The experts could work out the necessary trigonometry in their heads, and even take snap shots at rapidly moving targets. But the variables introduced by launching underwater with limited means of observation meant that far too often, and for far too many crews, the torpedo missed.
To restore the situation the submarine services introduced their own mechanical calculating machines. The model shown here is the US Navy’s torpedo data computer Mark 3, which with its predecessors helped the US submarine fleet wreak havoc with the Japanese naval and merchant fleet in the Pacific. (Details of the TDC Mark 3 models 5–8 and 10–12, can be found in the Bureau of Ordnance Pamphlet prepared in June 1944 by the Arma Corporation of Brooklyn, New York.)
The position keeper continually tracked the target ship and updated its actual position at all times in relation to the submarine. In order to do this it automatically received input of the boat’s own course from the gyro compass, and of the boat’s speed from the pit log. The hand cranks on the face of the TDC allowed for manual input of the target ship’s length, estimated speed, and angle on the bow. Sound bearings from the boat’s listening sonar were also automatically entered and taken into account in the calculations. Regular visual observations of the target’s actual position, speed and bearing could be fed into the machine to correct initial errors. Usually three or four observations were necessary to have confidence in the results.
The targeting part of the computer continually took the data from the position keeper and used it to work out the torpedo gyro angles to maximise the chances of a hit. As the data changed, so the gyro angles would be automatically updated. The machine was connected to the forward and aft torpedo rooms and input the gyro angles on all ten torpedo tubes by remote control.
The dual functionality of the TDC Mark 3 gave the US submariners a continuous firing solution; it was the only system at that time which both solved the gyro angle equation and also tracked the target in real time, and was thus way in advance of contemporary German and Japanese torpedo computers.
ROYAL NAVY TUBES IN HMS OCELOT
By way of comparison with the earlier systems described above, a submarine launch system from the Cold War period is visible inside HMS Ocelot, a diesel-powered boat preserved as a museum in Chatham Historic Dockyard. The colour photos are by the author, with the help of Scott Belcher, who kindly provided access. Note the substantial locking arrangements, which allowed these boats to fire their torpedoes from their maximum operating depth. The tube has eight aluminium bronze lands riveted to the inside to act as guides for the torpedo which is a free-floating fit inside the tube. The door is secured primarily by the large rotating ring on the end of the tube, but also by a safety bolt.
There was space forward for twelve torpedoes on three levels, mounted on racks which slid sideways to align with the tubes. With six loaded tubes, Ocelot carried a total of eighteen torpedoes. Her two shorter stern tubes had been intended for small anti-submarine torpedoes, but during her time in service the stern tubes were removed and the muzzle orifices plated over.
Ocelot was equipped with a Type 44 TDC, and before pressing his master firing buttons, her commander could call for a readout on the individual torpedo battery charge indicator board. If the electrical systems were out, the torpedoes could be fired manually from a seat squeezed in between the forward tubes.
CHAPTER 14
Torpedo Bombers and Stand-off Weapons
In naval warfare, the gun dominated for centuries, and held onto its leading position, even as newer weapon systems were threatening to dislodge the gun from its position of hegemony. The mine and the torpedo posed major threats to the battleship, and as aircraft developed, they came to add the threat of bombs and aerial torpedoes. While aircraft remained relatively fragile and underpowered, their bombs posed little threat to the largest dreadnoughts, free to manoeuvre in the open sea and capable of offering a powerful anti-aircraft defence. Torpedoes carried by aircraft, however, were to become as potent as any launched by surface and submarine craft.
In the late 1930s a British admiral and a high-ranking RAF officer argued out the respective merits of the torpedo and the bomb, or more specifically the bomb dropped from a dive-bomber. The admiral ended the discussion by noting that, ‘Bombs make holes in the tops of ships and let in air; torpedoes make holes in the bottoms of ships and let in water.’This was a slight over-simplification of the question, and many large warships would soon come to be sunk or disabled by bombs alone, but bombs could not on their own have accounted for the huge Japanese super-dreadnoughts Musashi and Yamato: they were both to be sunk by overwhelming aerial torpedo attacks.
One major problem remained to be solved: the airmen of all the combatants, German, British, Japanese or American, were exposed to suffering crippling losses when going in to attack with torpedoes at low altitude and on a steady approach run. They flew in the face of concentrated anti-aircraft fire, and their slow and heavily loaded torpedo planes often had to run the gauntlet of defending fighters. One suggested solution was to attack at night. But this brought serious problems of its own, as the reduced visibility would lower the chances of target acquisition, and most serious of all, would make the low, slow approach over the water extremely difficult to judge and therefore potentially fatal. The British Swordfish torpedo bombers that attacked Taranto were accompanied by Swordfish dropping flares for that very reason.
Night attack was in fact the preferred tactic of American Admiral Bradley A Fiske, who in 1912 had taken out US Patent № 1032394 dealing with a ‘Method of and apparatus for delivering submarine torpedoes from airships’. Three years later he proposed that torpedo bombers should carry out attacks at night, descending in a spiral dive and levelling out just 3–6m (10–20ft) above water level, releasing their torpedo at a range of 1400–1800m (1500–2000yds) from the target vessel. He concluded that if there was enough room the torpedo planes could attack vessels inside their harbours. Truly prophetic ideas.
EARLY TORPEDO BOMBERS
The very first successful torpedo drop from an aircraft was carried out on 28 July 1914, from a Short seaplane based at Calshot. A year later the carrier Ben-My-Chree ferried a flight of Short 184 seaplanes to the Dardanelles. Three Turkish ships were sunk by 14in torpedoes, one when the seaplane was waterborne. But the Short 184s were patently underpowered for the task, and a larger, more powerful aircraft, the Short 320, was built to replace it.