The H-IIB Launch Vehicle is the largest rocket in Japan and was jointly developed by the Japan Aerospace Exploration Agency (JAXA) and Mitsubishi Heavy Industries, Ltd. (MHI). Its main mission is to launch the H-II Transfer Vehicle (HTV), which has a mass of about 16.5 tons, into an orbit at an altitude of about 300 kilometers in order to transport supplies to the International Space Station (ISS). Following the retirement of the Space Shuttle, the importance of the HTV mission has increased and it became important to maintain its reliability as a launch vehicle and to secure launch schedules. The H-IIB Launch Vehicle managed to maintain and improve its reliability and reduce operation costs by taking on the specifications and composition of devices used for the H-IIA Launch Vehicle. There are many common parts in facilities and operating procedures, thus while increasing operation opportunities, we can operate different rockets efficiently and gain experience.

The H-IIB Launch Vehicle is equipped with two LE-7A engines used for the H-IIA Launch Vehicle and the propellant tank is enlarged, thus the diameter of the first-stage rocket became 5.2 meters. We also developed a new satellite faring for the HTV, the 5S-H type, whose is larger than conventional H-IIA fairing. While we renewed technology where necessary, we also utilized time-proven technologies (the engine and separation mechanism) to expand the range of applications. Consequently, we could achieve these two fruitful results, namely "performance enhancement" and "technological revolution" of the launch vehicle, through the improvement of the H-IIA Launch Vehicle as a stepping stone.