Tianzhou 6 launched with cargo for manned missions

The Tianzhou 6 robotic cargo ship — the first spacecraft to visit China's Tiangong space station this year — was launched on Wednesday night to transport packages for the next two manned missions.

With Tianzhou 6 atop, the Long March 7-Y7 carrier rocket — the seventh of its kind — blasted off at 9:22 pm from the coastal Wenchang Space Launch Center in the country's southernmost island province of Hainan.

After a short flight, the rocket placed Tianzhou 6 into a low-Earth orbit. The three-story-tall cargo ship will travel for several hours to rendezvous with the Tiangong station and then dock with the massive outpost.

The cargo vehicle is the ninth spaceship to visit the Chinese space station and the first to do so since the station was completed at the end of 2022.

Tianzhou 6 is carrying about 260 packages with a combined weight of nearly 5.8 metric tons, including living necessities enough for a three-member crew for 280 days. In the food packages, there are about 70 kilograms of fresh fruit, double the quantity carried by Tianzhou 5.

There are 98 packages of science payloads, with a combined weight of 714 kg. These contain new equipment, spare parts and experiment-related materials. The payloads will be used in 29 scientific experiments and technological tests in disciplines such as life sciences, biology and fluid physics in microgravity, as well as combustion and material sciences.

With a designed life span of more than a year, a Tianzhou cargo craft has two parts — a cargo cabin and a propulsion section. Such vehicles are 10.6 meters long and 3.35 meters wide. It is the world's best space cargo transporter when it comes to carrying capacity, as more than half of its liftoff weight can be used for payloads, according to its designers.

Li Zhihui, deputy project manager of Tianzhou 6, said that compared with its predecessors, Tianzhou 6 has a remarkable improvement — it has more space in the airtight payload containers because engineers have redesigned its interiors and moved some devices from the cargo cabin to the propulsion section.

After the modifications, the cargo ship is capable of holding 7.4 tons of mission supplies, according to Li.

Pang Zhihao, an expert on space exploration and manned spaceflights, said the new version of the cargo craft features stronger transport capability and higher efficiency.

"The new model's loading ratio — the proportion of mission payloads in its overall weight — is as much as 53 percent, the best of its kind in the world. It means we could use, say, three of these craft to carry materials that would have originally required four," he said.

In addition, Pang said the new spacecraft model has an improved communication system — a phased array antenna that has good capacity and is lower in cost.

Last week, the Tianzhou 5 cargo craft undocked from the Tiangong space station and started a period of solo flight. Its connection hatch will be used by Tianzhou 6.

Tianzhou 5 is scheduled to re-dock with the space station in the coming weeks after the departure of the Shenzhou XV crew, who will return to Earth after their six-month journey ends, according to the China Manned Space Agency.

Around the end of May, the crew of the Shenzhou XVI mission is expected to arrive at the Tiangong station to take over from the Shen-zhou XV team.