Characterization of Advanced Hybrid Rocket Engines

Abstract

In the last years, the discovery of high regression rate liquefying fuels has generated a renewed interest in hybrid propulsion systems due to some advantages in certain applications compared to solid or liquid rockets. The intrinsic safety, simplicity and low cost make hybrid systems appreciable for research at university level. At the University of Stuttgart a 500 N hybrid rocket engine, called MIRAS (MIcro RAkete Stuttgart), has been developed by the student team HyEnD (Hybrid Engine Development) within the DLR STERN (STudentische Experimental RaketeN) program. MIRAS is propelled by a liquefying paraffin-based solid fuel and nitrous oxide as oxidizer. It was designed as a technology demonstrator for a scale-up version with a thrust of 10000 N. The test campaign was conducted with an experimental set-up at the test bench M11.5 at the DLR Lampoldshausen. A ballistic characterization of paraffin-based hybrid rocket fuels with different additives in combination with nitrous oxide and a performance evaluation of the 500 N hybrid rocket engine are carried out. A wide range of operating conditions, fuel compositions, injector geometries and engine configurations are evaluated with this engine. Effects of different injector geometries and post combustion chamber designs on the engine performance are analyzed. Additionally, the appearance of combustion instabilities under certain conditions is described, their effect and possible mitigation techniques are also investigated.