Executive Summary : | Necessity of improved mission performance and environmental concerns are leading a way to change the criteria for propellant selection and rocket design. Traditionally, propellant performance in terms of specific impulse and density played a major role in its operability nut now cost, toxicity and environmental pollution are major criteria. Thus to reduce air pollution during rocket launches, research is being done to develop propellants that are environmentally amicable (“green”) and non-toxic. The simplicity of monopropellant feed and control systems make them very attractive for missions. Hydrazine (N2H4) is the most widely used monopropellant and is applied in many types of attitude control thrusters, insertion stages, and gas generators; however toxicity & flammability hazards are its major drawbacks. These drawbacks can be compensated by using the amicable hydrogen peroxide (H2O2) for providing safe, simple monopropellant systems. Though, catalyst system based on silver and platinum have been developed, but the problems of large pressure drops, high weight, and deactivation due to the stabilizers are a major concern. Thus, the need of the hour is to develop a new catalyst and thruster system for the combustion of H2O2 based green propellant which is cost effective and has longevity. The catalyst choice is one of the most important problems in the development of engines based on hydrogen peroxide. The catalyst operation life is influenced by numerous factors: • Catalyst material, • Pressure in the decomposition chamber, • Hydrogen peroxide concentration, • Load of its flow on the catalyst, and • Operation mode The main requirements that a catalyst should meet for the complete decomposition of concentrated hydrogen peroxide solutions are: 1. High activity: The time of contact of catalyst with hydrogen peroxide to start decomposition should be as short as possible and the reaction rate should be maximum. 2. Mechanical impact and thermal shock resistance: The resistance to mechanical impact and thermal shock associated with the engine start/stop (ignition/stop of operation) is particularly important. 3. High activity and stability in a wide interval of the operation conditions. 4. Resistance to stabilizing agents added to hydrogen peroxide to enhance its long-term stability. 5. Optimum ratio between the mechanical strength and specific surface area. |