Long-Term Storability of Propellant Tankage and Components

A program was initiated to investigate the storability of liquid system components and tankage under extreme conditions of relative humidity and temperature. A variety of system components and tankage materials are being evaluated for long-term storability with storable liquid rocket fuels and oxidizers. Storage conditions are 85 degrees F temperature and 85 relative humidity for oxidizer systems and 70 to 150 degrees F temperature for fuel systems. The propellants under test are N204, ClF5, and MHF-5. Tankage materials under test are various alloys of aluminum, steel and titanium. The results of almost 3 years of testing on a representative number of tankage materials have indicated that leakage of propellant can occur as a result of improper weld joint design, inadequate quality control in fabrication and inadequate acceptance leakage testing. Factors which can contribute to the development of oxidizer leakage are a high ambient relative humidity greater than 30 and stress corrosion cracking susceptibility of the tank material in combination with the propellant and trace quantities of foreign compoundselements in the propellant.