The Shenzhou-15 crew, who set a domestic record for conducting the largest number of spacewalks by a single crew, have recently recalled particular hard moments of their four extravehicular activities (EVAs), as the operation in orbit requires precise control of their bodies as well as tacit cooperation among crew members. 

The trio has now performed extravehicular activities on four occasions since they were launched into space in November 2022. 

The Shenzhou-15 astronauts on board China's orbiting space station completed their first spacewalk on February 10, with Fei Junlong and Zhang Lu carrying out operations in space and Deng Qingming offering support from inside the space station. 

During the EVAs lasting about seven hours, they completed several tasks, including the installation of the extension pumps outside the Mengtian lab module. During this mission, Fei and Zhang needed to maneuver between the Wentian lab module, the Mengtian lab module, and the core module to install the extended pump on the Mengtian. 

Fei was in charge of installing the equipment and Zhang was on the armrest of the bulkhead to assist in observing the alignment of the equipment, while Deng was paying close attention to the operations of the two crewmates from inside. 

"I think that the astronaut staying inside the module serves as the eyes and the extension of the crewmates' arms. Because what he sees is a partial picture while I can see his maneuver track during the entire process, from one location to the next and then the next," Deng said in an interview with China Media Group (CMG). "I see it all on pictures of the space station while he can't see it. Your eyes need to follow wherever he goes and push the emergency button to stop the operation should there be an emergency situation."

On March 2, Fei and Zhang carried out the second spacewalk to install equipment among other operations. Deng stayed inside the space station to provide support. 

After leaving the module, Fei and Zhang first needed to maneuver to the operating point with the help of the handrails outside the module. During the process, Fei had to take off the two safety rope hooks from the previous handrail before hooking them to another handrail. 

Though seen as a simple movement, picking and hanging the safety rope hooks in space was a huge challenge to astronauts as it required great strength from the astronauts' upper limbs, given the heavy pressure from the spacesuit. 

"When walking outside, we need to avoid touching some equipment, some sensors, and some engines installed outside the module. The equipment may leave a very narrow gap for you (to pass through). Sometimes, you have to crawl like this, sometimes you have to crawl with your body standing straight. Sometimes you have to climb backwards and sometimes you have to crawl sideways," Fei told CMG.

There were 20 plugs on the equipment that Fei and Zhang needed to install and each of them goes with a protective cover. When installing, Fei had to pull out the protective cover first, then plugged in the plug, and did a power-on test during the plug-in process. 

The installation operation would consume a huge amount of physical energy, as the astronaut had to stabilize his body while carrying out the fine work. Therefore, Fei had to rest several times during the operation. 

"Fei used only two fingers to pull out the plug and plug it in again. It is true that this process may not be understood by others, but I know it is very tiring. This kind of tiredness is not like the feeling of exhaustion from carrying a sack or a load of food grain. It is not like this kind of tiredness. The kind of tiredness from spacewalk is a feeling of stiffness and numbness involving the whole hand muscles, which makes the heart rate increase in just about one or two minutes," Zhang said. 

The previous spacewalks had accumulated experience for Fei and Zhang to carry out the third spacewalk on March 30. This time, they were entrusted with the task of installing and connecting cables across the module. There were more than 40 plugs at both ends of the cross-module cable, which increased the intensity and difficulty of the work to a great extent compared to that of the last time.

Two weeks later, the Shenzhou-15 trio completed the fourth, also their last spacewalk during their six-month stay in the orbit, setting a domestic record for the most spacewalks by a single crew. 

The Shenzhou-15 crew returned to Earth on June 4 after fulfilling the six-month mission and after completing the in-orbit crew rotation with their Shenzhou-16 colleagues in space.