By Commander William Hovgaard
Professor of Naval Design and Construction, Massachusetts Institute of Technology, Boston, Mass. Read to the Royal Canadian Institute, January 23rd, 1915
Part I – Historical review.
THE conception of submarine navigation is an old one, and submarine boats have been built and operated fairly successfully several times during the last hundred and forty years. As early as 1624 we hear of a Hollander, Dr. C. J. Drebbel, who constructed a wooden submarine boat propelled by oars. With this boat he experimented on the Thames. Submarine boats, however, did not acquire practical military importance till in this century, because not till then did the technical resources at the disposal of the inventors permit a practical solution.
During the years 1771 to 1775 an American, David Bushnell of Connecticut, constructed a submarine vessel which he called the American Turtle. It was built of wood and the shape was that of two tortoise shells stuck together. The boat possessed in a primitive form most of the essential features of modern types. A mine box of wood containing 150 lbs. of gunpowder was carried on the outside and was to be attached with a screw to the bottom of the enemy ship. During the War of Independence an attack was attempted against a British frigate, the Eagle, but the operator did not succeed in fixing the mine, which exploded harmlessly at a distance from the ship. Bushnell was the first inventor of the submarine mine. He showed, what was then considered marvelous, that gunpowder could be made to explode under water. He well deserves the title accorded to him as the "Father of Submarine Warfare".
Robert Fulton took up the ideas of Bushnell and with more means at his disposal he advanced the solution of the problem considerably. It is of interest to note that Fulton was a peace advocate, and when he devoted so much energy to the development of the submarine boat as also of the submarine mine, it was on the ground that he believed these weapons would make war on the sea impossible. Other friends of peace have had the same belief. We know now how much they have been mistaken. Fulton went to Paris in 1797 and laid his plans for a submarine boat before the Directory, but it was not till three years later, when he offered his design to Bonaparte, who was then First Consul, that his plans were seriously considered. Bonaparte saw the possibilities of the new weapon and appointed a Committee consisting of Volney, Monge, and Laplace, who gave a favorable report. A sum of 10,000 francs was appropriated for the purpose and an experimental boat was constructed. The shell plating of this boat was of brass with iron frames. The boat was propelled by hand-driven screws. Fulton descended to a depth of 25 ft. and remained under water for more than four hours. He carried a store of compressed air in a tank for renewal of the air. He blew up a small vessel in the harbor of Brest, attaching a mine to her bottom. In spite of the relative success of the experiments, Napoleon realised that the speed, which was only two knots, was too small for military purposes, and nothing further was done.
During the Civil War in America a number of so-called "Davids" were built by the Confederates. Although referred to as submarine boats, they were probably most of them surface boats, going awash with very little freeboard, showing practically only a cupola above the surface. Some of them were designed for diving, but it is not known that any of them operated successfully under water. Most of the Davids were constructed of iron plates and some were propelled by steam-power. They were built in haste with limited resources and necessarily primitive in construction. They are of interest chiefly because they were actually employed in war and because one of them, a hand-driven boat, succeeded in blowing up a Northern ship, the Housatonic.
At the same time the French Government built a submarine boat, the Plongeur, which was launched at Rochefort in 1863. The Plongeur was of about 450 tons displacement, much larger than any boat built heretofore and thereafter up till a few years ago. The general shape was not unlike that of an ordinary torpedo boat, and it carried a superstructure on top in which was housed a detachable boat to be used in case of emergency. The hull was built of iron plating stiffened by frames. Ballast tanks were fitted for changing the displacement, and the depth was to be kept by two regulating cylinders which produced variations in the force of buoyancy. There were also vertical and horizontal rudders. The boat was propelled by an engine driven by compressed air, whence a very large store of compressed air at a pressure Of 12 atmospheres was carried. The engine was of 80 horse-power and operated a propeller which gave the boat a speed of about 5 kts. on the surface. Le Plongeur went down to depths of from 30 to 40 ft., she could slide along an even bottom without difficulty, but steering in the vertical plane caused great difficulties. She was the best designed boat up to that time, but the speed was too slow, the radius of action small, and steering in the vertical plane remained an unsolved problem. The boat, therefore, had no military value and in 1874, after ten years of experiments, the French Government abandoned the project.
The period from 1880 to 1905.
The greatest difficulty before the designers of submarine boats prior to 1880 was to find a source of power suitable for underwater propulsion. Compressed air, tried in the Plongeur, was probably the best available means of storing energy for that purpose, but the air reservoirs occupied too much space, whence the supply of energy that could be carried was too limited. It was, therefore, of the greatest importance for the solution of this problem when in 1880 the French scientist Faure succeeded in improving the lead accumulator, invented by Planté in 1859, by applying a layer of red lead paste as an active material to the lead plates. The accumulator so perfected afforded a means of storing energy eminently adapted for submarine boats since it was independent of the atmospheric air and, although heavy, took up relatively little space.
Another difficulty was that no weapon existed, suitable for a submarine boat. Neither the attachment of mines to the bottom of an enemy's ship, or the use of spar or towing torpedoes offered satisfactory solutions, and ramming was at least as dangerous to the submarine boat as to the enemy's ship. Another great step in advance was, therefore, made when the Whitehead torpedo appeared about the end of the "seventies". This weapon enabled the submarine boat to attack a ship from a distance without difficult and dangerous manoeuvres.
At the same time there was in the "eighties" a strong development in all machinery and fittings used in the application of electric power and light, and great progress was made in the production and storage of compressed air.
Thanks to all these inventions and to the general rapid advance in all fields of engineering which was characteristic of that period, the problem of the submarine boat suddenly became capable of a practical solution. In various parts of the world designs were prepared and experimental boats were constructed, which before the end of the century led to the production of boats practically applicable in naval warfare.
In the "eighties" the author of this article commenced to study the problem and worked out several designs of which that of a "diving boat" published in 1880 will be here briefly described in order to illustrate the general standpoint of the problem at that time. It was realised that ordinarily a submarine boat would travel on the surface, and that diving would only be necessary occasionally, namely when in the presence of an enemy. Hence the boat was designed essentially for work on the surface and was given a form very similar to that of a Thornycroft torpedo-boat. A large self-bailing superstructure was fitted on the top, by which a good freeboard and longitudinal stability and hence good seagoing capability were secured. The total reserve buoyancy was about 33 per cent. of the displacement in light condition, half of which was obtained by emptying internal ballast tanks, the other half was due to the self-bailing superstructure which was provided with valves that could be closed watertight. The propulsion was to take place on the surface by steam-power and in the submerged condition by electric accumulators. A combination of electric power for submarine propulsion with another distinctly different source of power for the surface secured at once the military qualities of high speed and great radius of action necessary for bringing the boat to the field of operation of the enemy, and invisibility and perfect protection by going submerged when in the presence of the enemy. The design provided for an armament of two Whitehead torpedo tubes in the bow, giving great power of attack.
The type thus proposed, where principal importance was attached to service in the surface condition, was later perfected, and boats designed on this principle are now generally referred to as "submersibles" in contradistinction to "submarines", which are designed more particularly for submerged work. The characteristics of the two types will be more fully discussed later.
During the "eighties" a Swede, Mr. T. Nordenfelt, built several boats and attained a fair measure of success. He used steam-power for propulsion both on the surface and under water, the steam when in the latter condition being derived from a store of hot water in a reservoir. The system was simple but in order to obtain an appreciable radius of action under water a large store of hot water under a high pressure had to be carried, whence much space and weight were required. Another and serious drawback was that the heat would leak away and the pressure fall in the hot water reservoir in a relatively short time. The Nordenfelt boats were maneuvered on an even keel, and horizontal propellers were used to secure immersion and to maintain the desired depth. The last Nordenfelt boat, built for the Russian Government, was 160 / 230 ts. and the speed was 14 / 5 kts. The form was very nearly ship-shaped, and the superstructure was very long. The control of the motion in the vertical plane was never satisfactorily attained in the Nordenfelt boats.
In France M. Claude Goubet experimented during the "eighties" and "nineties" with a small type of boat driven only by electricity derived from a battery of primary cells. He was entirely successful and his experience proved of great value to later designers, but the boats were too small and slow to be of military value. The French Government, therefore, rejected his boats, and in 1886 set to work to build submarine boats itself.
The first boat built by the French Government since its attempt with the Plongeur was the Gymnote, laid down in 1886, a small 30 ts. electrically-driven experimental submarine. As in the Goubet boats the power was at first derived from primary cells, but later a storage battery of iron-copper elements and finally of lead accumulators were substituted. Lead accumulators were here, it appears, used for the first time in submarine boats.
In 1889 a much larger boat, the Gustave Zédé 266 / 274 ts., was laid down. She was likewise driven by electricity only and was designed for high speed. The ratio of length to diameter was about 15. Great difficulties were experienced with the storage battery. On one occasion the battery was so badly damaged by short-circuiting that it had to be dismantled, whereupon larger cells of an improved type were substituted. Vertical steering proved very difficult, the boat often took excessive inclinations and hit the bottom on some occasions. Additional horizontal rudders were fitted, so that at last there were rudders both forward and aft and also amidships.
The construction of the next boat the Morse was suspended for a long time pending the alterations in the Gustave Zédé and was not completed till 1898. The Morse was more ship-shaped and carried an optical tube, probably of primitive construction. This was a most important addition to the outfit of the submarine boat, because if further developed it promised to solve, partly at least, one of the greatest difficulties connected with submarine navigation, viz., the complete blindness of the boat when travelling under water. It enabled a boat to approach an enemy within striking distance of the torpedo without the necessity of coming to the surface, showing at intervals, only the head of the periscope a few feet above the water.
In 1899 was launched the Narval, 117 / 202 ts., designed by M. Laubeuf, a French naval constructor. This boat represents in an eminent degree the type referred to before as a "submersible", which term was first introduced by M. Laubeuf to distinguish between his ship-shaped boat and the previous spindle-shaped boats built by the French Government which he called "sous-marins". The hull is double, consisting of an inner spindle-shaped "strength hull" of heavy construction, calculated to resist the maximum pressures of the water, and a light outer shipshaped hull which completely envelops the inner. The shape of the aft-body resembles that of a Thornycroft torpedo boat. The space between the two hulls is used chiefly for water ballast, whence a very great reserve buoyancy may be obtained. It was found difficult at first to fill the tanks in a complete manner; whence shifting of airbubbles were apt to cause violent changes in the longitudinal balance of the boat, and the vertical steering was disturbed. Also the filling of the tanks took nearly one-half hour, much too long for immersing the boat whew in the presence of an enemy. These defects were afterwards remedied in the Narval and were avoided in later boats of this type. The Narval was driven by steam in the surface, where she made 12 kts. The boilers used oil-fuel. Under water she was driven by electric power and attained a speed of 8 kts. She carried four 18-in. torpedo tubes. The heat from the machinery caused considerable trouble. On the whole, however, the Narval proved satisfactory and was the type ship for a great number of following boats. Other types of submersibles which have later been developed, such as the Germania and the Laurenti types, are derived from the Laubeuf boats.
In the United States Mr. John P. Holland worked with great perseverance for a number of years and built several experimental boats. The first, which was very primitive, being worked by hand-power, was launched in 1878. Finally, through the agency of the Holland Torpedo Boat Company, he succeeded in producing a boat that was accepted by the United States Navy in 1899. The boat, which was named the Holland, was 67 / 74 tons; it was cigar-shaped with but a small superstructure on the top and, consequently, had very little stability in the surface condition. The reason of the success of this boat was the use of a gasoline engine for surface work, combined with a storage battery for the submerged condition. Holland first tried steam-power but failed, and the gasoline motor which had just then been developed to a practicable shape was here used for the first time in submarine boats. The gasoline engine had several great advantages; it occupied relatively small space and did not produce so much heat as a boiler and steam engine; it consumed very little fuel so that a great radius of action could be obtained. The engine of the Holland was of 50 H.P. and gave the boat a speed of 8 kts. on the surface. The electric motor was of about the same power and drove the boat with a speed of 6 kts. under water. A novelty in this boat was the way in which diving was effected. Contrary to earlier experimenters who held that the axis of the boat should as far as possible be kept horizontal, Holland boldly effected immersion and emersion by "porpoising", i.e., by inclining the axis, sometimes to great angles, using the horizontal rudder fitted in the stern. This method of controlling the vertical motion proved satisfactory although not without danger, for it has happened that boats of the Holland type took deep involuntary dives. Holland's experiments showed the great importance of keeping the centre of gravity immovable and of compensating for all changes in buoyancy.
The Holland type was reproduced in the United States Navy in the Adder Class and following types and in England Vickers commenced building the A-class for the British Navy.
During the "nineties" another American Mr. Simon Lake constructed several experimental boats, and evolved a type of which the Protector, 136 / 174 ts., built in 1901-2 was the first representative.
The Protector belongs to the submersible type, having a ship-shaped superstructure and a reserve buoyancy in the light condition of about 28 per cent. of the light displacement. Diving and emersion takes place as in the Gustave Zédé by four horizontal rudders, the boat being always kept nearly on even keel. Mr. Lake's first idea was to produce a boat suitable for salvage operations and the like, and he for this purpose fitted wheels forward and aft hung by pivoted steel jaws fitted in pockets in the bottom and cushioned by hydraulic cylinders. These wheels enabled the boat to run along on an even bottom with a slight deficiency in buoyancy. The means of propulsion are the same as in the Holland.
The early development of submarine boats was groping and erratic, the "eighties" and "nineties" was a period of experimentation, resulting in a great variety of types, but after about the year 1900 boats entered into actual military service, with the result that an elimination of the less practicable features took place, and there o owe a movement towards a unification of type. At the same time the nautical and military requirements led to a steady increase in displacement and power. Great progress was made in perfecting the various technical appliances. We shall now briefly describe recent types of boats so far as their various features have been made public.
In the British Navy the Holland type was gradually modified considerably. The ratio of length to diameter, which in the A-class was about 5 1/2 was much increased. Later boats were given large side structures patched on outside the spindle-shaped strength hull, the object being probably to gain greater tank volume, greater stiffness in the surface condition, and greater safety against collision. The displacement in the E-class is 710 / 825 ts. and in the six boats of the F-class laid down in 1913 it reaches 960 / 1200 ts. and the speed is 13 / 12 kts. No data are known about later boats, but they are probably larger and more powerful.
In the United States the Electric Boat Company developed the Holland type. Boats of the M-class have a submerged displacement of 800 ts. A larger boat of about 1200 ts. displacement is to be laid down this year. The price of this boat is 1 1/3 million dollars. The speed according to press reports is to be 20/11 kts. The reserve buoyancy of the American Holland boats has been gradually increased and the form of the superstructure is now ship-shaped in the bow.
The Holland type has been adopted also by the Whitehead firm in Fiume. The bow of the Whitehead boats is similar to that of an ordinary torpedo boat.
The Lake boats have likewise developed to larger size. The Seal carries torpedo-tubes in the superstructure.
In France a greater differentiation took place than in other navies. The two main types, the submarine and the submersible, co-existed and were developed simultaneously to greater sizes, but gradually approached each other. After the comparative trials in 1908 between submarines of the Emeraude class and submersibles of the Pluviose class it appears that the submarine was altogether abandoned. In five boats laid down last year the displacement is 830 /1070 ts.
In Italy submersibles of the Laurenti type have been developed. They have the same principal features as the Laubeuf boats of which they may be considered a variety, but differ from them in some respects. The strength hull is not always circular, although in later boats this seems to be the case. Some have horizontal propellers for submerging. Some recent boats have three propellers for propulsion.
In Germany the Germania firm in Kiel constructs submersibles of the d'Equevilley-Germania type, likewise derived from the Laubeuf boat. The strength hull is cylindrical and is built up of several welded sections without frames. The sections are scarfed together, except one of the sections amidships which is connected to the others by bolted flanges so as to facilitate shipping and unshipping of the machinery. The ballast and fuel tanks are outside the strength hull amidships and at the ends. Only one internal tank, used for compensating for incidental variations in buoyancy, is fitted amidships. The boats dive almost on an even keel. The latest German boats are probably of about the same size as the English F-class.
 Submarine Boats, London, 1887.
 Proposed Designs for Surface Boats and Diving Boats, Institution of Naval Architects. London, 1888.
 The upper figures in the fractions refer to the surface condition, the lower figures to the submerged condition.