Propulsive performance of a c3h4/h2o2 rocket prototype for future green bipropellant thrusters

In current liquid rocket engines, in both monopropellant or bipropellant configurations, the feeding system provides the propellants at a pressure that allows them to be injected into the thrust chamber by means of turbo pumps or pressurized systems such as direct gas pressurization, flexible bags within tanks or piston pressurization1,2.Even if the engine can be operated in pulse mode, the feed system is currently designed in order to guarantee the nominal steady state operation and, consequently, the nominal feed pressure should be higher than the expected one inside the combustion chamber due to pressure losses inside pipelines, valves and injectors. Except for the propellant itself, most of the weight of the propulsive system consists in the pressurizing system3.PulCheR (Pulsed Chemical Rocket with Green High Performance Propellants) 4,5 is a R&D project funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n°313271. The main aim of the project is to demonstrate the feasibility of a new propulsion concept in which the propellants are fed in the combustion chamber at low pressure and the thrust is generated by means of high frequency pulses, reproducing the defence mechanism of a notable insect: the bombardier beetle6,7. The radical innovation introduced by this concept is thee limination of any external pressurizing system even if the thruster works at high pressure inside the combustion chamber. At each pulse, pressurization of the combustion chamber gases takes place due to the decomposition or combustion reaction, and the final pressure is much higher than the one at which the propellants are stored. The pulsed chemical rocket concept is potentially able to substitute many currently used propulsion systems for accessing space. The feasibility of this new propulsion concept will be investigated at breadboard level in both mono and bipropellant configurations through the design, realization and testing of a platform of the overall propulsion system including allits main components. In addition, the concept will be investigated using green propellants with potential similar performance to the current state-of-the-art for monopropellant and bipropellantthrusters.8,9 The final test campaign will experimentally investigate the propulsive performance of the system in terms of specific impulse, minimum impulse bit and thrust modulation. The present paper aims at presenting the experimental results attained on the rocket prototype specifically designed for exploring the stationary (not-pulsed) propulsive performance of the bipropellant thruster with particular reference to: thrust, combustion chamber temperature, specific impulse, efficiency, propellants mixing and combustion. The test campaign has been carried out in ALTA’s Green Propellant Rocket Test Facility using as selected green propellants a light unsaturated dhydrocarbon (propyne) and hydrogen peroxide.