Exploring the great depths

In June 2011, Jiaolong faced its 5,000-meter trials in the northeastern Pacific Ocean. The media started to notice the vessel and the trials were covered live on TV as well.

"We tried 5,000 meters seven times, and each time it was successful, because by then we already understood what exactly deep-sea equipment is from our previous trials," says Yang.

Each time Jiaolong achieved a new depth, other crew members splashed water on the pilots when they returned to the mother ship, as a kind of ritual.

In Yang's memory, the trials for 7,000 meters were easier than the previous ones. On June 27, 2012, Jiaolong reached a depth of 7,062 meters in the Mariana Trench in the western Pacific. Three days before, Yang and the other pilots spoke from this depth with Chinese astronauts who encouraged them from Tiangong-1 space lab.

With six dives in total, the trials were completed in 2012 and it was confirmed that the performance of Jiaolong was stable at a depth of 7,000 meters.

All functions of the submersible were tested at least twice and the faults found in the tests were remedied.

While Jiaolong was doing its sea trials, another manned submersible project named Shenhai Yongshi (Deep Sea Warrior) started in 2010, and Yang became the deputy chief designer on it.

Shenhai Yongshi is designed to reach a depth of 4,500 meters and finished its sea trials in 2017.

In March, Shenhai Yongshi finished its first expedition in the Indian Ocean.

A new mother ship named Shenhai Yihao (Deep Sea No 1) is expected to carry Jiaolong to the Mariana Trench for another expedition this year.

"We were a young team when making Jiaolong, with around 60 to 70 percent of our team members in their 30s, and now looking back at that experience is helping us to grow quickly as scientists," says Yang.

"Jiaolong helped us to find our direction in developing new technology for undersea research."

Having reached great depths with Jiaolong, Yang and the team of China's new manned submersible (which plans to dive to 11,000 meters underwater) are preparing to explore further.