Combustion of propellants with ammonium dinitramide

This paper reports a series of experiments involving ammonium dinitramide (ADN), a new energetic oxidizer of potential use in composite solid propellants. The experiments include (a) self-deflagration of pressed pellets of ADN; (b) combustion of sandwiches with ADN laminae on both sides of a binder lamina that is either pure or filled with particulate oxidizer and other additives; and, (c) combustion of propellants with a bimodal oxidizer size distribution, wherein, combustion of coarse ADN and fine AP (ammonium perchlorate) and vice versa were used, in addition to mixtures of coarse ADN and AP, fine ADN and AP, and all-ADN or all-AP formulations. The results indicate the possibility of a major role for condensed phase heat release in the control of the self-deflagration of ADN, resulting in very high rates compared to that of AP self-deflagration. The sandwich burning rates are always appreciably above the ADN self-deflagration rate, but follow the same trend as pressure is varied. This indicates a role for the oxidizer/fuel (O/F) flame present in the sandwiches, which seems to assist the self-deflagration of the ADN laminae. Results with oxidizer filled-sandwiches show that O/F flame-assisted self-deflagration of ADN lamina always controls the sandwich burning rate regardless of the contents of the binder lamina (ADN or AP particles, with or without very fine ferric oxide catalyst or aluminum). The all-AP formulations exhibited plateau burning and addition of Fe2O3 yielded burning rates as high as pure ADN laminae. A family of bimodal propellants reflect the sandwich results by showing higher rates for formulations with coarse ADN and any fine oxidizer (ADN or AP) than those with coarse AP and fine ADN or AP. Pressure sensitivity of the burning rates was high!.