Dec 14 1981
From The Space Library
NASA issued a final report on investigation of the leak of nitrogen tetroxide oxidizer at KSC September 22. A four-person committee chaired by KSC's Wiley Williams said that the cause of the leak was failure of a quick-disconnect fitting in which iron nitrate from the oxidizer had accumulated between interior components, allowing escape to the outside.
Between 15 and 20 gallons of oxidizer escaped, some diverted away from the orbiter surface by a catch system, but "a significant quantity" flowed over the outside of the orbiter and its thermal-protection system. About 370 tiles had to be removed. Oxidizer also got into the forward module of the reaction control system, damaging thermal blankets and electrical wiring.
Close tolerance in the interior components, allowing the binding to take place, was a design failure point unrecognized before the accident. As the same fittings would be used for the second Shuttle launch, the committee recommended taking several steps before loading hypergolic propellant again: -adding more values to the system to permit isolation of the quick disconnect fittings -modifying the catch system and adding protective aprons to guard against a large leak -changing procedures to eliminate use of the quick-disconnect fitting as a shutoff valve -expanding emergency procedures and conditioning the servicing team to expect similar failures -sealing possible entry paths into the orbiter during loading, or purging internal compartments with inert gaseous nitrogen.
Although the committee limited its investigation to this one incident, it recommended review of its report to identify other fluids used around the orbiter that could cause damage if spilled. (NASA Release 8173)
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