JAXA Reports No Problems in H3 Engine Firing Test; Latest Rocket, Unlike Others, Has No Boosters

The Yomiuri Shimbun

16:27 JST, July 24, 2025

An engine firing test for the new mainstay H3 rocket was conducted without any major problems at the Tanegashima Space Center in Kagoshima Prefecture on Thursday, the Japan Aerospace Exploration Agency said.

The test involved a new type of H3 without rocket boosters and is part of a process that aims to reduce the cost of launches to ¥5 billion, half the price of the previous mainstay H2A’s launches. The firing test, which marked the final stage of this process, finished without any significant problems.

JAXA and Mitsubishi Heavy Industries, Ltd. have jointly developed the H3. Thursday’s test involved the sixth H3 rocket, which is a Type 30 test vehicle that has three main engines and no boosters. The three main engines were fired for 25 seconds while the rocket remained attached to the launchpad. JAXA will check acceleration, temperature and other data collected during the test.

Successfully launched H3 rockets have so far had two main engines and two boosters. The H2A rocket that was retired last month had either two or four boosters, but none of the H2A rockets was boosterless.

If JAXA confirms the rocket performed as expected during the firing test, it will be scheduled to blast off carrying dummy satellites and other cargo before the end of fiscal 2025, which runs through March 2026. Later H3 rockets are scheduled to launch satellites including the government’s information-gathering satellites from fiscal 2026 onward.