Innovative Metal Fuels for Solid Rocket Propulsion

Two groups of innovative metal fuels are addressed in this paper. Three nanometric powders nominally ranging from 50 to 100 nm were contrasted to three micrometric activated aluminum powders, in terms of active metal content, specific surface area, scanning electron microscopy imaging, laser granulometry, and ignition properties in air. Both nanosized and activated aluminum powders featured augmented reactivity as well as a higher fraction of oxidized metal with respect to standard micrometric aluminum. All metal powders were also used as fuels for a series of composite AP (ammonium perchlorate)/Hydroxyl Terminated Polybutadiene (HTPB)/metal propellants, in either total or partial replacement of micrometric aluminum (baseline). Burning rates were contrasted to powder properties (mainly, specific surface area of the fuel), discussing the correlation between these parameters. A specific analysis on particle shape factor was also conducted on three micrometric powders. In this regard, a framework for the characterization of particle roundness was implemented and used for the cross comparison among several lots of powders for propulsion application (space-grade) as well as painting industry (industrial-grade), providing a statistical management of particle shape features.