Japan's new H3 rocket took off Friday on its second test flight; its success is an important milestone for the launch vehicle poised to power nearly all of the Japanese space program's missions into orbit over the next decade.
The 187-foot-tall (57-meter) H3 rocket lifted off from the Tanegashima Space Center in southwestern Japan at 7:22 pm EST Friday (00:22 UTC Saturday) with a dummy payload and two smaller satellites.
Two hydrogen-fueled main engines and a pair of strap-on solid rocket boosters ignited with 1.6 million pounds of thrust, vaulting the H3 rocket off its launch pad on a trajectory east from Tanegashima, then south over the Pacific Ocean. The strap-on boosters burned out and jettisoned about two minutes into the flight, and the core stage's LE-9 engines fired for nearly five minutes.
After releasing the first stage to fall into the Pacific, the H3's second stage lit a single LE-5B engine, also burning liquid hydrogen and liquid oxygen, for an 11-minute burn to accelerate the rocket to orbital velocity. Once in orbit, the H3 deployed an Earth-imaging microsatellite for Canon Electronics and a small Japanese CubeSat to test an infrared Earth observation sensor in space.
The H3 rocket circled Earth one time before reigniting its upper-stage engine for a braking maneuver to bring it back into the atmosphere, where it was expected to burn up during reentry a couple of hours after liftoff. Before falling back to Earth, the upper stage tested its payload separation mechanism with a dummy payload called VEP-4, a nearly 3-ton metallic column aboard the rocket to simulate the mass of a medium-size satellite.
Success, at last
Officials from the Japan Aerospace Exploration Agency (JAXA) were thrilled with the outcome of the test flight. Publicly available US military tracking data indicated the rocket reached an orbital altitude of approximately 420 miles (680 kilometers), with an inclination of 98.1 degrees to the equator, right on target.
"The H3 finally gave its first cry. The launch was a perfect success," said Masashi Okada, JAXA's H3 project manager, according to a report by Japan's Mainichi Shimbun newspaper.
The Japanese government approved development of the H3 rocket in 2013, and the program has cost approximately 220 billion yen (nearly $1.5 billion). JAXA funded most of the cost, while Mitsubishi Heavy Industries (MHI) serves as prime contractor for the H3 rocket. MHI will also take over commercial management of the H3 program.
The H3's first launch into orbit follows another milestone Japan's space program achieved last month, when the country's robotic SLIM lunar lander touched down on the Moon. This made Japan the fifth nation to accomplish a soft landing on the lunar surface.
"We are very happy to see such great achievements in the space field following the successful SLIM moon landing," Japanese Prime Minister Fumio Kishida wrote in a post on X. "I would like to express my respect for the efforts of everyone involved over the years and hope that Japan's core rockets will continue to steadily accumulate achievements."
Once in operational service, the H3 rocket will launch Japanese scientific satellites, solar system exploration missions, navigation satellites, spy satellites, and resupply freighters to the International Space Station. Japanese officials also want the H3 to compete for commercial launch business on the global market, but there's stiff competition for commercial launch contracts. SpaceX dominates the commercial launch market, and a bevy of new rockets are joining the competition.
So far, the H3 hasn't made much of a mark in the global launch market. Nevertheless, the H3 is critical for the future of Japan's space program. It is cheaper and more capable than Japan's workhorse H-IIA rocket, which is due for retirement after more than 20 years in service.
A chance for a do-over
The successful launch Friday occurred nearly one year after the H3 rocket faltered on its first test flight. On that launch, the H3 rocket's second-stage engine failed to ignite a few minutes after liftoff, causing the launcher and its Earth observation satellite payload to plunge into the sea east of the Philippines.
After an exhaustive investigation, engineers identified three possible electrical problems that could have caused the H3 failure last year. Investigators could not identify a definitive cause, so engineers made adjustments to the second H3 rocket to eliminate the risks from all three possibilities.
The board of inquiry probing the H3 launch failure determined an electrical fault caused a loss of power on the rocket's second stage, immediately after the computer sent a signal to ignite the engine. But the investigators couldn't pinpoint the cause and instead identified three failure scenarios—a short circuit in an electrical "exciter" or one of two overcurrent conditions within the electrical system.
In a video released by JAXA before Friday's launch, Okada, the H3 project manager, said the investigation wasn't straightforward. Without any hardware to recover and inspect, engineers focused on the stream of telemetry data beamed down from the rocket in the moments just before the failure.
"The flight data (from the first H3 test flight) was pretty tricky, with a limited number of data points and time resolution," he said. "This means we only had intermittent data.
"There are various ways to recover from this kind of failure," Okada said. "One way is pinpoint the exact cause, find clear evidence, and narrow it down to a single issue. The other, which is what we did, was to identify a reasonable number of causes, address them, and look ahead to the second launch.
"We were in a challenging position," he said. "Around four to five months after (the first launch), we felt quite stuck. However, we were relieved when we finally began to see a bit of light at the end of the tunnel after that."
Engineers addressed these potential causes by adding insulation and inspections of electrical components on the rocket, improving quality-control procedures, and removing an unnecessary diode that could have contributed to one of the failure scenarios. JAXA released the final report from the investigators in October, and the agency gave the green light to start final preparations for the second H3 test flight.
Over the past few months, ground crews on the southwestern Japanese island of Tanegashima stacked the H3's core stages, solid rocket boosters, and payload compartment. The fully assembled second H3 rocket rolled out to its launch pad a few days before liftoff.
This time, JAXA did not risk an operational satellite on the H3 rocket. A $200 million land-imaging satellite named ALOS-3 was lost on the H3's failed launch last year. For the second H3 test flight, engineers fabricated a metallic column called a Vehicle Evaluation Payload to fly in place of a primary satellite. Two relatively low-cost small satellites rode into orbit as rideshare payloads.
The metallic structure has the same mass and center of gravity as ALOS-3, and the H3 rocket launched on the same trajectory as the doomed test flight last year. These similarities will allow engineers to compare the performance of two H3 rockets flying on identical missions.
No launch gap for Japan
The H3 isn't a revolutionary rocket. It's an evolution of Japan's H-IIA and H-IIB rockets, which have amassed a laudable success record in more than 22 years of service.
The H-IIA has a 98 percent success rate in 48 flights since 2001, while the more powerful H-IIB was 9-for-9 before retiring in 2020. There are two more H-IIA rockets left in Japan's inventory before the H3 becomes the sole Japanese rocket available to launch most of the country's space missions.
With Friday's successful launch, the H3 appears ready to take up this responsibility. There won't be a lapse in access to space for Japan, as Europe currently faces following the retirement of the Ariane 5 rocket before the debut of its replacement, the Ariane 6, later this year.
The Japanese government plans to launch around 20 missions on H3 rockets by 2030. Reuters reported MHI, the rocket's manufacturer, has a long-term target of launching between eight and 10 H3 flights per year. According to Reuters, this would require additional production capacity, because the contractor's factories can currently only produce five to six H3 rockets a year.
MHI has some selling to do if it's going to reach this goal. Japanese government demand for H3 flights will only account for a few missions per year, and MHI has announced just a single commercial launch deal for the H3 rocket. That agreement, signed in 2018, is for the launch of an unspecified communications satellite for Inmarsat, a company acquired by Viasat last year.
The H3 will come in four basic configurations, with two or three core stage engines and zero, two, or four strap-on solid-fueled boosters. The rocket can also launch with a short or long payload fairing, depending on specific mission requirements.
The long-term goal for JAXA and MHI is to reduce the cost of an H3 launch to less than half that of an H-IIA mission, with a target of 5 billion yen ($33 million) per flight for the lightest version of the H3, without any solid rocket boosters. In that configuration, the H3 can deliver a payload of more than 4 metric tons (8,800 pounds) into a Sun-synchronous polar orbit a few hundred miles above Earth.
The most powerful version of H3 has a payload capacity of more than 6.5 metric tons (14,300 pounds) to a higher geostationary transfer orbit, according to a JAXA fact sheet. This version of the H3 rocket will launch Japan's next-generation HTV-X supply ships to the International Space Station, and future H3s could send cargo freighters to resupply the future Gateway space station around the Moon.
It's not clear how often the H3 will need to fly to reach the $33 million goal, but it likely assumes some commercial uptake. JAXA says the cost savings for H3 are realized through more efficient manufacturing processes and the use of more commercial off-the-shelf components.
Officials in the Japanese government are already plotting a replacement for the H3. A space policy document released by Japan's Cabinet Office last June included language endorsing the development of a reusable rocket to follow the H3, with a first launch sometime in the 2030s.
JAXA awarded MHI a contract for joint studies on this proposed next-generation launcher, which would have a recoverable and reusable first-stage booster. There's no design yet for this still-unnamed rocket, and officials have not decided on a fuel. Liquid methane or liquid hydrogen are the top contenders.
