LE-9

The LE-9 is a liquid cryogenic rocket engine burning liquid hydrogen and liquid oxygen in an expander bleed cycle. Two or three will be used to power the core stage of the H3 launch vehicle.

The newly developed LE-9 engine is the most important factor in achieving cost reduction, improved safety and increased thrust. The expander bleed cycle used in the LE-9 engine is a highly reliable combustion method that Japan has put into practical use for the LE-5A/B engine. However, it is physically difficult for an expander bleed cycle engine to generate large thrust, so the development of the LE-9 engine with a thrust of 1471 kN is the most challenging and important development element.

Firing tests of the LE-9 first-stage engine began in April 2017.

On 21 January 2022, the launch of the first H3 was rescheduled to FY 2022 or later, citing technical problems regarding the first stage LE-9 engine.

The LE-9 was operated successfully for the first time, on March 7, 2023. The second stage of that rocket, did not ignite and the mission was a failure. On February 17, 2024, the second launch of H3 was successful and LE-9 operations were successful for the second consecutive time.