China's first cargo spacecraft, Tianzhou-1, completed an automated fast-docking with experimental space lab Tiangong-2, currently in orbit.
Controlled from Earth, Tianzhou-1 began to approach Tiangong-2 at 5:24 PM yesterday and it took six and a half hours to complete the fast-docking with the space lab.
It was the third docking between the two spacecraft using fast-docking technology. Previously, it took about two days to dock.
Chinese scientists are using experimental space lab to master the docking technology for its permanent space station expected to be ready by 2022.
China aims to build a permanent space station rival to Russia's International Space Station, Mir. It is expected to orbit for at least 10 years, and the debut of the cargo ship is important as it acts as a courier to help maintain the space station.
The experiment tested the cargo spacecraft's capability of fast-docking, laying a foundation for future space station building.
Tianzhou-1 was launched on April 20 from south China's Hainan Province, and it completed the first and second docking with the orbiting Tiangong-2 space lab on April 22 and June 19, respectively.
The cargo spacecraft will conduct the third refuelling of the space lab before returning to Earth.
The two spacecraft completed their first in-orbit refuelling on April 27 and their second in-orbit refuelling on June 15.
China is the third country, after Russia and the United States, to master refuelling techniques in space, which is crucial in the building of a permanent space station.
Tiangong-2, which was sent into space on Sept 15, 2016, is China's first space lab "in the strict sense" and a key step in building a permanent space station.
Cargo ships play a crucial role maintaining a space station and carrying supplies and fuel into orbit.