Failure Mechanism of Attitude Control System Valve in Chlorine Pentafluoride Service
Final technical rept. Jul 1970-Mar 1971
MCDONNELL DOUGLAS ASTRONAUTICS CO-HB HUNTINGTON BEACH CA
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As part of a continuing Air Force effort to develop component technology for high-energy propulsion systems, an attitude control system ACS valve was developed elsewhere for use with high-energy storable liquid propellants. This valve performed successfully in most propellants tested however, it failed by developing excessive leakage when operated in chlorine pentafluoride. The design and operation of the ACS VALVE WERE ANALYZED FOR MODES OF POSSIBLE FAILURE. The modes studied included overstressing of the closures by closing loads adhesive wear of the closure surfacescorrosion of the closures by CPF, and hydrofluoric acidabrasive wear corrosive wear and impact-initiated chemomechanical reactions. Some new equations which relate valve wear to operating and material parameters were developed during the analysis. Tests of some materials were conducted to supply data for certain of the analyses, to test the equations used, and to evaluate some candidate materials. For all of the normal modes of possible failure investigated, it was demonstrated conclusively that the valve is adequately designed withstand any expected level of load or attack. MDAC has shown by analysis and test that impact-initiated chemomechanical reaction of absorbed water with CPF on the closure surfaces will result in failure of the type observed.
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