Human Torpedo in Use by the Israeli Commando Unit, 1967

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 (with a larger version) Britain, deployed in the Mediterranean and used to attack ships in enemy harbors. The human torpedo concept has occasionally been used by recreational divers.

Israeli manned torpedo, 1967.

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 (or other breathing gas) supply so its riders do not have to drain their own apparatus while they are riding it. 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 (if used). There are flotation tanks (typically four: left fore, right fore, left aft, right aft), which can be flooded or blown empty to adjust buoyancy and attitude.

The concept of a tiny 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 as early as 1918 and this craft did have some success. The first truly practical human torpedo was the Italian Maiale (nicknamed the “pig” because it was difficult to steer) used in the Second World War.

Manned torpedo, called Maiale, at the Museo nazionale della scienza e della tecnologia Leonardo da Vinci of Milan.

The Maiale was electrically propelled by a 1.6 horsepower (1.2 kW) motor in most of the units manufactured, with a top speed of 3 knots (5.6 km/h) and often required a travel time of up to two hours to 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 15 meters (49 ft), and hypothetically to 30 meters (98 ft), 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 11 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 a Lenta Corsa (SLC or “Slow-running torpedo”). Two distinct models were made, Series 100 and then (in 1942) Series 200 with some improvements. At least 50 SLCs were built by September 1943.

A maiale in Taormina, Sicily.

In operation, the Maiale torpedo was carried by another vessel (usually a conventional submarine), 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 (Regia Marina) successfully forced the harbor of Alexandria and damaged the two British battleships HMS Queen Elizabeth and HMS Valiant, as well as the tanker Sagona. This feat encouraged the British to develop their own torpedo “chariots”.

The last Italian model, the SSB (for Siluro San Bartolomeo, “San Bartolomeo Torpedo”) was built with a partly enclosed cockpit, a more powerful motor and larger 300 kg (660 lb) warhead (up from the earlier SLC’s 220 and 250 kg (490 and 550 lb) warheads). Three units were made but not operationally used because Italy surrendered in 1943.

A captured Kaiten torpedo at the USS Bowfin Museum in Hawaii.

The first British version of the concept was named the Chariot manned torpedo. Two models were made; Mark I was 20 feet (6.1 m) long while Mark II was 30 feet (9.1 m) long, both suitable for carrying two men. Later versions were larger, starting with the original X-class submarine, a midget submarine, 51 feet (16 m) long, no longer truly a human torpedo but similar in concept. The X-Craft were capable of 6.5 knots (12.0 km/h) on the surface or 5.5 knots (10.2 km/h) submerged. They were designed to be towed to their intended area of operations by a full-size 'mother' submarine.

A Mk.I Chariot (minus warhead), 3 March 1944, Rothesay. (© IWM)

Chariot Mk 1 and crew. 3 March 1944, Rothesay.

The German navy also developed a manned torpedo by 1943, the Neger, intended for one man, with a top speed of 4 knots (7.4 km/h) and carrying one torpedo; the frequent technical problems often resulted in the deaths of operators. Roughly 40 of these were made and they did manage to sink a few ships. The later Marder (pine marten in English) was about 27 feet (8.2 m) long and more sophisticated and could dive to depths of 27 meters (89 ft) but with very limited endurance. About 500 were built.

A Neger with its operator being launched, ca. 1944–45.

(via Wikipedia)