Oxygen interactions with materials III - Mission and induced environments

The Evaluation of Oxygen Interactions with Materials III (EOIM-III) flight experiment was developed to obtain benchmark atomic-oxygen-material reactivity data. The experiment was conducted during Space Shuttle mission 46, July 31 to August 7, 1992. Quantitative interpretation of the materials reactivity measurements requires a complete and accurate definition of the space environment exposure, including the thermal history of the payload, the solar ultraviolet exposure, the atomic-oxygen fluence, and any spacecraft outgassing and contamination effects. The thermal history of the payload was measured using 11 thermocouple sensors placed behind selected samples and on the EOIM-III payload structure. The solar ultraviolet exposure history of the EOIM-III payload was determined by analysis of the as-flown orbit and vehicle attitude combined with daily average solar ultraviolet and vacuum ultraviolet fluxes. The atomic-oxygen fluence was assessed in three ways. First, the O-atom fluence was calculated using a program that incorporates the MSIS-86 atmospheric model, the as-flown Space Shuttle trajectory, and solar activity parameters. Second, it was estimated directly from Kapton film erosion. Third, ambient O-atom measurements were made using the quadrupole mass spectrometer on the EOIM-III payload. As of this writing, our best estimate of the O-atom fluence is (2.3 plus or minus 0.3)x10 super(20) atoms/cm super(2). Finally, results of postflight surface analysis of selected samples by x-ray photoelectron spectroscopy indicate low levels of molecular contamination on the payload surface.