Burning behaviour of ADN solid propellants in comparison to other oxidizers

Solid rocket propellants based on ammonium dinitramide (ADN) as oxidizer and glycidyl azide polymer (GAP) as binder are suitable candidates for future propellants with good performance characteristics and no hazardous impact to the environment relating to the burning products. The comparison with the actual state of the art solid propellant, based on hydroxyl-terminated polybutadiene (HTPB) and ammonium perchlorate (AP), reveals that ADN-based propellants, especially in combination with an energetic binder, result in non-suitable burning rates (rb) and pressure sensitivities (n) for civil applications. Well known ballistic modifier to reveal an optimized burning behaviour with the main focus on rb and n are inefficient, incompatible to the oxidizer (ADN) or generate undesirable burning phenomena. For this reason, propellant formulations of ADN/GAP, ADN/HTPB and AP/GAP, AP/HTPB were produced and investigated to comprehend the differences in the combustion mechanism. The characterization of the burning behavior was done in a chimney-type window bomb (2 - 13 MPa). By the burning interruption of the propellants in liquid nitrogen, the reaction layer near the surface of the different sample formulations is analyzed in terms of Nano-Computed Tomography (nano-CT) and Confocal Raman Spectroscopy.