This post is also available in:
עברית (Hebrew)
Maintaining a credible sea-based nuclear deterrent requires more than just advanced missiles. Submarines tasked with strategic patrols must remain undetected for extended periods while carrying sufficient firepower to ensure survivability and second-strike capability. As underwater detection technologies evolve, so too must submarine design, propulsion and stealth systems.
A new 7,000-ton nuclear-powered ballistic missile submarine is set to join service, representing the largest vessel yet built under its class. The submarine, known as S4, recently completed its final deep-sea trials and is expected to be commissioned in the coming months.
At approximately 130 meters in length, the platform features a lengthened hull compared to earlier boats in its class. This increased displacement enables it to carry a heavier missile load. The submarine is equipped with eight vertical launch system (VLS) tubes—double the number installed on previous variants. It can reportedly deploy up to 24 K-15 short-range ballistic missiles with a range of around 750 kilometers, or eight K-4 intermediate-range missiles capable of reaching approximately 3,500 kilometers. The vessel is also designed to accommodate longer-range K-5 missiles, with reported strike distances of up to 6,000 kilometers.
According to Interesting Engineering, power is provided by an 83-megawatt compact light water reactor developed specifically for this submarine class. The reactor is described as a quieter evolution of earlier pressurized water designs, a key attribute for stealth-dependent patrol missions. Acoustic discretion is further enhanced by a seven-blade propeller engineered to reduce noise, allowing speeds of up to 24 knots submerged. Indigenous sonar suites and anechoic tiles contribute to both detection capability and reduced sonar signature.
From a defense standpoint, the addition of a third ballistic missile submarine supports a rotational deployment model: one vessel on patrol, one preparing for deployment and one in maintenance. Such a structure underpins continuous at-sea deterrence, a cornerstone of modern nuclear strategy.
The submarine is expected to operate from a fortified underground naval facility designed to protect strategic assets from surveillance and potential attack. Its commissioning marks another step in the gradual expansion of sea-based strategic capabilities.
