The domestically built submarine Hai Kun is embarking on its first overnight stay away from home. Torpedo drills are verifying its endurance.

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Taiwan’s first domestically built submarine, the Hai Kun (海鯤), departed Kaohsiung Port early Wednesday, May 8, for its 14th sea trial and 8th diving test, this time remaining at sea overnight in a milestone endurance exercise, according to military analysts. 

The overnight trial marks a significant step in the submarine’s final acceptance phase, with tests expected to last two to three days. Crew members will rotate in three shifts, simulating actual combat operating schedules, while engineers monitor battery consumption and equipment stability over an extended period.  

Military expert Chi Tung-yun (紀東昀) said the tests would evaluate the submarine’s full power cycle after charging, with dive depths progressively increasing. "This is the most critical phase of Hai Kun's acceptance process," Chi said, adding that torpedo system tests would be conducted both surfaced and submerged to verify combat readiness.

Engineers will also stress-test life support, thermal regulation, pressure hull integrity, and sonar systems under sustained conditions. If the overnight trials succeed, state-owned shipbuilder CSBC Corporation plans to formally deliver the vessel in July.