Japan’s flagship H3 rocket fails on first test flight

Japan’s first H3 rocket lifts off on an ill-fated test flight with the ALOS 3 Earth observation satellite. Credit: JAXA

Japan’s first H3 rocket, designed to launch satellites and resupply space stations, fell back to Earth Monday (U.S. time) after its second stage engine failed to ignite five minutes into the new launcher’s inaugural test flight, destroying the rocket and a three-ton Earth observation spacecraft.

After a decade in development and a last-second abort on its first launch attempt last month, the H3 rocket was loaded with super-cold liquid hydrogen and liquid oxygen Monday as the countdown smoothly ticked down to liftoff at 8:37:55 p.m. EST (0137:55 GMT Tuesday). The rocket’s two core stage engines ignited in the final seconds of the countdown, then two strap-on solid rocket boosters lit to propel the H3 off the launch pad at the Tanegashima Space Center.

Riding 1.6 million pounds of thrust, the H3 rocket quickly vaulted off its launch pad at Tanegashima, located on a bluff overlooking the Pacific Ocean on the southwestern part of the Japanese island chain. Liftoff occurred at 10:37 a.m. Japan Standard Time.

The rocket’s design builds on propulsion technology used on Japan’s earlier generation of H-2A and H-2B rockets, but its twin LE-9 core stage engines use a new engine cycle and produce more thrust than the engines used on previous Japanese launch vehicles. Problems with the new main engine for the H3 rocket were largely to blame for delays in its first flight from 2020.

But the LE-9 engines appeared to function as expected on the first H3 test flight. The rocket’s two solid rocket boosters burned out and jettisoned about two minutes into the mission, followed by separation of the H3’s nose cone three-and-a-half minutes after liftoff, revealing the Japanese-built Advanced Land Observing Satellite 3 payload. Ground-based cameras showed the rocket making a right turn, as expected, to steer from its initial track east from the launch site onto a southerly course to target a polar orbit.

The rocket shut down its LE-9 main engines at T+plus 4 minutes and 56 seconds. Eight seconds later, telemetry data streaming from the rocket back to a ground station confirmed separation of the H3’s first stage from the second stage of the launcher.

The upper stage was supposed to ignite its hydrogen-fueled LE-5B-3 engine at T+plus 5 minute and 16 seconds, but data from the rocket indicated the engine did not start. Telemetry from the H3 launcher also showed its velocity decreasing after reaching a top speed around 8,000 mph (13,000 kilometers per hour), about half of the velocity required to reach a stable orbit around Earth.

Without the thrust from the upper stage engine, the rocket continued slowing as it arced to a maximum altitude of nearly 400 miles (about 630 kilometers), according to data displayed on a live launch broadcast produced by the Japan Aerospace Exploration Agency, or JAXA.

“Because the second stage engine did not fire, there was no prospect of being put into the specified orbit,” JAXA said.

JAXA said range controllers sent a destruct command to the rocket after determining there was “no possibility of achieving the mission.” Debris from the rocket and the three-ton ALOS 3 satellite fell over a remote stretch of ocean a few hundred miles east of the Philippines.

JAXA said an investigation board will probe the cause of the H3 launch failure.

“It is extremely regrettable that the launch of the H3 rocket, which has been under development as a new flagship rocket, failed, and I am sorry that we could not live up to the expectations of the people and everyone involved,” said Keiko Nagaoka, Japan’s minister of education, culture, sports, science and technology.

“We will investigate the cause as soon as possible, formulate countermeasures, and respond with all our might and with a sense of urgency while cooperating with related organizations so that we can meet the expectations of the H3 rocket,” she said.

The H3 will replace Japan’s workhorse H-2A rocket and the H-2B launch vehicle, which have amassed a 98% success rate in 55 missions since 2001.

Japan’s space agency started development of the H3 rocket in 2013, with a goal of slashing in half the cost per launch of the H-2A rocket. The new rocket has a cheaper, lighter, and more powerful version of the hydrogen-fueled engine that flies on the H-2A rocket, and flies with two or three main engines instead of a single powerplant on the core stage of the H-2A.

The maiden flight of the H3 rocket was powered by two LE-9 core stage engines, each producing more than 330,000 pounds of thrust, a third more power than the LE-7A engine used on the H-2A rocket. Future H3 missions could fly with three main engines, allowing the rocket to lift off without the need for any solid rocket boosters.

Engineers also upgraded the H-2A rocket’s solid rocket boosters for the H3 program, with the new SRB 3 solid-fueled motors on the H3 rocket capable of generating 20% more thrust. Designers achieved cost savings by simplifying the connection between the boosters and the core stage of the H3 rocket, and by using a fixed nozzle on the SRB 3 motor, instead of a vectoring nozzle on the H-2A rocket’s solid-fueled boosters.

Japan’s first H3 rocket lifts off from the Tanegashima Space Center. Credit: JAXA

The LE-5B-3 engine on the H3 rocket’s upper stage, which did not ignite on the test flight Monday, is designed for multiple firings in space. It’s a modernized version of the LE-5B engine flown on the H-2A rocket, capable of generating more than 30,000 pounds of thrust in space.

Changes to the upper stage engine introduced on the H3 rocket improved the LE-5B’s fuel efficiency and firing duration.

In order to achieve the improvement in fuel efficiency, engineers modified the design of the engine’s mixer, which combines liquid hydrogen from the fuel turbo pump with gaseous hydrogen from the engine coolant channels. Designers changed the turbine in the engine’s fuel turbopump to reduce the risk of fatigue during extended duration missions with multiple upper stage firings.

The development of the H3 rocket cost about 200 billion yen, or $1.5 billion.

The first test flight of the H3 was delayed from 2020 due to problems during testing of the new LE-9 main engine, which employs an expander bleed cycle more often used on lower-thrust upper stage engines. The expander bleed cycle uses super-cold hydrogen fuel to cool the engine’s combustion chamber, then the heated hydrogen gas is used to drive the engine’s fuel and oxidizer turbopumps. The H-2A rocket’s LE-7A engine uses a different design operating on a staged combustion cycle.

The LE-9 also introduces electrically actuated valves and new manufacturing techniques, including 3D printing of components.

Engineers discovered cracked rotor blades in the LE-9 engine’s fuel turbopump after hotfire testing in 2020, and found holes in the internal wall of the engine’s combustion chamber. The engine development team redesigned the turbine blades and the fuel and oxidizer turbopumps to resolve the problems, then performed more hotfire tests before clearing the H3 rocket for its inaugural test flight.

Artist’s illustration of the H3 rocket’s upper stage, with its LE-5B-3 engine firing. Credit: JAXA

Mitsubishi Heavy Industries led the Japanese industrial team developing the H3 rocket under contract with JAXA, Japan’s space agency. MHI also led the design and development of the cryogenic liquid-fueled LE-9 and LE-5B-3 engines. IHI Aerospace developed the solid rocket boosters, building on the design used on the H-2A rocket. Japan Aviation Electronics Industry Ltd. worked on the H3 rocket’s guidance system.

MHI aims to launch the H3 rocket for as low as $50 million per mission, about 50% of the cost of an H-2A rocket flight. Japan has launched 46 H-2A missions, plus nine flights of the heavier H-2B rocket on resupply missions to the International Space Station. A handful of H-2A rockets remain to fly, and the H-2B is already retired.

The H3 rocket comes in four configurations, with the number of main engines, solid rocket boosters, and the size of the payload fairing adjustable based on mission requirements. The H3 rocket for Test Flight 1, or TF1, flew in the H3-22S configuration with two first stage engines, two strap-on solid rocket boosters, and a short payload fairing.

According to JAXA, the H3 rocket in its most powerful configuration can launch payloads of up to 6.5 metric tons into geostationary transfer orbit, a destination favored by many large telecommunications satellites. That is comparable to the lift capability of SpaceX’s Falcon 9 rocket.

Japanese engineers completed a hold-down test-firing of the first H3 rocket’s main engines at Tanegashima in November, then integrated the two solid-fueled strap-on motors and the payload fairing ahead of mission’s first launch attempt in February, which was aborted moments before liftoff due to an electrical problem.

The Advanced Land Observing Satellite 3, or ALOS 3, spacecraft in a clean room prior to integration with its H3 launcher. Credit: JAXA

JAXA and MHI designed the H3 rocket to launch Japanese scientific satellites, intelligence-gathering and national security spacecraft, and Japan’s new HTV-X resupply freighter for the International Space Station. Japan also plans to use the H3 rocket to launch a version of the HTV-X supply ship to the Gateway mini-space station NASA and other space agencies will construct in orbit around the moon.

Officials hope to attract commercial launch business for the H3 rocket, which will compete with SpaceX’s Falcon 9 rocket, ULA’s Vulcan launch vehicle, and Europe’s Ariane 6 rocket. Like the H3, the latter two vehicles are expendable in design, and have not yet flown, while the Falcon 9 is partially reusable and commands a leading position in the global commercial launch market.

The Advanced Land Observing Satellite 3, or ALOS 3, mission lost on the H3 rocket’s test flight Monday was supposed to collect wide-swath, high-resolution images of land surfaces around the world, providing observations for disaster management, mapping, and environmental monitoring.

ALOS 3 was expected to separate from the H3 rocket’s upper stage in a 419-mile-high (675-kilometer) orbit about 17 minutes after liftoff.

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