Experimental Evaluation of a High Test Peroxide Catalyst Chamber for a Hybrid Rocket Engine

Hybrid rocket propulsion technology has recently gained in importance. Within the program “AHRES” at the German Aerospace Center (DLR), a small HRE technology demonstrator was developed, which should deliver data for the validation of a self-developed HRE design software. Instead of a conventional ignition system, for this HRE a catalyst chamber with a silver mesh catalyst is designed to decompose currently up to 0.7 kg/s of 87.5% HTP to steam and oxygen at high temperatures. The chamber consists of the catalyst itself, a mount for the catalyst material, a retainer, an injector manifold, a cooling channel, and a casing. Furthermore, a pressure sensor, a mass flow sensor, and a thermocouple are attached to measure the properties of the decomposition products. 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 developed based on the results of the design tool SHAKIRA. 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 to the results generated by the design tool. The developed and tested catalyst chamber provides a simple, reliable ignition system for hybrid rocket engine based on hydrogen peroxide as oxidiser. The system is capable of igniting repeatedly 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.