Exploring the great depths

Chinese submersibles expert promotes undersea exploration among youth, Li Yingxue reports.

Yang Bo speaks to young people, especially students, about undersea resources these days. The researcher at the Institute of Acoustics of the Chinese Academy of Sciences, is a designer and pilot of Jiaolong, China's first manned deep-sea research submersible that can touch depths of more than 7,000 meters below sea level.

Ever since the Chinese vessel succeeded in reaching a depth of 7,062 meters in the Mariana Trench in the Pacific Ocean in 2012, Yang, 39, has been sharing his experiences in public also in the hope of popularizing science among the country's youth. And, his talks about the mysteries of the sea are getting many of his young audiences interested in the subject.

China's 7,000-meter manned submersible project was proposed in 1992 and finally started 10 years later. The challenge was to test the vessel's capability of real-time communication, microphotography detection and sampling in a moving state at a designated area undersea.

The submersible was named after the mythical dragon Jiaolong.

Yang joined the project team in 2005 focusing on the acoustic communication system after he had completed his master's at the Beijing Institute of Technology.

After its designing, manufacturing and on-land test, the vessel had to go through a open water-tank test. Then it entered the final stage - sea trials - also the most challenging among all tests.

In 2005, China had only successfully dived some 600 meters undersea. And, due to the lack of prior experience, the trials of Jianglong were carried out from shallow to deep waters step by step - 0 meter, 50 meters, 300 meters, 1,000 meters, 3,000 meters, 5,000 meters and 7,000 meters.

In 2009, Jiaolong started its first sea trial in the South China Sea and Yang got an additional role as a pilot, as he knew much about the acoustic communication system of the vessel. The acoustic communication system of Jiaolong is like human eyes, mouth and ears used to communicate, locate and map the undersea landform through acoustic emissions and reception.

At 8.2 meters long and 3.4 meters high, Jiaolong weighs around 22 tons.

Before each sea trial, Jiaolong had to be lifted from its mother ship and put into the sea, he says.

"When we were releasing Jiaolong for the first time (in the sea), it was blown away by the wind, and the mother ship had to find the exact angle for the frogmen to tie it back to the vessel," Yang says. "It was also the first time we got data from the sea.

"But the communication system was not working, as the signal from Jiaolong was swallowed by the noise of the sea. It was like trying to talk in a busy market with someone, without being able to hear each other."

Yang and other team members took two-hour naps each night for two weeks on the mother ship to solve the problem and the communication finally worked in a 50-meter trial.

Then came the 300-meter trial which took around 20 times to achieve.

"We had collected nearly 300 sets of monitoring data, but we could call the depth as passed only after all data were measured twice," he adds.

Yang remembers that at 300 meters below sea level it started to get dark, but the creatures were attractive.

"I saw many kinds of corals and different fish that I had never seen before," says Yang, who had never been to sea until this trial in 2009 and all he knew about sea creatures were from books or documentaries.

The team tried 1,000 meters before heading back to the laboratory to upgrade the vessel.

In the first half of 2010, Jiaolong was back in the South China Sea for a second round of trials - this time the goal was 3,000 meters. Yang recalls that problems occurred while diving below 2,200 meters, but they vanished when floating up. "If we met certain problems, the trial must be stopped and we had to immediately float up to solve them."

The trials for 3,000 meters went well for the last few times. The submersible went down into the sea 35 meters per minute, and each trial took around 10 hours. On each trial day, Yang and two other pilots set off in the vessel in the morning and returned before sunset. Yang also had some seasickness.

"The floating up time was the most relaxing time for us, pilots, as we can observe the sea, chat and eat."

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.

Contact the writer at liyingxue@chinadaily.com.cn

(China Daily Global 07/26/2019 page15)