Atomic Oxygen Fluence Research Articles

Translational energy dependence of the reaction of atomic oxygen with polyimide films

Atomic beam experiments are reported in which atomic oxygen, produced in a conventional microwave discharge beam source, struck Kapton samples at a translational energy of approximately 0.14 eV. After being exposed to an atomic oxygen fluence in excess of 2xl0 cm~, the Kapton samples showed no evidence of reaction, either to the naked eye or under microscopic examination. These experiments, and others performed in this laboratory and elsewhere, strongly support the notion that there is a true dynamic barrier (in incident translational energy) of between 0.2 and 1 eV for the etching of polyimide films by atomic oxygen.

A consideration of atomic oxygen interactions with the Space Station

A computer model is developed in order to calculate fluence for a generalized spacecraft in orbital flight based on mass spectrometer and incoherent scatter (MSIS) measurements of ambient density. The calculations are used to identify criteria for the selection of materials for the construction of an LEO Space Station. The model is generalized such that the surfaces for study can be oriented in any direction with respect to: a body coordinate system fixed to the spacecraft (E surfaces); and a solar inertial coordinate system. A parametric study was performed in order to evaluate the effects of altitude, inclination, and solar activity on atomic oxygen fluence. Values are obtained for samples of Mylar, Kevlar, Kapton, Tedlar, Teflon and sulfone, as well as for some ethylene polymers. The range of values for material reactivities is from 360 microns for ram-facing surfaces to 200 microns for solar power surfaces during each cycle of solar activity. The possibility of improving reactivity by employing certain chemical coatings is also discussed.