111 N HYDRAZINE BIPROPELLANT ENGINE (HBE) WITH GAS-GAS INJECTION

A thruster, designated LE111, utilizes hydrazine and MON3 as fuel and oxidizer and produces a thrust of 111 N at nominal operating conditions with an Isp of up to 328 s. The thruster is throttleable through the use of separate fuel and oxidizer metering valves and is able to transition to a hydrazine monopropellant mode at any point during its operation. Completed qualification testing has demonstrated a versatile operating box that includes chamber pressure-mixture ratio excursions, heated propellants up to 341 K, and gaseous helium ingestion through propellant flow paths. Overall, the thruster has achieved 15,455 s of accumulated on-time and a maximum continuous burn time of 6,000 s. The thruster achieves its performance through a novel micro-coaxial gas-gas injection scheme and an innovative regeneratively cooled combustion chamber, which uses the oxidizer as the working fluid. The thruster's capabilities and performance recorded during the completed qualification testing are described, and its design is outlined. This paper is published with the permission of the authors granted to 3AF – Association Aéronautique et Astronautique de France (www.3AF.fr) organizer of the Space Propulsion International conference.