A Comparison of Space- and Ground-Based Facility Environmental Effects for Fep Teflon

Abstract

Fluorinated Ethylene Propylene (PEP) Teflon™ is widely used as a thermal control material for spacecraft. However, it is susceptible to erosion, cracking, and subsequent mechanical failure in low Earth orbit (LEO). One of the difficulties in determining whether FEP Teflon will survive during a mission is the wide disparity of erosion rates observed for this material in space and in ground-based facilities. Each environment contains different levels of atomic oxygen, ions, and vacuum ultraviolet (VUV) radiation, in addition to parameters such as the energy of the arriving species and temperature. These variations make it difficult to determine what is causing the observed differences in erosion rates.

This paper attempts to narrow down which factors affect the erosion rate of FEP Teflon through attempting to change only one environmental constituent at a time. This was attempted through the use of a single simulation facility (plasma asher) environment with a variety of Faraday cages and VUV transparent windows.

Isolating one factor inside of a radio frequency (RF) plasma proved to be very difficult. Two observations could be made. First, it appears that the erosion yield of FEP Teflon with respect to that of polyimide Kapton is not greatly affected by the presence or lack of VUV radiation present in the RF plasma and the relative erosion yield for the FEP Teflon may decrease with increasing fluence. Second, shielding from charged particles appears to lower the relative erosion yield of the FEP to approximately that observed in space, however it is difficult to determine for sure whether ions, electrons, or some other components are causing the enhanced erosion.