Japan's Ministry of Defense has begun developing a vertical launch system (VLS) for future conventional diesel-electric submarines, drawing global attention through media reports. Militarnyi, a Ukrainian military affairs outlet, recently reported that Japan has launched development of a VLS to equip next-generation submarines with long-range missiles, mindful of the submarine capabilities held by the South Korean Navy.
Notably, the new VLS Japan is pursuing is being designed to accommodate multiple types of missiles. Among the candidates under discussion are a sea variant of the High-Velocity Gliding Projectile (HVGP), long-range cruise missiles, and hypersonic missiles. The ground-launched version of the HVGP is called the "Type 25." In this method, a rocket booster lifts the glide body to high altitude, after which it glides toward its target at high speed.
Among these, hypersonic missiles fly at speeds exceeding Mach 5 (6,120 km/h) and maneuver during flight to make trajectory prediction difficult, making detection, tracking, and interception virtually impossible. Only three countries worldwide have developed and possess such weapons: the United States, Russia, and China. In response, South Korea, along with Germany, France, Japan, and India, are joining the race to develop hypersonic missiles.
According to Japan's Ministry of Defense, the project runs from 2026 to 2029. Japan will invest a total of 3.9 billion yen (about 36 billion won) to verify design feasibility and launch stability. It plans to reduce development costs and technical risks by using high-precision virtual simulations that reproduce actual operating environments. In the disclosed concept diagram, one VLS module contains seven to eight launch tubes.
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This means that mounting two or three modules on a single submarine would secure a total of 14 to 24 vertical launch tubes. Japan's submarine VLS concept became known as it took concrete shape in the next-generation submarine concept unveiled by Kawasaki Heavy Industries in 2023. The design at the time included a larger hull than before, an improved propulsion system, and vertical launch tubes for striking ground targets.
If Japan secures VLS-equipped submarines, it would emerge as a threatening presence, as it could operate multiple and diverse missiles larger than those fired from torpedo tubes. Utilizing the stealth of submarines, its options to strike not only maritime targets but also land targets would expand. However, it remains in the early stages, and considerable time is needed before actual deployment, including virtual verification, hull integration, and underwater ejection tests.
Currently, the submarines operated by Japan's Maritime Self-Defense Force have no separate VLS. They operate U.S.-made Harpoon anti-ship missiles and others through 533mm torpedo tubes. In addition, Kawasaki Heavy Industries is also producing and delivering to the Maritime Self-Defense Force the Type 12 surface-to-ship guided missile enhanced-range version (SSM-ER) to be mounted on surface ships and submarines.
Going a step further, Japan has taken the position that it will also pursue the introduction of nuclear-powered submarines. Japanese Defense Minister Shinjiro Koizumi said at a press conference that U.S. President Donald Trump had approved South Korea's construction of nuclear-powered submarines, adding, "If all neighboring countries come to possess nuclear-powered submarines, (Japan too) will not rule out any options," expressing his intention to also consider introducing nuclear-powered submarines.
The ruling Liberal Democratic Party and its coalition partner, the Japan Innovation Party, also stated in their coalition agreement last year that they would join forces to acquire submarines equipped with vertical launch systems (VLS) using next-generation power. This was interpreted as effectively having nuclear-powered submarines in mind. Japan is known to possess more than 20 submarines. It does not operate nuclear-powered submarines.
