Basic Combustion Research for the Practical Application of Sustainable Rocket Propellant (SRP)

In recent years, efforts to achieve a sustainable society have been strengthened worldwide, and reducing the environmental impact of the aerospace industry is one of the challenges that must be addressed. Sustainable Aviation Fuel (SAF) is a chemically processed biomass jet fuel that is carbon neutral and contains no aromatic, nitrogen or sulfur compounds that cause soot, NOx and SOx emissions, making it a clean fuel. In addition, it is believed that current sustainable fuel production technologies can be used to control the number of carbon atoms and molecular structure (branched, linear or cyclic) in the composition during the production process and optimize the fuel for use as a rocket propellant. The objective of this study is to develop Sustainable Rocket Propellant (SRP) from biomass and to demonstrate the technology of optimized rocket engines using this propellant. SRP is a new biomass-based rocket propellant, like RP-1 composition, with superior storage, safety and operability compared to cryogenic temperatures propellants, as well as excellent density specific impulse due to its high density. In addition, SRP has the potential to become a higher density, higher thrust propellant due to its flexibility in fuel design. In this study, rapeseed oil was selected as the raw material for SRP because of its high oil extraction rate and ease of cultivation. As a result of studying the optimal fuel properties of SRP, it was decided that the fuel composition of SRP should consist mainly of isoalkanes, which have a high combustion rate, and polycyclic cycloparaffins, which have a high density. The prototype SRP exhibited favorable physical and combustion properties, with higher flame temperatures and a lower soot tendency compared to conventional aviation fuel JETA-1. Furthermore, the micro explosion characteristics of a mixture of fuel components that are likely to consist of SRP were investigated during droplet combustion. The results suggest that it is possible to intentionally induce micro explosions by adjusting the fuel composition of SRP, which may lead to higher combustion efficiency. Future work will determine the final composition of SRP, evaluate its combustion characteristics, and assess the performance of SRP-optimized rocket engine.