Kinetic and mechanistic analysis of Mn(II)AA doped hypergolic ignition in HTP/kerosene bipropellant systems

Abstract

Hypergolic ignition systems have traditionally relied on toxic propellants such as MMH/NTO, prompting a global shift toward greener alternatives. High-Test Peroxide (HTP), with its high oxygen content and clean decomposition products, has emerged as a promising oxidizer when paired with kerosene and suitable catalysts. However, a mechanistic understanding of HTP–fuel ignition, especially with metal-organic catalysts under varying conditions, remains underdeveloped. Here, a comprehensive experimental and kinetic study of hypergolic ignition using Mn (II) acetylacetonate-doped kerosene with HTP is presented across a wide parametric space (HTP: 85–98 %; catalyst: 0.5–10 wt%; O/F: 4.5–7.5; T: 20–50 °C). The results reveal that ignition delay times (IDTs) reduce by over 30 % with preheating and optimal catalyst loading, and deconvoluted phase-wise IDTs show that Mn(II)AA primarily accelerates HTP decomposition and chemical ignition. Derived apparent activation energies (E_a ≈ 10.0 kJ/mol) are consistently low, while the Arrhenius pre-exponential factor (A) increases significantly with catalyst and oxidizer concentration, indicating catalytic efficiency and diminishing returns beyond 5 wt%. Peak flame temperatures exceeding 1200 °C confirm robust energy release, with high-speed imaging further revealing a transition to rapid, spatially distributed ignition under optimal conditions. These findings offer quantitative mechanistic insights into catalyst-enhanced HTP ignition and establish a framework for optimizing green bipropellant systems for aerospace propulsion.