Singapore’s highly capable Type 218SG submarine program illustrates the lengths the small island nation is willing to go to maintain one of the most advanced navies in Asia—and to retain the city-state’s technical edge in the ever-more-competitive undersea environment. The Type 218SG, also known as the Invincible class, will help defend Singapore and secure access to its sea lines of communication.
The class is being built to replace the country’s aging Challenger- and Archer-class boats, which date from the 1960s and 1980s. These older subs had been purchased secondhand in the 1990s and 2010s from Sweden (where they were known as the Sjöormen class and Västergötland class, respectively), and they were later modernized with air-independent propulsion (AIP) systems for Singaporean service. The Type 218SG has instead been designed from the outset to meet Singapore’s tropical environment and unique maritime requirements and is being built in Germany by ThyssenKrupp Marine Systems.
Four Type 218SG submarines are currently planned. The first two, the Invincible and Impeccable, were ordered in December 2013, and a contract for two additional boats, to be named Illustrious and Inimitable, was signed in 2017. Steel was cut on the initial submarine in 2014, and the Invincible was launched in early 2019. Her sea trials began during the summer of 2020 and continued through early 2021. The COVID-19 pandemic has complicated construction timelines, and the first unit is now expected for delivery a year late, in 2022. The second submarine is expected to follow a year later, while delivery of the third and fourth boats is scheduled by 2026.
The Type 218SG is 230 feet long, with a submerged displacement of 2,200 tons. The design incorporates experience gained from previous cutting-edge AIP submarine programs, including Germany’s Type 212A. The Invincible class features X-configuration control surfaces for enhanced maneuverability in crowded and shallow waters, along with an array of new systems, many of which were developed indigenously for increased crew comfort, combat capabilities, and situational awareness. The Type 218SG makes extensive use of automation and requires a small crew of only 28 officers and enlisted personnel.
The Invincible’s diesel-electric propulsion incorporates an AIP system with fuel- cell technology that reportedly enjoys 50 percent more endurance than previous systems, enabling quiet underwater operations for several weeks at a time. The class has a top speed in excess of 15 knots submerged, or more than 10 knots when surfaced. Armament consists of eight 21-inch bow torpedo tubes, which can potentially launch either heavyweight torpedoes or antiship missiles. The Type 218SG also can reportedly transport and deploy naval special operations forces from an airlock for a variety of missions.
