China plans to launch three astronauts into low-Earth orbit on Friday night to exchange crews onboard its Tiangong space station, according to the China Manned Space Agency.

Zhang Jingbo, a spokesman for the agency, said at a news conference on Thursday morning at the Jiuquan Satellite Launch Center in the Inner Mongolia autonomous region in Northwest China, that a Long March 2F carrier rocket is scheduled for lift off from the Jiuquan spaceport at 11:44 pm on Friday.

The rocket will carry the Shenzhou XXI mission crew, headed by Senior Colonel Zhang Lu, toward the Tiangong, which has been manned by their Shenzhou XX peers for more than six months.

The rocket's propellant fueling will begin at its service tower later on Thursday, and other pre-launch preparations are already underway, according to the spokesman, who is also a senior engineer at the space agency.

"After the Shenzhou XXI spacecraft enters its preset orbital position, it will activate the rapid autonomous rendezvous-docking mode and take about three and a half hours to approach and connect with the front port on the Tianhe core module," he said.

The Shenzhou XXI team is tasked with operating and maintaining the Tiangong space station during their six-month flight.

The mission will become the second time for Zhang Lu to fly in space, some 29 months after he returned from the Shenzhou XV flight.

It will be the debut mission for his two crewmates: Major Wu Fei, the Shenzhou XXI's spaceflight engineer, and mission payload specialist Zhang Hongzhang.

Completed in late 2022, the Tiangong is the only operating space station independently run by a single nation, orbiting Earth at an altitude of about 400 kilometers.

The orbital outpost has been manned by the Shenzhou XX astronauts — mission commander Senior Colonel Chen Dong, Colonel Chen Zhongrui and Colonel Wang Jie — since their arrival in late April.

Chen Dong's team is scheduled to fly back to Earth after several days of handover work with their successors, according to Zhang Jingbo.