The Development and Operation of Propulsion System for SLIM (Smart Lander for Investigating Moon)

SLIM is a small lunar lander developed by JAXA/ISAS. It was launched on September 7, 2023 (JST) from Tanegashima Space Center by H-IIA Launch Vehicle and achieved pinpoint lunar landing on January 20, 2024. SLIM was designed to demonstrate pinpoint landing technology and to contribute to future lunar and planetary exploration by developing a lightweight spacecraft system. SLIM propulsion system required not only capability of high Delta-V and enough thrust for orbit transfer and lunar landing, but also high controllability of thrusters required for pinpoint landings, as well as a stronger weight reduction than that of conventional spacecraft. To achieve these requirements, we constructed and operated a unique propulsion system that has never been seen on a conventional spacecraft, including a bipropellant propulsion system with a blowdown system, pulse injection operation using 500 N-class thrusters, adoption of a shape memory alloy valve, and a newly developed integrated fuel/oxidizer tank. This paper describes the development and operational results of SLIM propulsion system in detail.