THE LAST ACHIEVEMENTS IN THE DEVELOPMENT OF A ROCKET GRADE HYDROGEN PEROXIDE CATALYST CHAMBER WITH FLOW CAPACITY OF 1 KG/S

Kurzfassung

Worldwide, the hybrid rocket propulsion technology gained in importance recently. A new innovative hybrid rocket engine concept is developed at the German Aerospace Center (DLR) within the program “AHRES”. This rocket engine is based on hydroxyl-terminated polybutadiene with metallic additives as solid fuel and rocket grade hydrogen peroxide (high test peroxide: HTP) as liquid oxidiser. Instead of a conventional ignition system, a catalyst chamber with a silver mesh catalyst is designed, to decompose the HTP to steam and oxygen at high temperatures up to 615 °C. The newly modified catalyst chamber is able to decompose up to 1.3 kg/s of 87,5% HTP. Used as a monopropellant thruster, this equals an average thrust of 1600 N. The catalyst chamber consists of the catalyst itself, a mount for the catalyst material, a retainer, an injector manifold and a casing. Furthermore, a pressure sensor, a mass flow sensor and a thermocouple can be attached to measure the properties of the decomposition products. With the described catalyst chamber a number of tests under steady conditions are carried out using 87.5 %wt hydrogen peroxide with different flow rates and constant amount of catalyst material. The chamber is mounted on a test-bed, which comprises attachment, peroxide storage, feed system, valves, data acquisition and control. By determination of the decomposition temperature the integrity of decomposition is verified and compared to theoretical prediction. The catalyst chamber is designed using the self-developed software tool SHAKIRA. A short description of the tool features is given. The applied kinetic law which determines catalytic decomposition of HTP within the catalytic chamber is also given and commented. Several calculations are carried out to determine the appropriate geometry for complete decomposition with a minimum of catalyst material. The experimental results show good agreement with the results generated by the design tool. The developed catalyst chamber provides a simple, reliable ignition system for hybrid rocket propulsion systems based on hydrogen peroxide as oxidiser. The system is capable for multiple re-ignitions without the need to meet an optimal ignition point. Such a system behaves like a hypergolic engine in terms of ignition, but no hazardous substances are required. The developed hardware and software can be used to design full scale monopropellant thrusters based on HTP and catalyst chambers for hybrid rocket engines. Both concepts are under considerations within DLR.