Hybrid rocket fuel systems continue to be considered promising compared to other options (solid and liquid) due to reliability and safety in handling operations. Herein, paraffin fuel combustions with chemical additives such as elemental boron has been examined showing enhancement in the ignitions and combustions for paraffin (PW) fuels using sodium borohydride (NaBH4) and total energy. Measurements of ignition delays by applying hydrogen peroxide (H2O2) as liquid oxidizer using high–speed imaging on the most recommended compositions PSB2 were tested. Hypergolicity was improved by increasing the percentage of (NaBH4) (6%, exothermic reaction) between NaBH4 and H2O2 which convert B(s) to B(g) thus enhancing the spontaneous reaction. High heat of formation (ΔHc) of boron combustion products increases more than 2 times when pure paraffin wax was tested, as the mass percentage of B increases. Different propellant compositions with different percentage of boron ranging from (30:38) and (NaBH4) ranging from (4:12) %. were also calculated theoretically using CEA NASA code. An experimental testing for heat of combustion for the more candidate compositions PSB2 have been tested using a bomb calorimeter model Parr1621. The experimental result 12.7 J kg-1 is higher than theoretical values 8.92 J kg-1 according to the high pressurize oxygen environment on bomb calorimeter. H NMR test have been performed to determine the change occurred in PW during mixing and casting and the result showed that there is no change occurred and this is a good feature for additives compatibility with PW matrix. The recommended composition PSB2 for experimental testing or bulk production is selected on safety and processing grounds. Decreasing the ignition time (IDT) reveals the utility of the application of this propellant fuel mixture for “green" and high energetic propulsion systems.

Keywords: Sodium borohydride; boron; Hydrogen peroxide; Heat of combustion; ignition time delay; propellant; energetic propulsion systems; Paraffin fuel