Human torpedo

Human torpedoes or manned torpedoes are a type of diver propulsion vehicle on which the diver rides, generally in a seated position behind a fairing. They were used as secret naval weapons in World War II. The basic concept is still in use.
The name was commonly used to refer to the weapons that Italy, and later Britain, deployed in the Mediterranean and used to attack ships in enemy harbours. The human torpedo concept has occasionally been used by recreational divers, although this use is closer to midget submarines.
More broadly, the term human torpedo was used in the past to refer to vehicles which are now referred to as wet submarines and diver propulsion vehicles. Midget submarines which are employed to directly support frogman operations, whether possessing airlocks or not, if used as underwater tugs to transport equipment and frogmen clinging to their exterior, also blur the line between the human torpedo and more sophisticated underwater vehicles.File:Maiale at gosport.jpg|thumb|A maiale at the Royal Navy Submarine Museum, Gosport

History of common wartime models

The concept of a small manned submarine carrying a bomb was developed and patented by a British naval officer in 1909, but was never used during the First World War. The Italian Navy experimented with a primitive tiny sub carrying two men and a limpet mine: this craft successfully sank the Austro-Hungarian battleship SMS Viribus Unitis on 1 November 1918.
The first truly practical human torpedo was the Italian maiale, electrically propelled by a motor in most of the units manufactured. With a top speed of, it often took up to two hours to reach its target. Two crewmen in diving suits rode astride, each equipped with an oxygen rebreather apparatus. They steered the craft to the enemy ship. The "pig" could be submerged to, and hypothetically to, when necessary. On arrival at the target, the detachable warhead was released for use as a limpet mine. If they were not detected, the operators then rode the mini sub away to safety.
Development began in 1935 but the first eleven were not completed until 1939 by San Bartolomeo Torpedo Workshops in La Spezia, Italy and a larger number followed. The official Italian name for the majority of the craft that were manufactured was Siluro Lenta Corsa. Two distinct models were made, Series100 and then Series200 with some improvements. At least 50 SLCs were built by September 1943.
In operation, maiali were carried by another vessel, and launched near the target. Most manned torpedo operations were at night and during the new moon to cut down the risk of being seen. Attacks in 1940 were unsuccessful but in 1941, the Italian navy successfully entered the harbour of Alexandria and damaged the two British battleships and, as well as the tanker Sagona. This feat encouraged the British to develop their own torpedo "chariots".
The last Italian model, the SSB was built with a partly enclosed cockpit, a more powerful motor and larger warhead. Three units were made but not operationally used because Italy surrendered in 1943.
The first British version of the concept was named the Chariot manned torpedo. Two models were made; MarkI was long while MarkII was long, each suitable for carrying two men. Later versions were larger, starting with the original X-class submarine, a midget submarine, long, no longer truly a human torpedo but similar in concept. The X-Class were capable of on the surface or submerged. They were designed to be towed to their intended area of operations by a full-size 'mother' submarine.
The German navy also developed a manned torpedo by 1943, the Neger, intended for one man, with a top speed of and carrying one torpedo; the frequent technical problems often resulted in the deaths of operators. Roughly 200 of these were made and they did manage to sink a few ships. The later Marder was about long and more sophisticated and could dive to depths of but with very limited endurance. About 500 were built.

Construction

A typical manned torpedo has a propeller, hydroplanes, a vertical rudder and a control panel with controls for its front rider. It usually allows for two riders who sit facing forwards. It has navigation aids such as a compass, and nowadays modern aids such as sonar and GPS positioning and modulated ultrasound communications gear. It may have an air supply so its riders do not have to drain their own apparatus while they are onboard. In some the riders' seats are enclosed; in others the seats are open at the sides as in sitting astride a horse. The seat design includes room for the riders' swimfins. There are flotation tanks, which can be flooded or blown empty to adjust buoyancy and attitude.

Timeline

1909: The British designer Commander Godfrey Herbert received a patent for a manned torpedo. It was rejected by the War Office as impracticable and unsafe.
1 November 1918: Two men of the Regia Marina, Raffaele Paolucci and Raffaele Rossetti, in diving suits, rode a primitive manned torpedo into the Austro-Hungarian Navy base at Pola, where they sank the Austrian battleship and the freighter Wien using limpet mines. They had no breathing sets so they had to keep their heads above water, and thus were discovered and taken prisoner.
1938: In Italy the "1^a Flottiglia Mezzi d'Assalto" was formed as a result of the research and development efforts of two men – Major Teseo Tesei and Major Elios Toschi of the Italian Royal Navy. The pair resurrected the idea of Paolucci and Rossetti.
1940: Commander Vittorio Moccagatta of the Italian Royal Navy reorganised the 1st Fleet Assault Vehicles into the Decima Flottiglia MAS or "X-MAS", under the command of Ernesto Forza. It secretly manufactured manned torpedoes and trained war frogmen, called nuotatori.
26 March 1941 The Raid on Souda Bay was an attack by the Decima MAS. Decima MAS used explosive boats against British ships lying in Souda Bay, Crete, during the early hours of 26 March 1941. The MTM explosive boats had been ferried from Astypalaia by the destroyers Francesco Crispi and Quintino Sella and launched at the approaches to the bay. After crossing the three boom defences, the MTM attacked the British heavy cruiser and the Norwegian tanker Pericles.
26 July 1941: An attack on Valletta Harbour ended in disaster for the X MAS and Major Teseo Tesei lost his life.
19 December 1941: The Decima Flottiglia MAS attacked the port of Alexandria with three maiali. The battleships and were sunk in shallow water putting them out of action for many months. Luigi Durand de la Penne and five other swimmers were taken prisoner. De la Penne was awarded the Gold Medal of Military Valour after the war.
October 1942: Two British Chariot manned torpedoes were carried aboard the Shetland bus fishing-boat Arthur to attack the on Operation Title. They were swung overboard once in Norwegian waters but both became detached from their tow hooks in a gale and the operation was a total failure.
8 December 1942. An attack by three manned torpedoes from the against British naval targets was thwarted in Gibraltar. Three divers were killed by depth charges when the British harbour defence "reacted furiously" to the attack. Among the dead were Lieutenant Licio Visintini, commander of the divers unit on board the Olterra, Petty Officer Giovanni Magro, and Sergeant Salvatore Leone, from Taormina, Sicily. Leone's body was never found. Sergeant Leone was awarded the Medaglia d'oro al Valor Militare and a memorial was erected in the Community Gardens in Taormina on the 50th anniversary of the attack. The memorial includes a rebuilt maiale and a description of the events, in three languages.
1–2 January 1943: British submarines, and took part in Operation Principal. P311 was lost en route to La Maddelena but the other two boats had some success at Palermo, launching two and three Chariots respectively. The Ulpio Traiano was sunk and the stern torn off Viminale. However the cost was high with one submarine and one chariot lost and all but two charioteers captured.
18 January 1943: Thunderbolt took two chariots to Tripoli for Operation Welcome. This was to prevent blockships being sunk at the harbour mouth, so denying access to the Allies. Again, partial success was achieved. This was the last operation in which chariots were carried in containers on British submarines, although some others followed with the chariots on deck without containers.
6 May & 10 June 1943: Italian maiali from the Olterra, now under the command of Lieutenant Ernesto Notari, sank six Allied merchant ships in Gibraltar, for a total of 42,000 tons.
September 1943: Operation Source was an attempt to destroy warships including the Tirpitz using X-class midget subs. Of the five deployed, only two were successful. Tirpitz was badly damaged, crippled, and out of action until May 1944.
2 October 1943: A bigger Italian frogman-carrier, long and carrying four frogmen, called Siluro San Bartolomeo, or SSB, was going to attack Gibraltar, but Italy surrendered and the attack was called off.
21 June 1944: A British-Italian joint operation was mounted against shipping in La Spezia harbour. The chariots were carried on board an MTB and the cruiser Bolzano was sunk.
6 July 1944: A German Neger-type vessel torpedoed the Royal Navy minesweepers and Cato.
8 July 1944: A German Neger-type torpedo manned by Lieutenant Potthast heavily damaged the Polish light cruiser off the Normandy beaches.
20 July 1944: Royal Navy destroyer was mined at anchor in Seine Bay. A German human torpedo was believed responsible.
27–28 October 1944: The British submarine carried two Mk 2 Chariots to an attack on Phuket harbour in Thailand. See British commando frogmen for more information about this attack. No manned torpedo operations in combat in any war are known with certainty after this date.
20 November 1944: The USS Mississinewa was sunk by a Japanese kaiten manned suicide torpedo.
Immediate post-war period: The British Chariots were used to clear mines and wrecks in harbours.

For other events, see Operations of X Flottiglia MAS and British commando frogmen.
Some nations including Italy have continued to build and deploy manned torpedoes since 1945.