Range on March 22, 1980. Two features are clearly present in the low energy portion of the spectrum derived from the data. They correspond to emission lines from C V (300 eV) and C VI (360 eV), and from O VII (560 eV) and O VIII (650 eV). The detection of emission lines coming from these highly stripped ions is direct evidence for the thermal origin of the emission and confirms the presence of a hot (1-million K) component in the interstellar medium.
    Keywords: ASTROPHYSICS
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    NASA TECHNICAL REPORTS
  • 2
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    Design and Performance Calculations of a Propeller for Very High Altitude Flight (1998)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Reported here is a design study of a propeller for a vehicle capable of subsonic flight in Earth's stratosphere. All propellers presented were required to absorb 63.4 kW (85 hp) at 25.9 km (85,000 ft) while aircraft cruise velocity was maintained at Mach 0.40. To produce the final design, classic momentum and blade-element theories were combined with two and three-dimensional results from the Advanced Ducted Propfan Analysis Code (ADPAC), a numerical Navier-Stokes analysis code. The Eppler 387 airfoil was used for each of the constant section propeller designs compared. Experimental data from the Langley Low-Turbulence Pressure Tunnel was used in the strip theory design and analysis programs written. The experimental data was also used to validate ADPAC at a Reynolds numbers of 60,000 and a Mach number of 0.20. Experimental and calculated surface pressure coefficients are compared for a range of angles of attack. Since low Reynolds number transonic experimental data was unavailable, ADPAC was used to generate two-dimensional section performance predictions for Reynolds numbers of 60,000 and 100,000 and Mach numbers ranging from 0.45 to 0.75. Surface pressure coefficients are presented for selected angles of attack. in addition to the variation of lift and drag coefficients at each flow condition. A three-dimensional model of the final design was made which ADPAC used to calculated propeller performance. ADPAC performance predictions were compared with strip-theory calculations at design point. Propeller efficiency predicted by ADPAC was within 1.5% of that calculated by strip theory methods, although ADPAC predictions of thrust, power, and torque coefficients were approximately 5% lower than the strip theory results. Simplifying assumptions made in the strip theory account for the differences seen.
    Keywords: Aerodynamics
    Type: NASA/TM-1998-206637 , E-11102 , GRC-E-DAA-TN10120
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    NASA TECHNICAL REPORTS
  • 3
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    Design and fabrication of a radiative actively cooled honeycomb sandwich panel (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The mass of a radiative actively cooled panel was compared to the mass of a bare actively cooled panel designed to the same conditions and constraints. The approach was to design and optimize a 0.61 x 6.1 m full scale panel which combines radiative and active cooling to control structural temperatures to levels compatible with use of lightweight materials and to fabricate a 0.61 x 1.22 m panel for performance testing. Results of the design and optimization of the full scale radiative actively cooled structural panel, including radiative concept selection, final configuration details, test panel description, and conclusions are summarized.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Recent Advan. in Structures for Hypersonic Flight, Pt. 1; p 449-492
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    NASA TECHNICAL REPORTS
  • 4
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    Validation of the Predicted Circumferential and Radial Mode Sound Power Levels in the Inlet and Exhaust Ducts of a Fan Ingesting Distorted Inflow (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Fan inflow distortion tone noise has been studied computationally and experimentally. Data from two experiments in the NASA Glenn Advanced Noise Control Fan rig have been used to validate acoustic predictions. The inflow to the fan was distorted by cylindrical rods inserted radially into the inlet duct one rotor chord length upstream of the fan. The rods were arranged in both symmetric and asymmetric circumferential patterns. In-duct and farfield sound pressure level measurements were recorded. It was discovered that for positive circumferential modes, measured circumferential mode sound power levels in the exhaust duct were greater than those in the inlet duct and for negative circumferential modes, measured total circumferential mode sound power levels in the exhaust were less than those in the inlet. Predicted trends in overall sound power level were proven to be useful in identifying circumferentially asymmetric distortion patterns that reduce overall inlet distortion tone noise, as compared to symmetric arrangements of rods. Detailed comparisons between the measured and predicted radial mode sound power in the inlet and exhaust duct indicate limitations of the theory.
    Keywords: Acoustics
    Type: NASA/TM-2012-217253 , AIAA Paper-2011-2808 , E-18008 , 17th Aeroacoustics Conference; Jun 05, 2011 - Jun 08, 2011; Portland, OR; United States
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  • 5
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    Tone Noise Predictions for a Spacecraft Cabin Ventilation Fan Ingesting Distorted Inflow and the Challenges of Validation (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A fan tone noise prediction code has been developed at NASA Glenn Research Center that is capable of estimating duct mode sound power levels for a fan ingesting distorted inflow. This code was used to predict the circumferential and radial mode sound power levels in the inlet and exhaust duct of an axial spacecraft cabin ventilation fan. Noise predictions at fan design rotational speed were generated. Three fan inflow conditions were studied: an undistorted inflow, a circumferentially symmetric inflow distortion pattern (cylindrical rods inserted radially into the flowpath at 15deg, 135deg, and 255deg), and a circumferentially asymmetric inflow distortion pattern (rods located at 15deg, 52deg and 173deg). Noise predictions indicate that tones are produced for the distorted inflow cases that are not present when the fan operates with an undistorted inflow. Experimental data are needed to validate these acoustic predictions, as well as the aerodynamic performance predictions. Given the aerodynamic design of the spacecraft cabin ventilation fan, a mechanical and electrical conceptual design study was conducted. Design features of a fan suitable for obtaining detailed acoustic and aerodynamic measurements needed to validate predictions are discussed.
    Keywords: Acoustics
    Type: E-18071 , E-18071-1 , NOISE-CON 2011; Jul 25, 2011 - Jul 27, 2011; Portland, OR; United States
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    NASA TECHNICAL REPORTS
  • 6
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    Spectral observation of the soft X-ray background and of the North Polar Spur with solid state spectrometers (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Soft X-ray diffuse background observations in the 0.3-1.5 keV interval of two sky regions, near the north galactic pole and the North Polar Spur (NPS) are reported. Data were taken with a solid-state spectrometer carried by a rocket. The near-polar region exhibited O VII ion emissions at 530 eV. A second component was not identified but was attributed to the Galactic Halo. Fe XVIII, Ne IX, and O VIII contributions were detected in the NPS, along with an enhancement at 1.35 keV from Mg XI lines. A two-temperature contour was fit to the spectra and chi-square confidence levels of 90 and 68 percent were obtained.
    Keywords: ASTROPHYSICS
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  • 7
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    High heat flux actively cooled honeycomb sandwich structural panel for a hypersonic aircraft (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of a program to design and fabricate an unshielded actively cooled structural panel for a hypersonic aircraft are presented. The design is an all-aluminum honeycomb sandwich with embedded cooling passages soldered to the inside of the outer moldline skin. The overall finding is that an actively cooled structure appears feasible for application on a hypersonic aircraft, but the fabrication process is complex and some material and manufacturing technology developments are required. Results from the program are summarized and supporting details are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2959
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  • 8
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    Acoustic Measurements of an Uninstalled Spacecraft Cabin Ventilation Fan Prototype (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Sound pressure measurements were recorded for a prototype of a spacecraft cabin ventilation fan in a test in the NASA Glenn Acoustical Testing Laboratory. The axial fan is approximately 0.089 m (3.50 in.) in diameter and 0.223 m (9.00 in.) long and has nine rotor blades and eleven stator vanes. At design point of 12,000 rpm, the fan was predicted to produce a flow rate of 0.709 cu m/s (150 cfm) and a total pressure rise of 925 Pa (3.72 in. of water) at 12,000 rpm. While the fan was designed to be part of a ducted atmospheric revitalization system, no attempt was made to throttle the flow or simulate the installed configuration during this test. The fan was operated at six speeds from 6,000 to 13,500 rpm. A 13-microphone traversing array was used to collect sound pressure measurements along two horizontal planes parallel to the flow direction, two vertical planes upstream of the fan inlet and two vertical planes downstream of the fan exhaust. Measurements indicate that sound at blade passing frequency harmonics contribute significantly to the overall audible noise produced by the fan at free delivery conditions.
    Keywords: Acoustics
    Type: NASA/TM-2012-217692 , E-18375 , 12_158 , Inter-Noise 2012, The 41st International Congress and Exposition on Noise Control Engineering; Aug 19, 2012 - Aug 22, 2012; New York, NY; United States
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  • 9
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    Tone Noise Predictions for a Spacecraft Cabin Ventilation Fan Ingesting Distorted Inflow and the Challenges of Validation (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A fan tone noise prediction code has been developed at NASA Glenn Research Center that is capable of estimating duct mode sound power levels for a fan ingesting distorted inflow. This code was used to predict the circumferential and radial mode sound power levels in the inlet and exhaust duct of an axial spacecraft cabin ventilation fan. Noise predictions at fan design rotational speed were generated. Three fan inflow conditions were studied: an undistorted inflow, a circumferentially symmetric inflow distortion pattern (cylindrical rods inserted radially into the flowpath at 15deg, 135deg, and 255deg), and a circumferentially asymmetric inflow distortion pattern (rods located at 15deg, 52deg and 173deg). Noise predictions indicate that tones are produced for the distorted inflow cases that are not present when the fan operates with an undistorted inflow. Experimental data are needed to validate these acoustic predictions, as well as the aerodynamic performance predictions. Given the aerodynamic design of the spacecraft cabin ventilation fan, a mechanical and electrical conceptual design study was conducted. Design features of a fan suitable for obtaining detailed acoustic and aerodynamic measurements needed to validate predictions are discussed.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217681 , E-18071-2 , Noise-Con 2011; Jul 25, 2011 - Jul 27, 2011; Portland, OR; United States
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  • 10
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    Predicting the Inflow Distortion Tone Noise of the NASA Glenn Advanced Noise Control Fan with a Combined Quadrupole-Dipole Model (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A combined quadrupole-dipole model of fan inflow distortion tone noise has been extended to calculate tone sound power levels generated by obstructions arranged in circumferentially asymmetric locations upstream of a rotor. Trends in calculated sound power level agreed well with measurements from tests conducted in 2007 in the NASA Glenn Advanced Noise Control Fan. Calculated values of sound power levels radiated upstream were demonstrated to be sensitive to the accuracy of the modeled wakes from the cylindrical rods that were placed upstream of the fan to distort the inflow. Results indicate a continued need to obtain accurate aerodynamic predictions and measurements at the fan inlet plane as engineers work towards developing fan inflow distortion tone noise prediction tools.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217673 , E-18348 , AIAA Paper 2012-2196 , 18th Aeroacoustics Conference; Jun 04, 2012 - Jun 06, 2012; Colorado Springs, CO; United States
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