Japans H3 to return to flight with debut launch of lightest configuration

Date:
Thu, 11 Jun 2026 20:05:57 +0000

Description:
Japans H3 rocket will return to flight Friday, with a launch that also marks the The post Japans H3 to return to flight with debut launch of lightest configuration appeared first on NASASpaceFlight.com .

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Japans H3 rocket will return to flight Friday, with a launch that also marks the debut of a new configuration, optimized for smaller payloads. Liftoff is scheduled for a window opening at 00:53 UTC (9:53 a.m. local time) from the Tanegashima Space Center.



Fridays launch is the eighth flight of the H3 , and its first since a failure last December that resulted in the loss of the QZS-5 navigation satellite. During that mission, the rockets second stage was noted to have an
off-nominal startup for its second planned burn, followed by a premature shutdown; however, an investigation has revealed that the failure occurred much earlier in the mission.

The root cause of the failure is now suspected to be a manufacturing defect
in the payload adaptor that connects the satellite to the rockets upper
stage. This had been redesigned for H3, using an adhesively-bonded construction rather than being bolted together, to reduce cost and weight. This is believed to have delaminated, and this, combined with stresses at the point of fairing separation late in the first-stage burn, led to the adaptors structural failure.

The anomaly caused the satellite to break free from the rocket although it remained in place due to the rockets acceleration until the end of the first stage burn and damaged the hydrogen tank pressurization systems on the
second stage. The satellite fell away during the coast between first stage shutdown and second stage ignition, and although the second stage was underperforming during its first burn, this was offset by its lower-than-expected mass due to the missing payload.

For Fridays launch, the payload adaptor has undergone inspection and repair
of any delamination prior to launch, while its performance will be monitored to gather data for future flights. On future flights, the Japan Aerospace Exploration Agency (JAXA) intends to either take the same approach or to reinforce the adaptor with fasteners, depending on mission and performance requirements.



In addition to marking H3s return to flight, Fridays launch is the first flight of the H3-30 configuration. This features a modified first stage, with three LE-9 engines instead of the two used on other versions of the rocket. This allows the first stage to deliver more thrust at liftoff eliminating
the need for solid rocket boosters during the early stages of flight.
Compared with the other H3 configurations, the H3-30 is designed to carry smaller payloads into low-Earth orbit. See Also H3-30S F6 Updates Japanese Section NSF Store Click here to Join L2

The H3 is a two-stage rocket built by Mitsubishi Heavy Industries , with two stages burning cryogenic propellants: liquid hydrogen and liquid oxygen. The first stage is powered by LE-9 engines, with two or four SRB-3 boosters providing additional thrust for launches with the two-engine version of the first stage. The second stage has a single LE-5B-3 engine, with the payload mounted atop the stage enclosed within the rockets payload fairing. H3 can
fly with either a short fairing measuring 10.4 m in length, a longer 16.4 fairing, or a wider fairing for missions that require it. Fridays launch will use the short fairing, with the specific configuration designated H3-30S: the three-character variant number indicating three first-stage engines, no boosters, and a short fairing.

With this being the first H3 mission without solid rocket boosters, it also marks Japans first launch of an all-liquid-propellant rocket, as all of the countrys previous liquid-fueled rockets have used solid motors to augment the first stage at liftoff.

The H3-30s maiden flight marks the eighth launch overall for H3, with the mission designated H3 flight No.6 (F6), with missions F7 and F8 having
already launched. Five of its seven previous launches have been successful; the rockets maiden flight in March 2023 also failed.

The main goal of Fridays launch is to demonstrate the new H3-30
configuration, with the rocket carrying a 1,600-kg mass simulator, Vehicle Evaluation Payload 5 (VEP-5), as its primary payload. VEP-5 is not designed
to separate from the rocket and will remain fixed to its payload attachment fitting for the duration of the mission. Six small satellites are riding aboard the mission as secondary payloads and will be deployed once the second stage reaches orbit. Payload configuration for the H3 F6 mission, VEP-5 is
the silver disk at the top of the stack (Credit: JAXA)

The Platform for Extra and Terrestrial Remote Examination with LCTF (PETREL), or Umitsubame, is a 65-kg satellite built by the Tokyo Institute of
Technology that carries an experimental imaging payload. The payload will be used for both Earth observation and ultraviolet astronomy, depending on whether the satellite is in sunlight or in Earths shadow.

Shizuoka Universitys STARS-X, also known as Shiraito, is the latest in a series of space tether experiments conducted by the university. Another 65-kg satellite, the satellite is designed to split into two sections separated by
a one-kilometer tether and deploy a climber robot to traverse the tether. The mission will also test techniques for capturing space debris.

The Visible Extragalactic Background Radiation Exploration by CubeSat (VERTECS) mission, led by the Kyushu Institute of Technology, will observe background radiation originating from outside our galaxy to study the history of the early universe. VERTECS is a six-unit (6U) CubeSat .

The remaining three payloads are being launched for commercial operators. The Hurtling Orbit Normalizer (HORN) satellites: HORN-L and HORN-R, are a pair of 6U CubeSats being carried for Japanese startup BULL. These will test techniques for deorbiting satellites using a deployable sail, with the two spacecraft using differently sized sails to evaluate their performance. The BRO-22 satellite, being carried for the French company Unseenlabs as part of the Breizh Reconnaissance Orbiter (BRO) constellation, will be used to detect electronic emissions from ships to identify vessels operating without transponder signals that may be engaged in illegal activities. Tanegashimas Yoshinobu Launch Complex during an H3 test firing in 2022. (Credit: JAXA)

H3 F6 will launch from the second pad of the Yoshinobu Launch Complex at the Tanegashima Space Center , located on Tanegashima Island off the southern coast of Kyushu the southernmost of Japans four main islands. The Yoshinobu complex was originally built for the H-II family of rockets, with H-II and H-IIA launches using Pad 1. Pad 2 was constructed in the early 2000s as a backup pad for the H-IIA, but was instead used to launch the larger H-IIB and later H3.

All of the H3s launches to date have taken place from this pad, with integration taking place in a vehicle assembly building (VAB) about 500 m northwest of the pad before the rocket is rolled into position atop a mobile launch platform.

The moment of liftoff for Japanese rockets is termed X0, rather than the more familiar T0 used by many Western operators. The three LE-9 engines will
ignite shortly before this mark in the countdown, with the rocket beginning its climb away from the launch pad at X0.

With no solid rocket motors to jettison, the next major event in the flight will be the separation of the payload fairing, expected around three minutes and 12 seconds after liftoff, with H3 already at an altitude of 125 km and traveling downrange at 3.1 km per second. This will be followed, about 22 seconds later, by main engine cutoff (MECO), when the first stage engines
shut down. MECO occurs much earlier in the flight with the H3-30 compared to other configurations, the extra engine meaning the stage burns through its propellant more quickly.



About eight seconds after MECO, the first and second stages will separate, with second stage ignition expected twelve seconds after separation. The second stages LE-5B-3 engine will burn for 11 minutes and 21 seconds to complete insertion into low-Earth orbit. Deployment of the secondary payloads will begin with PETREL and STARS-X about 61 seconds after the burn ends, concluding with HORN-R at 30 minutes and six seconds mission elapsed time.

Following payload deployment, the mission will enter a coast phase before the second stage restarts for a second burn at X+1 hour, 44 minutes, and 58 seconds. An 18-second burn will deorbit the upper stage with VEP-5 still attached ensuring a safe reentry over the Indian Ocean.

Fridays launch is the first of 2026 for both Japan and the H3 rocket. H3s
next launch is expected in the next few months, going from its smallest configuration for the F6 mission to its heaviest, with the H3-24W due to deploy the HTV-X2 cargo craft bound for the International Space Station.

(Lead image: H3-30 F6 at the launch pad during its Captive Fire Test in March. Credit: JAXA)



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