The science and technology ministry aims to launch the first heavy-lift version of the H-2A in the fiscal year starting in April 2007, said Shigekazu Matsuura at the ministry's space utilisation division.

"The primary purpose for this is to boost cargo transport to the International Space Station," he said.

"The capacity of the current standard model is not sufficient" although Japan will be obliged to ship six tons of cargo every year to the station upon its completion around 2008, he said.

"The higher capacity will also enable the rocket to carry more commercial satellites, thus reducing the launch costs per satellite and increasing competitiveness (of the H-2A)," he said.

The project will raise the H-2A's payload capacity to the level equal to its rivals such as Europe's Ariane rockets, he said.

The development is estimated to cost 20 billion yen, a quarter of which will be shouldered by Mitsubishi Heavy Industries Ltd.

The private firm will design and produce the revamped rocket, while the Japan Aerospace Exploration Agency, the reorganised space agency to be launched in October, will remodel launch facilities.

"The diameter of the rocket's first stage will be increased to five metres (16.5 feet) from four meters for the current standard model so that the new version will have more fuel, and also a second main engine will be added," Matsuura said.

The new H-2A rocket will be able to place a 4,000-kilogramme (8,800-pound) communications satellite into geo-stationary orbit 36,000 kilometresmiles) above the equator, he said.

The production and launching cost of the current version of the H-2A is 8.5 billion yen, compared with 10.5 billion yen for the new heavy-lift version.

By carrying more satellites, however, launch costs per satellite can be brought below current levels.

A ministry panel is expected to give the formal go-ahead for the development plan on August 22 after subcommittee-level approval likely to come on Monday next week, the official said.

Japan has sent up five domestically-developed H-2A rockets, with the latest blast-off in March carrying the nation's first spy satellites.

SPACE.WIRE