Experimental Investigation of Green Hypergolic Propellants for Upper-Stage Propulsion

Abstract

To address concerns regarding toxicity inherent in conventional storable brpropellants, the propulsion community is actively exploring "green" alternatives. Hydrogen peroxide (HTP), paired with eco-fnendly fuels such as kerosene or ethyl alcohol, is emerging as a promising option due to its potential for cost reduction in space launch, enhanced safety, ease of handling, and favorable density-impulse characteristics. This study investigates the hypergohcity and combustion dynamics of HTP with kerosene doped with organic manganese-based additives, targeting application in a 100 N class upper-stage thruster. The experimental campaign employs 95% and 98% HTP combined with variable catalyst loadings in kerosene to optimize ignition behavior and combustion performance. Drop tests were performed under controlled conditions to characterize ignition delay times (IDT) and post-ignition flame temperatures, supported by high-speed imaging and infrared diagnostics. Two O/F ratios (6.5 and 7.5) were explored to balance stoichiometric efficiency and ignition responsiveness. Comparative evaluation of Mn(II)AA and Mn(III)AA catalysts was conducted across a unified experimental matrix, with Mn(III)AA consistently outperforming Mn(II)AA by enabling faster ignition and higher combustion efficiency. Furthermore, the demonstration of catalytic hypergohcity eliminates the need for a conventional HTP decomposition catalyst bed, simplifying propulsion system architecture and reducing engine mass and cost. These findings provide critical data for the development of next-generation green propulsion systems, contributing to lighter, simpler, and safer thrusters for space applications. This research is an integral part of the EU Horizon Mane Sklodowska-Cune Actions (MSCA) funded initiative GREENLAM project, which aligns with the overarching goals of the EU Horizon initiative, facilitating technological innovation and advancements in the aerospace industry for the benefit of space exploration and satellite deployment.