BEIJING, Aug. 18 (Xinhua) -- Engineers have successfully tested the propulsion system of China's planned space station lab capsules, a key step in its space station program.

Weighing 66 tonnes, the space station will comprise a core module and two lab capsules. The propulsion system will determine whether lab capsules can move in space.

Engineers designed 36 engines for the propulsion system with four to adjust the capsules' operation orbit and 32 to adjust flight attitude. Each engine is designed to work for at least 15 years, according to the China Aerospace Science and Technology Corporation (CASC), the main manufacturer of the space station.

The engines worked well and passed tests in Shanghai, said the CASC.

China is accelerating its timetable for the Tiangong space station, with the Tianhe core capsule expected to be launched in 2020. The station is due for completion around 2022.