M23 C-Series Midget Submarine
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The C-Series is the latest successful submarine designed by Italian submarine design legend Giunio Santi. Two boats are being built for the Qatari Navy and there are potentially more exports to follow..
The C-Series submarines are being built by M23 S.R.L., the successor company to GSE Triste (Giunio Santi Engineering) and Maritalia. The shared heritage includes numerous innovative and impressive small submarines, one of the key lineages in Italy’s famous midget submarine industry.
The Qatari Emiri Navy (QEN) deal was first alluded to in announcements relating to the larger Italian naval deal led by Fincantieri in 2020, although details emerged only slowly. A MoU (memorandum of understanding) was signed with Fincantieri which mentioned the “the supply of cutting-edge naval vessels and submarines.” Then in 2024 the first submarine was observed undergoing sea trials in La Spezia, Italy. A model was also displayed at the MSPO 24 defense show in Poland.
M23 submarine during sea trials, August/September 2024 in La Spezia, Italy.
It has been reported, in export related documents, at EUR 190 million. This covers two submarines and a training system. I suspect that some level of training and ongoing support may also be included. Significantly M23 S.R.L. was subsequently mentioned instead of Fincantieri. The design is described as MIDGET AUTONOMUS SUBMARINE P / N M232017023. There may be a strong hint in this number, and also the company’s name: it may be 23 meters long (I now estimate closer to 21 meters). We can also infer that it was designed in 2017. It is known to have a 200 kw diesel engine, 70 kw electric motor and sonar.
M23 submarine visible on Google Earth
M23 Submarine Specifications
Displacement: 120-130 tonnes
Length: ~21 meters
Beam: 5 meters
Operating depth: 200 meters
Speed: 12 knots
Range: 2,200 nautical miles
Crew: 6
Passengers: 6
Weapons: 2 x 533mm (21”) heavyweight torpedoes. Lightweight torpedoes, loitering munitions and bottom mines.
Payload: 2 x special forces equipment containers
M23 & GSE - Submarine Excellence
GSE (Giunio Santi Engineering S.R.L. ) has a long tradition of small submarine construction. In the 1980s, when the company was called Maritalia, Santi was building AIP (air independent propulsion) mini-submarines starting with the IMI-35 first launched in 1982. He then developed a unique tubular construction known as Gaseous Oxygen stored in the Toroidal pressure hull (GST). This consisted of steel pipes formed into a circle and then welded together to form the hull. This was both cheaper and more versatile than traditional construction. These would be used to store gas, specifically oxygen, which could then be used to run a diesel engine even when the submarine is underwater. Combined with filtering and storing the exhaust gases in the same tubular hull, this allowed true Air Independant Propulsion (AIP) with no exhaust emissions at all. This construction was termed Gaseous Oxygen stored in the Toroidal pressure hull (GST). The oxygen was stored at incredibly high pressures (350 atmospheres) thus allowing a huge volume of gas to be carried which translated into impressively long ranges.
innovative Gaseous Oxygen stored in the Toroidal pressure hull (GST) hull construction.
The best-known submarine with GST construction was the 3GST9. This 9.5 meter (21 ft) long boat gained a certain amount of attention as a potential Special Forces transport. Today we would call it a Dry Combat Submersible (DCS). Like so many promising designs of that era the end of the Cold War appears to have dashed its prospects. Today, GSE submarines still feature tube-like annular reinforcing rings around the pressure hull used in a similar manner.
Santi sold the GST technology to Fincantieri who marketed larger designs using the method. The 1990s were a poor time for submarine orders and no units were sold.
By the 2000s Santi’s firm, then GSE Trieste, was selling luxury minisubs to the mega-rich. They were also designing military types and some of there designs did end up in the peripherals of Navies. One design, the VAS 525 SL Mk2, was supplied to a Venezuelan oil company in 2006 and may have since found its way into the Venezuelan Navy’s fleet around 2015.
More notable is the Button 5.60 Dry Combat Submersible which was tested by the US Navy. While very compact, potentially small enough to fit inside a Dry Deck Shelter (DDS), it retained Santi’s signature teardrop form with no sail.
Today M23 S.R.L. is based at a factory in Ciserano, Bergamo, Italy.
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UOES3 (Button 5.60) Dry Combat Submersible (DCS)
