Background
@Tristan's answer to How are the silicon PV cells constructed in the ISS's solar panels? Are they as flexible as they appear here? informs us that Kapton is part of the "blanket" holding individual silicon photovoltaic cells together in the ISS' large solar panels and is what gives them that orange or golden color.
Answers to
- Why is gold used in space technology to protect from heat radiation?
- What was mylar used for on the Apollo Command Module space craft? Why is it gold after returning from space?
- How many different kinds of insulation film are wrapped around the Apollo Lunar Module? (see comments as well, it seems that "H-film" = Kapton)
also address the color of metallized (usually aluminized) Kapton. While on Earth superinsulation for cryogenic insulation is often aluminized Mylar, the higher high-temperature resistance of Kapton wins in spacecraft applications.
From Wikipedia's Kapton:
Kapton is a polyimide film used in flexible printed circuits (flexible electronics) and space blankets, which are used on spacecraft, satellites, and various space instruments. Discovered by the DuPont Corporation in the 1960s, Kapton remains stable (in isolation) across a wide range of temperatures, from 4 to 673 K (−269 to +400 °C).
and
Kapton is a registered trademark of E. I. du Pont de Nemours and Company.
Erosion rate
I ran across the paper cited below today and saw the plots below. I'm not certain of their accuracy or applicability to the ISS' solar panels, so I'm curious if there is a more detailed analysis, or even some measurements from samples an ISS astronaut may have taken during an EVA.
Question: What fraction of the Kapton thickness on the ISS' solar panels was likely eroded throughout their lifetime? Are there any specific predictions or measurements?
From Samwel, S. W (2004) Low Earth Orbital Atomic Oxygen Erosion Effect on Spacecraft Materials Space Research Journal 7 (1) pp. 1-13.
...variation of the Atomic oxygen erosion depth of Kapton... assuming a circular orbit, at mid-thermospheric altitude (500 km) for mean level of solar activity...
above: Fig. 5: AO Erosion depth as a function of spacecraft mission length for mean solar activity in polyimide Kapton below: Fig. 4: AO Erosion depth as a function of spacecraft surface orientation for mean solar activity in polyimide Kapton (presumably for 1 year)
