China's manned submersible Fendouzhe or "Striver" surfaced on Nov. 10 after descending 10,909 meters below sea level for six hours of data collection and scientific research in the Mariana Trench.

This feat has set a new deep-sea diving record for China.

The submersible, which carried three experts, started diving at about 4 am Beijing time last Tuesday. Upon reaching the record depth at 8:12 am, the machine evaluated its speed, depth, and the geological conditions of the surrounding seabed, before pausing to allow the three experts inside to conduct necessary sampling work.

China launched the 10,000-meter manned submersible project in 2016. Ye Cong, chief designer of the submersible, described to Science and Technology Daily some of the challenges in deep-sea diving.

According to Ye, first the foremost is how to deal with the incredible effects of water pressure 10,000 meters under the sea, which is measured at approximately 1000 atmospheres, or the equivalent to 2,000 African elephants stepping on a person's back. The submersible must all be able to hold experts and scientific equipment to carry out exploration works.

Thanks to the support of several adaptable key technologies, such as the manned cabin's spherical shell and various buoyancy materials, the submersible can operate in every ocean around the world.

The cabin, for instance, is manufactured using an innovative welding technique which reduces the number of seams and is thus sturdier in high-pressure aquatic environments. Its shell was built using titanium alloy in southern Jiangsu's Wuxi city.

This latest exploration mission was supported by two mother ships: Tansuo-1 and Tansuo-2. Tansuo-1 has a displacement of 6,250 metric tons and boasts a cruising radius exceeding 10,000 nautical miles. Meanwhile, Tansuo-2 was completed in June of this year after being renovated from an offshore marine engineering vessel. Six of its key pieces of equipment were domestically produced, including the submersible deployment and retrieval systems.

China's first manned submersible, the "7103 Lifeboat" was successfully developed in 1986, which opened a new chapter for the country's R&D efforts in the deep-sea field. In addition to the self-developed manned submersibles such as Jiaolong and Deep Sea Warrior, China has also stepped up its efforts in unmanned submersibles, producing more recent vessels such as Haidou, Haiyan, and Haiyi.

Bao Gengsheng, a researcher from the Institute of Deep-sea Science and Engineering under the Chinese Academy of Sciences, explained the necessity of developing 10,000-meter deep-sea manned submersibles.

Bao said that the R&D efforts of manned submersibles can aid in making key technical breakthroughs as they have superior maneuverability and can carry more scientific equipment for underwater exploration.

(You can also read it at: http://www.china.org.cn/china/2020-11/17/content_76919944.htm)