On November 26, 2023, an engine combustion test for the Epsilon S rocket at the Tanegashima Space Center in Kagoshima Prefecture was abruptly stopped due to an explosion. Live broadcasts from the Japan Aerospace Exploration Agency (JAXA) depicted a significant fireball and smoke emerging from the site, while the exact reason for the failure remains unidentified. Fortunately, there were no casualties reported.

The test was initially intended to assess the upgraded features of the Epsilon S, which included enhancements to its second-stage motor, increasing propellant capacity from 15 tons to 18 tons. The test commenced at 8:30 a.m., and just 49 seconds into the ground testing, a loud boom was heard, leading to the ignition of a fireball accompanied by thick white smoke.

This incident is not isolated, as a previous test in July 2022 resulted in an explosion during an Epsilon rocket assessment at the Noshiro Rocket Testing Center in Akita Prefecture, causing the destruction of the facility. Investigations pinpointed that elevated temperatures had melted some components, undermining the motor's integrity and igniting the propellant. To prevent a recurrence of such issues, engineers had insulated the components with a specialized material for the latest test, which was meant to pave the way for a subsequent Epsilon rocket launch this fiscal year; however, the recent incident casts doubt on this timeline.