China's cargo ship Tianzhou-4 docks with its space station
China's Tianzhou-4 cargo spacecraft, carrying supplies for the upcoming Shenzhou-14 crewed mission in June, successfully docked with the nation's under-construction space station on Tuesday morning.
The Long March-7 Y5 rocket carrying the Tianzhou-4 blasted off from the Wenchang Spacecraft Launch Site on the southern island province of Hainan at 1:56 a.m. (Beijing Time), according to the China Manned Space Engineering Office.
At 8:54 a.m. (Beijing Time), the Tianzhou-4 completed an automatic rendezvous and docking at the rear docking port of the space station's Tianhe core module.
It formed a linear shape with Tianhe in the center and the Tianzhou-3 cargo craft currently docked at its front docking port.
Like previous cargo flights, the Tianzhou-4 carries three categories of supplies, including six-month living supplies for taikonauts, spare parts for space station maintenance, and space research equipment.
The Tianzhou-4 adopted the fast-docking technology, which took only about seven hours to dock with the space station.
Li Zhihui, deputy commander of the cargo spacecraft system of the No. 5 Research Institute under the China Aerospace Science and Technology Corporation has explained the process of the docking in a previous interview with China Media Group.
Li explained that after separating from the rocket, the cargo craft moves from the perigee orbit to that of the space station by means of long-range autonomous guidance and near-range autonomous control to achieve fast-docking.
"The long-range autonomous guidance is realized through an orbital change powered by jet engine, which takes Tianzhou cargo spacecraft from a 200-kilometer-high perigee orbit to a space station orbit at 393 kilometers. Then the cargo craft enters the phase of autonomous control, where it docks with the core module after passing through four anchoring points including 5 kilometers, 400 meters, 200 meters and 19 meters away from the space station. The whole process takes 6.5 hours," he said.
Five missions ahead to complete the space station
Five more space flight missions will be carried out this year to complete the in-orbit construction of China's space station.
The Shenzhou-14 spacecraft will take three astronauts to the space station in June, stationing them in the core module for six months.
The Wentian lab module will dock with the Tianhe core module in July, and the Mengtian lab module will dock with the core module in October to complete the in-orbit construction of a T-shaped space station.
Over 200 packages in more than 40 cabinets
The Tianzhou-4 cargo craft is a fully sealed cargo craft with a total weight of 13.5 tonnes. It carries 6.9 tonnes of cargo, making it the world's most capable cargo craft in service, according to the China Media Group.
The craft is 10.6 meters long and its width reaches 14.9 meters when solar panels are fully unfolded. It consists of two parts: a propelling module 2.8 meters in diameter and a cargo storage module 3.35 meters in diameter.
The spacecraft has over 200 packages in more than 40 cabinets for different units.
The craft has also brought seeds, including wheat, soybean and corn varieties, collected from universities for experiments in space.
According to Li, the research team made several adjustments on Tianzhou-4 to enable the taikonauts to find the packages more easily, besides expanding storage by optimizing package designs.
Xu Xiaoping, deputy chief designer of Tianzhou-4 cargo craft, said that the planning will be more precise in future missions as the consumption of the propellant in this mission is used just as planned. "We can bring more packages next time" without carrying extra fuel, Xu said.
Tianzhou-4 is expected to remain with the space station till the completion of Shenzhou-14 mission.