In retrospect, the Harvey was a workable weapon system, but it had the misfortune to arrive on the scene at the same time as the much superior Whitehead.
STEALTH WEAPONS: MIGNATTA, BARCHINO SALTATORE, SLC MAIALE, CHARIOT, NEGER AND KAITEN
Fulton had finally been forced to abandon the concept of a stealth attack weapon, lacking the necessary power source to guarantee mobility and accurate delivery of the warhead. Instead he turned to relatively complicated fixed mines for coastal defence. But a century later, inventive minds revived his stealth weapon concept, and brought new power sources to bear to make them a practical proposition.
In 1909, Lieutenant Godfrey Herbert of the Royal Navy, former second-in-command of Nasmith’s submarine A 4, and serving in surface ships before returning to submarines, patented the idea of a manned torpedo. The Admiralty of the day dismissed it as impractical and unsafe. His idea was to see form in the hands of the Italian navy.
In 1918 the first ‘human torpedo’ arrived on the scene in a dramatic manner, operated by two Italian naval officers. Major of Naval Engineers Raffaele Rossetti had designed a ‘Mignatta’ (Italian for ‘leech’), using components from a standard Italian Navy B57 Model 14in torpedo.
At the same time Physician Sub Lieutenant Raffaele Paolucci had conceived the idea of walking on the seabed into an enemy anchorage, dragging behind him an explosive charge. He trained for such an action, walking long distances on the seabed wearing a diving suit and dragging behind him a length of iron to represent the charge.
Bringing these two ideas together, Rossetti conceived and built the definitive Mignatta, which ended up 8m (26ft) long with a diameter of 600mm (24in). Powered by compressed air, it was driven by two four-bladed contra-rotating propellers at a slow speed of 2 knots, for a maximum distance of 16km (10 miles). There was no mechanical means of steering: the crew had to direct it by extending their arms and legs. Without breathing apparatus they were obliged to keep their heads above water. The warhead was composed of two detachable charges, each one containing 175kg of explosive and provided with clockwork fuses giving a delay of up to six hours.
The scale drawing of the Mignatta shows the two detachable explosive charges. When the second charge has been detached, in front of the central air flask was a second streamlined nose cone, to allow the operators to use the Mignatta to make good their escape. Inside the tail unit are the mechanical parts of the 14in torpedo, with the three-cylinder engine and propeller shaft to the contra-rotating gears in the tail. Note the complete lack of rudders and horizontal tail planes. What appears to be a handhold at the top rear is in fact the compressed air pipe to the engine, carried outside the hull to impart some heating from the surrounding seawater.
Despite the apparent crude nature of the Mignatta, against all expectations Rossetti and Paolucci succeeded in entering Pola harbour on the night of 1 November 1918, even dragging their Mignatta over the harbour defence boom and then over a protective gate. Having attached one of the charges to the Austro-Hungarian flagship Viribus Unitis, they were spotted and were forced to scuttle their Mignatta. Taken on board the target vessel as prisoners, they were surprised to learn that the very day they had set out on their mission, the Viribus Unitis had been handed over to the newly formed Yugoslav National Council and renamed Jugoslavia. The change of nationality did not save the ill-fated vessel, and when the charge exploded she capsized and sank to the harbour bottom.
A very different kind of stealth weapon had already been tried out by the Italian navy, with their ‘barchino saltatore’, or ‘jumping boat’, also known as the sea tank from its pair of caterpillar tracks. Driven by electric motors, these assault boats were intended to climb the Austro-Hungarian net boom harbour defences to attack their fleet at anchor, with the two 450mm torpedoes carried in drop collars. The 16m long boats could proceed at a speed of 4 knots for up to 30 nautical miles. With a crew of four, they were carried to the chosen target by mother craft.
Designed by Attilio Bisio of the SVAN Company that built them, a total of four were commissioned by the Italian navy in March 1918. Cavalletta and Pulce were scuttled during an abortive attack on Pola on 13 April 1918. A month later, the third boat Grillo attempted to enter Pola harbour but was spotted and fired upon. Abandoned by her crew, she sank, but was recovered by the Austrians. The latter were so impressed by the Italian boat that they planned to build a close copy and carry out attacks of their own on Italian bases. The war ended before they could put this plan into operation. The fourth ‘barchino’, Locusta, saw no action and was scrapped in 1921.
During the late 1930s two captains in the Genio Navale (the Italian navy’s engineering corps), took up Rossetti’s Mignatta and redesigned it to produce the SLC (‘silura lenta corse’, or ‘slow-speed torpedo’). In the hands of the famous elite unit Decima MAS (literally, the 10th Motor Torpedo Squadron), the whole balance of naval power in the Mediterranean was altered by these tiny units when SLCs put out of action the rebuilt Royal Navy battleships Queen Elizabeth and Valiant in Alexandria harbour on the night of 19 December 1941.
They were, however, extremely difficult to control, having a tendency to roll, and the crews’ exertions were not helped by the clumsy suits and breathing gear. These problems were carried over into the British copy of the SLC, the Chariot. A detailed description of the Chariot, plus the construction of a working replica, can be found on the website, www.divingheritage.com/torpedo.htm, hosted by Phil Nussle.
In October 1943 the Regia Marina had built three examples of a much larger SLC, the SSB (‘siluro San Bartolomeo’), which they planned to use in an attack against shipping in Gibraltar, but the plan was overtaken by the Italian surrender. Instead of riding astride the torpedo, the crew now sat in a cockpit area well furnished with controls and instruments. A surviving example of a San Bartolomeo can be seen today in store at Explosion, the Museum of Naval Firepower in Gosport, and a second one is on display at the Historic Ship Nautilus and Submarine Force Museum, Groton, Connecticut.
The German Kriegsmarine went further than the Italians and the British, in producing the ‘Neger’, a form of human torpedo which transported and launched a second torpedo, the pilot then hopefully returning to his base. In reality, his chances of surviving an attack on an Allied invasion fleet — their intended target — were at best slim: the clumsy combination was difficult to control, and the pilot’s vision was extremely limited as the Neger lacked even the simplest of periscopes. To navigate he had therefore to keep the Perspex dome surrounding his head and shoulders above water, which made his craft easy to detect by enemy lookouts. The tiny cockpit cannot have helped.