China is pressing ahead with a pivotal project to test an 11,000-meter deep-sea manned submersible in four years, as it aims to set up a deep-water laboratory to conduct further marine scientific research, said a scientist in charge of the program.

Yan Kai, director of the State Key Laboratory of Deep-sea Manned Submersible at the China Ship Scientific Research Center in Jiangsu province, said the deep-sea craft is scheduled to conduct its first test in 2021.

Yan said the submersible is capable of diving into the world's deepest known place - the Mariana Trench.

The sophisticated device belongs to the Jiaolong family, whose manned deep-sea explorer dived 7,062 meters in the Pacific Ocean's Mariana Trench in 2012 and set a world record. It will be jointly built by research institutes and shipyards of China Shipbuilding Industry Corp, one of China's major State-owned shipbuilders.

Yan said existing submersibles can cover 99.8 percent of the world's marine area, while the 11,000-meter deep-sea vehicle will enable scientists to exploit the remaining 0.2 percent located in several deep trenches.

However, the development of the 11,000-meter device is still confronted with major challenges such as pressure-resistant materials, design, power-supply and telecommunications, according to Yan.

Despite all the odds, Yan said it is of "huge scientific value" for human beings to explore the unknown ocean world.

Yan said such breakthroughs will lay the foundation for a deep-sea researching station, whose "single underwater visit is estimated to last from several months to half a year and can accommodate dozens of people". Existing submersibles can only work for 12 hours in a single dive and have a very limited passenger capacity.

Under the plan, the undersea laboratory will be mainly for scientific purposes, where scientists can conduct genetic and biological research, and explore mineral, oil and gas resources in the seabed. Using traditional fuel cells, the device enables passengers to live and work in it for two weeks to a month.

However, Yan said more powerful fuel cells, nuclear power and even unknown undersea energy options can supply power to the facility in the future.

"Due to technology restraints, only the United States and Russia are capable of building high-end submersibles and deep-sea research stations, which means they have the edge to gain new knowledge about the ocean and the Earth," said Dong Liwan, a shipbuilding professor at Shanghai Maritime University.

But so far no existing data indicated that their deep-water devices can reach 11,000 meter deep, Yan said.

Contact the writers through jingshuiyu@chinadaily.com.cn