Characterization of a family of paraffin-based solid fuels

framework of EU-project ORPHEE, some innovative solid fuel formulations for hybrid rocket propulsion were manufactured and tested in order to overcome the shortcoming of very low fuel regression rates, typical of conventional hybrid ro cket fuels. Firing tests were perfomed in a 2D slab burner implemented at SPLab (Space Propulsion Laboratory of Politecnico di Milano). Nano-Al powders and a metal hydride (Magnesium hydride (MgH 2)) were used as fillers in paraffin matrices. The highest regression rates were found f or the Solid Wax (SW) composition, added with 5% MgH 2 mass fraction. At 350 kg/m 2 s oxygen mass flux, the measured regression rate, a veraged in space and time, was 2.5 mm/s, which is approximately five times higher than that of the pure HTPB composition, taken as baseline reference fuel. Comp ositions added with nano-sized Aluminum powders were compared with those added with MgH 2, using gel or solid wax. A rheological investigation and a mechanical characterization wer e performed, in order to explain the dependence of the regression rate on the nature and size of the m etal powder, the viscosity of the paraffin melted layer, the thermodynamic properties of the differen t paraffins considered in this work. Nomenclature