H3 (rocket)

The development of the H3 was authorized by the Japanese government on 17 May 2013.[7] The H3 Launch Vehicle is being jointly developed by JAXA and Mitsubishi Heavy Industries (MHI) to launch a wide variety of commercial satellites. The H3 was designed with cheaper engines compared to the H-IIA, so that manufacturing the new launch vehicle would be faster, less risky, and more cost-effective. JAXA and Mitsubishi Heavy Industries were in charge of preliminary design, the readiness of ground facilities, development of new technologies for the H3, and manufacturing. The main emphasis in design is cost reduction, with planned launch costs for customers in the range of US$50-65 million.[8]

Firing tests of the LE-9 first-stage engine began in April 2017.[9] In August 2018, the first tests of the solid rocket boosters were carried out.[10]

In earlier plans, the first H3 was to be launched in fiscal year 2020 in the H3-30 configuration which lacks solid-rocket boosters, and in a later configuration with boosters in FY2021.[2][11] During the development of LE-9, many technical problems were found and the engine's development was split into two stages.[6] The type 1 engine would have used a fuel injector machined with conventional methods, along with a suboptimal liquid hydrogen turbopump to avoid vibration resonance. The type 2 engine will use a 3D-printed injector , and the improved turbopump will suppress vibration.[6] To compensate for the suboptimal performance of the type 1 LE-9 engines, the first H3 test flight was changed to use the H3-22 configuration which uses two solid-rocket boosters.[6]

The H3 Launch Vehicle is a two-stage rocket. The first stage uses liquid oxygen and liquid hydrogen as propellants and carries zero, two or four strap-on solid rocket boosters (derived from SRB-A3) using polybutadiene fuel. The first stage is powered by two or three LE-9 engines which uses a expander bleed cycle design similar to the LE-5B engine.[12] The fuel and oxidizer mass of the first stage is 225 metric tons. The second stage is powered by a single engine which is an improved LE-5B. The propellant mass of the second stage is 23 metric tons.[3][13]

Each H3 booster configuration has a two-digit plus letter designation that indicates the features of that configuration. The first digit represents the number of LE-9 engines on the main stage, either "2" or "3". The second digit indicates the number of SRB-3 solid rocket boosters attached to the base of the rocket, and can be "0", "2" or "4". All layouts of the solid boosters are symmetrical. The letter at the end shows the length of the payload fairing, either short, or "S", or long, or "L". For example, an H3-24L has two engines, four solid rocket boosters, and a long fairing, whereas an H3-30S has three engines, no solid rocket boosters, and a short fairing.[14]

As of November 2018, three configurations are planned: H3-30, H3-22, and H3-24.[14]

A previously mentioned variant, the H3-32, was cancelled in late 2018 when the performance of the H3-22 variant, sporting one less engine on the core booster, was found to be greater than anticipated, putting it close to the H3-32's performance. While the H3-32 would have provided greater performance, JAXA cited SpaceX's experience with their Falcon 9 rocket, which routinely lifted commercial communications satellite payloads to less than the gold standard geosynchronous transfer orbit of 1500 m/s of delta-V remaining to get to geostationary orbit, leaving the satellites themselves to make up the difference. As commercial clients were apparently willing to be flexible, JAXA proposed redefining their reference transfer orbit to something lower, believing commercial clients would prefer the less expensive (if slightly less capable) H3-22 rocket, even if the client had to then load additional propellant onto their satellite for it to reach GEO, than a more expensive H3-32.[14]

As of October 2019, MHI is considering contributing two variants for the Gateway project: an extended second stage variant, and the H3 Heavy variant which would comprise three first-stage liquid-fuel boosters strapped together, similar to the Delta IV Heavy, Atlas V Heavy, and the Falcon Heavy rockets. It would have a payload capacity of 28,300 kg to low earth orbit. [15]

H3 will have a "dual-launch capability, but MHI is focused more on dedicated launches" in order to prioritize schedule assurance for customers.[16]

As of 2018, MHI is aiming to price the H3 launch service on par with SpaceX's Falcon 9.[16]

Sources: Japanese Cabinet[17]

Date and time (UTC)	Flight	Type	Launch site	Payload(s)	Outcome
2020 (TBD)	TF1	H3-22S[6]	LP2, Tanegashima	ALOS-3	Planned
2021 (TBD)	TF2	H3	LP2, Tanegashima	ALOS-4	Planned
February 2022	F3	H3-24L		HTV-X1	Planned
2022 (TBD)	F4	H3		DSN-3	Planned
2022 (TBD)		H3		Inmarsat	Planned
2023 (TBD)		H3		ETS-IX	Planned
2023 (TBD)		H3-24L		HTV-X2	Planned
2023 (TBD)		H3		QZS-5	Planned
2023 (TBD)		H3		QZS-6	Planned
2023 (TBD)		H3		QZS-7	Planned
2024 (TBD)		H3-24L		MMX	Planned
2025 (TBD)		H3		LiteBIRD	Planned
(TBD)		H3		IGS-Optical 9	Planned
(TBD)		H3		IGS	Planned
(TBD)		H3		IGS	Planned
(TBD)		H3		IGS	Planned

Wikimedia Commons has media related to H3 (rocket).

• JAXA H3 English page
• JAXA H3 pamphlet
• JAXA TODAY No.10