China's Mengtian space lab module, the third major component of the nation's Tiangong space station, is scheduled to be launched on Monday afternoon, according to the China Manned Space Agency.

The lab module's carrier — a Long March 5B rocket — is set to blast off at 3:37 pm at the Wenchang Space Launch Center in the southernmost island province of Hainan, it said in a brief news release.

The rocket will place the spacecraft into a low-Earth orbit nearly 400 kilometers above the ground in which Tiangong is traveling.

Several hours after the launch, the Mengtian will rendezvous and then dock with the Tiangong station's Tianhe core module, according to mission planners.

Mengtian was transported to Wenchang by ship in early August. It underwent pre-launch checks over the past three months at the launch center. The craft received fuel earlier this month at the launch center.

The lab module is about 17.9 meters long, has a diameter of 4.2 meters and weighs more than 23 metric tons, according to its designers at the Shanghai Academy of Spaceflight Technology.

Wentian, Tiangong station's first lab module, was launched on July 24 on a Long March 5B heavy-lift rocket from the Wenchang center.

Tiangong is currently composed of four modules: the Tianhe core module, the Wentian lab, the Tianzhou 4 cargo ship and the Shenzhou XIV spacecraft.

After Mengtian 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.