Encyclopedia Astronautica
1966.10.25 - Propellant tanks of Apollo service module 017 failed


Propellant tanks of service module 017 failed during a pressure test at North American Aviation, Downey, Calif.

The planned test included several pressure cycles followed by a 48-hour test of the tanks at the maximum operating pressure of 165 newtons per square centimeter (240 pounds per square inch). Normal operating pressure was 120 newtons per square centimeter (175 pounds per square inch). After 1 hour 40 minutes at 165 newtons the failure occurred.

SM 017 (designed for SA-501) had been pulled for this test after cracks had been detected in the tanks of SM 101. SM 017 had been previously proof-tested a short time (a matter of minutes) at 220 newtons per square centimeter (320 pounds per square inch).

A team was set up at North American Aviation to look into the failure and its possible impact on the Saturn IB and Saturn V Apollo missions. MSC had two observers on the team, which was to make its findings and recommendations available by November 4.

North American Aviation identified the problem as stress-corrosion cracking resulting from use of methanol as a test liquid at pressures causing above threshold stresses. No tanks subjected to methanol at high stress levels would be used. Freon and isopropyl alcohol, respectively, were recommended for test fluids in the oxidizer and fuel systems, with the stipulation that the equipment had not previously seen propellant and would receive a hot gaseous nitrogen purge after completion of the cold flow operation.

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