notablelaunch2026-07-23

JAXA completes Epsilon S second-stage engine test after switching to backup motor

JAXA's Epsilon S clears its second-stage engine test, using a fallback motor after two prior explosions grounded the program.

// sources · 2 attached

what happened

JAXA fired the M-35a second-stage engine for its Epsilon S small-satellite rocket for about two minutes at Tanegashima Space Center on July 23, per Xinhua and Nikkei Asia. JAXA switched to the older, proven M-35a design, adapted from an earlier Epsilon-series motor, after the newer E-21 engine exploded during ground tests in July 2023 and November 2024. The switch cuts the rocket's payload capacity to sun-synchronous orbit from 600 kg to 400 kg, and JAXA is targeting a first flight within the current Japanese fiscal year.

why it matters

The successful static fire clears a key hurdle toward Epsilon S's first flight after nearly two years of setbacks, restoring a dedicated Japanese small-satellite launch option. The reduced payload capacity narrows the vehicle's competitive window against other smallsat launchers before it has even flown its first mission.