The Submarine in War and Peace: Its Development and its Possibilities

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 on 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.

=--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.