Wednesday, 2 February 2022

Hunters Of The Deep - Turkey’s Small Submarines

By Stijn Mitzer
Armed with several torpedoes and nimble in their movements, these hunters and killers of the deep dare not be dismissed by their smaller size. The potency of small submarines was reaffirmed when a North Korean midget submarine sunk the ROKS Cheonan, a Pohang-class corvette of the South Korean Navy, in 2010. The Cheonan's active sonar had failed to detect the North Korean submarine that had been lurking in the area for the past day, which fired a single 533mm torpedo at the unsuspecting target. The submarine that had caused this tragedy slipped back into the dark waters of the North unnoticed, providing a tragic reminder of the effectiveness of small submarines.

Relatively few countries in the world are still designing or actively operating small submarines today. While generally easier to design and less expensive to acquire than regular attack submarines, their shorter endurance and often light armament makes their acquisition an illogical choice for most sea-going nations. Only countries with oceanographic geographical features that favour the deployment of small submarines have looked at their operations with interest. Such countries include Indonesia, Iran and North Korea, the latter two of which operate large numbers of small submarines. Other countries that come to mind are Turkey and Greece, which are embroiled in the Aegean dispute.
Because of the many islands dotting the Aegean Sea that provide a natural sanctuary for submarines, the Aegean Sea can be dubbed a 'submariners paradise'. The introduction of a fleet of small submarines to the Aegean by the Turkish Navy would significantly complicate anti-submarine warfare (ASW) operations by Greece, and turn the Aegean Sea and certain parts of the Mediterranean Sea into deadlier waters than ever before. The same principle also applies to the Hellenic Navy, which might look to replace some of its 40+-year old Type 209 submarines with smaller designs as a cheaper alternative to acquiring more Type 214s from Germany, for which the country currently lacks the funds.

Turkey's small submarine designs are also perfectly positioned to become a hit on the international market. Turkish defence companies have an eye for penetrating and later conquering defence markets, as already evidenced by the success of Turkey's UCAVs and AUSVs. [1] [2] Just like with the AUSV market, Turkish shipyards are likely to face relatively little competition when offering their small submarine designs to foreign countries. Only North Korea and China currently offer small submarine designs for export, with the former ruled out as a source for armament for all but a few countries in the world. China has so far achieved little success with selling its submarine designs abroad, and it doesn't seem implausible that Turkey could soon gain a monopoly position in the small submarine market. [3]

Artwork by HI Sutton.

An added benefit of Turkey's two small submarine designs is that while both types are classified as small submarines, they are not direct competitors. The STM500 by STM offers many of the capabilities of attack submarines at a lower cost, which was apparently enough to already secure its first foreign customer, while the L Sub 33 design by Dearsan Shipyard offers characteristics closer to a midget submarine. [4] While some have argued that the introduction of small submarines to the Aegean Sea by Turkey would be a game changer, it can be argued that they are better described as market changers. Countries that previously lacked the funds to acquire modern submarines can now purchase them at affordable prices from a politically-neutral nation with a growing worldwide influence: Turkey.

This is not only set to include the STM500 and the L Sub 33, but also the 60-metres long indigenously-designed TS1700 attack submarine fitted with air-independent propulsion (AIP). [5] This design features many of the characteristics of the German-Turkish Type 214TN class, and is positioned as a direct competitor to the Type 209 and Type 214 submarines currently offered for export by South Korea and Germany. The fact that Turkey can now offer a large attack submarine, two small submarines types in different classes and a midget submarine for infiltration purposes could shake up the submarine market at the cost of countries like Germany, France and South Korea.
Countries that could end up acquiring Turkish submarines within the coming decade include Indonesia, Ukraine, Pakistan, Qatar, Turkmenistan and the Philippines. Even nations that previously were forced to acquire submarines second-hand because of their lower acquisition price could now opt for brand-new designs because these are now finally financially attainable. Some of these countries include Poland, Romania, Bulgaria, Colombia, Peru, Ecuador and Chile. While Turkey was still reliant on German submarine designs just a few years ago, the idea of Turkish submarines being used by the navies of several European countries now seems anything but far-fetched.

A model of the STM500.

The STM500 by STM Naval Engineering is the most advanced small submarine design on offer, and boasts many of the capabilities of larger attack submarines. This includes an AIP system, four torpedo tubes for a total of eight torpedoes or 220+-km ranged Atmaca anti-ship missiles (AShMs), mine-laying capabilities and the capability to deploy autonomous underwater vehicles (AUVs) and special forces. [6] Their operations will be controlled by an indigenously-designed naval combat management system. The crew of eighteen can sustain up to thirty days of operations at ranges up to 4000 nautical miles (with AIP), roughly half that of larger attack submarines like the German Type 212.
STM already has significant experience in the design, construction and upgrading of submarines. STM is currently constructing the Type 214TN Reis class submarines for the Turkish Navy, and is also upgrading its older Type 209 class submarines. [7] Work doesn't only include the Turkish Navy's submarines, but also the Agosta 90B-class of the Pakistani Navy. In 2016, STM secured a $350 million contract to modernise Pakistan's two Agosta 90B submarines, ironically outbidding the French company that built them more than 40 years ago. [8] 
Success has already been achieved with the STM500 design, with a first boat set to be constructed in 2022 for an unknown customer, although Ukraine and especially Pakistan are likely candidates. [4] It is currently unknown if the Turkish Navy intends on acquiring any small submarines as well, with its submarine service currently in the process of receiving the first out of an eventual six Type 214TN submarines. After their entry into service, Turkey is then set to produce the fully-indigenous MILDEN class of attack submarines. With their eyes on the future, a number of small submarines could be acquired for use in the Aegean to relieve the Type 214TNs for duties in the Mediterranean.

The design by Dearsan is notable for its distinctive chined sail not unreminiscent of the Swedish A26 class of submarines. The L Sub 33 is the first submarine to have been designed by Dearsan Shipyard, which already achieved significant success with a number of surface combatants in Nigeria and Turkmenistan. [9] [10] These same countries are also potential clients for the L Sub 33, with an acquistion of submarines by Turkmenistan likely to occur in this decade. In fact, it doesn't seem implausible that the L Sub 33 was specifically designed to meet a Turkmen Navy requirement for a small type of submarine.

The L Sub 33 comes in at 33.6-metres, making it significantly smaller than the STM500. [11] Though not equipped with AIP, the design leans itself well towards stealthy infiltration missions, for which its 1600 nautical miles range and underwater thruster are potent tools. Corresponding to its smaller size, only two 533mm torpedoes and six bottom mines are carried. The L Sub 33 has a crew of six to eight persons, and can carry a special forces detachment of eight more. These can leave and enter the submarine via a diver lockout chamber located below the torpedo tubes. Through these feats, the L Sub 33 is essentially a hunter killer submarine and infiltration submarine rolled into one design.
Another small submarine design by Dearsan, tentatively dubbed the Multi Purpose Seal Submarine, is specifically designed to insert combat swimmers or special forces deep into enemy waters. This 19.2 metres-long sleek design has a range of some 100 nautical miles and can carry eight combat swimmers or special forces in addition to its two-person crew. [11] Like most of Dearsan's ship designs, the Multi Purpose Seal Submarine appears to have been specifically designed for export, but could perhaps one day fulfill a Turkish Navy requirement for a stealthy delivery vehicle for special forces and their equipment. In addition to these two types, Dearsan has also developed a 6.5 metres-long autonomous underwater vehicle (AUV) that can carry a 600kg payload to a range of 50 nautical miles. [11]

The Multi Purpose Seal Submarine.

(Click on the submarine to see a picture of them)

Small Submarine - Hunter Killer

  • STM500 [STM] (Can be armed with eight 553mm AKYA torpedoes, Atmaca AShMs or mines)
  • L SUB 33 [Dearsan] (Can be armed with two 533mm AKYA torpedoes or six bottom mines)

Small Submarine - Infiltration

[1] An International Export Success: Global Demand For The Bayraktar TB2 Reaches All Time High
[2] The Market Leader: Turkey’s Indigenous Unmanned Surface Vessels (USVs)
[8] Despite French Sanctions, Turkey Making Progress in Pak's Agosta 90B Sub Upgrade 
[10] Bigger Business: Turkey Unveils F142 Frigate Design