China's Jiaolong submersible completes 7,000-metre sea trials after upgrade

Why it matters: Crewed deep-sea submersibles are a point of national pride in China and a marker of its marine technology ambitions. Upgrades that replace imported parts with domestic ones matter because they reduce reliance on foreign suppliers for equipment used in deep-sea research and resource surveys. Deep-sea exploration is also an area where China increasingly works with international scientific partners.

The Jiaolong (蛟龙), China's crewed deep-sea submersible, has carried out several dives of around 7,000 metres in the Philippine Sea Basin and returned safely, according to a report on 27 October from the research vessel Deep Sea No. 1.

The dives were part of a national key research programme on improving Jiaolong's operational capability and its use in science. The submersible made three dives, two of them deeper than 7,000 metres, with a maximum depth of 7,056.9 metres, the report said. All test targets for the 7,000-metre level were met.

The work was carried out during the second leg of China Ocean 100, a scientific research cruise.

Sun Yongfu, a researcher at the National Deep Sea Center, said the trials confirmed the reliability and safety of the upgraded submersible and of domestically made replacements for key components, and strengthened China's technical edge in crewed deep-diving equipment.

Before the cruise, Jiaolong was fitted with a new high-energy-density oil-immersed lithium battery pack, domestically made direct-drive low-noise DC thrusters, an expanded emergency hydraulic interface, and deep-water hydraulic buoyancy adjustment and wide-angle, high-zoom ultra-high-definition camera systems. The report said these changes brought major gains in power, propulsion, hydraulics, electrical systems and observation and communication.

Sun said that after the upgrade, Jiaolong carried out a number of deep-sea resource and ecology surveys in several sea areas, which the report said would deepen international marine cooperation.