IM-1 Lunar Landing Powered Descent: Propulsion System Flight Data and Analysis

On February 22, 2024, Odysseus, a robotic lunar lander developed by Intuitive Machines, performed the first U.S. soft landing on the Moon in over 50 years and marked the first commercial spacecraft to successfully land on the lunar surface. That lander was powered by an in-house developed liquid oxygen/liquid methane rocket engine, which marked another significant milestone for liquid propulsion development: the first LOX/LCH4 spacecraft and the first lander to utilize cryogenic propellants. The main engine was fired a total of six times during the mission for engine commissioning, trajectory correction, lunar orbit insertion, orbit correction, orbital descent, and landing. During the powered descent, flight software actively controlled the engine thrust level, adjusting acceleration to target the intended landing site, and softly land. To allow Odysseus to descend to the lunar surface after the braking phase, the engine needed to be capable of deep throttling, from 100% to 30% total thrust. Nominal engine operations regulate propellant feed pressures to a constant value, but due to anomalously high usage of helium during the Earth-to-Moon transit, the propulsion system performed the final 13-minute maneuver in a blow-down mode. The burn was successful, with all data downlinked post-landing indicating nominal operations. Pressure, temperature, and acceleration data were used to determine propulsion system health and operational status throughout the maneuver and was compared with fluid analysis and ground-data derived performance models. As a result of this successful mission and validation under flight conditions, both the VR-900 engine technology and the cryogenic fluid management system have now achieved Technology Readiness Level 9.