Theoretical investigation of the thermal decomposition mechanism of ammonium dinitramide (ADN) as a green propellant using DFT methods.

The demand for satellite maneuvering and reaction control systems (RCS) is increasing, therefore, space agencies are searching for greener, high performance propellant alternatives. One alternative that fits this description is ammonium dinitramide (ADN), which is a promising eco-friendly option to replace the use of hydrazine based monopropellant because of its high density of energy and low toxicity. An investigation into the mechanism for ADN decomposition in the gas phase has been systematically undertaken using density functional theory (DFT). The geometry and frequencies of the possible decomposition products of ADN have been optimized and calculated at the B3LYP/6-311++G(d,p) level; a reaction pathway was developed based upon the investigation of five reaction routes that could lead to the decomposition products using energies of each molecule's transition state and the intrinsic reaction coordinate. Due to the limited thermal stability that ADN possesses at room temperature, the effect of solvents on the thermodynamics of ADN was modeled and studied in a liquid phase, specifically water and methanol, to gain insight into the thermodynamic and kinetic aspects of the ADN decomposition pathway and provide a greater understanding of the performance and stability of ADN to function as a green propellant in next-generation satellite propulsion systems.