Structural anti-torpedo protection

English Airborne Defense System

On British ships, the main anti-torpedo bulkhead was a direct and somewhat collapsed casing. The boule formed a wide rubber dam , serving as an explosion chamber, reaching the upper edge of the armor belt . The inside of the anti-torpedo buoy was adjoined by the so-called buoyancy space , filled with liquid fuel or fresh water. Behind this compartment was a liquid fuel hopper expanding upward, protected by a light anti-torpedo bulkhead.

US Airborne Defense System

The standard reservation scheme for ships of the times of WWII . A - main armored belt , B - main armored deck , C - artillery armored deck, D - anti-torpedo bulkhead

The American "layered" underwater protection system consisted of 4 thin vertical bulkheads , covered from above with a lower splinter deck and dividing the anti-torpedo bul into 3 compartments . During a torpedo explosion, the external empty compartment absorbed part of the explosion energy, the other part was spent on deformation of the liquid-filled compartments, which also trapped all fragments arising from the explosion. The internal empty compartment was the last barrier to flooding the compartments of the power plant and the ammunition cellars. At first, it was considered very important to make the outer skin and all anti-torpedo bulkheads as thin as possible to reduce the size of the resulting fragments.

Later, the system became widespread, including on large ships of the Soviet Navy . It was originally designed as part of the body, and therefore did not form a boule. The official Soviet name is "Three-chamber anti-torpedo defense system." The three described compartments are called respectively: expansion chamber, absorption chamber, filtration chamber.

Italian Airborne Defense System

The Italian constructive underwater protection of the Pugliez system was developed by Italian specialists from 1921 to 1931 . Field tests of the Pugliès system were carried out on specially refitted tankers Brennero and Tarvisio. After completing the tests, the Puglieze was equipped with modernization battleships Giulio Cesare and Conte di Cavour, which were undergoing modernization, and later equipped with the system were all newly designed large warships of the Italian fleet ^[1] .

The constructive underwater protection of the Pugliez system consisted of two concentric cylinders , marching in the underwater part of the ship for about 2/3 of the length of the hull. The inner cylinder with a diameter of 3 m was made of 7 mm high-resistance steel, kept constantly empty and was intended to absorb the energy of the explosion. The outer cylinder with a diameter of 5.48 m formed a double skin of the side with a thickness of 10 to 15 mm and an anti-torpedo bulkhead with a thickness of 28 to 40 mm. The space between the cylinders (the protective chamber) was divided into 16 sections, filled with fuel and fresh water, which, as they were spent, were replaced with sea water. This was followed by two longitudinal filtration bulkheads, one 8–9 mm thick and the other 7 mm thick. The width of the protection on the midship frame was 7.57 m from each side ^[1] .

The estimated resistance to the underwater explosion was 350 kg of TNT, but in practice this value could not be achieved due to the insufficient strength of the riveted joints (including in the area where the external cylindrical bulkhead is attached to the bottom structures). In addition, the internal hollow thin-walled cylinder showed strength significantly higher than the calculated value, as a result of which the cylinder did not deform and the energy of the underwater explosion by the cylinder was not absorbed. ^[2] . Flooding of vast cylinder cavities during an underwater explosion could also cause a significant roll ^[2] .