China will launch its unmanned spacecraft Shenzhou-8 early Tuesday for the country's first space docking, a major step closer to the goal of building a permanent space station around 2020.

Shenzhou-8 will take off at 5:58 a.m. Tuesday, carried by a modified model of the Long March CZ-2F rocket at Jiuquan Satellite Launch Center in northwest China, said Wu Ping, spokeswoman of China's manned space program.

The spacecraft is due to couple with Tiangong-1, or "Heavenly Palace," China's first space lab module within two days after the launch for the country's first docking. Tiangong-1 was sent into space on Sept. 29.

They will separate after flying together for 12 days but will carry out a second docking later, she added.

The mission, if successful, will make China the third nation to master the technology after the United States and Russia, paving the way for the nation to place a space station into orbit around 2020.

Ready for blast off

Fuel was injected into the modified Long March CZ-2F rocket at 10 a.m. on Monday, Wu said. Technical conditions of all systems are normal, interfaces of different systems are coordinated, ground tests are adequate, contingency plans are ready and all facilities are sound, which meet requirements for a launch, she added.

The launch vehicle is the latest updated model of the Long March-2F rocket, she said. The rocket, 58.3 meters long, has a liftoff weight of 497 tonnes and a payload capacity of 8.13 tonnes.

The target vessel Tiangong-1 completed a 180-degree turn-around to prepare itself for the upcoming docking at 7:34 p.m. Sunday under the control of the Beijing Aerospace Flight Control Center, said Chen Hongmin, director of the command center for the Chinese space program on Sunday.

He said the spacecraft was lowered to the 343-km-high rendezvous and docking orbit on Sunday after a series of maneuvers including orbit control and on-orbit testing during one-month orbits.

"Equipments and technical conditions of Tiangong-1 have met requirements for docking," Wu said.

To ensure the success of the mission, Chinese space engineers have made "considerable modifications" on Shenzhou-8 to previous versions of China's unmanned spacecraft.

Shenzhou-8, with a length of 9 meters and a maximum diameter of 2.8 meters, has a liftoff weight of 8.082 tonnes.

"More than half of the 600 or so sets of equipment have been modified technically, while newly designed devices account for about 15 percent of the total," Wu said.

The modifications were mainly aimed at arming the spacecraft with automatic and manual rendezvous and docking capacities, and to enhance the vehicle's performance, safety and reliability, according to Wu.

"After the improvements, the spacecraft will be able to connect with the target spacecraft Tiangong-1 for 180 days," Wu said.