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Purified urine provides clean drinking water for astronauts

By ZHAO LEI in Wenchang, Hainan | CHINA DAILY | Updated: 2021-04-30 09:40
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Special apparatus cuts resupply costs, allows for longer durations, designer says

Researchers and engineers at the China Aerospace Science and Industry Corp, a major defense contractor, have several sets of its instruments inside the core capsule of the country's space station that was launched on Thursday.

Rather than lethal weapons, those instruments will serve astronauts who live and work inside the station. One is especially indispensable-the urine treatment and water recovery apparatus.

Developed and built by engineers at the CASIC Second Academy's 206th Institute, the apparatus was activated for in-orbit testing shortly after the capsule entered orbit, and the results showed it functions well.

"We sent signals from ground control to start the machine for a certain period of time to check whether it can dispose of simulated urine as we had designed. The readings were normal, which means our design works," said Cui Guangzhi, chief designer of the apparatus at the institute.

"Urine treatment and water recovery are among the most important parts in a space station's environmental control and life support system, being vital to astronauts. Long-term manned space missions rely heavily on regenerative life support systems, and resupplying water, oxygen and food poses challenges. A reliable urine treatment and water recovery apparatus will help extensively reduce resupply costs and allow for longer-term missions."

Once astronauts of the Shenzhou XII mission enter the core capsule in the near future, the apparatus will formally begin operation, Cui said.

The machine's processing method sounds simple-urine will be mixed with chemical agents for initial disposal and then pumped into a vacuum container, where it will be boiled for evaporation. Then, water molecules will be collected from the steam and be further purified.

However, engineers had to overcome a number of technical difficulties to make sure the process can occur smoothly in the space station's unique environment, which differs from Earth's in various ways, according to Wang Tianbao, a member of Cui's team.

"For instance, in the station's microgravity environment, it is very hard to extract and concentrate water molecules from the vapor, so we developed a special device to separate them," he explained.

Wang said the apparatus is capable of recovering more than 80 percent of the water in urine and can produce 2.5 liters of pure water each hour.

Cui said that the processed water will not only be drinkable, but even cleaner than standard drinking water in China. It will mainly be used for astronauts' consumption, cleansing and oxygen production.

The 206th Institute began to design the prototype of the apparatus in August 2012 and finished the design work in early 2013. Engineers then manufactured several prototypes and started to conduct a great number of ground tests to examine their capability and performance.

Previous Chinese manned missions kept astronauts' urine in a special container, which would burn along with the spacecraft's unmanned section as it fell back to Earth.

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