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.

Sketch showing the essential parts of a Whitehead torpedo. A. Pistol, detonator, primer, which causes the explosion of “B” when the torpedo strikes an object. B. Explosive head, filled with wet gun-cotton. (The “war-head” is substituted by a weighty dummy during practice.) C. Air chamber with compressed air, at a pressure of approximately 1350 lbs. per square inch, for action. The chamber is tested to stand a pressure of 1700 lbs. per square inch. D. Balance chamber, containing mechanism for regulating the depth of submergence at which the torpedo is adjusted to run. E. Engine-room, containing propelling machinery (I.H.P. 60 in latest 18-in. type). F. Buoyancy chamber—a practically empty chamber—to give the necessary buoyancy to the torpedo. G. Gyroscope. An instrument for correcting any deviation of the torpedo from the line of fire. H. Rudders, and mechanism for operating. I. Twin-screws, operating “clockwise” and “anti-clockwise.”

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.

CHAPTER XI
SUBMARINE MINES

If the Russo-Japanese war was the first to fully demonstrate the value of the explosive mine, the Great European Conflict has certainly brought this weapon to the forefront in the rapidly growing science of submarine warfare. During the first few weeks of the naval fighting several warships, beginning with H.M.S. Amphion, and many merchant vessels representing millions of pounds sterling, were destroyed by these weapons. Had it not been for the foresight of the British Admiralty in providing a very large fleet of mine-sweepers, aided by seaplanes, there can be no doubt but what the shipping of all countries—neutrals and belligerents alike—would have suffered far greater losses.