The Shenzhou-12 spacecraft, or Divine Vessel, was launched on a Long March-2F carrier rocket Thursday morning, from the Jiuquan Satellite Launch Center in northwest China's Gobi Desert.
They will call the core module of the Tiangong space station home until September, making it the longest crewed space mission in China's history.
The mission includes commander Nie Haisheng, who is a decorated air force pilot in the People's Liberation Army and already has experience in two space missions.
After the Tianhe was launched in April, the rocket that carried it into space made an uncontrolled reentry to Earth, though China dismissed criticism of the potential safety hazard.
The Shenzhou-12 crew are to live on the Tianhe, which means "Harmony of the Heavens", a cylinder 16.6 m (55 ft) long and 4.2 m (14 ft) in diameter.
The first crew will test and maintain the systems onboard, conduct spacewalks and undertake scientific experiments. Nie will command the mission and make his third journey into space.
"This mission is more arduous and the challenges are greater".
Three astronauts have docked with part of China's new space station.
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In 2016, two male astronauts - Chen Dong and Jing Haipeng - were sent via the Shenzhou-11 spacecraft to Tiangong-2, a prototype of the space station where they later stayed for about a month.
Liu, with the help of another astronaut, used a crowbar to pry open the hatch after it refused to budge.
Crew member Tang Hongbo said in a separate interview with state broadcaster CCTV that he had taken videos of everyday life with his son and wife to watch on the space station. "The mission has thus become extremely complex and tough".
Comprehensive cooperation and communication on spacecraft technology, space experimentation and astronaut selection and training have already taken place between China and several countries including Russia, Germany and Italy, as well as global organizations such as the United Nations Office for Outer Space Affairs and the European Space Agency.
China's building its own station, due to be complete by the end of 2022.
Hao Chun, director of the China Manned Space Agency, said in April that more than 20 cabinets aboard the space station will be reserved for scientific instruments designed in accordance with worldwide standards, adding that these will be available for global cooperation.
"After the completion of the Chinese space station, in the near future, we will see both Chinese and foreign astronauts jointly participate in the flight of the Chinese space station", said Ji Qiming, assistant director at the China Manned Space Agency, told reporters in Jiuquan.
"We're willing to carry out more extensive global exchanges and cooperation with other countries on the issue of debris from spacecraft and in space", Ji said.