4 Chinese student volunteers spent 200 days in a simulated lunar lab in Beijing, the state media reported on Friday.

The volunteers lived in the sealed lab to simulate a long-term space mission with no input from the outside world. They grew their own food, and handled their own waste. At 200 days, this stay breaks the record for the longest stay in a self-sustaining cabin.

China’s lunar base plans are progressing very seriously, but before they actually send astronauts to the moon, they want to know how they can handle the rough conditions there — so they set up a “virtual” base, here on Earth. They called it the Lunar Palace.

The experience “challenged the system as well as the psychological status of the volunteers, but they withstood the test,” the module’s chief designer Liu Hong told Xinhua.

The facility treats human waste with a bio-fermentation process, and volunteers grew experimental crops and vegetables with the help of food and waste byproducts.

Two men and two women entered for an initial stay of 60 days. They were then relieved by another group of four, who stayed 200 days.

The initial group will now return for an additional 105, Xinhua said.

The Lunar Palace has two plant cultivation modules and a living cabin: 42 square metres containing four sleeping cubicles, a common room, a bathroom, a waste-treatment room and a room for raising animals.

A successful 105-day trial was also carried out in 2014.

Ultimately, China wants to build its own moon base within a decade, potentially in a partnership with the European Union. The Chinese Space Program is one of the world’s most active and aspirational. Aside from the moon base, they also want to establish a crewed space station, send an unmanned rover to Mars, and exploit the Earth-Moon space for industrial development — namely, developing space-based solar powered satellites that would beam energy back to Earth.