H3 (rocket)

The H3 is a Japanese medium-lift launch vehicle developed by JAXA and Mitsubishi Heavy Industries (MHI). A hydrolox-fuelled rocket, it is the successor to the H-IIA and H-IIB launch vehicles. The H3 uses the LE-9 main engine, which was designed to be less expensive to produce as part of a broader effort to lower launch costs. The rocket has a modular design: its first stage is powered by two or three LE-9 engines and can be fitted with zero, two, or four SRB-3 solid rocket boosters, which are also used on the Epsilon S small-lift launch vehicle. The second stage uses the LE-5B-3 engine, an upgraded version of the engine family used since the H-I rocket. Development of the H3 began in 2013. Its maiden flight in March 2023 failed after the second-stage engine did not ignite. The rocket's first successful flight took place in February 2024. In addition to launching satellites into Earth orbit, the H3 is used to launch the HTV-X cargo spacecraft to the International Space Station and is planned to launch the Martian Moons eXploration and Lunar Polar Exploration Mission probes.