Paraffin-Based Solid Fuels for Hybrid Propulsion Filled with Lithium Aluminum Hydride: Thermal, Mechanical and Ballistic Characterization

A chemical, thermal, mechanical and ballistic investigation of paraffin-based solid fuels filled with Lithium Aluminum Hydride (LiAlH4, LAH) for hybrid propulsion is presented in this paper. Two different formulations containing 5% and 10% of a styrene-based thermoplastic elastomer (Polystyrene-block-poly(ethylene-ranbutylene)-block-polystyrene grafted with maleic anhydride, hereafter named SEBSMA) were investigated for the strengthening of paraffin waxes. Two LAH mass fractions were considered for each paraffin-based blend (5% and 10%), for a total of four fuel formulations. The paraffin-based blends filled with LiAlH4 were found to be stable when exposed to air. Rheological properties were investigated using a parallel plate giving evidence of the link between the elastic modulus (G’) evolution and the thermal behavior of LAH. Thermal properties were studied using a differential scanning calorimeter (DSC) leading to obtain data about the transitions typical of paraffin waxes (solid/solid and solid/liquid) and also about the thermal decomposition of the added energetic filler. A manufacturing technique for the production of homogeneous blends strengthened with SEBS-MA and filled with LAH is described. Firing tests were performed in a lab-scale hybrid motor using gaseous oxygen; the local and instantaneous regression rate was measured using a fiber optic technique. The behavior of paraffin waxes blended with the selected SEBS-MA thermoplastic elastomer and filled with LAH, is discussed.