A Space Experiment to Measure the Atomic Oxygen Erosion of Polymers and Demonstrate a Technique to Identify Sources of Silicone Contamination

Abstract

A low Earth orbital space experiment entitled, "Polymers Erosion And Contamination Experiment," (PEACE) has been designed as a GetAway Special (GAS Can) experiment to be accommodated as a Shuttle in-bay environmental exposure experiment. The first objective is to measure the atomic oxygen erosion yields of-40 different polymeric materials by mass loss and erosion measurements using atomic torce microscopy. The second objective is to evaluate the capability of identifying sources of silicone contamination through the use of a pin-hole contamination camera which utilizes environmental atomic oxygen to produce a contaminant source image on an optical substrate. 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION OF REPORT OF THIS PAGE

Study of surface chemical changes and erosion rates for CV-1144-O silicone under electron cyclotron resonance oxygen plasma exposure

“…1,2 In low earth orbit, atomic oxygen is generated by photodissociation of diatomic oxygen under ultraviolet ͑UV͒ radiation from the sun, and exists where the mean-free path of atomic oxygen is large enough that recombination has low probability. [2][3][4][5] The atomic oxygen density in LEO is not particularly high, depending strongly on solar activity and position; however, because of the high orbital velocity ͑approximately 8 km/s at Shuttle altitude͒, the flux is quite high, of the order of 10 15 atoms/cm 2 s. 6 The atomic oxygen in the LEO environment has caused deleterious erosion and oxidation problems for spacecraft materials. [3][4][5]7,8 Furthermore, contamination due to the eroded products that come from one region of a spacecraft and land in another region has become another significant problem.…”

“…[2][3][4][5] The atomic oxygen density in LEO is not particularly high, depending strongly on solar activity and position; however, because of the high orbital velocity ͑approximately 8 km/s at Shuttle altitude͒, the flux is quite high, of the order of 10 15 atoms/cm 2 s. 6 The atomic oxygen in the LEO environment has caused deleterious erosion and oxidation problems for spacecraft materials. [3][4][5]7,8 Furthermore, contamination due to the eroded products that come from one region of a spacecraft and land in another region has become another significant problem. For example, silicone exposed to AO on one part of the spacecraft can redeposit material on solar cell surfaces, degrading power generation.…”

“…10 The application and durability of different coating materials have been studied for years. [3][4][5]7,[11][12][13][14] Coatings of inorganic oxides such as aluminum oxide, silicon oxide, chromium oxide, as well as decaborane-containing polymers, have been shown to protect organic materials against oxygen plasma and/or AO erosion. 15 Lately, attention has been focused on the use of polymeric materials as protective coatings due to the ease and flexibility of their application.…”

“…It is found that silicone can chemically change into an ultraviolet resistant material upon AO and UV irradiation, which will serve as a barrier protecting underlying oxidizable materials. Upon reaction with atomic oxygen the silicone coatings (dϷ1 g/cm 3 ) lose their organic components and undergo a density increase to somewhere near that of amorphous SiO 2 (dϷ2.4 g/cm 3 have shown that silicones exposed to atomic oxygen and vacuum UV radiation release polymeric fragments which deposit on neighboring surfaces, resulting in shortening of their operating time. This background information leads to questions related to silicone contamination problems, including physical and chemical changes to the surfaces exposed to AO radiation, the speed and origin of the surface chemical changes, and the nature of the eroded product.…”

Oxygen plasma effects on optical properties of ZnSe films

“…24,25 In low earth orbit, AO is generated by photodissociation of diatomic oxygen under ultraviolet ͑UV͒ radiation from the sun and exists where the mean free path of oxygen atoms is large enough that recombination has low probability. [25][26][27][28] The AO density in LEO is not particularly high and depends strongly on solar activity and position. However, because of the high orbital velocity ͑approximately 8 km/s at Shuttle altitude͒, the flux is quite high, of the order of 10 15 atoms/cm 2 s. 29 The AO in LEO environment causes deleterious erosion, contamination, and oxidation problems for spacecraft materials.…”