scope:

As part of the International Space Station (ISS) Heat Rejection System (HRS) radiator face sheet failure investigation team, review of the radiator panel design indicated that the radiator panel acted as an enclosed, un-vented volume. Subsequent testing confirmed this assumption and other investigation data suggested the volume beneath the face sheet was fed, over time, by an internal leak of either nitrogen or ammonia. Pressure build-up continued and the separation of the face sheet from the underlying honeycomb structure grew due to the formation of football-shaped volumes, or "lagoons", in the honeycomb structure. After, either, reaching a critical pressure level or triggered by a micrometeoroid/orbital debris (MMOD)-induced pressure wave, the face sheet failed.