Japanese rocket part came unglued, leading to mission failure
Tiny variation in temperature weakened a component and when a critical moment arrived, that mattered
Japan’s space exploration agency (JAXA) thinks a manufacturing process that didn’t properly take into account the qualities of an adhesive caused the December 2025 failure of a satellite launch using its locally developed H3 rocket.
As The Register reported at the time, the H3’s second stage ignited late and shut down early, leading JAXA to abort the mission. The navigation satellite aboard the mission was lost.
Analyses of the mission presented to Japan’s Ministry of Education, Culture, Sports, Science and Technology yesterday suggest the cause of the mess was the manufacturing process used to create a component that held the satellite payload in place.
Temperatures during manufacturing became hotter than expected, which weakened the adhesive used to connect layers of the component.
When the H3’s fairing opened, that weakness meant the component delaminated and became unable to support the weight of the satellite – which therefore moved in unexpected ways. One result of that movement was to break a fuel pipe to the second stage, which explains the later-than-expected ignition.
The rest is history.
JAXA thinks the problem only became apparent on this mission because the payload was unusually heavy. The agency has vowed to revisit the manufacturing processes and perhaps change the design of the H3 to avoid future problems of this sort.
The analysis is a reminder of the incredibly complex engineering needed to conduct space missions, and how even seemingly tiny mistakes can have colossal consequences. JAXA’s report [PDF] on the incident refers to many sources of telemetry the rocket produces, and points out tiny momentary anomalies that represent evidence for the theory about the adhesive issues.
The H3 is Japan’s next-generation medium-capacity launcher. JAXA hopes it will become a mainstay of its commercial launch program and also propel its scientific missions into space.
The space agency has chalked up many extraordinary successes, among them returning samples gathered from two asteroids, and numerous missions to the International Space Station. ®