China launched its Wentian space laboratory on Sunday afternoon, sending the country's largest-ever spacecraft to Earth's orbit to become part of the Tiangong space station. [Photo by Zhu Xingxin/chinadaily.com.cn]

China launched its Wentian space laboratory on Sunday afternoon, sending the country's largest-ever spacecraft to Earth's orbit to become part of the Tiangong space station.

Encased in a 20.5-meter-long payload fairing, the space lab was carried by a Long March 5B rocket that blasted off at 2:22 pm from a coastal service tower in the Wenchang Space Launch Center in Hainan province.

After an eight-minute flight, the rocket placed the craft into a low-Earth orbit nearly 400 kilometers above the ground in which Tiangong is travelling.

In the next couple of hours, the Wentian will rendezvous and then dock with the Tiangong station's Tianhe core module, according to the China Manned Space Agency.

After that, the Shenzhou XIV mission crew now flying with Tiangong — mission commander Senior Colonel Chen Dong, Senior Colonel Liu Yang and Senior Colonel Cai Xuzhe — will enter the lab module to check its condition and internal equipment, it said.

In coming weeks, Wentian will be repositioned by a robotic apparatus from the forward docking port to a lateral port, where it will remain and be prepared for long-term operation, the agency noted.

To prepare for the Wentian's arrival, the Tianzhou 3 cargo spacecraft departed from the Tiangong station on July 17 to leave its docking hatch for the coming lab. The cargo ship, which was launched in September and had remained connected to Tiangong since then, will be guided by ground controllers to fall back to Earth in due course.

Currently, Tiangong consists of the Tianhe module, the Tianzhou 4 cargo ship and the Shenzhou XIV spacecraft.

Assembled at a manufacturing and testing complex in the northern coastal municipality of Tianjin, Wentian was transported by ship and arrived in Wenchang in late April. It underwent function and prelaunch checks over the past three months at the launch center.

The first lab component of the Tiangong station, Wentian features cutting-edge technologies, strong capabilities, sophisticated design and represents a new milestone in China's space industry. It incorporates the wisdom, dedication and hard work of numerous scientists, engineers and technicians, according to the China Academy of Space Technology that designed and made the craft.

The vehicle consists of three major parts – a crew working compartment, an airlock cabin and an unpressurized service module.

China launched its Wentian space laboratory on Sunday afternoon, sending the country's largest-ever spacecraft to Earth's orbit to become part of the Tiangong space station.[Photo by Zhu Xingxin/chinadaily.com.cn]

Weighing 23 metric tons, the space lab is 17.9 meters tall, roughly equivalent to a six-story residential building, and has a diameter of 4.2 meters. It is the largest and heaviest spacecraft China has ever built and also the world's heaviest self-propelled spaceship in service, said Zhang Qiao, a head designer of Wentian's overall structure.

The flexible solar panels of the lab are the largest of their kind in China. When fully unfolded, they are more than 55 meters long and have a combined area of nearly 280 square meters.

After Wentian is connected to the Tianhe module, its airlock cabin will replace the one on Tianhe to become the major place for astronauts to put on their spacewalk suits and move out of the space station.

"Its inner space is bigger than that of the airlock cabin on the core module while its hatch is wider, making it easier for astronauts to make preparations and carry out spacewalks," Zhang said.

Inside the gigantic lab, there are eight scientific cabinets and they will mainly be used to serve biological and life science studies and can support research on the growth, aging and genetic traits of plants, animals and microbes in the space environment.

Outside the airlock cabin, there are 22 extravehicular payload adapters capable of carrying scientific experiments needed to be exposed to the space environment, cosmic rays, vacuum, and solar winds, according to him.

"In addition to its scientific functions, Wentian also serves as a backup control station to the Tianhe core module in case of emergencies or malfunctions. It has all flight-control devices same to those inside the core module to operate the entire Tiangong station," Zhang said.

China launched its Wentian space laboratory on Sunday afternoon, sending the country's largest-ever spacecraft to Earth's orbit to become part of the Tiangong space station.[Photo by Li Guanhan/chinadaily.com.cn]

The designer added that the craft also has three separate sleeping quarters and an independent section for personal hygiene and they can be used in emergencies or during crews' handovers.

Moreover, Wentian has a five-meter robotic arm that can be used to move small- and medium-sized equipment. It can also be linked with the 10-meter robotic arm on the Tianhe module to create a joint arm capable of reaching to all major parts of the Tiangong station, according to the designer.

According to mission planners, the Tiangong station's second lab named Mengtian will be lifted by a Long March 5B from Wenchang in October.

After it is connected with the Tiangong, the station will form a T-shaped structure and astronauts will have as much as 110 cubic meters in their usable space.

After the labs, the Tianzhou 5 cargo craft and the Shenzhou XV crew are scheduled to arrive at the massive orbiting outpost around the end of the year.

Upon its completion, the Tiangong will be manned regularly by groups of three astronauts in periods usually lasting six months. During hand-overs to new three-astronaut groups, the station will accommodate up to six astronauts.

Currently, Tiangong is manned by the Shenzhou XIV mission crew who entered the station late on June 5, several hours after their spacecraft was launched from the Jiuquan Satellite Launch Center in northwestern China.

The third group of Tiangong occupants, Chen and his teammates are scheduled to stay in the station for six months to monitor the assembly of the colossal station in space.

The three astronauts' flight has launched a 10-year period in which, barring unforeseen circumstances, Chinese astronauts will be in space every day.