Interpret failures and development tests

Epsilon-6 launched on October 12, 2022 carrying the third innovative-satellite demonstration mission and QPS-SAR spacecraft. JAXA’s initial account described an attitude deviation at the second-to-third-stage separation decision, followed by a determination that orbit could not be reached and a flight-termination command. The launch failed.

That first announcement also opened an investigation. It documents the observed sequence without itself providing a final root-cause conclusion. Do not replace that distinction with an invented connection to a different motor test just because both events belong to the Epsilon family.

Epsilon S development encountered second-stage motor explosions during ground firings in July 2023 and November 2024. These were tests at a ground facility, not additional orbital launch attempts. The November 2024 investigation announcement explicitly distinguishes this development work from the planned vehicle flight.

On July 23, 2026, JAXA conducted a ground firing of the M-35a second-stage motor. Its next-day report said the test ended normally and further data analysis would follow. This supports a bounded test result; it does not by itself establish a completed Epsilon S orbital mission or a guaranteed date for one.

Interpret a test without overstating the result

The July 2026 preliminary table lists a 129.9-second burn against a 127.9-second prediction. Subtracting gives a 2.0-second difference, about 1.6 percent of the prediction. It also lists 355.3 kN maximum thrust against 358.2 kN predicted. The measured maximum is 2.9 kN lower.

A difference from a prediction is not automatically a violation of an acceptance criterion. The table does not provide every tolerance or the full thrust history. In particular, multiplying maximum thrust by burn time assumes the maximum was sustained throughout the burn; that does not give a defensible total impulse without additional data. Test interpretation needs requirements, measurement definitions and analysis.