scope:

Abstract:

Leaks in the Space Shuttle ammonia boiler system, as well as a single instance of a boiler shutdown during postflight operation, led to a review of the materials and processes used in the ammonia boiler. Failure analysis was performed and concluded that the corrosion was caused by high levels of chloride in the procured ammonia and that the shutdown was due to high levels of polyethylene oxide (PEO) in the propellant-grade ammonia. Since the switch to higher-purity, technical-grade ammonia, there have been no ammonia boiler leaks or shutdowns.