Tianzhou-4 cargo spacecraft

The fresh delivery package for China's space station as well as the upcoming Shenzhou-14 crew has arrived at the Tianhe core cabin on Tuesday morning with the fast and smooth docking of the Tianzhou-4 cargo spacecraft. One of the highlights in this supply run is the replacement parts for the renewal of the station's urine treatment system, which turns urine into water and supports the long-term stay of astronauts in space.

A dozen of replacement parts including calcium removal assembly and urine filters were brought up with the Tianzhou-4 spacecraft. They will replace the old ones used by the Shenzhou-13 crew who had finished their six-month stay in orbit, Global Times learned from the system developers - the 206 Research Institute of the Second Academy of the China Aerospace Science and Industry Corp (CASIC).

For the past year, the system developers have been tracking the variation of each parameter during its in-orbit flight, summarized the differences in performance on the ground and in space, and made adjustments accordingly.

The urine treatment system has been operating stably in orbit since it was launched on April 19, 2021, and all indicators of the distilled water produced by the system meet the requirements of use, the institute said. 

The system has processed nearly 1,700 liters of urine and produced more than 1,400 liters of distilled water, which has fully verified the stability and reliability of the urine treatment functions. 

Water recycling is a key technological breakthrough to ensure a long-term human stay in the space station at minimal cost, developers explained.

The system can extract five liters of distilled water from six liters of urine in one cycle, and the maximum water production rate is 2.5 liters per hour, according to the CASIC. The quality of the distilled water surpasses the country's portable water standards as well as the standard required for astronauts. The recycled water can be used for drinking, cleaning or oxygen generating purposes in the space station.