Integrating Moisture Isotherms, Compatibility Assessment, and Model Propellant with ADN as an Eco-Friendly Oxidizer

This study delves into the use of ammonium dinitramide (ADN) as an eco-friendly substitute for ammonium perchlorate (AP) in solid rocket propellants. ADN based novel propellants were formulated with a nitrile butadiene rubber (NBR) based binder system. Employing Dynamic Vapor Sorption (DVS), ADN’s moisture characteristics were investigated at various temperatures (25, 35, 45 and 55°C) and utilized for propellant processing. Two component chemical compatibility assessments, in adherence to STANAG 4147 standard, were performed using Differential Scanning Calorimetry (DSC) and Vacuum Stability Testing (VST). Subsequently, propellant compositions containing ADN were formulated, and their performance was predicted using NASA’s CEC-71 code. The most promising formulation was processed and thereafter underwent testing for physical, ballistic, and mechanical performance against conventional AP-based propellants at a 500 g batch level. Optimal storage (≤ 25 °C, relative humidity (RH) ≤50%) and processing (35-40 °C, RH ≤35%) performance conditions were identified for ADN, contributing to the successful formulation of high-performance ADN/NBR propellant. The developed propellant showed marginal differences compared to AP/NBR in burn rate and density. However, compatibility issues with the bonding agent, hydantoin resin, led to deficiencies in mechanical strength. These findings contribute to the advancement of eco-friendly propellant technology, showcasing ADN’s potential as a transformative substance in aerospace applications.