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Space shuttle molecular and wake vacuum measurementsThe wake environment of the space shuttle is analyzed to determine whether it is feasible to perform ultrahigh vacuum experiments in or near the payload bay with the shuttle oriented such that the payload bay faces the antivelocity direction. Several mechanisms were considered by which molecules could approach the payload bay from this direction and their relative contributions to the wake environment are estimated. These mechanisms include ambient atmospheric molecules that have velocities in excess of the orbital velocity which can overtake the shuttle, ambient atmospheric molecules that are backscattered by collisions with the shuttle induced atmosphere, and self scattering from the induced atmosphere. These estimates are compared with the measurements made with the collimated mass spectrometer which was part of the Induced Environment Contamination Monitor flown on several of the early shuttle flights. Although the collimated mass spectrometer was not designed for this purpose and the instrument background for the species for which the collimator is effective is above the expected levels, upper limits can be established for these species in the wake environment which are consistent with the analysis. There was considerably more helium and argon observed in the wake direction than was predicted, however. Possible origins of these gases are discussed.
Document ID
19850021666
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Naumann, R. J. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Carignan, G. R. (Michigan Univ. Ann Arbor, United States)
Miller, E. R. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
September 5, 2013
Publication Date
June 1, 1985
Subject Category
Astronautics (General)
Report/Patent Number
NASA-TM-86509
NAS 1.15:86509
Accession Number
85N29978
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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