Domestic first without boosters: Successful launch of H3 rocket No. 6

The large-scale H3 rocket No. 6 was launched from the Tanegashima Space Center in Kagoshima Prefecture at 9:53:59 a.m. on June 12. For the first time in a domestic large-scale launch vehicle, it adopted the smallest airframe configuration equipped without solid rocket boosters. The launch was a success, placing all six onboard ultra-small satellites into their designated orbits. The configuration without boosters was developed as a key for cost reduction, and it has finally seen the light of day over three years after the H3 started operations. As the H3 failed last December, this success also marks a successful resumption of launches.

Previous failure... Watching the flight with bated breath

Under clear skies, the simple airframe, resembling a single standing pencil, emitted a roaring sound and slowly began its ascent. Stretching out a faint orange flame, it aimed for the southeastern sky and eventually disappeared behind the clouds. The usual plume of smoke showing the flight path was not seen. At the press base located 3 km south of the launch site, reporters eagerly took photos of its first flight powered solely by the main engines.

The H3 separated its fairing (satellite cover) about 3 minutes after launch. Approximately 3 minutes and 30 seconds into the flight, the first-stage engine finished burning, and the first and second stages separated. After the second-stage engine burned normally for over 11 minutes, the rocket sequentially separated a total of six ultra-small satellites from domestic and international companies and universities, such as the Institute of Science Tokyo and Shizuoka University, from about 16 to 30 minutes after launch.

This time, no large satellite was carried, making it a test flight that utilized a 1.6-ton dummy metal weight instead. However, to make the most of the launch opportunity, ultra-small satellites were onboard. In the failed previous launch of Rocket No. 8, vibrations from the fairing separation are believed to have caused destruction to spread within the satellite-mount section of the second stage. This launch was conducted after implementing countermeasures, and related personnel anxiously watched the progress of the flight.

On the afternoon of June 12, Hiroshi Yamakawa, President of the Japan Aerospace Exploration Agency (JAXA), stated at a press conference: "We take the failure of Rocket No. 8 very seriously, and with restoring trust in mind, we have put all our effort into investigating the cause and taking countermeasures. The many words of encouragement and criticism became the driving force for everyone involved to work together. We will continue working to ensure that Japan's space transportation can demonstrate higher reliability and competitiveness."

"Still halfway there, putting H3 back on track"

The H3 is a two-stage liquid-fuel rocket. It is the common successor to the "H2A," which ended operations last June, and the enhanced "H2B," which ended in 2020, and is developed by JAXA and Mitsubishi Heavy Industries. The government positions it, along with the solid-fuel small vehicle "Epsilon," as a "flagship rocket" for Japan to advance space development and utilization autonomously without relying on other nations. In the future, the launching operations will be transferred from JAXA to Mitsubishi Heavy Industries, just like with the H2A and H2B, to enter the commercial market. Rocket No. 6 has a total length of 57 meters and weighs 271 tons, excluding satellites.

The maiden flight failed in March 2023 because the second-stage engine could not ignite due to an anomaly in the electrical system, resulting in the loss of an Earth observation satellite. Countermeasures were implemented, and the rocket subsequently succeeded five consecutive times up to Rocket No. 7 last October, but Rocket No. 8 failed again last December. The cause is believed to be that peeling occurred during manufacturing inside the adapter that mounts the satellite to the second stage, which then spread due to vibrations during flight.

To prevent a recurrence, future adapter assemblies will add reinforcement measures to the bolt fastening method used in the H2A. However, because Rocket No. 6 was a test vehicle, a previously manufactured adapter was repaired and used. The data acquired during the flight will be helpful for verifying the correctness of the cause investigation into the failure of Rocket No. 8.

Makoto Arita, JAXA's Project Manager who serves as the H3 responsible official, said with a look of relief at the press conference: "It has been half a year since the failure. It felt very short yet long. We were able to come this far thanks to everyone's hard work and cooperation. As a result, we achieved this in a proper way, but we are still halfway there. To put the H3 back on a steady track, we are at a stage where we need to clear another hurdle and will approach this with a tight focus."

Flagship rocket: the path to revival comes into view

Conventionally, domestic large-scale rockets have been equipped with solid rocket boosters to help lift the airframe for a few minutes after launch. However, Rocket No. 6 was launched for the first time in history without boosters, powered solely by the engines of the main body. It has three first-stage engines and zero solid rocket boosters and this configuration is called the "30 (Three-Zero) configuration." Because its development took time, its launch was postponed last fiscal year, and Rockets No. 7 and No. 8 were launched ahead of it due to the circumstances of the satellites they carried.

The "30 configuration" has a launch capacity of 4 tons into a sun-synchronous orbit that circles the Earth north to south, and it will mainly carry satellites for government Earth observation and other purposes. The launch cost was aimed to be around 5 billion yen, which is about half the price of the basic H2A model (with two boosters), based on the price and exchange rate levels at the start of development.

Executive Vice President Masayuki Eguchi, also serving in the capacity of Head of Integrated Defense & Space Systems, at Mitsubishi Heavy Industries, said: "With this 30 configuration, all three configurations of the H3 have now succeeded, but the completion of the first-stage engine is yet to come, as the development of a new type remains. Our top priority is to cut costs without loosening our efforts and to increase competitiveness."

JAXA is currently developing an improved version of the Epsilon called "Epsilon S," but it has repeatedly exploded during static firing tests. The second stage will be temporarily reverted to almost the same as the conventional type, aiming for a launch within this fiscal year. The failure of the H3 last December occurred amid these circumstances, plunging Japan into an abnormal situation where it lacked a stably operating flagship rocket. With the success of Rocket No. 6, the path toward a revival has come into view.

According to the government's Space Basic Plan Timeline (revised last December), launches planned for this fiscal year using the H3 include the "HTV-X" No. 2, a cargo transfer vehicle to carry supplies to the International Space Station (ISS), and the "MMX" probe to explore Mars' moon "Phobos" and return samples to Earth.

Stabilizing H3 is the duty of a technology-oriented nation

The situation surrounding large-scale rockets worldwide has changed drastically over the past decade or so. Historically, Arianespace of Europe pioneered the commercial launch market, and vehicles like the "Ariane 5" held a long-standing dominance. However, the "Falcon 9" from the U.S. company SpaceX, which debuted in 2010, rose to prominence with a rational design that clusters nine engines on its first stage. By achieving first-stage reuse in 2017, it built a monopoly.

The Falcon 9 continues to distance itself from others by repeatedly launching satellites for "Starlink," its own satellite constellation service that deploys communication services by linking numerous small satellites. According to statistics from the U.S. research firm BryceTech, the Falcon 9 accounted for 165 (more than half) of the total 325 orbital launches worldwide last year, sending a total of 3,854 artificial satellites and spacecraft into space.

Meanwhile, the successor to the Ariane 5, the "Ariane 6," has been operational since July 2024, but it is reportedly filling up most of its launch slots after receiving massive orders to launch constellation satellites for the U.S. company Amazon. The new "Vulcan" rocket from the U.S. company United Launch Alliance faces a difficult situation due to delayed engine development combined with booster problems. The rocket of Blue Origin of the United States, "New Glenn," is also in a severe predicament, having suffered a major explosion at its launch pad late last month. The vehicles of Russia, a space superpower that once competed with Ariane, have been removed as major options from the market because nations can no longer use them following the invasion of Ukraine.

As a result, the supply and demand for rockets are currently tight worldwide, presenting a challenge for space development and utilization. A situation where the world relies too heavily on a single system like the Falcon 9 for a massive technology like rockets is also not preferable.

The H3 is a flagship rocket, and its primary mission is to serve Japan's national security, science and technology, and disaster prevention. Its positioning differs from the Falcon 9, which leaped forward on a commercial basis, and it does not simply aim to play catch-up.

However, its stable operation also holds the significance of providing a powerful "alternative choice" for the global market. The government plans to advance the capabilities of the H3, aiming for six to eight or more launches per year. The capacity to accept satellites other than government ones will be just a few times a year, which is not much compared to global demand. Even so, raising the degree of completion of the H3 can be called the duty of Japan as a technology-oriented nation. This success marks an important step toward that goal.