Location and Repair of ISS Ammonia Leaks

The possibility of a leak in one of the International Space Station (ISS) External Active Thermal Control (EATC) loops is real and has been addressed in conceptual studies and in equipment preparation. Leak location and repair is essential to restore the functionality of the loop affected. However, it is a difficult task due to the large size of the ISS EATC loops and the harsh environment in which they operate. The rapid dispersion of leaking ammonia into the vacuum of space makes leak location particularly difficult. Repair must be performed via ExtraVehicular Activity (EVA) by doing what amounts to plumbing work on a high-pressure container in the thermal vacuum environment of space.

This paper provides insights into the preparation NASA and Boeing have taken to address the leak contingency. The design capabilities that allow leak location and repair for some scenarios are presented. The limitations of those techniques are also addressed and a set of scenarios that can't be addressed using the system capabilities are identified. For those cases where system capabilities can't locate or repair a leak a set of detection and repair equipment has been designed to address the location and repair of the system. The projects developing those new technologies are presented for both the challenging leak location and the equally challenging leak repair tasks. The operations leading to leak location and repair are also described.