The H-I was Japan’s first medium-lift launch vehicle to incorporate liquid-fuel technology, marking a significant advancement in the nation’s space capabilities. Developed by the National Space Development Agency of Japan (NASDA) in the 1980s, the H-I combined Japanese engineering with licensed American technology to create a reliable and cost-effective rocket for launching satellites into low Earth orbit (LEO) and geosynchronous transfer orbit (GTO).
Design and Configuration
The H-I rocket featured a three-stage configuration:
First Stage: A license-built version of the U.S. Thor-ELT stage, utilizing RP-1 and liquid oxygen (RP-1/LOX) as propellants. This stage provided the initial thrust necessary to propel the rocket from the launch pad.
Second Stage: The Japanese-developed LE-5 engine, powered by liquid hydrogen and liquid oxygen (LH2/LOX). This cryogenic engine was the first of its kind in Japan and offered high efficiency for the upper stages.
Third Stage (optional): A solid-fuel motor, the UM-129A, was used for missions requiring GTO. This stage provided the final push to place payloads into higher orbits.
Additionally, the H-I employed Castor 2 solid rocket boosters to enhance lift-off thrust, with configurations of either six or nine boosters depending on the mission requirements.
Launch History and Achievements
The H-I had a commendable launch record, with nine missions conducted between 1986 and 1992, all of which were successful. These missions included the deployment of various satellites:
EGP (Ajisai): Launched on August 12, 1986, this mission marked the first flight of the H-I rocket.
ETS-5 (Kiku-5): Launched on August 27, 1987, this satellite was part of Japan’s experimental communications satellite program.
CS-3A (Sakura-3A) and CS-3B (Sakura-3B): Launched in 1988, these satellites were part of Japan’s communications satellite series.
GMS-4 (Himawari-4): Launched on September 5, 1989, this geostationary meteorological satellite was part of Japan’s weather observation network.
MOS-1B (Momo-1B): Launched on February 7, 1990, this satellite was part of Japan’s ocean observation program.
BS-3A (Yuri-3A) and BS-3B (Yuri-3B): Launched in 1990 and 1991, these satellites were part of Japan’s broadcasting satellite series.
Japanese Earth Resource Satellite (FUYO-1): Launched on February 11, 1992, this satellite was Japan’s first Earth observation satellite.
Legacy and Evolution
The H-I rocket served as a bridge between Japan’s earlier solid-fuel rockets and the fully indigenous liquid-fuel H-II launch vehicle. Its development provided valuable experience in cryogenic propulsion and multi-stage rocket design. The H-I’s success paved the way for the H-II, which further advanced Japan’s space launch capabilities and laid the foundation for subsequent rockets like the H-IIA and H-IIB.
