Sl. Koontz et al., EOIM-III MASS-SPECTROMETRY AND POLYMER CHEMISTRY - STS-46, JULY-AUGUST 1992, Journal of spacecraft and rockets, 32(3), 1995, pp. 483-495
The Evaluation of Oxygen Interactions with Materials III space-flight
experiment was developed to obtain benchmark atomic-oxygen reactivity
data and wits conducted during Space Transportation System Mission 46.
We present an overview of the flight experiment and the results of th
e Lyndon B. Johnson Space Center polymer chemistry and mass-spectromet
er-carousel experiments. Mass-spectrometric measurements of gaseous pr
oducts formed by O-atom reaction with C-13-labeled Kaptan(TM) revealed
CO, CO2, H2O, NO, and NO2. By operating the mass spectrometer to dete
ct naturally occurring ionospheric species, we characterized the ambie
nt ionosphere at various times during the flight experiment and detect
ed the gaseous reaction products formed when ambient ions interacted w
ith the C-13 Kapton carousel sector, Direct comparison of the results
of on-orbit O-atom exposures with those conducted in ground-based labo
ratory systems, which provide known O-atom fluences and translational
energies, demonstrated the strong translational-energy dependence of O
-atom reactions with a variety of polymers. A line-of-centers reactive
scattering model was shown to provide a reasonably accurate descripti
on of the translational-energy dependence of polymer reactions with O
atoms at high atom kinetic energies, and a Beckede-Ceyer model provide
d an accurate description of O-atom reactivity over a three-order-of-m
agnitude range in translational energy and a four-order-of-magnitude r
ange in reaction efficiency. Postflight studies of the polymer samples
by x-ray photoelectron spectroscopy and infrared spectroscopy demonst
rate that O-atom attack is confined to the near-surface region of the
sample, that is, within 50 to 100 Angstrom of the surface.