The eighth H3 rocket lifts off from the Tanegashima Space Center in Kagoshima Prefecture on Dec. 22. (Kazushige Kobayashi)

EDITORIAL: JAXA faces long road to recover international trust

（社説）Ｈ３ロケット　信頼回復へ　道のり遠く

Failure struck the launch of the eighth unit of the H3 rocket jointly developed by the Japan Aerospace Exploration Agency and Mitsubishi Heavy Industries Ltd.

The second stage engine stopped burning prematurely and JAXA was unable to place into orbit the Michibiki No. 5, a quasi-zenith satellite that would have been part of the domestic positioning system.

The seven-satellite system would have been completed with the launch of another satellite in February and allowed Japan to move away from dependence on the U.S. global positioning system.

But that reality is now farther away.

The launch was originally set for early December, but that was delayed due to equipment trouble. A second attempt last week was automatically aborted moments before liftoff.

JAXA explained there was the possibility that pressure in the fuel tank decreased after the fairing protecting the satellite during the launch separated abnormally.

This was the second failed launch of the H3 rocket following the first unit two years ago. While the launch of the first unit was resumed in about a year’s time, JAXA was unable to specify the exact cause.

As a result, the agency implemented all possible preventive measures based on the conceivable scenarios for the failure.

An evaluation from a wide perspective, including what, if any, relationship there was with the first failure and the delay in subsequent launches, should be conducted.

About 20 launches for the flagship H3 rocket are scheduled until fiscal 2030, but there will be no avoiding an impact on that timetable.

Because Japan is part of a joint international project, the reliability of its space exploration capabilities will be called into question.

There will be a need to fully explain what happened through an objective investigation and publicize how that is being carried out.

JAXA now faces the difficult task of both finding the cause and ensuring no recurrence while also moving toward a quick resumption of launches.

While failure is a given for space exploration, reliability in a rocket can only be gained by accumulating successful launches.

The road to recovery is a long one.

In general, a launch success rate of 95 percent is considered a benchmark for reliability, but the H3 is now at about 70 percent.

The predecessor H-2A rocket that ended operations this year had a success rate of 98 percent, but due to the associated high costs that rocket had insufficient international competitiveness.

The H3 was developed while trying to achieve not only a high capability, but also ease of use and reduced costs.

But the design and development structure may now have to undergo a fundamental review.

Since a failed launch three years ago, the smaller flagship Epsilon rocket has also not resumed operations.

Japan now finds itself in the serious position of not being able to launch any satellites because it cannot use either flagship rocket.

There will be a need to assess not only the technological mistakes, but also whether sufficient personnel and money were invested to match JAXA’s plans and schedule.

--The Asahi Shimbun, Dec. 24

宇宙航空研究開発機構（ＪＡＸＡ）と三菱重工業が開発したＨ３ロケット８号機の打ち上げが、失敗に終わった。第２段エンジンの燃焼が予定より早く停止し、搭載していた「日本版ＧＰＳ」と呼ばれる準天頂衛星みちびき５号機を予定の軌道に入れることができなかった。
　日本版ＧＰＳは来年２月にあと１機打ち上げれば７機体制となり、米国のＧＰＳに依存しない測位が可能となるはずだった。実現が遠のいた。
　当初、今月上旬の打ち上げを予定していたが、機器の不具合で延期され、さらに再設定された先週は、打ち上げの直前に緊急停止していた。
　ＪＡＸＡによれば、打ち上げ時に衛星を保護するためのカバー「フェアリング」が異常な外れ方をしており、燃料タンクの圧力低下につながった可能性があるという。
　Ｈ３の失敗は２年前の初号機に続き、２回目となる。このときは約１年後に再開にこぎ着けたが、必ずしも原因を一つに特定できたわけではない。考えうる複数のシナリオのすべてに再発防止策を講じるという方法をとった。初号機の失敗や打ち上げ延期との関連の有無を含め、幅広い視点からの検証が欠かせない。
　国の大型基幹ロケットＨ３は、２０３０年度までに約２０回の打ち上げが予定されている。影響は避けられない。国際共同で進めるプロジェクトもあり、日本の宇宙開発に対する信頼性も問われる。調査に客観性を持たせ、経過を公表するなどして説明責任を果たしていく必要がある。原因究明や再発防止の徹底だけでなく早期再開との両立という難しい課題にも直面する。
　宇宙開発には失敗がつきものとはいえ、ロケットは打ち上げ実績を重ねることでしか得られない信頼もある。回復への道のりは遠い。
　一般的には成功率９５％が信頼性の目安とされ、現段階では７割程度にとどまる。
　今年運用を終えた先代のＨ２Ａロケットは、成功率９８％を実現したが、コスト高のため国際的な競争力の点では不十分だった。そのため性能だけでなく、使い勝手の良さやコスト削減を追求したのがＨ３だ。設計や開発体制が根本から問われる可能性もある。
　小型の基幹ロケット「イプシロン」も３年前に失敗して以降、再開のめどが立たない。基幹ロケットがいずれも使えず、衛星の打ち上げができない厳しい状況に置かれた。失敗の技術的な検証だけでなく、計画やスケジュールに見合った人と予算が投じられているのかといった視点からの検討も必要だ。

(2025年12月24日)