The rocket carrying the Docking Tiangong-1 space lab arrives at the launch pad at the Jiuquan Satellite Launch Center on September 20. Photo: Agencies

A rocket carrying China's first space lab module will blast off this evening from the Jiuquan Satellite Launch Center, representing a milestone for the country's space program that brings it a step closer to its goal of building a space station by 2020.

The Long March-2FT1 rocket has been fueled and is set to take off between 9:16 and 9:31 pm, carrying the space experiment platform Tiangong-1, or "Heavenly Palace 1," Wu Ping, a spokesperson with China's manned space program, told reporters on Wednesday.

The rocket was made more powerful by receiving more than 170 improvements after an unsuccessful launch in August when a Long March-2C rocket failed to send an experimental satellite into orbit, Wu said.

"Despite the failure in August, China remains full of confidence and anticipation in the launch of Tiangong-1," Wu said, adding that the country has successfully conducted 94.4 percent of its nearly 130 space launches.

The 8.5-ton Tiangong-1 is cylindrical in shape with two docking ports and a two-module space lab that can accommodate three astronauts, the Xinhua News Agency reported.

During its two-year service life, its main mission will be to conduct a series of rendezvous and docking experiments with the Shenzhou-8, -9 and -10 spacecrafts that will be launched later.

"Without rendezvous and docking, you really cannot run an advanced space program. You're confined to launching small spacecraft that just operate by themselves," Morris Jones, a space analyst based in Sydney, told Reuters.

"Tiangong-1 is the preliminary step toward building our space station. Mastering rendezvous and docking will lay the ground for China's future space exploration, but the experiments will be very challenging," Pang Zhihao, a Beijing-based space technology expert, told the Global Times.

According to Pang, since 1966, there have been 300 space dockings conducted by foreign astronauts, 17 of which have failed, including two last year by Russian cosmonauts.

Wu said on Wednesday that the Shenzhou-8 is scheduled to be launched one month later, and within two days of it reaching its orbit, the first docking test will be conducted.

According to Wu, the Tiangong-1 will first drop from its 350-kilometer-high orbit to a 343-kilometer-high orbit to rendezvous with the Shenzhou-8. After docking, the two will fly together for about 12 days and will conduct another docking at an appropriate time.

"The Shenzhou-8 will return to earth after tests and the Tiangong-1 will rise to its original orbit, waiting for the following docking tests with Shenzhou-9 and -10," Wu added.

According to official accounts, the Shenzhou-10 will carry a Chinese astronaut who will test manual space docking with the Tiangong-1, and before 2016, China will try to send Tiangong-2 and Tiangong-3 into orbit.

A source inside the aerospace industry told the Global Times that apart from the docking test, labs on Tiangong-2 and -3 will also be used to test water and oxygen recycling technologies required for staying in outer space.

"Water and oxygen consumed in previous Shenzhou spacecrafts were all carried from earth. To support long-term stay in orbit, future Chinese space labs and space stations should be capable of recycling water and oxygen by themselves," the insider said.

China's ultimate goal is to build a space station around 2020, roughly the same year the International Space Station will end its life cycle.

Pang said if China can reach its goal by 2020, it would probably be the only space station in the world by that time.

"China did not take part in missions on the current space station because it was not involved in the construction process of the project, but that will not affect China's future search for international cooperation in space exploration," Pang said.

Pang's remarks echoed those of Wu, who said on Wednesday that the space station would positively contribute to mankind's exploration and peaceful use of space through broad international cooperation.

Ministry of Defense spokesman Geng Yansheng also reiterated on Wednesday that China's exploration of outer space was for peaceful purposes, and Beijing was firmly opposed to the weaponization of space exploration programs.

Regarding Western reports that the Tiangong-1 also has military purposes, Geng said, "The military enjoys unique advantages in organizing and coordinating such large-scale activities, and its involvement in aerospace missions is an international practice."

Johnson-Freese told Reuters that Tiangong is not going to immediately or directly provide China any military capabilities.

"With most space technology dual-use – of value to both civil and military communities – anything done by China in space will have spillover to the military, much the same as NASA's technical advancements do in the US," Johnson-Freese said.