CHARACTERIZATION OF REMAINING EFFECTIVE STABILIZER IN A REPRESENTATIVE PROPELLANT GEOMETRY

A stabilizer compound is included in chemical propellant formulations to reduce autocatalytic reactions and prolong the useful life. Higher storage temperatures and longer life spans increase the risk of stabilizer being depleted to an unsafe level which would require disposal of the propellant. Because stabilizer levels are frequently measured and recorded, this metric is often the driver for remaining useful life estimates of propellant. Propellant stabilizer consumption is driven by the evolution of NOx molecules volatilizing from the propellant itself and reacting with stabilizer in the gas phase to prevent the NOx molecule from reacting with a pristine nitrate ester in the propellant. As the stabilizer is consumed, additional stabilizer volatilizes to maintain equilibrium. Where in the propellant volume this stabilizer evolves from is driven by both the temperature of the propellant as well as the consumption of surrounding stabilizer. This work presents an analysis of one method to estimate where the stabilizer evolves from and how different sampling methods could yield different results on the remaining effective stabilizer in the solid phase. This will include developing a numerical model to simulate the temperature distribution in the propellant and incorporate a published equation for stabilizer depletion to translate this temperature profile to stabilizer consumption. The results will provide a basis for the selection and preparation of propellant for analysis. This is an advancement to the current state-of-the-art where stabilizer levels are sampled and assumed to represent the bulk stabilizer levels of the entire volume.