Photochemical Spacecraft Self-Contamination: Laboratory Results and Systems Impacts
Abstract
It has become clear that photochemical reactions induced by solar vacuum ultraviolet (VUV) radiation play a substantial role in contaminant accretion and effects. A series of laboratory measurements of the absolute rates of adsorption, desorption, and VUV-induced deposition of contaminants have been made under simulated spacecraft conditions. The results of these experiments, together with analyses of operational and experimental flight data, show conclusively that the role of sunlight is not merely to darken or fix previously condensed contaminant films, but also to promote the irreversible deposition of contaminant films under conditions in which condensation would not occur. A simple model of the kinetics of photochemical deposition, based on a competition between desorption and photolysis of a transiently adsorbed contaminant molecule, using experimentally measured parameters, is reasonably successful in describing the deposition process. These laboratory experiments and analyses of space-flight experience reveal that photochemical deposition is significant mechanism whereby contaminant films accrete on orbit and must be considered in the design of future vehicles.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 25, 1990
- Accession Number
- ADA226488
Entities
People
- D. C. Marvin
- D. F. Hall
- G. S. Arnold
- T. B. Stewart
- W. C. Hwang
Organizations
- The Aerospace Corporation