Formulation of Hexamine‐based Fuels for Hybrid Rockets

Abstract

AbstractHybrid rockets have many attractive properties but have not yet been used in any high performance applications, mainly due to the low regression rate of the solid fuels used. In this work, a number of crystalline organic fillers were assessed with the aim to increase the regression rate and density of HTPB‐based fuels. Hexamine, which was the most promising filler, catalyses the HTPB/isocyanate crosslinking reaction leading to unacceptable short pot life. However, it was found that the pot life could be substantially prolonged by the use of less reactive brands of HTPB, added plasticizer and reduced NCO/OH ratio. Fuel formulations containing 75 % hexamine were easy to cast and the cured slabs were of good quality, free from bubbles or voids, with a density 30 % higher than plain HTPB. The tensile strength of the fuels were similar to typical solid propellants but the elasticity might need to be improved. Hexamine decompose at substantially lower temperature than HTPB. This, and its high density, makes it promising for use in hybrid rocket fuels.