Читать книгу The Submarine in War and Peace: Its Development and its Possibilities - Simon Lake - Страница 7

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What is a modern submarine boat? A modern submarine vessel is a complex mechanism capable of being navigated on the surface of the water just as is any boat, but with the added faculty of disappearing at will beneath the surface, and of being operated beneath the surface in any desired direction at any desired depth. Some submarines are able to wheel along the bottom itself, and are also provided with diving compartments from which members of the crew, encased in diving suits, may readily leave and re-enter the vessel during its submergence.

The principal use to which the submarine vessel has thus far been turned has been that of a naval weapon, for scouting and for firing explosive automobile torpedoes, either for defensive or offensive purposes. Its full capacity has by no means been realized up to the present time.

All submarines, regardless of their design, have certain essential features which will be described in the order of their importance.

The Hull.—This must be watertight and capable of withstanding a pressure corresponding to the depth at which the vessel is designed to operate. The hull in most submarines is circular in cross-section; the circular form is best adapted for withstanding pressure. In some cases this circular hull is surrounded by another hull or is fitted with other appendages which will both increase the stability and seaworthiness of the submarine and add to its speed.

Superstructure.—Most of the early military submarines built for the French, Spanish, United States, and English governments were circular in cross-section and of cigar-or spindle-shaped form in their longitudinal profile view. It is difficult, in vessels of this form, to secure sufficient stability to make them seaworthy. They are apt to roll like a barrel when light, due to a diminishing water plane, and when under way the water is forced up over their bows, making a large "bow wave" which absorbs power and causes such vessels to dive at times when least expected. In some instances this tendency to dive has caused loss of the vessel, and, in some cases, of the lives of the crew as well.

They are also very wet for surface navigation, as the seas break over their inclined sides like breakers on a beach. These difficulties led to the invention of the buoyant superstructure, first used on the Argonaut. This is a watertight structure built of light-weight plating—in some cases it has been built of wood—with valves which admit free water to the interior of the superstructure before submerging.

By the admission of the water, danger of collapse is prevented. By this expedient the pressure upon these light plates is equalized when the vessel is submerged. This combination of a circular pressure-resisting inner structure, surmounted by a non-pressure-resisting outer structure of ship-shaped form, is now common to all modern submarines of all navies of the world. This superstructure adds to the seaworthiness and habitability of submarine vessels and increases their speed, both in the light and submerged conditions, as it admits of better stream lines.

Stability.—The stability of a vessel refers to its ability to keep upright and on a level keel. It is desirable to have great stability in a submarine in order that it may not assume excessive angles when submerged. The measure of stability is expressed in inches of metacentric height. The metacentric height of a vessel when submerged is the distance between the centre of buoyancy—or submerged volume—of the vessel and the centre of all the weights of hull, machinery, stores, and equipment contained within the vessel. This distance between the centre of buoyancy and the centre of gravity must be determined very accurately in order to obtain conditions of ideal stability in a submarine.

The metacentric height of a vessel is a term used in naval architecture to express the stability of the ship. In surface ships the term may be used to express either the longitudinal or transverse stability of the vessel, and varies according to the load line and trim or heel of the ship. On the other hand, in submarine boats when submerged the metacentric height is constant and expresses the distance between the centre of gravity and the centre of buoyancy of the vessel, and is the same either in the transverse or longitudinal plane of the vessel. In other words, the centre of buoyancy of the vessel when submerged must be directly over the centre of gravity of the vessel to cause her to submerge on a level keel.

We then get the effect of a pendulum, the length of the pendulum arm being the distance between the two points, and the weight of the pendulum equalling the weight of the ship. Therefore, if a submarine has a submerged displacement of five hundred tons, with a metacentric height of twelve inches, her stability, or ability to remain upright, is equal to a pendulum of five hundred tons hung by an arm twelve inches long, and it would require the same force to incline the ship as it would to incline the pendulum. Therefore it is evident that the greater the metacentric height the more stable the ship, and the less likely she is to make eccentric dives to the bottom or "broach" to the surface.

Ballast Tanks.—All submarines are fitted with tanks which may be filled with water so that the vessel will submerge; these are called ballast tanks. When the vessel is navigating on the surface she has what is called "reserve of buoyancy," the same as any surface vessel. It is this reserve of buoyancy which causes the vessel to rise with the seas in rough weather. It means the volume of the watertight portion of the vessel above the water line. In surface cruising a vessel with great buoyancy will rise to the seas, while if the "reserve" is small the vessel is termed "loggy" and will not rise to the sea. In the latter case the seas will break over the vessel just as they break over a partially submerged rock in a storm. On such a vessel the men cannot go on deck in a storm; in a sea-going submarine a large reserve of buoyancy is therefore essential.

Now in a modern submarine, of five hundred tons submerged displacement, for instance, this reserve should be about one hundred and twenty-five tons, according to the best practice. This means that before the vessel could sink beneath the surface the ballast tanks must be filled with one hundred and twenty-five tons of water. On the surface these tanks are filled with air. The water is permitted to enter by the opening of valves for that purpose. These ballast tanks are located within the main hull and in the superstructure.

Propelling Machinery.—When on the surface the submarine may be propelled by steam, internal-combustion engines, or any other kind of motive power adapted to the propulsion of surface ships. For propulsion when submerged many types of engine have been tried: compressed air engines; steam engines drawing the steam from boilers in which water has been stored at high temperatures; carbonic acid gas engines, and the internal-combustion engines receiving their air supply from compressed-air tanks. Most modern submarines use internal-combustion engines for surface navigation and storage batteries delivering current to electric motors for submerged propulsion. The internal-combustion engine is best suited for surface work because it can be started or stopped instantly, which is a desirable feature in submarine work. It is not fitted for submerged operation because of its great noisiness, and also because its spent gases must be discharged from the boat, in which case these gases ascend to the surface in the form of bubbles and thus betray the presence and position of the submarine. The storage battery, on the contrary, permits the use of practically noiseless machinery and does not require any outboard discharge of gases, as the battery gives off no material quantity of gases when delivering its stored-up power.

I was the first to use successfully an internal-combustion engine in a submarine boat, the Argonaut. This first engine was a heavy-duty engine of rugged construction, and gave but little trouble. This type of engine, with but slight modifications, was installed in six other boats built subsequent to the Argonaut. They also worked satisfactorily for several years, and so long as I had knowledge of them they always gave satisfactory and reliable service.

The first gasolene (petrol) internal-combustion engines installed in the Holland boats were also of rugged construction, and I have been informed by various officers in our submarine service that they were reliable and gave but little trouble. It is known that, after twelve years' service, some of them are still doing good work. The boats in which these engines were installed were slow-speed boats, making only from eight to nine knots on the surface.

A natural desire on the part of the governments of various nations was to secure increased speed. They sent out requirements to submarine boat builders calling for increased speeds within certain limits of cost. The submarine boat builders said: "Certainly we can give you increased speed if the engine builders can give us engines of the necessary power to go into the available space, and within a certain weight, to thus enable us to get the power plant within a certain size vessel possessing the fine lines necessary to give the required speed." The engine builders said they could do it.

The first, as I remember, to break away from the slow-speed, heavy-duty type was a celebrated Italian firm. Then two large and well-known German firms followed; then a celebrated English firm, and certain American firms claimed that they could build reliable, compact, high-speed engines on very much less weight than we had been using. I remember one American firm which offered engines as low in weight as twenty pounds per horsepower. Fortunately, we had sense enough to refuse to accept an engine so light as that, but we, as well as all other submarine boat builders both in this country and abroad, did accept contracts which required engines very much less in weight than the old, slow, heavy-duty type first used, and there has been "wailing and gnashing of teeth" both by the submarine boat builders and by the engine-room forces in the world's submarine navies ever since.

The first light-weight engines built by the Italian firm "smashed up" in short order. The German engines followed suit, and the losses to this firm, or to the shipbuilders, must have been enormous, as a large number of engines were built by them before a set was tested out in actual service. The test of an engine in the shop, on a heavy foundation, open to inspection on all sides, and with expert mechanics in constant touch with the engine, does not mean that this same engine will prove satisfactory in the restricted space available in a submarine boat when run by other than expert engine-building mechanics. I was present at a shop test of one of the German engines referred to, and under shop conditions it appeared to work very well—so well, in fact, that I took an option for my firm to build from the same designs in America. When the engine was tried out, however, in one of the German submarines it rapidly deteriorated and pounded itself into junk in a few weeks. Cylinders and cylinder heads cracked, bed-plates were broken, and crank-shafts twisted or broken. It was evident that the design was too light all the way through.

There are some destructive actions in connection with large, high-speed, light-weight internal-combustion engines which practically all designing engineers have failed to grasp. Otherwise, engineers of all nationalities would not have failed to the extent they have; and I do not believe that there is a submarine engine in service to-day which has fully met the expectations of its designers and builders.

It is unfortunate for the engineering profession that government policy will not permit of a full disclosure of the defects of engines and other equipment in government-owned vessels. Were a frank disclosure made, other inventors and engineers would, in all probability, take up the problems and they might the sooner be solved.

All the earlier submarines were equipped with engines which used gasolene (petrol) as a fuel, but the gas from this fuel, when mixed with a proper proportion of air, is highly explosive. A number of serious explosions occurred in submarines due to this gas escaping from leaky tanks, pipings, or valves. Some of them were accompanied by loss of life. The most disastrous was that on board the Italian submarine Foca, in which it is reported that twenty-three men were killed. Therefore, several years ago, all governments demanded the installation of engines using a non-explosive fuel; and builders then turned to the "Diesel" engine as offering a solution of the problem.

As early as 1905 I had anticipated that such a demand would ultimately be made, so during that year I built, in Berlin, Germany, an experimental double-acting heavy-oil engine; but unfortunately the engineer in charge of the work was taken ill and eventually died. This engine was later completed and showed great flexibility in its control and in reversing. It, however, has never been put on a manufacturing basis.

In the meantime, others took up the work of developing the heavy oil Diesel engine for submarines. The first of the Diesel type engines to be installed in a submarine were built by a well-known French firm of engine builders. As we were then in the market for heavy-oil submarine engines, plans of these engines were submitted to me, but I found it impossible to install them in any boat we then had under construction, owing to their size and weight. I have been advised that engines of this design were installed in some of the French submarine boats. I have also been informed that the shock and vibrations produced by them were such as to cause the rivets in the boats to loosen, and this started the vessels to leaking so badly that it was found necessary to take them out. These engines differed only slightly from the vertical Diesel land engine.

The engine is the most important element in the submarine. Without this it is impossible to make long surface runs, and in the event of its disablement it is impossible to charge the storage batteries to enable the submarine to function submerged, which is, of course, what she is built for doing.

I think the demand for increased speed has come too rapidly. It is more important to have reliability than speed. The criticisms which have been made regarding United States submarines, if traced to their source, may be found to be justified so far as they apply to the engines, but the Navy Department cannot be held responsible, and neither can the designers of submarines. They have both searched the world's markets and secured the best that could be purchased. All naval departments were undoubtedly right when they decided to abandon the gasolene (petrol) engine and substitute therefor the heavy-oil engine. Eventually a successful heavy-oil engine will be produced.

STORAGE BATTERY CELL

A SUBMARINE CELL COMPLETELY ASSEMBLED READY FOR INSTALLATION

Storage batteries as used in modern submarines have been especially developed to meet the special needs of submarine-boat service. The requirements for this service are much more severe than those for any other service to which the storage battery has been applied. The batteries as first introduced in submarines were entirely too frail to stand up to their work, and the gases given off from them while being charged were the cause of much distress and danger to the crew, and have been in some cases responsible for the loss of both vessel and crew.

The Diesel engine, weighing practically five hundred pounds or more per horsepower, has functioned satisfactorily in land installations and has come into very general use, especially in Germany, but when the attempt was made to change this slow-speed engine of five hundred pounds per horsepower into high-speed engines of approximately fifty pounds per horsepower, all designers "fell down." It was but natural that naval authorities throughout the world should call for increased speed; they cannot be criticised for that, as it is a desirable thing, but experience has shown that they called for it too early in the game.

The expense of the development of a new type of motive power, such as the high-speed, heavy-oil-burning engine, for use in vessels whose prime purpose is to preserve the autonomy of the country, should be borne by the government rather than by individuals or private corporations. Millions of dollars have been expended in the development work of engines, but, although vast improvements are now in progress, the successful engine is not yet on the market.

Dr. Diesel has stated that he worked seven years before he succeeded in getting his first engine to make one complete revolution. Governments and the people must therefore content themselves to accept what they can get in a heavy-oil engine, imperfect though it may be, until such time as a satisfactory engine is evolved, built, and tested out under service conditions.

Storage Batteries.—It is impossible in a book of this character to go into much detail regarding the development of the storage battery. There have been two types in general use. They are both lead batteries, one known as the Planté type, in which metallic lead is used to form both the positive and negative plates. The other type employs what is commonly known as pasted plates, in which various compositions of materials are worked up into a paste and forced into metallic grids to form the positive and negative plates. The pasted type has greater capacity per pound of material used, but much shorter life.

In both of these batteries sulphuric acid solutions are used as the excitant between the elements. In charging, hydrogen gas is given off in the form of bubbles, the skin of the bubbles being composed of sulphuric acid solution. These bubbles, when taken in one's lungs, are very irritating, and if they collect in any quantity, or break up and allow the hydrogen gas to mix with the air, there is always danger of creating an explosive mixture within the hull of the vessel or in the battery tanks, which a spark would set off at any time.

The best method of installing batteries on a submarine boat is to have them isolated from the living quarters of the vessel in separate watertight compartments. The elements of the battery should be contained in non-metallic containers and sealed to prevent spilling of the electrolyte under excessive rolling or pitching of the vessel. Means should be provided to discharge the hydrogen gases from the boat as rapidly as formed. Special care should be taken to prevent leakages between the adjacent cells. Circulation of air to keep the cells dry is the best means of preventing this.

Mr. Edison has been working for a number of years on a storage battery suitable for submarine work, and it has recently been stated that he has finally solved the problem of producing a battery that will stand up longer than the lead type of battery, and that it has the further advantage in that it will not give off chlorine gas in case salt water should get into the cells. It should, however, be contained in a separate compartment, which should be ventilated during the charging period, as I understand the Edison battery gives off hydrogen gas the same as the lead batteries. Chlorine gas, as given off from the lead battery when salt water has got into it, has undoubtedly caused the loss of some lives. Mr. Edison claims that his battery, when immersed, will not give off poisonous gases of any kind.

METHOD OF CONTROL IN DIVING TYPE BOATS

Horizontal rudder set down aft inclines the vessel down by the bow, in which condition, with only a small reserve of buoyancy, she will "dive." When she reaches the desired depth a lesser inclination of the diving rudder is supposed to reduce her angle of inclination sufficiently so that the pressure on the top of her hull will offset the tendency to rise due to her positive buoyancy. To be successful there must be no movable ballast, and variable stream line effect requires expert manipulation of the diving rudder.

Depth Control.—Practically all modern submarines use hydroplanes with a horizontal rudder for the control of depth when under way. Hydroplanes might be said to correspond to the side fins of a fish. They are substantially flat vanes that extend from either side of the vessel. They are set on shafts that may be partially rotated by mechanism in control of a man within the vessel. They readily control the depth of the vessel with a certain amount of either positive or negative buoyancy. For instance, submarines are usually submerged with a small amount of positive buoyancy. If a vessel has positive buoyancy she will float. We have seen that in a surface condition the five-hundred-ton submarine has about one hundred and twenty-five tons of positive buoyancy.

METHOD OF CONTROLLING HYDROPLANE BOATS

Showing a proper arrangement of hydroplanes and horizontal rudders. C B represents the centre of buoyancy of the vessel when submerged. G represents centre of gravity, which lies directly beneath centre of buoyancy. Now if hydroplanes are located at equal distances fore and aft their up or down pull is always balanced and does not cause the vessel to dive or broach, but holds her to a level keel. If stream line pull tends to upset this level keel, horizontal rudders may be used to correct it.

Now to prepare the vessel for a submerged run, we admit, say, one hundred and twenty-four tons of water; the positive buoyancy is then reduced to one ton. Now if the forward edges of the hydroplanes are inclined downward (see diagram), and the vessel is given headway, the pressure of the water on top of the inclined hydroplanes, combined with the tendency for a vacuum to form under the planes, will overcome the one ton of positive buoyancy and will pull the vessel bodily under the water. When the desired depth is reached the operator sets the inclination of the hydroplanes so as to just balance the upward pull of the one ton of positive buoyancy, and the vessel proceeds at the desired depth. On modern boats the control of depth is most remarkable; it is very common for submarines to make continuous runs of several hours' duration without varying their depth more than a couple of feet. When the headway or motive force of the submarine is stopped, if she has reserved some positive buoyancy she will come to the surface. If she has negative buoyancy she will sink, but while under way with as much as a ton of positive or negative buoyancy the hydroplanes will absolutely control the depth of the vessel.

HOW HYDROPLANES CONTROL DEPTH OF SUBMERSION

The vessel being "under way" in the course of the arrow, the water contacting against the upper surface of the hydroplanes, as in the upper view, its course is thus diverted and adds weight to the upper surface of the planes. There is also a tendency to form a vacuum under the plane. Both these forces tend to overcome the positive buoyancy of the boat and force her under water and on a level keel if these forces are properly distributed fore and aft of the centre of buoyancy and gravity of the vessel.

Action of the Hydroplanes.—The diagrams are intended to demonstrate how it is that the Lake and other hydroplane boats can be so easily held at a predetermined depth and controlled vertically on an even keel.

The hydroplanes are symmetrically disposed on two sides of the vessel. They should be equal distance forward and aft of amidships. This symmetrical disposition, with equal forces acting on each hydroplane, compels the boat either to rise or sink on an even keel, depending upon which face of the hydroplanes is presented to the passing water during the boat's progress.

In the upper diagram the entering edges of the hydroplanes are inclined downward, and the force of the passing stream lines strikes upon the upper face of the blades. This exerts a downward force which causes the boat to sink, as indicated by the arrows marked "A, A." The opposite of this takes place when the forward ends of the hydroplanes are lifted. This brings the force of the stream lines against the under side of the hydroplanes, and the resultant is a lifting impulse in the direction of the line of least resistance, which is here indicated by the arrows marked "B, B." It is the lifting force so applied that makes it possible to raise hydroplane boats from the bottom even when having considerable negative buoyancy.

ON PICKET DUTY

This is a field of service to which the anchoring weights and the diving compartment of the Lake boats lend themselves conjointly with especial fitness. The illustration represents a submarine doing picket duty on an offshore station. A junction box is placed in a known locality with telephone or telegraph cables leading therefrom to the shore. The submarine, having taken her position on the surface, lowers her anchoring weights, reduces her reserve buoyancy to the desired extent, and then draws herself down to the bottom by winding in again on the cables connecting with the anchoring weights. Having reached the bottom, the diving door is opened and a diver passes out and makes the necessary connections between that junction box and the instruments in the boat.

Holding Depth When Not Under Way.—If it is desired to bring the boat to rest while submerged, but when no motive force is being used, other methods must be used than that just described. One method is to have an anchor or anchors to hold the vessel at the desired depth. If it is desired to lie at rest off the entrance of the enemy's harbor to wait for her ships to come out, the submarine proceeds to her station submerged with a small amount of buoyancy,—which is the usual method of navigating submerged. When she arrives at the desired station the speed is reduced and an additional amount of water is gradually admitted to give her a small amount of negative buoyancy. At the same time her anchoring weights are paid out until they touch bottom. As soon as they do so water is forced out of the ballast tanks by compressed air until positive buoyancy is restored and the vessel stops sinking and remains at rest anchored between the surface and the bottom, like an anchored buoyant mine. By winding in on the anchor cables a submarine may then be hauled down nearer the bottom, and by paying out the cables she may rise nearer the surface. On picket duty off harbor entrances she remains sufficiently near the surface to project her telescoping periscope occasionally above the crest of the waves to keep watch and see that an enemy ship does not enter or clear. In this condition there is no necessity to have any machinery running on board the submarine, therefore she can remain for weeks at a time on station without exhausting her fuel supply. It is only necessary for her to renew the air supply now and then, which can be done at night. Another method for holding a vessel at rest is by taking in and forcing out alternately small quantities of water so as to keep her in equilibrium between positive and negative buoyancy. Another method is to use vertical propellers operating in wells extended from the sides, and by running these it is possible to exert an upward or downward pressure and so hold her at a depth. Neither of these methods is as satisfactory, however, as the anchor weights, because the vessel will not hold a definite position on station, but will drift off with the current. They also make a drain on the storage battery and require constant attention on the part of the members of the crew. By the anchor weights scheme the vessel may stay on station as long as the food and fuel supply holds out.

SHOWING VARIOUS CONDITIONS IN WHICH A SUBMARINE OF THE LEVEL KEEL TYPE FITTED WITH BOTTOM WHEELS, MAY NAVIGATE

1, running light on surface; 2, awash, ready for submergence; 3, submerged, depth controlled by hydroplanes; 4, running on bottom.

The above facts set forth simply the outstanding mechanical principles upon which the operation of the submarine is based. The submarine of to-day, however, has many auxiliaries, to describe which in detail would require several volumes of technical description.

I will briefly enumerate a few of the more important of these devices and describe their function as applied to the war submarine.

THE LOWER PORTION OF GALILEO PERISCOPE

THE PERISCOPE IS THE EYE OF THE SUBMARINE.

(See description.)

The Periscope.—The periscope is the eye of the submarine. In its simpler form it consists of a stiff metallic tube, from fifteen to twenty feet in length and about four inches in diameter. Referring to Figure 1, on page 23, it is made up of an object glass, A, which "views" or takes an impression of all objects within its range or field of vision, and transmits an image of such object through the right-angle prism, B, which turns the image so that it appears some distance down the tube, say, for purposes of description, at C. If a piece of ground glass were held at the focus of the objective lens at C, the image could be seen. The lens D, located farther down the tube, in turn now "views" the image and transmits it still farther down the tube, where it is turned through the right-angle prism, E, and where the image is again turned into an erect position. A piece of ground glass located at F would show the image in the same manner as an image is shown on the ground glass of a camera. The magnifying eyepiece G magnifies the image so that distant objects appear of natural size.

Other figures show a periscope as made by the Officina Galileo in Florence, Italy. This firm makes periscopes with binocular eyepieces. The success of any periscope depends upon the character of the material used in the lenses and prisms and the accuracy of the workmanship. This firm, which is probably the oldest optical manufacturing house in the world, said to have been founded by Galileo himself, turns out instruments of the most beautiful workmanship. The flange of the instrument is bolted to the top of the conning tower, or deck, and a gate valve is arranged between the deck and the eyepiece so that in case the tube should be carried away the gate valve can be closed and thus prevent water from entering the vessel. A hand wheel arranged below the binocular eyepiece permits of easy rotation of the instrument. Provision is made for introducing dry air; this prevents condensation forming on the lenses or prisms within the tube.

Owing to the fact that there is a certain loss of light in transmitting the image through the various prisms and lenses, it is customary to magnify the image so that it appears to be about one-quarter larger than when viewed by the natural eye. This has been found by experience to give, when viewed through the periscope alone from a submerged vessel, the impression of correct distance.

Previous to 1900 there was no instrument which would give through a long tube normal vision and a correct idea as to distance. At this time I took up with various opticians the question of producing such an instrument. They all contended that it was impossible to produce an instrument that would give through a long tube a field of vision equal to the natural eye or that would convey a correct idea as to the distance of an object when viewed through a long tube. The camera lucida which Mr. Holland and others had used in the earlier submarines simply threw a picture of the object on a bit of white paper, usually located on a table. This did not give to the observer any more idea of the correct distance of an object than a photograph would. Believing, however, that a solution could be found, I then purchased a variety of lenses and started making experiments.

Without any special knowledge of optical science, one day quite by accident I secured the desired result and found that it was possible to secure practically normal vision through a tube of considerable length. About the same time, Sir Howard Grubb, of England, brought out an instrument in which he accomplished the same result. I then continued in my experimental work and brought out an instrument which was designed to give a simultaneous view of the entire horizon.

This instrument was called an "omniscope." It was first called a "skalomniscope," which was a word coined with the idea of describing the function of the instrument and which, translated, means "to view and measure everything." A scale was used in connection with this instrument which would convert it into a range finder by measuring the image of an abject of known dimensions, such as the length of a ship or the height of its smokestack, and give simultaneous reading as to its distance.

For a time it was necessary for us to manufacture our own sighting instruments, but later, when the optical houses understood the principle of the periscope, they took up the matter of manufacture and have so greatly improved them that it is now possible to secure instruments of great accuracy and fine definition.

The periscope, however, is faulty, in that it is only an instrument for day use. As soon as dusk comes on the periscope becomes useless. The passing of the image down the tube and through the various lenses and prisms reduces the brilliancy of the image to such an extent that, even though it is finally magnified to above normal, the image is so thin at night that it cannot be seen. This forces the submarine to become vulnerable in making an attack at night, as it is necessary for the conning tower to be brought a sufficient distance above the surface of the water to permit the commanding officer to secure natural vision.

With the powerful searchlights and rapid-fire guns, the submarine would have little opportunity to approach a surface war vessel at night without great danger of being discovered and destroyed.

THE VOICE AND EAR OF THE SUBMARINE

A Fessenden oscillator, before being installed. The flange of the oscillator is riveted to the shell of the ship and its diaphragm is caused to vibrate by the sound waves, which pass through water more distinctly than they do through the air. To send out signals it is caused to vibrate mechanically by electrical apparatus.

Invisible Conning Tower.—For night observation it has been proposed to use transparent conning towers built of clear glass, in which the commander takes his station and just sticks his head above the crest of the waves in order to direct his vessel against the enemy. This has not as yet come into general use because of the difficulty of securing sufficiently clear glass in the desired form. Experiments have been made, however, which show that quite a large transparent conning tower cannot be seen on a submarine at rest even when within a couple of hundred yards; the application of these conning towers will greatly increase the submarine's efficiency for night work.

Submarine Sound Receivers.—All modern submarines are fitted with devices which enable the commanders of submarines to communicate with each other when running under water even when considerable distances apart. One of these outfits consists of a signal bell and a powerful receiver with which sounds may be transmitted and heard. Conversations may be carried on by the Morse and other codes for distances of ten or twelve miles.

TORPEDO TUBES ASSEMBLED READY FOR INSTALLATION IN A SUBMARINE BOAT

Left view, the breech end of the tube. Right view, the outboard doors, which must first be opened before the torpedo is expelled from the tube by compressed air. When the torpedo is expelled it starts a compressed-air engine supplied with air stored at high pressure within the torpedo, and will run several thousand yards under its own power.

A later device, called the Fessenden oscillator, will transmit or receive sounds a distance of twenty miles. The principle of its operation is that of setting up wave vibrations by very large transmitters; these vibrations are carried by the water and taken up by receivers on other submarines. It has been found that the human voice will set up vibrations in the Fessenden transmitter so clearly that wireless conversation may be carried on under water for several hundred yards. I discovered in my earlier experiments that when a submarine was lying submerged, with all machinery shut down, the noise of the machinery in an approaching ship could be detected quite a distance off without the use of any special kind of receivers. In this way the commander of a submarine can always note the approach of an enemy simply by shutting down his own machinery. The warning thus given him comes long before he could sight the enemy ship were he on the surface. After a little experience one can tell the type of ship approaching from the sound, as every type of ship has sounds peculiar to her class. The smash of paddle wheels, the deep, slow pound of the heavy merchant ships or battleships, the clack and the whir of the higher speed machinery on destroyers or torpedo boats, are all easily recognizable when one becomes familiar with them. At the present time all the larger submarines are fitted with wireless outfits on their decks which they may use when on the surface to communicate with other submarines or with their base.

Torpedo Tubes.—These are used to start the automobile torpedo on its course toward the enemy. In simple form they are tubes about eighteen inches in diameter and seventeen feet long, placed in line with the axis of the vessel. They are fitted with doors both internal and external to the submarine. The inboard door of the tube opens into the interior of the vessel and permits the loading of the torpedo. When the torpedo is to be discharged the inboard door is closed and securely fastened. The outer door is then opened, and through the operation of quick-opening valves compressed air is admitted back of the torpedo and the torpedo is driven out of the tube in the same manner that the bullet is driven out of an air rifle or the cork out of a pop-gun. Some of the larger modern submarines carry several torpedo tubes firing in line with the axis of the vessel both forward and aft. Some carry torpedo tubes on their decks which may be made to train to fire broadside on either side of the vessel.

A WHITEHEAD TORPEDO

Courtesy of the Scientific American

The forward end of the torpedo is the war head filled with guncotton or trinitrotoluol. A detonator is screwed into the end of the war head to set off the main charge on contact. An air flask forms the middle portion of the torpedo. Aft of this is the depth-control mechanism, in which a diaphragm controls the diving rudder by the pressure of the water against a spring set for the desired depth. A pendulum controls the levelling mechanism and a gyroscope its direction in the horizontal plane, tending to keep it on the course by its control of the vertical rudder.

REAR END OF THE WHITEHEAD TORPEDO

Courtesy of the Scientific American

Showing compressed air engine and twin propeller with their control gear.

Automobile Torpedoes.—These are the projectiles which are used to destroy the enemy's ship. They are called automobile torpedoes because they will, on being ejected from the torpedo tubes, continue running in the direction in which they are aimed, from power and mechanism contained within themselves. They are wonderful pieces of mechanism and cost several thousand dollars each. They are virtually miniature submarine boats. The essential features of the automobile torpedo are the airflask, the warhead, the depth control, and steering and propelling machinery. The airflask forms the central section, which is a steel tank containing compressed air stored at high pressure; about twenty-five hundred pounds per square inch is the present practice. When the torpedo is expelled from the torpedo tube this air is automatically turned on to run the engines. It passes through reducing valves and heaters to drive either a multiple cylinder or a turbine engine, and revolves two propellers, running one clockwise and the other counterclockwise, set in tandem at the stern of the torpedo. The propellers, running in opposite directions, thus enable the torpedo to be more easily steered by the delicate automatic steering machinery. A diaphragm operated by the pressure of the water operates control mechanism which regulates the depth. An instrument called the "Obry gear" steers it in the horizontal plane. The essential feature of the "Obry gear" is a gyroscope which is started when the torpedo is ejected from the tube. It is instantly speeded up either by a powerful spring or an air turbine to about fifteen thousand revolutions per minute. The peculiarity of the gyroscope is that it has a tendency to hold the direction in which it is started. Hence, if the torpedo starts swerving either to the right or left from the direction in which it is aimed, the gyroscope causes certain valves to function which will automatically set the steering rudder to bring the torpedo back into its original course. The "Gyro" will continue this control until the torpedo has completed its course, which in some of the latest types is said to be about five miles.

The warhead is the forward portion of the torpedo and contains usually wet gun-cotton, which is a safe high explosive and can be exploded only by a detonating charge of the more sensitive explosives. This detonating charge is placed in a tube screwed into the forward end of the torpedo. Extending out from the forward end of the tube is a small propeller, the purpose of which is to set the firing mechanism after the torpedo has run a certain distance from the vessel from which it has been fired. This is a safety device to prevent the torpedo from being exploded near its own ship. The torpedo running through the water causes the propeller to revolve, which turns a shaft. After the shaft makes a certain number of revolutions it sets a firing pin, and then if it hits an object it will explode. Many modern torpedoes are loaded with trinitrotoluol. This is a much more powerful explosive. According to experts, the explosion of two hundred and fifty pounds of T-N-T, as it is called, will destroy any battleship ever built.

RAPID-FIRING GUNS

Courtesy of the Scientific American

Rapid-fire disappearing guns may be quickly elevated above armored turret when the submarine rises to the surface.

Divers' Compartment.—Some submarines are fitted with a divers' compartment, from which compartment mines may be planted, either when on the surface or when submerged. This compartment is fitted with a door which opens outwardly in the bottom of the boat. It is shut off from the living and machinery rooms of the vessel by an air lock and heavy pressure-resisting doors. The divers' door may be opened when the vessel is submerged and navigating on the bottom, and no water will come into the vessel when the door is opened. This is accomplished in the following manner: The members of the crew who wish to go outside the vessel first go into the diving compartment. They close the door which shuts them off from other parts of the vessel. They then turn compressed air gradually into the compartment until the air pressure in the compartment equals the water pressure outside. If the depth is one hundred feet the air pressure in the compartment would need to be 43.4 pounds per square inch; if the depth is two hundred feet, twice that, or 86.8 pounds per square inch, etc. When the air pressure in the compartment equals the water pressure outside, at any depth, the door in the bottom may be opened and the water will not rise up into the compartment, because the air pressure keeps it out. Tests have been made which show that it is safe for divers to go out from compartments of this kind in depths up to two hundred and seventy-five feet.

DIVING COMPARTMENT

This view shows the diving compartment being used for the purpose of grappling for the electric cables controlling fields of submarine mines. Operating in this manner, the diving compartment becomes a veritable travelling diving-bell, and when the air pressure in the diving chamber is made to balance with the water pressure outside the diving door may be opened and yet the water will not enter the working chamber.

Dangers.—Years of painstaking development work have eliminated most of the dangers connected with the operation of submarines in times of peace. The experienced designers have learned the importance of having great submerged stability, so that no modern craft is likely to make an unexpected headfirst dive into the mud, hard sand, or rocks on the bottom. This was a common occurrence not many years ago. Another danger to be avoided is that of asphyxiation by the escape of noxious gases from the engines. The blowing up of the vessel by the ignition of hydrogen fumes from the battery is another risk to be guarded against. In the latest vessels the noxious gases from the engine are not permitted to escape into the engine-room; gasolene is rapidly giving place to heavy-oil engines which do not use an explosive fuel, and the hydrogen gas given off during the charging of batteries is pumped overboard as rapidly as it is generated. Consequently modern submarines, when navigating on the surface, are as safe as any surface ship. In fact, they are safer, from the fact that they are so much more strongly built and that they are divided into compartments. Any one of these compartments could be filled by water in an accident and the remaining compartments would keep the ship afloat. In submerged peace-time navigation the dangers are those of collisions with surface vessels, uncharted rocks, or sunken ships. The danger of collisions with surface ships may be avoided by keeping below the depth of keel of the deepest draft surface ship, when long under-water runs are being made, and always stopping machinery to listen for the sound of surface ships before rising to the surface. If running near the surface where periscopic vision is possible, constant vigilance must be maintained, as there are no rules of the road or right of way which may be claimed by the submarine commander, owing to the fact that the lookout on the surface craft, in all probability, cannot see his little periscope in time to avoid collision.

A MODERN SUBMARINE CRUISER, OR FLEET SUBMARINE (LAKE TYPE)

The parts indicated by numbers in this illustration are as follows: 1, main ballast tanks; 2, fuel tanks; 3, keel; 4, safety drop keel; 5, habitable superstructure; 6, escape and safety chambers; 7, disappearing anti-aircraft guns; 8, rapid-fire gun; 9, torpedo tubes; 10 torpedoes; 11, twin deck torpedo tubes; 12, torpedo firing tank; 13, anchor; 14, periscopes; 15, wireless; 16, crew's quarters; 17, officers' quarters; 18, warhead stowage; 19, torpedo hatch; 20, diving chamber; 21, electric storage battery; 22, galley; 23, steering gear; 24, binnacle; 25, searchlight; 26, conning tower; 27, diving station; 28, control tank; 29, compressed-air flasks; 30, forward engine room and engines; 31, after engine room and engines; 32, central control compartment; 33, torpedo room; 34, electric motor room; 35, switchboard; 36, ballast pump; 37, auxiliary machinery room; 38, hydroplane; 39, vertical rudders; 40, signal masts.

How the Submarine Works.—Reference to the diagrammatic view of a modern submarine will probably make clear the following explanation of the operation of a submarine. We will assume that our submarine leaves her own harbor with fuel, stores, and torpedoes on board, wireless and signal masts erected. She is bound to a station farther down the coast, but receives word by wireless that an enemy fleet has been seen approaching the coast in such a direction as to indicate an attack on New York. She receives instructions to return and take up a station fifteen miles off Sandy Hook, the entrance to New York Harbor, and also that she is to coöperate with the smaller harbor-defense submarines that are permanently located in New York. She therefore puts back to the station designated. All deck fittings and lines are stowed except the ventilators and the deck wireless outfit; the latter is left standing so as to keep in touch with the scout ships and destroyers which are reporting the approach of the enemy. Shortly after arriving at her station, the commander notes smoke on the horizon and orders are given to "prepare to submerge." Each member of the crew then proceeds to his particular task; the wireless masts and ventilators are quickly housed, and all hatches are closed and secured. The quartermaster and submerged-control man who controls the steering and hydroplane operating gear take their stations in the control department. The engines are uncoupled by means of the rapid operating clutch, the electric motor is coupled, the hydroplanes are unfolded, the valves are opened, and the word is passed to the commander, "All ready for submergence!" All this is done in a modern vessel in less than two minutes.

The command is then given: "Fill main ballast!" Quick-opening valves are opened and the water rushes into the ballast tanks and superstructure at the rate of fifty or sixty tons per minute. The order is then given: "Trim for submergence!" Sufficient water is then admitted into the final adjustment and trim tank to give the desired buoyancy and trim, and the vessel is now ready to submerge on signal from the commander, who now takes his station at the periscope. The gunners have also taken their stations at the torpedo tubes to prepare to load the tubes as soon as the torpedoes already in the tubes are discharged. The whole time consumed from the time word to "prepare to submerge" until the vessel is running under water has probably not been over two or three minutes. In the meantime the enemy has been rapidly approaching and her superstructure is already above the horizon. The commander of the submarine notes that if the enemy holds its course it will be advantageous to change his position to intercept the oncoming fleet. He therefore gives word to submerge to the desired depth and gives the quartermaster the course, and the vessel proceeds, entirely submerged, to get nearer the enemy's line of approach. The commander then brings his submarine to rest before extending his periscope above the surface. As soon as the enemy is found to be coming within range he manœuvres his ship so that his torpedoes will bear the proper distance in advance of the ship he selects to destroy. To make a hit it is necessary to fire in advance of the oncoming ship to allow for the time the torpedo takes to reach the point where the enemy will be. Range finders, torpedo directors, and rapid calculators enable the commander to calculate this to a nicety. If the distance is only a thousand or fifteen hundred yards, a hit is pretty certain to be made, but the greater the distance the less the chance of success and the greater the opportunity for error.