LE-5B

The LE-5B rocket engine is an improved version of the LE-5A engine developed for the second stage of the H-II rocket. It was the first rocket engine in the world to implement the expander bleed cycle, which utilizes hydrogen, originally used for cooling the combustion chamber, as turbine gas for pump drive. The LE-5B-3 engine, which has been enhanced for both performance and cost reduction compared to the LE-5B-2 engine used in the H-IIA/B rockets, is currently installed on the H3 rocket.