N2-induced erosion of FEP in very low Earth orbit

The erosion yields of fluorinated ethylene propylene (FEP) by atomic oxygen (AO) and that by N2 in VLEO were quantitatively evaluated separately by ground-based experiments. A series of experiments were performed by a laser detonation beam source with a gas mixing system at Kobe University. O2 and Ar gases were used as source gases. Ar was used to simulate the physical effect of N2 collision energy in VLEO. Three beam conditions (50%Ar + 50%AO, 70%Ar + 30%AO, and 90%Ar + 10%AO) were used in the experiments. Since the erosion of FEP under simultaneous exposure conditions of AO and Ar beams is known to be additive, erosion yields of FEP by AO (Ey(AO)) and argon (Ey(Ar)) were evaluated by solving simultaneous equations for the mass loss of FEP under two different conditions. The analytical results showed that Ey(Ar) was more than six times larger than Ey(AO). These experimental data indicate that the erosion of the FEP in VLEO is mainly due to N2 bombardment, with AO being a minor effect, and are in qualitative agreement with the results of the SLATS on-orbit experiment.