High-Energy Metal Fuels for Rocket Propulsion: Characterization and Performance

A joint international effort to improve solid propellant performance within the framework of a FP7 European Project was described. Several metallized solid rocket propellants, of the broad family AP/HTPB/Metal in the ratio 68/14/18, were experimentally analyzed seeking to optimize the delivered specific impulse by identifying the most suitable high-energy fuel. Keeping the same nominal composition, different metallic fuels (including micrometric and nanometric Al, AlH3, and a variety of dual metal compositions) were characterized, tested, and contrasted to a conventional micrometric aluminum (30 μm average grain size) certified for space flights. In order to overcome the intrinsic performance limitations of the matrix AP/HTPB, a new matrix consisting of ADN/GAP satisfying also the need for environmentally benign propellant formulation was considered as well. A comparative analysis between the two solid propellant systems in terms of ideal thermochemistry and experimental combustion properties reveals advantages and disadvantages of both. Overall, it is judged worthwhile to develop ADN/GAP propellants, with or without metallic fuels, to enhance the current status of solid rocket propulsion. Controlling morphology and mechanical properties of ADN/GAP compositions and understanding their flame structure and aggregation/agglomeration properties are the main issues still challenging industrial users.