The International Space Station (ISS) Port 1 (P1) External Active Thermal Control System (EATCS) Ammonia Leak



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49th International Conference on Environmental Systems


From 2013 to 2017, the crew onboard the International Space Station (ISS) was at risk of dire consequences due to an external ammonia leak. Ammonia is used in the External Active Thermal Control System (EATCS) to cool the pressurized modules and external electrical systems. Engineers at NASA’s Johnson Space Center (JSC) initially detected the leak in one of two cooling loops by monitoring the system ammonia inventory decay over time. White flakes seen on High Definition (HD) cameras were also thought to be associated with the leakage but not confirmed. Initially, the leak was small enough that the ammonia inventory and system operations were not in jeopardy. However, the leak began to accelerate to the point where troubleshooting and corrective action were vital to the sustainability of the ISS. Therefore, it became imperative that the leak be located and repaired for ISS operations to continue. No tools were readily available on the ISS to locate such a leak when it was initially detected, however NASA engineers were already in the process of developing a new device for this purpose called the Robotic External Leak Locator (RELL). The RELL is a robotic instrument package with a mass spectrometer and an ion pressure gauge. Initial checkout operations with RELL happened to coincide with the increasing leak, and a higher concentration of vaporous ammonia was found around the P1 EATCS Radiator #3 flexible jumper hoses. The leak ceased after the radiator and its flexible hoses were remotely isolated from the loop and the ammonia from the isolated segment was vented to space. Astronauts conducted a spacewalk that successfully removed the flexible hoses, which were returned to ground for further investigation. The purpose of this paper is to review the leak detection and isolation efforts, investigation results, lessons learned and the recovery plan.


Darnell Cowan, National Aeronautics and Space Administration (NASA), USA
Timothy Bond, National Aeronautics and Space Administration (NASA), USA
Jordan Metcalf, National Aeronautics and Space Administration (NASA), USA
ICES206: Manned Orbiting Infrastructures, Habitats, Space Station and Payload Thermal Control
The 49th International Conference on Environmental Systems as held in Boston, Massachusetts, USA on 07 July 2019 through 11 July 2019.


thermal, fluids, ISS, ATCS, leak, thermal control systems, NASA