Regression Rate Measurements in a Hybrid Rocket Engine with Advanced HTPB-based Fuel Mixtures and Hydrogen Peroxide

A new slab combustion chamber employing hydrogen peroxide (H2O2) and hydroxyl-terminated polybutadiene (HTPB) was designed and commissioned by the German Aerospace Center (DLR), Institute for Aerodynamics and Flow Technology (AS) in Braunschweig at the DLR site Trauen. The combustion chamber has four helium-cooled quartz glass windows, which provide an insight into the combustion process above the fuel slab and enable its characterization with optical measurement techniques. The experiment allows studying the combustion process at pressures of up to 25 bars and oxidizer mass flows of up to 250 g/s. A H2O2 catalyst chamber, which delivers a mixture of hot water steam (H2O) and oxygen (O2), enables self-ignition without an additional igniter system. The regression rate during the test runs is measured with two ultrasonic probes and other methods. During the experiments a high-speed camera, a two-color pyrometer and infrared temperature measurements were also used. The first results show a regression rate of about 0.62 mm/s at a mass flux of 86 kg/(m2*s) and a pressure of 20 bars for HTPB with 1% graphite powder