Technical Approach

Metal-bound porphyrins and metal-bound porphyrazins represent a class of molecules theoretically well-suited for use as a propellant ingredient. The metal ions remain locked inside a macrocyclic skeleton via strong metal-to-nitrogen atom ionic bonds, limiting their ability to interact with other chemicals in the polymeric matrix. These metals would remain dormant until needed during combustion, where they could cause areas of super-rate burning and platonization of the burn rate. In this project, researchers will screen the most commercially available and affordable metal-bound porphyrins and metal-bound porphyrazins for preliminary safety data and compatibility with each ingredient present in the proposed lead-free formulation before manufacturing the propellant at the 600-gram batch size. Propellant viscosity will be measured and strands will be fired from 50 psig to 4500 psig in an effort to elucidate their ballistic profiles. The presence of super-rate burning and platonization will be of particular interest for ultimate comparison to a lead- and RDX-free baseline XLDB and ATK's state-of-the-art, RDX-free, lead-containing formulation. The most promising formulation will be taken forward for scale-up and further characterization. The propellant will then be manufactured at the 1-gal mix size (10 lb) where five 2x4 subscale motors will be cast. Extended mechanical properties at hot and cold test conditions will be obtained. The 2x4 motors will be fired at various pressures across the ballistic profile to confirm and enhance the pressure-burn rate model.