The H3 rocket is a Japanese expendable launch system developed by the Japan Aerospace Exploration Agency (JAXA) and Mitsubishi Heavy Industries (MHI). It is designed as the successor to the H-IIA and H-IIB rockets,with an emphasis on reducing launch costs through the use of the lower-cost LE-9 main engine. The H3 features a modular design with two or three first-stage engines and zero,two,or four solid rocket boosters,allowing it to accommodate a variety of payload sizes. Development began in 2013,and the first flight took place in March 2023;the launch ended in failure when the second-stage engine did not ignite. The first successful test flight occurred in February 2024.
The Japanese government authorized development of the H3 on 17 May 2013.[9] The vehicle is being jointly developed by JAXA and MHI to support a wide range of commercial satellite launches. Compared with the H-IIA,the H3 was designed with simpler,lower-cost engines to reduce manufacturing time,technical risk,and overall expense. JAXA and MHI were responsible for preliminary design work,ground facility readiness,new technology development,and manufacturing. Cost reduction was the primary design goal,with launch prices projected at about US$37 million.[10]
As of 2015,the first H3 launch was planned for Japanese fiscal year (JFY) 2020 in the H3-30 configuration,which lacks solid rocket boosters,followed by a booster-equipped version in JFY21.[11][2]
The newly developed LE-9 engine was the key to cost reduction,improved safety,and higher thrust. The engine employs an expander bleed cycle,a combustion method previously used on the upper-stage LE-5 engine,and never before used on a first-stage.[12] While such cycles typically cannot produce high thrust,the LE-9 was designed to reach 1,471kN (331,000lbf),making its development one of the most significant challenges of the program.[13]
Ground tests of the LE-9 began in April 2017,[14] and the first solid rocket booster tests were conducted in August 2018.[15]
On 21 January 2022,the first H3 launch was postponed to JFY22 or later due to technical issues with the LE-9 engine.[16]
The first launch attempt on 17 February 2023 was aborted just before ignition of the SRB-3 boosters,although the main engines had successfully ignited.[17][18][19] The second launch attempt occurred on 7 March 2023 at 01:37:55 UTC. Approximately five minutes and twenty-seven seconds after launch,the second-stage engine failed to ignite. With the rocket unable to reach the required velocity,JAXA issued a self-destruct command 14 minutes and 50 seconds after launch,destroying the ALOS-3 satellite along with the launch vehicle.[20][21][22][23]
On 17 February 2024,JAXA successfully launched the second test rocket,configured as an H3‑22S. During this flight,the second stage reached the intended orbit,marking the first fully successful H3 launch.[24]
Vehicle description
The H3 is a two-stage launch vehicle. The first stage uses two or three LE-9 engines fueled by 225 tonnes (496,000lb)liquid oxygen and liquid hydrogen (hydrolox) propellants. The first-stage can be fitted with zero,two,or four strap-on SRB-3 solid rocket boosters (SRBs) derived from the SRB-A and fueled with polybutadiene. The second stage is powered by an upgraded LE-5B-3 engine and carries 23 tonnes (51,000lb) of hydrolox propellant.[25][3][26]
Variants
H3 configurations are identified by a two-digit number and a letter. The first digit indicates the number of LE-9 engines on the core stage (two or three),while the second digit indicates the number of SRB-3 solid rocket boosters (zero,two,or four). The final letter specifies the payload fairing:short ("S"),long ("L"),or wide ("W"). For example,the H3-24L has two LE-9 engines,four SRBs,and a long fairing,while the H3-30S has three engines,no SRBs,and a short fairing.[27][28]
As of November2018[update],three configurations were planned:H3-30,H3-22,and H3-24.[27]
The H3-32,a proposed variant with three engines and two SRBs,was cancelled in late 2018 after tests showed that the H3-22 offered better-than-expected performance,reducing the need for the more powerful version. JAXA cited commercial precedent,noting that SpaceX’s Falcon 9 frequently launched satellites into a low geostationary transfer orbit,leaving the satellites to raise themselves to a geostationary orbit. Since commercial clients appeared willing to accept this trade-off,JAXA concluded that customers would prefer the less expensive H3-22 even if it required additional onboard satellite propellant.[27]
As of July2015[update],the minimum H3-30 configuration is to carry a payload of up to 4,000kg (8,800lb) into Sun-synchronous orbit (SSO) for about ¥5 billion(equivalent to¥5.1 billionorUS$46.76 million in 2019)[29] and the maximum configuration is to carry more than 6,500kg (14,300lb) into geostationary transfer orbit (GTO).[2] The most powerful H3‑24 variant will deliver more than 6,000kg (13,000lb) of payload to lunar transfer orbit (TLI) and 8,800kg (19,400lb) of payload to geostationary transfer orbit (GTO) (∆V=1830m/s).
As of October 2019,MHI was also studying two concepts for potential use in NASA’s Lunar Gateway program:an extended second stage,and a heavy-lift version with three liquid-fueled core stages strapped together,similar to the Delta IV Heavy and Falcon Heavy.[30] The proposed H3 Heavy would have a payload capacity of 28,300kg (62,400lb) to low Earth orbit.[31]
Launch services
H3 will have a "dual-launch capability,but MHI is focused more on dedicated launches" in order to prioritize schedule assurance for customers.[32]
As of 2018,MHI is aiming to price the H3 launch service on par with SpaceX's Falcon 9.[32]
↑ A Japanese Fiscal Year starts in April of the year and ends in March of the next year. For this case, it denotes launch will occur no earlier than 1 April 2021, and no later than 31 March 2022.
↑ "Development of the LE-X Engine"(PDF). Mitsubishi Heavy Industries Technical Review. 48 (4). December 2011. Archived(PDF) from the original on 9 July 2015. Retrieved 8 July 2015.
↑ 2020年：H3ロケットの目指す姿(PDF) (in Japanese). JAXA. 8 July 2015. Archived(PDF) from the original on 5 March 2016. Retrieved 8 July 2015.
1 2 3 H3ロケットの開発状況について(PDF) (in Japanese). JAXA. 29 November 2018. Archived(PDF) from the original on 29 November 2018. Retrieved 29 November 2018.
↑ 衛星フェアリングとは (in Japanese). JAXA. Archived from the original on 25 September 2022. Retrieved 25 September 2022.
↑ "宇宙基本計画⼯程表 (令和5年度改訂)"[Basic Plan on Space Policy (2023 Revision)](PDF) (in Japanese). Cabinet Office. 22 December 2023. p.45. Archived(PDF) from the original on 25 December 2023. Retrieved 26 December 2023.
↑ "H3ロケット試験機1号機による先進光学衛星「だいち3号」（ALOS-3）の打上げについて[再設定(その5)]"[Launch of Advanced Optical Satellite "DAICHI-3" (ALOS-3) by H3 Rocket Test Vehicle No. 1 [Reschedule (Part 5)]] (Press release) (in Japanese). JAXA. 4 March 2023. Archived from the original on 4 March 2023. Retrieved 4 March 2023.
↑ H3ロケットの開発状況について(PDF). 宇宙開発利用部会 (in Japanese). 10 December 2019. Archived(PDF) from the original on 10 December 2019. Retrieved 10 December 2019.
↑ "JAXA 主力ロケット「H3」2号機 2024年2月15日に打ち上げへ"[JAXA main rocket "H3" No. 2 to be launched on 15 February 2024]. NHK (in Japanese). 27 December 2023. Retrieved 27 December 2023.
↑ "「H3」ロケット3号機 種子島宇宙センターから打ち上げ成功"["H3" rocket No. 3 successfully launched from Tanegashima Space Center]. NHK (in Japanese). 1 July 2024. Retrieved 30 June 2024.
↑ "HTV-X1". Next Spaceflight. Retrieved 4 July 2025.
↑ Sato, Toshiaki (27 September 2024). H3ロケット30形態試験機の打上げ計画及び超小型衛星相乗りの実施について(PDF). Ministry of Education, Culture, Sports, Science and Technology (in Japanese). Retrieved 28 October 2024.
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