China plans to launch an unmanned space module, Tiangong-1, in 2011, which is expected to accomplish the country's first space docking and regarded as an essential step toward building a space station, an expert said on Wednesday.

Tiangong, or the heavenly palace, would finally be transformed into a manned space lab after experimental dockings with three Shenzhou spacecraft, which are expected to be put into space within two years following the module's launch, said Qi Faren, former chief designer of Shenzhou spaceships.

Qi, a member of the National Committee of the Chinese People's Political Consultative Conference (CPPCC), made the remarks on the sidelines of the annual full session of the top political advisory body that opened Wednesday afternoon.

A spokesman of China's space program said in February last year that the country had planned to launch the unmanned module into orbit as early as the end of 2010. Qi said the delay was due to technical reasons.

Weighing about 8.5 tons, Tiangong-1 is able to perform long-term unattended operation, which will be an essential step toward building a space station.

When transformed into a manned space lab, Tiangong would provide a "safe room" for Chinese astronauts to live in and conduct research in zero gravity, Qi said.

Its scheduled docking with unmanned Shenzhou-8 spacecraft would be the country's first space docking. Scientists on the ground would control the docking between the orbiter and the unmanned spaceship.

Qi said Shenzhou-9 and Shenzhou-10, the two other spaceships to dock with Tiangong-1, would carry two or three astronauts each.

The spaceships would possibly carry seeds from Taiwan for experiments, according to Qi.

Experts say space docking has been widely recognized as one of the most sophisticated space technologies as it requires precise controlling of two high-speed spacecraft which meet and dock in space.

Qi said other key technologies are replenishment of propellant, air, water and food as well as a regenerating life guarantee system for the space module.

Clean propellant elements such as liquid oxygen and kerosene have replaced polluting ingredients in China's space programs, said Qi, also academician of the Chinese Academy of Engineering and the International Academy of Astronautics.

Liang Xiaohong, also a CPPCC National Committee member and Party chief of the China Academy of Launch Vehicle Technology, said Tiangong-1 would be launched on a technologically-modified Long March II-F carrier rocket.

Researchers have made close to 170 technological modifications, including 38 major ones, to the original Long March II-F model, Liang said.

An experimental model of the improved rocket has already been assembled, and would be sent to a satellite launch center for training missions to test its accuracy, reliability and safety capabilities.

In September 2008, China successfully launched its third manned spacecraft Shenzhou-7, following Shenzhou-5 in 2003 and Shenzhou-6 in 2005.