RECENT SUBMARINES AND SUBMERSIBLES
After the Civil War several nations interested themselves in the subject of submarines, and during the Franco-Prussian war in 1870–71, France attempted the construction of such vessels, but without success. Yet the possibility of producing these boats was becoming more apparent every year by the improvements in electrical motors, gasoline engines, compressed-air motors, and the automobile- or fish-torpedo—itself a miniature submarine boat.
In America the progress made in submarine-boat construction has been fully as great, if not greater, than in any other country. Undoubtedly the foremost figure in this progress has been Mr. P. Holland; and his efforts and successes are largely responsible for the present fleet of submarine boats built already, or in the process of construction, as well as for those of several foreign countries. Indeed, in the matter of submarine inventions, only one country can be considered as rivaling America, that nation being France, whose enthusiasm for submarine navigation has been much greater than that of any other nation, although in the matter of results she has not outstripped the United States.
Mr. Holland's first submarine boat was built in 1875. It was called a "diving canoe," being only sixteen feet in length and wide enough to hold one man clothed in a diving-suit. Four years later, however, Holland built a larger boat called the Holland No. 3 constructed along similar lines to the most recent submarines. This was the first buoyant submarine to be steered up and down by horizontal rudders alone, and may be said to mark an epoch in submarine navigation. But the No. 3 had many defects, and Mr. Holland continued to build and improve new boats, until finally his ninth boat, which is the one familiarly known as the Holland, represented a practical form of submarine vessel. This boat was 53 feet 10 inches long, 10 feet 3 inches in diameter, had a displacement of 75 tons, and carried 10 tons of water ballast. The gasoline engine which it used when running at the surface propelled the boat at the rate of seven knots an hour, and it could travel a distance of fifteen hundred miles at this rate of speed with the amount of fuel carried. When submerged it could run a distance of about fifty knots without coming to the surface.
In diving, the Holland type of boat takes in sufficient water ballast to lower it to the surface of the water. The horizontal rudders are then brought into use causing it to descend to the desired depth, and keeping it at an approximately uniform distance from the surface while running submerged. By this arrangement the boat can dive very quickly, requiring only a matter of eight or ten seconds for reaching a depth of thirty feet. Record plunges have been made in less time than this.
The armament of the Holland boat was originally designed to consist of three tubes, two of which were for throwing aërial torpedoes and shells, and the third for discharging Whitehead torpedoes. One of these aërial guns was placed in the bow, and one in the stem; but later the stern tube was abandoned. The bow gun was designed to discharge projectiles a distance of about one mile, such projectiles weighing something over two hundred pounds and carrying one hundred pounds of gun-cotton. The tube for discharging the Whitehead torpedo was practically the same as the submerged tubes in use at present on battle-ships.
Although this Holland is now the type of diving boat most familiar to the majority of people, and the one in use in several navies, it should not be understood that the Holland boats were the only successful submarines constructed up to this time. France and Russia had produced successful diving boats; and in America those invented by Simon Lake, some of which are used for wrecking and salvage work as well as for war purposes, have proved quite as practical as the Hollands. In recent tests of these two types by the United States Government the Holland boats showed themselves to be slightly superior to the Lake boats in certain particulars, but the margin of superiority was a very narrow one.
The boats of the "Octopus" type are strictly speaking "diving boats," while the Lake boats are of the "even-keel" type. These terms refer to the method of submergence, the diving boats changing their horizontal trim when submerging, while the even-keel boats retain their horizontal trim, or nearly so.
The Lake boats have some features not usually embodied in other submarines, since some of the boats are designed for purposes other than warfare. Thus, they are equipped with wheels, or buffers, on which they can roll along the bottom of the ocean or bay. In the bow is an air-tight compartment with an opening in the bottom through which a diver can emerge and work on wreckage, or laying and disconnecting mines. These boats have also a safety device in the form of a detachable keel weighing several tons. In case of accident, when it might otherwise be impossible to rise to the surface, this keel can be detached simply by pulling a lever, thus giving the boat sufficient buoyancy to rise to the surface. This particular feature of the detachable keel is not peculiar to the Lake boats alone, some of the foreign submarines using a similar arrangement as a safeguard.
THE AMERICAN SUB-MARINE BOAT "CUTTLEFISH" IN DRY DOCK AT THE BROOKLYN NAVY YARD.
Technically speaking the name "submarine" is now used only as applying to those boats that are operated solely by electric power, have little buoyancy, and do very little running at the surface. The term "submersible" is applied to a submarine boat, actuated by electricity while submerged, but using gasoline motors for motive power while running at the surface. These gasoline engines are used at the same time for charging the storage batteries; so that the submersible is a much more practical boat than the submarine, and at the same time is quite as good a diver. Indeed, although many naval writers are very careful to make a distinction in the use of these terms, there seems little need of doing so, since only one type of boat—the submersible—is now considered practical. But as the word submarine is the older and more popular, it is used here to cover both classes except in specific cases.
For several years there were two classes of submarines under observation—those possessing no floatability when submerged, and those having some reserve buoyancy. The advantage claimed for the no-floatability class of boats is that, having no buoyancy, they are kept more easily at a certain depth below the surface of the water instead of tending to come to the surface constantly as in the case of boats of the other type.
But in actual practice the theoretical possibilities of such boats have not come up to the expectations of their advocates. For keeping the boat at a uniform depth, the most universally accepted method is by the use of horizontal rudders. The fact that the vertical direction of a boat may be controlled by horizontal rudders, when her buoyancy is small, has long since been established in submarine navigation; and the simplicity of this method naturally helps its popularity. If there were no shifting of weight in a submarine, or no wave disturbance, it would not be difficult to set the rudders at such an angle that the boat would travel for long distances at an approximately uniform submergence, the depth of submergence being indicated by gauges acted upon by the water pressure on the surface of the boat. And in actual practice it is possible to do this at the present time, part of the problem having been solved by automatic and other devices.
It should be remembered that many things enter into the disturbance of the submarine's equilibrium. The movement of a member of the crew from one point to another shifts the ballast; a certain amount of leakage of water cannot be avoided, and the sudden discharge of a torpedo weighing several hundred pounds from her bow tends to bring the boat quickly to the surface if this lost weight is not compensated for quickly. By various ingenious devices all these difficulties have been practically overcome, most of them automatically.
But the great unsolved problem of submarine navigation—practically the only one that now opposes a question mark to its great utility in warfare—is that of steering with certainty of direction when submerged. Once the submarine is under water it is in utter darkness as far as seeing to steer is concerned; and what adds to the difficulty is the fact that the compass cannot be relied upon, because of the surrounding electrical apparatus. It would be possible, perhaps, to construct a powerful electric lamp to throw a light some distance ahead of the boat, but this would defeat the primary object of submarine attack, as such a light would be seen by an enemy.
In still water, when the boat is running within a distance of ten or fifteen feet of the surface, it is possible to steer with great precision by the use of an optical tube or "periscope." This periscope is a straight, hollow tube, connected with the steering compartment in the submarine, and protruding above the water. In the upper end are a mirror and lenses so arranged that the surrounding objects are reflected downward through the tube, and show on a screen, or some other device, so that the helmsman sees things of exactly the same size that they would appear to the naked eye. The periscope is also fitted with a telescope attachment which magnifies objects like the binoculars used in surface navigation. On some recent submarines there are two periscopes, a movable one for use of the commanding officer, and one that looks straight ahead for the helmsman's use.
In still water the periscope works admirably, but it is seriously interfered with even by small waves. It is so small and inconspicuous, however, that it might enable a submarine to creep within torpedo range even in daylight, and launch the torpedo with accuracy, as was proved in 1908 when a fleet of submarines actually accomplished this feat in an experimental test.