Assessment of Atomic-Oxygen Flux in Low-Earth-Orbit Ground Simulation Facilities

Abstract

A common method for assessing the atomic-oxygen flux in low-Earth-orbit (LEO) ground simulation facilities is measuring the mass loss of attached Kapton coupon and assuming a known erosion yield of 3 x 10 - 2 4 cm 3 /O atom. However, in most ground simulation facilities additional components, for example, UV radiation, excited and ionized oxygen atoms and molecules or reactive volatile products of degraded samples might be involved in Kapton-atomic-oxygen interaction. The present work demonstrates the effect of simultaneous atomic oxygen and other reactive species irradiation on the Kapton etching rate. The Kapton mass loss was measured in situ using quartz crystal microbalance. The etching rate was assessed as a function of atomic oxygen and either VUV radiation, sample temperature, or reactive volatile products. Kapton reactivity was found to be dependent on the examined system parameters resulting in ambiguous determination of the atomic-oxygen flux. The validity of the use of Kapton as a reference material for ground simulation testing (of spacecraft candidate materials for LEO applications) should be critically reassessed in the context of the present findings.