Jumbo rocket design poses challenges

Development of Long March-11 to boost ability to enter space

Problems in the development of China's largest rocket have delayed its launch, probably until 2015, said a senior official working on the launch vehicle's design.

The Long March-5 was initially due to be launched next year.

"Our plan has encountered some difficulties," said Liang Xiaohong, deputy head of the China Academy of Launch Vehicle Technology, referring to three failed experiments recently.

The main difficulty lies in the rocket's structural elements, said Liang, who is also a member of the National Committee of the 12th Chinese People's Political Consultative Conference.

Though China's Long March rockets have recorded more than 100 successful launches, the Long March-5 is a new challenge due to its larger size - a diameter of 5 meters, instead of the 3.35 meters of all previous launch vehicles.

The larger design enables the Long March-5 to send heavy satellites and space station components into orbit, and it has six vehicle configurations planned for different missions.

"But when an object is bigger, its technical risks and functional defects are also magnified," Liang said.

The increased size has challenged the mechanical machining capabilities of Chinese manufacturers, who have never produced rocket parts as big before and lack the necessary equipment and technology, he added.

"The Long March-5 project has reached the basic industry's ceiling," Liang said.

Also, the potential risks of a larger launch vehicle in space are unknown, and the designers must gauge these for six configurations of the craft instead of one, he said.

Failure to solve the problem has prompted the academy to push manufacturers to improve their level of mechanical machining.

However, next year will still see the debut of Long March-7, which is designed to send China's cargo spaceship to dock with a future space station.

The Long March-7 carrier rocket has a takeoff thrust of 700 metric tons, the second-largest after Long March-5 with 1,000 tons.