The first submarine of Taiwan’s domestic submarine construction program, the Hai Kun (SS-711), recently completed a new series of surface navigation tests in the waters near the port of Kaohsiung, moving forward toward one of the most critical milestones in the evaluation schedule: the first static dive, planned for the coming weeks. The completion of the tests was confirmed by the Chung-Shan National Institute of Science and Technology (NCSIST) and by Navy sources cited in local media, which emphasized that the prototype continues “following the planned schedule” after the delays accumulated throughout the year.
In recent days, the submarine carried out navigation maneuvers, systems calibration, and stability evaluations on the water, including turning tests, directional control, and verification of the performance of its diesel-electric engines. All activities were conducted without incident and formed part of the required preparation before authorizing the first shallow static dive, a decisive phase to validate the structural integrity of the pressure hull.
Progress of Taiwan’s IDS submarine program after months of uncertainty
The Hai Kun is the first prototype built under the IDS (Indigenous Defense Submarine) Program, one of the most ambitious technological initiatives in Taiwan’s military history. Nevertheless, its development has been marked by successive delays related to the integration of foreign systems, the provision of sensitive components, and the need to secure technical certifications previously accessible only to a small number of submarine-producing countries.
On this basis, it became known in October that the Hai Kun’s sea trials were behind the original schedule, projecting that the first dive would not occur until late 2025. The submarine’s recent activity, however, has shown progressive advancement of the project toward its entry into operational service, planned —under the revised timeline— for before 2027.
A key submarine for the future of Taiwan’s Navy
In detail, the Hai Kun has an approximate displacement of 2,600 tons, with a design derived from Western standards and equipped with a diesel-electric propulsion system, advanced sonar, and integrated combat systems. The project began in 2018, when then–U.S. President Donald Trump approved the transfer of technology to Taiwan to begin developing its own attack submarines. One year later, the government revealed a scale model of the design selected for its first prototype, thereby enabling the beginning of its construction in 2020, which has since received foreign support from several countries.
Furthermore, one of the key aspects of the program is its compatibility with U.S. weaponry. In 2023 and 2024, the United States authorized the provision of Mark 48 Mod 6 AT heavyweight torpedoes, as well as associated systems, intended to equip both the Hai Kun and future IDS program units. According to the official budget proposal, the Taiwanese Navy is expected to receive next year four torpedoes that will be used for training, while fourteen additional torpedoes will be delivered in 2027 and another ten in 2028, completing the quantity originally requested by Taipei.
The most recent tests: navigation, stability, and calibration
Since its unveiling in 2023, the submarine has carried out various tests — Harbor Acceptance Tests (HAT) and Sea Acceptance Tests (SAT) — ranging from surface speed, verification of steering systems, and combat system calibrations, to communications trials and structural vibration assessments. With the first tests conducted since 2024, all of this was observed by analysts and shared through images released from Open-Source Intelligence (OSINT) and official sources, which showed the Hai Kun accompanied by support vessels and rescue teams assigned specifically for this stage.
Next milestone: the first static dive
The first dive — a test in which the submarine submerges while remaining stationary to verify watertightness, buoyancy, and depth control — will be one of the most critical points of the program. Only after passing this step will the Taiwanese Navy’s Hai Kun be authorized to begin dynamic dives and subsequently full simulated combat maneuvers.
Finally, depending on the results of the current tests, Taiwan’s submarine program contemplates the construction of eight domestically designed units (including the Narwhal), which will be added to the two Chien Lung–class submarines. At the time, Taiwan’s Ministry of Defense emphasized that this capability will help increase deterrence in the Taiwan Strait, with a fleet of modern submarines equipped with state-of-the-art weaponry. Although the development of the Hai Kun has not been free of technical challenges — stemming from the integration of multiple systems from different countries — the next units are expected to reflect a more efficient construction process, capitalizing on the experience accumulated in the prototype.
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