STM500 is a mini attack submarine which can operate in shallow oceanic waters. Credit: STM.
STM500 will be able to operate continuously for 30 days at a water depth of more than 250m. Credit: STM.
The STM500 submarine will have a top speed of more than 18kt. Credit: STM.

STM500 is shallow water, small-sized attack submarine designed by Savunma Teknolojileri ve Mühendislik (STM), a defence engineering company based in Turkey, in cooperation with the Turkish Presidency of Defense Industries (SSB) for the Turkish Naval Forces.

The submarine will be able to operate in both brown and blue waters to perform all tactical operations, including intelligence, surveillance, and reconnaissance (ISR), submarine warfare operations, special forces operations, and mine warfare.

The first phase of production of the submarine commenced in June 2022. The project is in its pressure hull test production phase currently.

Design and features

The STM500 attack submarine will have an overall length of 42m, a waterline length of 4.2m, and a maximum beam of 8.5m. It will have a submerged displacement of 540t, while the surfaced displacement is expected to be 485t.

The submarine will be equipped with advanced warfare systems and can travel at a top speed of more than 18kt and a cruise speed of 5kt. It will be able to operate at depths of more than 250m for 30 days with 18 crew members and more than six additional members of the special forces team.

The ship will also be able to launch unmanned ground, air, surface, or underwater sea (UXV) vehicles.

The STM500 will feature a commanding officer’s (CO) cabin, galley, dry provisions, freezer room, and separate mess rooms.

Weapons and armaments aboard STM500 attack submarine

The submarine will be equipped with a total of eight heavy torpedoes and guided missiles, which will be delivered through four ready-to-fire torpedo tubes, including two tubes for guided missiles. The remaining four torpedoes and guided missiles will be stored in the payload stowage.

Roketsan, a Turkish defence contractor, will provide its AKYA new-generation heavyweight torpedoes and the submarine-launched variant of the ATMACA missiles for the STM500 submarine.

Torpedo and missile features

AKYA is a high-speed, long-range, fully autonomous or fibre optic wire-guided torpedo capable of engaging submarines and surface targets at a range of more than 50km with a speed of 45kt.

AKYA features an active/passive sonar head with acoustic counter-countermeasure capability and wake guidance. The torpedo is fitted with a proximity/impact fuse and can be launched in swim-out mode.

It delivers an insensitive warhead with an underwater shock effect when launched. It is driven by a brushless DC electric motor and a counter-rotating propeller system.

ATMACA is a long-range, high-precision, autonomous anti-ship missile capable of striking targets at more than 220km with about 220kg of high explosive fragmentation effective penetration warhead.

The missile measures between 4.3m and 5.2m in length and weighs more than 750kg. It features an inertial navigation system (INS), a global positioning system (GPS), a barometric altimeter, a radar altimeter, and an active radiofrequency (RF) seeker for missile guidance.

Sensors and radars

The STM500 attack submarine will be equipped with a combat management system, a navigation radar, optronic search and attack periscopes, torpedo countermeasures (decoys), and an electronic support measures (ESM) antenna.

It can be installed with continuous active sonar (CAS), compact towed array (CTA) sonar, passive ranging sonar (PRS), multi-aperture sonar (MAS), intercept detection and ranging sonar (IDRS), and own noise analysis (ONA) sonar.

The information collected by the sonars will be processed by the combat management system.

Engine and propulsion

The STM500 submarine will be powered by two diesel generators and lithium-ion batteries. Its main propulsion system will be driven by a 1.5MW permanent excited propulsion motor. It can also be fitted with an optional air-independent propulsion (AIP) system.

The ship will have an endurance of 3,500 nautical miles (nm) when operating on diesel, 75nm on battery and 4,000nm with the combination of diesel and AIP.