Japan’s first H3 rocket, nearly a decade in development, was moments from liftoff Thursday (U.S. time) when the launch vehicle detected a problem and cut off the countdown just before sending a command to ignite two strap-on solid-fueled boosters.
The H3 rocket’s two hydrogen-fueled main engines ignited about 6.3 seconds before liftoff, sending a plume of exhaust out of the flame trench at the Tanegashima Space Center in southwestern Japan. But the H3’s dual solid rocket boosters did not light when the countdown clock struck zero.
“During the automatic countdown sequence of the rocket, the first stage vehicle system detected an abnormality and did not send out the solid rocket booster (SRB-3) ignition signal, so today’s launch was canceled,” the Japan Aerospace Exploration Agency said in a statement.
JAXA officials did not provide any more details on the problem that prevented the 187-foot-tall (57-meter) H3 rocket from taking off Thursday at 8:37 p.m. EST (0137 GMT Friday). The launch team began preparations to drain cryogenic liquid hydrogen and liquid oxygen from the two-stage rocket as engineers analyzed data to find the cause of the abort.
The H3 rocket’s countdown was running on a computer-controlled sequencer, which checks numerous parameters in the final moments before launch to ensure engines, avionics, and other systems are ready for liftoff.
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JAXA did not set a new target launch date for the inaugural flight of the H3 rocket, which will replace Japan’s workhorse H-2A rocket and the already-retired H-2B launch vehicle.
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, which has been in service since 2001. 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 will have 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.
And the H3’s upper stage has a single LE-5B-3 hydrogen-fueled engine capable of multiple firings in space. It’s a modernized version of the LE-5B engine flown on the H-2A rocket.
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.
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, will fly 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 the launch attempt this month. Thursday’s countdown was the first time an H3 countdown proceeded with the solid rocket boosters attached to the core stage.
The H3 rocket will 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.
MHI and JAXA 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. 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.
When it lifts off, the first H3 rocket will initially head east from Tanegashima to place a Japanese Earth observation satellite into orbit for the Japan Aerospace Exploration Agency. The Advanced Land Observing Satellite 3, or ALOS 3, mission will collect wide-swath, high-resolution images of land surfaces around the world, providing observations for disaster management, mapping, and environmental monitoring.
The two LE-9 engines and twin strap-on boosters will generate 1.6 million pounds of thrust at full power, accelerating the H3 launcher into the sky over Tanegashima.
The two solid rocket boosters will burn out and jettison to fall into the Pacific at T+plus 1 minute and 56 seconds. The payload fairing on top of the rocket will release in a clamshell-like fashion at T+plus 3 minutes and 34 seconds, revealing the ALOS 3 spacecraft once it is out of the discernible atmosphere.
After turning onto a more southerly course, the main stage of the H3 rocket will shut down its two engines at T+plus 4 minutes and 58 seconds, followed by stage separation seven seconds later. Ignition of the upper stage LE-5B-3 engine is expected at T+plus 5 minutes and 17 seconds.
The upper stage will burn more than 11 minutes before releasing the more than 6,000-pound (3-ton) ALOS 3 spacecraft at T+plus 16 minutes and 57 seconds at an altitude of about 420 miles (675 kilometers). ALOS 3 will unfurl its solar arrays to begin a seven-year Earth observation mission.
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