The STM 500 is a Turkish mini submarine of the 500-tonne class under construction since 2022. The shallow-water diesel-electric submarine is being built by Turkish defense company STM with completion of the first vessel not expected until 2026.^[1]

As of June 2022^[update], the customer for the project had not yet been publicly released.

The STM-500 was announced in 2021 at the 10th Naval Systems Seminar in August 2021 as a lower cost and more cost effective subsurface warfare option.^[2] Construction began in 2022. It is expected to require four years to complete construction, and up to six years to fully complete the project.^[1]

The STM-500 will displace approximately 500 tonnes, have a crew of 18, and be able to transport a squad of 6 special forces personnel. It is being designed to have an endurance of 30 days and a maximum dive depth of 250 meters.^[1]

Specifications

Specifications as of 2022 include:^[1][3]

• Displacement: 485 tonnes surfaced, 530 tonnes submerged
• Length: 42 metres (138 ft) Beam: 8.5 metres (28 ft)
• Diameter: 4.2 metres (14 ft)
• Speed: 5 knots (9.3 km/h; 5.8 mph) cruise 18 knots (33 km/h; 21 mph) max
• Endurance 6,500 kilometres; 4,000 miles (3,500 NM) on diesel power 139 kilometres; 86 miles (75 NM) on batteries
• Propulsion power: 1.5 megawatts (2,000 hp)
• Power generation: 2x diesel generator with Lithium-ion battery storage and optional air independent propulsion system
• Crew: 22 + 8 additional space for special forces personnel

Weapons include up to eight "modern heavy-weight torpedos or guided missiles, delivered via four torpedo tubes.^[1] Torpedoes can be fired simultaneously. The sub will be able to carry and launch underwater drones.^[2]

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