Cerium Oxide Based Active Catalyst for Green Hydroxylammonium Nitrate HAN Fueled Monopropellant Thruster

Abstract

Monopropellants are widely used for propulsion and gas generation applications. The current state of art monopropellant systems are based on hydrazine propellants. While hydrazine has a strong heritage as a versatile monopropellant, some of the inherent problems associated with hydrazine like toxicity, high vapor pressure and associated storage and handling cost have been a major concern. These concerns led to the exploration of nontoxic and better performing alternate propellants, among which Hydroxylammonium Nitrate (HAN) is a promising candidate and scores over other monopropellants in terms of insensitivity, toxicity and volatility. Some of the other projected advantages of HAN formulations over hydrazine include its lower crystallization point, higher density and volumetric impulse. The current practice of decomposing HAN is based on available technology used for hydrazine decomposition. However main challenges for HAN thrusters in contrast to hydrazine are material constraints imposed by the higher temperature levels experienced in HAN thrusters and need of high temperature tolerant catalysts. The catalysts under consideration should be both temperature tolerant and resistant to any possible poisoning from the decomposition products of HAN. There have been few reports of late on the development of suitable catalysts for HAN. Besides, unlike hydrazine, HAN propellants are multi-component, undergoes multistage decomposition adding complexity to the decomposition mechanism. Current work pertains to the development of a high temperature tolerant active catalyst for HAN decomposition. The issues related to catalyst design, catalyst characterization, reactivity to HAN based monopropellants, performance estimation and its decomposition kinetics are extensively pursued in this work. Special tests were developed to measure catalyst s capability to sustain extreme chemical and thermal conditions witnessed in HAN thruster. A novel cobalt doped cerium oxide (CeCo) catalyst was prepared via co-precipitation route...