H3 reaches orbit on second launch

WASHINGTON — Japan’s H3 rocket successfully reached orbit on its second launch Feb. 16, nearly a year after its inaugural launch failed.

The H3 rocket lifted off from the Tanegashima Space Center at 7:22 p.m. Eastern after a two-day delay caused by weather. There were no issues reported during the countdown, with liftoff occurring at the beginning of a window lasting more than two and a half hours.

A key point in the launch was the separation of the upper stage and ignition of its LE-5B-3 engine. On the vehicle’s inaugural launch in March 2023, that engine failed to ignite, forcing controllers to issue a destruct command to destroy the stage and its payload, the ALOS-3 Earth observation satellite.

On this launch, designated H3 Test Flight 2 (H3TF2) by the Japanese space agency JAXA, the engine did ignite. The stage reached a preliminary orbit of about 674 kilometers 16 and a half minutes after liftoff, and moments later deployed one of its payloads, the CE-SAT-1E imaging satellite built by Canon Electronics. It was scheduled to be followed about nine minutes later by the other secondary payload, a cubesat called TIRSAT.

A second burn of the upper stage was planned one hour and 47 minutes after liftoff, lasting 26 seconds. After that, the upper stage would deploy its primary payload, a mass simulator called Vehicle Evaluation Payload (VEP) 4. VEP-4 is a metallic column with the same mass and center of gravity as ALOS-3. JAXA flew the inert payload after criticism about flying ALOS-3, a $200 million satellite, on the rocket’s first launch.

JAXA and the vehicle’s prime contractor, Mitsubishi Heavy Industries, spent months investigating the inaugural launch failure. Engineers concluded that while the rocket received the signal to ignite the engine, an electrical failure prevented the ignition system from starting up.

While the investigation did not identify a single root cause, it did find three scenarios that most likely explained what happened: a short-circuit in wiring in the ignition system, a failed transistor in the ignition system and a failure in one computer in the stage’s control system that sent electrical current to a redundant computer that caused it to fail. JAXA made changes to prevent any of those scenarios from reoccurring.

The potential problems with the ignition system also affected the older H-2A rocket, which uses a version of the same upper-stage engine. That grounded the H-2A for half a year, with the rocket returning to flight in September.

The H3 is key to Japan’s future space plans. The rocket will succeed the H-2A and launch civil and military missions, including the new HTV-X spacecraft that will transport cargo to the International Space Station. The H3 is also designed to operate at far lower costs than the H-2A, making the vehicle more competitive in the commercial launch market.

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