INVESTIGATION OF SOLID SCRAMJET ENGINES FUELLED BY LITHIUM HYDRIDE

This study aims to investigate the combustion performance of lithium hydride (LiH) grains in a supersonic airstream to assess its potential as a fuel for solid-fueled scramjet engines. LiH could be a challenging alternative to liquid fuels due to its exothermic reactivity with different oxidizers (i.e. it burns spontaneously on contact with air starting at 470 K); and its hydrogen content, which suggests its suitability for scenarios requiring higher density than liquid hydrogen (LH2). Thermochemical properties of LiH and its exothermic decomposition were determined by the NASA CEA code. Flame temperatures have been found to be 12% higher than HTPB, resulting in a Isp 150% higher. In fact, specific impulse and thrust density predictions at different flight Mach demonstrate compelling performance, with values of 1100 m/s at M=7. The stoichiometric equivalence ratio of LiH indicates a lower oxidizer requirement compared to HTPB, leading to a grain geometry with reduced power impact. This optimized grain geometry enhances aerodynamic design, reducing drag and enabling the scramjet to maintain higher speeds more efficiently. These findings suggest that LiH holds potential as a viable fuel option for solid-fueled scramjet engines, offering favorable combustion characteristics and performance metrics. Further research is warranted to validate these preliminary results and explore practical implementation possibilities.