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Underwater Transport Containers

Page Created
January 19th, 2025
Last Updated
January 24th, 2025
Italy
Italian Flag
Length
8 metres
Wide
1.4 metres
Height
1.4 metres
Weight
2.8 tonnes
Propulsion
Armour
Armament
History
Transport Container

In mid-1940, the Italian Navy began adapting submarines for the covert transport and deployment of Siluro a Lenta Corsa units, also known as human torpedoes, significantly improving on earlier methods used by the submarine Iride. The system on Iride was rudimentary, with the Siluro a Lenta Corsa’s simply strapped to saddles on the submarine’s deck.

Shortly after the loss of Iride during the first operation, Operazione Golfo di Alessandria 1, Admiral Domenico Cavagnari, Chief of Staff of the Regia Marina, issued a new operational order. The Xa Flottiglia MAS was tasked with conducting simultaneous attacks on two critical Allied naval bases: Alexandria, the headquarters of the Mediterranean Fleet, and Gibraltar, the base of Force H.

Two submarines, Gondar and Scirè, are selected and modified specifically for transporting Siluro a Lenta Corsa’s. The modifications, carried out at the Odero Terni Orlando shipyard in La Spezia, involve equipping both submarines with watertight container cylinders mounted on their decks. These cylinders allowed the submarines to carry, protect, and deploy Siluro a Lenta Corsa’s at depths of up to 90 metres, a significant improvement over Iride’s system, which permitted a maximum depth of only 30 metres. The new system eliminated the need for support vessels and intermediate stopovers, which had previously exposed operations to unnecessary risk.

Each submarine was fitted with three cylinders: one positioned forward of the conning tower and two aft, mounted side by side. Each cylinder weighed 2.8 tonnes and was capable of withstanding the pressure at the maximum test depth of the Adua-class submarines, 90 metres. The transport containers for the Siluro a Lenta Corsa were carefully designed to accommodate the torpedoes and support their deployment in covert naval operations. Given that each Siluro a Lenta Corsa measured 7.3 metres in length and had a diameter of 53 centimetres, the containers needed to be robust, watertight, and spacious enough to ensure safe storage and deployment.

Each container was constructed to slightly exceed the Siluro a Lenta Corsa’s dimensions, providing sufficient clearance for operational mechanisms and structural reinforcement. The containers were approximately 6.6 metres in length, ensuring the Siluro a Lenta Corsa’s could be securely housed with room for access and handling.

The internal diameter of the containers was designed to accommodate the 53-centimetre-wide torpedo with additional clearance. This space allowed for insulation, water-flooding systems, and ventilation to maintain the Siluro a Lenta Corsa’s batteries. The internal diameter was estimated to be around 1.2 to 1.3 metres, while the external diameter, accounting for the thick structural walls, reached approximately 1.4 metres.

Built to withstand the immense pressure at depths of up to 90 metres, the containers also served as ballast tanks, capable of holding up to 21.75 cubic metres of water when fully flooded. This feature added versatility, enabling the containers to assist with submarine stability during operations. The design ensured that the containers could be flooded or drained as needed, while their hemispherical hatches allowed the Siluro a Lenta Corsa’s to be deployed seamlessly in either surfaced or submerged conditions.

The cylinders were connected to the submarine through an internal system of valves and pipes, enabling them to be flooded or drained as needed. They also contained electrical systems to ventilate the cylinders and charge the Siluro a Lenta Corsa batteries. Each cylinder was sealed with a hemispherical watertight hatch that opened laterally. Notably, Gondar’s forward cylinder lacked reinforcing rings, differentiating it from the design used on Scirè.

To offset the added weight of the cylinders, modifications included the removal of Gondar’s 100/47-millimetres deck gun, its ammunition, two torpedoes, and other equipment deemed non-essential.

Two operational methods were developed for releasing the Siluro a Lenta Corsa’s. In the first, the submarine would surface with only its conning tower exposed, remaining stationary. The operators would exit the submarine through the upper hatch, walk along the deck, flood the cylinders, open the hatches, extract the Siluro a Lenta Corsa’s, and proceed toward their targets. In the second method, the submarine would lie on the seabed at a depth of approximately 12 metres. The operators, equipped with breathing apparatus, would exit the submarine through a floodable escape compartment, open the flooded cylinder hatches, extract the Siluro a Lenta Corsa’s, and commence their mission.

Motoscafo Turismo Ridotto Deployment

In early 1941, the Regia Marina recognises the need to simplify operations and reduce the risks associated with surface vessels acting as carriers for explosive motorboats. Inspired by the success of the Siluro a Lenta Corsa, submarines are proposed as an alternative means of transport, utilising the same type of watertight cylinders designed for self-propelled craft. This shift represents a significant evolution in Italian naval strategy, prioritising stealth and flexibility.

The primary obstacle in adapting submarines as carriers lies in the dimensions of the standard explosive motorboats. To overcome this challenge, a smaller variant is developed, officially named the Motoscafo Turismo Ridotto (Reduced Tourism Motorboat), though naval staff commonly refer to it as “erre” (R). Building upon this design, an improved version, the Motoscafo Turismo Ridotto Modificato (MTRM), is already under development by 1943, prior to the armistice.

One of the earliest technical blueprints for this smaller craft, CABI drawing A.550, is dated 28 February 1942. The Motoscafo Turismo Ridotto maintains a similar length to its predecessor, the Motoscafo Turismo Modificato, but its beam is reduced by approximately 60 centimetres to enable submarine transport. The craft features a hard-chine, unstepped hull, and its fully loaded weight is 1,250 kilograms. Its overall dimensions are 6.185 metres in length, 1.080 metres in beam, and 1.14 metres in depth. These dimensions are calculated with the stern drive raised and the windscreen and compass temporarily removed, both of which are reinstalled upon launch.

The transport cylinders on the submarines measure approximately 6.6 metres in length and have an internal diameter of about 1.15 metres. These compact dimensions require every available inch of space to be optimised. The Motoscafo Turismo Ridotto is adapted accordingly. The life-raft sections are reduced in size to 0.425 metres in length, 0.5 metres in width, and 0.15 metres in depth. The hull sides are given a more convex shape compared to the near-vertical profile of the Motoscafo Turismo Modificato.

To conserve space, the explosive charge and cylindrical petrol tank, measuring 37 by 50 centimetres, are mounted directly on the keel rather than on the floor. The refuelling nozzle is cleverly recessed within a deck compartment to avoid protrusions, and the air intakes are replaced with a rectangular, front-hinged hatch. Additionally, the lubrication oil tank and battery are relocated to the right side of the engine compartment to ensure a more efficient use of space within the craft.

This meticulous design and compact configuration allow the Motoscafo Turismo Ridotto to be effectively transported within submarines, marking a critical advancement in the Regia Marina’s ability to carry out covert and precise naval operations. By integrating these compact explosive motorboats with stealthy submarine deployments, the Italian Navy enhances its tactical capabilities, demonstrating innovation and adaptability in the evolving theatre of war.

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