CHAPTER X

THE SUBMARINE TORPEDO

The submarine torpedo has become one of the principal naval arms. Not only does it supply the chief offensive power of the submarine, the torpedo-boat and the destroyer, but it is also carried as a separate arm, with a special highly-trained crew, by almost every warship afloat. At the beginning of hostilities the Naval Powers engaged owned considerably over 80,000 of these weapons, and _one_ factory in England alone can make them at the rate of two a day. During the first few weeks of the _Great War_ the torpedo was responsible for the sinking of warships to the value of over one million sterling. Had the German Fleet been on the high seas instead of in harbour and protected from torpedo raids by carefully-prepared submarine defences, there is little doubt but what several more of the enemy’s ships would have been sunk by this weapon. The fact that at first the British light cruisers suffered rather heavily—though in total loss of ships and men less than the German Navy—does not point to any advantage derived either from the type of torpedo used or from skill in this mode of warfare possessed by the Germans, but clearly to the timidity of the German main fleet, which was at the very beginning of hostilities withdrawn from the zone of war and placed behind fortifications, where it was safe from torpedo attack. The British Fleet, true to the policy of “attack and not defence,” began operations the moment war was declared, with results so brilliantly successful, and of such far-reaching and world-wide importance, that enumeration is well-nigh impossible. But while all these operations were in progress the British Fleet was more or less exposed to torpedo attack by any hostile submarines or fast surface craft which might succeed in getting past the cordon of protecting destroyers, while the German Fleet was safe, but ignominiously impotent. That the naval losses of Great Britain, with all her fleets at sea, have not been far greater than they have is in itself a victory of the greatest magnitude—a victory due entirely to consummate naval skill.

The modern torpedo varies in length from 14 to 19 feet, and weighs up to half a ton. It has an extreme range of 4,000 yards, or just over 2 ¼ miles. There are three types of torpedoes in use by the fleets at war. The British use the _Whitehead Torpedo_, the French the Whitehead and the _Schneider_, the Russians and the Japanese use the Whitehead; the Germans have a type of their own, known as the _Schwartzkopf_, and the Austrian arm is principally the Whitehead. All these types are alike in their essential features, and therefore need not be described separately.

The latest pattern 18-inch Whitehead torpedo is propelled by compressed air stored in that section of the weapon known as the _air-chamber_ (see diagram). The air on being released is heated and expanded in a tiny three or four-cylinder engine which operates twin screws, moving “clockwise” and “anti-clockwise.” The “war-head” contains about 200 pounds of wet gun-cotton which is exploded on the torpedo striking an object. The essential features of the Whitehead torpedo are shown in the diagram.[9]

This torpedo maintains a speed of 42 knots for 1,000 yards, 38 knots for 2,000 yards, 32 knots for 3,000 yards, and 28 knots for 4,000 yards. Thus, if discharged at a distance of half a mile it reaches its object in about 45 seconds.

Torpedoes are fired—or ejected—into the sea from surface or submerged tubes, and on striking the water are propelled by their own engines in an absolutely straight course towards the target. The exact mechanism of the submerged tube—which is used in surface warships as well as in submarines—is a naval secret. When fired from a surface tube the torpedo sinks immediately to a depth of about 10 to 14 feet, and maintains this depth until it strikes its object. When fired from a submerged tube it rises—if necessary—to the same level. A torpedo always proceeds towards its object of attack at a depth of a few feet below the surface. This, combined with speed, renders it almost impossible to destroy an approaching torpedo by gun-fire. So marvellous is the mechanism of these little weapons that in anything like favourable circumstances they may be _depended upon_, if well aimed, to strike within a yard or two of the spot aimed at. This accuracy is due almost entirely to the gyroscope, which, briefly described, is a rotating wheel automatically controlling the torpedo’s course.

Although for many years torpedoes have been carried by nearly all types of service warships, none of them were really ideal for this kind of warfare. A new field for the torpedo was, however, opened out by the introduction of the submarine boat. In order to be effective the torpedo must be discharged from a distance under 4,000 yards—preferably from a point less than half this distance from the object of attack. This means that the vessel carrying the torpedo would have to get within a mile, or at least a mile and a-half, of her object of attack before discharging a torpedo. For a surface vessel to accomplish this in the face of a heavy cannonade from quick-firing guns would be extremely risky. To make a quick rush to close quarters, if possible, by several vessels from different points, was the only chance of delivering a successful torpedo attack on a hostile warship; unless, of course, she was favoured by fog or darkness _at the right moment_—favourable conditions which would seldom obtain in actual warfare. Again, every increase in the speed of the big surface warship rendered the task of the ordinary torpedo-boat and destroyer more difficult because in the event of a threatened attack the larger vessel would make use of her speed to keep out of torpedo range while her powerful guns were repelling the attacking torpedo-boat.

The _hour_ of the torpedo came with the _perfection_ of the submarine. All the conditions of an ideal torpedo-boat were fulfilled—_invisibility_ rendering daylight attacks possible; _almost perfect immunity from gun-fire_ enabling the torpedo to be discharged at closer range; _submerged discharge_ removing the likelihood of the weapon being exploded by accurate gun-fire before being discharged; _speed on the surface_ enabling the “carrying” vessel to manœuvre for position; _moderate speed when submerged_ enabling an attack under all reasonably tactical conditions; and _comparatively large displacement_ giving good cruising qualities, wide range of action, and enabling a large number of torpedoes and tubes being carried.

Footnote 9:

“Submarines of the World’s Navies,” By Charles W. Domville-Fife. (London: Francis Griffiths.)