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  • 1
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    Structureborne noise control in advanced turboprop aircraft (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Structureborne noise is discussed as a contributor to propeller aircraft interior noise levels that are nonresponsive to the application of a generous amount of cabin sidewall acoustic treatment. High structureborne noise levels may jeopardize passenger acceptance of the fuel-efficient high-speed propeller transport aircraft designed for cruise at Mach 0.65 to 0.85. These single-rotation tractor and counter-rotation tractor and pusher propulsion systems will consume 15 to 30 percent less fuel than advanced turbofan systems. Structureborne noise detection methodologies and the importance of development of a structureborne noise sensor are discussed. A structureborne noise generation mechanism is described in which the periodic components or propeller swirl produce periodic torques and forces on downstream wings and airfoils that are propagated to the cabin interior as noise. Three concepts for controlling structureborne noise are presented: (1) a stator row swirl remover, (2) selection of a proper combination of blade numbers in the rotor/stator system of a single-rotation propeller, and the rotor/rotor system of a counter-rotation propeller, and (3) a tuned mechanical absorber.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA-TM-88947 , E-3362 , NAS 1.15:88947 , AIAA PAPER 87-0530
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 2
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    In-flight near- and far-field acoustic data measured on the Propfan Test Assessment (PTA) testbed and with an adjacent aircraft (1993)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Flight tests to define the far-field tone source at cruise conditions were completed on the full-scale SR-7L advanced turboprop that was installed on the left wing of a Gulfstream 2 aircraft. This program, designated Propfan Test Assessment (PTA), involved aeroacoustic testing of the propeller over a range of test conditions. These measurements defined source levels for input into long-distance propagation models to predict en route noise. In-flight data were taken for seven test cases. Near-field acoustic data were taken on the Gulfstream fuselage and on a microphone boom that was mounted on the Gulfstream wing outboard of the propeller. Far-field acoustic data were taken by an acoustically instrumented Learjet that flew in formation with the Gulfstream. These flight tests were flown from El Paso, Texas, and from the NASA Lewis Research Center. A comprehensive listing of the aeroacoustic results from these flight tests which may be used for future analysis are presented.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA-TM-103719 , E-6402 , NAS 1.15:103719
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 3
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    Unbekannt
    Measured far-field flight noise of a counterrotation turboprop at cruise conditions (1989)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Modern high speed propeller (advanced turboprop) aircraft are expected to operate on 50 to 60 percent less fuel than the 1980 vintage turbofan fleet while at the same time matching the flight speed and performance of those aircraft. Counterrotation turboprop engines offer additional fuel savings by means of upstream propeller swirl recovery. This paper presents acoustic sideline results for a full-scale counterrotation turboprop engine at cruise conditions. The engine was installed on a Boeing 727 aircraft in place of the right-side turbofan engine. Acoustic data were taken from an instrumented Learjet chase plane. Sideline acoustic results are presented for 0.50 and 0.72 Mach cruise conditions. A scale model of the engine propeller was tested in a wind tunnel at 0.72 Mach cruise conditions. The model data were adjusted to flight acquisition conditions and were in general agreement with the flight results.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA-TM-101383 , E-4437 , NAS 1.15:101383
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unbekannt
    Structureborne noise control in advanced turboprop aircraft (1987)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Structureborne noise is discussed as a contributor to propeller aircraft interior noise levels that are nonresponsive to the application of a generous amount of cabin sidewall acoustic treatment. High structureborne noise levels may jeopardize passenger acceptance of the fuel-efficient high-speed propeller transport aircraft designed for cruise at Mach 0.65 to 0.85. These single-rotation tractor and counter-rotation tractor and pusher propulsion systems will consume 15 to 30 percent less fuel than advanced turbofan systems. Structureborne noise detection methodologies and the importance of development of a structureborne noise sensor are discussed. A structureborne noise generation mechanism is described in which the periodic components or propeller swirl produce periodic torques and forces on downstream wings and airfoils that are propagated to the cabin interior as noise. Three concepts for controlling structureborne noise are presented: (1) a stator row swirl remover, (2) selection of a proper combination of blade numbers in the rotor/stator system of a single-rotation propeller, and the rotor/rotor system of a counter-rotation propeller, and (3) a tuned mechanical absorber.
    Schlagwort(e): ACOUSTICS
    Materialart: AIAA PAPER 87-0530
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 5
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    Sputtering from a Porous Material by Penetrating Ions (2012)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Porous materials are ubiquitous in the universe and weathering of porous surfaces plays an important role in the evolution of planetary and interstellar materials. Sputtering of porous solids in particular can influence atmosphere formation, surface reflectivity, and the production of the ambient gas around materials in space, Several previous studies and models have shown a large reduction in the sputtering of a porous solid compared to the sputtering of the non-porous solid. Using molecular dynamics simulations we study the sputtering of a nanoporous solid with 55% of the solid density. We calculate the electronic sputtering induced by a fast, penetrating ion, using a thermal spike representation of the deposited energy. We find that sputtering for this porous solid is, surprisingly, the same as that for a full-density solid, even though the sticking coefficient is high.
    Schlagwort(e): Space Sciences (General)
    Materialart: GSFC.JA.7459.2012 , The Astrophysical Journal Letters; 743; 1; L5
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 6
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    Unbekannt
    Farfield inflight measurement of high-speed turboprop noise (1982)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A flight program was carried out to determine the variation of noise level with distance from a model high speed propeller. Noise measurements were obtained at different distances from a SR-3 propeller mounted on a JetStar aircraft, with the test instrumentation mounted on a Lear jet flown in formation. The propeller was operated at 0.8 flight Mach number, 1.12 helical tip Mach number and at 0.7 flight Mach number, 1.0 helical tip Mach number. The instantaneous pressure from individual blades was observed to rise faster at the 0.8 M flight speed, than at the 0.7 M flight speed. The measured levels appeared to decrease in good agreement with a 6 dB/doubling of distance decay, over the measurement range of approximately 16 m to 100 m distance. Further extrapolation, to the distances represented by a community, would suggest that the propagated levels during cruise would not cause a serious community annoyance.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA-TM-83327 , E-1574 , NAS 1.15:83327 , AIAA PAPER 83-9745 , AIAA 8th Aeroacoustics Conf.; Apr 11, 1983 - Apr 13, 1983; Atlanta
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 7
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    Understanding the Space Weathering of Mercury via Simulation of Micrometeorite Impacts (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Space weathering alters the surfaces of airless planetary bodies via irradiation from the solar wind and micrometeorite impacts. These processes modify the microstructure, chemical composition, and spectral properties of surface materials, typically resulting in the reddening (increasing reflectance with increasing wavelength), darkening (reducing albedo), and attenuation of characteristic absorption features in reflectance spectra. In lunar samples, these changes in optical properties are driven by the production of reduced nanophase Fe particles (npFe). Our understanding of space weathering has largely been based on data from the Moon and, more recently, near-Earth S-type asteroids. However, the environment at Mercury is significantly different, with the surface experiencing intense solar wind irradiation and higher velocity micrometeorite impacts. Additionally, the composition of Mercurys surface varies significantly from that of the Moon, including a component with very low albedo known as low reflectance material (LRM) which is enriched with up to 4 wt.% carbon over the local mean. Our understanding of how carbon phases, including graphite, are altered as a result of these processes is limited.
    Schlagwort(e): Space Sciences (General)
    Materialart: JSC-E-DAA-TN64971 , Lunar and Planetary Science Conference; Mar 18, 2019 - Mar 22, 2019; Woodlands, TX; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 8
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    Irradiation of FeS: Implications for the Lifecycle of Sulfur in the Interstellar Medium and Presolar FeS Grains (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Fe(Ni) sulfides are ubiquitous in chondritic meteorites and cometary samples where they are the dominant host of sulfur. Despite their abundance in these early solar system materials, their presence in interstellar and circumstellar environments is poorly understood. Fe-sulfides have been reported from astronomical observations of pre- and post-main sequence stars [1, 2] and occur as inclusions in bonafide circumstellar silicate grains [3, 4]. In cold, dense molecular cloud (MC) environments, sulfur is highly depleted from the gas phase [e.g. 5], yet observations of sulfur-bearing molecules in dense cores find a total abundance that is only a small fraction of the sulfur seen in diffuse regions [6], therefore the bulk of the depletion must reside in an abundant unobserved phase. In stark contrast, sulfur is essentially undepleted from the gas phase in the diffuse interstellar medium (ISM) [7-9], indicating that little sulfur is incorporated into solid grains in this environment. This is a rather puzzling observation unless Fe-sulfides are not produced in significant quantities in stellar outflows, or their lifetime in the ISM is very short due to rapid destruction. The main destruction mechanism is sputtering due to supernova shocks in the warm, diffuse ISM [10]. This process involves the reduction of Fe-sulfide with the production of Fe metal as a by-product and returning S to the gas phase. In order to test this hypothesis, we irradiated FeS and analyzed the resulting material using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).
    Schlagwort(e): Space Sciences (General)
    Materialart: JSC-CN-19996 , 41st Lunar and Planetary Science Conference; Mar 01, 2010 - Mar 05, 2010; The Woodlands, TX; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 9
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    Coordinated Analysis of an Experimentally Space Weathered Carbonaceous Chondrite (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The surfaces of airless bodies experience solar wind irradiation and micrometeorite impacts, a process collectively known as space weathering. These mechanisms alter the chemical composition, microstructure, and optical properties of surface materials and considerable work has been done to understand this phenomenon in lunar and ordinary chondritic materials. However, ongoing sample return missions Hayabusa2 to asteroid Ryugu and OSIRIS-REx to asteroid Bennu have prompted the need to study the effects of space weathering on hydrated, organic-rich materials, especially in the context of early results. Understanding space weathering of these samples is critical for properly interpreting remote sensing data during asteroid encounters, for sample site selection, and for the eventual study of returned samples. We can better understand space weathering of carbonaceous materials by simulating these processes in the laboratory. Recent experiments have shown that the changes in spectral characteristics of carbonaceous chondrites are not consistent among experiments, suggesting additional work is needed before these results can inform our understanding of spectral variations on asteroidal surfaces. Similarly, substantial work remains to characterize the chemical and microstructural effects of these processes in order to correlate these features with spectral changes. Here, we build on our previous work, presenting new results of the pulsed laser irradiation of the Murchison (CM2) meteorite to simulate micrometeorite impacts and the progressive space weathering of carbonaceous surfaces.
    Schlagwort(e): Space Sciences (General)
    Materialart: JSC-E-DAA-TN66089 , Lunar and Planetary Science Conference; Mar 18, 2019 - Mar 22, 2019; The Woodlands, Texas; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
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