In the March 1915 issue, Popular Mechanics witnessed the beginning of two types of warfare tech that would change militaries forever—the modern submarine and the sea mine. During the early days of World War I, Germany had already proved its ability to do serious damage beneath the waves. But as the world was still grappling with the possible scale of this escalating conflict, so too were they coming to terms with these powerful—and frightening—new weapons.
When the three British armored cruisers—Aboukir, Hogue, and Cressy—were all sunk within the space of about an hour by one German submarine, the world was given a startling demonstration of the possibilities of this type of underwater fighting craft.
In the subsequent fighting at sea these vessels have played such an important part as to give considerable justification to Admiral Sir Percy Scott’s prediction that when submarines have been fully developed they will entirely displace the great dreadnaughts that form the principal fighting strength of the navies of the present time.
Next to this first decisive blow struck by the German submarine, the most striking underwater attack up to the present stage of the war was that of the British submarine “B-11” which stole past five cordons of mines laid to block the Dardanelles, torpedoed and sunk the Turkish battleship “Messudieh,” lying at anchor at Tchanak Kalessi, and then worked its way back to safety after being under water continuously for nine hours. In December the British made a combined sea and air attack on the German naval base at Cuxhaven, which not only demonstrated the fighting qualities of the submarine but its value for scouting purposes as well.
It is now reported on good authority that the reason this attack could be carried out without disaster to the attacking party was that the mine defenses designed to protect the naval base had been thoroughly explored in advance by British submarines.
During the five years preceding the war, submarine fighting craft had been developed to a high state of efficiency. Among the new vessels, submersibles had almost entirely superseded the original type that bore the name of submarine. For understanding the character of the fighting craft that has come into such prominence it is necessary to distinguish between the two types of vessels. The original submarine was designed primarily to operate under water and was far from being a seaworthy craft when running on the surface.
These vessels were therefore valuable mainly for coast defense and for operations within restricted limits in connection with a fleet of warships. The submersible, while having all the underwater efficiency of the submarine, is built to operate on the surface as well, and is practically as seaworthy as a destroyer. Such vessels are capable of making long voyages and of taking the offensive independently and not simply as auxiliaries to a fleet of warships. All the later vessels, while commonly called submarines, are in fact submersibles. The original submarines still in service are used almost exclusively for coast defense.
A convincing demonstration of the seagoing qualities of the submersible was given a short time before the war when the French boat “Papin” made a voyage of 1,800 miles in 14 days, traveling much of the distance under water. In this voyage the “Papin” started from the French port of Cherbourg, passed around the coast of Spain, through the Strait of Gibraltar, and along the north coast of Africa to the port of Bizerta, in Tunis, completing the trip with only two landings. The “Papin” is over 170 ft. in length and carries six torpedo tubes.
The leading nations—belligerents and neutrals alike—are building bigger submersibles all the time. According to reports the Germans are building four of such size that they will be able to keep at sea for 40 days without having to replenish their stocks of oil or provisions.
So far as is definitely known, however, a submersible to be built for the United States will be the largest of all. This vessel is to be 260 ft. long and will have a radius of action of 5,500 miles. It will be capable of making a speed of 23 miles an hour on the surface and of 1,212 miles an hour when submerged. A contract for the construction of this modern “Nautilus” was awarded recently by the Navy Department—the cost being $1,350,000.
The submarine is shaped like a cigar, a cross section at any point along the hull being practically circular. In the submersible this shape is retained for the inner shell, but over this is built a hull that gives the completed vessel the shape of a torpedo boat. The inner shell contains all the working parts of the boat, while the space between the two shells is utilized for the water ballast compartments which, when filled, overcome the buoyancy of the craft and cause it to sink to any desired depth beneath the water.
The interior of a submersible impresses one as being a thing of supreme nervous energy, with every detail devoted to the accomplishment of just one thing—that of slipping in close to the enemy’s ship and sinking it with a torpedo. So completely is the vessel filled with machinery and equipment for this purpose that only very limited space can be utilized for quartering and feeding the crew.
While the newer submersibles are equipped with tubes for firing torpedoes from the stern and even from the side, the principal fighting equipment is at the bow. Here are located either two or four torpedo tubes. Unlike the guns of a battleship, these tubes must be aimed at the mark by aiming the entire vessel. Each tube is closed by a trap door that opens automatically when the torpedo is fired and closes the instant the torpedo has started on its journey of destruction. Back of the torpedo tubes is a compartment for the storage of torpedoes and in this are also sleeping quarters for the officers of the vessel. In the deck above this compartment is a hatch for taking in the torpedoes.
Next comes a compartment containing one of the two electric storage batteries which furnish power for propelling the vessel when it is under water. Back of this, at the center of the vessel, is the central operating compartment, from which every movement of the vessel is controlled. Next comes a compartment containing the second set of storage batteries, then the engine room and workshop, and finally the compartment at the stern containing the propelling and steering machinery.
The crew, which often numbers from 20 to 30 men on a submersible, is usually quartered in hammocks in the compartments containing the storage batteries.
Every naval submarine vessel has two complete power plants, one for propulsion on the surface and the other for propulsion when submerged. The main power plant of the most modern submersibles consists of Diesel engines using heavy oil, but gasoline engines and steam turbines are both used for this purpose. This plant supplies power for operation on the surface and for charging the storage batteries. One of the first things in preparing for submergence is to shut off this power plant, and from this time until the vessel again comes to the surface it runs on the power stored in the batteries.
The next step is to close all the hatches and let the water into the water-ballast compartments. The vessel then begins to settle in the water, and as the process is continued, first the deck and then the conning tower go under water. For sinking to a greater depth, diving is usually resorted to, the vessel being inclined downward at an angle by means of horizontal rudders at the stern or by sea planes at the bow.
Ordinarily the submarine is kept under the surface by the action of these devices, a portion of the buoyancy of the vessel being retained so that it will rise to the surface in case of accident and as soon as it stops. It is easily possible, however, to take all the buoyancy out of the vessel so that it will lie securely on the bottom, or will hang as if suspended at any desired depth beneath the surface. One type of submarine is designed to be sunk to any depth by means of its water-ballast compartments alone, and is even provided with wheels for running on the bottom of the sea.
Of all the equipment of submarine vessels the most important is the periscope, a simple device that serves as the eyes of the craft when it is running submerged. On the latest submersibles two of these instruments are used, one being fixed to give a view straight ahead and the other being so mounted that it can be turned to face in any direction.
Although serving such a vital part in the operation of a submarine the periscope is exceedingly simple in construction. The light enters the hood of the periscope horizontally. It then passes through a prismatic lens that deflects it downward at right angles into the vertical shaft of the periscope. At the bottom of the shaft is a second lens that again turns the rays of light to a horizontal direction. This is the simplest form of the periscope.
Usually there are additional lenses for magnifying the view. After passing ‘through the bottom lens the image is either thrown on a screen or is viewed directly through a telescope by the officer in command. The one disadvantage in the periscope is that it gives only a limited view in the one direction in which it happens to be facing.
Attempts have been made to develop a panorama periscope that uses a “fish-eye” lens and gives a view of the entire horizon, but this device has not yet been developed sufficiently to come into general use. When the submarine is submerged, only the tops of the periscopes are visible above the surface. These are difficult to see and still more difficult to hit, and this accounts for the apparent ease with which a submarine can steal up within range of a battleship and fire its torpedo without being discovered.
Although submarines and submersibles are designed for firing torpedoes, and for little else, they are not by any means the only vessels that use these deadly projectiles. Torpedo boats, cruisers, and battleships are equipped with torpedo tubes. With surface vessels the torpedo is often fired from above the water, but the result is the same in any case. The torpedo is in effect a miniature submarine that automatically takes and keeps, as soon as it enters the water, a position about 15 ft. beneath the surface, and in this position propels and steers itself unerringly toward the mark at which it is fired.
The standard torpedo of the United States Navy is 18 in. in diameter and 16 ft. long. Some of the new war vessels now building have tubes for 21-in. torpedoes, of which a number have been manufactured. A torpedo consists essentially of the war head, containing about 250 lb. of guncotton; an air tank in which compressed air for propelling and steering the torpedo is stored; a compressed air engine for propulsion; horizontal and vertical rudders, and an automatic mechanism for controlling these rudders.
The horizontal steering is controlled by a small gyroscope, while a uniform depth below the surface is maintained by hydrostatic pressure applied in an ingenious but simple manner. A pipe open to the water projects from the stern into the body of the torpedo, where it opens against a piston.
On the opposite side of this piston is a spring made to exert a pressure exactly equal to that of water at a depth of 15 ft. This piston is connected with the apparatus operating the rudders that control the vertical depth. When the depth of water is greater than 15 ft. this piston is forced inward with the result that the rudders are turned upward, and when the depth of water is less than this the spring forces the piston outward and the rudders are turned in the opposite direction.
Projecting forward from the nose of the torpedo is a plunger which is thrust into the detonating charge when the torpedo strikes. This fires the detonating charge, which in turn fires the main charge of guncotton. To prevent all danger of explosion before the torpedo is launched, the plunger is securely held away from the charge by a pin which must be removed just before the torpedo is placed in the tube. The torpedo is launched from the tube by compressed air, but the instant it enters the water it begins operations independently. So perfectly has all the controlling apparatus been worked out that it is now possible to launch a torpedo broadside from a ship and have it turn at a right angle after, entering the water and go straight ahead or straight astern.
A single torpedo costs about $8,000, and this accounts for the fact that a recent test shot fired by a United States war vessel was the second torpedo with service charge ever fired by any vessel of the United States Navy. This was done at the Newport torpedo station for the purpose of testing a new device for destroying torpedo nets. The twisted remains of the exploded torpedo were recovered and preserved for study.
In spite of the deadly menace of the submarine there is such a thing as an effective defense against it. For a ship under way, high cruising speed and frequent change of course constitute the principal defense. Added to this are rapid-fire guns and a constant lookout from the ship and from aeroplane scouts. Where the ship is accompanied by torpedo boats or destroyers, these are constantly on the alert to ram and sink a submarine the moment its periscopes are seen. One weakness of the submarine is its low speed when submerged.
For this reason such a vessel cannot give chase to a warship. It cannot make its escape by running away without coming to the surface, where it is exposed to gun fire. Its only chance for a successful attack is in lying in wait for a ship that is under way, or in stealing in close to a ship lying at anchor. The range for firing a torpedo successfully, however, is not so great as might be supposed, in comparison with the range for successful battleship action. A hit is almost certain at a range of 700 or 800 yd., while 1,500 yd. is considered a good range. Some of the submersibles now being built are designed for firing at a range of from 7,000 to 10,000 yards.
When a battleship is at anchor, defense is likely to be a much more difficult matter. Such protection as is possible is provided by mine fields, heavy-chain entanglements, and by steel torpedo nets, suspended from spars and floats around individual ships. This protection is not always effective. Both the Audacious and the Messudieh were sunk while at anchor.
In the case of the Audacious the attack occurred at the principal naval base of the British navy where there was a fleet of battleships and where there was undoubtedly a flotilla of scout boats on guard. With the latest type of torpedo even the steel netting is no longer effective as a defense. The new 21-in. torpedo that has been adopted by the United States Navy is equipped with a secondary war head that blows a hole in the strongest steel netting without setting off the main charge, and permits the torpedo to pass through. The first charge is fired by contact with the netting. This explosion lights a time fuse that explodes the main charge after a given interval of time.
Although it cannot make a definite attack on a ship, the submarine mine is perhaps the greatest menace of all to battleships and other surface vessels, and up to the present stage of the war more ships have been sunk by this means than by the submarines with their torpedoes.
Three kinds of mines are in common use, and all are so deadly in their effect that there is little hope for a ship that even brushes against any one of them. The one in most common use is the trigger mine, which is usually anchored at a depth of 15 ft. below the surface. The method of anchoring a mine of this class is shown in one of the illustrations. When the mine is in place, the trigger projects out from one side. A ship striking the trigger pushes it to one side and releases a spring-actuated plunger that explodes the detonating charge.
The mine responsible for the destruction of the cruiser Amphion is said to have been what is known as the “contact” mine. A mine of this type is globular in shape and is studded with small leaden spines. Each of these spines is in contact with a glass receptacle filled with acids and placed within the mine. When one of them is struck the glass receptacle is broken and the acids, flowing into a chamber containing chemicals, set up an action that explodes the guncotton. The electro-contact mine is suited only to harbor defense. It is exploded by the closing of an electric circuit from a station on shore, and for this reason is dangerous only to the enemy’s ships.
The electric control of this type of mine has been developed to a high degree of perfection. In the latest installations a number of mines are grouped together on one electric circuit. When one of the mines is struck an electric bulb is lighted in the shore station. Then when the operator closes the electric switch this mine, and this mine alone, is exploded.
The only way of clearing a mine field is by “creeping.” This is done by two trawlers which drag between them a sagging chain, the purpose being to explode the mines by dragging the chain against them at a safe distance.
The work is extremely dangerous. Not less than half a dozen British trawlers have already been sunk by striking the mines that they were attempting to destroy. The drifting mine with which the North Sea was said to have been studded at the beginning of the war is a contact mine of any type that floats on the surface. Such mines are arranged in pairs and connected by a floating cable so that a ship striking either of the mines or the cable is practically certain to be destroyed.
Just what the submarine strength of the warring nations was at the beginning of the war is not definitely known, but according to the best authority available, England and France each had 78 submarines and submersibles, Russia 37, Germany 21, and Austria 6. This gave the allies a total of 193, and Germany and Austria a total of 30.
By this time, however, these figures have undoubtedly undergone a great change, as all the belligerents have been and are still busily at work building more and larger submersibles.