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  • ACOUSTICS  (2)
  • NUMERICAL ANALYSIS  (2)
  • 1975-1979  (4)
  • 1955-1959
  • 1945-1949
  • 1
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    The method of averages applied to the KS differential equations (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A new approach for the solution of artificial satellite trajectory problems is proposed. The basic idea is to apply an analytical solution method (the method of averages) to an appropriate formulation of the orbital mechanics equations of motion (the KS-element differential equations). The result is a set of transformed equations of motion that are more amenable to numerical solution.
    Keywords: NUMERICAL ANALYSIS
    Type: NASA-CR-151607 , ACM-TR-109
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Noise measurements for a twin-engine commercial jet aircraft during 3 deg approaches and level flyovers (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Noise measurements have been made with a twin-engine commercial jet aircraft making 3 deg approaches and level flyovers. The flight-test data showed that, in the standard 3 deg approach configuration with 40 deg flaps, effective perceived noise level (EPNL) had a value of 109.5 effective perceived noise decibels (EPNdB). This result was in agreement with unpublished data obtained with the same type of aircraft during noise certification tests; the 3 deg approaches made with 30 deg flaps and slightly reduced thrust reduced the EPNL value by 1 EPNdB. Extended center-line noise determined during the 3 deg approaches with 40 deg flaps showed that the maximum reference A-weighted sound pressure level (LA,max)ref varied from 100.0 A-weighted decibels 2.01 km (108 n. mi.) from the threshold to 87.4 db(A) at 6.12 km (3.30 n. mi.) from the threshold. These test values were about 3 db(A) higher than estimates used for comparison. The test data along the extended center line during approaches with 30 deg flaps were 1 db(A) lower than those for approaches with 40 deg flaps. Flight-test data correlating (LA,max)ref with thrust at altitudes of 122 m (400 ft) and 610 m (2000 ft) were in agreement with reference data used for comparison.
    Keywords: ACOUSTICS
    Type: NASA-TM-X-3387 , L-10780
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    The development of the Poincare-similar elements with true anomaly as the independent variable (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: In reference 1, the Hamiltonian of the unperturbed two-body problem in extended phase space is established. Depending on the type of time transformation, eight canonical elements were developed with the true anomaly or the eccentric anomaly as the independent variable. These two new sets, DS(phi) and DS(u), however contain singularities for small eccentricities and inclinations. In reference 2, these singularities are removed by a transformation from DS(u) to eight canonical PS(u) elements. In reference 3, the DS(phi) variables are transformed to the PS(phi) elements to remove the singularities. However, no direct relation was established between the eight canonical PS(phi) elements and the Cartesian coordinates. It is the purpose of this report to establish those relations and to develop the perturbed equations of motion in the PS(phi) space. This report also demonstrates the accuracy of this new set when it is applied to numerical orbit prediction problems.
    Keywords: NUMERICAL ANALYSIS
    Type: NASA-TM-79454 , JSC-11550 , JSC-IN-76-FM-60
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Statistical comparisons of aircraft flyover noise adjustment procedures for different weather conditions (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Aircraft flyover noise spectra and effective perceived noise level (EPNL) values obtained under widely different weather conditions were adjusted according to a proposed national standard. The results were statistically compared with the same measured spectra adjusted according to an alternate procedure and with reference spectra and EPNL values obtained under almost ideal weather conditions. Three different ways to represent the weather condition through which the sound propagated were also evaluated.
    Keywords: ACOUSTICS
    Type: NASA-TP-1430 , L-12626
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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