Japan’s new H3 rocket ready for another launch attempt after last-second abort

Japan’s H3 rocket rolls out to its launch pad at the Tanegashima Space Center before a second launch attempt March 6 (U.S. time). Credit: JAXA

After an electrical problem kept Japan’s first H3 rocket on the ground during a launch attempt last month, teams wheeled the new hydrogen-fueled launcher back to its firing stand for another countdown Monday to try to send an Earth observation satellite into orbit.

The 187-foot-tall (57-meter) H3 rocket rolled out of the Vehicle Assembly Building at the Tanegashima Space Center on the eve of another launch attempt Monday. The two-stage rocket, fitted with two strap-on solid rocket boosters for extra thrust, moved into position on Launch Pad No. 2 at Tanegashima, a spaceport overlooking the Pacific Ocean on the southwestern end of the Japanese island chain.

Launch engineers plan to load cryogenic liquid hydrogen and liquid oxygen into the expendable rocket in the hours before liftoff. Covered in orange foam insulation to protect its super-cold propellant tanks, the H3 has a six-minute, 20-second launch window opening at 8:37:55 p.m. EST Monday (0137:55 GMT Tuesday), or 10:37 a.m. Japan Standard Time.

The rocket’s first countdown Feb. 16 (U.S. time) ended just before liftoff. The computer overseeing the final stages of the countdown called an abort after ignition of the rocket’s two LE-9 core stage engines, which flashed to life as expected in the final seconds before launch. The two solid rocket boosters were supposed to ignite when the countdown clock hit zero, driving the H3 off its launch pad to begin the rocket’s inaugural test flight.

Japanese ground crews rolled the rocket back to its assembly building for troubleshooting. The investigation found the last-second abort was caused by a problem in the first stage flight control system.

In a statement, the Japan Aerospace Exploration Agency, or JAXA, said engineers determined that the first stage vehicle control computer malfunctioned due to a voltage transient as the controller switched from external power to internal power, a transition that occurs a split-second before the ground power umbilical separates from the rocket at the launch pad.

The electrical problem appeared during a fast-paced sequence of final checks before the H3 rocket sends the command to ignite the two solid rocket boosters, an irreversible event that commits the launcher to liftoff. Engineers from JAXA and the rocket’s industrial team, led by Mitsubishi Heavy Industries, made fine adjustments to the exact timing of the first stage vehicle controller’s switch to internal power to avoid the same problem on the upcoming launch attempt.

With those corrective actions in place, JAXA last week set a new launch date of Sunday night (U.S. time) for the H3 test flight. Officials later delayed the mission 24 hours due to a forecast bad weather.

A view of the H3 rocket inside the Vehicle Assembly Building at the Tanegashima Space Center. Credit: JAXA

Japan’s space agency started development of the H3 rocket in 2013, with a goal of slashing in half the cost per launch of Japan’s workhorse 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.

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.

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.

If all goes according to plan, the 187-foot-tall 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 Advanced Land Observing Satellite 3, or ALOS 3, spacecraft in a clean room prior to integration with its H3 launcher. Credit: JAXA

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.

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 three-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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