Factbox: Timeline of China's manned space program

BEIJING, April 29 (Xinhua) -- China launched on Thursday the Tianhe core module of its space station, a key mission in the third step of the country's manned space program.

Here are some key facts of China's manned space program, which started in 1992 with a three-step strategy.

FIRST STEP

The first step was to send astronauts into space and bring them back safely.

The country's first experimental manned spacecraft, Shenzhou-1, was launched with no crew in November 1999, heralding the beginning of China's foray into manned space exploration.

The main goal of the Shenzhou-1 launch was to examine the performance and reliability of the launch vehicle, a Long March-2F carrier rocket, and evaluate key space exploration technology.

In January 2001, Shenzhou-2 was launched, conducting experiments in the areas of materials science, astronomy and physics in a microgravity environment.

Shenzhou-3, launched in March 2002, carried human physical monitoring sensors and "dummy astronauts." It was also equipped with escape and emergency rescue functions.

Nine months later, Shenzhou-4 was launched, featuring radiation-proof facilities and manual emergency rescue systems, despite the fact that the vessel was unmanned.

The launch of Shenzhou-5 in October 2003 was another milestone for China's manned space program, as the mission successfully sent astronaut Yang Liwei into space, making China the third country to send a man into space after the Soviet Union and the United States.

In October 2005, China sent two astronauts into space aboard Shenzhou-6. The astronauts carried out scientific and medical experiments onboard the craft.

SECOND STEP

The second step was developing advanced space flight techniques and technologies including extra-vehicular activity and orbital docking. This phase included the launch of Tiangong-1, a transitional platform to test the docking technology, and the Tiangong-2 space lab.

In September 2008, China achieved its first spacewalk for 19 minutes and 35 seconds, conducted by astronaut Zhai Zhigang, with the launch of Shenzhou-7. China thus became the third country in the world to conduct extravehicular activity in space, following the Soviet Union and the United States.

In September 2011, China launched its experimental space lab, Tiangong-1. The main task of the Tiangong-1 was to test the technologies in rendezvous and docking between spacecraft, and to accumulate experience for developing a space station.

About one month later after the launch of Tiangong-1, China sent Shenzhou-8 into orbit with no crew. In November 2011, Tiangong-1 and Shenzhou-8 accomplished the country's first automatic rendezvous and docking at a height of 343 km above Earth.

In June 2012, the Shenzhou-9 spacecraft was thrust into space to dock with the orbiting Tiangong-1. This was China's first manned rendezvous and docking mission. Two docking tests, one automated and one manual, were accomplished between Shenzhou-9 and Tiangong-1.

Launched in June 2013, Shenzhou-10 docked with Tiangong-1 twice, once through automatic operation and the other manually, aiming to further test technologies designed for docking and supporting astronauts' stay in space. Three astronauts spent 12 days in Tiangong-1, where they conducted space medical experiments and technical tests.

In September 2016, China launched Tiangong-2, an improved version of Tiangong-1 that is considered China's first space lab.

About one month after the launch of Tiangong-2, China successfully launched the manned spacecraft Shenzhou-11 carrying two astronauts who would stay in space for 33 days, the longest mission in the country's manned space program to date. On October 19, 2016, Tiangong-2 and Shenzhou-11 completed an automated docking in orbit.

In April 2017, Tianzhou-1, China's first cargo spacecraft, successfully conducted automated docking with the orbiting Tiangong-2 and then carried out their first in-orbit refueling. Another two dockings and two further refuelings were completed later.

THIRD STEP

The third step is to assemble and operate a permanent manned space station.

In May 2020, China's new large carrier rocket Long March-5B made its maiden flight. Long March-5B is mainly used to launch the modules of China's space station, and the successful flight inaugurated the "third step" of China's manned space program.

On Thursday, China sent into space the core module of its space station, kicking off a series of key launch missions that aim to complete the construction of the station by the end of next year.

China will also send the Tianzhou-2 cargo spacecraft and Shenzhou-12 manned craft this year to dock with the core module, Tianhe. Three astronauts will reach the core module aboard Shenzhou-12 and stay in orbit for three months.

Tianzhou-3 cargo craft and Shenzhou-13 manned spaceship will also be launched later this year to dock with Tianhe, and another three astronauts will then begin their six-month stay in orbit.

After the five launch missions this year, China plans six missions, including the launch of the Wentian and Mengtian lab modules, two cargo spacecraft and two manned spaceships, in 2022 to complete the construction of the space station.