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  • Other Sources  (2)
  • 1980-1984  (2)
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  • 1
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    Preparation and cleanliness verifications of a space simulation chamber for contamination sensitive test specimens (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Contamination sensitive optical devices were to be evaluated under thermal vacuum conditions. Test specifications called for an extremely clean chamber environment, ambient temperature chamber walls, and optical surface temperatures at approximately - 30 C. Chamber preparation included the replacement of diffusion pumps with cryopumps and the cleaning of the chamber walls to reduce contamination levels. Chamber cleaning using vacuum bake was tried and abandoned as time consuming and ineffective. Chemical cleaning and cleanliness verification methods were developed. Gas chromatograph analysis techniques were used extensively throughout the cleaning process to verify cleanliness levels prior to evacuating the chamber. A chamber cleanliness verification test using a thermoelectric quartz crystal microbalance and witness samples was performed to demonstrate that an appropriate cleanliness level was achieved.
    Keywords: GROUND SUPPORT SYSTEMS AND FACILITIES (SPACE)
    Type: NASA. Goddard Space Flight Center 13th Space Simulation Conf.; p 343-352
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    On eigensolutions for discontinuous liners in a duct containing uniform mean flow (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Sound attenuation in a rectangular acoustically lined duct containing uniform mean flow is analytically investigated using the generalized Wiener-Hopf technique. Uniqueness of the solution is enforced for lined sections of the finite axial extent by imposing edge conditions at the liner interface. Possible edge conditions are considered, including the Kutta condition, and the causal solution corresponding to edge conditions is considered the best choice. Solution methods such as the mode matching and singularity methods imply differing edge conditions, and results show that power attenuation is insensitive to the imposed edge conditions, although significant differences are observed for the reflection coefficient. The amplitude of the exponentially increasing instability mode in the lined section must be set to zero as a first approximation to the nonlinear situation, and results indicate that measurements of the reflection factor can be used to make a more definite decision about physically appropriate edge conditions.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 81-2017 , Aeroacoustics Conference; Oct 05, 1981 - Oct 07, 1981; Palo Alto, CA
    Format: text
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    NASA TECHNICAL REPORTS
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