Combustion behavior of gel fuels for sounding rocket applications

Abstract

Gelled propellants have now become an attractive alternative to traditional liquid and solid fuels for space propulsion because they can take advantage of the best of both fuels—providing better safety, storage stability, and throttling. Among various gel formulations, inorganic gel fuels using kerosene and silica have drawn interest for their clean burning nature and structural integrity. In this work, the combustion of inorganic gel fuels prepared by suspending fumed silica in kerosene is studied. The study is concerned with the thermal and physical processes involved in single droplet burning under normal conditions. Experimental research was performed to monitor and examine distinct phases of combustion, such as initial heat-up, gellant shell development, and internal vapor pressure-induced exfoliation. Thermal diagnostics and high-speed imaging were used to describe the flame structure, burning rate, and droplet regression behavior. The impact of silica concentration on combustion performance was also assessed with particular focus on shell behavior and bubble formation. The findings show that inorganic gel fuels can have more controlled and stable combustion than organic gels, despite the creation of non-combustible silica residue. This steady burning rate makes these fuels a good choice for sounding rocket missions, where rapid response and stability of combustion is important. The research adds to the understanding of inorganic gel combustion and offers insights for their possible use in future aerospace propulsion systems. Keywords: Inorganic gel, sounding rocket, fumed silica, combustion, shell formation, exfoliation.