Tianzhou-2 cargo craft completes rendezvous, docking with China's space station core cabin at record speed
Published: May 30, 2021 05:05 AM

China's Tianhe space station core cabin received its first "visiting guest" - the Tianzhou-2 cargo spacecraft early Sunday, about 8 hours after the latter's launch, setting a new record in China's space history.

According to the China Manned Space Agency, the rendezvous and docking of the Tianzhou [Heavenly Vessel] cargo spacecraft with the Tianhe core cabin took around eight hours after the former was launched from Wenchang spaceport from South China's Hainan Province via a Long March 7 carrier rocket at 8:55 pm Saturday. 

The first spaceship launched in the space station construction phase, Tianzhou-2 weighed 13.5 tons at launch, and is capable of sending a payload of 6.9 tons for supply missions. Its in-orbit service is at least one year, said Feng Yong, commander-in-chief of the Tianzhou-2 mission from the project contractor China Academy of Space Technology (CAST).

The 10.6-meter-long, 3.35-meter-diameter Tianzhou-2 cargo spaceship has two components - a totally enclosed cargo cabin and a propelling cabin, according to CAST. 

The carry-on onboard the Tianhe spacecraft includes consumables that are designed to support three astronauts on their space missions for three months, space suits for missions outside cabin and other supplies, Feng revealed, adding that during its docking with the space station core cabin, it will also carry out multiple in-orbit experiments. 

Tianzhou-2 will also deliver propellants to refuel the Tianhe core cabin, Mu Guoxin, a CAST publicity official said.

"Next, the Shenzhou-12 manned spaceship will dock with the core cabin at the front, and altogether the three sections will form the first linear structure for China's space station," Mu noted.

There were 6.8 tons of supplies onboard the Tianzhou-2, including some 160 parcels of goods and two tons of propellants, according to CAST. "The load to total mass ratio is over 50 percent, indicating its world leading capacity."

The two space suits for the astronauts' outside-cabin activities weigh more than 100 kilograms each, it disclosed.

The Saturday mission also witnessed a substantial improvement in the Tianzhou spacecraft's fast docking capability. Compared to the Tianzhou-1's rendezvous and docking with Tiangong-2 in 2017, which took about two days, it took a mere eight hours to achieve the feat.

Lei Jianyu, deputy director designer of the Tianzhou-2 spacecraft, said that there are only two cargo spaceships in active service in the world that are capable of sending payloads of more than five tons, and Tianzhou is one of them, and has the "world class capability."

The reason behind such progress lies in the fact that all the information for the docking maneuver had been installed in software with the Tianzhou-2, saving the time needed to transfer such instructions from ground tracking and monitoring facilities, which was the case for Tianzhou-1 in executing the same move. 

"Such a fast rendezvous and docking process not only shortens the stay of astronauts in the relatively narrow space in the spaceship, saving their energy, but also ensures that the transfer of fresh goods [such as biological agents] is conducted in a timely fashion," CAST developers said.

The Tianzhou-2 adopted a new long-distance guiding technology, as it was able to use the location information provided by the country's BeiDou Navigation Satellites System, or BDS, to automatically navigate itself for the rendezvous and docking with the space station, whereas the Tiangong-1 version needed artificial assistance to lead the craft to approach Tiangong-2 for the move.

In an ideal situation, the time for the rendezvous and docking of Tianzhou-2 would be reduced to some four hours, CAST announced. 

In the event of an emergency, this kind of fast rendezvous and docking technology will also facilitate quick responses by providing all kinds of urgently needed materials to the space station and rescue the trapped astronauts, according to the academy.

Yang Sheng, the cargo spacecraft system's chief designer, disclosed that ground logistics technology has also been adopted for the spacecraft. For example, astronauts can obtain the location and further information of specific goods by scanning a QR code, and the inventory information is recorded in a dynamic manner so that astronauts can keep track of changes of goods.