The H3 rocket is tracking for a maiden flight toward the end of 2020. MHI conducted hot-firing tests of the rocket's LE-9 first-stage engines early this year. Credit: JAXA

WASHINGTON — The Japanese space agency JAXA announced Sept. 11 that the first launch of the country’s new H3 rocket will be delayed to no earlier than the spring of 2021 because of problems with the rocket’s main engine.

JAXA said that the first flight of the rocket is now scheduled for some time in Japanese fiscal year 2021, which begins April 1 of 2021. The second launch of the rocket has also slipped, to Japanese fiscal year 2022.

JAXA said that engineers had encountered a technical problem with the LE-9 engine used in the rocket’s first stage. The statement did not elaborate in the problem. That engine, which uses liquid oxygen and liquid hydrogen propellants, performed hotfire tests early this year.

“JAXA will deal with the LE-9 engine-related problem in an appropriate manner and make an all-out effort for the successful launch of the H3,” the agency said.

JAXA and Mitsubishi Heavy Industries (MHI), the prime contractor for the H3, has previously targeted an inaugural launch of the rocket by the end of 2020. Ko Ogasawara, MHI vice president and general manager for space systems, affirmed that schedule in March at the Satellite 2020 conference, with the ALOS-3 Earth science satellite as the payload for that mission.

The H3 will succeed the existing H-2A and H-2B rockets, which have been the mainstay of Japan’s space program for nearly two decades. The H3 is designed to be significantly less expensive than the H-2, making it more competitive on the global commercial launch market.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...