If you’ve been in the space business long enough, you learn that there are many ways a rocket can go wrong. I wrote an article about Rocket’s cheating and the extensive investigations that usually take place.—But not always—Find out what went wrong.

But I never expected to write this story. Perhaps this was a failure of my own imagination. I’m used to writing about engine failures, staging problems, guidance failures, and structural defects. Last April, Ars A strange failure was reported Photo of Firefly Aerospace’s commercial Alpha rocket.

Japan’s H3 rocket discovered a new way to fail last month, but it apparently had escaped the imagination of the country’s designers and engineers.

The H3 is a relatively new rocket, and last month’s launch marked the eighth flight for Japan’s flagship rocket. Launchers fall into the medium to heavy section of the lift spectrum. The No. 8 H3 rocket launched from Tanegashima in southern Japan on December 22 local time, carrying a navigation satellite weighing approximately 5 tons into space.

This rocket was scheduled to place the Michibiki 5 satellite into an orbit more than 20,000 miles above Earth. All was well until H3, about four minutes into flight, ejected its payload fairing, a two-piece clamshell that covers the satellite during liftoff.

Officials at the Japan Aerospace Exploration Agency (JAXA) are beginning to understand what happened. Space agency officials last week briefed the government ministry that oversees Japan’s space activities. The presentation (in Japanese) was as follows. Published on government website.

This presentation is rich in information, including illustrations, fault tree analysis, and graphs of in-flight measurements from the H3 rocket’s sensors. This provides a treasure trove of details and data that most launch providers refuse to release publicly after a rocket failure.

On December 22, 2025, Japan’s No. 8 H3 rocket takes off from the Tanegashima Space Center along with the navigation satellite Michibiki 5.

Credit: JAXA

what happened?

Some of the content may be difficult to understand for foreigners not familiar with the subtle intricacies of the H3 rocket design. What is clear is that something went wrong when the rocket released its payload shroud. Video returned from the rocket’s onboard camera showed a shower of debris surrounding the satellite, and the satellite began to wobble and tilt shortly after the fairing separated. Sensors also detected a sudden acceleration around the attachment point that connects the spacecraft to the top of the H3 rocket.