Torpedo. The term torpedo is now used to denote a submarine weapon of offence, carrying a charge of gun-cotton or other explosive, and possessing powers of locomotion, in distinction to a submarine mine (see MINES), which is stationary and used for defensive purposes. Torpedoes may be divided into two classes: (1) Uncontrollable, being those which carry within themselves their own motive power, and which after being once started are no longer under the control of the operator; and (2) Controllable—i.e. those whose motive power is under the control of the operator, who can by electricity or other means direct the movements of the torpedo during its run. Of the first the best-known examples are the Whitehead and the Howell; and of the second the Brennan, Sims-Edison, and Lay. Of these the most important is the Whitehead, which dates from about 1867.
The general arrangement of this weapon is shown in the figure: it is cigar-shaped, made of steel or bronze, and varying from 12 to 18 inches in diameter, and from 10 to 16 feet 6 inches in length, the most common size being 14 inches in diameter and 14 feet 6 inches long. The head A is conical and contains the charge of gun-cotton, which in the 14-inch torpedo varies from 32 lb. in the earlier patterns to 70 lb. in the later ones. The pistol, P, on coming in contact with the enemy's ship is driven back on to a small charge of fulminate of mercury which detonates the gun-cotton. B is the air-chamber which contains the compressed air for driving the engines. The air is forced into this chamber by means of air-pumps to a pressure of ninety atmospheres. C is the balance chamber, and contains the mechanism by which the depth of the torpedo below the surface is regulated during its run. The depth of the torpedo can be adjusted before starting to any required amount between 5 and 20 feet. In D are the engines worked by the compressed air. E is the buoyancy chamber. F is the tail, consisting of two screws placed one in front of the other for propelling the torpedo, two small vertical rudders which are adjusted by experiment to keep the torpedo running in a straight line, the horizontal rudders which are controlled by the mechanism in the balance chamber and which keep the torpedo at the depth for which it has been set, and four fins, two horizontal and two vertical, to prevent rolling.
The torpedo is discharged from a tube either above water or below the water-line. In the latter case special arrangements are made. In above-water tubes the torpedo fits the tube like a projectile in a gun, and is ejected either by a small charge of powder or by compressed air. As the torpedo leaves the tube the valve controlling the supply of air to the engines is opened, and the torpedo on entering the water is propelled by its own engines. A safety arrangement on the pistol prevents the latter exploding the charge by accident until the torpedo is clear of the ship. The speed of the later patterns of 14-inch torpedoes is 26 knots for 600 yards. In action it can be adjusted to sink at the end of its run in the event of its missing its object, and when used for exercise it is adjusted to float, and can then be picked up and used again. For various reasons it is considered that the effective range of a Whitehead torpedo is not more than 400 yards, and although the torpedo is capable of going much farther, it is desirable, in order to ensure a fair measure of success, not to discharge the torpedo until within that distance of the enemy.
The position which the Whitehead torpedo is destined eventually to take in naval warfare is to a great extent a matter of speculation. There have been instances in recent wars where it has been used with success even with the inferior weapons and apparatus then in use. On the other hand, torpedoes occasionally take most erratic courses, and no one can predict with certainty what direction one will take. Moreover, in consequence of the slow speed of a torpedo as compared with a projectile, and also on account of the deflection it receives on entering the water, it is necessary in discharging it to take into consideration the speed of one's own ship and also the speed and course of the enemy; and as the two latter must necessarily be more or less guess-work, an additional element of error is introduced. Another objection, the importance of which can only be determined in war time, is that during the time the torpedo is waiting to be discharged the charge is liable to be detonated by an enemy's shot, the results of such an accident being obviously of a most disastrous character. The torpedo is, however, at present recognised as a most important element in naval warfare, and its use must of necessity be continued until war has decided definitely in its favour or otherwise. A very much more powerful type of Whitehead is 18 inches in diameter, carrying a charge of about 200 lb. of gun-cotton, and having a speed of about 30 knots for 800 yards. Torpedoes are now usually discharged below, not above, water.
The Howell torpedo may be described as in shape similar to the Whitehead, and is propelled by screws to which motion is imparted by means of a heavy flywheel in the interior of the torpedo which is spun up to 10,000 revolutions a minute, before discharging, by means of suitable machinery. This wheel, in addition to providing the requisite energy, also acts as a gyroscope, the result of which is that the torpedo continues to run in the direction of the line of fire, and cannot be deflected from its course. The application of the gyroscopic principle to torpedoes is new and ingenious, and its development will be watched with interest. The charge is exploded on contact.
The Brennan torpedo carries inside it two drums on which are wound piano wire which, passing out of the rear of the torpedo, is connected with powerful engines on shore. On these being started the wire is reeled off the drums in the torpedo, the motion of the drums being imparted to the screws. The faster the wire is reeled up on shore, the faster will the torpedo go ahead. Steering is effected by checking one or other of the wires which actuate vertical rudders on the torpedo. The charge is exploded on contact, and the range is a mile or more.
The Sims-Edison torpedo consists of a 'float' to which is suspended the torpedo so that it is about 6 feet below the surface. The motive power is supplied by an electric motor in the torpedo worked from a generator at the base through an electric cable which is paid out as the torpedo advances.
The Lay torpedo is propelled by carbonic acid gas contained in the torpedo under pressure, the engines being controlled by the operator through an electric cable. The charge in both these torpedoes is exploded by electricity at will, and the speed in each is about 10 or 11 knots for one mile.
The three last torpedoes are connected to the base from which they start, by means of wires, and it would be a matter of very great difficulty to control these torpedoes, and to direct their course so as to strike any particular object, if they were used from a moving base. Hence any proposals to use them on board ship have not so far met with much favour, and it is unlikely that this class of torpedo will ever be used except from forts or fixed stations on shore.
The Outrigger torpedo is used from steam pinnaces, and consists of a charge of gun-cotton placed at the end of a pole about 40 feet long, which projects over the bows of the boat, the charge being about 10 feet below the surface when in position. The boat in making an attack has to bring the charge in contact with the bottom of the enemy's ship, and it is then exploded by electricity. A notable instance of the success of this method of attack occurred during the American civil war; but under present conditions an attack on a modern ship with the outrigged torpedo must be regarded as impracticable except under very exceptional circumstances.
Torpedo Boats.—If a large ship is to be attacked by a comparatively small boat, the latter, in order to have any chance of success, must be as nearly invisible as possible, and must possess a high speed. Torpedo boats designed to fulfil these requirements vary considerably in size, but may be broadly divided into two classes—those which can be carried on board large ships, and which are therefore limited in size and possess small sea-going powers; and those which can take the sea and act independently. The two classes are similar in construction, being built of the lightest steel, low in the water, and with most of the available space occupied by the engines and apparatus connected with the torpedoes. The former class are about 60 feet in length, 15 knots speed, and carry a crew of eight men. The latter range from 100 to 150 feet in length, have a nominal speed of from 19 to 22 knots, which in practice rarely exceeds 17 to 20 knots, and carry a crew of from sixteen to sixty men, with three to five torpedoes, and also a small gun armament.
There is also an intermediate class of vessel, known as torpedo-boat destroyers, carrying an armament of machine guns and torpedoes. These vessels are of high speed, and their superior size and sea-going qualities enable them to maintain their speed in the open sea far better than a torpedo boat, whilst their powerful armament would render them formidable opponents even to large ships.
For torpedo-nets, see NAVY, Vol. VII. p. 421. For part of the history of submarine warfare, see SUBMARINE NAVIGATION. See also Sleeman's Torpedoes and Torpedo Warfare (1880; 2d ed. 1889).