The first flight of the H3 rocket had been postponed for a year from the launch date initially scheduled for some time in fiscal 2020 ended March last year.


But the discovery of defects forced the Japan Aerospace Exploration Agency to delay it a second time as it remains unclear by when the vehicle’s engine can be redesigned and produced, according to the sources.


Some people in the government expressed concerns over the postponement being potentially prolonged, the sources said.


The rocket, which has the highest launch capability to the geostationary transfer orbit, has been under development to succeed the country’s existing H2A and H2B launch vehicles so that Japan can maintain its autonomous access to space in terms of launching satellites and probes, according to JAXA.


By utilizing the 63-meter-long rocket with a diameter of 5.2 meters, Japan’s satellite launching capacity is expected to rise over 1.3 times than when it used the H2A rocket.


In the future, the H3 rocket is expected to carry a cargo transporter, HTV-X, which will deliver supply goods and materials to a lunar-orbiting outpost in a U.S.-led space program.


Against the background of the rapid emergence of new technologies overseas, including those for reusable rockets, JAXA and its prime contractor Mitsubishi Heavy Industries Ltd., among others, has been on board from the development stage, leveraging their expertise to produce the new rocket.


The H3 launch vehicle aims at high flexibility, high reliability, and a high cost-performance ratio, the space agency said.


The first unit of H3 is planned to carry the Advanced Land Observing Satellite-3, designed for an improved ground resolution with a large field of view and expected to become a key tool for the government’s disaster management.


Also aboard ALOS-3 will be the Defense Ministry’s demonstration sensor, capable of detecting missiles and other projectiles.


In May 2020, a test conducted on the H3 rocket’s main engine found holes on the wall of a combustion chamber and a crack on a turbine that feeds fuel to the chamber, prompting the agency to announce the first delay.


Since then, JAXA has reviewed its design and has been reassembling the rocket at Tanegashima Space Center in Kagoshima Prefecture, where the rocket is planned to lift off.