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Cheap means of sinking a ship

By Sakhal

Magnetic mines

During 1940 Germany surrounded Britain with dangerous minefields to destroy the convoys that coming from the United States supplied the country and its war effort, and to sabotage any attempt from British armies to reach the continental Europe. In that same year, the British were taken by surprise by a new type of mine deployed by the Germans. Along the coasts, some ships were mysteriously sunk, while in the Thames six merchants exploded, and even the battleship Nelson was severely damaged by a mysterious explosion. Pound, first Lord of the Admiralty, declared then that the Germans possessed a secret device whose countermeasure would not be possible until its identification. The time had been passing with anxiety, but the 22nd November news came from the mouth of the Thames: a German airplane prosecuted by British fighters had dropped several voluminous objects, one of which had been located. The engineers quickly examined the object, discovering the first secret weapon of the Third Reich: the magnetic mine. This device was equipped with a magnetic sensor, sensitive to variations on the lines of force of the terrestrial magnetic field caused by the magnetic mass of a ship. The mine would explode when a metallic hull passed to a certain distance, without the requisite of making direct contact with the mine. This advantageous characteristic would allow to collapse a maritime sector with a notably lesser number of mines. But after the secret became revealed, the effectiveness of the tactic would be lost, since the British would demagnetize the hulls of their ships from that moment.

Cheap means of sinking a ship

Parts of a magnetic mine: 1 - Locking ring; 2 - Tail section equipped with stabilizing fins and parachute; 3 - Body; 4 - Magnetic sensor; 5 - Metallic capsule that protects the sensor

Cheap means of sinking a ship

Deployment of a magnetic mine: A - The mine, built like an aerial bomb, is dropped from an airplane and falls to the sea slowed by a parachute; B - The mine is dettached from the tail structure and the parachute by a mechanism when hitting the sea surface, and starts to dive; C - The mine lies on the seabed, being harder to spot than conventional floating mines, and a timer has activated the magnetic sensor; D - The mine explodes when the magnetic sensor senses a metallic hull at a certain distance

Pilotable torpedoes

A surprise assault should be able to achieve an effective result following the principle of economy of the forces used, hurting the enemy both materially and morally. Certainly the danger of receiving a cannon shot from the enemy is, in wartime, logical and accepted by the mariner; but the danger posed by a torpedo launched by a submarine keeps the nerves in tension because it is not known from where and when it can arrive. But at least, the submarine would commonly attack in the sea during the navigation, and it could even be harassed with depth charges after being detected. Which is the worst is the idea that a ship could be blown up in any moment, either while docked or while in navigation, despite the exhaustive vigilance and controls. Also, for these purposes is required highly specialized personnel who would be more useful in other place. It is enough to think about the first incursions from the Italian assault flotillas against Gibraltar and Alexandria; in each of these British ports had been organized a surveillance service which included, apart from the passive defenses (obstruction nets), sentinels in the docks, in the ships, in the port mouth and in speedboats which remained in constant movement, dropping explosive charges in the water every certain number of minutes.

Despite of that, the assailants belonging to the 10th Flotilla MAS (Motoscafo Armato Silurante or Torpedo Armed Motorboat), from the 15th March 1941 managed to bring their offensive to the heart of the enemy ports, to the point that the 8th September 1943 this bunch of men could register in their record five warships and 27 merchants, accounting for a total of 264792 tonnes sink or severely damaged. Let us see the equipment of these men and their most known assault mean: the "Maiale" (Pig). The assailants were provided with a normal diving set, upon which they wore a rubberized fabric suit known as "Belloni". They wore the appropriate footwear and only their hands and head were exposed to the water. The breathing device was one of oxygen with purifier filter of soda lime, granting six hours of operation. The mask was one of anatomical adaptation with independent lenses and incorporated mouthpiece. The dotation included also a wrist compass - properly isolated from the magnetic mass generated by the Maiale and other metallic parts - and a phosphorescent wrist watch. The Slow March Torpedo (official name of the Maiale) was just a 533-millimeter torpedo with some modifications, measuring 6.70 meters in length. The original engine, which granted high speed to the torpedo, was replaced by a slower one, fed by a 30-cell battery providing a total voltage of 60 volts. A rheostat allowed to regulate the speed, which could reach a maximum of five kilometers/hour. Operational range was about 20 kilometers. Two floodable tanks, placed in the aft and fore parts, allowed to bring the torpedo to the desired depth, which theoretically should not surpass 30 meters. The two operators sat straddled on the torpedo and were clung to the structures. The controls were in the fore part available for the pilot. In the fore end was the explosive head measuring 1.80 meters in length, loaded with 300 kilograms of explosive. Once detached, it would remain beneath the keel of the attacked ship with the timer fuses working, while the two operators escaped, either making use of the driving section of the Maiale or taking cover in the terrain.

Cheap means of sinking a ship

Remote-controlled boats

One of the tactics that had attracted the attention of the German Navy was the possibility of penetrating by surprise, with fast means, inside the Allied docks to sink the enemy ships by means of torpedoes or embarked artillery. Firstly it was considered to use an old motorboat, the Linse, capable of 35 knots (65 kilometers/hour) and loaded with 400 kilograms of high explosive. Theoretically, the Linse would have to be escorted until arriving to the enemy dock and then introduced inside via radio control, to approach the target ship and finally explode with the help of a remote detonator. The prime inconvenient was the speed: navigating at 35 knots, the Linse would be probably destroyed by the coastal defenses or the artillery from the warships before approaching the target. Hence, it would be necessary to have a faster boat to effectuate an action of this genre. Therefore it was projected the Tornado, a wide boat fitted with two floaters under the hull and propelled by the same rocket engine used in the flying bomb V-1. In the prow it would be installed a load of 700 kilograms of dynamite. This small boat could be remotely controlled or piloted by an operator who, some seconds before the impact, would abandon the boat and escape towards an ally escort ship. The Tornado would be much faster and more armed than the Linse, but it was difficult to obtain the engines, since these were reserved for the aforementioned missiles. Not discouraged by this, the technicians continued their experiments and, soon before the end of the war, they projected the Schlitten, a hydroplane propelled by an engine Ford V-8, capable of reaching a speed of 65 knots (120 kilometers/hour), and fitted with an explosive load of 700 kilograms, which could be remotely controlled or piloted by an operator. According to the technicians, this boat would be perfectly capable of completing its mission, but the end of the war arrived before than the chance to build and test some exemplars.

Cheap means of sinking a ship

The Linse.

Cheap means of sinking a ship

The Tornado.

Pocket submarines

A very practical system to attack anchored ships was the use of not only pilotable torpedoes but also pocket submarines. The interest for these vehicles was shared by the Germans and the Allies alike. In diverse occasions, the Royal Navy had the chance to use pocket submarines during the war, and Germans, Italians and Japanese made much use of them. The first German project of this type was the Hecht, a single-seater pocket submarine provided with a detachable warhead. They were built about 50 units which however served almost exclusively as experimental vehicles. The Hecht was fitted with an electric motor fed by batteries, which had nor the power neither the range necessary to undertake operative use, so the technicians projected a modified version, the Neger, propelled by a petrol engine. This one was projected in such a way than the engine and the pilot would take place in a sort of tubular hull, and the head of the pilot would remain above the surface of the sea. A torpedo would be placed beneath the pilot so this one could launch it easily. Whereas the Neger demonstrated to be perfect from a mechanical standpoint, it left much to be desired regarding another aspect: the pilot breathed pure oxigen and that restricted notably the operational range since there is a limit of time for the breathing of the oxigen. Because of this the Neger was modified so the pilot could benefit from a reserve of air; this new project was denominated Molch. It seems that, in 1944-45, many boats of this type were launched against Allied warships along Antwerp, but without success.

Cheap means of sinking a ship

The Hecht.

Cheap means of sinking a ship

The Molch.

The Molch was quickly replaced by a new model, the Marder, a similar boat to the former one, but capable of remaining submerged for brief time, allowing the pilot to cover the larger distance at sea level and to submerge in the moment of attacking. To allow this, the boat was fitted with two electric motors, which however demonstrated to be insufficient. The Marder was armed with a G7E 533 millimeters torpedo and about 300 units were produced. Provided now with a larger experience in building pocket submarines, the technicians decided to approach a more ambitious project: the Hai. This one was an oblong and single-seater pocket submarine powered by a petrol engine which conferred it the notable speed of 20 knots (37 kilometers/hour) while submerged. It was capable of remaining submerged for sixty hours, and navigating, always submerged, during circa two hours. It was used only experimentally and never took part in any war action. The successive model, the Biber, had 5.8 meters in length and a displacement of three tonnes, and it was armed with two torpedoes placed along the sides of the hull. Originally a single-seater, it was later converted into two-seater. Many units of this submarine took part in war actions in the estuary of the Scheldt and along the Russian coast.

Cheap means of sinking a ship

The Marder.

Cheap means of sinking a ship

The Biber.

Finally it came the Seehund, a two-seater pocket submarine displacing 15 tonnes and armed with two torpedoes placed in similar disposition as in the Biber. It was capable of a speed of 6 knots (11.1 kilometers/hour) while submerged and 8 knots (14.8 kilometers/hour) while surfaced. Fitted with an auxiliary tank - externally placed and which could be jettisoned if required - it reached an operational range of 500 nautical miles (930 kilometers). The Seehund was completed in 1944 and in 1945 it entered action in the estuary of the Scheldt, the estuary of the Thames and along Margate. The particulars of its warlike activity remained unknown because in 1945 the German informative services were in chaos, and it was only known that these boats managed to sink one or two Allied ships in the estuary of the Scheldt. Today it is known that from January to April 1945 they could have sunk as much as 120000 gross tonnes of shipping during the 142 sorties that they performed.

Cheap means of sinking a ship

The Seehund.

Article updated: 2015-06-12

Categories: Naval Warfare - Submarines - Engineering - World War Two - 20th Century


Website: Military History

Article submitted: 2015-06-12

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