Lab-Scale Investigation of Metal Hydrides as Additives in Liquefying Fuels for Hybrid Rocket Propulsion

This study analyzes the effects of metal hydrides on the combustion behavior of paraffin-based solid fuel formulations. Investigated hydrides include: AlH3, MgH2, LiAlH4, and Li3AlH6 . The discussion is divided into two different parts: (i) a wide theoretical investigation of specific impulse performances with different oxidizers (O2, N2O, and 98% H2O2) and (ii) a lab-scale experimental campaign aimed at the determination of the regression rate in O2 of selected formulations. In the work, performance of the hydride-loaded tested formulations are compared to that of reference nonloaded formulations. A relative grading of the analyzed performance is achieved. Under the investigated conditions, AlH3 is the hydride promoting the highest vacuum-specific impulse enhancement, with +3% when N2O is considered as oxidizer. Outputs from the ballistic analysis performed in gaseous O2 show the attractive regression rate performance of LiAlH4 (+70% increase over the non-loaded pure paraffin baseline).