JAXA was developing this engine, the responsibility for which was planned to eventually be turned over to the Galaxy Express venture.

In late December 2007, The Yomiuri Shimbun newspaper reported that the GX program was being subjected to a thorough review, mainly because of unexpectedly high additional costs.

It was originally designed to use an Atlas III first stage, and to be launched from Tanegashima in Japan, however this was abandoned in 2009[citation needed] in favour of the CCB configuration.

In November 2009, the Japanese Government Administration Reform Committee recommended that funding for the second-stage engine be halted.

[3][4] Galaxy Express Corporation (株式会社ギャラクシーエクスプレス, Kabushikigaisha Gyarakushīekusupuresu) (GALEX) was a Japanese company which intended to develop the GX rocket.