New Approach for Service Life Evaluation of Gun Propellant

摘要

The ability to predict how long gun propellant will remain serviceable (i.e., safe and functional) has been a concern of the US Navy for decades. The initial ordnance service life program began in 1944. Historically, service life programs have provided very limited extensions for service life of gun propellant. One of the primary reasons for this short coming is that gun propellant contains nitrate esters (nitrocellulose, nitroglycerin, or both). Nitrate esters are by their very nature, unstable. During the course of storage, gun propellant slowly and spontaneously releases nitrogen oxides (a red color fume). Stabilizer is added to the propellant at the time of manufacturing to serve as a 'trap' for the oxides. Without the stabilizer, or when the stabilizer content is low, the liberated nitrogen oxides can catalyze the decomposition of the original nitrate esters. This reaction is exothermic and can eventually lead to autocatalysis (self-ignition) of the gun propellant. Most Naval gun propellants are subjected to periodic fume tests throughout their lifetime to hopefully assure that they remain in a stable condition safe for storage and handling. All objective studies of fuming process have indicated that the test is simply a pass / fail procedure with no quantifiable content. A review of an incident which occurred in 1976 at ARDEC, revealed that the red fume produced in the test could fade in a few days. At some time after the red fume fading, many types of propellant could self-ignite. Therefore, it was concluded that the time-to-fume test is clearly not an accurate and safe predictive test method. Today the routine use of more precise technology such as the HPLC (High Performance Liquid Chromatography) has greatly enhanced our understanding of the effective stabilizer contents remained in the propellant. While this HPLC data is useful for assessment of the current stability condition, it does not predict the future safe storage life of the propellant.