Environmental Exposure Conditions for Teflon® Fluorinated Ethylene Propylene on the Hubble Space Telescope

Abstract

The outer layer of Teflon® fluorinated ethylene propylene (FEP) multi-layer insulation (MLI) on the Hubble Space Telescope (HST) was observed to be significantly cracked at the time of the Second HST Servicing Mission (SM2), 6.8 years after HST was launched into low Earth orbit (LEO). Comparatively minor embrittlement and cracking were also observed in the FEP materials retrieved from solar-facing surfaces on the HST at the time of the First Servicing Mission (3.6 years exposure). After SM2, a failure review board was convened to address the problem of degradation of MLI on the HST. In order for this board to determine possible degradation mechanisms, it was necessary to consider all environmental constituents to which the FEP MLI surfaces were exposed. Based on measurements and various models, the environmental exposure conditions for the FEP surfaces on the HST were estimated, including: the number and temperature ranges of thermal cycles; equivalent sun hours; fluence and absorbed radiation dose of x-rays, trapped protons and electrons and plasma electrons and protons; and atomic oxygen (AO) fluence. This paper presents the environmental exposure conditions for FEP on the HST, briefly describing the possible roles of the environmental factors in the observed FEP embrittlement and providing references to the published works which describe in detail testing and analysis related to FEP degradation on the HST.

Erosion of FEP Teflon and PMMA by VUV Radiation and Hyperthermal O or Ar Atoms

“…Fluorinated ethylene-propylene copolymer (FEP) Teflon, commonly used as a thermal control material on spacecraft, degrades upon exposure to the LEO environment (5)(6)(7)(8)(9)(10)(11)(12). Many studies have used both space environments and ground-based test facilities in order to unravel the erosion mechanism of FEP Teflon.…”

Surface Modification of Fluoropolymers via Molecular Design

“…They exhibit a wide range of outstanding properties, including high-temperature stability, excellent chemical resistance, low water sorption, and low dielectric constant. [26,27] Fluoropolymers have been widely used in space applications, [28,29] protective coatings, [30] microelectronics packaging, [12,31] and biotechnology. [32,33] Other basic materials properties of the fluoropolymers are widely available in the literature.…”

Analyses of Hubble Space Telescope Aluminized-Teflon Insulation Retrieved After 19 Years of Space Exposure

“…Electron and proton fluence from solar wind particles trapped in Earth's magnetic field have been calculated from deployment until December 9, 1999 using NASA's proton and electron models, AP-8 and AE-8, respectively (Ref. 3). The data for SM4 were extrapolated from these prior data, and indicated the Bays 5 and 8 MLI received an electrons fluence of 5.6×10 13 particles/cm 2 for electrons 40 keV, and a proton fluence of 5.4×10 10 particles/cm 2 for protons 40 keV.…”