|Manufacturer||Mitsubishi Heavy Industries|
|Country of origin||Japan|
|Launch sites||LA-Y, Tanegashima|
|Boosters - M-34+|
|Specific impulse||283.6 seconds (2.781 km/s)|
|Engines||2 LE-X (LE-9)|
|Specific impulse||432 seconds (4.24 km/s)|
|Thrust||137 kN (30,798 lbf)|
|Specific impulse||448 seconds (4.39 km/s)|
H-III (H-X) is an expendable launch system in development in Japan. H-III rockets are liquid-fuelled with solid-fuel strap-on boosters and are planned to be launched from the Tanegashima Space Center in Japan. Mitsubishi and JAXA have been primarily responsible for design, manufacture, and operation of H-III.
H-III (without boosters) is able to carry a payload of up to 2,100 kg to GTO, compared with the payload of 4,000-6,000 kg for the H-IIA. Its performance to LEO is 3000 kg to 800km high Sun-synchronous orbit . The first H-III without boosters is planned to launch in 2020, and with boosters in 2021.
The development of H-III was authorized by Japanese government 17 May 2013. The H-III launch vehicle is a launch vehicle being developed jointly by JAXA and Mitsubishi Heavy Industries to launch the wide variety of commercial satellites. The H-III was designed with cheaper engines compared to H-IIA, so that manufacturing the new launch vehicle would be more cost-effective, with less risk, in a shorter period of time. JAXA was in charge of preliminary design, readiness of the ground facility, and the development of new technologies for the H-III, while the Mitsubishi Heavy Industries is responsible for manufacturing. The main emphasis in design is cost reduction, with planned launch costs for customers are in range 50-65 mln USD.
The H-III launch vehicle is a two-stage rocket. The first stage uses liquid oxygen and liquid hydrogen as propellants and has none to 6 strap-on solid rocket boosters (SRB-A3) powered by polybutadiene. The first stage is powered by two LE-7B (LE-X) engines, similar to H-IIB. The body diameter (4.5 to 5m) is smaller than 5.2m body of H-IIB to reduce take-off weight and to enable takeoff without solid-fuel boosters. The second stage is powered by a single LE-5B engine. (tentatively). In future, upgrades of the upper stage are planned.