China's new deep-sea manned submersible Fendouzhe (Striver), onboard the scientific research ship Tansuo-1, returned to the port in the city of Sanya on Saturday morning, after completing its ocean expedition. (PHOTO: XINHUA)

By Staff Reporters

The successful development of Fendouzhe, or Striver, is a clear indication that China has entered into the first echelon of deep-sea scientific research, which also means the country has established a powerful new platform for exploring 10,000-meter deep water.

The ubiquitous huge pressure in deep water is the primary obstacle preventing people from exploring the deepest ocean on earth.

"Exploring the underwater world is never easy, since the seawater pressure on objects will increase by one atmosphere (in pressure) every 10 meters of depth in the sea," Ye Cong told Science and Technology Daily. "If an object is in the Challenger Deep at the bottom of the Mariana Trench -- the deepest part of the ocean, the pressure will be more than 1,000 atmospheres, which is equivalent to the weight of about one ton on an area equivalent to the size of a fingernail. This pressure is sufficient to destroy most of the scientific research equipment."

Ye is the chief designer of Fendouzhe and deputy director of the China Ship Scientific Research Center (CSSRC). On November 10, 2020, the Chinese manned submersible Fendouzhe successfully dived in the Mariana Trench in the Western Pacific and it reached 10,909 meters, setting a new record for China's manned deep-sea diving and returned with samples of rocks, sea water and organisms from the bottom of the trench.

This means that China had successfully explored the so-called "fourth pole of the Earth", which is also an area among the harshest environment on Earth.

Nearly 1,000 scientific researchers from 20 scientific research institutes, 13 universities, and more than 60 companies, including the CSSRC, the Institute of Deep-sea Science and Engineering of Chinese Academy of Sciences (CAS), have taken part in the research and development of Fendouzhe.

The manned cabin is the core component of the full-ocean-depth manned submersible. It not only provides a hardware guarantee and safety shield for humans to enter the 10,000-meter deep sea, but also marks the technical level of a country's manned submersible. Yang Rui, researcher at the Institute of Metal Research, CAS and the person in charge of the manned cabin project, said that it is the largest pressure vessel in the entire submersible. Made with special materials, the manned cabin is directly related to whether the entire submersible can work successfully.

Under the extreme pressure conditions of 10,000-meter deep sea, the materials used in previous submersibles could not meet the requirements of Fendouzhe, in relation to target size and thickness. Independent innovation in technology was the last resort. "Our original new titanium alloy material has successfully solved problems regarding the strength, toughness and weldability encountered by the manned cabin materials, and we finally manufactured a spacious and strong manned cabin made of new titanium alloy materials," said Yang.

The reporter learned that the continuous and repeated 10,000-meter-level sea trials of Fendouzhe have verified the stability of the overall performance and system reliability of the submersible, which meets the safety regulations of large-depth manned submersibles. Meanwhile, domestic watertight connectors were offered an opportunity to test at 10,000 meters as a key equipment, and technologies like domestic manned submersibles were adopted in the trials, proving the capability and practical value of the manned submersible and laying the foundation for the following operations and maintenance applications.

At present, China has three deep-sea manned submersibles, as well as a series of unmanned submersibles such as Hailong. The country has established a preliminary full-depth deep submersible system, and has continuously achieved breakthroughs and major innovations in the development of deep-sea equipment technology.

In Ye Cong's view, China's self-developed 10,000-meter-deep manned submersible will help Chinese scientists explore freely in the deepest part of the world's oceans and realize their scientific dreams in the near future.