A. Introduction
B. Head section of a Mark 15 type torpedo
C. Air system of a Mark 15 torpedo
D. Superheating system of a Mark 15 torpedo
E. Main engine of a Mark 15 torpedo
F. Control systems of a Mark 15 torpedo
G. Tail section of a Mark 15 torpedo
H. Aircraft torpedos
I. Other types of torpedoes
J. Above-water torpedo tubes

A. Introduction

12A1. General

A torpedo is a self-propelled underwater weapon that carries a high-explosive charge to its target. A torpedo can do more damage than a projectile from the biggest guns on a battleship. There is more explosive in a torpedo war head than there is in any projectile.

The torpedo war head explodes under water, and that increases its destructive effect. When a projectile explodes, a part of its force is absorbed by the surrounding air. But when the torpedo war head explodes. the water transfers almost the full force of the explosion to the hull of the target ship. Thus, even if a projectile could carry the same amount of explosive, the torpedo would do more damage.

The torpedo makes it possible for small ships to carry heavy armament. But of course it can not make a small ship the equal of a large one in combat. A torpedo moves slowly compared to a projectile, and its effective range is much shorter.

12A2. Applications

The torpedo is an important weapon of destroyers, destroyer escorts, and frigates. Torpedoes are the principal armament of PT boats and submarines, and, under certain conditions, of aircraft. The tactical use of torpedoes is gradually changing; their use in surface engagements is less frequent than it was a number of years ago. The outcome of a battle is likely to be decided before the enemy is within torpedo range. Even so, the ability of a destroyer to launch torpedoes serves as a constant threat to the enemy, and thus limits the range of maneuver available to him.

When aircraft approaches a surface ship within torpedo-launching range. it is vulnerable to antiaircraft fire. In future warfare, it is likely that both destroyers and torpedo planes will use guided missiles against surface targets. The missiles will carry torpedoes to within launching range of the enemy.

While it is submerged, a submarine is not vulnerable to gunfire. A submarine can often approach within torpedo range of its target before its presence is detected. Torpedoes will therefore continue to be the principal armament of submarines in the foreseeable future.

Homing torpedoes are a relatively recent development; they have been perfected since the end of World War II. With homing torpedoes, a destroyer can attack a submerged submarine, even when its exact position and depth are unknown. The homing torpedo is becoming increasingly important as a weapon with which one submerged submarine may attack another.

12A3. Launching methods

There are two principal ways to launch a torpedo— by firing it from a tube, or by dropping it from a rack.

PT boats launch torpedoes from racks at the sides of the boat. A PT boat may carry from 2 to 4 torpedoes.

Aircraft drop torpedoes from launching racks; usually, an aircraft carries only a single torpedo.

Older destroyers carry 5 torpedoes, in a tube mount that consists of 5 barrels side by side. The tube mount is carried amidships. It can be trained through a wide arc, so that torpedoes may be fired from either side of the ship. Impulse charges of black powder are used to expel the torpedoes from the tube mount with enough force to clear the firing ship.

Newer destroyers, destroyer escorts, and frigates are fitted with fixed, non-trainable tubes—usually four of them. The tubes are located below the weather deck with their muzzles extending through the sides of the deck house. Torpedoes are expelled from these tubes by compressed air.

Submarines fire torpedoes from fixed, below-water tubes. The fleet-type submarine is fitted with 10 tubes—6 in the bow and 4 in the stern. On firing, the torpedoes are expelled from the tubes by compressed air. Spare torpedoes are carried in ready racks near the tubes. A submarine on war patrol will usually put to sea with a load of 28 torpedoes aboard.

12A4. Requirements of a torpedo

As previously stated, a torpedo is a self-propelled weapon. Its principal requirements are, therefore, a charge of explosive and a power plant. As a practical weapon, a torpedo must have a number of other features.

These include the following:

A shell, or housing, strong enough to support the explosive charge, power plant, and related mechanisms, and strong enough to withstand the shock of launching.

A source of energy for the power plant, and for the torpedo control mechanisms.

An exploder that will detonate the explosive charge when the torpedo reaches its target, but which will remain inoperable while the torpedo is close to the firing ship.

Control mechanisms that hold the torpedo on a preset course, at a preset depth.

One or more propellers to drive the torpedo through the water.

Tail vanes and rudders, to control course and depth. Sections B through G of this chapter will show how these requirements are met in a typical torpedo-the Mark 15 type.

12A5. Types of torpedoes in service

All torpedoes are similar in general appearance; they are typically cigar-shaped, as shown in
figure 12A1.
Torpedoes may be classified in several ways:

1. By their power plants (gas-steam or electric). Electric torpedoes are powered, of course, by electric motors; the energy source may be either a dry battery or a lead-acid storage battery. The power plant of a gas-steam torpedo consists of a pair of turbines and a gear-reduction engine. In most of the gas-steam torpedoes, energy is provided by compressed air and alcohol. In the Mark 16 type, the energy source is alcohol and a concentrated solution of hydrogen peroxide.

2. By the craft from which they are launched (destroyer, submarine, or aircraft).

3. By their speed and range.

4. By the type of exploder. The impact exploder operates only when the torpedo actually strikes its target. The influence exploder (which will not be described in this volume) operates when the torpedo passes near its target.

5. By the type of control mechanism. In the older torpedoes, the control mechanism holds the torpedo on a previously calculated collision course with the target. The homing torpedo (which is described briefly in article 12I6) can steer itself toward its target and, if necessary, chase it.

The following list summarizes the characteristics of the nonhoming torpedoes now in the Fleet.

Mark 13 type. The Mark 13 torpedo, compared with the others, is short and thick: its length is 13 1/2 feet, and its diameter, 22 1/2 inches. (The others all have the same diameter-21 inches-so they will fit the standard torpedo tubes.) The Mark 13 is designed for launching from aircraft and PT boats. Its range is 6,000 yards at an average speed of 33 1/2 knots, and it carries 600 pounds of high explosive.

Mark 14 and 23 types. The Mark 14 torpedo is fired from submarines. Its length is about 20 1/2 feet. It offers a choice of two speeds. At the high-speed setting it has a range of 4,500 yards, at an average speed of 46 knots. At the low-speed setting its range is 9,000 yards, and its average speed is 32 knots. It carries 600 pounds of high explosive.

The Mark 23 torpedo is exactly like the Mark 14, except that it has no speed-change mechanism. It operates only at high speed.

Mark 15 type. The Mark 15 torpedo is launched from the deck tubes of surface ships. It is 24 feet long, and carries an explosive charge of about 800 pounds.

It has three speeds:

26 1/2 knots (range 15,000 yards);

33 1/2 knots (range 10,000 yards);

and 45 knots (range 6,000 yards).

Mark 16 type. The Mark 16 is a “chemical” torpedo. It uses a strong solution of hydrogen peroxide, rather than compressed air, to support the combustion of its fuel. This feature gives the Mark 16 a relatively high speed and long range, and enables it to carry a relatively heavy charge of explosive.

Mark 18 type. The Mark 18 is the only nonhoming electric torpedo now in the Fleet. Its principal source of energy is a large lead-acid storage battery. It has a length of about 20 1/2 feet, and an effective range of 4,000 yards at an average speed of 29 knots.

12A6. Construction of the gas-steam torpedo

A gas-steam torpedo is made up of five sections— the head, air-flask section, midship section, afterbody, and tail.
Figure 12A1 is an external view of a Mark 15 type torpedo, showing the four principal sections. The midship section, which is not indicated in the figure, is very short; it is located at the after end of the air-flask section. Because it is permanently joined to the air flask, it is not always counted as a separate section.

When a torpedo is issued to the Fleet it consists of three main units:

1. The head.

2. The air-flask and midship sections (permanently joined)

3. The afterbody and tail (assembled together with joint screws)
Figure 12A2 is a cutaway view of a Mark 15 type torpedo, showing the principal contents of the various sections.

The war head contains the charge of high explosive, and the exploder mechanism that detonates it.

The air-flask section contains the air flask, fuel flask, and water compartment.

In the midship section are a number of valves and fittings for transferring fuel, air, and water between the air-flask section and the afterbody, and for recharging the air flask. Also in the midship section, but attached to the afterbody, is the combustion flask. En this flask, compressed air and fuel are mixed and burned, and provide a high-speed stream of exhaust gases to spin the turbines. Water is sprayed into the combustion flask to increase the volume of gases that go to the turbines, and to prevent overheating.

The contents of the afterbody include the turbines and gear-reduction engine, and their lubrication system; the starting gear; and the mechanisms that control the course and running depth of the torpedo. The depth mechanism includes a diaphragm and pendulum, which determine the torpedo’s depth and the inclination of its axis, and a depth engine to control the depth rudders. The steering mechanism includes a gyro to determine the torpedo’s actual course with respect to the preset course, and a steering engine to control the action of the steering rudders.

The mark of a gas-steam torpedo applies to the air flask, afterbody, and tail. The war head, exercise head, and gyro have individual marks.