Development and Testing of a Carbon Fiber Overwrapped Ablatively Cooled Liquid Rocket Engine using Green Propellants

HyEnD, a student rocketry group from the University of Stuttgart, is developing high-performance liquid rocket engine as part of the BLAST project, aiming to surpass the altitude record for student-built liquid rockets. A performance optimized, lightweight variant of this liquid rocket engine utilizing nitrous oxide and ethanol as propellants, features an ablative combustion chamber liner enclosed within a carbon-fiber-reinforced polymer (CFRP) composite pressure casing. The manufacturing process employs an in-house developed, 4-axis NC-controlled filament winding machine, enabling rapid prototyping of optimized fiber layups and winding patterns. The development cycle involved extensive ignition characterization using an ablatively cooled "battleship" engine to establish a reliable startup sequence and characterize the thermal behavior of the ablative material. The system was iteratively scaled and hot-fire tested at thrust levels ranging from 200 N to 2 kN. The technology achieved flight-proven status during the 2025 European Rocketry Challenge (EuRoC), where a 1 kN variant successfully propelled the LUMINA rocket to a category win. This work demonstrates the feasibility of utilizing automated composite manufacturing for high-pressure rocket engine architectures in student-led aerospace research.