Adiabatic calorimetry for evaluation of thermally induced reactions in liquid propellants

Abstract

The gun propellants that are aqueous mixtures of the nitrate salts of hydroxylamine (HAN) and triethanolamine (TEAN) are homogeneous, ionic liquids and are susceptible to damage by a variety of contaminants. Reaction initiation that results from the absorption of thermal energy is a method for determination of propellant stability. An adiabatic calorimetry based, diagnostic system utilizes a commercially available accelerating rate calorimeter (ARC) that has been modified to make it suitable for use with liquid gun propellants. The effects of contaminants and impurities on reaction onset temperature which is related to safe storage temperature are readily determined using the ARC. In addition to propellant safety studies, the ARC data also provide insight into propellant efficacy, since ignition and combustion are observed. Reaction onset temperatures, as determined with the ARC, are independent of the quantity of material being stored, thereby eliminating the extrapolation from small laboratory samples that is a common uncertainty in many stability evaluation test methods. The presence of nitric acid, a common propellant contaminant, affects both storage stability and propellant efficacy in the gun. The data indicate that storage stability is adversely affected to a much greater extent than efficacy.