Photo: CCTV

During the mission, Shenzhou-12 mission commander, veteran astronaut Nie Haisheng installed an expansion pump set, which will serve as one of the power sources for the operation of the fluid circuit of the space station's thermal control system, the Global Times learned from the system developer China Academy of Space Technology (CAST) on Friday.

Dubbed the "central air conditioner" for China's space station, the thermal control system is the key system to ensure the normal running of facility onboard as well as the coziness of astronauts' stay in space, protecting the orbiting spacecraft from the harsh space environment where its surface temperature reaches more than 150C when exposed to direct solar radiation and drops to minus 100C when the craft travels to the dark side. 

Chief designer of the space station thermal control sub-system Han Haiying, compared the pump set installed outside the cabin to a "circuit heart," which ensures the steady running of fluid across the system as the way the heart pumps blood all over the human body. 

Photo: CCTV

Eyeing the requirements to sustain at least 15 years' running of the space station, CAST developers emphasized long endurance, reliability, repairing-friendly and safety of the system at the designing stage. And they have raised the idea to install multiple expansion pump sets both inside and outside the cabin, ensuring their long stand-by capability in order to sustain the long steady running of the space station, Han explained. 

As Nie turned the wrench for the last time for the installation, with the connection of the electric and hydraulic circuits, CAST developers said they felt as if they were starting to hear the beating of a heart and they also could see the solid foundation for the 15-year stable running of the space station.  

The circuit pump, as a part that runs at a high speed for a long term, has a limited service life. Therefore, it must be repair- and replacement-friendly, according to the CAST. 

Photo: CCTV

The thermal control team has invented an exquisite and easy-to-use solution, integrating all the parts that need to be replaced into an extended pump set, facilitating the complicated connection work of machinery, electronic and fluid circuits, and "making astronauts pump-changing process as easy as changing a tire."

There are already three such thermal control pump sets inside the cabin and the one to be installed outside on Friday will be a backup one for the space station. 

The other task goal of the Friday spacewalk, the Shenzhou-12 crew is also expected to carry out the mission of raising another panoramic camera outside the cabin. During the first spacewalk mission, the crew also lifted one panorama camera outside the Tianhe core module.