Japan’s Flagship H3 Rocket Suffers Engine Bust, Fails to Deliver Satellite

Japan’s H3 rocket lifted off for its seventh mission on Sunday, but an engine failure foiled its attempt to insert a navigation satellite in geostationary orbit.

Japan Aerospace Exploration Agency (JAXA) revealed that its flagship rocket’s second-stage engine suffered an anomaly shortly after launch, causing it to shut down prematurely. The rocket was carrying the Michibiki 5 satellite, part of Japan’s regional navigation satellite system in geosynchronous orbit.

The space agency has already set up a special task force headed by JAXA president Hiroshi Yamakawa and “started investigations to find out the cause,” it wrote in a statement.

Japan’s H3 rocket suffered an anomaly during its inaugural launch in 2023, also due to an issue with its second stage. The recent engine failure is a major setback for Japan’s space program, casting uncertainty over several H3 launches scheduled for the coming year.

Failure to launch

The H3 rocket launched on Sunday at 8:51 p.m. ET from the Tanegashima Space Center, located on a southwestern Japanese island. The rocket’s second-stage engine burn failed to ignite on time, resulting in an unplanned shutdown. The onboard satellite, also known as QSZ-5, did not reach its designated orbit and was reportedly lost.

During a press conference, JAXA stated that telemetry data showed pressure in the second stage’s hydrogen tank began dropping during the first stage engine burn. As a result, the first stage engine cutoff took place 27 seconds later than planned, delaying the second ignition by 15 seconds. It’s not yet clear if the satellite separated from the rocket.

The launch of the QSZ-5 satellite was originally planned for December 17 but was delayed “because an uncertain incident was found in the cooling water injection equipment,” JAXA wrote in a statement on Friday.

The 207-foot-tall (63-meter) rocket is due to launch another QSZ satellite in 2026, as well as Japan’s HTV-X cargo spacecraft. Japan’s Martian Moons eXploration (MMX) mission is also scheduled to launch on board the H3 rocket in late 2026.

Japan’s H3 rocket was 11 years in the making, a successor to the H-2A, which the agency retired in June. The expendable rocket had a rocky start, forcing a dreaded self-destruct command just 15 minutes after its inaugural launch on March 6, 2023. Although the rocket’s first stage worked as planned, an electrical glitch caused the second stage to fail to ignite. The failure resulted in the loss of the $200 million ALOS-3 advanced Earth-observing satellite.

Since its failed first launch, however, H3 has pulled off five successful missions to date. Still, the latest engine failure puts a wrench in Japan’s spaceflight plans, with JAXA aiming for at least two H3 launches per year. The scheduled launches for 2026 now appear to be in limbo, pending the results of the investigation.